Planting date and hybrid influence on corn forage yield and quality

Producers believe that corn (Zea mays L.) forage can be planted at later dates than corn grain because forage harvest does not have to wait until the grain matures fully. The objectives of this study were to determine relationships between planting date and corn forage yield and quality and to determine optimum planting dates of corn forage for the state of Wisconsin. Full- and shorter-season hybrids were planted on six dates at six locations in Wisconsin during 1998 and 1999. Few significant hybrid X planting date interactions or hybrid differences were observed. The optimum planting dates for dry matter yield and quality for southern, central, and northern Wisconsin were 10 May, 27 April, and 8 May, respectively. Corn forage yields remained at 95% of maximum yields when corn was planted in late May for all zones. In all zones, early June plantings exhibited an accelerated rate of yield decline of 0.2 Mg ha(-1) d(-1) delay in planting. Corn forage quality decreased progressively as planting dates progressed into June. The optimum planting date for milk yield ha(-1) was 2 May in southern and central zones and late April in the northern zone. As planting was delayed past mid-May, rates of quality decline were more severe in central and northern zones compared with the southern zone. Therefore, planting of corn forage should occur between late April and mid-May for all production zones in Wisconsin, but planting could occur into late May in the southern production zone because milk yield ha(-1) declined by only 8%.