Impact Of Biochar On Availability Of Phosphorus In Different Soil Types

The biochar is a highly aromatic refractory and solid material that is produced by the pyrolysis andcharring of plant biomass in the case of complete or partial absence of oxygen. The materials ofbiochar includes wood, bamboo, straw, rice husk. The biochar contains rich mineral nutrient elementssuch as phosphorus, potassium, calcium, magnesium and nitrogen, which are applied to the soil that canincrease the nutrient content of the soil. Among them, phosphorus is the necessary nutrients for cropgrowth, it is part of many important compounds and also indispensable part of the growth andmetabolism for plants. Compared with other nutrients, phosphorus is a non-renewable resources, hasbecome a limiting nutrient elements of the terrestrial and marine ecosystem productivity. Therefore, thefull and rational use of existing phosphate fertilizer resources is of great significance to maintain thephosphorus cycle.In this study, through selecting corn stalk as materials of biochar, in view of the recycling use ofphosphorus in the fields, focusing on studying the effects on of phosphorus availability in different soiltypes and in the soil applied external phosphorus. And the mechanism of effects of biochar onphosphorus in the soil and external phosphorus were discussed.The specific findings are as follows:（1） Study the elemental composition, morphology, physical and chemical properties of biochar atvarious pyrolysis temperatures （300℃,400℃,500℃）. When the pyrolysis temperature is at400℃,the phosphorus content, pH, the conversion rate of biochar is moderate, and its layered structure isobvious.400℃biochar is better than two other biochars in conversion rate of biochar, improving soilfertility and ameliorating soil environment.（2） The application of2%,4%and8%of biochar in red soil, paddy soil, cinnamon soil, alluvialsoil can significantly improve soil Olsen-P content, especially in the cinnamon soil and alluvial soilplays a better role in promoting the availablity of phosphorus. And Olsen-P content in red soil, paddysoil, cinnamon soil, alluvial soil and biochar application rate reached a significant positive correlation.But CaCl₂-P content in the soil increased with biochar application rate increases, also showedsignificant positive correlation. Therefore, biochar application rate should be in the reasonable control,which is to reduce environmental risks that due to the increase of the CaCl₂-P content in the soil appliedexcessive biochar.（3） Through the analysis of influence factors of biochar on availablity of soil phosphorus, itshowed that after the application of biochar, soil conductivity and microbial biomass phosphorussignificantly increased, however, soil phosphatase activity is significantly reduced. So it can be seen thatalong with application of biochar, the increasing on content of Olsen-P and CaCl₂-P in the soil mainlydue to conversion of phosphorus in biochar itself. And through comparative studies, showed that whenthe application of biochar which was removed the ash, the increasing on the content of Olsen-P andCaCl₂-P is significantly lower than before.Therefore, Ash of Biochar is an important part for improvingavailablity of phosphorus in soil. （4） The indoor soil cultivation experiments were applied with exogenous phosphorus and differentapplication rate of biochar show that, biochar plays a role in promoting availablity of exogenousphosphorus in the red and paddy soil, and have inhibitory effects on CaCl₂-P content in red soil. But theCaCl₂-P content in paddy soil increased with biochar application rate increases in soil. Biochar inhibitedthe Olsen-P transformation of exogenous phosphorus in cinnamon soil and alluvial soil, but it improvesCaCl₂-Pcontent in cinnamon soil and8%treatment of alluvial soil.（5） Through study on the impact of biochar on both availablity of soil phosphorus and exogenousphosphorus, we found that biochar can not only be used as additives to improve the Olsen-P in the soil,it also can increase availablity of exogenous phosphorus in red soil and paddy soil.