Strip intercropping of corn-soybean in irrigated and rainfed environments

A strip intercropping system of corn (Zea mays L.) and soybean [Clycine Mau (L.) Merrill] has the potential to reduce soil erosion and increase the bi ological 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 easte rn 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 Agricultur al Research and Development Center near Mead. A full-season corn hybrid was grown in strips in combination with soybean cultivars of different maturit y groups. Yields of the two border rows of corn and soybean strips were mac hine harvested and compared with the middle four rows of each crop strip to determine border effects. Under irrigated conditions, corn yields in the o utside two rows increased in 4 of 5 yr, A maximum yield increase of 28 bu/a cre occurred in 1986, with a 5-yr average increase of 17 bu/acre (11%) in t he corn borders. Under rainfed conditions, corn border row yield increases were less consistent, averaging 5 bu/acre, In 1989, a maximum corn yield in crease of 19 bu/acre (23%) was obtained in the rainfed environments. Soybea n yields were reduced in the outside two border rows compared with the midd le four rows under both rainfed and irrigated environments. Yields from soy bean 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, s uggesting no benefit under either condition for the multispecies systems. A lthough economics of the system are dependent on corn and soybean prices, r esults of these experiments indicate strip intercropping systems of corn-so ybean show no consistent differences in systems yield or net returns compar ed with monoculture fields under the same conditions. Strip intercropping w ill then benefit by reducing erosion on soybean stubble.