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Production of Biofuel Crops in Florida: Peanut

By D.L. Wright, professor, Agronomy Department, Florida Cooperative Extension Service. This article looks at the Production of Peanut for Biofuel with a focus on Florida.

Introduction

Peanut (Arachis hypogaea) is an annual legume that is commonly grown in the southeastern United States and also in Texas. This crop is well adapted to sandy Coastal Plain soils and does well on relatively infertile, droughty soils. It is one of the few crops that do well when grown on deep sands and responds to rotation as much or more than most agronomic crops. The majority of peanut acreage in Florida is in north and central Florida but can be grown throughout Florida and the southeast. Florida grows about 120,000 acres of peanut annually.

Figure 1. Florida counties with significant peanut production. (CREDITS: Hope Crawford, UF/IFAS Communication Services)
Peanuts are generally used in rotation with other crops such as cotton and corn. Florida has the longest ongoing peanut breeding program in the U.S. and has released many peanut varieties grown across the peanut belt. Florunner, developed in Florida, was the dominant runner peanut variety grown in the U.S. for more than 20 years.

Current potential for Use as Biofuel

Peanut is widely adaptable for the southeastern United States, has high oil content (45-52%) compared to many of the other oilseed crops and could produce more biodiesel than most of the other oilseed crops currently grown in the southeast. Since peanut needs to be planted in rotation with grass crops or cotton, it needs no direct fertilization aside from liming and boron under most conditions. Little or no research has addressed peanut as an oil crop, so breeding and selection for this attribute could greatly enhance the potential for peanut in the biodiesel market. Likewise, because peanut grade and quality are not important for the biofuel market, there may be several viable breeding lines among those that have been discarded due to non uniform size and other characteristics valuable to the edible trade. Peanuts will continue to be grown in the Deep South due to the long growing season needed for most varieties to mature.

Biology of Peanut

Peanut is a warm season annual legume crop that requires 125-150 days from planting to maturity. Peanuts begin pegging about 28 days after planting and continue pegging and flowering for another 5-6 weeks. After this period, pods begin to fill and peanuts have a high water requirement for 6-7 weeks to fill pods. Peanuts will continue to grow and have only moderate need for water during the last 6 weeks of pod fill. Runner types of peanuts are mostly grown in Florida but Virginia types can also be grown. Virginia types usually have higher input needs and may be more susceptible to diseases in Florida. Peanut grows much better in well drained soils; wet soils often make them prone to more pod, stem, and leaf diseases.

Production

Figure 2. Peanut Production Field (CREDITS: National Peanut Board, 2007.)

Production information can be found at http://edis.ifas.ufl.edu/AA258. Peanuts are produced under a wide range of soil and management conditions in Florida and the southeast. Generally peanuts do not respond to direct fertilization after either winter grazing or if used in rotation with crops that have fertilizer applied to them such as corn and cotton. However, it is still a good management practice to take soil samples immediately after harvest of the preceding crop to determine lime as well as fertility requirements for fields to be planted with peanuts the coming year. If soil pH needs adjusting, fall is a good time to apply lime because it may take as long as 6 months for full reaction. However, some reaction does occur soon after application.

Bacteria that fix nitrogen in symbiotic relationship to the peanut plant do better and form more nodules with an adequate calcium (Ca) level and with pH around 6.0 or higher. If the crop that precedes peanuts is well-fertilized, there may be enough residual nutrients to make direct fertilization unnecessary. The analysis of the soil sample will also tell you which nutrients are needed to grow peanuts on a particular soil. Calcium and magnesium (Mg) may be supplied by the limestone. If no lime is needed, Ca can be supplied by gypsum, and Mg can be included in the fertilizer. If phosphorus (P) is low, be sure to add sufficient P in the fertilizer. The same is also true for potassium (K) and other fertilizer nutrients,or micronutrients, needed by the peanuts.

Boron (B) is often the most deficient micronutrient, especially on sandy soils. Therefore, if peanuts are to be planted on a sandy soil, it would be advisable to use B in the peanut fertilizer. The B should be applied at the rate of 0.5-0.75 pound of elemental B per acre. Higher rates of B can be toxic to the plants. Applications of B should be split because it is a highly leachable, mobile nutrient. High application rates of other nutrients can make B deficiency more pronounced. B may be applied early with herbicides or with fungicides to alleviate the need for additional trips across the field.

The crop may take up less than a tenth of a pound per acre, but it is still important for crop production. Crop rotation is an important cultural practice that is recommended for all crops and especially for peanuts. Rotation is recommended to reduce the effects of pests (disease, nematode, insects, and weeds). Leafspot control is usually accomplished with a routine fungicide program but data shows that rotation with cotton or corn can reduce the amount and severity of disease. Recent data shows that rotations with bahiagrass can reduce the disease even further and will result in higher yields. In one study, peanut yields were 19% higher after 2 years of corn and 41% higher after 2 years of bahiagrass. Rotations produce more profit, and reduce the amount of management and capital inputs needed.

As mentioned previously, peanuts grow best in well-drained soils and in full sun. If planted in poorly-drained soils, diseases will be prevalent and yields are normally low. Peanuts can be grown in sandy or excessively-drained soils, but irrigation may be needed for consistent production.

Potiential Yields

Peanut production in Florida generally averages between 2500-2900 lbs/A. However, many of the better growers who use good management practices may average between 3500-4500 lbs/A. With a yield of 3000 lbs/A and a 70 grade (70% of the weight of the peanut in shell) and 50% oil content, peanut has the potential to produce 120-150 gallons of biodiesel/A. If varieties with better disease resistance can be developed and grown with no fungicide use, peanut has the potential to be a good biofuel crop.

Production Challenges

Peanuts became well established in Florida and the southeast with the quota system and were a very profitable crop. The quota system was dropped in the 2002 farm bill and peanut profitability declined. The most pressing challenge for peanut producers at the present time is managing tomato spotted wilt virus (TSWV). Varieties with some TSWV resistance have been developed. However, there are other management factors that have been changed to minimize damage from this disease. The biggest expense to growing peanuts at the current time is the fungicide program to control leaf spot. Fungicides often have to be applied as many as 6-7 times during the growing season if wet weather conditions occur. Peanut varieties need to be bred that require no fungicides and can produce good yields with minimal inputs.

Peanuts are also susceptible to wet weather during harvest season. If digging is delayed a week to 10 days, peanuts may lose as much as 500-1000 lbs/A. This is a hazard of disease control for leaf spot. If the plants become defoliated, they will often quickly drop the peanuts attached to pegs.

Currently peanuts cost 2-3 times as much to produce as soybean, and digging and harvesting are slower. Production costs will have to be reduced for peanuts to be competitive with some of the other oil seed crops even though oil content for the peanut is higher than for soybean and canola.

Figure 3. Peanut Production Field (CREDITS: National Peanut Board, 2007.)

Environmental Concerns

Peanuts are a good rotation crop for cotton, corn, and other grasses. Since peanuts require little fertilization, there is little concern for nutrient contamination or runoff.

Peanut must be rotated to maintain high yields. Peanut land was turned for years resulting in vast amounts of soil loss and erosion from fields. In recent years, it has been confirmed that peanut can be grown satisfactorily under minimum tillage. However, peanut farms have had the slowest movement to conservation tillage of any of the crops grown in the southeast and are therefore still of concern for the environmental community.

Peanut will have to be considered as a biofuel crop due to its high oil content. Production is well established and understood in the southeast. It will not likely spread to Texas because of its long growing season requirements. However, as plant breeders focus on peanut as a biofuel crop, it is likely that it can be competitive and will contribute to the biofuels industry.

January 2008

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