The Variation Characteristics Of Soil Phosphor In Weibei Loess Area

Phosphorus is one of the essential elements for plant growth and development, plants need phosphorus is mainly obtained from the soil phosphorus pool. In recent years, phosphate fertilizer was continuously put into the farmland in the loess area, the content of phosphorus was increased, and a huge potential of phosphorus pool was formed. But the effect of phosphate fertilizer production was gradually reduced. Excessive fertilization not only will cause a huge waste, but also bring harm to ecological environment. Therefore, the comprehensive management of phosphorus is key to coordinate the high crop yield and environmental friendly.In this study, there were six different fertilizers treatments and five different amount of phosphorus application treatments in the experiment on the basis of 30 years. The six different fertilizers treatment were included without fertilization, nitrogen, phosphorus, manure, nitrogen and phosphorus, nitrogen phosphorus and manure;and five different rates treatments 0,45 kgP2O5/ha,90 kgP2O5/ha,135 kg kgP2O5/ha,180 kgP2O5/ha. The research based on 0-200 cm of soil profile studied influence of different fertilizations with soil productivity; studied accumulation and spatial distribution of soil inorganic phosphorus and organic phosphorus in long-term fertilization; studied soil available phosphorus in different fertilization. Draw the following main conclusions:i The content of soil nutrient are reduced under without fertilization application, leading to soil productivity decline. Wheat yield is maintain a certain level without fertilizers, and with the depletion of soil nutrients, yield of wheat is about 1450 kg/ha. Soil nutrient keep an imbalance, and can not only improve soil productivity, under nitrogen fertilizer and phosphate fertilizer application for a long term. Soil nutrient can keep a balance under organic fertilizer, nitrogen and phosphorus and nitrogen phosphorus and organic fertilizer. Soil fertility can improve soil productivity, the yield of wheat reached increased extremely significant. With the increase of fertilizer, the yield of wheat is not increased but reduced,ii Under phosphorus fertilization application of soil, the content of different forms of inorganic phosphorus are showed:Ca10-P>O-P>Cag-P>Al-P>Fe-P>Ca2-P. Increment of inorganic phosphorus fractions in soil profile is different, with phosphorus fertilizer and the years increased. The increment of Ca2-P, Cag-P, Al-P profile is gradually decreased with the increment of soil depth to 2011 year. The increment of Ca10-P and O-P soil profile was showed "S" type distribution. The total organic phosphorus is increased with phosphorus fertilizer increased. Organic phosphorus content is mainly moderately labile organic phosphorus, followed by the moderately resistant organic phosphorus, high resistant organic phosphorus, and labile organic phosphorus. Along with the increment of phosphorus fertilizer, organic phosphorus fractions in soil profiles is different in different years, labile organic phosphorus in the soil profile in the downward trend, and the resistant organic phosphorus and highly resistant organic phosphorus in soil profile distribution showed "S" type, moderately labile organic phosphorus had no obvious rule.iii The forms of inorganic phosphorus content are increased with fertilizers application for a long-term. But the effects of long-term fertilization on soil inorganic phosphorus is greater than organic phosphorus. In different fertilization treatments, the content of Ca2-P and Cag-P in soil were mainly accumulated in 0-60 cm soil layer, topsoil is larger than the bottom,60-200 cm remained unchanged. The content of Al-P and Fe-P is similar to the vertical mobility of small, mainly accumulated in 20-60 cm. The content of O-P is decreased in the profile, Ca10-P is relatively stable. Labile organic phosphorus in the soil profile in the downward trend, the resistant organic phosphorus and highly resistant organic phosphorus showed "S" type distribution in the soil profile, moderately labile organic phosphorus content in the profile is not obvious regularity.iv The content of the soil total phosphorus, available phosphorus and soil microbial phosphorus of Alfalfa rotation is in inverse proportion to alfalfa growth years. The longer the alfalfa growth years, the lower soil total P, available P and soil microbial biomass phosphorus content. Alfalfa soil inorganic phosphorus fractions in the soil profile is mainly in Ca-P. Soil inorganic phosphorus in O-P state accumulated in the soil with long term fertilization, Caio-P is difficult to be utilized by crops. Organic phosphorus content is mainly in labile organic phosphorus, organic phosphorus content in labile and moderately labile accounted for the total organic phosphorus decreases with the increase of growth years, changes in moderately resistant and highly resistant organic phosphorus is relatively stable.v Ca2-P, Ca8-P and labile organic phosphorus is the main source of available phosphorus; Al-P, Fe-P and O-P can be transformed into Ca2-P, and Cas-P indirectly become available phosphorus by crops using; Ca10-P, moderately labile organic phosphorus, moderately resistant organic phosphorus and highly resistant organic phosphorus on soil is smaller contribution to available phosphorus; Moderately resistant organic phosphorus and highly resistant organic phosphorus can be transformed into labile organic phosphorus. Ca2-P is the best available phosphorus absorption of crops, Ca10-P least used by crops. Phosphorus fertilizer application in soil mainly performance for the Ca2-P and Ca8-P two forms. Ca8-P is converted to Ca2-P, and the indirect effects of available phosphorus content. The occluded O-P was finally broken down and used by crops. Organic phosphorus in soil must be converted into inorganic phosphorus by mineralization then to be absorbed by the plant.vi The treatment without phosphate fertilizer for long term, soil P reserves gradually reduced, results in the soil of phosphorus depletion. Phosphate fertilizer can improve soil phosphorus availability, increase the available phosphorus content, so that an accumulation of available phosphorus in the topsoil.But the storage capacity of available phosphorus in the soil is not increased with increasing amount of fertilizer application, and to maintain a certain level of phosphorus in soil, to achieve balance between supply and demand. The farmland in the Loess Area the available phosphorus stored in the soil of 4.8 to 5.24 kg/(ha y), excessive fertilization can increase soil organic and inorganic phosphorus content, and not increase the. soil available phosphorus pool.