| In relay intercropping system, root and aboveground part growth environment for soybean and maize was different greatly from sole cropping. Different arrangements for row spacing of maize and distance between maize and soybean were set under conditions of 2.0 m of strip width in this experiment, which altered the level of shade above soybean canopy and changed the growth space for maize roots and leaves. Responses of root and aboveground biomass accumulation, morphological growthof root, ability of absorbing, accumulating and transportingnutrients of root for soybean and maize to different intercropping environment had been investigated. The main results showed as follows:1. The intensity of shade above soybean canopy increased gradually with the expanding of maize row spacing and the diminishing of the distance between maize and soybean. Aboveground and root biomass, total root length, root surface area, root volume, the accumulation of nitrogen (N), phosphorus (P) and potassium (K) in root, roots bleeding intensity, and the content of nitrate and ammonium N, P, K and soluble sugar in bleeding for soybean were all significantly decreased under relay intercropping-shade, and more reduction of aforementioned indexes resulted from increasing shade intensity. According to regression analysis, aboveground and root biomass and morphological traits of root displayed a slow-fast-slow rule of declining with reducing the distance between maize and soybean. Compared with sole cropping, aboveground biomass, root biomass and morphological traits of soybean declined slightlyunder the distance being set between 0.6 m and 0.7 m. However, the intercropping arrangement against soybean growth inhibited aboveground and root biomass accumulation and growth of root morphology while the distance was lesser than 0.6 m.Therefore, poor growth of root caused sharp decline in the accumulation of N, P and K in root, bleeding intensity and the content of nitrate and ammonium N, P, K and soluble sugar in bleeding, which indicated the ability in root of absorbing, accumulating and transportingnutrients weakened. Ultimately,the shortage of nutrients supply resulted in further limits on growth of aboveground part and even the whole plant, and the inadaptation to the intercropping shade environment.2. The relay intercropping environment had no significant effect on growth of maize plant while row spacing was between 0.6 m to 0.8 m. Nevertheless, aboveground and root biomass, root volume and the accumulation of N, P and K in root for maize plant all reduced when row spacing was narrower than 0.6 m in relay intercropping, compared with sole cropping.Arrangements that row spacing was narrower than 0.4 m, led to severe competition of soil space and nutrients for root, and competition of spread space for leaves in narrow-row. As a consequence of too narrow row spacing, leaves overlapped seriously in narrow-row, and aboveground and root biomass, fresh weight and volume of root all decreased sharply. Poor root growth resulted in large declines in accumulation of N, P and K in root, and weakening the ability of absorbing and accumulating nutrients was not conducive to growth of aboveground part and even the whole plant.3. The relay intercropping system used light resource efficiently in arrangement of 0.4 m of maize row spacing and 0.6 m of the distance between maize and soybean, and showed the highest aboveground and root biomass equivalent ratio and land equivalent ratio (LER) among all of arrangements. Either enlarging row spacing of maize and the distance being lesser than 0.6 m or widen the distance and row spacing being narrower than 0.4 m could reduce biomass and yield production efficiency of crop population in relay intercropping, because enhancing the intensity of relay intercropping-shade suppressed soybean growth or increasing the level of intraspecific competitionrestricted maize growth. |
