| Previous researches indicated that, with the delaying of the sowing time, nutritive growth period was reduced, dry matter accumulation and grain seed setting was decreased. In this case, yield declined significantly according to original planting method and density. For this reason, it is expected by increasing the planting density to compensate yield losses caused by delayed sowing, seeking sowing density cultivation technology coordination which could adapt to the reality of the condition, and offering a technological support for sourthern intercropping soybean production. To investigate the effects of sowing time and density on agronomic traits, dry matter accumulation and yield of soybean in maize-soybean relay strip intercropping system, a two-year field experiment was conducted with three sowing times (June 15, normal sowing time, late sowing time:June 25, properly late sowing time and July 5, too late sowing time; denoted as A1, A2 and A3) and four densities (8.25×104plant.ha-1,11.25×104plant.ha-1,14.25×104plant.ha-1,17.25×104 plant.ha-1, denoted as B1,B2, B3 and B4). The results were showed as follows:1. Different densities had no significant effects on all growth period under different sowing times. With the delaying of the sowing time, all growth period and the symbiotic period were shortened. Sowing time had more remakerable effect on days of ermergence to flowering than flowering to physiological maturity.2. Compared to normal sowing (June 15), late sowing (June 25, July 5) declined the plant height, the stem diameter, the first internode length, pods of branches, branching number. The plant height increased with increasing density under different sowing times (normal sowing and late sowing). The difference was insignificant under late sowing. The stem diameter decreased with increasing density. There was a significant difference on R1-R4 and no significant difference on R8 under late sowing. The branching number decreased with increasing density, the difference was insignificant under late sowing. Density have a remarkable on pods of branches. Compared to normal sowing (June 15), properly late sowing (June 25) declined lodging rate and diseased plant rate. The lodging rate and diseased plant rate increased with increasing density. Diseased plant rate of the density treatments had no significant difference under late sowing.3. Sowing time and density significantly affected the photosynthesis characteristics of soybean.To SPAD, with the growth process moving forward, leaf SPAD of soybean increased. Properly late sowing could improve SPAD. High density planting could reduce SPAD. SPAD of high density treatment was lowest under different sowing times (normal sowing and late sowing) on V5 and R4.To leaf area index, with the growth process moving forward, soybean leaf area index increased. Sowing time had no significant effect on it on R1 to R4. Leaf area index reduced on R4 and first increased and then decreased on R5 with the delaying of the sowing time. Leaf area index of the growth period increased with the increase of density under under different sowing times (normal sowing and late sowing). The leaf area index between B3 treatment and B4 treatment was not significantly different.Sowing time and density significantly affected the photosynthesis characteristic parameter of soybean. To net photosynthetic rate, properly sowing could improve leaf net photosynthetic of the growth period. It first increased and then decreased with the increase of density under different sowing times (normal sowing and late sowing), especially under proper late sowing (June 25). To the stomatal conductance, properly sowing could improve leaf stomatal conductance, it first increased and then decreased with the increase of density, the difference was insignificant under late sowing. To transpiration rate, it under sowing time treatment (B3) was lower than under others. The transpiration and stomatal conductance under different densities treatment manifested same change trend. To intercellular CO2 concentration, compared to normal sowing, intercellular CO2 concentra-tion increased under late sowing. It reduced with the increase of density under different sowing times (normal sowing and late sowing).4. Sowing time and density significantly affected the dry matter accumulation, distrubution and output of soybean. the results showed that, compared to normal sowing (June 15), properly late sowing (June 25) declined the plant height, the stem diameter, post-anthesis dry matter accumulation per plant of soybean, increased the post-anthesis dry matter accumulations, crop growth rate, pods allocation ratio, output rate and transfer rate from stem and leaf of soybean. Moreover, properly high sowing density (B3) resulted in the increase of the post-anthesis dry matter accumulations, crop growth rate and pods allocation ratio under different sowing times (normal sowing and late sowing), especially under proper late sowing (June 25). Dry matter accumulations and the post-anthesis crop growth rate of soybean in treatment A2B3 were highest.pods allocation ratio of treatment A3B3 were highest, treatment A2B3 on the second place. Meanwhile, output rate and transfer rate of stem and leaf could be improved by increasing density.5. Sowing time and density significantly affected yield and yield components of soybean. Compared to normal sowing (June 15), properly late sowing (June 25) increased grain number per plant, economic coefficient, Moreover, with the increase of density, pods and seeds per plant decreased, economic coefficient, It was beneficial to improve the yield of soybean with properly late sowing (June 25) with high sowing density (B3), which was higher than the treatment of A1B3 by 6.8% on average over two years. |
PDF Full Text Request