UNL CropWatch July 16, 2010: The Importance of Soil Testing for the 2011 Winter Wheat Crop
July 16, 2010
Wheat harvest is progressing across Nebraska and it’s time to start thinking about next year’s fertilizer needs. With adequate moisture in most of the wheat producing areas across the state, yield potential for next year’s crop should be good.
Fertilizer and wheat prices have undergone major changes in the past couple years. Adequate spring moisture has produced high yields in many parts of Nebraska, but with high fertilizer prices, many producers decreased nitrogen applications last year, resulting in lower protein content in some wheat. Now some elevators are paying premiums for higher protein content.
Wheat prices have rebounded some in the last few weeks, so producers should calculate projected yields and selling prices. Knowing fertilizer prices plus soil test levels helps to plan accordingly.
World Nitrogen Supply
Nitrogen prices have finally leveled off and declined to levels last seen back in 2006 (Figure 1). These are urea prices averaged over several sources and calculated weekly, giving equal weight to prices published by major trade publications for granular urea FOB vessels from the Middle East, Southeast Asia, the U.S. Gulf, and Latin America.
World demand for fertilizer decreased during the economic crisis, so there has been excess fertilizer. There is some indication that some major manufacturers in Russia are cutting production, which could increase prices later. Fertilizer prices f.o.b. the U.S. Gulf are under $280/ton and ammonia f.o.b. for the Corn Belt is now near $320 per ton.
Soil testing is the best way to determine fertilizer requirements for wheat. Because soil nitrate is mobile, soil samples should be taken to at least a three-foot depth before each wheat crop. (See the UNL NebGuide, Guidelines for Soil Sampling, for further information.)
Soil samples for pH, phosphorus, potassium, and micronutrients should be done every three to five years as these values do not change rapidly even with fertilization. The topsoil sample should be taken from the zero to eight- inch depth.
When calculating nitrogen and phosphorus recommendations for wheat, information from your soil tests plus fertilizer prices and the expected selling price are included (see Fertilizing Winter Wheat, EC143). Fertilizer prices should be lower than last year and wheat prices are ranging from $3.50 to $4.00 at local elevators and higher on the Kansas City and Chicago markets. Based on current prices for nitrogen and wheat, nitrogen application is still profitable (Table 1).
Phosphorus prices for 18-46-0 (DAP) more than quadrupled before falling back to 2006 levels (Figure 2).
Applying phosphate is also still profitable. Nebraska data shows up to a 20 bu/ac increase when applying P for low soil test P and up to 10 bu/ac increases when applying to medium P soils. The most profitable P rate depends on
- the P source used,
- wheat and fertilizer prices,
- soil pH and
- the method of application.
Row or dual-applied P is more efficient than broadcast applications. Newer ammonia applicators with coulters allow narrower application (15 inches) and also operate at shallower depths (5 to 7 inches), greatly reducing power requirements. This has been a standard practice with older knife (dual) placement which has been around for 20 years. Dual-applied P and seed-applied P perform equally well at optimum seeding dates.
Taking soil samples now can be the first step in producing a profitable and quality crop for 2011.
Extension Nutrient Management Specialist, Panhandle REC, Scottsbluff
Extension Nutrient Management Specialist, West Central REC, North Platte