Influence of nitrogen fertilizer on grain yield of barley (Hordeum vulgare L.) under irrigated conditions

A field study was conducted from 1998 to 2000 in Ciudad Real (Spain) to analyze the productive response of thebarley (Hordeum vulgare L.) crop to different nitrogen-fertilizer strategies. The effect of N dose and its partitioningbetween sowing-time and top-dressing at tillering state on grain yield and yield components was evaluated, as well asthe contribution of each one of these parameters to the final yield by means of a correlation and regression study, andpath coefficient analysis. The specific climatic conditions of each growing season had a very marked effect on barleycrops, and grain yields and yield components significantly differed every year. No significant differences in yieldwere found between 100 and 150 kg N ha-1 doses, but yield was significantly reduced by applying 200 kg N ha-1. Theevolution of grain yield according to N fertilizer was properly fitted to a quadratic function, with the maximum valuecorresponding to about 120 kg N ha-1. It is not advisable to exceed this dose because this is of no benefit to the plantand implies a risk of environmental contamination. The highest yield was obtained by applying two thirds of the totalN fertilizer at seeding time, whereas a single application of N fertilizer as a top-dressing resulted in a significantreduction in barley grain yield. In these field conditions, grain yield mainly depended on the number of ears per squaremeter, being the 1000-kernel weight the most stable yield component.