Grain Yield and Individual Kernel Weight As Affected by Nitrogen and Sulfur Addition In Two Maize Hybrids In the Argentinean Pampas.

A deficient supply of nitrogen (N) and sulphur (S) may affect maize yield, N uptake and kernel composition, since both nutrients are closely related in plant metabolism. Individual kernel weight not only affects grain yield, but also grain quality. Reduced N availability during grain filling affects kernel weight. Since S has low mobility in the plant, it may constrain kernel weight if not fully available during grain filling; however this issue was not fully explored in literature. The objective of this work was to evaluate different N and S fertilization timing on grain yield and individual kernel weight in two maize hybrids with contrasting yield potential and grain quality (a Flint and a semident maize type). A field experiment was conducted at INTA Oliveros Research Station (32 33’S, 60 51’W), in the Pampas region of Argentina in 2009. In order to avoid N deficiency, the experiment was fertilized with a base N rate (162 kg N ha^-1, summing N in soil at planting plus fertilizer). In both genotypes, S treatments consisted in two S fertilizer levels (0 and 20 kg S ha^-1 as calcium sulphate), applied 100% at planting (Pl), 50% Pl- 50% at tasseling (VT) and 100% at VT. In all treatments, two late N fertilizer rates were tested (0 and 50 kg N ha^-1 applied at VT). At harvest, grain yield, kernel number, individual kernel weight and test weight were determined. As expected, the semident hybrid showed higher yield than the Flint type hybrid (12290 vs 10343 kg ha^-1, respectively), and no interaction with N or S addition was detected. Additional N applied at VT increased grain yield by 820 kg.ha^-1 (7.5% increase), but no response to S fertilization was observed. However, individual kernel weight showed a significant 2.6% increase due to S addition and a 4.4% increase in response to N fertilization at VT. No differences were observed among S fertilization moments. These results suggest that early S supply is sufficient for increasing individual kernel weight, even when it is not reflected in final grain yield.