| Popis: |
Maize was sown at 7.4, 12.4 and 17.3 seeds m-2 every 4 weeks for 12 months. The higher seeding rates gave similar yields; the low seeding rate frequently reduced yield. Dry matter yields of forage at the soft dough stage ranged from 200 g m-2 for crops planted in June to about 1400 g m-2 for crops planted between September and January. Grain yields followed a seasonal pattern similar to forage yields, with oven dry weights exceeding 800 g m-2 for crops sown between August and January inclusive. Crops sown in winter gave low yields because there were few surviving plants, few grains per cob and the grains were small. Crops sown later than February were killed by frost before maturity. Closer spacing resulted in small cobs with a few and smaller grains. Phenological phase lengths varied with planting time and could be estimated from the inverse of mean temperatures above a critical base as the predictor variable. It is concluded that the planting season for high production of maize on the Swan Coastal Plain extends from August to January and that two crops for silage, or one for grain and one for silage, could be grown in one year. |
