What are the soil and fertility requirements for organic peanut production?
Answer: Organic peanut growers need to get a sense of their soil fertility by obtaining a soil test report with recommendations specifically for peanuts. Previous experience with rotational cover crops and compost or manure applications is also helpful. Organic peanut growers must work closely with crop advisers familiar with organic production and peanuts.
Growers should always consider the history of the field they select for peanuts, especially if it is a new site. In 2003, the North Carolina Department of Agriculture and Consumer Services warned new peanut growers about zinc buildup due to chicken litter application, especially in eastern counties.
Some fields that received heavy, long-term litter applications now have zinc-index (Zn-I) values approaching [Zn-I = 300 (12 ppm), caution advised] or exceeding the toxicity thresholds [Zn-I = 500 (20 ppm), critical toxic level] for peanuts. Growing peanuts on fields with Zn-I values above 300 is not advisable. Officials alerted growers that toxicity was more likely for soil pH below 6.0
Lime is essential for successful peanut production. Soil pH needs to be carefully monitored and should be in the 5.8 to 6.2 range for Southern growers. Large-seeded Virginia peanuts require high calcium content in the soil surface at pegging for pod development and quality. Land plaster or gypsum, a by-product of drywall, is not allowed as a source of calcium in organic production. Mined sources of gypsum are allowed.
Excessive levels of potassium within the fruiting zone, or the top two to three inches of soil, are associated with peanut pod rot. Potassium also competes with calcium uptake at pegging, resulting in a high percentage of pops, or unfilled shells. Any potash (K2O) is incorporated along with the preceding crop’s fertilizer, if possible, in order to allow enough time for potassium to move below the fruiting zone before pegging.
Manganese deficiency may occur when soil pH exceeds 6.2. Again, careful soil monitoring and soil and plant analysis are recommended. The amount of boron recommended on a soil test report prevents hollow heart in peanuts. Boron can be applied as a pre-plant broadcast treatment along with other fertilizer applications, or as a foliar spray near blooming (Hardy et al., 2006).
Ready to learn more? Check out the ATTRA publication Peanuts: Organic Production. It discusses markets and production, including topics such as soil and fertility, pest management, diseases, irrigation, and harvesting.
Hall, Tim. 2003. Check zinc levels for new peanut fields. North Carolina Department of Agriculture and Consumer Services. p. 1.
Hardy, D.H., M.R. Tucker, and C.E. Stokes. 2006. Crop fertilization based on North Carolina soil tests. North Carolina Department of Agriculture and Consumer Services, Agronomic Division, Raleigh. Note 3. Fertilization of Field Crops. Peanuts. p. 4-5.