Current IssueSpecial IssueEditorial BoardOnline First ArticlesArchive
Current IssueSpecial IssueEditorial BoardOnline First ArticlesArchive

Full Research Article

Herbicide-based Weed Management for Enhanced Cowpea (Vigna unguiculata) Performance in Ghana’s Semi-deciduous Forest Zone

A
Appiah-Kubi Samuel1
N
Novor Samuel2,*
K
Kwadwo Gyasi Santo2
K
Kwabena Atakora2
E
Esther Fobi-Donkor2
1Cocoa Health and Extension Division, Ghana Cocoa Board, Post Office Box 25, New Abirem-Eastern Region, Ghana.
2Department of Horticulture and Crop Production, University of Energy and Natural Resources, Sunyani, Post Office Box 214, Ghana.

ABSTRACT

Background: This study evaluated the effects of herbicides on weed control and cowpea (Vigna unguiculata) performance in the semi-deciduous forest agro-ecological zone of Ghana.

Methods: Field experiments were conducted at Nkwanta (Ashanti region) and Abodom (Eastern region) using a single-factor, randomized complete block design with ten treatments and three replications. Treatments included one post-emergence herbicide (Agil 100 EC) applied at 2, 4, and 6 weeks after sowing (WAS), two pre-emergence herbicides (Butachlor 50% EC and Alligator 400 EC), and hand weeding at 2, 4 and 6 WAS as the control.

Result: At Nkwanta, the tallest cowpea plants were recorded with 3.6 mL a.i/ha of Butachlor 50% EC, while at Abodom, 1.8 mL a.i/ha of Agil 100 EC produced the greatest plant height. Branching at Nkwanta was highest with Alligator 400 EC at 4 and 6 WAS, whereas Abodom showed consistent branching responses across all intervals with Agil 100 EC. The application of Alligator 400 EC at 2 WAS and higher concentrations of butachlor 50% EC improved the canopy cover in Nkwanta, while the use of Alligator 400 EC in Abodom had the highest canopy spread. In both locations, the use of Butachlor 50% EC recorded the highest flowering and podding. The highest pod length and pods per plant were observed with manual weeding at 2, 4 and 6 WAS at Nkwanta, while the use of Alligator 400 EC recorded the highest pod performance in Abodom. The findings revealed a significant difference in the efficacy of the herbicide. Butachlor 50% EC improved growth metrics at Nkwanta, and Agil 100 EC was most effective at Abodom.

INTRODUCTION

Cowpea [Vigna unguiculata (L.) Walp.] is known as a very important crop and a lifeline for many families in sub-Saharan Africa. Cowpea provides food security, essential revenue for cultivators, provide sustainable farming systems, especially in the savannah regions of West Africa (Valenzuela and Smith, 2002; Manibharathi et al., 2024). Cowpea is cultivated on approximately 12.8 million hectares of land, producing about 7.6 million tonnes each year globally, which 87% of the total production coming from Africa (Abate et al., 2012). The main African countries that produce cowpea on a large scale include Nigeria, Niger, Senegal, Ghana, Mali and Burkina Faso (Langyintuo et al., 2003; FAO, 2019). Cowpea is the second most essential legume in Ghana after groundnut (Asare et al., 2020). Cowpea is mostly cultivated in communities in the Guinea and Sudan savannah zones, serving as an important protein source and supporting the community livelihoods (Al-Hassan and Diao, 2007).
       
Cowpea contains 25% of protein, essential micronutrients and can fix atmospheric nitrogen back into the soil. This makes it an ideal crop to be included in the crop rotation system (Sichone and Mweetwa, 2018; Simunji et al., 2019). Aside from these benefits, the production of cowpea in the tropics is challenging. Aggressive weed competition largely reduces the productivity from 12.7% to over 70% (Gupta et al., 2016; Ugbe et al., 2016). Weeds compete with the cowpea crop for nutrients, light, moisture and also their ability to harbor pests and diseases, which increases production cost (Marinov-Serafimov, 2015).
       
With high labour costs and difficult manual weeding for large farms, the use of chemical weed control has become increasingly unavoidable (Manisankar et al., 2022; Nath et al., 2024; Rani et al., 2024). The application of herbicides is crucial to finding the right dose to ensure the effective control of the weed without affecting the cowpea crop performance and total yield (Nath et al., 2024; Nesha et al., 2026). Therefore, it’s very important to evaluate how specific herbicides and their application rates affect weed control and the agronomic performance within the semi-deciduous forest agro-ecological zone of Ghana.

MATERIALS AND METHODS

Experimental sites
 
Field trials were carried out in the 2023 cropping season at two separate sites, Abodom (Birim North District, Eastern Region) and Nkwanta (Mampong Municipality, Ashanti Region), Ghana. Abodom lies between latitude 6°20′18″N and longitude 0°59′44″W, elevated at 156 m above sea level, within the semi-deciduous forest zone. This trial site experience bimodal rainfall pattern, major season (March to July) and minor season (August to October). Yearly rainfall ranges from 1500 to 2000 mm, the average daily temperature is 25.2°C and the mean relative humidity is 55-59%. Soils are mainly silty sand, appropriate for cowpea production (Issaka et al., 2012; Asubonteng et al., 2001).
       
Nkwanta lies between latitude 01°45′N and longitude 1°24′W and is elevated at 402 m above sea level, positioned in the forest-savannah transitional zone. The area experiences bimodal rainfall, with yearly rainfall of 1094-1200 mm, major rains in (March to July) and minor rains in (August to November), with a daily average temperature of 30°C. Soils are well-drained, pebbly, moderately fertile, with a pH 6.0-6.5 and good water-holding capacity. Common weeds include Cyperus rotundus, Cynodon plectostachus and Panicum maximum. Nearly 80% of land is under smallholder cultivation (Tachie-Menson et al., 2021; Bolfrey-Arku et al., 2006).
 
Experimental design and treatments
 
Design
 
A single-factor experiment was laid out in a randomized complete block design (RCBD) with three replications at each site. Ten treatments were evaluated, with each replication containing ten plots of 4 m × 3 m, separated by 1 m between plots and 2 m between blocks, giving a total of 30 plots per site (529.5 m2).
 
Treatments
 
Two pre-emergence herbicides (Butachlor 50 EC and Alligator 400 EC) were applied at three rates each and one post-emergence herbicide (Agill 100 EC) at three rates, along with a manual weeding control (2, 4, 6 WAS). The treatments were:
• T1: Butachlor 50 EC, 1.8 ml a.i./ha.
•  T2: Butachlor 50 EC, 3.15 ml a.i./ha.
•  T3: Butachlor 50 EC, 3.6 ml a.i./ha.
•  T4: Alligator 400 EC, 1.62 ml a.i./ha.
•  T5: Alligator 400 EC, 1.98 ml a.i./ha.
• T6: Alligator 400 EC, 2.16 ml a.i./ha.
• T7: Agill 100 EC, 1.08 ml a.i./ha at 2, 4, 6 WAS.
• T8: Agill 100 EC, 1.44 ml a.i./ha at 2, 4, 6 WAS.
• T9: Agill 100 EC, 1.8 ml a.i./ha at 2, 4, 6 WAS.
• T10: Manual weeding at 2, 4, 6 WAS.
 
Planting material
 
Cowpea variety ‘Zamzam’ was obtained from the Crop Research Institute, CSIR, Fumesua, Kumasi, Ashanti Region, Ghana.
 
Land preparation and sowing
 
Field preparation involved clearing with cutlasses and leveling with hand hoes. Planting at Abodom was on 20 May 2023 and at Nkwanta on 17 June 2023. Each plot had five rows, 0.6 m between rows, 0.2 m within rows, with one seed per hole at 4 cm depth, totaling 100 seeds per plot. No fertilizers were applied. Tools included meter rules and tapes (layout and growth measurements), pegs and tags (identification), knapsack sprayers (herbicide application) and electronic scales (grain measurement).
 
Soil physiochemical properties of the experimental sites
 
The two experimental sites differed considerably in soil physicochemical properties (Table 1). Abodom recorded higher organic carbon, organic matter, total nitrogen, and ECEC (1.48%, 2.95%, 0.16%, and 12.54 mol/kg) compared to Nkwanta (0.32%, 0.64%, 0.04%, and 3.02 mol/kg), indicating greater inherent fertility. Both sites were slightly acidic (pH 5.69 and 5.65), though Abodom’s silty loam texture contrasted sharply with Nkwanta’s sandy soil, likely influencing water retention, nutrient availability, and the differential herbicide and cowpea growth responses observed across locations.

Table 1: Preliminary chemical and physical characteristics of soil at the study sites at 0-15 cm.


 
Cultural practices
 
Manual weed control
 
Weeds were controlled by cutlass and hand-picking at 14-day intervals. Predominant weeds were Cyperus spp.
 
Chemical weed control
 
Pre-emergence herbicides were applied before sowing and post-emergence herbicides were applied at 2, 4 and 6 WAS, according to treatment rates.
 
Pest and disease management
 
Insect pests were controlled using emetine benzote (1.5 L/ha) and Karate 2.5 EC (50 ml per knapsack, 20 knapsacks/ha). Fungal diseases were monitored and controlled with Redomil at 1.5 kg/ha. Regular scouting was employed to detect early infections.
 
Data collection
 
Seedling emergence
 
Emergence counts were conducted within two weeks of sowing and the percentage emergence was calculated.
 
Growth parameters
 
Plant height, number of branches and canopy spread were measured on five tagged plants per plot at 2, 4 and 6 WAP using meter rules and tapes.
 
Phenological traits
 
Days to 50% flowering and podding were recorded visually.
 
Yield components
 
At harvest, the number of plants, pods per plant, pod length, seeds per pod, thousand-grain weight and net grain yield were determined from the net plot. Pods were sun-dried before measurements and seed weights were obtained using electronic scales.

Statistical analysis
 
Data were subjected to ANOVA and treatment means were separated using least significant difference (LSD) at 5% probability level. Assumptions of normality and homogeneity of variance were checked before analysis.

RESULTS AND DISCUSSION

Effect of herbicide on growth parameters of cowpea
 
Plant height (cm)
 
At 14 days after sowing (DAS), herbicide application did not significantly influence cowpea plant height at Nkwanta (p = 0.377). The highest plant height was observed under 3.6 mL a.i./ha of Butachlor 50% EC, while the lowest occurred with 1.44 mL a.i./ha of Agil 100 EC. In contrast, plant height at Abodom differed significantly among treatments at the same growth stage (p<0.05), with 1.8 mL a.i./ha of Agil 100 EC producing the tallest plants and 3.6 mL a.i./ha of Butachlor 50% EC the shortest, excluding the control (Table 2).

Table 2: Effect of different rates of herbicides on cowpea plant height (cm).


       
At 28 DAS, no significant variation in plant height was recorded among treatments at Nkwanta (p=0.524). Here, 3.6 mL a.i./ha of Butachlor 50% EC resulted in the greatest height, while 3.15 mL a.i./ha of the same herbicide gave the lowest. However, a highly significant treatment effect was observed at Abodom (p<0.0003), where 1.8 mL a.i./ha of Agil 100 EC produced the maximum plant height and 3.6 mL a.i./ha of Butachlor 50% EC the minimum.
       
By 42 DAS, plant height at Nkwanta differed significantly among herbicide treatments (p<0.011), with the tallest plants recorded under 3.6 mL a.i./ha of Butachlor 50% EC and the shortest under 1.62 mL a.i./ha of Alligator 400 EC. Similarly, a significant treatment effect was observed at Abodom (p = 9.28E), where 1.8 mL a.i./ha of Agil 100 EC consistently produced the greatest plant height, while 3.6 mL a.i./ha of Butachlor 50% EC resulted in the least (Table 2).
 
Number of branches
 
Herbicide active ingredient rates had no statistically significant effect on cowpea branching at 14, 28, or 42 DAS at Nkwanta (p>0.05) and a comparable lack of significance was observed at Abodom across all assessment periods (Table 3). Despite the absence of significant differences, treatment-related numerical trends were evident. At 14 DAS in Nkwanta, the weeded control recorded the highest branch number, while the lowest values occurred under 1.8 and 3.15 mL a.i./ha of Butachlor 50% EC. Conversely, at Abodom, 1.44 mL a.i./ha of Agil 100 EC produced the highest branch count, whereas the weeded control recorded the lowest. By 28 DAS, branching at Nkwanta peaked under 1.62 mL a.i./ha of Alligator 400 EC and declined most under 3.6 mL a.i./ha of Butachlor 50% EC. At Abodom, the highest and lowest values were associated with 1.8 mL a.i./ha of Agil 100 EC and 1.62 mL a.i./ha of Alligator 400 EC, respectively. At 42 DAS, the highest branch number at Nkwanta occurred under 2.16 mL a.i./ha of Alligator 400 EC, with the lowest recorded at 3.6 mL a.i./ha of the same herbicide. In Abodom, 1.44 mL a.i./ha of Agil 100 EC resulted in the highest branching, while 1.98 mL a.i./ha of Alligator 400 EC produced the lowest (Table 3).

Table 3: Number of branches of cowpea under different herbicide treatments.


 
Canopy spread (cm)
 
Canopy spread of cowpea at Nkwanta was not significantly influenced by herbicide active ingredient concentration at any sampling time (14, 28, or 42 DAS; p>0.05). In contrast, significant treatment effects were observed at Abodom across all measurement periods (p<0.05). At 14 and 28 DAS, plots treated with 1.8 mL a.i./ha of Agil 100 EC (applied at 2, 4 and 6 WAS) recorded the greatest canopy spread and differed significantly from those treated with 3.6 mL a.i./ha of Butachlor 50% EC. By 42 DAS, the widest canopy was associated with 2.16 mL a.i./ha of Alligator 400 EC, which was significantly higher than values obtained under butachlor 50% EC (3.6 mL a.i./ha), Agil 100 EC (1.8 mL a.i./ha) and the manually weeded control (Table 4).

Table 4: Canopy spread (cm) of cowpea under different herbicide treatments.


 
Days to 50% flowering
 
The days to 50% flowering of cowpea further showed significant differences (p<0.0002) among the various herbicide active ingredient concentrations for the days to 50% flowering in Nkwanta with 3.6 mL a.i/ha of Butachlor 50% EC had recorded the maximum and 2.16 mL a.i/ha of Alligator 400 EC had recorded the minimum whiles there was no significant difference (p = 0.4176) among the various herbicide active ingredient concentrations for the days to 50% flowering in Abodom at the rate of 3.15 mL a.i/ha of Butachlor 50% EC had recorded the maximum and weeding at (2, 4 and 6 WAS) as control had recorded the minimum (Table 5).

Table 5: Days to 50% flowering of cowpea.


 
Days to 50% podding
 
The results from (Table 6) for the days to 50% podding of cowpea indicated significant differences (p<1.77E-06) among the various concentrations of herbicide active ingredient in Abodom with the rate of 1.8 mL a.i/ha of Butachlor 50% EC had recorded the maximum and weeding at (2, 4 and 6 WAS) as control had recorded the minimum whiles there were no significant differences (p>0.2004) for the days to 50% podding of cowpea in Nkwanta with the rate of 3.6 mL a.i/ha of Butachlor 50% EC had recorded the maximum and 1.08 mL a.i/ha of Agil 100 EC (2, 4 and 6 WAS) had recorded the minimum.

Table 6: Days to 50% podding of cowpea.


 
Yield and yield-related parameters
 
Effect of herbicide application on cowpea yield and yield components
 
At Nkwanta, cowpea yield and its associated components were not significantly influenced (p>0.05) by the different herbicide active ingredient rates applied. Pod length, number of pods per plant, seeds per pod, thousand-seed weight and grain yield remained statistically comparable across treatments. Nonetheless, numerical variations were observed. The longest pods occurred under the weeding treatment, whereas the shortest pods were recorded at 3.15 mL a.i./ha of Butachlor 50% EC. The highest number of pods per plant was obtained at 1.08 mL a.i./ha of Agil 100 EC, while the lowest was observed at 3.6 mL a.i./ha of Butachlor 50% EC. Seeds per pod peaked at 1.8 mL a.i./ha of Butachlor 50% EC and declined at 3.15 mL a.i./ha of the same herbicide. Thousand-seed weight was greatest at 3.15 mL a.i./ha of Butachlor 50% EC and lowest at 1.44 mL a.i./ha of Agil 100 EC. Grain yield was numerically highest at 1.62 mL a.i./ha of Alligator 400 EC and lowest at 3.6 mL a.i./ha of Butachlor 50% EC (Table 7).

Table 7: Effect of herbicides on cowpea yield and yield parameters.


       
In contrast, at Abodom, herbicide treatments significantly affected pod length and grain yield. Pod length was highest under the weeding treatment and lowest at 3.6 mL a.i./ha of Butachlor 50% EC. Grain yield reached its maximum at 1.62 mL a.i./ha of Alligator 400 EC and 1.8 mL a.i./ha of Agil 100 EC. However, pods per plant, seeds per pod and thousand-seed weight did not differ significantly among treatments. Despite this, the highest number of pods per plant was observed at 1.62 mL a.i./ha of Alligator 400 EC, while the lowest occurred at 1.8 mL a.i./ha of Agil 100 EC. Seeds per pod were highest at 2.16 mL a.i./ha of Alligator 400 EC, with the lowest values recorded at 1.8 and 3.6 mL a.i./ha of butachlor 50% EC (Table 7).
 
Effects of herbicide regimes on vegetative growth
 
Plant height
 
Cowpea height showed a strong site × herbicide interaction, revealing itself in radically different responses at Nkwanta and Abodom. At Nkwanta, variation in herbicide rate did not affect the early vegetative development, with differences that are statistically significant appearing only at later stages of growth. On the other hand, cowpea maintained at Abodom recorded vigorous and sustained response to treatment during the entire period of growth, implying that plant growth at this site was more sensitive to weed management practices under prevailing environmental conditions.
       
These different reactions match up with the ways the herbicides work and how picky they are. Butachlor is a pre-emergence chloroacetanilide that mostly keeps sprouting weeds in check, but can put some pressure on the crop when used at higher doses. Pendimethalin (Alligator 400 EC) also interferes with the growth of roots and shoots of weeds at the initial stage of their emergence. In contrast, Agil 100 EC (propaquizafop), a selective post-emergence herbicide for the control of grasses, is safe to broadleaved crops such as cowpea. This, therefore, means that the superior plant height recorded under the Agil treatments at Abodom could be attributed to adequate post-emergence grass control, which reduced competition for light, water and nutrients under high weed pressure conditions. A similar trend has, however, been reported across all agroecological conditions. Cruz et al., (2020) noted that the integrated herbicide program, which controlled grasses, resulted in greater height of cowpea, while Yadav et al., (2017) noted better vegetative growth from the application of pendimethalin, supported by subsequent control of weeds. Selective herbicides and hoe weeding have also been found to increase the height of cowpea as compared to unweeded plots by Kumar et al., (2025), though responses were seasonal. Such a relatively lower response at Nkwanta can be attributed to site limitations comprising lower rainfall, higher temperatures and well-drained pebbly soils that reduce weed competition, plus less dynamic benefit from capture resources facilitated by herbicide intervention (Guuroh et al., 2025). This interpretation is an inspiration from Kusi et al., (2025), who found strong genotype × environment interaction effects on growth performance across locations in Ghana.
 
Branching
 
Branching exhibited very low sensitivity to the herbicide treatments at both locations, with only slight numerical differences among regimes. This clearly shows that in the Zamzam cowpea variety, branching is relatively less responsive to moderate contrasts of weed management compared to such attributes as plant height or canopy expansion and more so, largely dependent on inherent genetic controls and general resource status (Ibrahim, 2013; Wang et al., 2006).
       
These results fall in line with earlier reports that stated, when interference from weeds is properly controlled, differences in weed control strategies have a negligible effect on branch and leaf production (Ali et al., 2015; Felix et al., 2019). Works of literature available further go ahead to note that the flexibility of branching in cowpea is prompted by plant population density and nutrient availability rather than minor variations among equally effective options for weed management (Satodiya et al., 2015; Helmy et al., 2015).
 
Canopy spread
 
Responses in canopy spread varied markedly between sites. At Nkwanta, canopy development was largely unaffected by the herbicide regimes, while at Abodom, distinct and consistent treatment effects were evident throughout the crop growth cycle. Notably, applications of Agil 100 EC and the higher doses of Alligator 400 EC repeatedly resulted in broader canopy expansion, whereas increased rates of Butachlor were linked to comparatively restricted canopy growth. It demonstrates the importance of effective grass weed control in places like Abodom, where conditions favor the quick establishment of weeds. Propaquizafop-based herbicides selectively control grassy weeds, allowing for encouraging canopy closure, which will later suppress other secondary weeds by their shading effect (Attri et al., 2022; Bhullar et al., 2015). Better canopy spread improves light capture and radiation use efficiency supports more biomass production. Results that were comparable have been recorded from the cowpea production systems where all pre-emergence herbicides were based on pendimethalin and the timeliness of supplementary control measures enhanced canopy development more than when applied singly or with late hand-weeding (Nath et al., 2024). It was due to different environmental and soil characteristics. Rainfall was somewhat better at Abodom, with silty sandy soils probably encouraging more vigorous competition from weeds, thus increasing the importance of early chemical input for maximum canopy expansion (Dieleman et al., 2000; Anorvey et al., 2018). There is a relatively drier transitional climate at Nkwanta, accompanied by a different species composition of weeds-herbs may not be so competitive here; hence, less apparent influence of herbicide treatment on canopy development (Anorvey et al., 2018).
 
Phenological responses: Flowering and podding
 
The herbicide treatments induced generally slight and location-specific effects on cowpea phenological development. Flowering time varied slightly between treatments at Nkwanta, with higher rates of Butachlor application delaying the onset of flowering, most likely due to initial herbicide stress or changes in early crop-weed dynamics. This, therefore, indicated a strong phenological plasticity under specific environmental conditions prevailing at the site since flowering at Abodom was not responsive to the applied herbicide regimes (Quee et al., 2021). Patterns seen for podding further emphasize the role of local factors in guiding herbicide effects. Podding time at Nkwanta stayed mostly the same among treatments, while clear differences showed at Abodom. Some Butachlor uses delayed pod start when compared to manual weeding. Delays might be associated with slower crop recovery or short-term effects of herbicides under high humidity conditions with high weed pressure. Such trends corroborate earlier studies that asserted that pre-emergence herbicides, especially when applied at higher rates, may instigate minor delays in the development of crops (Quee et al., 2021; Ezebuiro et al., 2021). Normally, these shifts are limited and do not necessarily result in yield penalties (Cruz et al., 2020; Arshad et al., 2025). In a related situation, found that hoe weeding usually encourages an earlier start of flowering and pod formation compared to chemical control of weeds (Dennis et al., 2024).
       
Overall, the mild and localized phenological reactions observed in the current experiment confirm the high tolerance of the Zamzam cowpea variety. But under agro-ecosystems which are characterized by a short growing period or high risk of terminal drought, even small delays in developmental stages might be agronomically meaningful and warrant more detailed analysis (Quee et al., 2021).
 
Effects on yield and yield components
 
Grain yield and its contributing characters were highly site-specific and treatment effects were more pronounced at Abodom than at Nkwanta. No significant differences in any yield component or overall grain yield were observed at Nkwanta, suggesting that the effectiveness of the weed control treatments evaluated was similar at this site.
       
In contrast, the effects of treatments at Abodom were highly significant, especially for pod length and grain yield. Alligator 400 EC and Agil 100 EC at intermediate application rates contributed to maximum grain yields, while higher rates of Butachlor were associated with lesser performance. The lack of consistent differences among individual yield components indicated that the yield responses observed resulted mainly from a general improvement in plant growth and vigor rather than from isolated reproductive attributes (Ebone et al., 2020; Dias et al., 2011).
       
The results line up with earlier studies showing that Butachlor’s effectiveness really depends on how much you use and what the environment’s like. Just dumping more doesn’t always mean you’ll get better yields (Chongdar et al., 2016). Other research from West Africa and South Asia found that cowpea yields improved with pendimethalin-based pre-emergence herbicides, especially when farmers combined them with good agronomic practices (Ibrahim, 2013). In this study, moderate doses of Alligator 400 EC kept yield numbers high, while hand weeding made pods longer but didn’t always boost the grain yield. That fits with what Dennis et al. (2024) found, which showed that carefully managed herbicide use can match or even beat hand weeding, plus it saves a lot of labor.

CONCLUSION

This study shows that chemical weed control really shapes how cowpea plants grow, develop and yield, but the results depend a lot on which herbicide you use, how much you apply and the local environment. At the Nkwanta site, spraying Butachlor 50% EC before the plants emerged (at 3.6 mL a.i./ha) led to strong, tall plants. But at Abodom, the best plant height and canopy came from using Agil 100 EC (1.8 mL a.i./ha) after the plants were up. No matter the treatment or location, branching didn’t respond much to the herbicides, which indicates that genetics drives this trait more than weed management practices.
       
Grain yield and yield components played out differently depending on the site. In Nkwanta, changing the type or amount of herbicide barely touched the yield, so performance stayed steady across treatments. But in Abodom, yields improved when Alligator 400 EC at 1.62 mL a.i./ha or Agil 100 EC at 1.8 mL a.i./ha were applied. Clearly, knocking back grass weeds matters more in spots with heavier weed pressure. Increasing herbicide doses higher, especially with Butachlor, didn’t boost yields much and sometimes even slowed down the plants’ move into reproductive stages.
       
Altogether, the results showed that using moderate amounts of herbicide works better than going heavy and post-emergence, grass-targeting sprays really help when weeds are thick. The big influence of location on how treatments work just shows that blanket herbicide advice doesn’t cut it; farmers need weed control plans that fit their specific fields. Further research such as how long herbicide residues stick around, the best timing for applications and how different cowpea varieties react to these chemicals. Results will help build more sustainable and productive cowpea farming systems.

ACKNOWLEDGEMENT

I gratefully acknowledge the cooperation of the Abodom farming community, with particular appreciation to Mr. Oteng Kofi, the Chief Farmer, for his invaluable support and assistance throughout and beyond the fieldwork period. I also extend sincere thanks to Amuzu Godwin, Mr. Adebah Ebenezer and Mr. Senaye Raphael of the New Abirem Cocoa Health and Extension Division for their encouragement, as well as their constructive comments and technical input.

CONFLICT OF INTEREST

All authors declare that they have no conflict of interest.

REFERENCES


  1. Asare, A.T., Mensah, T.A., Tagoe, S.M.A. and Asante, D.K.A. (2020). Identification of new sources of rust resistance in cowpea [Vigna Unguiculata (L.) Walp] germplasm using simple sequence repeat markers. Legume Research. 43(2): 185-189. doi: 10.18805/LR-488.

  2. Abate, T., Alene, A.D., Bergvinson, D., Shiferaw, B., Silim, S., Orr, A. and Asfaw, S. (2012). Tropical Grain Legumes in Africa and South Asia: Knowledge and Opportunities. PO Box 39063, Nairobi, Kenya: International Crops Research Institute for the SemiArid Tropics. 112 pp. ISBN: 978-92-9066-544-1. Order Code: BOE 056.

  3. Al-Hassan, R.M. and Diao, X.  (2007). Regional Disparities in Ghana: Policy Options and Public Investment Implications. IFPRI Discussion Papers 693, International Food Policy Research Institute (IFPRI).

  4. Ali, A., Streibig, J.C., Christensen, S. and Andreasen, C. (2015). Image based thresholds for weeds in maize fields. Weed Research. 55(1): 26-33.

  5. Anorvey, V., Asiedu, E. and Dapaah, H. (2018). Growth and yield of maize as influenced by using Lumax 537.5 SE for weed control in the transitional agro-ecological zone of Ghana. International Journal of Plant and Soil Science. 21(2): 1-11.

  6. Arshad, M.A., Abbas, R.N., Khaliq, A. and Ahmed, Z. (2025). Ecological approaches to sustainable soybean production with sequential herbicide applications and their impact on weed dynamics and crop yield. Journal of Ecological Engineering. 26(2): 231-257.

  7. Asubonteng, K.O. and Andah, E.I. (2001). Characterization and evaluation of inland valley watersheds for sustainable agricultural production: Case study of semi-deciduous forest zone in the Ashanti Region of Ghana. Tropics. 10(4): 539-553.

  8. Attri, M., Sagar, L., Sharma, J., Nesar, N.A., Bhochalaya, R.S. and Sandhu, R. (2022). Weed management in vegetables and flower crops in India. The Pharma Innovation Journal. pp 652-661.

  9. Bhullar, M.S., Kaur, T., Kaur, S. and Yadav, R. (2015). Weed management in vegetable and flower crop-based systems. Indian Journal of Weed Science. 47(3): 267-276.

  10. Bolfrey-Arku, G.E.K., Onokpise, O.U., Carson, A.G., Shilling, D.G. and Coultas, C.C. (2006). The speargrass [Imperata cylindrica (L.) Beauv.] menace in Ghana: Incidence, farmer perceptions and control practices in the forest and forest-savanna transition agro-ecological zones of Ghana. West African Journal of Applied Ecology. 10(1). https://doi.org/10.4314/wajae.v10i1.45713.

  11. Chongdar, S., Rai, A., Ghosh, A., Patra, K. and Kanti, P. (2016). Bioassay techniques for dose determination of non- traditional herbicides in cowpea [Vigna unguiculata (L.) Walp.]. International Journal of Current Research and Academic Review. 4(3): 178-182.

  12. Cruz, A.B.D.S., Albuquerque, J.D.A.A.D., Rocha, P.R.R., Souza, L.T.D., Cruz, D.L.D.S., Soares, M.B.B. and Silva, E.S.D. (2020). Effect of the use of pre-and post-emergence herbicides on nodulation and production of cowpea (Vigna unguiculata L.) in the Amazonian savannah. Agronomía Colombiana. 38(2): 280-286.

  13. Davis, A.S., Maxwell, B., Clements, D.R., Swanton, C.J., Valente, T., Dille, A. and Bohan, D.A. (2017). Integrated Weed Management for Sustainable Agriculture (Vol. 42). Burleigh Dodds Science Publishing.

  14. Dennis, A.O., Santo, K.G., Khalid, A.A., Atakora, K., Ntiamoah, D.A., Abdulai, M. and Eric, A. (2024). Growth, yield and grain quality of cowpea [Vigna unguiculata (L.) Walp.] and weed flora as affected by physical and chemical methods of weed control. Legume Science. 6(4): e70010.

  15. Dias, M.A.N., Pinto, T.L.F., Mondo, V.H.V., Cicero, S.M. and Pedrini, L.G. (2011). Direct effects of soybean seed vigor on weed competition. Revista Brasileira de Sementes. 33: 346-351.

  16. Dieleman, J.A., Mortensen, D.A., Buhler, D.D., Cambardella, C.A. and Moorman, T.B. (2000). Identifying associations among site properties and weed species abundance I: Multivariate analysis. Weed Science. 48(5): 567-575.

  17. Ebone, L.A., Caverzan, A., Tagliari, A., Chiomento, J.L.T., Silveira, D.C. and Chavarria, G. (2020). Soybean seed vigor: Uniformity and growth as key factors to improve yield. Agronomy. 10(4): 545.

  18. Ezebuiro, P., Yakubu, A.I. and Audu, M. (2021). Evaluation of three pre-emergence herbicides for weed control in soybean [Glycine max (L.) Merr.] in Dutsinma and Sokoto, Sudan savanna. FUDMA Journal of Sciences. 5(4): 368-374.

  19. FAO. (2019). FAO Statistics. Food and Agriculture Organization of the United Nations.

  20. Felix, F., Bonsiysi, B.I., Venasius, W.L., Christina, N.K., Nkongho, E.C., Annih, M.G. and Woin, N. (2019). Growth and yield response of maize (Zea mays L.) to different weed control methods in the western highlands of Cameroon. Journal of Agriculture and Crops. 5(2): 15-22.

  21. Gupta, K.C., Gupta, A.K. and Rani, S. (2016). Weed management in cowpea [Vigna unguiculata (L.) Walp.] under rainfed conditions. International Journal of Agricultural Sciences. 12(2): 238-240. https://doi.org/10.15740/HAS/IJAS/12.2/ 238-240.

  22. Guuroh, R.T., Nero, B.F., Folega, F., Oduro, K.A., Kalanzi, F., Adeyiga, G.K. and Amponsah, E. (2025). Woody and herbaceous species diversity respond differently to environmental variables in semiarid areas in Ghana. Ecology and Evolution. 15(4): e71253.

  23. Helmy, A.A., Hassan, H.H. and Ibrahimet, H. (2015). Influence of planting density and bio-nitrogen fertilization on productivity of cowpea. American-Eurasian Journal of Agricultural and Environmental Sciences. 15(10): 1953-1961.

  24. Ibrahim, U. (2013). Effect of pre-emergence herbicides on weed control and performance of cowpea. Journal of Agricultural Sciences. 8(2): 76-81.

  25. Issaka, R.N., Buri, M.M., Tobita, S., Nakamura, S. and Owusu- Adjei, E. (2012). Indigenous Fertilizing Materials to Enhance Soil Productivity in Ghana. In Soil Fertility Improvement and Integrated Nutrient Management-A Global Perspective. (pp. 119-134).

  26. Kumar, J.S., Sunitha, S., Saravanan, R., Thangamani, C., Suresh, V., Mamatha, K. and Kour, M. (2025). Sustainable approaches for weed management in taro cultivation: Analysis using mixed effect model in diverse agroclimatic conditions. Weed Research. 65(3): e70026.

  27. Kusi, F., Amoah, R.A., Attamah, P., Alhassan, S., Yahaya, D., Awuku, J.F. and Asante, I. (2025). Genotype × environment interaction effect on grain yield of cowpea [Vigna unguiculata (L.) Walp.] in deciduous forest and Sudan savanna ecologies of Ghana. Plos One. 20(1): e0314464.

  28. Langyintuo, A.S., Lowenberg-DeBoer, J. and Faye, M. (2003). Cowpea supply and demand in West and Central Africa. Field Crops Research. 82(2-3): 215-231.

  29. Manibharathi, S., Swaminathan, C., Somasundaram, S., Kathirvelan, P. and Kannan, P. (2024). Weed management practices in cowpea (Vigna unguiculata L.): A review. Legume Research. 47(12): 2019-2027. doi: 10.18805/LR-5306.

  30. Manisankar, G., Ghosh, P., Malik, G.C. and Banerjee, M. (2022). Recent trends in chemical weed management: A review. The Pharma Innovation Journal. 11(4): 745-753.

  31. Marinov-Serafimov, P. (2015). Determination of allelopathic effect of some invasive weed species on germination and initial development of grain legume crops. Pesticides and Phytomedicine. 25(3): 251-259. https://doi.org/10.2298/ PIF1003251M.

  32. Nesha, M., Dutta, D. and Krishna, V.J. (2026). Assessing the impact of quinchlorac 35% SC on weed flora, soil nutrient and microbial status in transplanted boro rice (Oryza sativa L.). Indian Journal of Agricultural Research. 60(6): 861- 868. doi: 10.18805/IJARe.A-6472.

  33. Nath, C.P., Singh, R.G., Choudhary, V.K., Datta, D., Nandan, R. and Singh, S.S. (2024). Challenges and alternatives of herbicide-based weed management. Agronomy. 14(1): 126. https://doi.org/10.3390/agronomy14010126.

  34. Olorunmaiye, K.S. (2010). Reproductive performance of two cowpea [Vigna unguiculata (L.) Walp.] varieties, Ife Brown and TVX3236, as influenced by imidazolinone and dinitroaniline herbicides. Australian Journal of Agricultural Engineering. 1(3): 101-105.

  35. Quee, D.D., Kamanda, P.J., Saffa, M.D. and Norman, J.E. (2021). Differential responses of two cowpea [Vigna unguiculata (L.) Walp.] genotypes to pre-emergence herbicides in the savannah woodland and rainforest agroclimatic regions of Sierra Leone. World Journal of Advanced Research and Reviews. 10(1): 343-355.

  36. Rani, B.S., Chandrika, V., Reddy, G.P., Nagamadhuri, K.V., Sudhakar, P. and Sagar, G.K. (2024). Response of weed management practices on yield loss, soil enzyme activity and microbial populations in maize (Zea mays L.). Indian Journal of Agricultural Research. 58(3): 474-479. doi: 10.18805/IJARe.A-6068.

  37. Satodiya, B.N., Patel, H.C. and Soni, N.V. (2015). Effect of planting density and integrated nutrient management on flowering, growth and yield of vegetable cowpea [Vigna unguiculata (L.) Walp]. Asian J. Hort. 10(2): 232-236.

  38. Sichone, R. and Mweetwa, A.M. (2018). Soil nutrient status and cowpea biological nitrogen fixation in a maize-cowpea rotation under conservation farming. Journal of Agricultural Science. 10(6): 136.

  39. Simunji, S., Munyinda, K.L., Lungu, O.I., Mweetwa, A.M. and Phiri, E. (2019). Evaluation of cowpea [Vigna unguiculata (L.) Walp.] genotypes for biological nitrogen fixation in maize- cowpea crop rotation. Sustainable Agriculture Research. 8(1): 82-93.

  40. Tachie-Menson, J.W., Buah, J.N., Adu, M.O. and Afutu, E. (2021). Morphological diversity in purple nutsedge from four agro-ecological zones in Ghana. Heliyon. 7(7): e07661.

  41. Ugbe, L.A., Ndaeyo, N.U. and Enyong, J.F. (2016). Efficacy of selected herbicides on weed control, cowpea [Vigna unguiculata (L.) Walp.] performance and economic returns in Akamkpa, southeastern Nigeria. International Journal of Agriculture. 19: 19-27.

  42. Valenzuela, H. and Smith, J. (2002). Cowpea. Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawai‘i at Mânoa.

  43. Wang, G., McGiffen, J. M.E., Ehlers, J.D. and Marchi, E.C. (2006). Competitive ability of cowpea genotypes with different growth habits. Weed Science. 54(4): 775-782.

  44. Yadav, T., Nisha, K.C., Chopra, N.K., Yadav, M.R., Kumar, R., Rathore, D.K. and Singh, M. (2017). Weed management in cowpea: A review. International Journal of Current Microbiology and Applied Sciences. 6(2): 1373-1385.
Published In
Indian Journal of Agricultural Research
Article Metrics
Metrics Icon
27
Views
0
Citations
Reviewed By
Share Article
Download Article
In this Article
    Contact us
    Follow us

    Full Research Article

    Herbicide-based Weed Management for Enhanced Cowpea (Vigna unguiculata) Performance in Ghana’s Semi-deciduous Forest Zone

    A
    Appiah-Kubi Samuel1
    N
    Novor Samuel2,*
    K
    Kwadwo Gyasi Santo2
    K
    Kwabena Atakora2
    E
    Esther Fobi-Donkor2
    1Cocoa Health and Extension Division, Ghana Cocoa Board, Post Office Box 25, New Abirem-Eastern Region, Ghana.
    2Department of Horticulture and Crop Production, University of Energy and Natural Resources, Sunyani, Post Office Box 214, Ghana.

    ABSTRACT

    Background: This study evaluated the effects of herbicides on weed control and cowpea (Vigna unguiculata) performance in the semi-deciduous forest agro-ecological zone of Ghana.

    Methods: Field experiments were conducted at Nkwanta (Ashanti region) and Abodom (Eastern region) using a single-factor, randomized complete block design with ten treatments and three replications. Treatments included one post-emergence herbicide (Agil 100 EC) applied at 2, 4, and 6 weeks after sowing (WAS), two pre-emergence herbicides (Butachlor 50% EC and Alligator 400 EC), and hand weeding at 2, 4 and 6 WAS as the control.

    Result: At Nkwanta, the tallest cowpea plants were recorded with 3.6 mL a.i/ha of Butachlor 50% EC, while at Abodom, 1.8 mL a.i/ha of Agil 100 EC produced the greatest plant height. Branching at Nkwanta was highest with Alligator 400 EC at 4 and 6 WAS, whereas Abodom showed consistent branching responses across all intervals with Agil 100 EC. The application of Alligator 400 EC at 2 WAS and higher concentrations of butachlor 50% EC improved the canopy cover in Nkwanta, while the use of Alligator 400 EC in Abodom had the highest canopy spread. In both locations, the use of Butachlor 50% EC recorded the highest flowering and podding. The highest pod length and pods per plant were observed with manual weeding at 2, 4 and 6 WAS at Nkwanta, while the use of Alligator 400 EC recorded the highest pod performance in Abodom. The findings revealed a significant difference in the efficacy of the herbicide. Butachlor 50% EC improved growth metrics at Nkwanta, and Agil 100 EC was most effective at Abodom.

    INTRODUCTION

    Cowpea [Vigna unguiculata (L.) Walp.] is known as a very important crop and a lifeline for many families in sub-Saharan Africa. Cowpea provides food security, essential revenue for cultivators, provide sustainable farming systems, especially in the savannah regions of West Africa (Valenzuela and Smith, 2002; Manibharathi et al., 2024). Cowpea is cultivated on approximately 12.8 million hectares of land, producing about 7.6 million tonnes each year globally, which 87% of the total production coming from Africa (Abate et al., 2012). The main African countries that produce cowpea on a large scale include Nigeria, Niger, Senegal, Ghana, Mali and Burkina Faso (Langyintuo et al., 2003; FAO, 2019). Cowpea is the second most essential legume in Ghana after groundnut (Asare et al., 2020). Cowpea is mostly cultivated in communities in the Guinea and Sudan savannah zones, serving as an important protein source and supporting the community livelihoods (Al-Hassan and Diao, 2007).
           
    Cowpea contains 25% of protein, essential micronutrients and can fix atmospheric nitrogen back into the soil. This makes it an ideal crop to be included in the crop rotation system (Sichone and Mweetwa, 2018; Simunji et al., 2019). Aside from these benefits, the production of cowpea in the tropics is challenging. Aggressive weed competition largely reduces the productivity from 12.7% to over 70% (Gupta et al., 2016; Ugbe et al., 2016). Weeds compete with the cowpea crop for nutrients, light, moisture and also their ability to harbor pests and diseases, which increases production cost (Marinov-Serafimov, 2015).
           
    With high labour costs and difficult manual weeding for large farms, the use of chemical weed control has become increasingly unavoidable (Manisankar et al., 2022; Nath et al., 2024; Rani et al., 2024). The application of herbicides is crucial to finding the right dose to ensure the effective control of the weed without affecting the cowpea crop performance and total yield (Nath et al., 2024; Nesha et al., 2026). Therefore, it’s very important to evaluate how specific herbicides and their application rates affect weed control and the agronomic performance within the semi-deciduous forest agro-ecological zone of Ghana.

    MATERIALS AND METHODS

    Experimental sites
     
    Field trials were carried out in the 2023 cropping season at two separate sites, Abodom (Birim North District, Eastern Region) and Nkwanta (Mampong Municipality, Ashanti Region), Ghana. Abodom lies between latitude 6°20′18″N and longitude 0°59′44″W, elevated at 156 m above sea level, within the semi-deciduous forest zone. This trial site experience bimodal rainfall pattern, major season (March to July) and minor season (August to October). Yearly rainfall ranges from 1500 to 2000 mm, the average daily temperature is 25.2°C and the mean relative humidity is 55-59%. Soils are mainly silty sand, appropriate for cowpea production (Issaka et al., 2012; Asubonteng et al., 2001).
           
    Nkwanta lies between latitude 01°45′N and longitude 1°24′W and is elevated at 402 m above sea level, positioned in the forest-savannah transitional zone. The area experiences bimodal rainfall, with yearly rainfall of 1094-1200 mm, major rains in (March to July) and minor rains in (August to November), with a daily average temperature of 30°C. Soils are well-drained, pebbly, moderately fertile, with a pH 6.0-6.5 and good water-holding capacity. Common weeds include Cyperus rotundus, Cynodon plectostachus and Panicum maximum. Nearly 80% of land is under smallholder cultivation (Tachie-Menson et al., 2021; Bolfrey-Arku et al., 2006).
     
    Experimental design and treatments
     
    Design
     
    A single-factor experiment was laid out in a randomized complete block design (RCBD) with three replications at each site. Ten treatments were evaluated, with each replication containing ten plots of 4 m × 3 m, separated by 1 m between plots and 2 m between blocks, giving a total of 30 plots per site (529.5 m2).
     
    Treatments
     
    Two pre-emergence herbicides (Butachlor 50 EC and Alligator 400 EC) were applied at three rates each and one post-emergence herbicide (Agill 100 EC) at three rates, along with a manual weeding control (2, 4, 6 WAS). The treatments were:
    • T1: Butachlor 50 EC, 1.8 ml a.i./ha.
    •  T2: Butachlor 50 EC, 3.15 ml a.i./ha.
    •  T3: Butachlor 50 EC, 3.6 ml a.i./ha.
    •  T4: Alligator 400 EC, 1.62 ml a.i./ha.
    •  T5: Alligator 400 EC, 1.98 ml a.i./ha.
    • T6: Alligator 400 EC, 2.16 ml a.i./ha.
    • T7: Agill 100 EC, 1.08 ml a.i./ha at 2, 4, 6 WAS.
    • T8: Agill 100 EC, 1.44 ml a.i./ha at 2, 4, 6 WAS.
    • T9: Agill 100 EC, 1.8 ml a.i./ha at 2, 4, 6 WAS.
    • T10: Manual weeding at 2, 4, 6 WAS.
     
    Planting material
     
    Cowpea variety ‘Zamzam’ was obtained from the Crop Research Institute, CSIR, Fumesua, Kumasi, Ashanti Region, Ghana.
     
    Land preparation and sowing
     
    Field preparation involved clearing with cutlasses and leveling with hand hoes. Planting at Abodom was on 20 May 2023 and at Nkwanta on 17 June 2023. Each plot had five rows, 0.6 m between rows, 0.2 m within rows, with one seed per hole at 4 cm depth, totaling 100 seeds per plot. No fertilizers were applied. Tools included meter rules and tapes (layout and growth measurements), pegs and tags (identification), knapsack sprayers (herbicide application) and electronic scales (grain measurement).
     
    Soil physiochemical properties of the experimental sites
     
    The two experimental sites differed considerably in soil physicochemical properties (Table 1). Abodom recorded higher organic carbon, organic matter, total nitrogen, and ECEC (1.48%, 2.95%, 0.16%, and 12.54 mol/kg) compared to Nkwanta (0.32%, 0.64%, 0.04%, and 3.02 mol/kg), indicating greater inherent fertility. Both sites were slightly acidic (pH 5.69 and 5.65), though Abodom’s silty loam texture contrasted sharply with Nkwanta’s sandy soil, likely influencing water retention, nutrient availability, and the differential herbicide and cowpea growth responses observed across locations.

    Table 1: Preliminary chemical and physical characteristics of soil at the study sites at 0-15 cm.


     
    Cultural practices
     
    Manual weed control
     
    Weeds were controlled by cutlass and hand-picking at 14-day intervals. Predominant weeds were Cyperus spp.
     
    Chemical weed control
     
    Pre-emergence herbicides were applied before sowing and post-emergence herbicides were applied at 2, 4 and 6 WAS, according to treatment rates.
     
    Pest and disease management
     
    Insect pests were controlled using emetine benzote (1.5 L/ha) and Karate 2.5 EC (50 ml per knapsack, 20 knapsacks/ha). Fungal diseases were monitored and controlled with Redomil at 1.5 kg/ha. Regular scouting was employed to detect early infections.
     
    Data collection
     
    Seedling emergence
     
    Emergence counts were conducted within two weeks of sowing and the percentage emergence was calculated.
     
    Growth parameters
     
    Plant height, number of branches and canopy spread were measured on five tagged plants per plot at 2, 4 and 6 WAP using meter rules and tapes.
     
    Phenological traits
     
    Days to 50% flowering and podding were recorded visually.
     
    Yield components
     
    At harvest, the number of plants, pods per plant, pod length, seeds per pod, thousand-grain weight and net grain yield were determined from the net plot. Pods were sun-dried before measurements and seed weights were obtained using electronic scales.

    Statistical analysis
     
    Data were subjected to ANOVA and treatment means were separated using least significant difference (LSD) at 5% probability level. Assumptions of normality and homogeneity of variance were checked before analysis.

    RESULTS AND DISCUSSION

    Effect of herbicide on growth parameters of cowpea
     
    Plant height (cm)
     
    At 14 days after sowing (DAS), herbicide application did not significantly influence cowpea plant height at Nkwanta (p = 0.377). The highest plant height was observed under 3.6 mL a.i./ha of Butachlor 50% EC, while the lowest occurred with 1.44 mL a.i./ha of Agil 100 EC. In contrast, plant height at Abodom differed significantly among treatments at the same growth stage (p<0.05), with 1.8 mL a.i./ha of Agil 100 EC producing the tallest plants and 3.6 mL a.i./ha of Butachlor 50% EC the shortest, excluding the control (Table 2).

    Table 2: Effect of different rates of herbicides on cowpea plant height (cm).


           
    At 28 DAS, no significant variation in plant height was recorded among treatments at Nkwanta (p=0.524). Here, 3.6 mL a.i./ha of Butachlor 50% EC resulted in the greatest height, while 3.15 mL a.i./ha of the same herbicide gave the lowest. However, a highly significant treatment effect was observed at Abodom (p<0.0003), where 1.8 mL a.i./ha of Agil 100 EC produced the maximum plant height and 3.6 mL a.i./ha of Butachlor 50% EC the minimum.
           
    By 42 DAS, plant height at Nkwanta differed significantly among herbicide treatments (p<0.011), with the tallest plants recorded under 3.6 mL a.i./ha of Butachlor 50% EC and the shortest under 1.62 mL a.i./ha of Alligator 400 EC. Similarly, a significant treatment effect was observed at Abodom (p = 9.28E), where 1.8 mL a.i./ha of Agil 100 EC consistently produced the greatest plant height, while 3.6 mL a.i./ha of Butachlor 50% EC resulted in the least (Table 2).
     
    Number of branches
     
    Herbicide active ingredient rates had no statistically significant effect on cowpea branching at 14, 28, or 42 DAS at Nkwanta (p>0.05) and a comparable lack of significance was observed at Abodom across all assessment periods (Table 3). Despite the absence of significant differences, treatment-related numerical trends were evident. At 14 DAS in Nkwanta, the weeded control recorded the highest branch number, while the lowest values occurred under 1.8 and 3.15 mL a.i./ha of Butachlor 50% EC. Conversely, at Abodom, 1.44 mL a.i./ha of Agil 100 EC produced the highest branch count, whereas the weeded control recorded the lowest. By 28 DAS, branching at Nkwanta peaked under 1.62 mL a.i./ha of Alligator 400 EC and declined most under 3.6 mL a.i./ha of Butachlor 50% EC. At Abodom, the highest and lowest values were associated with 1.8 mL a.i./ha of Agil 100 EC and 1.62 mL a.i./ha of Alligator 400 EC, respectively. At 42 DAS, the highest branch number at Nkwanta occurred under 2.16 mL a.i./ha of Alligator 400 EC, with the lowest recorded at 3.6 mL a.i./ha of the same herbicide. In Abodom, 1.44 mL a.i./ha of Agil 100 EC resulted in the highest branching, while 1.98 mL a.i./ha of Alligator 400 EC produced the lowest (Table 3).

    Table 3: Number of branches of cowpea under different herbicide treatments.


     
    Canopy spread (cm)
     
    Canopy spread of cowpea at Nkwanta was not significantly influenced by herbicide active ingredient concentration at any sampling time (14, 28, or 42 DAS; p>0.05). In contrast, significant treatment effects were observed at Abodom across all measurement periods (p<0.05). At 14 and 28 DAS, plots treated with 1.8 mL a.i./ha of Agil 100 EC (applied at 2, 4 and 6 WAS) recorded the greatest canopy spread and differed significantly from those treated with 3.6 mL a.i./ha of Butachlor 50% EC. By 42 DAS, the widest canopy was associated with 2.16 mL a.i./ha of Alligator 400 EC, which was significantly higher than values obtained under butachlor 50% EC (3.6 mL a.i./ha), Agil 100 EC (1.8 mL a.i./ha) and the manually weeded control (Table 4).

    Table 4: Canopy spread (cm) of cowpea under different herbicide treatments.


     
    Days to 50% flowering
     
    The days to 50% flowering of cowpea further showed significant differences (p<0.0002) among the various herbicide active ingredient concentrations for the days to 50% flowering in Nkwanta with 3.6 mL a.i/ha of Butachlor 50% EC had recorded the maximum and 2.16 mL a.i/ha of Alligator 400 EC had recorded the minimum whiles there was no significant difference (p = 0.4176) among the various herbicide active ingredient concentrations for the days to 50% flowering in Abodom at the rate of 3.15 mL a.i/ha of Butachlor 50% EC had recorded the maximum and weeding at (2, 4 and 6 WAS) as control had recorded the minimum (Table 5).

    Table 5: Days to 50% flowering of cowpea.


     
    Days to 50% podding
     
    The results from (Table 6) for the days to 50% podding of cowpea indicated significant differences (p<1.77E-06) among the various concentrations of herbicide active ingredient in Abodom with the rate of 1.8 mL a.i/ha of Butachlor 50% EC had recorded the maximum and weeding at (2, 4 and 6 WAS) as control had recorded the minimum whiles there were no significant differences (p>0.2004) for the days to 50% podding of cowpea in Nkwanta with the rate of 3.6 mL a.i/ha of Butachlor 50% EC had recorded the maximum and 1.08 mL a.i/ha of Agil 100 EC (2, 4 and 6 WAS) had recorded the minimum.

    Table 6: Days to 50% podding of cowpea.


     
    Yield and yield-related parameters
     
    Effect of herbicide application on cowpea yield and yield components
     
    At Nkwanta, cowpea yield and its associated components were not significantly influenced (p>0.05) by the different herbicide active ingredient rates applied. Pod length, number of pods per plant, seeds per pod, thousand-seed weight and grain yield remained statistically comparable across treatments. Nonetheless, numerical variations were observed. The longest pods occurred under the weeding treatment, whereas the shortest pods were recorded at 3.15 mL a.i./ha of Butachlor 50% EC. The highest number of pods per plant was obtained at 1.08 mL a.i./ha of Agil 100 EC, while the lowest was observed at 3.6 mL a.i./ha of Butachlor 50% EC. Seeds per pod peaked at 1.8 mL a.i./ha of Butachlor 50% EC and declined at 3.15 mL a.i./ha of the same herbicide. Thousand-seed weight was greatest at 3.15 mL a.i./ha of Butachlor 50% EC and lowest at 1.44 mL a.i./ha of Agil 100 EC. Grain yield was numerically highest at 1.62 mL a.i./ha of Alligator 400 EC and lowest at 3.6 mL a.i./ha of Butachlor 50% EC (Table 7).

    Table 7: Effect of herbicides on cowpea yield and yield parameters.


           
    In contrast, at Abodom, herbicide treatments significantly affected pod length and grain yield. Pod length was highest under the weeding treatment and lowest at 3.6 mL a.i./ha of Butachlor 50% EC. Grain yield reached its maximum at 1.62 mL a.i./ha of Alligator 400 EC and 1.8 mL a.i./ha of Agil 100 EC. However, pods per plant, seeds per pod and thousand-seed weight did not differ significantly among treatments. Despite this, the highest number of pods per plant was observed at 1.62 mL a.i./ha of Alligator 400 EC, while the lowest occurred at 1.8 mL a.i./ha of Agil 100 EC. Seeds per pod were highest at 2.16 mL a.i./ha of Alligator 400 EC, with the lowest values recorded at 1.8 and 3.6 mL a.i./ha of butachlor 50% EC (Table 7).
     
    Effects of herbicide regimes on vegetative growth
     
    Plant height
     
    Cowpea height showed a strong site × herbicide interaction, revealing itself in radically different responses at Nkwanta and Abodom. At Nkwanta, variation in herbicide rate did not affect the early vegetative development, with differences that are statistically significant appearing only at later stages of growth. On the other hand, cowpea maintained at Abodom recorded vigorous and sustained response to treatment during the entire period of growth, implying that plant growth at this site was more sensitive to weed management practices under prevailing environmental conditions.
           
    These different reactions match up with the ways the herbicides work and how picky they are. Butachlor is a pre-emergence chloroacetanilide that mostly keeps sprouting weeds in check, but can put some pressure on the crop when used at higher doses. Pendimethalin (Alligator 400 EC) also interferes with the growth of roots and shoots of weeds at the initial stage of their emergence. In contrast, Agil 100 EC (propaquizafop), a selective post-emergence herbicide for the control of grasses, is safe to broadleaved crops such as cowpea. This, therefore, means that the superior plant height recorded under the Agil treatments at Abodom could be attributed to adequate post-emergence grass control, which reduced competition for light, water and nutrients under high weed pressure conditions. A similar trend has, however, been reported across all agroecological conditions. Cruz et al., (2020) noted that the integrated herbicide program, which controlled grasses, resulted in greater height of cowpea, while Yadav et al., (2017) noted better vegetative growth from the application of pendimethalin, supported by subsequent control of weeds. Selective herbicides and hoe weeding have also been found to increase the height of cowpea as compared to unweeded plots by Kumar et al., (2025), though responses were seasonal. Such a relatively lower response at Nkwanta can be attributed to site limitations comprising lower rainfall, higher temperatures and well-drained pebbly soils that reduce weed competition, plus less dynamic benefit from capture resources facilitated by herbicide intervention (Guuroh et al., 2025). This interpretation is an inspiration from Kusi et al., (2025), who found strong genotype × environment interaction effects on growth performance across locations in Ghana.
     
    Branching
     
    Branching exhibited very low sensitivity to the herbicide treatments at both locations, with only slight numerical differences among regimes. This clearly shows that in the Zamzam cowpea variety, branching is relatively less responsive to moderate contrasts of weed management compared to such attributes as plant height or canopy expansion and more so, largely dependent on inherent genetic controls and general resource status (Ibrahim, 2013; Wang et al., 2006).
           
    These results fall in line with earlier reports that stated, when interference from weeds is properly controlled, differences in weed control strategies have a negligible effect on branch and leaf production (Ali et al., 2015; Felix et al., 2019). Works of literature available further go ahead to note that the flexibility of branching in cowpea is prompted by plant population density and nutrient availability rather than minor variations among equally effective options for weed management (Satodiya et al., 2015; Helmy et al., 2015).
     
    Canopy spread
     
    Responses in canopy spread varied markedly between sites. At Nkwanta, canopy development was largely unaffected by the herbicide regimes, while at Abodom, distinct and consistent treatment effects were evident throughout the crop growth cycle. Notably, applications of Agil 100 EC and the higher doses of Alligator 400 EC repeatedly resulted in broader canopy expansion, whereas increased rates of Butachlor were linked to comparatively restricted canopy growth. It demonstrates the importance of effective grass weed control in places like Abodom, where conditions favor the quick establishment of weeds. Propaquizafop-based herbicides selectively control grassy weeds, allowing for encouraging canopy closure, which will later suppress other secondary weeds by their shading effect (Attri et al., 2022; Bhullar et al., 2015). Better canopy spread improves light capture and radiation use efficiency supports more biomass production. Results that were comparable have been recorded from the cowpea production systems where all pre-emergence herbicides were based on pendimethalin and the timeliness of supplementary control measures enhanced canopy development more than when applied singly or with late hand-weeding (Nath et al., 2024). It was due to different environmental and soil characteristics. Rainfall was somewhat better at Abodom, with silty sandy soils probably encouraging more vigorous competition from weeds, thus increasing the importance of early chemical input for maximum canopy expansion (Dieleman et al., 2000; Anorvey et al., 2018). There is a relatively drier transitional climate at Nkwanta, accompanied by a different species composition of weeds-herbs may not be so competitive here; hence, less apparent influence of herbicide treatment on canopy development (Anorvey et al., 2018).
     
    Phenological responses: Flowering and podding
     
    The herbicide treatments induced generally slight and location-specific effects on cowpea phenological development. Flowering time varied slightly between treatments at Nkwanta, with higher rates of Butachlor application delaying the onset of flowering, most likely due to initial herbicide stress or changes in early crop-weed dynamics. This, therefore, indicated a strong phenological plasticity under specific environmental conditions prevailing at the site since flowering at Abodom was not responsive to the applied herbicide regimes (Quee et al., 2021). Patterns seen for podding further emphasize the role of local factors in guiding herbicide effects. Podding time at Nkwanta stayed mostly the same among treatments, while clear differences showed at Abodom. Some Butachlor uses delayed pod start when compared to manual weeding. Delays might be associated with slower crop recovery or short-term effects of herbicides under high humidity conditions with high weed pressure. Such trends corroborate earlier studies that asserted that pre-emergence herbicides, especially when applied at higher rates, may instigate minor delays in the development of crops (Quee et al., 2021; Ezebuiro et al., 2021). Normally, these shifts are limited and do not necessarily result in yield penalties (Cruz et al., 2020; Arshad et al., 2025). In a related situation, found that hoe weeding usually encourages an earlier start of flowering and pod formation compared to chemical control of weeds (Dennis et al., 2024).
           
    Overall, the mild and localized phenological reactions observed in the current experiment confirm the high tolerance of the Zamzam cowpea variety. But under agro-ecosystems which are characterized by a short growing period or high risk of terminal drought, even small delays in developmental stages might be agronomically meaningful and warrant more detailed analysis (Quee et al., 2021).
     
    Effects on yield and yield components
     
    Grain yield and its contributing characters were highly site-specific and treatment effects were more pronounced at Abodom than at Nkwanta. No significant differences in any yield component or overall grain yield were observed at Nkwanta, suggesting that the effectiveness of the weed control treatments evaluated was similar at this site.
           
    In contrast, the effects of treatments at Abodom were highly significant, especially for pod length and grain yield. Alligator 400 EC and Agil 100 EC at intermediate application rates contributed to maximum grain yields, while higher rates of Butachlor were associated with lesser performance. The lack of consistent differences among individual yield components indicated that the yield responses observed resulted mainly from a general improvement in plant growth and vigor rather than from isolated reproductive attributes (Ebone et al., 2020; Dias et al., 2011).
           
    The results line up with earlier studies showing that Butachlor’s effectiveness really depends on how much you use and what the environment’s like. Just dumping more doesn’t always mean you’ll get better yields (Chongdar et al., 2016). Other research from West Africa and South Asia found that cowpea yields improved with pendimethalin-based pre-emergence herbicides, especially when farmers combined them with good agronomic practices (Ibrahim, 2013). In this study, moderate doses of Alligator 400 EC kept yield numbers high, while hand weeding made pods longer but didn’t always boost the grain yield. That fits with what Dennis et al. (2024) found, which showed that carefully managed herbicide use can match or even beat hand weeding, plus it saves a lot of labor.

    CONCLUSION

    This study shows that chemical weed control really shapes how cowpea plants grow, develop and yield, but the results depend a lot on which herbicide you use, how much you apply and the local environment. At the Nkwanta site, spraying Butachlor 50% EC before the plants emerged (at 3.6 mL a.i./ha) led to strong, tall plants. But at Abodom, the best plant height and canopy came from using Agil 100 EC (1.8 mL a.i./ha) after the plants were up. No matter the treatment or location, branching didn’t respond much to the herbicides, which indicates that genetics drives this trait more than weed management practices.
           
    Grain yield and yield components played out differently depending on the site. In Nkwanta, changing the type or amount of herbicide barely touched the yield, so performance stayed steady across treatments. But in Abodom, yields improved when Alligator 400 EC at 1.62 mL a.i./ha or Agil 100 EC at 1.8 mL a.i./ha were applied. Clearly, knocking back grass weeds matters more in spots with heavier weed pressure. Increasing herbicide doses higher, especially with Butachlor, didn’t boost yields much and sometimes even slowed down the plants’ move into reproductive stages.
           
    Altogether, the results showed that using moderate amounts of herbicide works better than going heavy and post-emergence, grass-targeting sprays really help when weeds are thick. The big influence of location on how treatments work just shows that blanket herbicide advice doesn’t cut it; farmers need weed control plans that fit their specific fields. Further research such as how long herbicide residues stick around, the best timing for applications and how different cowpea varieties react to these chemicals. Results will help build more sustainable and productive cowpea farming systems.

    ACKNOWLEDGEMENT

    I gratefully acknowledge the cooperation of the Abodom farming community, with particular appreciation to Mr. Oteng Kofi, the Chief Farmer, for his invaluable support and assistance throughout and beyond the fieldwork period. I also extend sincere thanks to Amuzu Godwin, Mr. Adebah Ebenezer and Mr. Senaye Raphael of the New Abirem Cocoa Health and Extension Division for their encouragement, as well as their constructive comments and technical input.

    CONFLICT OF INTEREST

    All authors declare that they have no conflict of interest.

    REFERENCES


    1. Asare, A.T., Mensah, T.A., Tagoe, S.M.A. and Asante, D.K.A. (2020). Identification of new sources of rust resistance in cowpea [Vigna Unguiculata (L.) Walp] germplasm using simple sequence repeat markers. Legume Research. 43(2): 185-189. doi: 10.18805/LR-488.

    2. Abate, T., Alene, A.D., Bergvinson, D., Shiferaw, B., Silim, S., Orr, A. and Asfaw, S. (2012). Tropical Grain Legumes in Africa and South Asia: Knowledge and Opportunities. PO Box 39063, Nairobi, Kenya: International Crops Research Institute for the SemiArid Tropics. 112 pp. ISBN: 978-92-9066-544-1. Order Code: BOE 056.

    3. Al-Hassan, R.M. and Diao, X.  (2007). Regional Disparities in Ghana: Policy Options and Public Investment Implications. IFPRI Discussion Papers 693, International Food Policy Research Institute (IFPRI).

    4. Ali, A., Streibig, J.C., Christensen, S. and Andreasen, C. (2015). Image based thresholds for weeds in maize fields. Weed Research. 55(1): 26-33.

    5. Anorvey, V., Asiedu, E. and Dapaah, H. (2018). Growth and yield of maize as influenced by using Lumax 537.5 SE for weed control in the transitional agro-ecological zone of Ghana. International Journal of Plant and Soil Science. 21(2): 1-11.

    6. Arshad, M.A., Abbas, R.N., Khaliq, A. and Ahmed, Z. (2025). Ecological approaches to sustainable soybean production with sequential herbicide applications and their impact on weed dynamics and crop yield. Journal of Ecological Engineering. 26(2): 231-257.

    7. Asubonteng, K.O. and Andah, E.I. (2001). Characterization and evaluation of inland valley watersheds for sustainable agricultural production: Case study of semi-deciduous forest zone in the Ashanti Region of Ghana. Tropics. 10(4): 539-553.

    8. Attri, M., Sagar, L., Sharma, J., Nesar, N.A., Bhochalaya, R.S. and Sandhu, R. (2022). Weed management in vegetables and flower crops in India. The Pharma Innovation Journal. pp 652-661.

    9. Bhullar, M.S., Kaur, T., Kaur, S. and Yadav, R. (2015). Weed management in vegetable and flower crop-based systems. Indian Journal of Weed Science. 47(3): 267-276.

    10. Bolfrey-Arku, G.E.K., Onokpise, O.U., Carson, A.G., Shilling, D.G. and Coultas, C.C. (2006). The speargrass [Imperata cylindrica (L.) Beauv.] menace in Ghana: Incidence, farmer perceptions and control practices in the forest and forest-savanna transition agro-ecological zones of Ghana. West African Journal of Applied Ecology. 10(1). https://doi.org/10.4314/wajae.v10i1.45713.

    11. Chongdar, S., Rai, A., Ghosh, A., Patra, K. and Kanti, P. (2016). Bioassay techniques for dose determination of non- traditional herbicides in cowpea [Vigna unguiculata (L.) Walp.]. International Journal of Current Research and Academic Review. 4(3): 178-182.

    12. Cruz, A.B.D.S., Albuquerque, J.D.A.A.D., Rocha, P.R.R., Souza, L.T.D., Cruz, D.L.D.S., Soares, M.B.B. and Silva, E.S.D. (2020). Effect of the use of pre-and post-emergence herbicides on nodulation and production of cowpea (Vigna unguiculata L.) in the Amazonian savannah. Agronomía Colombiana. 38(2): 280-286.

    13. Davis, A.S., Maxwell, B., Clements, D.R., Swanton, C.J., Valente, T., Dille, A. and Bohan, D.A. (2017). Integrated Weed Management for Sustainable Agriculture (Vol. 42). Burleigh Dodds Science Publishing.

    14. Dennis, A.O., Santo, K.G., Khalid, A.A., Atakora, K., Ntiamoah, D.A., Abdulai, M. and Eric, A. (2024). Growth, yield and grain quality of cowpea [Vigna unguiculata (L.) Walp.] and weed flora as affected by physical and chemical methods of weed control. Legume Science. 6(4): e70010.

    15. Dias, M.A.N., Pinto, T.L.F., Mondo, V.H.V., Cicero, S.M. and Pedrini, L.G. (2011). Direct effects of soybean seed vigor on weed competition. Revista Brasileira de Sementes. 33: 346-351.

    16. Dieleman, J.A., Mortensen, D.A., Buhler, D.D., Cambardella, C.A. and Moorman, T.B. (2000). Identifying associations among site properties and weed species abundance I: Multivariate analysis. Weed Science. 48(5): 567-575.

    17. Ebone, L.A., Caverzan, A., Tagliari, A., Chiomento, J.L.T., Silveira, D.C. and Chavarria, G. (2020). Soybean seed vigor: Uniformity and growth as key factors to improve yield. Agronomy. 10(4): 545.

    18. Ezebuiro, P., Yakubu, A.I. and Audu, M. (2021). Evaluation of three pre-emergence herbicides for weed control in soybean [Glycine max (L.) Merr.] in Dutsinma and Sokoto, Sudan savanna. FUDMA Journal of Sciences. 5(4): 368-374.

    19. FAO. (2019). FAO Statistics. Food and Agriculture Organization of the United Nations.

    20. Felix, F., Bonsiysi, B.I., Venasius, W.L., Christina, N.K., Nkongho, E.C., Annih, M.G. and Woin, N. (2019). Growth and yield response of maize (Zea mays L.) to different weed control methods in the western highlands of Cameroon. Journal of Agriculture and Crops. 5(2): 15-22.

    21. Gupta, K.C., Gupta, A.K. and Rani, S. (2016). Weed management in cowpea [Vigna unguiculata (L.) Walp.] under rainfed conditions. International Journal of Agricultural Sciences. 12(2): 238-240. https://doi.org/10.15740/HAS/IJAS/12.2/ 238-240.

    22. Guuroh, R.T., Nero, B.F., Folega, F., Oduro, K.A., Kalanzi, F., Adeyiga, G.K. and Amponsah, E. (2025). Woody and herbaceous species diversity respond differently to environmental variables in semiarid areas in Ghana. Ecology and Evolution. 15(4): e71253.

    23. Helmy, A.A., Hassan, H.H. and Ibrahimet, H. (2015). Influence of planting density and bio-nitrogen fertilization on productivity of cowpea. American-Eurasian Journal of Agricultural and Environmental Sciences. 15(10): 1953-1961.

    24. Ibrahim, U. (2013). Effect of pre-emergence herbicides on weed control and performance of cowpea. Journal of Agricultural Sciences. 8(2): 76-81.

    25. Issaka, R.N., Buri, M.M., Tobita, S., Nakamura, S. and Owusu- Adjei, E. (2012). Indigenous Fertilizing Materials to Enhance Soil Productivity in Ghana. In Soil Fertility Improvement and Integrated Nutrient Management-A Global Perspective. (pp. 119-134).

    26. Kumar, J.S., Sunitha, S., Saravanan, R., Thangamani, C., Suresh, V., Mamatha, K. and Kour, M. (2025). Sustainable approaches for weed management in taro cultivation: Analysis using mixed effect model in diverse agroclimatic conditions. Weed Research. 65(3): e70026.

    27. Kusi, F., Amoah, R.A., Attamah, P., Alhassan, S., Yahaya, D., Awuku, J.F. and Asante, I. (2025). Genotype × environment interaction effect on grain yield of cowpea [Vigna unguiculata (L.) Walp.] in deciduous forest and Sudan savanna ecologies of Ghana. Plos One. 20(1): e0314464.

    28. Langyintuo, A.S., Lowenberg-DeBoer, J. and Faye, M. (2003). Cowpea supply and demand in West and Central Africa. Field Crops Research. 82(2-3): 215-231.

    29. Manibharathi, S., Swaminathan, C., Somasundaram, S., Kathirvelan, P. and Kannan, P. (2024). Weed management practices in cowpea (Vigna unguiculata L.): A review. Legume Research. 47(12): 2019-2027. doi: 10.18805/LR-5306.

    30. Manisankar, G., Ghosh, P., Malik, G.C. and Banerjee, M. (2022). Recent trends in chemical weed management: A review. The Pharma Innovation Journal. 11(4): 745-753.

    31. Marinov-Serafimov, P. (2015). Determination of allelopathic effect of some invasive weed species on germination and initial development of grain legume crops. Pesticides and Phytomedicine. 25(3): 251-259. https://doi.org/10.2298/ PIF1003251M.

    32. Nesha, M., Dutta, D. and Krishna, V.J. (2026). Assessing the impact of quinchlorac 35% SC on weed flora, soil nutrient and microbial status in transplanted boro rice (Oryza sativa L.). Indian Journal of Agricultural Research. 60(6): 861- 868. doi: 10.18805/IJARe.A-6472.

    33. Nath, C.P., Singh, R.G., Choudhary, V.K., Datta, D., Nandan, R. and Singh, S.S. (2024). Challenges and alternatives of herbicide-based weed management. Agronomy. 14(1): 126. https://doi.org/10.3390/agronomy14010126.

    34. Olorunmaiye, K.S. (2010). Reproductive performance of two cowpea [Vigna unguiculata (L.) Walp.] varieties, Ife Brown and TVX3236, as influenced by imidazolinone and dinitroaniline herbicides. Australian Journal of Agricultural Engineering. 1(3): 101-105.

    35. Quee, D.D., Kamanda, P.J., Saffa, M.D. and Norman, J.E. (2021). Differential responses of two cowpea [Vigna unguiculata (L.) Walp.] genotypes to pre-emergence herbicides in the savannah woodland and rainforest agroclimatic regions of Sierra Leone. World Journal of Advanced Research and Reviews. 10(1): 343-355.

    36. Rani, B.S., Chandrika, V., Reddy, G.P., Nagamadhuri, K.V., Sudhakar, P. and Sagar, G.K. (2024). Response of weed management practices on yield loss, soil enzyme activity and microbial populations in maize (Zea mays L.). Indian Journal of Agricultural Research. 58(3): 474-479. doi: 10.18805/IJARe.A-6068.

    37. Satodiya, B.N., Patel, H.C. and Soni, N.V. (2015). Effect of planting density and integrated nutrient management on flowering, growth and yield of vegetable cowpea [Vigna unguiculata (L.) Walp]. Asian J. Hort. 10(2): 232-236.

    38. Sichone, R. and Mweetwa, A.M. (2018). Soil nutrient status and cowpea biological nitrogen fixation in a maize-cowpea rotation under conservation farming. Journal of Agricultural Science. 10(6): 136.

    39. Simunji, S., Munyinda, K.L., Lungu, O.I., Mweetwa, A.M. and Phiri, E. (2019). Evaluation of cowpea [Vigna unguiculata (L.) Walp.] genotypes for biological nitrogen fixation in maize- cowpea crop rotation. Sustainable Agriculture Research. 8(1): 82-93.

    40. Tachie-Menson, J.W., Buah, J.N., Adu, M.O. and Afutu, E. (2021). Morphological diversity in purple nutsedge from four agro-ecological zones in Ghana. Heliyon. 7(7): e07661.

    41. Ugbe, L.A., Ndaeyo, N.U. and Enyong, J.F. (2016). Efficacy of selected herbicides on weed control, cowpea [Vigna unguiculata (L.) Walp.] performance and economic returns in Akamkpa, southeastern Nigeria. International Journal of Agriculture. 19: 19-27.

    42. Valenzuela, H. and Smith, J. (2002). Cowpea. Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawai‘i at Mânoa.

    43. Wang, G., McGiffen, J. M.E., Ehlers, J.D. and Marchi, E.C. (2006). Competitive ability of cowpea genotypes with different growth habits. Weed Science. 54(4): 775-782.

    44. Yadav, T., Nisha, K.C., Chopra, N.K., Yadav, M.R., Kumar, R., Rathore, D.K. and Singh, M. (2017). Weed management in cowpea: A review. International Journal of Current Microbiology and Applied Sciences. 6(2): 1373-1385.
    In this Article
      Contact us
      Follow us
      Published In
      Indian Journal of Agricultural Research

      Editorial Board

      View all (0)