YIELD, QUALITY AND DEVELOPMENT OF FORAGE MAIZE AS INFLUENCED BY DATES OF PLANTING AND HARVESTING

The effects of dates of planting and harvesting on yield, quality and development of forage maize were investigated in a 3-yr study. Treatments studied were all possible combinations of five planting dates, spaced at 2-weekly intervals from late April to mid-June, and three harvest dates (mid-September, early and mid-October). Between early May and mid-June, each 1-day delay in seeding resulted, on average, in a 1% reduction in whole-plant digestible dry matter yield. In vitro dry matter digestibility was not significantly affected by date of harvesting but was reduced progressively from 66 to 63% as the date of planting was delayed. Although grain content varied from 0 to 50% of whole-plant dry matter, it had little effect on the in vitro digestibility of forage maize, which only ranged from 62 to 68%, when whole-plant dry matter contents were acceptable for direct ensiling. During the grain-filling period (450–1600 corn heat units after mid-silking), whole-plant dry matter content (%) was linearly related to accumulated corn heat units (r2 = 0.83***); each 1% increase in dry matter content requiring an input of 40 corn heat units. Thus, using information on the date of mid-silking and daily air temperature records (long-term or current), it is possible to predict the date (average or actual) when whole-plant DM content reaches any desired magnitude for harvesting.Key words: Quality, planting date, harvest date, maize, corn, development