| dc.description.abstract | Current methods for determining midseason nitrogen (N) rates in corn have used normalized difference vegetation index (NDVI), and in some cases, plant height and intra-specific plant competition. Another parameter that can be linked to potential yield is stalk diameter; thus incorporating collectively the parameters of NDVI, plant height, and stalk diameter should result in a better prediction of yield potential. This could lead to more efficient methods for midseason fertilizer N applications. The objective of this study was to analyze the relationship of stalk diameter, as well as plant height and NDVI, with final grain yield, and to refine the method of predicting yield potential using a combination of these factors. In this 2-year study at 4 locations, we selected several rows of corn plants, each with varying amounts of pre-plant nitrogen fertilizer, from 0 to 145 kg ha-1, and where no additional nitrogen was applied throughout the growing season. Measurements of plant spacing, stalk diameter, plant height, and NDVI were taken from growth stages V8 (eight fully collared leaves) to VT (corn tasselling), and all corn plants were harvested by-plant to determine grain yield or dry biomass. Individual plant height measurements proved to be a good predictor of by-plant grain yield (r2 = 0.52, 0.53; V10, V12, respectively). Using a value of stalk diameter X plant height gave the best correlation with grain yield (r2 = 0.34, 0.55, 0.67; V8, V10, V12, respectively). By-plant biomass was also highly correlated with stalk diameter, with an r2 of 0.68 at growth stage V15, using a polynomial function. This work showed that stalk diameter X plant height was highly correlated with by-plant corn grain yields, and this parameter could possibly be used for refining midseason fertilizer N rates from growth stages V8 to V12. | |
