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

Spring 1999, No. 8

Research results evaluating nutrient needs of new high yield peanut varieties such as Georgia Green are in short supply. Thus, basic knowledge from older studies plus recent production experience offers suggestions for fertilizing peanuts with (1) residual fertility or (2) direct fertilization or (3) a combination of both. The goal in all cases is to avoid plant development problems and to insure that plant nutrition does not limit yield, quality, profitability, and long-term productivity of peanuts.

• Peanuts, in general, yield well when grown after a well fertilized grass crop such as corn. Why? The reasons might include a break in the nematode cycle, moisture/nutrition benefits from the large amounts of root/shoot residues breaking down in the soil, and/or the carry-over benefits of nutrients unused by the grass crop.

• Soils should be tested for pH, phosphorus, potassium, magnesium, and other nutrients before planting the crop ahead of peanuts and again before planting peanuts. Why? First to establish lime and nutrient needs for both the grass and peanuts. The second testing determines if soil acidity was properly corrected and if the residual fertility levels were achieved by applying peanut fertility to the previous crop.

• Effectiveness and efficiency of peanut use of fertilizer phosphate and potash will likely be lower when applied to the previous grass crop. Why? Phosphate moves very little even in sandy soils and tends to chemically react with iron and aluminum in acidic soils. Potash rates high enough for two crops will increase the likelihood that some will leach from the sandy soils.

• The economic aspects of crop production are always a vital issue. Why? Fertilizer applied to a previous crop but destined for peanuts must be paid from the proceeds of that previous crop. However, this can be beneficial when moisture/production conditions exceed expectations. Extra production from tapping the "peanut fertilizer" can significantly improve profitability and still provide the needed residuals.

• Direct fertilization and liming of peanut soils is more challenging to the development of a peanut plant. Why? Lime should be incorporated at least three months before seeding to react with the soil and reduce soil acidity. Phosphate promotes root development and can go on with potash broadcast and incorporated into the soil or with some nitrogen as a starter nitrogen-phosphorus fertilizer in a band at least two inches to the side and below the seed. Placement of potash in the pegging zone (top 3 inches of soil) should be avoided as it can interfere with the movement of calcium and water into the pegs during this critical period of pod development. For medium/low testing soils, insure that fertilizer is placed outside the pegging zone.

• In depth research on nutrient management for high yielding peanuts is vital. Why? New knowledge is essential if the benefits from GPS/GIS technology and genetic potential of new varieties are to be realized. Environmental and economic considerations encourage site-specific nutrient management for each and all crops. Programmed fertilization to supply nutrient needs by growth stage is vital to lowering the unit cost of production and remaining globally competitive.