Effects of timing, intensity and duration of pollination on kernel set and yield in maize (Zea mays L.) under temperate conditions.

Abstract

Pollen shedding and silking of maize can be desynchronized, which may result in poor grain set. In four field experiments the timing, intensity and duration of pollination was influenced by different types of ear-covering treatments, under ecological conditions in which desynchro-nization is small. The pollen production already reached a maximum after a few days after the onset of anthesis. After 8-10 days, 99 % of the pollen was already shed. Tassel treatments hardly affected the grain set, probably because there was ample lateral transport of pollen. Apparently, silks are already receptive directly after extrusion. Covering the ears on different moments after the onset of anthesis resulted in reduced kernel set. This effect was stronger when the covering was earlier, but the effect was also modified by plant density and the environmental conditions. In two experiments, 5-6 days of pollination were sufficient to obtain a maximum grain set. In other experiments, the maximum grain set required a longer period of pollination. In the uncovering treatments the pollination was delayed and therefore more silks were exposed to pollen at the same time. A long delay of silk exposure inhibited grain set because of a lack of pollen and a reduced functionality of silks. In one experiment, a short delay of pollination slightly increased the number of kernels per ear, because of a positive effect on the grain set in the top of the ear. A long delay in pollination affected the distribution of dry matter over the ear, even when it did not reduce overall grain set. There was a strong relation between the proportion of grain set and the ear yield in all experiments. Only in one experiment, the maximum ear yield could already be obtained with a significantly reduced grain set. Under Dutch conditions, pollen is usually abundantly available for a proper grain set. Only in the upper part of the ear, grain set can be limited by lack of pollen. The silks remain functional for such a long time, that their receptiveness is not limiting either.