Effect of Inclusion of Legumes in Cropping System and their Residue Incorporation on the Yield of Maize

Maize (Zea mays L.) crop considered as “Queen of cereals” due to its versatile uses in food industry. It is the second most widely grown crop in the world and cultivated in tropics, sub-tropics to temperate climate. In India, it is cultivated in 9.20 m ha with the production of 27.80 m tonnes and 2965 kg ha^-1 productivity (Anonymous., 2020a), however in Gujarat, it is cultivated on 0.40 m ha area with production of 0.80 m tonnes and productivity 2170 kg ha^-1 (Anonymous., 2020b). As the demand of maize is increasing globally due to its multiple uses, there is a need to enhance its productivity. In the soil, organic matter content is highly related with the fertility of soil due to its contribution in improving soil’s physical, chemical and biological properties. Intensive cropping and tillage system resulted in substantial decrease in soil organic matter levels. Legumes are well known to add significant amount of organic carbon and atmospheric N fixed in the soil by more amount of leaf litter fall and root residue as compare to cereals. Therefore, there is need to assess legume crops in crop sequences as an alternate source for improvement of soil health and N supply in crop sequences.
       
Cheaper organic source which is abundantly available should be explored to satisfy the nutrient requirement of high yielding crops. The use of alternative organic inputs such as leguminous crop residues could be an option for maintaining soil fertility and sustain crop yields (Zoumane et al., 2000). Crop residues not only supplies all the major and micro nutrients, but also acts as a soil conditioner, improves the physical, chemical and biological properties (Mandal et al., 2004).
               
Diversification of cropping systems by incorporating short duration legume crops in the cereal based cropping sequence may be helpful in regaining the soil health. Legume crop residues can serve good source of plant nutrients and readily available energy for soil microbes because of their high nutrient content, low lignin content and easy decomposition as compare to cereal residue. The contribution of legume residues on productivity of the succeeding maize and their nitrogen economy is not thoroughly investigated. Hence, the present study was carried out with the objective to study the effect of different legume crop and their residue management with different nitrogen levels on growth and yield of maize crop.

A field experiment was conducted at B.A. College of Agriculture, Anand Agricultural University, Anand, Gujarat, India during summer-kharif seasons of years 2017 and 2018. The experimental field had an even topography with a gentle slope having good drainage and loamy sand in texture. The soil of the experimental field at 0-15 cm depth was low in organic carbon (0.34%) and available N (141.1 kg ha^-1), medium in available P₂O₅ (36.2 kg ha^-1) and K₂O (226.8 kg ha^-1) and slightly alkaline in reaction (pH-8.24, EC-0.18).
 
Experiment details
 
The experiment was laid in strip-split plot design with four replications. Three legume crops were grown in summer season and designated in vertical strips viz., green gram (C₁), groundnut (C₂) and cluster bean (C₃). Each legume crop strip had been sub-divided into two horizontal strips, for residue management treatments viz., residue removal (R₀) and residue incorporation (R₁); which further split into three intersectional sub plots designated with three nitrogen levels in succeeding kharif maize viz., 100% RDN (N₁), 75% RDN (N₂) and 50% RDN (N₃). The gross plot size was 3.6 m × 5 m and net plot size was 2.4 m × 4 m. green gram, groundnut and cluster bean were grown in summer season of both the years. All legumes in summer season received equal amounts of nutrients i.e., 20 kg N and 40 kg P₂O₅ per ha as basal dose. Sowing of legumes were done in February during both years. Harvesting of green gram was done in first fortnight of May and cluster bean and groundnut were harvested in first week of June. Maize var. GAWMH 2 was sown as main kharif crop and all the treatments were conferred upon it during both the years. The recommended dose of fertilizer for maize crop was 150-65-00 NPK, kg ha^-1 which given as per treatment.
 
Residue management
 
Residue yield was obtained by subtracting the grain yield of legumes of each net plot from their respective total dry biomass (above ground) and computed on hectare basis. Nutrient (N, P and K) content of residue of legumes were estimated by as per the procedures described in Jackson (1973). After incorporation of residue in soil one irrigation was given for proper decomposition. The biomass was allowed to decompose for about 20 days in the field.
 
Data recording
 
Five plants were selected and tagged at random from each net plot to record observations on various growth characters at different stages of maize. Five cobs were randomly selected from the net plot produce of maize and used for studying various yield parameters. Grain and straw yield from net plot converted to kg ha^-1 basis. Harvest index (HI) calculated as the ratio of economic yield to the total biological yield. Seed index calculated by counting and weighing 100 grains of maize grains from composite sample of the produce of the net plot.
 
Statistical analysis
 
The statistical analysis of the data of the kharif maize were performed in strip-split plot design as per the procedure described by Cochran and Cox (1957). Cropping systems, residue management and nitrogen management data were subjected to an ANOVA and means were compared using t-test, with α= 0.05 level.

Among the three summer legumes, cluster bean produced the highest amount of total residue (haulm+pod residue) followed by groundnut. The nutrient content of cluster bean residue was also found higher which resulted in highest amount of nutrient addition to the soil (76.34 kg ha^-1 N, 19.42 kg ha^-1 P and 42.01 kg ha^-1 K) followed by groundnut crop when residue was incorporated (Table 1).
 

 
Effect on succeeding maize
 
Effect of cropping systems
 
Growth parameters
 
Two-year study revealed that plant height of maize at harvest was not affected due to different cropping systems however, significantly higher leaf area at 60 DAS (3505 cm²), chlorophyll content at 60 DAS (24.18) and dry matter production at 60 DAS and at harvest (5659 and 14187 kg ha^-1, respectively) was observed with cluster bean-maize cropping sequence. Groundnut-maize (C₂) cropping sequence gave comparable results with cluster bean-maize (C₃) for leaf area and chlorophyll content (Table 2).
 

 
Yield parameters
 
Cropping systems had significant influence on various yield attributes and grain and straw yields of maize. Cluster bean-maize (C3) sequence provided significantly the highest cob length (16.80 cm) over rest of the sequences however, cob girth of maize was unaffected (Table 2). Cluster bean-maize (C₃) sequence recorded significantly the highest number of grains per cob (412.2), seed index (23.47 g), grain yield (3253 kg ha^-1) and straw yield of maize (5525 kg ha^-1) as compare to rest of the sequences. Harvest index remained unchanged in all sequences (Table 2).
       
The positive results of growing preceding legumes on maize growth and yield might be due to increased nitrogen and other nutrients availability in the soil for growing maize. The difference in growth and yield of maize observed between preceding legumes might be due to their different carry over capacity of nitrogen for the succeeding maize crop. Adeleke and Haruna (2012), Ammaji (2014) and Ali et al., (2015) also reported similar effect of different preceding legume crops on succeeding maize.
 
Effect of residue management
 
Growth parameters
 
Incorporation of legume residues (R₁) significantly enhanced plant height of maize at harvest (177.8 cm), leaf area at 60 DAS (3498 cm²), chlorophyll content at 60 DAS (24.20) and dry matter production of maize at 60 DAS and at harvest (5469 and 13939 kg ha^-1, respectively) as compare to residue removal (Table 2).
 
Yield parameters
 
Similar to growth parameters residue incorporation of different legumes on maize significantly benefitted the yield parameters i.e. cob length of maize (16.53 cm), cob girth of maize (14.98 cm) number of grains per cob of maize (409.9), seed index (23.21 g), grain yield (3301 kg ha^-1) and straw yield of maize (5562 kg ha^-1) as compare to residue removal. However, it failed to influence harvest index of the crop (Table 2).
       
The findings are in corroboration with the reports of Ammaji (2014), Rajkumara et al., (2014) and Ali et al., (2015) and it might be due to improved mineralization and of high amount of accumulated nitrogen in the legume residue which was returned to the soil slowly throughout the crop growing period. Addition of organic matter in form of crop residues also boosted availability of other nutrients which might have resulted in better crop growth of maize.
 
Effect of nitrogen management in maize
 
Growth parameters
 
Results indicated that full dose of nitrogen in maize significantly increased plant height at harvest (181.6 cm), leaf area at 60 DAS (3556 cm²), chlorophyll content at 60 DAS (25.22) and dry matter production at 60 DAS and at harvest (6065 and 14537 kg ha^-1, respectively) (Table 2).
 
Yield parameters
 
Full dose of nitrogen (100%) in maize significantly influenced cob length (17.95 cm), cob girth (15.62 cm), number of grains per cob (451.5), grain yield (3693 kg ha^-1), straw yield (6138 kg ha^-1), harvest index (37.48) and seed index (25.70 g) of maize (Table 2).
       
Improved growth parameters with full dose of N might be due to role of nitrogen in increasing cell division, cell elongation and chlorophyll formation. Similar findings reported by Rekha (2014) and Singh et al., (2015).
 
Relation between growth and yield parameters
 
Study of relation between different parameters while experimentation is important. Beneficial effect of different treatments on growth of crop, will ultimately result to positive effect on yield parameters and yield of crop. Linear regressions between different maize growth parameters and grain yield and yield parameters and grain yield presented in Fig 1 and Fig 2. Fig 1 shows that maize growth parameters effectively contribute to the maize grain yield. Plant height at harvest and leaf area at 60 DAS contributes 89% and 83% to grain yield of maize respectively. Moreover, the influence of the chlorophyll content and dry matter production at 60 DAS on the grain yield of maize is greater than plant height and leaf area (90% and 93% respectively). Fig 2 shows that maize grain yield is highly dependent to different yield parameters of maize. Number of grains per cob, cob length, seed index and cob girth strongly influence grain yield of maize with regression coefficients of 0.97, 0.95, 0.94 and 0.92 respectively.
 

 

 
Interaction effect
 
It was observed that the interaction between residue management and nitrogen management in maize (R × N) found significant, in case of grain yield of maize. The data revealed that residue incorporation of legumes with application of 100% RDN (R1N1) resulted in significantly the highest grain yield of maize (4035 kg ha^-1) than rest of combinations (Fig 3). Even residue incorporation significantly increases grain yield of maize at all levels of nitrogen. It increased grain yield by 20%, 11% and 7% as compare to residue removal at 100%, 75% and 50% recommended dose of nitrogen application.
 

 
Study of all three-factor interaction i.e. crping systems, residue management and nitrogen management in maize (C × R × N) revealed that in the second year (2018) interaction was found significant, in case of grain yield of maize. Cluster bean-maize cropping system with residue incorporation and 100% RDN (C3R1N1) recorded significantly higher grain yield of maize (4492 kg ha^-1), followed by groundnut-maize cropping system with similar treatment combination (C₂R₁N₁) (4130 kg ha^-1) (Fig 4).
 

               
Residue incorporation of cluster bean and groundnut with 75% RDN application in maize gave comparable results with residue removal with 100% RDN application for grain yield. This indicates 25% saving of fertilizer nitrogen application with residue incorporation of legume crops like cluster bean and groundnut. Further residue incorporation of cluster bean at 100% RDN application improve 25% yield increase over residue removal with similar nitrogen application level. However, the interaction was found significant only in second year it means more repetition of research needed for consistent result.

On the basis of results of two years of experimentation with cropping system, residue and nitrogen management, it can be concluded that cluster bean-maize cropping system found to be the best system followed by groundnut-maize cropping system which provided the highest improvement in growth parameters, yield attribute and grain and straw yield of maize. Residue incorporation of summer legumes proved beneficial in improving growth and yield parameters and grain and straw yield that indicated its potential to use as an alternative of organic manure. Study of correlation and regression between growth and yield parameters revealed strong positive relations between growth and yield parameter and maize grain yield. Combined application of residue and nitrogenous fertilizers had positive effects on maize grain yield, however incorporation was not able to reduce the nitrogen requirement through chemical means. Effect of crop residues applied for a short period cannot be assessed as it takes long time to build up organic matter content in the soil and meet the nutrient requirement of crops in a sequence. So long term experimentation is needed to examine the potential of these treatments with respect to reducing nitrogen fertilizer requirement.

None.