​​Improved Herbicide Efficacy through Sole and Sequential Application of Herbicides for Higher Productivity of Urdbean (Vigna mungo) in Indian Semi-arid Tropics

Agriculture accounts for roughly 17.0% of national GDP and about 70% of the population is reliant on agriculture and allied activities for their livelihood (Anonymous, 2019). Pulses, which have a high amount of protein (20-25%) contribute about 14% of total protein supplements in the Indian diet. According to the Indian Council of Medical Research (ICMR), the minimum requirement for pulse is 70 gm capita^-1 day^-1, while only 35.8 grammes per person per day are available (Chopra, 2018).
               
Among pulses, urdbean (Vigna mungo L.) is one of India’s most important crops grown on 4.48-million-hectare area, producing 2.83 million tonnes with an average productivity of 641 kg ha^-1 (Directorate of Economics and Statics, 2018-19). It contains 48.0% carbohydrates, 22.3% protein, 154 mg calcium, 9.1 mg iron, 1.4 g fat, 0.37 g riboflavin and 0.42 mg thiamine in 100 gm^-1 (Asaduzzaman et al., 2010). During kharif (rainy) season, weeds are a major threat to urdbean productivity posing enormous competition for nutrients, water, light and space, especially during the early stages of crop growth. Because the crop is a poor weed competitor and yield losses ranging from 42-64% have been reported depending on the nature, density and duration of occurrence of crop-weed competition (Singh, 2011 and Choudhary et al., 2012). Weeds not only diminish the grain production but also deplete the soil minerals (Kaur et al., 2010). Hence, there is a need to find out the effective weed management practices to appreciate better growth and higher yield. Mechanical practices such as hand weeding (HW) and interculture operations are effective in controlling weed infestations under check but field operations are frequently hampered by labour shortages, high labour costs and incessant rains (Nath et al., 2016). Then, chemical weeding becomes essential in such situations and can be a decent alternative to HW. Chemical weed treatments are a good alternative to manual and mechanical weeding since they provide a weed-free environment during the first 30-35 days of growth (Das and Yaduraju, 2012). Therefore, keeping above facts in view, the present study was undertaken to assess the effect of different weed management strategies in kharif season with better efficacy and high productivity.

During the kharif season 2019, a field experiment was carried out at the Agricultural Research Station, Ummedganj, Kota, to assess the impact of various weed management strategies on weeds dry matter, weed control efficiency and ultimately the final harvest. The study involved ten treatments;  T₁- weedy check, T₂- two hand weeding at 20 and 40 DAS (day after sowing), T₃- pendimethalin 30% EC @ 1 kg ha^-1 (PE, pre-emergence); T₄- propaquizafop 2.5% w w^-1 @ 33.3 g a.i. ha^-1 + imazethapyr 3.75% w w^-1 (pre mix) ME(Micro emulsions) @ 50 g a.i. ha^-1 at 20 DAS, T₅- acifluorfen-sodium 16.5% EC (Emulsifiable concentrate) @ 140 g a.i. ha^-1 + clodinafop-propargyl 8% EC @ 70 g a.i. ha^-1 at 20 DAS, T₆- fomesafen 11.1% w w^-1 @ 220 g a.i. ha^-1 + fluazifop-p-butyl 11.1% w w^-1 @ 220 g a.i. ha^-1 at 20 DAS, T₇- pendimethalin 30% EC @ 1 kg a.i. ha^-1 fb propaquizafop 2.5% w w^-1 @  33.3 g a.i. ha^-1 + imazethapyr 3.75% w w^-1 (pre mix) ME @ 50 g a.i. ha^-1 at 20 DAS, T₈- pendimethalin 30% EC @ 1 kg a.i. ha^-1 fb acifluorfen-sodium 16.5% EC @ 140 g a.i. ha^-1 + clodinafop-propargyl 8% EC @ 70 g a.i. ha^-1 at 20 DAS, T₉- pendimethalin 30% EC @ 1 kg a.i. ha^-1 fb fomesafen 11.1% w w^-1 @  220 g a.i. ha^-1 + fluazifop-p-butyl 11.1% w w^-1 @ 220 g a.i. ha^-1 at 20 DAS and T₁₀- fluazifop-p-butyl 13.4% EC @ 250 g a.i. ha^-1 at 20 DAS which were evaluated in randomized complete block design with three replications. The size of experimental plots was 3.8 m broad and 4.0 m long. Weeds dry matter data was obtained using 0.5 m² quadrat at 2/3 random places in each treatment plot, then transformed to the square root of transformation (x + 0.5) to normalize their distribution. The collected weed samples were then dried in an oven for 48 hours at 70^oC till the constant weight is attained. Treatment wise weed control efficiency (WCE) was computed by using the formula as describes by Umrani and Boi (1982) as:
   
Where,
WCE (%) = Weed control efficiency.
DMC = Weed dry weight in weedy check plot.
DMT = Weed dry weight in treated plot.
       
The harvest index (HI) was calculated by the following formula a referred by Donald and Hamblin (1976) and expressed in %.
   
Statistical analysis
 
All of the data was subjected to analysis of variance (ANOVA). At P=0.05, critical difference (CD) was used to compare the treatment means. In order to evaluate the link between distinct traits as stated by Panse and Sukhatme (1978), correlation experiments were conducted.

The field experiment was considerately examination during crop growth stages to look the occurrence of different weed species at the particular stage (Fig 1). It was observed that three types of weeds were found in experiment trail i.e., monocot, dicot and sedge weeds. Among the monocot weeds Cynodon dactylon and Echinochloa crusgalli were the most prominent weeds. The dicot weeds viz., Digera arvensis and Celosia argentea were prominent. Cyperus rotundus was the prominent sedge. Similar botanic compositions of weeds were also reported by Singh et al., (2022) and Poornima et al., (2018). The share of monocot, dicot and sedge weeds of total weeds were 34.00, 49.46 and 17.18%, respectively. Weed dry matter of monocot, dicot, others and total weeds at 30, 60 DAS and at harvest in urdbean given in Table 1 to 3 respectively.
 

 

 

 

 
Effect on weeds 
 
The treatment T₂ (Two hand weeding at 20 and 40 DAS) recorded significantly lowest weeds dry matter accumulation of monocots {Cynodon dactylon (3.86, 4.30 and 3.08 kg ha^-1), Echinochloa crusgalli (4.73, 5.18 and 4.41 kg ha^-1), Eleusine indica (4.44, 4.56 and 3.13 kg ha^-1), Commelina benghalensis (3.33, 2.18 and 1.34 kg ha^-1)}; dicot {Digera arvensis (4.18,4.38 and 3.03 kg ha^-1), Celosia argentea (3.24, 3.58 and 2.67 kg ha^-1), Trianthema spp (4.04, 4.26 and 2.97 kg ha^-1), Parthenium hysterophorus (2.91, 3.18 and 2.11 kg ha^-1)}; sedge {Cyperus rotundus (3.23, 3.64 and 2.40 kg ha^-1)}; others (5.42, 5.64 and 4.18 kg ha^-1) and total weeds (12.21, 13.01 and 9.44 kg ha^-1) followed by T₇ (Pendimethalin (PE) fb propaquizafop + imazethapyr) during 30, 60 DAS and at harvest of crop and in case of Echinochlona crusagli application of T₄, T₅ also found at par with T₆ at 30 DAS.
       
Whereas, dry matter accumulation of Parthenium hysterophorus under application of T₄ was remained at par with T₇ and in case of Commelina benghalensis, the application of T₁₀ bring non-significant differences with T₇ at 60 DAS. While, in case of Echinochloa crusgalli, the application of T₁₀ also caused non-significant differences with T₇ at harvest of crop. The highest weed dry matter observed in T₁ (Weedy check) (Table 1 to 3). Propaquizafop inhibit ACCase enzyme at the initial stage of fatty acid synthesis this leads to killing most of monocot weeds same time Imezathyper control dicot weeds by inhibiting of acetolactate synthase (ALS) and this leads to death of synthase (ALS) and this leads to death of weeds. These results were in harmony with Susmitha et al., (2019) and Sahu et al., (2019) findings.
       
Highest weed control efficiency (84.57, 84.54 and 88.14%) recorded by T₂ (Two hand weeding at 20 and 40 DAS) followed by the T₇ [Pendimethalin (PE) fb propaquizafop + imazethapyr] and T₉ [Pendimethalin (PE) fb fomesafen + fluazifop-p-butyl] during at 30, 60 DAS and at harvest (Table 4). Pendimethalin (PE) fb propaquizafop + imazethapyr was recorded highest WCE might be because of T₇ treatment was records lowest weed population during initial growing period and HW records lowest weed population at critical crop-weed competition as compared to all other treatments. Singh et al., (2022), Meena et al., (2022) and Poornima et al., (2018) were also found similar results.
 

 
Effect on yield attributes
 
The data can be recorded and analyzed for yield attributing characters of urdbean (Table 4). Among the different treatment maximum number of pods plant^-1 (13.87), seeds pod^-1 (6.43) was observed under two hand weeding at 20 and 40 DAS and which was found to be at par with pendimethalin (PE) fb propaquizafop + imazethapyr and pendimethalin (PE) fb fomesafen + fluazifop-p-butyl. Yield attributes of urdbean might vary due to differences in growth parameters such dry matter production and weed population. Plant height, number of branches per plant, number of leaves and LAI all contributed to DM production. Two hand weeding resulted in good aeration and nutrient availability to crop growth throughout vital crop growth phase due to increased availability of water, space, nutrients to the crop plant and reduce crop-weed competition during the critical crop growth stage. Panda et al., (2015) and Kumar et al., (2018) were also found the Similar results.
 
Effect on yield of urdbean
 
All the weed control treatments were found to be significantly superior over the weedy check treatment shown in Table 4. During the year, treatment T₂ (Two hand weeding at 20 and 40 DAS) recorded significantly more grain yield (859 kg ha^-1), straw yield (1434 kg ha^-1), biological yield (2292 kg ha^-1) and harvest index (37.47%) which was at par with T₇ (Pendimethalin (PE) fb propaquizafop + imazethapyr) and T₉ (Pendimethalin (PE) fb fomesafen + fluazifop-p-butyl) and significantly superior over rest of treatments. It could be attributed to manual weeding reducing weed population and dry weight, as well as inhibition of weed development owing to higher plant density and lower spacing. T₁ (Weedy check) treatment resulted in a lower grain yield (395 kg ha^-1). Under present study existence of high positive correlation (Fig 2) between pods/plant and seeds/pod (r = 0.927 and 0.967, respectively) on grain yield, also validate the said statement. Similarly, total weed dry matter at 30, 60 DAS and at harvest was also has negative correlation (Fig 3) with grain yield (r = -0.906, -0.836 and -0.876) shown in Fig 3. These finding are in agreement with results of Singh et al., (2022) and Sandil et al., (2015).
 

 

The study results conclude that application of Pendimethalin 30% EC @ 1 kg a.i. ha^-1 (PE) fb propaquizafop 2.5% w w^-1 @ 33.3 g a.i. ha^-1 + imazethapyr 3.75% w w^-1 (pre mix) ME @ 50 g a.i. ha^-1 at 20 DAS may be recommended for attaining better weed control and higher crop yield in kharif urdbean under semi-arid condition.

On the behalf of all authors state that it is an original article and the data presented have neither been published in part nor under consideration for publication in any other journal. All the authors declare no conflicts of interest regarding this article.