Optimising Water Footprint in a Dalbergia sissoo-Rice Agroforestry System through Tree Pruning Intensity

Abstract

This study aimed to quantify the green, blue, grey and total water footprints of an 18-year-old Dalbergia sissoo–rice agroforestry system under four tree pruning intensities in a semi-arid region of central India. A field trial was conducted to investigate the outcome of different pruning levels of Dalbergia sissoo on water footprint under a silviculture-based agroforestry system at Jawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur, Madhya Pradesh, India. Rice (Oryza sativa) was grown in association with 18-year-old Dalbergia trees, which were planted in a strip plot design with five replications. The four pruning levels, i.e. 0% (no pruning as control), 25% (light), 50% (moderate) and 75% (heavy) of total tree height, were applied. Seasonal crop and tree water use were estimated using the CROPWAT model based on the FAO Penman–Monteith approach, and combined tree–crop outputs were expressed as paddy grain production equivalent yield (PEY) using prevailing local market prices. Paddy grain yield, paddy stubble, big-size timber, small-size timber and fuel wood were converted to a common PEY to evaluate system-level water productivity. Green, blue, grey and total water footprint were derived under four levels of pruning. Water footprint was expressed as the volume of water (m3) required to produce one kg of paddy equivalent yield. The total water footprint of 25% pruning (1.754 m3 kg-1) was significantly lower than 50% pruning (2.497 m3 kg-1), 75% pruning (2.691 m3 kg-1) and 0% pruning (3.156 m3 kg-1). The water used to produce one kg of paddy equivalent yield was only 1754 litres in 25% pruning as compared to 2497 litres (50%), 2691 litres (75%) and 3156 litres (0%). The green, blue and grey water footprint was also lowest for 25% pruning. Total water use was statistically similar across pruning intensities (p > 0.05), and the observed differences in green, blue, grey and total water footprints therefore arose primarily from changes in PEY rather than from changes in water consumption. Among the four pruning intensities, 25% pruning emerged as the most water-efficient option, achieving the lowest total water footprint while maintaining a high paddy grain production equivalent yield.