July 24, 2009

Soil Testing for the 2010 Winter Wheat Crop

Wheat harvest is complete in most of the state except the Panhandle and it’s time to start thinking abut next year’s fertilizer needs. With adequate moisture in much of the fallow areas in Nebraska, yield potential for next year’s crop should be good.

The past couple of years have seen major changes in fertilizer and wheat prices. Adequate spring moisture has produced high yields in many parts of Nebraska, but because many producers decreased nitrogen applications due to high prices last year and this spring, protein content is lower in some areas. World fertilizer prices have been on a roller coaster ride, but prices should be lower this fall and winter.

Nitrogen

Nitrogen prices tripled compared to what they were two years ago but now have declined to levels seen in 2006 (Figure 1). These are urea prices averaged over several sources calculated weekly giving equal weighting to prices published by major trade publications for granular urea FOB vessel from the Middle East, Southeast Asia, the U.S. Gulf, and Latin America.

Figure 1. World urea prices May 1999 to July 17, 2009. (Source: Fertilizerworks.com; Basket Price)

World demand for fertilizer increased 14% during the previous five years (primarily due to sales to South America, China, and India), but demand subsided with the beginning of the worldwide recession last fall. Some U.S. dealers bought high last summer and had to take losses to meet competition from broker deals last winter. They should be able to buy much lower cost nitrogen this year and pass the savings on to producers. Urea prices f.o.b. the U.S. Gulf are under $280/ton and ammonia delivered to the Corn Belt is now near $320 per ton.

This year has produced rainfall extremes across Nebraska. Parts of eastern Nebraska are drier than normal. Rainfall in the Panhandle is above normal, finally breaking the last eight years of drought. Because soil nitrate is mobile, soil tests should be taken to at least a three-foot depth. Nitrate should be sampled before each wheat crop.

Soil testing is the best way to determine fertilizer requirements for wheat. (See UNL NebGuide, Guidelines for Soil Sampling, G1740, for procedures and recommendaitons.) 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 from the 0- to 8-inch depth.

Fertilizer prices, expected crop prices, and soil test results are used to calculate your nitrogen and phosphorus recommendations. Fertilizer prices should be lower and wheat prices are definitely lower than last year, but applying nitrogen is still profitable based on a range of current prices for wheat and nitrogen (Table 1).

Phosphorus

Figure 2. Phosphate prices fob Tampa, Florida from January 2006 to now. (Source: Green Market Fertilizer)

Phosphorus prices for 18-46-0 (DAP) more than quadrupled before falling back to 2006 levels this spring (Figure 2).

Applying phosphate is also still profitable. Nebraska data shows yield increases of up to 20 bu/ac with applications to low soil test P and up to 10 bu/ac increases for medium P soils. The most profitable P rate depends on:

• the P source used,
• wheat and fertilizer prices,
• soil pH, and
• the application method.

Row or dual-applied P is a more efficient method of P application than broadcast.

Newer ammonia applicators with coulters allow narrower application (15 inches) and also operate at shallower depths (5 to 7 inches). This greatly reduces power requirements and has been a standard practice with older knife (dual) placement for 20 years. Dual-applied P and seed-applied P perform equally at optimum seeding dates.

Taking soil samples now can be the first step in producing a profitable and quality crop for 2010.

Gary Hergert
Extension Soils Specialist, Panhandle REC, Scottsbluff