Colquitt County Ag Report

News, events, and happenings in agriculture.

The UGA Peanut Fertilization Strategy … In a Nutshell

Glen Harris, Professor, Extension Agronomist – Environmental Soil & Fertilizer University of Georgia

Because the peanut plant is a deep-rooted legume that fixes nitrogen and is a good scavenger of “P&K’, most people say it doesn’t need a lot of fertilizer. That is not necessarily true and if you come up short on something like pH or calcium it could really reduce yields and quality. Therefore, if you follow this simple strategy that I try to mention at every county peanut meeting you should take soil fertility out of the picture as far as a limiting factor:

1. Soil Test. – This is the only way to know if your soil pH is correct, if your phosphorous and potassium levels are good and if the pH to micronutrient relationships are in line to avoid zinc toxicity and manganese deficiency. Things like sulfur, cation exchange capacity (CEC )and base saturation are not that critical comparatively.

2. Lime to a pH of 6.0-6.5. Nutrients such as P and K are more readily available in this range and the nitrogen fixation process also needs pH in this range. Grid sampling and variable rate liming is a great tool to use to ensure good soil pH across the whole field.

3. Apply P & K at planting if recommended. There is no advantage to “split” applications of these nutrients like we do with nitrogen on other crops. And phosphorous is needed early for seedling root growth.

4. Inoculate with the proper Rhizobium. The official UGA recommendation is to inoculate only if you have been out of peanut in a certain field for more than 4 years. However, research studies have shown enough yield increase to cover the cost of inoculation even in short rotations.

5. Provide Calcium to the Pegging Zone. The traditional ways to accomplish this are either lime at planting or gypsum at early bloom time. If you have at least 500 lb/a soil test calcium in the top 4 inches of soil (the pegging zone) AND a Ca:K ratio of 3:1 or higher , then you are not likely to see a yield response to calcium fertilization. However, all seed peanuts should automatically receive 1000 lb/a gypsum (calcium sulfate) at early bloom and a lot of gypsum is applied “just in case” or as “insurance”. I wouldn’t argue with this strategy and would rather see you put your fertilizer dollars for peanuts into gypsum than into some “unproven” and “untested” product.

6. Apply 0.5 lb Boron/a. There are a number of ways to apply boron, the easiest being foliar feeding 0.25 lb B/a when tank mixed with your first two fungicide sprays. Also beware of products recommended at very low rates. For example, 6 oz of a 5 % liquid boron only gives you 0.025 lb B/a.

7. Foliar Feed Manganese when needed. The best way to determine need is to tissue sample and then follow the foliar feeding guidelines if the levels are below threshold.

8. Troubleshoot. As soon as you suspect a low pH or nutrient problem in peanut, take soil and tissue samples from “good” and “bad” areas of the field. If you suspect nitrogen problems, dig up the roots and check for nodules which should be pink in color on the inside.

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