Prediction of Dry Matter Yield of Hybrid Forage Corn Grown for Silage

Predicting yield at an early growth stage will allow producers to optimize the amount and timing of N to maximize crop yield. The objective of this study was to evaluate the usefulness of individual measurements and combinations of normalized difference vegetation index (NDVI) and plant height (PH) as early stage predictors of corn (Zea mays L.) dry matter (DM) yield for silage. Corn was grown during 2 yr in Camden, Australia with different rates of pre-and post-sown N fertilizer, with or without irrigation, and harvested for silage at physiological maturity. In both years, NDVI and PH data were collected at 3-, 5-, 6- and 8-leaf stages (V) and their relative values were calculated by using the reference treatment (nonlimiting N and water). In contrast to the actual data, the relative DM yield data in both years settled on the same regression line against relative NDVI indicating that expressing DM yield and NDVI in relative terms reduces the variation due to year and may be more useful than the actual values for prediction purposes. The accuracy of prediction was higher for PH than NDVI data. However, the best accuracy in DM yield prediction at V6 stage was obtained with combinations of relative PH x NDVI (r(2) >= 0.78). As slopes of all indicators were similar in stages from V6 to V8 stages, all indicators may be used to predict DM yield of forage corn grown for silage as early as V6 stage. Plant height and PH x NDVI can be used to predict DM yield of forage corn at V5 stage because slopes of these indicators were similar from V5 to V8 stages.