Grain yield components in maize: I. Ear growth and kernel set

Abstract

Maize ( Zea mays, L) grain yield is correlated with kernel number (KN), but uncertainty exists about the extension of the critical period for kernel set. In this work, the actual period of active ear elongation was determined and defined in thermal units (°C day=degree days). Kernel number was related to the amount of intercepted photosynthetically active radiation (IPAR) during this period. Field experiments were conducted in France (48°51′N) and Argentina (32 to 37°S). Different sowing dates and plant populations were used to vary the amount of IPAR plant −1. Hybrids of different cycle length (FAO maturity ranking between 300 and 630) were tested. Ear length was measured weekly after axillary bud differentiation, and values were normalized to final ear length. A significant linear model ( r 2=0.92, n=51) was fitted, which indicated that: (i) Active ear elongation took place between −227 and 100°C day from silking; (ii) ca. 41% of final ear length was reached at silking; (iii) Ear elongation rate increased after silking; and (iv) The duration of this period varied among sites and treatments. Kernel number plant −1 was significantly related to the IPAR plant −1 during the critical period ( r 2=0.70, n=81), but a significant ( P<0.01) difference was detected between the prolific and nonprolific groups. The presilking environment seemed to define the potential number of kernels that will be set as well as subapical ear fertility, but the effectively fixed KN depended upon postsilking conditions and hybrid characteristics such as prolificacy and ear size.