August 13, 2012

Nutrient removal and loss of ground cover need to be considered when estimating the cost of harvesting drought-affected immature corn for silage.

Removed nutrients need to be replaced with applied fertilizer unless the soil has adequate capacity to supply the nutrients. This is often the case for potassium, magnesium, and sulfur. The nitrogen removed in silage is of little value if the 2013 crop will be soybean.

Table 1 estimates nutrient concentrations and lb/ton fertilizer nutrient equivalent, on a dry weight basis, for corn with no grain on the ear and for corn with the ear normally developed and filled. Silage with intermediate amounts of grain, for example 25% grain, is expected to have intermediate nutrient concentrations. Nutrient removal amounts can be adjusted to silage on an as-it-is water content by multiplying the tabular nutrient content (lb/ton) by the estimated dry matter content of the silage. For example, if the silage is 60% water and 40% dry matter, the estimated N content of the immature corn silage without grain on the ear = 30 X 0.4 = 12 lb/ton. (See Using a Microwave Oven to Test Moisture Content of Forage.)

Silage harvest leaves the soil bare, which will increase evaporation and often increase runoff until the ground is covered by the 2013 crop. The increased evaporation could be 1-4 inches, depending on the amount of precipitation and nature of rainfall events occurring between now and next June. Evaporative losses will be greater from frequent, small events compared with fewer but larger events.

The bare soil also will be susceptible to water and wind erosion, and will have minimal capacity for trapping snow. Harvest of silage may remove the field from compliance with NRCS programs. See NebGuide G1846, Harvesting Crop Residues, for more information relevant to silage harvest.

Charles Wortmann
Extension Soil Nutrient Management Specialist
Bruce Anderson
Extension Forage Specialist