Phosphorus Status Of Cinnamon Soil And Its Loss Risk Assessment Under Long-term Fertilization

In order to explore the phosphorus accumulation characteristics and accumulation of soil phosphorus loss risk in cinnamon soil under the long-term application conditions, cinnamon soil phosphorus content, composition, ratio, soil phosphorus transformation related enzymes, microorganisms were studied in this paper by24years long-term fertilization trials, set up by8treatment models, which are:no fertilizer treatment (CK), only nitrogen fertilizer (N), nitrogen and phosphorus co-applied (NP), low amount of organic manure (M1), low amount of organic manure and nitrogen fertilizer (M1N), low amount of organic manure and nitrogen and phosphorus co-applied (M1NP), high amount of organic manure and nitrogen (M2N), high amount of organic manure and nitrogen and phosphorus co-applied(M2NP). The statistical analysis of the relationship between soil phosphorus forms and the evaluation of the risk of soil phosphorus loss were also studied. The results showed that:1In24years time, the soil total phosphorus and available phosphorus content show a downward trend in both CK and N. The soil total phosphorus and available phosphorus content of CK decreased by0.246g/kg and1.89mg/kg, while the N treatment decreased0.300g/kg and2.16mg/kg. In the case of no phosphate application, available phosphorus is close to depletion state.2The cinnamon soil phosphorus accumulation mainly affected by the amount of phosphate application, and it has little to do with the type of fertilizer and the mode of administration. With the increase of phosphorus application rate, the phosphorus accumulation increased, and it was tending to accumulate exogenous phosphorus easily. After24years of continuous fertilization, the soil total phosphorus content of the six treatments with exogenous phosphorus application was M2NP>M1NP>M2N>NP>M1>M1N, with an increase of50.3%,37.6%,28.0%,19.6%,19.3%respectively compared with prior the test. The available phosphorus content of the six treatments with exogenous phosphorus application also increased, in turn were 41.0times,20.2times,18.5times,16.5times,16.4times and11.4times compared with the prior the test. Whether the treatment was applied organic fertilizer applied or chemical fertilizers applied or organic and inorganic co-applied, the accumulated phosphorus in cinnamon soil was mainly by inorganic phosphorus with a based form ofCa10-P.3The long-term fertilization test shows that, alkaline phosphatase activity, solubilizing bacteria number and microbial biomass phosphorus content were affected by fertilizer application in cinnamon soil. Compared with the CK, alkaline phosphatase activity of others treatment increased in varying degrees, and the organic fertilizer was more effective than nitrogen fertilizer and phosphorus fertilizer. The number of soil phosphorus bacteria and content of microbial biomass phosphorus of N treatment were decreased compared with CK treatment after long-term fertilizer application. Solubilizing bacteria in cinnamon soil was sensitive to exogenous phosphorus for the right amount of exogenous phosphorus was conducive to the breeding of solubilizing bacteria. After24years, in the six treatments with exogenous phosphorus application, M1NP hold the maximum organophosphorus bacteria number, which increased52.8%compared with the CK, while M2N holding the maximum inorganic phosphorus bacteria number with an increase of67.5%.4The content of the various forms of soil phosphorus closely in the soil related with available phosphorus. As the main source of available phosphorus, the respectively correlation coefficient between the Ca2-P and Cag-P content with available phosphorus content could achieved0.9652and0.9521. However, Ca3-P content was mainly indirect effects to available phosphorus and the direct effect was small. Al-P, Fe-P, labile organic phosphorus and medium labile organic phosphorus to soil available phosphorus also had certain contribution, and medium stability of organic phosphorus and high stability of organic phosphorus to soil available phosphorus was relatively small, while Ca10-P and O-P had negative effect of the contribution.5After long-term application of organic manure and phosphate, the risk of phosphorus losses increased in cinnamon soil, especially in the treatments of organic manure application which risk increased with the phosphorus application rate increasing. The risk of phosphorus loss of M2NP was very large as the soil phosphorus saturation was more than25%in2011and reached61.39%in2012. The soil phosphorus saturation of M1NP reached the threshold of25%in2012also had a great loss risk. There was a certain loss risk in M1, M1N and M2N for their soil phosphorus saturation at around20%, while the soil phosphorus saturation of CK and N treatment were only2.53%and1.09%, there might no risk of loss.