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Planning your crop’s fertility begins with soil testing, followed by planning your fertilizer application, followed by summer tissue testing. Some nutrients will go on in the fall, others in the spring and the rest in the summer, depending on you and your agronomist’s approach to nutrient management.
A summer nutrition program should include checking for available nitrates (especially if it was wet during the spring) following your planned sidedress or topdress program, tissue testing to check for deficiencies and possibly applying a foliar program.
Crop nutrition begins by having a good baseline fertility. Agronomists and growers clearly recognize this begins with routine soil testing that reports levels of nutrients, pH, organic matter and base saturation.
Crops require 16 nutrients in varying amounts. Primary macronutrients include nitrogen (N), phosphorus (P) and potassium (K); secondary macros include calcium, magnesium and sulfur; and finally, micronutrients include zinc, manganese, iron, copper and boron. Sometimes chloride, molybdenum and nickel are added to this list.
Macronutrients are required in large amounts and have to be taken up by crop roots from the soil. For example, 200-bushel corn (grain and stover) requires more than 200 pounds N, 102 pounds P and 270 pounds K, and 65-bushel soybeans (grain and stover) require over 300 pounds N, 63 pounds P and 142 pounds K.
There is no way to provide these amounts by foliar feeding. While micronutrients are required in small amounts, their concentration in the soil is small and their availability is often limited…