Effects of Desulfurized Gypsum Addition on Saline-alkali Soil Nutrients and Photosynthetic Characteristics of Cultivated Oil-sunflower

The soil nutrient content of the ameliorated saline-alkali soils with different ages,and the diurnal courses curve of photosynthetic parameters,photosynthetic light response curve and yield of oil-sunflower(Helianthus annuus) grown on the ameliorated soils were measured to investigate the effects of desulfurated waste residue additions on the saline-alkali soils.The results showed that the soil electronic conductivity and pH value decreased while the soil organic matter,the concentration of available nitrogen(N),phosphorus(P) and potassium(K) increased with the ameliorating ages.And the net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs) and intercellular CO2 concentration(Ci) also increased markedly,but the water use efficiency(WUE) and stomatal limiting value(Ls) decreased.Meanwhile,the dark respiration rate(Rday),maxmum photosynthetic rate(Amax),light saturation point(LSP) increased obviously,while the light compensation point(LCP) decreased.A similar dramatic elevation was also found on the diameter size,plant weight and final yield of oil-sunflower.It was concluded that application of desulfurized gypsum can significantly facilitate the saline-alkali soil amelioration,enhance leaf photosynthetic capacity,promote crop growth and ultimately increase crop yield.Fig 2,Tab 3,Ref 29