The Effect Of Solar Irradiance Weakness On Growth And Yield Of Soybean And Its Model Simulation

In the atmosphere, there are clouds, water vapor, ozone and other gases and aerosol particles, which will weaken the surface solar radiation, by absorbing, reflecting, scattering. Also these will adversely affect the growth and physiological properties of crops. In order to elucidate the effects of reduced solar irradiance on growth and productivity of agricultural crops, we conducted a field experiment.In this paper, we conducted a field experiment in Nanjing and the shading treatments is Soybean. In the field experiments, three treatment groups were set, namely CK, T1(60%CK), T2(40%CK), with the total natural solar radiation as the control group (CK), we studied the photosynthesis, growth and yield effects of soybean systematically when the solar radiation was reducing, and simulate the yield and dry matter of soybean with DSSAT model, which can provide a scientific basis of avoiding the effect of solar radiation weaken to the agricultural production in China. The main conclusions of this treatment were as follows:(1) Reduce solar irradiance delay the growth period. Compared with CK, the growth period of T1and T2delay one or two days. With the growth of soybean, there was a significant increase of plant height and leaf area, which would be more obvious if more solar radiation reduced.(2) The more solar irradiance reduced, the net photosynthetic rate, conductance of stomatal and stomatal limitation value will lower, but with a higher intercellular CO2concentration. Before the pod, The dry matter of leaf and stem were lower when growing with lower photosynthesis rate in the less solar radiation, but higher than CK after pod for the dry matter of CK quickly transferred to the husk.(3) The dry matter of each organs were changed. The tendency of ratio on leaf weight to total dry weight and the ratio on root weight to shoot were T2>T1>CK. The tendency of ratio on root weight to total dry weight is CK>T1>T2. But the ratio on stem weight to total dry weight was lower. The solar radiation weakens also significantly reduce saturated pods, total pod number, grain weight, and declined the yield. The yield of T1declined29.63%(P<0.01), and T2declined33.8%.(4) The amended DSSAT model is good at simulating the soybean yield and total dry matter with small relative error and high coefficient of determination, and good at simulating the stem or leaf dry matter accumulation of solar weaken soybean. The sensitivity analysis of soybean to solar radiation showed that: solar radiation weakened by50%was the soybean’s sensitive, which would seriously reduce soybean yield; and there was a threshold, which soybean yield would be the best, in0%-20%solar radiation increment. The sensitivity analysis of soybean to solar radiation and precipitation showed that: when the solar radiation weakened and precipitation was in any value, the solar radiation would be the main sensitive factor; or when solar radiation increased and precipitation was in any value, the precipitation would be the main sensitive factor.