Strategies to Improve Water and Nitrogen Use in Furrow Irrigated Systems.

Furrow irrigation is a commonly used gravity fed method for irrigation. As global demand for food increases we need to find new ways to boost the productivity of furrow irrigated agriculture while reducing associated but unwanted environmental impacts. These include rising water tables, water logging, soil salinisation, soil structural degradation, groundwater salinisation, and surface and groundwater pollution. The solutions must include a reduction in deep drainage and leaching through improved water and nutrient use. In this paper we discuss results of a simulation study carried out using the HYDRUS-2D model to analyse water flow and non-reactive solute transport in furrow irrigated systems. Analyses included different combinations of soil surface management strategies (control; compacting the bottom of the furrow; covering the bottom of the furrow with plastic) and nitrogen fertilizer placements (bottom of the furrow; sides of the furrow; top of the ridge). The greatest potential benefit was achieved by covering the bottom of the furrow with plastic to force the applied water to move horizontally into the ridge. This helped maximise the benefit of capillary forces in retaining water and nitrogen within the ridge and plant root zone, while minimising the effect of gravitational forces that pull water and nitrogen vertically downwards below the bottom of the furrow. We discuss challenges and opportunities associated with applying these approaches in developed and developing countries.