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Yield of Corn, Cowpea, and Soybean Under Different Intercropping Systems¹

Intercropping is presently a major method of crop production in tropical Africa, subtropical Asia, and Central and South America. With this approach, crops are planted in such a variety of combinations that the merits of intercropping as compared with monoculture are often difficult to determine. Our objective was to evaluate the merits of intercropping legumes and grasses in the United States. Corn (Zea mays L.) was intercropped with cowpea (Vigna unguiculata (L.) Walp.] and soybean [Glycine max (L.) Merr.] on a Norfolk sandy loam soil (fine, loamy siliceous, thermic Typic Paleudult). The legumes were either planted in the rows with corn or alternate to the corn rows. Control plots were monocrops of corn and the legumes, with each species fertilized according to soil test recommendations. Both dry matter and seed yield of the monocrops were higher than the individual components in the intercrops. Intercropped corn yield ranged from 46 to 90% of the reference monoculture. The lower dry matter production in the intercropped plots may have been due to competition between the corn and legume components for N. Seed yield of intercropped cowpea ranged from 42 to 56% of monoculture. Intercropped soybean seed yield ranged from 52 to 54% in 1980, and 48 to 60% in 1981 of the monoculture. Dry matter accumulation was significantly greater for the monocrops but varied non-significantly, between the alternate and within row system. The corn-cowpea intercrops, which had Land Equivalent Ratios (LER) up to 1.27 in 1980 and 1.32 in 1981 and Area Time Equivalent Ratios (ATER) as high as 1.19 in 1980 and 1.25 in 1981, were more productive than the corn-soybean intercrops. The corn-soybean combination had a maximum LER in 1980 of 1.22 and 1.10 in 1981, while the maximum ATER was 1.12 in 1980 and 1.01 in 1981. Thus, both the LER and ATER showed that intercropping resulted in greater productivity per unit of land than monocultures of the intercrop components.

Key Words: Multiple cropping • Seed legumes • Crop productivity • LAI • LER • ATER • Zea mays L. • Vigna unguiculata (L.) Walp. • Glycine max (L.) Merr.

² Professor of agronomy and former graduate assistant, Dep. of Agricultural Sciences, Tuskegee Institute, AL 36088.

Received for publication December 27, 1982.