Effects Of Long-Term Fertilization On Phosphorus And Its Fractions In Aggregates Of Fluvo-Aquic Soil

Phosphorus is one essential macroelement to plant growth and development, and is the absolutely necessarity nutritional element of plant in the life cycle,, o but also has significant effect on keeping high productivity of crop and the good characteristic of crop cultivars.The plant P requirement is mainly from the soil.As an important component of soil phosphorus pool,soil organic P has important effect on the soil fertility and plant nutrition,thus its role on plant has been paid more and more attention to.In this study, a Fluvo-aquic soil was taken to evaluate phosphorus forms in combination with soil aggregates in order to provide theoretical basis and practical method for the forms and location of phosphate, and to provide scientific basis for rational use of phosphate. The results showed that:1. Composition of soil aggregates:The highest content in soil aggregates composition is the aggregates of 0.25 mm-5 mm, ranging from 60.72%-77.98%of the gross weight, followed by the aggregates of>5 mm, ranging from 11.90%-25.82%, and the lowest content for<0.25 mm, ranging from 7.09%～13.68%.The principal part is 0.25 mm-5 mm,long term fertilizer would decrease the content of small size of aggregates in Fluvo-aquic soil.2. Changes of soil organic phosphorus(OP):The increased application of P can increase the organic phosphorus and inorganic phosphorus content of the soil, and the organic manure was the most effective way to increase organic phosphorus content fluvo-aquic in soil. Compared to MNPK,1.5MNPK contain 50%more phosphorus, while only 12.9%more organic phosphorus content, it indicates that the continuous application of organic manure up to a certain level have limited effect to increase Fluvo-aquic soil organic phosphorus. Organic manure used in conjunction with straw can significantly increased levels of inorganic phosphorus, and has better effects than the application of alone organic fertilizer.3. Changes of soil inorganic phosphorus(iP):In Fluvo-acquic soil, among the fractions of organic phosphorus the ML-OP content is the highest with largest proportion, followed by MR-OP. While L-OP and HR-OP have the smallest content and proportion. As ML-OP is the main fraction, its content in different treatments varied from low to high, so ranked as CK5mm of 1.5MNPK, that is 88.36%, indicating that organic manure increase in macro aggregate organic phosphorus is most significant.In the same treatment, different fractions of organic phosphorus and total organic phosphorus variation have shown similar trends. From big to small particles, different components have different degrees of organic phosphorus increase. The total phosphorus of three aggregates contents was found almost identical, indicating that the distribution of total phosphorus in the aggregates is more stable and free from the impact of aggregate particle size, making it different from organic phosphorus. The variation tendency of available P in different aggregates is similar, this can be because L-OP and ML-OP are two major component of available phosphorus, therefore L-OP and ML-OP influence the available phosphorus more noticeable.5. Changes of available phosphorus(AP),inorganic phosphorus(iP)and its fractions in Fluvo-aquic soil aggregates with different sizes:In each treatment, the available phosphorus content order from high to low in succession was 1.5MNPK, MNPK, MNPK2, sNPK, NPK, CK. The available phosphorus content of fertilization treatment was significantly higher than CK. Inorganic and organic manure combination can significantly increase soil available phosphorus content. And analyzing the relativity and path can indicate that the major source of available phosphorus mainly is L-OP,ML-OP and MR-OP, and the ability of plants to use inorganic phosphorus is in order of Ca2-P> Ca8-P> Al-P> Fe-P> OP≈Ca10P,Plants mainly use Ca2-P, Ca8-P, Al-P, Fe-P, that are four inorganic fractions in fluvo-aquic soil, these four higher effective fractions are only 22.3%-49.9%of the total phosphorus. Therefore more than half of the inorganic phosphorus is almost ineffective in fluvo-aquic soil. In the long-term fertilization of inorganic phosphorus, the most important component to provide available P is Al-P, followed by Ca8-P.6. Distribution of total phosphorus(TP), organic phosphorus(OP) and inorganic phosphorus(iP) in different Loess soil aggregates:The main part of fluvo-aquic soil aggregate is 0.25-5mm, in the case of the same treatment, compared to CK, the organic an inorganic phosphorus content of all the aggregate have different extents of increase, among which>5mm have the biggest organic phosphorus increase, and the biggest inorganic phosphorus increase is in 0.25-5mm aggregates. Different fractions of organic phosphorus and available phosphorus have broadly similar trend with total organic phosphorus, and total phosphorus was rather stable, and was not subject to the influence of aggregate size. The distribution of inorganic phosphors in fluvo-aquic soil aggregates mainly decided by the aggregates content, and distribution of organic phosphorus showed a similar phenomenon.