|From The Field|
|From The Field|
Crop Nutrient Considerations
Commodity prices and input costs have varied dramatically over the past two years in response to unpredictable global pressures and drastic economic changes. Given little rainfall, Alabama growers have done an outstanding job shifting crops planted, adjusting management practices and staying in business while doing it. The face of agriculture in Alabama has changed and crop production in the state in 2009 will be very different from the paradigm that has prevailed for decades. Along with the cost of other inputs, growers have faced rising fertilizer prices. Profitable production now requires increased efficiency and changes in the way fertilizer has been utilized in the past. While each decision about fertilizer use depends on financial situations, prices and other economic factors, the need of each crop for adequate and balanced fertility remains constant.
Though it is tempting, growers should proceed with caution when considering cutbacks in their fertility program. Cutting corners can leave fields under-fertilized or throw critical nutrient ratios out-of-balance, limiting nutrient uptake and jeopardizing plant health and productivity. A full understanding of the total picture is necessary when considering fertilizer cut-backs. Soil tests, past yield reports, cost-of-production per acre, along with knowledge of the genetic potential of the chosen seed hybrid and the individual grower’s yield goal are all pieces of the puzzle. With that data in hand, production investments can be optimized, even in the face of fertilizer cutbacks. Growers on every level are making considerable investments in leading seed technologies and state-of-the-art crop protection technologies, not to speak of their outlay for fuel, labor, land and equipment. With such a high investment in genetics and other crop production inputs, shortchanging the fertilizer program and cutting back vital nutrients could limit yield potential before the seed is out of the bag.
Balance of Nutrients Crucial
Most growers are reluctant to cut back on nitrogen (N), because the impact is obvious – leaves turn yellow and plants simply look sickly. However, phosphorous (P) and potassium (K) are sometimes shortchanged in the name of N. In doing this, crops can be left with stunted root growth, delayed maturity of grain and less efficient use of water. When there are balanced levels of P and K available in soil, N uptake efficiency is increased. This synergy is imperative to healthy crops and good land stewardship – increased yields and reduced soil nitrate levels. Consistently, high top-end yields require not only a balanced N, P and K fertility program, but also adequate levels of sulfur (S) and zinc (Zn). Nutrient interactions between N and S, and between P and Zn, play a large role in N and P uptake efficiencies. Ultimately, all fertilizer application decisions should be made using soil test data. It’s simply the most accurate way for growers to understand their nutrient needs and build a sound program. Once crop needs are understood, cutback decisions can be made wisely, without seriously hindering yield potential.
Changing crop rotations can result in situations requiring specific nutrient management. Soybeans were planted on many acres in Alabama in 2008. It is generally accepted soybeans leave 20 to 40 pounds of N available for use by a subsequent crop. This should be considered when applying pre-plant fertilizer. In a no-till situation with large amounts of crop residue from corn or wheat, the situation is reversed. N rates need to be increased to compensate for the N immobilized by decomposing stalks or straw. K levels can be surprisingly low following certain crops or production practices. Corn silage, hay crops and baled wheat straw remove large amounts of K from a system. Soybeans also take a lot of K away from a field. Given the number of double crop wheat / soybean acres planted in Alabama this past year, careful consideration needs to be given to soil tests.
Chris Carter is Product Manager with the Agri-AFC Fertilizer Department.