Abstract
In order to study the effect of light competition and microclimatic modifications on the net assimilation (NA), growth and yield of soybean (Glycine max L.) as an understory crop, three 26-year-old soybean-tree (Acer saccharinum Marsh., Populus deltoides X nigra, Juglans nigra L.) intercropping systems were examined. Tree competition reduced photosynthetically active radiation (PAR) incident on soybeans and reduced net assimilation, growth and yield of soybean. Soil moisture of 20 cm depth close (< 3 m) to the tree rows was also reduced. Correlation analysis showed that NA and soil water content were highly correlated with growth and yield of soybean. When compared with the monoculture soybean system, the relative humidity (RH) of the poplar-soybean, silver maple-soybean, and black walnut-soybean intercropped systems was increased by 7.1%, 8.0% and 5.9%, soil water content was reduced by 37.8%, 26.3% and 30.9%, ambient temperature was reduced by 1.3°C, 1.4°C and 1.0°C, PAR was reduced by 53.6%, 57.9% and 39.9%, and air CO2 concentration was reduced by 3.7μmol·mol-1, 4.2μmol·mol-1 and 2.8μmol·mol-1, respectively. Compared to the monoculture, the average NA of soybean in poplar, maple and walnut treatments was also reduced by 53.1%, 67.5% and 46.5%, respectively. Multivariate stepwise regression analysis showed that PAR, ambient temperature and CO2 concentration were the dominant factors influencing net photosynthetic rate.
Highlights
Agroforestry, a conservation land management practice where trees, agricultural crops, grasses and/or animals are grown simultaneously on the same landscape, is being promoted as an alternative management system that can diversify income and improve environmental quality and environmental benefits on the farm landscape [1, 2]
Compared to the control treatment, the average photosynthetically active radiation (PAR) (2 m, 4 m and 6 m) on soybean under poplar, maple and walnut agroforestry systems was reduced by 53.6%, 57.9% and 39.9%, respectively
The results showed that the reduction of PAR on the understory soybean, as PAR Daily net assimilation(μmol m-2 s-1) Height Whole plant leaf area Whole plant leaf weight Total above-ground biomass Seed yield
Summary
Agroforestry, a conservation land management practice where trees, agricultural crops, grasses and/or animals are grown simultaneously on the same landscape, is being promoted as an alternative management system that can diversify income and improve environmental quality and environmental benefits on the farm landscape [1, 2]. Soybean Photosynthetic in Intercropping Systems had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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