Timing and Splitting of Nitrogen Side-Dress Fertilization of Early Corn Hybrids for High Grain Yield
Currently, most nitrogen fertilizer is side-dressed when corn is in the four (V4) to eight (V8) expanded leaf stage. However, recent studies have shown that modern hybrids take up high amounts of nitrogen during grain filling. This indicates that a late nitrogen fertilization, at the time of crop flowering, may be important to optimize corn agronomic performance. This study aimed to evaluate the effect of the timing and splitting of nitrogen side-dress application on the agronomic performance of early corn hybrids in order to achieve high grain yield. The experiment was set in Lages, Santa Catarina, in the South of Brazil, during the 2014/2015 and 2015/2016 growing seasons. A randomized block design arranged in split plots was used. Two hybrids were tested in the main plots: P1680YH (very early) and P30F53YH (early). Six nitrogen side-dress systems were assessed in the split plots: control (without N), full N rate applied at V5, full N rate applied at V10, 1/2 N rate applied at V5 and 1/2 at V10, 1/3 N rate applied at V5, 1/3 at V10 and 1/3 at VT; and the whole N rate applied at VT. The nitrogen rate was 300 kg ha-1 N. Urea was used as the nitrogen source. Total grain yield and yield components, agronomic nitrogen use efficiency, and leaf area were determined. Grain yield ranged from 6,422 to 15,426 kg ha-1 in 2014/2015 and from 9,283 to 14,986 in 2015/2016. Nitrogen side-dress application performed one time at V5 or V10 or split into two or three applications at different growth stages had similar grain yield, number of ears per plant, kernels per ear, and 1,000 grain dry weight. Nitrogen side-dressed entirely at VT led to higher grain yield than the control. However, grain yield and agronomic nitrogen use efficiency were lower in this treatment than in the treatments involving the other growth stages of side-dress nitrogen. The early hybrid was higher yielding than the very early hybrid, regardless of the timing of nitrogen fertilization. Splitting of nitrogen fertilization up to tasseling was not an effective strategy to increase grain yield and agronomic nitrogen use efficiency of the corn hybrids P30F53YH and P1680YH.