Residual Effect of Nitrogen and Weed Management Practices in Maize on Succeeding Groundnut

Maize is an exhaustive crop and highly responsive to nitrogen fertilizers. Farmers usually apply excessive doses of chemical fertilizers for producing higher yield Application of imbalanced and excessive nutrients led to decline in nutrient use efficiency making fertilizer consumption uneconomical and producing adverse effects on atmosphere (Aulakh and Adhya, 2005). Generally, fertilizer dose is recommended on the basis of individual crop response. Crops grown in fixed cropping sequence behave differently than their respective sole crops. However, the current system of fertilizer recommendation ignores the carry over effects of the fertilizers applied to the preceding crops. Nutrients applied to the preceding crops benefit the succeeding crops to a great extent (Nawale et al., 2007). Hence, it is essential that the cultivators are made aware of the possible carry over effects under sequential cropping.
 
Cereal-legume cropping system is considered to be one of the better alternatives for sustaining soil fertility and increasing the yield of cereal crops besides greater productivity per unit time and space and higher net returns of the system. Intensive cultivation through multiple cropping with proper planning in a sustainable way will help in increasing the food grain production for meeting the future demand and requirement. At present maize-groundnut cropping system is gaining importance under both rainfed and irrigated situations. Since maize is an exhaustive and weed sensitive crop, it removes lot of nutrients from soil (Ratnam et al., 2018). The succeeding groundnut builds up the soil nitrogen symbiotically and its leaf senescence character also improves the soil organic matter.
 
Saikia et al., (2000) reported that atrazine content in sandy loam soil at different intervals showed initial slow rate of loss of atrazine in soil up to 20 days and there after faster dissipation and at maize harvest (90 days) no detectable residue was left to injure the succeeding wheat, linseed and lentil. The total weed population was drastically reduced by the additive effect of the residual atrazine (0.25 to 1.0 kg ha^-1) and pendimethalin (0.75 kg ha^-1) in the succeeding soybean crop in maize-soybean sequential cropping system. Reddy et al., (2004) observed that pre-emergence atrazine and pre-emergence pendimethalin (0.5 kg ha^-1) applied to maize did not leave any significant amount of residues to adversely affect the germination and yield of succeeding groundnut But the information on the residual effect of herbicides (topramezone, tembotrione and 2,4 D) applied in maize on succeeding groundnut is meager. There is a need to assess the influence of new generation herbicides under maize-groundnut cropping system. Hence, residual effect of nitrogen and weed management practices applied in maize on succeeding groundnut was studied in the agro climatic zone of Andhra Pradesh, India.

The experiment was conducted during two consecutive rabi seasons of 2019-20 and 2020-21 on sandy loam soils of S.V. Agricultural College, Tirupati, Andhra Pradesh, which is geographically situated at 13.5°N latitude 79.5°E longitude and at an altitude of 182.9 m above mean sea level in the Southern Agro-climatic Zone of Andhra Pradesh. The soil was sandy loam in texture, neutral in soil reaction (6.85), low in organic carbon (0.28%) and available nitrogen (113.4 kg ha^-1), medium in available phosphorus (26.4 kg ha^-1) and potassium (180.9 kg ha^-1). The field experiment was laid out in a split plot design with three replications. The treatments comprised of four nitrogen management practices viz., control, recommended dose of fertilizer (180 kg ha^-1), green seeker directed N application (201.7  kg ha^-1) and soil test based fertilizer application (234 kg ha^-1) assigned to main plots and nine weed management practices viz., unweeded check, hand weeding twice at 15 and 30 DAS, pre-emergence application of atrazine 1.0 kg/ha fb post-emergence application of topramezone 30 g/ha, pre-emergence application of atrazine 1.0 kg/ha fb post-emergence application of tembotrione 120 g/ha, application of parthenium water extract 15 L/ha twice at 15 and 30 DAS, application of sunflower water extract 15 L/ha twice at 15 and 30 DAS, pre-emergence application of atrazine 1.0 kg/ha fb post-emergence application  of parthenium water extract 15 L/ha, pre-emergence application of atrazine 1.0 kg/ha fb post-emergence application of sunflower water extract 15 L/ha and brown manuring. In brown manuring treatmental plots (W9), sesbania 15 kg ha^-1 was sown in between rows of maize and it was knocked down with 2,4-D 1.0 kg ha^-1 at 35 DAS. Maize hybrid DHM -117 was sown and maintained with all general cultivation practices except for nitrogen and weed management methods.
 
Groundnut was raised after harvest of maize in undisturbed layout to study the residual effect of different nitrogen and weed management practices imposed in maize. Groundnut variety Dharani was sown at a spacing of spacing 22.5 cm x 10 cm in the first fortnight of December and harvested in second fortnight of March during both the years. Data recorded on different parameters of groundnut were statistically analyzed following the analysis of variance for split plot design as suggested by Panse and Sukhatme (1985).
 
Phytotoxicity rating on the groundnut crop was done at 10^th and 15^th day after sowing, as per the method suggested by Singh and Rao (1976).  Level of greenness was measured with Chlorophyll meter (model SPAD 502 of Minolta company, Japan). SPAD Chlorophyll Meter Readings (SCMR) were recorded by following the method of Turner and Jund (1991) at 15 DAS. SCMR data were recorded on 3^rd leaf from top of each representative plant, between 8.00 A.M. and 11.00 A.M. of the day. A mean of 15 readings from 5 representative plants per plot was taken. Efficacy of herbicide residue was calculated based on dry biomass weight of groundnut (Simarmata et al., 2018).
 

 

 
Where:
EHR= Efficacy of herbicide residue.
DBWt= Dry biomass weight of treated seedling.
DBWc= Dry biomass weight of control or untreated seedling.

Phytotoxic studies of groundnut
 
Nitrogen management practices imposed in preceding maize did not exert any significant influence on germination percentage, phytotoxicity, SPAD chlorophyll meter reading (SCMR) values and efficacy of herbicide in groundnut (Table 1).


 
Residual effect of weed management practices imposed in preceding maize was found to be non significant on germination percentage in groundnut, phytotoxicity and SPAD chlorophyll meter reading (SCMR) values but efficacy of herbicide residue found to be significant. The results obtained in this study are in line with the findings of Chand et al., (2014) and Sathyapriya and Chinnusamy (2020).
 
Significantly higher efficacy of herbicide residue was observed with brown manuring (W9), which was however, comparable with pre emergence application of atrazine 1.0 kg ha^-1 fb post emergence application of topramezone 30 g ha^-1 (W₃) and pre emergence application of atrazine 1.0 kg ha^-1 fb post emergence application of tembotrione 120 g ha^-1 (W₄) during both the years of study. Higher weed control efficiency in the these treatments in preceding maize might have led to lower density and dry weight of weeds in the succeeding groundnut, which favored the crop to accumulate higher dry matter. Pre emergence application of atrazine 1.0 kg ha^-1 fb post emergence application of sunflower water extract 15 l ha^-1 (W₈), pre emergence application of atrazine 1.0 kg ha^-1 fb post emergence application of parthenium water extract 15 l ha^-1  (W₇),  application of sunflower water extract 15 l ha^-1 twice at 15 and 30 DAS (W₆) and application of parthenium water extract  15 l ha^-1 twice at 15 and 30 DAS (W₅) were in parity with one another in registering lower efficacy of herbicide residue during both the years of study as well as in pooled mean.
 
Growth parameters, yield attributes and yield
 
Nitrogen management practices imposed in preceding maize did not exert any significant influence on yield attributes of groundnut (number of pods plant^-1, number of filled pods plant^-1, hundred pod weight, hundred kernel weight and shelling percentage) and yield (Table 1, 2 and 3).




 
Different weed management practices performed in preceding maize exerted remarkable influence on number of pods plant^-1, number of filled pods plant^-1, hundred pod weight and hundred kernel weight, pod yield but shelling percentage was found to be non significant. Similar trend was observed during both the years of study, including pooled mean.
 
Higher number of pods plant^-1, number of filled pods plant^-1,  hundred pod weight, hundred kernel weight pod yield were noticed with brown manuring (W₉), which was however, at par with hand weeding twice at 15 and 30 DAS (W₂), pre emergence application of atrazine 1.0 kg ha^-1 fb post emergence application of topramezone 30 g ha^-1 (W₃) and pre emergence application of atrazine 1.0 kg ha^-1 fb post emergence application of tembotrione 120 g ha^-1 (W₄). This might be due to reduced crop weed competition in succeeding groundnut that facilitated better partitioning of photosynthates leading to better pod development and filling which in turn led to higher yield. Similar observations were reported by Singh et al., (2012) in mustard, Nazreen et al., (2018) and Rani et al., (2019) in maize.
 
Economics
 
Gross returns, net returns and benefit-cost ratio of groundnut was considerably altered by weed management practices followed in preceding maize as presented in Table 3. Nitrogen management practices in preceding maize did not exert any significant influence on economics of groundnut. The interaction effect was not significant.
 
Among the weed management practices tested, gross returns, net returns and benefit-cost ratio of groundnut followed similar trend during both the years of study and as well as in pooled mean. Brown manuring (W₉) registered higher gross returns, net returns and benefit-cost ratio of groundnut, which was however, at par with hand weeding twice at 15 and 30 DAS (W₂), pre emergence application of atrazine 1.0 kg ha^-1 fb post emergence application of topramezone 30 g ha^-1 (W₃) and pre emergence application of atrazine 1.0 kg ha^-1 fb post emergence application of tembotrione 120 g ha^-1 (W₄). This may be attributed to higher pod yield due to reduced weed growth. Similar findings were reported by Mundra (2000) and Rani (2020).
 
Significantly  lower gross returns, net returns and benefit-cost ratio of groundnut were noticed with weedy check (W₁) and it was at par with application of parthenium water extract 15 l ha^-1 twice at 15 and 30 DAS (W₅), application of sunflower water extract 15 l ha^-1 twice at 15 and 30 DAS (W₆), pre emergence application of atrazine 1.0 kg ha^-1 fb post emergence application of parthenium water extract 15 l ha^-1  (W₇) and pre emergence application of atrazine 1.0 kg ha^-1 fb post emergence application of sunflower water extract 15 l ha^-1 (W₈) in the order of ascent. This might be attributed to low yields of groundnut due to severe crop weed competition.

Nitrogen management practices adopted in preceding maize did not exert any significant influence on the performance of succeeding groundnut. While, brown manuring or two hand weedings or sequential application of pre and post emergence herbicides applied in preceding maize were found to be effective and economic practices for realizing higher yields and net returns in succeeding groundnut. None of their interaction effects were found to be significant during both the years of study and in pooled mean.

Kadiri Saimaheswari is thankful to DST Inspire for aiding financial assistance during the course of study.

All the authors are declared the there is no conflict of interest for publication and all are willing to publish the research findings.