Effects of phosphite as a slow release phosphate fertilizer on nutrient absorption and photosynthetic characteristic in Cucumber

Using nutrient solution cultivation technique, the effects of different concentrations of phosphite on nitrogen and phosphorus contents in root, shoot, leaf and fruit of cucumber, dry weight and root/shoot, nitrogen and phosphorus contents per plant and photosynthetic characteristics were investigated. The results show that as the phosphite concentration in solution increased, the N contents in the fruit, leaf and root are decreased, while the N contents in shoot is not in statistically difference. The P contents in fruit and shoot are increased, while the contents in root are decreased, and the contents remain no differences in leaf. When the phosphite concentration is increased to some extent, the dry weights of all parts are decreased significantly, while the root/shoot ratios remain no differences. The N and P contents per plant are decreased and the net photosynthetic rates (Pn) are declined as the phosphite concentration in solution increased. These results suggest that as the phosphite concentration increased, cucumber is more likely to show a syndrome of phosphorus deficiency which reduces nutrient absorption and photosynthesis. The feasibility of phosphate being used as a slow release phosphate fertilizer is discussed.