The cornerstone of profitable crop production is a sound soil fertility program. Such programs require forethought and planning. One of the most useful tools farmers can use in soil fertility planning is soil testing. Planning a fertility program without soil test data is largely guesswork. Other factors to consider in planning an efficient fertility program are fertilizer rates of application, placement and timing.
Nitrogen in wheat production
Nitrogen performs many vital functions in the wheat plant. Wheat requires 2 to 2.5 pounds of nitrogen (N) per bushel (bu) of grain, or, if grazed, 1 pound per acre or each 3 pound-per-acre animal gain. Shortages of N may cause reduced tillering, reduction in head size, poor grain fill and low protein content. Adequate N must be available to the wheat plant at all phases of development. Splitting N applications generally improves use efficiency, minimizes risk to investment and safeguards the environment. Growers should make their top-dress applications early, prior to jointing, to maximize production efficiency. Timing, placement and nitrogen source should be managed to fit climatic conditions, soil type and tillage system.
Phosphorus in wheat production
Fertilizer and crop prices are at much higher levels than in recent years. Adequate phosphorus (P) fertility is associated with increased tillering and grain head numbers, reduced winter-killing, maximum water-use efficiency, hastened maturity, and lower grain moisture at harvest. Winter wheat requires about 0.6 to 0.7 lpounds of phosphorus pentoxide (P₂O₅) per bushel grain. Because P is relatively immobile in soils, banded or starter applications are often most effective in soils testing low to medium. Even in high-testing soils, starter applications help plants establish more quickly. Banded P also helps young plants overcome the adverse effects of soil acidity. Broadcast P should be incorporated to improve positional availability. Finally, remember that adequate P increases N recovery and use efficiency. The effect of balanced fertility and its impact on nutrient use efficiency is especially important in today’s environment.
Potassium in wheat production
Potassium (K) in wheat production is associated with increased moisture and N use efficiency, and decreased incidence of disease and lodging. The requirement for (K) is approximately equal to that of N. Placement of K is not as critical as P since it’s more mobile in soils. Split applications should be made on deep sandy soils in high-rainfall areas to increase use efficiency.
Don’t overlook the importance of secondary and micronutrients on wheat. For example, sulfur deficiency creates problems in some areas. Base your applications of these nutrients on field history, soil tests and plant analysis.
Profitable and efficient wheat production involves supplying adequate amounts of plant nutrients when and where the crop needs them. Fertilizer application rates are of little value if nutrients aren’t in the proper place at the proper time. Effective fertility management strategies vary from region to region, but a characteristic of all good soil fertility management programs is early planning.
Source: Dr. W.M. (Mike) Stewart, Southern and Central Great Plains Director, International Plant Nutrition Institute (IPNI).