Understanding interactions between cropping pattern, maize cultivar and the local environment in strip-intercropping systems
Strip-intercropping systems combine the possibility to increase productivity and resource-use-efficiency with the facilitation to accommodate machinery. In strip-intercropping systems with maize, competition for light strongly influences the total productivity. Therefore, we studied plant growth and yield formation in maize grown in strips with a neighboring, shorter crop (e.g. bush bean) over three growing seasons in the North China Plain (NCP) with irrigation and over four growing seasons in south-western Germany without irrigation. The chosen locations represented different latitudes, weather, and management conditions. Based on these data, interactions between the local environment, mainly radiation and water availability, and the planted maize cultivars were investigated. Further, a light partitioning model was used to study the effect of strip width, maize canopy height and leaf area index (LAI), latitude, and sky conditions on the light availability across the strip of bush bean over the co-growing period with maize. Experimental results showed an increase of maize yield in border rows in years with sufficient water supply. On average, maize yields calculated for strips consisting of 18 to four rows showed an increase by 3 to 12% at the German and 5 to 24% at the Chinese sites, respectively. Among the three cultivars included in this study, yield in border rows increased mainly by a larger number of kernels per plant. Those were achieved by a larger number of ears per plant in the German cultivars and by larger number of kernels per ear in the Chinese cultivar, respectively. Simulations of the light availability across the strip of the neighboring, shorter bush bean crop indicated that increasing the strip width might only reduce shading in the border rows when the bush bean is grown at lower latitudes under a high fraction of direct radiation. When grown at higher latitudes, the selection of a maize cultivar with reduced height and LAI are suitable options to increase the light availability for the shorter crop. However, shade levels in the border rows of the shorter crop remain high at around 25%. For the future improvement of the productivity of strip-intercropping systems, the selection of suitable maize cultivars and shade-tolerant cultivars and species will be decisive.
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