Efficient Tillage Practice for Maximum Infiltration, Rainwater Use Efficiency, and Profitability from Groundnuts under Semiarid Vertisols in Western India

Field experiments were conducted on groundnuts (Arachis hypogea) at Rajkot, India, during kharif from 1996 to 2006 to assess the efficiency of four tillage treatments: (1) shallow ploughing, (2) deep ploughing every year, (3) deep ploughing alternate years, and (4) deep ploughing once every three years. The tillage treatments were assessed for their effects on rainwater use efficiency (RWUE), soil moisture at depths of 0–15 and 15–30 cm, cumulative depth of infiltration, pod and straw yields attained, and sustainability over the years based on the sustainability yield index (SYI) criterion. The rainfall received during the crop growing period (June to September) ranged from 210.9 to 1,119.5 mm with a mean of 582.4 mm and variation of 47.4% over the years. A significantly higher mean pod yield of $770\mathrm{kg}/\mathrm{ha}$ and a straw yield of $\mathrm{2,134}\mathrm{kg}/\mathrm{ha}$ were attained under yearly deep ploughing than under shallow ploughing (664 and $\mathrm{1,840}\mathrm{kg}/\mathrm{ha}$). Yearly deep ploughing resulted in a mean infiltration depth of 12.8 cm and a RWUE of $1.59\mathrm{kg}/\mathrm{ha}/\mathrm{mm}$, which were significantly higher than those of shallow ploughing (8.8 cm and $1.37\mathrm{kg}/\mathrm{ha}/\mathrm{mm}$). Regression models of pod and straw yield were calibrated through monthly rainfall received during June to September and cumulative rainfall of these four months to assess the sustainability of the models over the years. The models attained coefficient of determination values in the ranges of 0.41 to 0.53, based on monthly rainfall, and 0.71 to 0.76, based on cumulative rainfall, for predicting the pod and straw yields of groundnuts based on the long-term study. The SYI ranged from 19.7 to 24.8% based on monthly rainfall and 25.6 to 30.9% based on cumulative rainfall for attaining maximum pod yield, and from 35.7 to 40.5% based on monthly rainfall and 38.0 to 44.8% based on cumulative rainfall for straw yield. The deep ploughing done every year resulted in maximum gross returns of 22,661 Rupees per hectare with benefit-cost ratio of 1.53, compared to shallow ploughing, with 19,543 Rupees per hectare and 1.43, respectively. The study indicated that yearly deep tillage was superior to attain maximum groundnut pod and straw yields, SYI, RWUE, gross returns, and benefit-cost ratio, in addition to providing maximum depth of infiltration. The deep ploughing done every alternate year and every three years were found to be the second and third best treatments for different parameters based on the study.