Strip Intercropping of Corn-Soybean in Irrigated and Rainfed Environments

Abstract

A strip intercropping system of corn (Zea mays L.) and soybean [Glycine Max (L.) Merrill] has the potential to reduce soil erosion and increase the biological and economic efficiencies of a corn-soybean rotational system. The objective of this study was to evaluate grain production in a corn-soybean strip intercropping system under irrigated and rainfed conditions in eastern Nebraska. Corn and soybean were grown in alternating 20 ft. (eight-row) strips in a north-south orientation on a Sharpsburg silty clay loam (fine, smectitic, mesic Typic Argiudolls) at the University of Nebraska Agricultural Research and Development Center near Mead. A full-season corn hybrid was grown in strips in combination with soybean cultivars of different maturity groups. Yields of the two border rows of corn and soybean strips were machine harvested and compared with the middle four rows of each crop strip to determine border effects. Under irrigated conditions, corn yields in the outside two rows increased in 4 of 5 yr. A maximum yield increase of 28 bu/acre occurred in 1986, with a 5-yr average increase of 17 bu/acre (11%) in the corn borders. Under rainfed conditions, corn border row yield increases were less consistent, averaging 5 bu/acre. In 1989, a maximum corn yield increase of 19 bu/acre (23%) was obtained in the rainfed environments. Soybean yields were reduced in the outside two border rows compared with the middle four rows under both rainfed and irrigated environments. Yields from soybean rows adjacent to corn were reduced an average of 6 bu/acre over the 5-yr period. Land Equivalent Ratios (LER = land area needed in monoculture to equal production in one unit area of intercropping) averaged 1.00 and 0.96 for the irrigated and rainfed strip intercropping systems, respectively, suggesting no benefit under either condition for the multispecies systems. Although economics of the system are dependent on corn and soybean prices, results of these experiments indicate strip intercropping systems of corn-soybean show no consistent differences in systems yield or net returns compared with monoculture fields under the same conditions. Strip intercropping will then benefit by reducing erosion on soybean stubble.