Performance of Green Manure Crops Sunhemp (Crotalaria juncea L.) and Dhaincha (Sesbania aculeata L.) in Rice Fallow
Abstract
In agriculture, green manure is created by leaving uprooted or sown crop parts to wither on afield so that they serve as a mulch and soil amendment. The plants used for green manure are often cover crops grown primarily for this purpose. Green manuring is the easiest and cheapest way to enrich soil fertility besides adding a huge amount of organic carbon to the soil and preventing soil erosion. The non-availability of green manure seed preceding paddy is a major constraint at the farmer level. In rice fallow pulses, yields are declining due to severe incidence of Yellow Mosaic Virus (YMV), and farmers are unable to reap pulses in rice fallow situations. Keeping in view the present scenario, this study on the performance of seed production of green manure crops for seed availability and profitability was taken up in farmers' fields as On Farm Testing. The performance of two crops, Sunhemp (Crotalaria juncea L.)and Dhaincha (Sesbania aculeata L.), was studied for seed yield in a rice fallow situation during Rabi 2021-22 and Rabi 2022-23 under a rainfed ecosystem by the DAATTC, Visakhapatnam District. The results revealed that a higher seed yield was observed in Sunhemp compared to Dhaincha. Seed yield increase was achieved to the tune of 84.00% in Sunhemp (1178 kg ha⁻¹) over Dhaincha (641 kg ha⁻¹). The increase in seed yield could be attributed to the better performance of the Sunhemp crop in terms of growth and yield components. The Sunhemp crop matured a week earlier than the Dhaincha crop.
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Introduction
India has changed from a region of food scarcity to food sufficiency by increased fertilizer use with subsidized prices, but the use of organic manures, including green manure, has declined substantially. Inorganic fertilizers are becoming more expensive; therefore, the sustainability of soil productivity has become a question. Hence, alternate sources to supplement inorganic fertilizers are needed. Green manuring is a low-cost and effective technology for minimizing the cost of fertilizers, enhancing soil structure, and safeguarding crop productivity. Crops grown for restoring or increasing the organic matter content in the soil are called green manure crops. The use of green manure crops in a cropping system is called 'Green Manuring.' A green manure crop should possess characteristics such as multipurpose use, short duration, fast growth, high nutrient accumulation ability, tolerance to adverse conditions, wide ecological adaptability, efficiency in water use, high nitrogen accumulation rates, high seed production, and pest and disease resistance. Inline with these properties, Sunhemp (Crotalaria juncea L.)and Dhaincha (Sesbania aculeata L.) are suitable species for green manuring with high biomass production of 20-25 t/ha (Tripathi et al., 2013). The lack of availability of adequate quality seed at an appropriate time and reasonable price for small and marginal farmers is a major constraint in Sunhemp and Dhaincha cultivation. Quality seed production of these crops has received meager importance in spite of huge demand from farmers. Further, the possibility of seed production under rice fallow situations paves the way for identifying suitable crops with high water use efficiency; hence, this study was taken up in farmers' fields. Objectives: 1. To create awareness among farmers on green manure cultivation in rice fallow situations. 2. To analyze the economics of seed production of green manure crops.
Conclusion
This two-year, on-farm evaluation conclusively demonstrates that Sunhemp (Crotalaria juncea L.)is significantly better suited than Dhaincha (Sesbania aculeata L.) for seed production in rice fallow systems of the Visakhapatnam region, and likely in similar agro-ecologies. Sunhemp outperformed Dhaincha in every critical aspect: it showed more vigorous growth, matured earlier, and delivered dramatically higher seed yields due to superior pod and seed formation. Crucially, this agronomic superiority translated into strong economic profitability, with a cost-benefit ratio more than double that of Dhaincha. Therefore, it is recommended that extension agencies and farmers actively promote Sunhemp as the green manure crop of choice for rice fallow seed production. This strategy achieves a dual purpose: it provides farmers with a lucrative supplemental income during the fallow period, and it simultaneously solves the critical problem of green manure seed unavailability at the farm gate. The seed produced locally can then be used by the same farmers or their community for green manuring in the subsequent pre-Kharif season, creating a self-sustaining cycle that enhances soil fertility, reduces dependency on chemical fertilizers, and improves the overall sustainability of the rice-based cropping system. This practice represents a simple, low-cost, and high-impact technology for resilient agriculture. CONFLICT OF INTEREST The authors declare no conflict of interest.
