| Strip intercropping maize [Zea mays L.] and soybean [Glycine max (L.) Merr] is increasingly popular because of its relatively easy implementation, potential for environmental protection and improved yields. The objectives of these studies were to determine the effects of plant density and environment on yield and yield components of maize and soybean in monoculture and at the interface in strip intercropping. Maize and soybean were grown in 8-row strips in six environments from 1991--1993 on a Sharpsburg silty clay loam soil. Maize and soybean yields responded similarly to density in monoculture and in the strip interface. As density increased plant height and grain and stover yields on an area basis increased and harvest index decreased. On a per plant basis, grain and stover yields decreased as density increased. Averaged across densities, maize grain yield was 17% higher but soybean was 20% lower at the interface compared to monoculture. To determine complementation or competition in resource use at the interface, additional calculations were made to estimate expected grain and stover yield based on actual monoculture data and the geometric land surface areas surrounding each plant in each crop. Actual per plant maize grain yields were 4--21% higher and stover yields 1--8% higher than expected at the maize/soybean interface, indicating a competitive advantage by maize above what was expected. Actual per plant soybean yields at the interface were higher than expected for grain (5--6%) and stover (7--8%), but only when maize density was low. Medium or high level maize density caused a competitive disadvantage for soybean represented by lower than expected soybean grain (-3--12%) and stover (1--10%) yields. In a supplemental observational study of competition at the interface, similar data and conclusions on maize/soybean strip intercropping were found in plots using natural field variation without the substantial efforts necessary for the conventional RCBD experimental study. Further research is needed to determine if observational studies could play a useful role in collecting preliminary data to help with farm management decisions. |
