Topics : Soil Fertility for Forage Crops : Pre-Establishment
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Phosphorus & Potassium
Forage crops have a high demand for phosphorus and potassium. Thus, it is critical that soil levels for these nutrients be built up in preparation for growing these crops. Phosphorus and potassium are relatively immobile in the soil. For example, phorphorus will move less than one-eighth of an inch in a year in soil. To bring the rooting zone of a soil up into the optimum level for crops, the phosphorus and potassium must be thoroughly mixed with the soil. Therefore, it is very important that the soil levels be built up before the perennial forage crop is established, because once the crop is established there is no way to effectively mix the phosphorus and potassium with the soil in the rooting zone.
Building low fertility soils up to high fertility without some tillage to mix the nutrients and limestone throughout the primary rooting zone of the crop is difficult. In no-till cropping systems this is an especially difficult problem because there is no opportunity for mixing. If soil fertility is low in no-till, it is suggested that at some point in the crop rotation, the recommended limestone, phosphorus, and potassium be applied and tilled into the soil to build the fertility levels. Once the soil levels are in the optimum to high range on the soil test, surface application of the limestone and the fertilizer phosphorus and potassium in a no-till system can maintain these levels.