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Alternative Crop Guide

Published by the Jefferson Institute

Cowpea

A Versatile Legume for Hot, Dry Conditions


Overview

Cowpea is one of the most ancient crops known to man, with its center of origin and subsequent domestication being closely associated with pearl millet and sorghum. Now it is a broadly adapted and highly variable crop, cultivated around the world primarily as a pulse, but also as a vegetable (both for the greens and the green peas), a cover crop, and for fodder. Cowpea has a number of common names, including crowder pea, blackeyed pea, southern pea, and internationally as lubia, niebe, coupe or frijole. However, they are all the species Vigna unguiculata (L.) Walp., which in older references may be identified as Vigna sinensis (L.). The largest acreage is in Africa, with Nigeria and Niger predominating, but Brazil, West Indies, India, United States, Burma, Sri Lanka, Yugoslavia, and Australia all have significant production. Dry seed production is estimated at 1.24 million tons annually.

In the U.S. the largest commercial application is for types most frequently marketed as blackeyed pea which are harvested and then sold after cleaning (dry). In the Southern US there is substantial production of a variety of cowpea types, which after drying are sold to processors. These processors essentially cook and soak the dried product, to make it ready to heat and serve. These products may be either canned or frozen, and are referred to as a group as Southernpeas. This name probably derives from the common use of shelling the pods green and then cooking the peas fresh, similar to the common peas. The focus within this guide will be on production of dried blackeye pea, which can be harvested with conventional grain combines.

Cowpea is considered more tolerant to drought than even soybeans or mung beans, due to its tendency to form a deep tap root. By nature the plant is a vine, hence the best breeding opportunities for modem agriculture systems is with the more determinate and bush types, although for forage or cover crop applications the vine characteristic is preferred. There is a fairly active breeding program throughout the primary production areas, which include the Southeastern U.S., Arkansas, California, and Texas. Yield information is available on the varieties released from these programs.

California produced 90% of the U.S. dried cowpea in 1994; a total of 42,000 tons was produced in the U.S. that year. Dried blackeye pea has averaged from $0.23 to 0.43 per pound from 1982 to 1994.

Plant Description

All cultivated cowpea varieties are considered warm season and adapted to heat and drought conditions. Some varieties are erect and bushy, while others are viney in growth habit. Cowpeas may reach a canopy height of 30–36 inches in Indiana. However, more determinate types will be around 20–24 inches, and it is likely the indeterminate types will vine at that same height resulting in no further increase of the canopy height. The seed pods are borne above the leaf axil, thus the pods are very visible. The seed pod is typically 3 to 6 inches long and has 6 to 13 seeds per pod. The seed weight per bushel is 60 pounds with about 3000 to 4000 seeds per pound.

The germination of the seed is rapid at soil temperatures above 65°F. The preferred varieties for Indiana (early types) will set pods in about 60 days and mature in 90 to 100 days with a June planting. Leaves will dry down but may not drop off completely.

Due to its drought tolerance, cowpea has a competitive niche in soils that are sandy. Cowpea does not tolerate excessively wet conditions, and should not be grown on poorly drained soils.

It may have potential as a double crop after wheat or canola in the south half of Indiana, but would need further evaluation for this application.

Utilization

The use of the dried blackeye or purpleeye types is for food products. The dried beans are frequently sold directly to the consumer after cleaning and bagging. Another common product is the canned product, which is cooked with water prior to canning. Various soups and bean mixes will incorporate this product as well. Cowpea is considered nutritious with a protein content of about 23%, fat content of 1.3%, fiber content of 1.8%, carbohydrate content of 67% and water content of 8–9%. As in most legumes, the amino acid profile complements cereal grains.

The price of good quality blackeye peas is substantially higher than soybeans, fluctuating from slightly less than $14 to slightly over $25 per bushel.

Markets and Economics

With alternative crops such as dried blackeye or purpleeye peas, it is generally preferable to have a contract for growing the crop before planting. However, this market is fairly well established throughout the South and in California, so it may be possible to sell the crop successfully without having a production contract. Growers are advised to identify their markets as early as possible, rather than waiting until after harvest. It may be possible to direct market dried blackeye, or purpleeye peas to a food broker or retailer in Indiana.

Price for dried blackeye or purpleeye peas fluctuates due to normal production and demand factors, but averages around $0.30 per pound ($18 per bushel). Although this price is substantially higher than soybeans, it is offset by lower yields. Yields in the US are reported at 900–1350 pounds per acre, but up to 2700 pounds per acre in California. In Indiana yields of about 1000 pounds per acre should be expected with normal growing conditions and selection of an improved variety. Optimizing management on good soils would lead to higher yields. Although cowpeas benefit from good soils, the competitive advantage, when compared to soybeans, is probably on sandy loam soils or in other moisture limited situations. When soybean prices are low, dried blackeye or purpleeye peas become more competitive-its price as a food crop is unaffected by the price of soybean, which is driven primarily by demand for livestock feed.

Production costs for cowpea are very similar to soybeans, with the primary difference(s) being post-harvest cleaning and/or transportation. If several Indiana farmers worked together on a common delivery point for dried blackeye or purpleeye peas, transportation costs could be reduced. A double cropping practice with no additional fertilizer would keep the production costs fairly minimal.

Overall, dried blackeye or purpleeye peas can be looked at as another crop to diversify the crop base on a farm, They compare well to soybeans on some drought prone soils. The fact that they are a food crop rather than a feed crop, can buffer a farmer's economic risk from variability in weather or commodity crop prices.

How to Grow Cowpea

Growing blackeye or purple eye peas is fairly straight forward, with management practices being similar to soybeans. Selection of a determinate, bush type will further the similarities, as the vine types will close the row quicker than soybeans and reduce the time one can cultivate.

Variety Selection and Seed Sources

The extreme variability of the species has led to a number of commercial cultivars grouped by the variance in bean shape, size, and color.

For crop breeding uses these various types may be crossed to give desired characteristics. For instance the southern pea varieties have used various blackeye, crowder, and cream types for this fresh green seed or green pod market. Some comparable data on variety yields comes from central Missouri, with yields with the better varieties ranging in yield from 800 to 1200 pounds per acre. Texas pinkeye was a good performer. Choice of market class, and approach to narrow or wide rows can affect which variety to choose. Contact the Jefferson Institute (573-449-3518) for a complete list of seed sources and recommended varieties.

Planting

Blackeye or purpleeye pea varieties should be planted in early June in Indiana, although planting dates from the latter part of May through mid-June are appropriate. A seeding rate of 50 pounds per acre is recommended and the field type seed cost is typically $0.35/pound. Plant populations in wide rows should be similar to soybeans, about 4 to 8 plants per foot of row. Field trials were done in Missouri on 30 inch row spacings, and the vine type varieties filled in the row well. The determinate, bush types may yield better on closer row spacing. The seed should be planted similar to soybeans, at 1 to 1 1/2 inches deep. If drilling cowpeas, the seeding rate should be increased in a similar percentage that soybeans are increased for this same application (row planting versus drilling). This same approach should also be taken if using a no-till planting methods. If cowpeas are planted no-till drilled, a seeding rate around 80 pounds per acre is recommended.

Fertility Management

As a legume fixes its own nitrogen, cowpeas do not need nitrogen fertilizer. However, applying nitrogen at a rate of 25 pounds per acre may give a boost to early growth, and increase the height of the pod set to facilitate harvest. Cowpeas do fix nitrogen without the addition of Rhizobium, as long as this bacteria is present in the soil from previous soybeans cultivation. Potassium and phosphorus needs have not been studied for cowpea in the Midwest. Using the amounts recommended from soil tests for soybeans would be appropriate. Soil pH should be close to neutral.

Pest Management

Weed control options are less than soybeans, but more than many other crops. Labeled herbicides* are Dual, Poast, Pursuit, Treflan, and sodium chlorate. Pursuit and Treflan both provide some broadleaf control, while all the products control grass weeds. However, row crop cultivation may be more necessary than for soybeans, depending on the weed pressure, soil conditions, and rainfall. Preplant tillage can greatly help reduce early weed pressure, or cover crops can potentially be used for weed control.

Insects and diseases have not been a significant problem in Midwest field trials. However, a number of diseases and pests are reported in southern locations, and active breeding has taken place for resistant varieties. In southeastern production areas the major insect pest is cowpea curculio and the major disease is root knot, a severe root disease incited by several rootknot nematodes (Meloidogyne spp.).

Diseases reported are fusarium wilt, bacterial canker, southern stem blight, cowpea mosaic virus (and several other less prominent viruses), cercospora leaf spot, rust and powdery mildew. The following fungicides* are registered for cowpeas-Maxim, Mefenoxam, Metalaxyl, Mycostop, Ridomil-Gold, and Thirarn.

Insects reported are Mexican bean beetle, bean leaf beetles, cowpea curculio, aphids, green stink bug, lesser cornstalk borer (and maybe others), and weevils (when in storage). The following insecticides* are registered on cowpeas-Adios, Azadirachtin, Bacillus thuringiensis, Di-Syston, Gaucho, Guthion, Insecticidal soap, Lorsban, Mattch, Methaldehyde, Methomyl, Methoxychlor, Pyrellin, Pyrethrin, Sevin, Success, Telone, and Trilogy.

*Pesticides mentioned as being labeled in this publication are based on reference lists published in the Thomson Publications "Quick Guide" on crop pesticides, 1999 edition. These lists are believed to be accurate, but given the changing nature of herbicide registrations, labels and relevant government regulations should be checked before approving any pesticide.

Harvesting and Storage

For the whole seed market, quality of seed is important, so care in harvest and post-harvest handling may be important to avoid cracked or split seed. Handling the product at a higher moisture reduces splitting of the seeds. If the leaves are still green at the time pods mature, Gramaxone may be applied as a harvest aid. Cowpea grown as a dried pea product can be direct combined using a platform head or a row crop head. Adjustments to combine settings, and possibly screen/sieve sizes, should be made for the cowpea seed. It is slightly larger than soybeans and kidney shaped. The grain can be stored short term at around 12% moisture or less, with 8 to 9% recommended for long-term storage. Some buyers will want the seed cleaned and bagged, while others will take the grain in bulk form and clean it themselves. When sold for the processing market, cowpeas are frequently sold at harvest by the truckload, at a higher moisture—17% and less being accepted for delivery. The product may benefit from a coarse cleaning process after harvesting to remove foreign material. It should then be delivered quickly (one day or less) to prevent quality degradation. Cowpeas are checked for discolored seeds, as well as foreign material and the payment adjusted accordingly. Product may be rejected if there are too many discolored, broken or cracked seeds.


Written by James Quinn Published by the Jefferson Institute, Columbia, MO, a non-profit research and education center supporting crop diversification (ph: 573-449-3618). Development of this publication was funded by the USDACSREES Fund for Rural America program, as part of a cooperative project with the University of Missouri, Purdue University, and other universities.

Published 3/99, Indiana edition