Productivity and Profitability of Green Gram [Vigna radiata (L.) Wilczek] under System of Crop Intensification

Pulses, endowed with unique ability of nitrogen fixation constitute an important component of crop diversification and resource conservation in farming systems. Green gram [Vigna radiata (L.) Wilczek] is one of the thirteen food legumes grown in India and the third most important pulse crop after chickpea and pigeon pea.

Large areas are left fallow after the harvest of rice in India. These summer fallows can be effectively utilised for crop intensification and diversification. Integrating the two core principles of system of crop intensification (SCI) i.e., spacing and foliar nutrition, pulse crops can be raised effectively with minimum resources because of their uniqueness of nitrogen fixation, deep extensive root system, low crop water requirement and ability to withstand drought. SCI has emerged as a next generation agro-ecological innovation. SCI principles and practices build upon the productive potentials that derive from plants having larger, more efficient, longer-lived root systems and from their symbiotic relationships with a more abundant, diverse and active soil biota. System of crop intensification practices enable the crop to grow and develop potentially which provides enhanced production in sustainable and eco-friendly manner (Sowmya et al., 2022).

Planting pattern is an important factor determining individual crop plant performance. Spatial arrangement has been quantified as the mean rectangularity, or the ratio of distance between rows to the distance between plants within a row. The influence of rectangularity has been quantified by measuring mean population yield rather than individual plant yield within the population (Fanish and Raghavan, 2020). Many experimental findings proved that foliar application of nutrients increased the growth, better utilization of nutrients, yield attributes and yield in different pulse crops (Yeshwanth, 2020).

Considering the inadequate adoption of production technology that led to low productivity of pulses, various alternatives were considered over the conventional cultivation practices. In pursuit of extending the beneficial effects of SCI, a field study was proposed under system of crop intensification in green gram.

Field experiment was conducted during summer season in farmer’s field at Southern coastal plain (AEUI), Thiruvananthapuram district, Kerala (8°43’11’’N and 76 45’50’’ °E longitude; 52 m above mean sea level) during 2021-2022. The experimental soils were clay loamy in nature. The pH of the soils was 5.5, EC was 0.18 dS m^-1, organic carbon was 1.32% and available N, P and K were 328, 71.2 and 188 kg ha^-1, respectively. The experiment was laid out in a split plot design with four replications. The main plot treatments were S₁-spacing of 25 cm × 15 cm with single seedling per hill, S₂-spacing of 25 cm × 15 cm with double seedling per hill, S₃-spacing of 25 cm × 25 cm with single seedling per hill and S₄- spacing of 25 cm × 25 cm with double seedling per hill; Sub-plot treatments were F₁-Urea at 2%, F₂ -DAP at 2%, F₃-KNO₃ at 0.5% and F₄-DAP at 2% + KNO₃ at 0.5%. The green gram variety, CO 8 was used for the experiment. Foliar nutrition was given at 15 and 30 DAS. All other recommended package of practices was followed to raise the crop as per package of practices (KAU, 2016).

Five plants were selected randomly from each treatment and observations were made on growth and yield parameters. The yield parameters were recorded at the time of harvest in each treatment. The data were subjected to statistical analysis by applying the techniques of analysis of variance (Gomez and Gomez, 1984).

Growth attributes
 
The SCI practices had significant effect on all the growth attributes like plant height, number of branches per plant and total leaf area per plant at flowering and at harvest (Table 1).



At harvest, taller plants were recorded with a spacing of 25 cm × 15 cm with one seedling per hill (S₁) and the shortest plants were observed in S₂. The increase in plant height was due to increased cell division and cell elongation at higher level of nitrogen. This may be due to the competition between the inter and intra plants for sun-light, water and nutrients at closer spacing encouraged the vertical growth rather than horizontal growth (Sathiyavani et al., 2016). At flowering and harvest, KNO₃ @ 0.5% (F₃) recorded taller (46.44 and 54.25 cm, respectively) plants.

Branching is basically a genetic character but environmental conditions may also influence the number of branches per plant which play an important role in enhancing seed yield of green gram. A spacing of 25 cm × 25 cm with single seedling per hill (S₃) recorded more number of branches (5.18 and 6.56, respectively) at flowering and at harvest which was on par with S₁. The results clearly indicated that optimum spacing with reduced plant density might have provided more room for the plant to produce a greater number of branches. Lowest number of branches were recorded with double seedling per hill, this might be due to absence of horizontal space for the plant to expand its canopy due to high plant density. Foliar nutrition with KNO₃ @ 0.5% (F₃) recorded higher number of branches at both the stages. This would be due to the foliar application of higher concentration of multi nutrients at critical growth stages increased the growth and yield parameters (Neethu and Kaleeswari, 2018). These findings are corroborated with Jagtap et al., (2021).

Total leaf area per plant was significant with spacing and foliar nutrition at flowering only. S₁ recorded the highest leaf area (1110.26 cm²) and the lower leaf area (798.26 cm²) was recorded in S₄. Abid et al., (2018) also reported that better branching results in higher leaf area. Among the foliar nutrition treatments, DAP @ 2% + KNO₃ @ 0.5% (F₄) recorded the highest leaf area (995.29 cm²) and the lowest was recorded in F₂. Dey et al., (2017) also reported the increased availability of nutrients to plants leading to maximum plant growth in terms of plant height and leaf area.
 
Yield attributes and yield
 
A perusal of data revealed that the yield attributes and the yield were significantly influenced by crop intensification practices (Table 2).



The spacing of 25 cm × 25 cm with single seedling per hill (S₃) recorded higher number of pods and number of seeds per pod (27.06 and 12.25, respectively). Lower number of pods were observed in double seedlings per hill treatments (S₂ and S₄). However, S₄ recorded the lowest number of seeds per pod. This might be due to better utilisation of applied nutrients and less competition due to wider spacing. Foliar application of KNO₃ @ 0.5% (F₃) recorded higher value for number of pods and number of seeds per pod. When nitrogen and potassium were administered to the foliage during crucial phases of the crop, they were efficiently absorbed and transferred to the growing pods, resulting in better-filled pods.

Grain and haulm yield were significantly influenced by spacing. Adopting a spacing of 25 cm × 25 cm with single seedling per hill (S₃) recorded higher grain yield (899.44 kg ha^-1) which was on par with the spacing of 25 cm × 15 cm with one seedling per hill (S₁) and significantly superior to the other two spacings. This may be due to effective utilization of the growth resources, particularly due to space and solar radiation. These treatments have more leaf area indicating higher photosynthetic efficiency. When plants suffered due to mutual shading in case of adjoining rows and more plants in double seedling treatments the yield were drastically reduced by 10.7 per cent and 38.2 per cent in S₂ and S₄, respectively over their single seedling treatments. Similar results were reported by Sathiyavani et al., (2016). The high grain yield can also be due to the absence of weed interference as reported by Strydhorst et al., (2008). The spacing of 25 cm × 25 cm with double seedling per hill (S₄) recorded the lowest (555.70 kg ha^-1) seed yield. This may be due to more competition for resources between plants for water and soil nutrients led to lesser yield.

Among the foliar nutrition application, KNO₃ @ 0.5% (F₃) recorded higher grain yield (880.85 kg ha^-1) and it was on par with DAP @ 2% + KNO₃ @ 0.5% (F₄). Lower seed yield (665.19 kg ha^-1) was observed in urea @ 2% (F₁) and it was on par with DAP @ 2% (F₂). This might be due to less competition and effective utilisation of translocated photosynthates from source to sink. Optimization of N and K nutrient interactions resulted in better yield attributes. The results clearly demonstrated that supplying legume plants with foliar application of major nutrients has positive impact on boosting growth and increasing seed output. This might be also due to the ability of potassium nitrate to tolerate the water stress and thus might have helped in retention of a greater number of flowers leading to more yield attributes and yield. Similar results were also reported by (Neethu and Kaleeswari (2018) and Jagtap et al., (2021).

 The haulm yield was higher with the spacing of 25 cm × 15 cm with one seedling per hill (S₁) and it was on par with spacing of 25 cm × 25 cm with single seedling per hill (S₃), this is due to more amount of dry-matter produced by plant population per unit area. Even though more plant density was observed with the spacing of 25 cm × 15 cm with double seedling per hill (S₂), the amount of dry matter produced per plant was low due to heavy competition among the plants for growth resources that resulted in shorter plants. Foliar nutrition treatments followed same trend as of grain yield. The spraying of water-soluble nutrients increased uptake of nutrients and water, resulting in more photosynthesis and enhanced food accumulation thus resulting in higher dry matter production.
 
Economics
 
Adoption of cultivation practices depends on the economic feasibility. The perusal of data from the study indicated that economic analysis also had the same trend as that of seed yield of green-gram (Table 3a and 3b).

a

b

The net income and benefit cost ratio varied with spacing and number of seedlings per hill. The spacing of 25 cm × 25 cm or 25 cm × 15 cm with single seedling per hill (S₃ and S₁) supplied with foliar nutrition of KNO₃ @ 0.5% (F₃) or DAP @ 2% + KNO₃ @ 0.5% (F₄) recorded the higher net returns and benefit cost ratio (Rs. 28524 ha^-1 1.49, respectively). These results are supported with the findings of Sathiyavani et al., (2016) in green gram and Singh et al. (2009b) in black-gram. This might due to effective utilisation of both above and below ground resources effectively thus contributing to better growth and yield attributes.

Based on the above findings, it can be inferred that the yield of green gram is significantly influenced by plant population and foliar nutrition. In summer fallows, maintaining an optimum plant population with a spacing of 25 cm × 25 cm or 25 cm × 15 cm with single seedling per hill and foliar application of KNO₃ @ 0.5% or DAP @ 2% + KNO₃ @ 0.5% could fetch the most profitable returns. 

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