Improved rainy season fallow management in vertisols for resource conservation

A two rainy season field experiments (2023-2024) were conducted at ICAR‑Indian Institute of Millets Research, Hyderabad, India, to assess the utility of chemical fallow and dhaincha (Sesbania aculeata) green manuring on resource (soil moisture and nutrient) conservation as compared to traditional natural fallow. In this study, three fallow management treatments replicated eight times were evaluated in randomized complete block design setup. Results shows that chemical fallow and dhaincha green manuring have reduced the weed count (weed dry biomass) at 45 DAS by 76.5 (88.62) and 59.6% (76.5%) over natural fallow (23.4 weeds/m² and 422 kg ha^-1). On above reduced weed biomass, chemical fallow and dhiancha green manuring have reduced N, P and K uptake of weeds. Chemical fallow has 93.8, 93.2 and 90.6% lower weed nutrient removals has 10.9-19.4-8.3% higher available N-P-K nutrients than that in natural fallow (9.81-1.10-5.52 kg ha⁻¹ N-P-K uptake and 181.2, 17.25 and 240.1 kg ha⁻¹ N-P-K balance in soil). Though dhaincha green manuring (receiving 20-17.4-16.6 kg/ha N-P-K fertilizers) has lower weed nutrient removals, but huge nutrient accumulation in its dry biomass, hence it has a medium nutrient balance between chemical fallow and natural fallow. Chemical fallow has improved available soil moisture (mm/15 cm depth) by 26.5% over natural fallow (15.25 mm/15 cm), while dhinacha green manuring has 27.5% more water depletion over natural fallow. Dhaincha green manuring involves 4.4 times more costs than chemical fallow (Rs. 2400). Thus chemical fallow is both nutrient and water conservative practice to natural fallow while green manuring with biological N fixation is nutrient enriching practice.