About

Peanuts are the seeds of an annual legume, which grows close to the ground and produces its fruit below the soil surface. U.S. peanuts are planted after the last frost in April or May when soil temperatures reach 65–70° Fahrenheit (20° Celsius). Pre-planting tillage ensures a well-prepared seedbed. Seeds are planted one and half to two inches (four to five centimeters) deep, one every two to four inches (5–10 centimeters) in the Southeast and Southwest, and four to six inches (10–15 centimeters) in the Virginia-Carolina area, in rows about three feet (one meter) apart. The row spacing is determined to a large extent by the type of planting and harvesting equipment utilized.

Peanuts may be cultivated once or twice (depending on region) to control broadleaf weeds and grasses. A climate with 200 frost-free days (175 days for Spanish varieties) is required for a good crop. Warm weather conditions, adequate moisture, and fertile, sandy soil result in the appearance of peanut leaves in 10–14 days after planting. Farmers generally follow a three-year rotation pattern with cotton, corn or small grains planted on the same acreage in intervening years to reduce disease problems. In addition, many farmers utilize irrigation in an effort to reduce crop stress and thereby enhance opportunities for the production of high quality peanuts.

Integrated pest management is utilized in order to control weeds, diseases, and insects. Diseases caused primarily by several fungal organisms are particularly troublesome and generally require chemical control. Weeds are controlled using either chemical or mechanical methods or a combination of the two.

The peanut harvesting process occurs in two stages. Digging, which is the first stage, begins when about 70% of the pods have reached maturity. At optimum soil moisture, a digger proceeds along the rows of peanut plants driving a horizontal blade four to six inches (10–15 centimeters) under the soil. The digger loosens the plant and cuts the taproot. A shaker lifts the plant from the soil, gently shakes the soil from the peanut pods and inverts the plant. A windrow of inverted plants results and this exposes the pods to the sun. The peanuts are now ready for the second phase of the harvest — combining. After drying in the field for two or three days, a peanut combine (also known as a thresher) separates the pods from the vines, placing the peanut pods into a hopper on the top of the machine. The vines are returned to the field to improve soil fertility and organic matter. Freshly harvested peanut pods are then placed into drying wagons for further curing with forced hot air slowly circulating through the wagons. In the curing process, moisture content is reduced to 8–10% for safe storage.

After proper curing, farmers’ stock peanuts (harvested peanuts that have not been shelled, cleaned or crushed) are inspected and graded to establish the quality and value of the product. The inspection process determines the overall quality and on-farm value of the shelled product for commercial sales or price support loans.
The inspection and grading of peanuts by the Agricultural Marketing Service of the U.S. Department of Agriculture (USDA/AMS) occurs at buying stations or shelling plants usually located within a few miles of where the peanuts have been harvested. A pneumatic sampler withdraws a representative quantity of peanuts from the drying wagon, and from this sample the USDA inspector determines the meat content, size of pods (for Virginia &Valencia), damaged kernels, foreign material, and kernel moisture content. Once the grade is established, the loan or commercial value is determined from USDA price support schedules.

After grading, peanuts move on to the shelling process. In the first step of this process, peanuts are cleaned — stones, soil, bits of vines and other foreign materials are then removed. The cleaned peanuts move by conveyor to shelling machines where peanuts are de-hulled as they are forced through perforated grates. The peanuts then pass through updraft air columns that separate the kernels from the hulls. Specific gravity machines separate the kernels and the unshelled pods. The kernels are then passed over the various perforated grading screens where they are sorted by size into market grades.
The edible nuts are individually inspected with high-speed electronic color sorting equipment that eliminates discolored or defective kernels as well as any remaining foreign material.

In-shell peanuts are usually produced from large Virginia or Valencia type peanuts that have been grown in sandy and light-colored soil for bright hulls. Sizing screens remove the small pods while updraft air columns remove very immature and lightweight pods. The largest remaining pods are separated into size categories by screens. Stems are removed and any remaining immature pods are removed by specific gravity. Electronic sorters then remove dark, cracked, or damaged pods so that only the most mature, brightest pods remain.