Irrigation and nitrogen source management for improving NUE in intensive Mediterranean horticulture

This study evaluates two strategies aimed to increase NUE in intensive Mediterranean horticulture: i) the precise adjustment of crop irrigation requirements to cover the losses by transpiration and evaporation from the soil, and ii) replacement of N source, from the highly leachable nitrate to ammonium, which is also directly used by the plant, and retained in the clay-humus complex. Two field experiments, with endive and muskmelon, were carried out in order to compare three treatments; i) irrigation and N management according to the farmer's criterion (F), ii) precision irrigation management with N according to the farmer's criterion (RA), and iii) precision irrigation management switching nitrate (N-NO3-), which is the fertiliser the farmer uses preferably, for ammonium (N-NH4+) [RA (Am)]. Plant water and nitrogen consumption, biomass production and yield, mineral tissue concentration, and nitrate and ammonium concentrations at 25-30 cm depth of soil were measured. The results indicate that precision irrigation alone or in combination with nitrogen source management can be used as a strategy to increase NUE, as long as the crop tolerance to ammonium is taken into account.