Rates and timing of nitrogen fertilizer application on yield, nutritive value and nutrient-use efficiency of early- and late-sown forage maize.

摘要

The outcomes of previous studies have resulted in differing recommendations on the rate and timing of fertilizer N applications for forage maize. In order to gain an improved understanding of the role of N fertilizer, a field experiment was carried out to investigate the effects of time and rate of N application on total and plant-fraction yield, nutritive value and efficiency of nutrient utilization in early- and late-sown forage maize. Treatments included two sowing dates (early, late), two rates of N (0, 135 kg ha-1) applied pre-sowing (N1) and three rates of N (0, 79, 158 kg ha-1) applied post-sowing (N2) at the six-leaf stage (V6). Application of N at N1 (N0 vs. N135) increased dry-matter (DM) stover yield by 11% and total yield by 7%. Application of fertilizer N at N2 (N0 vs. N158) increased grain yield by 44% and total yield by 34%. Application of N2 also increased irrigation and total water-use efficiency (WUE) from 30 to 40 and 46 to 61 kg DM ML-1 water respectively. Late sowing increased DM yield by 6%, but decreased WUE compared with early sowing. The results indicate that application of N at both N1 and N2 is essential to maximize total DM yield from forage maize, but application at V6 is recommended when N input is reduced.