Effects of conventional and multiple N application by fertigation on maize grain yields and NO 3 − —N residues

Abstract

When nitrogen is added to irrigation water (fertigation), N applications can be done in several dressings during the growing season. With this technique, it is possible to match the N requirements of maize crop. In such case, N efficiency should be enhanced, and, lower rates of nitrogen could be applied to avoid nitrate loss through leaching. In a two year field experiment the effect of N fertigation was compared with conventional N fertilization at two N rates (170 and 220 kg N ha −1). Grain yield, total biomass, N exportation and residual soil nitrogen were recorded. There was no influence of method of application on maize yields and yield components. But, the residual soil nitrogen was higher after multiple N applications, even at the low N rate. As no leaching was recorded, and, since the N recovery by the maize crop was the same for all the treatments, the difference in residual soil nitrogen was probably due to N immobilization by the soil biomass. The nitrogen applied late in the season (at tasselling) was not immobilized as fast as side-dressed nitrogen. N fertigation at the conventional N rate increases the risk of N leaching after maize harvesting, and to apply N at lower rates may decrease grain yield. So, if nitrate leaching is a potential risk, as it is generally the case in numerous irrigated areas, because of sandy or shallow loamy soils, N fertigation is not recommended so long as the N fertilization rates cannot be calculated more accurately.