S.C. Fransen
Washington State University, Prosser, Washington
The yield of corn silage in our trials ranged from 15.8 t/ha (7.0 T/ac) with 20.7% dry matter content at the early dent stage to 25.2 t/ha (11.2 t/ac) with 34.8% dry matter at ½ milk-line stage (Table 1). If the crop were to remain in the field longer, harvestable yields would probably decline because of leaf senescence and drop, stalk breakage, lodging and pest damage. Silage corn yield is a sum of its 3 yield components: ears, stalks and leaves. Whole-plant dry matter content is highly related to corn ear maturity, since stalks and leaves retain high concentrations of plant moisture. With increasing crop maturity, the percentage of ears increase and stalks decrease, but the rate of this change declines from dent to 1/2 milk-line. Although stalk and leaf percentages decrease with advancing crop maturity, the ratio of leaves to stalks increases with maturity. Nevertheless, percentage of stalks remains proportionally higher than percentage of leaves. Leaf percentage remains similar after the crop reached the dent stage of growth. The average silage corn plant produces about 20 leaves, but they range from 12 to 25 leaves.
In our trials, digestibility of whole plant silage corn increased slightly after the crop reached the early dent stage (Table 1). Whole plant digestibility was generally related to the percentage of ears. Starch percentage followed the same pattern as total grain per acre. Crude protein percentage decreased as the crop matured, due to increasing ear percentage. Percent ash also decreased with advancing crop maturity. Three important minerals within the ash component are sulphur, phosphorus and potassium. Concentration of potassium declined more rapidly with maturity than sulphur or phosphorus.
Table 1. Change of yield, yield components and nutritional parameters with advancing maturity of irrigated corn in the Pacific Northwest (based on 64 hybrids, 4 years and 2 locations).
