Peanut-Corn Intercrop Performance as Affected by Within-Row Corn Spacing at a Constant Row Spacing

The advantages of intercropping a cereal with a grain legume are often limited by the dominance of the cereal, which severely inhibits the legume. A field experiment was conducted in 1983 and 1984 in southern Maryland to determine the effects of within-row corn (Zea mays L.) spacing on a peanut (Arachis hypogaea L.)-corn intercrop. ‘Southern States 35A’ corn was planted in rows 1 m apart, with a double row of ‘Florunner’ peanut planted midway between. Peanut spacing was uniform, but within-row corn spacing varied from 0.125 to 0.335 m in a systematic design with spacing in adjacent pairs of corn rows differing by 0.03 m. Separate sole-crop plots of either four corn rows with 0.155-m spacing or four double rows of peanut were used as controls. Yield components of both crops, shading on the peanut canopy, and nitrogenase activity of the peanut were measured. Averaged across corn spacings, intercropping reduced peanut yields by 44 and 64% in 1983 and 1984, respectively. Corn yields were not significantly affected by intercropping, but decreased linearly from 4.2 to 3.5 Mg ha⁻¹ with decreased population density of corn. Conversely, peanut pod yield per hectare, pods per plant, and nitrogenase activity per plant increased linearly with decreased corn population density. Because of these countervailing trends, the combined yield and the land equivalency ratio (LER) (1.49 in 1983, a dry year, and 1.28 in 1984, a wetter year) of the intercrops were little affected by corn spacing. The 0.125-m within-row corn spacing resulted in the highest corn and combined dry seed yields, while the 0.335-111 within-row corn spacing resulted in the greatest combined economic value because of greater peanut yields. Peanut in monoculture gave the greatest economic value. This study pointed out that very low corn densities («30 000 plants ha⁻¹) should be considered in peanut-corn intercrops and that an LER >1.0 does not necessarily imply an economic advantage to intercropping. Contribution from the Dep. of Agronomy and the Univ. of Maryland Agric. Exp. Stn., Univ. of Maryland, College Park. Scientific Article no. A-4661 and contribution no. 7657.