Corn production and plant characteristics response to N fertilization management in dry-land conventional tillage system

Nitrogen (N) application management needs to be refined for low yielding environments under dryland conditions. This 3-yr study examined nitrogen fertilization management effects on corn (Zea mays L.) plant characteristics and grain yield in rain fed environment under conventional tillage system. Nitrogen fertilization management consisted of two timing methods of N application [all N at planting and as split with 35 kg N ha^-1 applied at planting and remaining N applied at vegetative (V)
6 growth stage] and five N rates (0, 45, 90, 135, and 180 kg N ha^-1). Insufficient rainfall at reproductive stage in 2008 and 2009 likely resulted in significant reduction of grain yield compared with grain yield in 2007, average 2.9 vs. 5.9 Mg ha^-1. Grain yield increased with N application up to 45 kg ha^-1; however, no further increase in N application resulted in increased yields. Plant height, ear height, relative chlorophyll (SPAD) content, and normalized difference vegetation index (NDVI) at reproductive (R1) stage increased with increasing N rate up to 90, 90, 135, and 90 kg N ha^-1, respectively. Corn grain yield significantly correlated with plant height at R1, SPAD at V8, NDVI and LAI at V8 and R1 stage. The combination of plant height, NDVI, and LAI of R1 stage explained most of the variability of grain yield (r-square = 0.71). The fertilization timing had no effect on corn grain yield and plant characteristics. These observations showed that applying more than 45 kg N ha^-1 to corn under dryland conditions with insufficient rainfall, especially during corn pollination, may not significantly increase grain yields.