Topics : Soil Fertility for Forage Crops : Pre-Establishment
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On farms with livestock, the manure applied to the corn will be a major contributor to meeting the phosphorus and potassium goals at establishment. When manure is applied to corn to meet the nitrogen needs of the corn, excess phosphorus and potassium will be applied. This excess phosphorus and potassium will build the soil levels, often into the high range, and can be used by a forage crop later in the rotation. When manure is not available, fertilizer must be applied to the corn to replace the nutrients removed in the corn crop and if necessary to build the soil levels into the optimum to high range before forage establishment.
Keeping records and following soil test trends can be very helpful in fine tuning the fertility program for a corn-forage rotation. This is illustrated in Figure 4. Notice the build-up during the corn part of the rotation when manure is being applied to meet a significant proportion of the nitrogen needs of the corn and a draw-down of the soil nutrient levels in the forage part of the rotation. Also notice that over time the trend in soil test levels should be relatively constant and maintained in the optimum to low high range.