Quantifying and reducing the water footprint of rain-fed potato production part II: a hydrological assessment using modelling supported by measurements

Abstract

Abstract Water footprinting (WF) is mooted to quantify the impacts of production on water resources. The impact of the rain-fed potato ( Solanum tuberosum) production on water resources was assessed for a kilogram of potatoes at the packhouse gate. The hydrological water-balance method was used and this accounts for all inflows and outflows to quantify the net use of groundwater as the blue WF, and that of the soil-water store as the green WF. The green WF was found to be negligible. The blue WF was negative at −67 L/kg. Thus rain-fed potato production here has no deleterious impacts on the water quantity. The grey WF, the water required to ‘dilute’ NO 3 –N in the drainage to meet the drinking water standard, was 61 L/kg, of which 56 L/kg was from the cropping stage. The impact of the packhouse phase and the background system was found to be small. However, the average leached NO 3 –N concentration of 11.3 mg/L, which is just at the drinking water standard, and the loading of 27.8 kg-N/ha/y during cultivation indicate that a single application of fertilizer at the time of planting has impacts on water quality. Our modelling of different fertilizer application scenarios of two splits, three splits and a late application at 55 days after planting reduced the annual average NO 3 –N concentrations to 10.5, 10.3 and 9.5 mg/L respectively. Potato yield was not compromised. The grey WF would be reduced to 50.6, 50.9 and 48.9 L/kg respectively for these fertilizer scenarios.