AGRI-BRIEFS   AGRONOMIC NEWS ITEMS

From Agronomists of the Potash & Phosphate Institute 655 Engineering Drive, Suite 110 Norcross, Georgia 30092-2837 Phone (770) 447-0335

Fall 2000, No. 8

Soil tests provide a good measure of soil pH and nutrient status. Careful sampling is critical as variability exists in every field. Thus, site-specific nutrient management delivers nutrient needs based on (1) differing soil fertility and productivity levels, (2) yield goal expectations, and (3) supporting production practices which interact with the basic functions performed by specific fertilizer nutrients. Such a system adjusts for differences in soil productivity and provides optimum development of the crop’s yield potential for each management zone in a field.

The building blocks for high wheat yields are no mystery. The challenge comes with the readjustment of the blocks to build the best production system for each management zone in the field. Each of the following practices contributes most when properly teamed with the others, and where needed, adjusted for management zone differences.

• Site selection...identify fields that are fertile and capable of achieving high yields.

• Tillage and seedbed preparation...reduced tillage improves soil/water relations, but must provide a firm seedbed for good soil-seed contact and germination.

• Liming and adjusting soil fertility...soil test, allow applied aglime to react for about three months before planting, and adjust soil test levels for phosphorus and potassium to the high range.

• Variety selection and seeding...select performance tested varieties, plant in narrow rows and plant within the high yield window.

• Weed, insect and disease management...prevention or early detection and control of these stress factors will likely vary between management zones.

• Nutrient management...multiple applications of nitrogen, phosphorus, potassium, sulfur, and boron might be needed to insure full development of each of the three components of high yield wheat. The following example might help to illustrate timing fertility to wheat needs on productive, low cation exchange capacity soils subject to intense periods of rainfall.

• Preplant: Consider the application of about one-third of the nitrogen, all the phosphorus, and half of the potassium, sulfur, and boron needs. This promotes seedling growth and tiller development which is needed for the high yield component of heads per acre.

• Sidedress: Consider half of the remaining nitrogen and the other half of the potassium, sulfur and boron needs applied prior to early spring growth flush (Feekes 3.0). This minimizes the risk of nutrient loss by leaching and targets the yield component of seed number per head.

• Sidedress: Consider the remaining nitrogen (adjusted if needed for climatic and/or yield conditions) for the third component of grain fill or seed size.

• Field Scouting ... provides early detection and control of crop stress conditions.