Peanuts are a valuable field crop, but successful cultivation requires a highly specific fertilization program. As a legume, the peanut plant converts atmospheric nitrogen into a usable form through a symbiotic relationship with Rhizobium bacteria in its root nodules. This nitrogen-fixing capacity means growers rarely need heavy nitrogen applications, unlike many other crops. Instead, high yields and quality hinge on providing adequate amounts of other key nutrients, particularly calcium, at the precise time and location the plant needs them. A successful fertilization strategy depends on understanding the plant’s unique physiological needs and translating soil test data into an actionable nutrient plan.
Essential Nutrient Requirements for Peanuts
The nutritional focus for peanut production centers on secondary and minor elements, as the plant handles its own nitrogen supply. Applying excessive nitrogen fertilizer can be counterproductive. Too much nitrogen encourages lush, unproductive vine growth at the expense of developing pods, reducing the overall yield.
Calcium is the most important nutrient for quality because the developing pod has a unique uptake requirement. Unlike other nutrients transported from the roots, calcium is immobile and must be absorbed directly by the developing pod, or “peg,” from the surrounding soil solution. A lack of available calcium in the fruiting zone (the top two to three inches of soil) leads to “pops,” which are pods with unfilled or shriveled kernels.
Phosphorus and potassium are also required, though typically in lower quantities than for non-legume crops. Phosphorus supports robust early root development, establishing a strong, healthy plant. Potassium plays a role in overall plant vigor and nutrient transport. However, high levels of potassium in the fruiting zone can interfere with calcium uptake, making a balanced ratio between the two elements necessary for quality.
Interpreting Soil Tests to Guide Fertilizer Choice
A comprehensive soil analysis is the only reliable method for determining a field’s nutrient status and calculating fertilizer requirements. General recommendations are insufficient because nutrient levels can vary widely. The test results provide a measure of existing nutrient reserves, which informs the type and amount of fertilizer needed to achieve a specific yield goal.
A primary step in soil analysis is determining the soil pH, which should be maintained between 5.8 and 7.0 for optimal nutrient availability. If the pH is too low, a calcareous amendment like agricultural lime is necessary. This adjustment corrects acidity and often supplies calcium and magnesium. The soil test report indicates existing levels of phosphorus and potassium, usually reported in parts per million or pounds per acre.
Growers must translate deficiency readings into specific fertilizer purchases and application rates. If the soil test indicates low phosphorus and potassium, a low-nitrogen blend (such as 0-10-20 or 0-20-20) is appropriate to avoid excessive vine growth. For calcium, the soil test must focus specifically on the pegging zone, requiring a separate sample from the top few inches of soil. A calcium level of 500 to 600 pounds per acre, along with a calcium-to-potassium ratio of at least 3:1, is the minimum for high-quality kernel development.
If the pegging zone calcium level is below the recommended threshold, gypsum (calcium sulfate) is often selected. Gypsum is preferred over lime for in-season calcium application because it is pH-neutral and highly soluble, making the calcium readily available to the developing pods. Soil tests also provide information on micronutrients such as boron, which prevents kernel defects like “hollow heart.” Adjusting the fertilizer program based on these data ensures resources are allocated efficiently to correct specific deficiencies.
Application Timing and Placement Strategies
The logistics of fertilizer application are determined by the specific nutrient and the peanut plant’s growth cycle. Phosphorus and potassium are most effective when applied before or at planting and thoroughly incorporated into the root zone. This allows the developing root system to access these nutrients immediately, supporting early establishment and plant health. These nutrients are often broadcast across the field or banded near the seed row.
Calcium application is the most time-sensitive and placement-specific requirement. Since the developing pod must absorb calcium directly from the soil, the nutrient must be available in the top two to three inches of the soil profile (the fruiting zone). The ideal time for this application is at the beginning of the blooming or early pegging stage, typically 30 to 60 days after planting.
The most effective method for applying gypsum is to broadcast it directly over the row, concentrating it where the pegs will penetrate the soil. Applying calcium too early risks it leaching below the fruiting zone, especially in sandy soils. Adequate soil moisture is necessary following application to dissolve the gypsum and move the calcium into the soil solution for absorption. This strategic timing ensures the calcium supply is available precisely when the plant transitions to reproductive development, maximizing the potential for a full, high-quality kernel.