Effect of Reversal of Conservation Tillage on Soil Nutrient Availability and Crop Nutrient Uptake in Soybean in the Vertisols of Central India

Effect of conservation tillage on crop performance and soil properties has been studied extensively under different agro-climatic situations. However, the impact of reversal from conservation tillage to conventional tillage on crop growth and soil nutrient release is rarely addressed. Thus, this study was conducted by converting half of the eight years old conservation tillage experiment to the conventional one with a similar level of residue return to compare the effect on soil nutrient availability and nutrient uptake in soybean crops in the Vertisols of Central India. The conservation tillage treatments included no-tillage (NT) and reduced tillage (RT) with 100% NPK (T1), 100% NPK + farmyard manure (FYM) at 1.0 Mg-carbon (C)/ha (T2), and 100% NPK + FYM at 2.0 Mg-C/ha (T3). After eight years of the experiment, the RT and NT treatments were subjected to conventional tillage, and thus the tillage treatments were RT-CT, RT, NT, and NT-CT. After tillage reversal for three growing seasons, soybean yield and nutrient uptake (N, P, K) got significantly influenced by the tillage and nutrient management. Averaged across nutrient treatments, NT showed highest soil organic carbon (SOC) content (8.4 g/kg) in the surface 0-5 cm layer. However, at 5-15 cm depth, the SOC was greater in the RT-CT treatment by 14% over RT and by 5% in the NT-CT treatment over NT. The soil nutrient availability (N and P) was not significantly (p> 0.05) affected by the interaction effect of tillage and nutrient on the surface soil layer (0-5 cm). Interaction effect of tillage and nutrient was significant on available P content at 5-15 cm soil depth. In contrast to N, soil available P relatively increased with reversal of tillage in both NT and RT. Tillage reversal (NT-CT, RT-CT) and RT had significantly higher available potassium than NT in 0-5 and 5-15 cm soil layers. Among the treatments, NT-CT-T3 showed significantly higher seed N (85.49 kg/ha), P (10.05 kg/ha), and K (24.51 kg/ha) uptake in soybean. The study indicates conventional tillage with residue returns and integrated nutrient management could be a feasible alternative to overcome the limitations of no-till farming in the deep black Vertisols of Central India.