Traditional rainwater management system (‘Haveli’) in Vertisols of central India improves carbon sequestration and biological soil fertility

Abstract

Farmers in Central India practice a unique rain water management system (‘Haveli’) based on impounding rain water in the fields during three months monsoon season (June–September) and draining out in October. Winter crops, mainly grain legumes are then grown that utilize the soil moisture conserved in the soil profile. We monitored the soil physico–chemical and fertility properties, C and N mineralization, microbial populations and biomass and soil enzymes in the 0–30cm soil layer at ten sites over three years at four stages viz., prior to submergence in summer (PS), during water-logging (WL), after drainage (AD) and after legume cropping (AC). Anaerobic conditions during water-logging (for 11 weeks) led to extensive losses of soil carbon amounting to 1900mgCkg−1 soil but no significant change in soil N. Post-drainage and decomposition of weeds (for 6 weeks), there was an increase in soil C of 3700mgCkg−1 and soil N of 74.1mgNkg−1 soil. Overall in 17 weeks, there was a net increase of 1800mgCkg−1 (+30.5%) and 87.5mgNkg−1 (+20.1%) amounting to soil C and N accretion rate of 15.1mgCkg−1 soilday−1 and 0.74mgNkg−1 soilday−1. Microbial biomass decreased by 19.7% during 11 weeks of water logging and improved by 54% in the 6 weeks aerobic phase; an overall increment of 23.5% (31mg microbial Ckg−1) in 17 weeks. Prolonged water-logging induced severe stress on microbial processes. However, post-drainage, there was significant improvement in microbial populations, nitrogen mineralization, soil enzymes and soil fertility. There were strong relationships between soil enzymes and microbial carbon; and, nitrogen mineralization and soil carbon. Results unequivocally demonstrated the benefits of rain-water conservation in Vertisols for carbon sequestration and nitrogen accretion and improvement of soil biological quality.