Energetics, Productivity and Profitability of Soybean (Glycine max)-Based Intercropping Systems under Different Planting Patterns

Soybean [Glycine max (L.) Merr.], the “wonder crop”, capable of growing in the diverse environments, is considered as poor man’s meat for vegetarians as it has the highest amount of proteins (35-45 per cent) among the pulses. Being unique in its chemical composition viz., provides complete protein containing all the 8 essential amino acids, isoflavones, good source of antioxidant and vitamin E; it is a high-value multi-utility crop used as food, feed and in industry (Sikka et al., 2018). Moreover, being the leguminous crop it helps in fixing nitrogen and not only fulfills its own nitrogen requirement but also accounts for 40-60 kg N on hectare basis for the succeeding crops (Ronaki et al., 2018). In India, it covered an area of 10.3 mha with the production of 10.9 m tonnes and productivity of 1058 kg/ha during the year 2017-18 (www.indiastat.com).
       
In the era of shrinking land, water as well as energy resources, the agro-technique viz., intercropping can be an effective tool for enhancing crop productivity as well as profitability, especially for the small as well as marginal farmers (Singh et al., 2016). Intercropping enables in capturing the larger share of available resources as compared to the sole crop (Andersen et al., 2007). Moreover, the intercropping systems based on pulses improve both production as well as relative economic efficiency (Sankaranarayan et al., 2011) and can be considered as a key functional group for the role they play in agroecological services (Duchene et al., 2017). Generally, in intercropping systems, selection of the companion crops, as well as the suitable planting pattern both are important to reduce the inter as well as intraspecific competitions for resources (Ghanbari et al., 2010). In intercropping systems, niche differences in crop species can play an important role in resource capture and conservation thus leading to enhanced biological efficiency and yield advantages (Willey, 1979). Thus, the selection of appropriate crops is highly desirable to get higher benefits from the intercropping systems (Maitra et al., 2019).
       
In soybean, various options are available for intercropping viz., pulses, fodders, oilseeds, etc. Among pulses, mungbean is a short duration crop which fits well in various multiple as well as intercropping systems and moreover, its architecture is quite different from soybean. Cultivation of fodders as intercrop like cowpea and maize can help to meet the green fodder requirement of animals during the summer season (Sekhon et al., 2019; Tamta et al., 2019). Cowpea is a quick growing palatable fodder of short duration with high protein content (Kumar et al., 2016) and maize produces excellent quality fodder which is succulent and palatable having high production ability, wider adaptability and quick growing nature (Yadav et al., 2017). Groundnut is a legume cum oilseed crop that can be grown successfully in sequential, multiple and intercropping systems. Thus, the adoption of these crops if found suitable in the intercropping system based on soybean can play an important role in crop diversification, soil conservation and enhancing farmer’s profitability.
       
Energy analysis is considered necessary for efficient management of scarce resources and identification of economical and effective production practices for improved agricultural production. Moreover, evaluation of different cropping systems in terms of energetics is desirable as it is based on nutritional value of the system, so it is more stable and meaningful and does not vary with market value of the produce. In Punjab, the work on these aspects with respect to soybean based intercropping systems is limited. Thus, keeping all this in view, the study was conducted to evaluate the effect of soybean based intercropping systems using different planting patterns on productivity, economics and energetics to generate location specific, energy efficient, productive and profitable agro-technology for north-west India.

A field experiment was conducted consecutively for two years in kharif 2015 and 2016 at the Research Farm, Department of Agronomy, Punjab Agricultural University (30° 56'N, 75°52'E, altitude 247 m above mean sea level) on the fixed plots. Randomized complete block design with three replications was used to study the effect of different intercrops on growth and yield of soybean and to find out the best intercropping system. The texture of the soil was loamy sand. The soil of the experimental field was low in available N (178.0 kg/ha), medium in available P (20.2 kg/ha) and available K (179.0 kg/ha) and normal in soil reaction (pH 8.20) and electrical conductivity (0.4 mmhos/cm). The treatments comprised of soybean (45 cm) + mungbean  (1:1), soybean (45 cm) + cowpea (fodder) (1:1), soybean (45 cm) + groundnut (1:1),  soybean (45 cm) + maize (fodder)  (1:1), soybean (60 cm) +  mash (1:1), soybean (60 cm) +  mungbean (1:2), soybean (60 cm) + cowpea (F) (1:2), soybean (60 cm) + groundnut (1:2), soybean (60 cm) +  maize (F) (1:2), soybean (60 cm)+ maize (1:1) and sole soybean (45 cm). Soybean (cultivar SL 958), maize fodder (J 1006), cowpea fodder (CL 367), mungbean (ML 818), mash (Mash 114), groundnut (SG 84) and maize (PMH 1) were sown on 15 June and 10 June during 2015 and 2016, respectively. Soybean was harvested on 5 and 4 November during 2015 and 2016. Maize and cowpea fodders were harvested 40 days after sowing (DAS). Mungbean, mash, groundnut and maize for grain were harvested on 9 and 5 September, 9 and 5 September, 9 and 7 November and 17 and 13 September during 2015 and 2016, respectively. The seed rate of soybean was 75 kg/ha whereas the intercrops viz., mungbean, cowpea fodder, groundnut, maize fodder, mash and maize for grain were sown using the seed rate 20, 30, 95, 75, 20 and 20 kg/ha, respectively, on proportionate area basis. Soybean crop received recommended dose of fertilizers, viz., 30 kg N/ha in the form of urea and 60 kg P₂O₅/ha as single super phosphate along with 10 t FYM/ ha at the time of sowing. Soybean seed was treated with the recommended culture of Bradyrhizobium japonicum. In intercropping system, mungbean, cowpea (F), groundnut, maize (F), mash and maize received 12.5,18.75, 15.0, 62.5, 12.5 and 125 kg N/ ha and 40, 55, 20, 60, 25 and 60 kg P₂O₅/ ha, respectively, on the basis of proportionate area of the crops and placed in respective rows. Weeds were controlled by two hand weedings at 20 and 40 DAS under sole cropping. Yield attributes of soybean were recorded from the representative samples taken from each plot. The seed and straw yield were taken by weight of produce plot wise. For the comparison of treatments, the intercrop yields were converted into soybean equivalent yield (SEY) based on the minimum support prices of the main produce.  
Production efficiency of the intercropping system was calculated as under:
  In our studies, soybean equivalent yield is based on grain yield only although for energetics whole produce (grain as well as straw) was considered. To calculate input energy, quantity of all inputs used in the form of seed, labour, chemical fertilizer, herbicide, FYM, diesel etc. used in the crops of intercropping systems were taken into consideration and converted into energy equivalent by multiplying their per unit energy equivalents as suggested by Singh and Mittal (1992) (Table 2). Similarly, the farm produce was also expressed in terms of the output energy. The energy input and output values were expressed in Mega Joule (MJ). Net energy, energy use efficiency, energy productivity and specific energy were calculated as follows:        
In this study, benefit: cost was calculated on the basis of gross returns.

       

The data recorded for different parameters were statistically analyzed using F-test procedure with analysis of variance (ANOVA) technique for randomized complete block design. The comparisons between treatment means were made at 5% level of significance (P=0.05).

Growth and yield attributes of soybean
 
The height of soybean was significantly reduced by the intercropping of maize and cowpea as fodders in 1:1 or 1:2 ratio compared to the other intercropping systems (Table 1). The maximum height of soybean (91.5 cm) was obtained in soybean (45 cm) + groundnut (1:1) intercropping system closely followed by soybean (60 cm) + groundnut (1:2) (90 cm) and sole soybean (89.9 cm). The branches per plant were statistically at par in all the treatments except soybean (60 cm) + maize (1:1) which might be because of the competition exhibited by the maize crop due to its canopy and also for longer period of time as compared to other systems. The maximum number of pods was recorded in sole soybean which was statistically at par with soybean based intercropping system involving leguminous crops i.e. cowpea, groundnut and mash. The maximum yield of soybean (21.73 q/ha) was obtained in the sole plot and was significantly better than all other treatments. Sole cropped soybean outperformed the intercropped soybean crop (Kamara, 2019).
 

       
The intercropping systems showed superiority to sole cropping in total productivity. Maximum soybean equivalent yield was recorded in soybean (45 cm) + groundnut (1:1) intercropping system which was statistically at par with soybean (60 cm) + groundnut (1:2) and both these treatments were significantly better than rest of the intercropping systems. The higher soybean equivalent yield under intercropping was owing to higher biomass production and efficient use of available growth resources under intercropping than sole cropping (Willey, 1990). Mash crop failed to grow as intercrop successfully in soybean based intercropping system which might be due to more shading effect and competition for light resulting in weak plant growth resulting in no pod yield. Intercropping systems showed superiority to sole cropping in production efficiency except soybean + mash intercropping system. The maximum production efficiency was recorded in soybean (45 cm) + groundnut (1:1) system, which was statistically similar with soybean (60 cm) + groundnut (1:2) and significantly better than all the treatments.

Energetics
 
Energy used in different intercropping systems was computed to augment the energy-use efficiency. Evaluation of different intercropping systems through energetics is highly desirable, stable and meaningful. Energy inputs for different intercropping systems were computed for two years. Pooled data pertaining to energetics is shown in Table 3. The total energy input in different systems under study ranged from 11.30×10³ to 19.9×10³ MJ/ha. Sole soybean required least energy input and the maximum energy input was required in the soybean + maize (grain) intercropping system which might be because of more fertilizer application and labour requirement for harvesting and threshing. Total energy output was computed from the main product and the by-product of various crops in different intercropping systems and it ranged from 89.8×10³ to 589.6 ×10³ MJ/ha. Soybean (60 cm) + mash (1:1) recorded the minimum energy output whereas the maximum output of energy was obtained from soybean (60 cm) + maize fodder (1:2) intercropping system. The intercropping of cowpea or maize fodder with soybean either in 1:1 row ratio at 45 cm or 1:2 row ratio at 60 cm row spacing, groundnut in 1:1 row ratio with soybean at 45 cm and intercropping of maize for grain purpose with soybean sown at 60 cm in 1:1 row ratio resulted in significantly higher total energy output as compared to sole soybean crop. Soybean (60 cm) + maize (fodder) (1:2) recorded significantly higher total energy output as compared to all other treatments.
 

       
The maximum net energy balance was obtained in soybean (60 cm) + maize fodder (1:2) combination and it was significantly higher than the rest of the treatments. The least value of net energy was obtained in soybean (60 cm) + mash (1:1) intercropping system which might be because of the failure of mash crop due to shading effect of soybean crop. Among different systems, soybean (45 cm) + cowpea fodder (1:1), soybean (45 cm) + maize fodder (1:1), soybean (45 cm) + groundnut (1:1),  soybean (60 cm) + cowpea fodder (1:2), soybean (60 cm) + maize fodder (1:2) and soybean (60 cm) + maize (1:1) produced significantly higher net energy output as compared to sole soybean crop.
       
The maximum energy use efficiency was obtained in soybean (60 cm) + maize (1:2) which was statistically similar with soybean (45 cm) + maize (fodder) (1:1) system but significantly higher than rest of the intercropping systems. The highest energy productivity was recorded in soybean (45 cm) + groundnut (1:1) system which was significantly better than all other intercropping systems. Both, soybean (45 cm) + groundnut (1:1) and soybean (60 cm) + groundnut (1:2) systems produced significantly higher energy productivity as compared to sole soybean. Specific energy showed the opposite trend. Specific energy indicates the amount of energy used to produce one unit of grain. Specific energy was highest in soybean (60 cm) + mash (1:1) system and was statistically at par with soybean (60 cm) + maize grain (1:1) system and significantly higher as compared to other treatments. The minimum specific energy was recorded in soybean (45 cm) + groundnut (1:1) system where the maximum amount of energy productivity was obtained.
 
Economics
 
The highest gross returns as depicted in Table 4 were recorded in soybean (45 cm) + groundnut (1:1) system (Rs. 98185 /ha), followed by soybean (60 cm) + groundnut (1:2) (Rs. 92268/ha) and soybean (60 cm) + maize (F) (1:2) (Rs. 82840/ha). Maximum net returns were recorded in soybean (45 cm) + groundnut (1:1), followed by soybean (60 cm) + maize (F) (1:2) and soybean (45 cm) + maize (F) (1:1). The gap in gross returns between soybean based intercropping systems involving groundnut were wider which narrowed down in net returns because of more cost of cultivation of groundnut. Among the different intercropping systems, the maximum benefit - cost ratio of 2.49 was recorded with soybean (60 cm) +  maize fodder (1:2) followed by soybean (45 cm) + maize fodder (2.41)  in 1:1 row ratio, which might be because of more productivity of the dual crops in combination and relatively low production cost per unit of yield under this combination. The least benefit-cost ratio of 1.38 was obtained in soybean (60 cm) + mash (1:1) intercropping system mainly due to lowest gross returns because of the lowest yields obtained from this system.
 

Based on the study, it can be inferred that intercropping showed higher soybean equivalent yield than sole cropping of soybean. Among the intercropping systems, groundnut was the best intercrop which was planted with soybean sown at a row spacing of 45 cm or 60 cm in 1:1 or 1:2 ratio, as these treatments registered higher soybean equivalent yield and production efficiency. Both these systems had higher B:C, net returns and energy productivity as compared to sole soybean. Thus, intercropping of soybean with groundnut can be a profitable option for small and marginal farmers of north-west India.