PREDICTING CORN YIELD RESPONSE TO PLANTING DATE DELAY

A two-year field study was conducted to determine the effect of delay in planting on com yield in eastern North Carolina. The relationship between yield and planting date is needed in order to quantify the effects of trafficability, as influenced by drainage system design, on yield. Corn was planted on drained and subirrigated plots at planting dates ranging from mid-March to early June. Results indicated that yield decreased with planting date delay after 10 April. Results were in general agreement with those in earlier unirrigated experiments. The relationship between relative yield, Y, and planting date delay, D (days), beyond 10 April could be described by a piecewise linear relationship: Y = 1.0 - 0.0088 D, for D < 40; and Y = 1.3 - 0.0162 D, for 40 less-than-or-equal-to D < 80. Similar relationships were derived from data published in the literature for eight other locations. Although there were differences in the threshold date beyond which yields decreased with delay in planting, the equation parameters fell within a relatively small range for most locations. These relationships can be used in the water management simulation model, DRAINMOD, to predict the effect of drainage design on planting delay and relative yield.