Soil Sampling and Testing for the 2012 Winter Wheat Crop - UNL CropWatch, July 21, 2011

Soil Sampling and Testing for the 2012 Winter Wheat Crop - UNL CropWatch, July 21, 2011

July 21, 2011

Wheat harvest is nearing completion in eastern Nebraska, but just getting underway in the west. Many of the wheat-fallow production areas have had good precipitation, setting the stage for good yield potential for next year’s crop with sound fertilizer management. Wheat prices have rebounded in the last few weeks, but fertilizer prices have continued to climb since the beginning of the year.

Given these economic factors, producers must calculate projected yields, selling prices, and fertilizer prices and plan accordingly. One of the first steps is soil testing.

Soil Sampling and Testing

Soil sampling and testing are essential to determine fertilizer requirements for a profitable wheat crop. For information on how to get the most accurate samples, see the NebGuide, Guidelines for Soil Sampling. The most important nutrients for winter wheat production are phosphorus and nitrogen.

Soil samples for pH, phosphorus, potassium, and micronutrients should be done every three to four years as these values do not change rapidly even with fertilization. The topsoil sample should be from the 0- to 8-inch depth.

Soil samples for soil nitrate should be taken one to three months before planting each wheat crop. In most dryland or rainfed wheat production areas, wheat will root to a 5-foot depth with a full profile of soil water. This should be the case for the 2012 crop in much of western Nebraska due to above normal rainfall this spring and early summer. Soil samples should be taken from the surface depth and at every foot to at least a 3- or 4-foot depth and analyzed for nitrate-N. The results will help you fine-tune your N fertilizer recommendations.

Nitrogen Fertilizer Prices

Nitrogen prices have continued to climb since last summer (Figure 1). Prices for urea in Figure 1 are averaged over several sources and 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.

nitrogen prices

Figure 1. World urea prices from June 2001 to July 15, 2011. (Links to larger version. Source: Fertilizerworks.com; Basket Price)


World demand for fertilizer has increased and with some plant shutdowns for maintenance, prices have been climbing. There is some indication that prices will not decrease as they often do in mid summer. U.S. Gulf prices for urea are steady around $467 per ton and ammonia in the Corn Belt is now retailing at over $800 per ton.

Weighing Costs and Nutrient Needs

Information from your soil tests plus fertilizer prices and expected selling price for your wheat are used in the calculation of both nitrogen and phosphorus recommendations (see Fertilizing Winter Wheat, EC143). Current nitrogen fertilizer prices (ammonia lower cost, urea or UAN higher) are ranging from $0.50 to 0.70 per pound of N. Wheat prices range from $7 (local cash basis) to near $8 in Kansas City. Because prices fluctuate, a range of fertilizer and wheat prices are combined with residual soil nitrate levels for N recommendations. Applying N is still profitable based on a range of current prices for wheat and nitrogen (Table 1).

Table 1.  Nitrogen fertilizer recommendations for dryland wheat when N is $0.50 or $0.70 per pound and wheat is $7 or $8 per bushel.

Residual Nitrate

Wheat price - $7/bu

Wheat price - $8/bu

Average ppm nitrate-N
in a 3-foot depth

N = $0.50/lb

N = $0.70/lb

N = $0.50/lb

N = $0.70/lb

2

95

75

100

85

4

75

55

85

65

6

55

35

60

45

8

35

15

40

20

10

15

0

20

0

Phosphorus

Phosphorus price trend

Phosphorus prices for 18-46-0 (DAP) from January 2008 through 2011.

Phosphorus prices for 18-46-0 (DAP) have climbed since last year and increased significantly during the past week (Figure 2), now costing over $700 per ton. Ammonium polyphosphate (10-34-0) prices per pound of phosphorus have been similar to dry.

Applying phosphate is also profitable. Nebraska data shows up to 20 bu/ac increases to applied P at low soil test P and up to 10 bu/ac increases for medium P soils. The P rate depends on P source used, wheat and fertilizer prices, soil pH and the method of application (see EC143). 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) greatly reducing power requirements. This has been a standard practice with older knife (dual) placement which has been around for 25 years. Dual-applied P and seed-applied P perform equally at optimum seeding dates.

Taking soil samples now can be the first step to producing a profitable and quality crop for 2012.

Gary Hergert
Extension Soils Specialist, Panhandle REC, Scottsbluff