The effect of nitrogen applications on the growth of young olive trees and nitrogen use efficiency

Abstract

Two field trials (FieldExp1 and FieldExp2) and a pot experiment (PotExp) were c0onducted over a period of 3 years to assessolive tree response to nitrogen (N) applications and to estimate apparent N recovery. FieldExp1 was installed in a 3-year-old olive grove.FieldExp2 consisted of a plantation of young rooted plants. Two treatments were applied in both experiments: N application and anonfertilized control. In PotExp, 4 N rates were used. In FieldExp1, olive yield significantly increased with applied N in only 1 of the3 growing seasons. In FieldExp2, aboveground dry matter yield significantly increased with N application. In PotExp, total dry matteryield displayed a typical saturation curve in response to N rates. The poor response of olive yield to N application might be due to thereduced amount of N removed in the crop, and also to the negative interaction found between N application and water deficit. ApparentN recovery reached values varying from 13.1% in FieldExp2 to ~100% in PotExp. The results indicate that the olive response to N and Nuse efficiency seem to be influenced more by the agroecological conditions defining target yield and N loss, rather than by plant species.