Soil water conservation and yield of winter sorghum (Sorghum bicolor L. Moench) as influenced by tillage, organic materials and nitrogen fertilizer in semi-arid tropical India

Soil water and nutrients play an important role in increasing sorghum (Sorghum bicolor L. Moench) yields in the Vertisols of semi-arid tropics during post-rainy season. The effects of tillage practices, organic materials and nitrogen fertilizer on soil properties, water conservation and yield of sorghum were evaluated during winter seasons of 1994–1995 and 1995–1996 on deep Vertisols at Bijapur in the semi-arid tropics of Karnataka State (Zone 3) of south India. Conservation and availability of water and nutrients during different stages of crop growth were increased by deeper tillage resulting in increased grain yield of winter sorghum. Medium and deep tillage increased the grain yield by 23% (1509 kg ha⁻¹) and 57% (1919 kg ha⁻¹) during 1994–1995 and 14% (1562 kg ha⁻¹) and 34% (1835 kg ha⁻¹) during 1995–1996, respectively, over shallow tillage. Water use efficiency increased from shallow (4.90 kg ha⁻¹ mm⁻¹) to deep tillage (7.30 kg ha⁻¹ mm⁻¹). Greater water use efficiency during 1994–1995 as compared to 1995–1996 was attributed to lower consumptive use of water during 1994–1995. Among organic materials, application of Leucaena loppings conserved larger amounts of water and increased winter sorghum yield and water use efficiency. Application of Leucaena loppings increased the winter sorghum grain yield by 9% (mean of 1994–1995 and 1995–1996) as compared to vermicompost. Significantly (P < 0.05) higher water use efficiency of 6.32 kg ha⁻¹ mm⁻¹ was observed in Leucaena loppings incorporated plots compared to 5.72 kg ha⁻¹ mm⁻¹ from vermicompost. Grain yield increased by 245 kg ha⁻¹ with application of 25 kg N ha⁻¹ in 1994–1995, and a further increase in N application to 50 kg ha⁻¹ increased the grain yield by about 349 kg ha⁻¹ in 1995–1996. Deep tillage with application of 25 kg N ha⁻¹ resulted in significantly higher sorghum yield (2047 kg ha⁻¹) than control during 1994–1995. Deep tillage with integrated nutrient management (organic and inorganic N sources) conserved higher amount of soil water and resulted in increased sorghum yields especially during drought years.