| Many studies showed that CRFs' nutrient release rate was accordant with plant nutrient uptake, which could improve fertilizer use efficiency. In order to illustrate phosphorus use efficiency, the change of phosphorus availability and phosphorus fraction in soil with controlled-release compound fertilizers, nutrient release in water, sorghum pot experiment and potato field plot experiment were conducted in this study. Two kinds of controlled-release compound fertilizers (CRCF) and controlled-release-monoammonium phosphate (CRMP) were used in these experiments to study the effects of phosphorus on potato growth and phosphorus removal and transformation characteristics. Compared with common fertilizers, the findings provided a theoretic support basis for improving the processing techniques and for exploring the extensive utilization of CRFs. The research results were as follows:1. The nutrient release curves of CRFs in water showed a shape of parabola with a fastigium of release rate in the course of nutrient release. The release rate of phosphorus was slower than that of nitrogen in controlled-release-monoammonium phosphate (CRMP). After the release fastigium of phosphorus, the drop of release rate for phosphorus was slower than that of release rate for nitrogen.2. The effects of controlled-release-monoammonium phosphate (CRMP) in low (75 mg P2O5/kg soil) and high(150mg P2O5/kg soil)rates on phosphate fractions and phosphorus availability were investigated and the sorghum pot experiment were conducted for this study. The results showed that CRMP had higher phosphorus availability in soil and the changes ofavailable P concentration in both root zone and non-root zone soil were more reasonable during the sorghum growing season as compared to common monoammonium phosphate (CMP). Besides of uptake by the sorghum, the added phosphate mainly accumulated in the forms of Ca2-P, Ca8-P, and Al-P in soil. The amounts of Ca2-P, Ca8-P, and Al-P in soil with CRMP and CMP treatments were higher than that in soil of control. The amount of Ca2-P in soil with CRMP treatments increased from beginning to 100days then decreased from 100days to 150days, while the amount of Ca2-P in soil with CMP treatments decreased from beginning to 150 days. The increase of amount of Ca2-P in soil with high rate CRMP treatment was the highest among all the treatments. At the end of the experiment, the amount of Ca2-P in soil with CRMP treatments at both low and high phosphate rate was higher than that of CMP treatments, but the amount of Ca2-P in soil with CRMP treatment in low rate was almost same to that in high rate. The amount of Ca8-P in soil with CRMP treatments was lower than that of CMP treatments. The changes of the amount of Al-P, O-P, Fe-P and Ca10-P in soil were neglectable during the course of experiment.3. The shoot and root weight of sorghum increased through application of phosphorus, in addition, The increase of sorghum shoot and root weight was greater than that of common monoammonium phosphate (CMP) due to the slow release of nutrients from CRMP. The accumulative uptake of phosphorus in shoot and root with CRMP treatment was greater than that with CMP treatment in low (75 mg P2O5/kg soil ) and high(150mg P2O5/kg soil)rates, especially on middle stage, and in high phosphorus rate, this advantage was more obvious than that in low phosphorus rate. The accumulative uptake of phosphorus in shoot and root with CRMP treatment in low phosphorus rate was similar to that with CMP treatment in high phosphorus rate. In the same rate of nitrogen, potassium, calcium, magnesium, the accumulative uptake ofnitrogen, potassium, calcium, magnesium in shoot and root of sorghum with CRMP treatment was greater than that with CMP treatment.4. The effects of application of phosphorus with controlled-release compound fertilizers (CRCF) on availability of P in soil, the uptake of P in potato plant, the phosphorus use efficiency and potato yield were also investigated in this study. Two kinds of controlled-release compound...
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