Rainwater, soil and nutrients conservation for improving productivity of citrus orchards in a drought prone region

Abstract

The abundant surface runoff along with top fertile soil in rainy season, followed by sub-optimal soil water content (SWC) in root zone of the plants during post-rainy period is one of the major causes of low productivity and decline of citrus orchards in tropics. Keeping this in view, a study was conducted for seven years to evaluate the effects of different rainwater conservation techniques (RCTs) on runoff, soil and nutrients losses and yield of citrus orchard in Vertisols under a sub-humid tropical climate of central India. The RCTs: staggered trench (ST) and continuous trench (CT) with and without grass mulch (GM) were imposed in runoff plots (350m2 area) with 14 citrus plants across the slope (12%) and their performances were compared with without conservation measure (WCM) treatment. All the RCTs were effective in conserving rainwater, soil and nutrients (N, P, K, Fe, Mn, Cu and Zn), which imparted a favourable response on vegetative growth, leaf nutrient content, fruit yield and fruit quality of citrus plants. However, CT+GM produced the best response, conserving 49% runoff and 51% soil compared with WCM in the orchard. The available nutrients and organic carbon content in soil were significantly improved in mulched plots. The runoff generated made linear relations (R2=0.82–0.91) with rainfall amount in treated plots, whereas this relationship was exponential (R2=0.89) in WCM plot. However, the quantity of runoff made the linear relations with soil loss in both treated plots (R2=0.76–0.89) and WCM (R2=0.93). The rates of transpiration, photosynthesis and stomatal conductance of leaf and leaf water use efficiency of the citrus plants were higher under higher available SWC in CT+GM. The CT+GM produced 65% higher fruit yield with better quality fruits (higher juice content, TSS and ascorbic acid content with lower acidity) using 32% less irrigation water, resulting in 65% improvement in rainwater productivity and 143% improvement in irrigation water productivity compared with WCM. Citrus production with CT+GM was also found economically superior to other treatments, generating more annual net income (INR 125480ha−1) with higher benefit-cost ratio (3.1). Overall results of this study demonstrates that the conjunctive use of CT and GM could conserve substantial rainfall runoff, soil and nutrients, resulting higher yield and water productivity using less irrigation water in citrus orchard in clay soil.