ANR-853, New Dec 1994. Dallas L. Hartzog, Extension Agronomist, Professor, and James F. Adams, Associate Professor, both in Agronomy And Soils

Boron and Other Minor Elements for Peanuts

The Alabama Cooperative Extension System has placed strong emphasis in recent years on the benefits of crop rotation. Other than rainfall pattern and plant nutrition needs, crop rotation is the main factor that affects peanut yields.

Much land that was once planted to peanuts but then allowed to remain idle for years is now being planted in peanuts again. Many of these fields are sandy soils that are characterized by low fertility levels. Most have never received any boron fertilizer, or it has been many years since boron was applied.

Land planted to bahiagrass can also be rotated back to peanuts. Research and on-farm experience have both shown that the longer the rotation is in grass the greater the benefits and the longer they last. However, these fields generally also need boron.

In order to produce a good peanut crop, boron is essential. Other elements, though also essential, generally do not need to be applied to peanut fields in Alabama.

Boron

Boron is a highly mobile element that rapidly leaches from the soil. A boron deficiency often results in internal nut damage known as "hollow-heart," which greatly reduces the quality and value of the crop. In hollow-heart, the insides of the kernels are discolored and abnormal. Peanuts with hollow-heart do not fare well in the market because of their off-flavor and short shelf-life.

The Soil Testing Lab of Auburn University can analyze a soil for boron. However, because boron leaches very rapidly from the root zone, there is little correlation between boron levels shown in the test and the amount that is actually available to the plant during the growing season.

Until recently, most literature stated that boron deficiencies affected only quality, not yield. However, boron is necessary for normal fruiting of the peanut plant. When boron levels become very low and no supplemental boron is applied, fruiting does not take place. In severe cases of boron deficiency, yield can be almost wiped out. A strong indication of severe boron deficiency is split limbs.

Normal peanuts where boron was applied.		Peanuts with severe boron deficiency.

To satisfy the boron requirements of peanuts, the Auburn University Soil Testing Lab recommends an annual application of boron. The rate of boron is 1.0 pound per acre broadcast or 0.3 to 0.5 pound per acre applied over-the-row. Boron can be toxic to peanuts; therefore, it should be applied at the recommended rate only. Boron may be applied in fertilizer, in preplant herbicides alone, or with leafspot sprays. When applied with leafspot sprays, it should be included in the first broadcast application.

The most common source of boron is Solubor. Solubor, as its name suggests, is a water-soluble boron solution. It contains 20 percent boron.

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Zinc

Zinc application to peanuts has not been shown to increase yields or grades. Zinc deficiency is associated with high soil pH and high available phosphorus levels. These conditions do not generally exist in the peanut belt of Alabama.

Zinc toxicity (too much zinc) symptoms include chlorosis (yellowing), stunting, purple coloration of the main stem, and petioles. There may be lesions at the base of the plant, limb splitting, and premature dying of plant tissue. An effective liming program may reduce zinc uptake and stunting but will not change the level of zinc in the soil. Zinc toxicity will more likely be diagnosed on peanuts grown on sandy soils rather than on clayey soils.

Chlorine

Chlorine is an essential element for plant production, but chlorine deficiency has not been described for peanuts. There is no data that warrants fertilizer chlorine recommendations for peanuts.

Peanuts with zinc toxicity, showing signs of chlorosis, stunting, and split limbs.

Copper

Copper is a micronutrient that is very rarely applied to agronomic crops as a nutrient, but it is sometimes applied in the form of pesticides, particularly fungicides. The published literature indicates that Spanish varieties may be more sensitive to copper deficiency than the Runner varieties. In general, peanut yields have not been increased by copper application, and therefore copper is not recommended for peanuts.

Iron

No problems have been reported with iron deficiency on the acid soils of the Southeast. Most soils in the peanut belt of Alabama have iron levels much higher than those needed for normal crop production. Therefore, iron is not a recommended fertilizer element for peanuts.

Molybdenum

Molybdenum is essential for nitrogen fixation and is therefore recommended for some legumes such as alfalfa and soybeans. Molybdenum application may cause peanut foliage to be larger and darker green, but it has never caused a significant increase in yield. It is not recommended for peanuts.

Manganese

Manganese deficiency is a problem only on high pH soils. The typical symptom of manganese deficiency is interveinal chlorosis. Soil manganese applications can be used to prevent manganese deficiency when the soil pH is known to be high. Foliar manganese application can correct manganese deficiency, diagnosed through foliar analysis, more rapidly than soil manganese application. Manganese deficiency is a problem for peanuts grown in Virginia, but not in Alabama. Therefore, it is not recommended.

Trade names are used only to give specific information. The Alabama Cooperative Extension Service does not endorse or guarantee any product and does not recommend one product instead of another that might be similar.

For more information, contact your county Extension office. Look in your telephone directory under your county's name to find the number.