| With the development of livestock and poultry breeding industry and the increasing consumption of meat,the total amount of animal bones in livestock and poultry farming has increased annually.Animal bones contain a lot of nutrient elements such as calcium,phosphorus and potassium,and there is a large number of animal bones abandoned and landfilled every year,causing a huge waste of resources.How to achieve the recycling of animal bones is important to reduce the waste disposal in livestock and poultry farming.The biomass pyrolysis technology is a safe,low-carbon and green engineering technology that can eliminate pathogens and destroy the structure of organic pollutants while it can preserve the beneficial components of biomass.This technology provides a new and sustainable approach to agricultural biomass waste disposal.The current study used the kitchen waste bovine bones to produce biochar through the biomass pyrolysis technology at 500℃,600℃ and 700℃,analyzed and evaluated its physicochemical properties and the possible improvement on soil phosphorus cycle;The typical vegetable soil in Southern China was selected,through simulated leaching test to study the phosphorus leaching in the bone char and chemical fertilizer treatments at the same phosphorus input level.Phosphorus of bovine bone char leaching can be used instead of a chemical phosphate fertilizer,providing an effective way to preserve soil phosphorus and reduce the risk of non-point source source pollution;Pot experiments of Pakchoi was designed to study the effects of bovine bone char.Therefore various kinds of chemical phosphate fertilizer and bovine char were used to calculate the phosphorus uptake and the soil phosphorus fractions transfer in the typical vegetable soil to verify the feasibility of bone char in agriculture,and provide scientific basis for livestock and poultry bone recycling.The main findings of this paper are as follows:(1)The black-brown bovine bone char obtained by pyrolysis carbonization has a yield of more than 50%and an average specific surface area of 111 m2/g,which is much higher than that of bovine bone(1.44 m2/g).The pores in bone char are mainly mesopores(2-20nm)that can be accounted as nanomaterials.High temperature increases the aromaticity of bovine bone char,forming more stable carbon.The tested biochar was weakly alkaline,the CEC was at 50 cmol/kg,the organic carbon content was between 6.5%～8.1%,and the total nitrogen was between 0.7%～1.4%,while both of them were reduced with the carbonization temperature.The total phosphorus content was as high as 14.5～16%,while 2%of formic acid led to phosphorus leaching of 7%～10%.The nutrient content of biochar obviously has the potential to improve soil fertility,especially by increasing the phosphorus content.Therefore,it can be a potential phosphate fertilizer source for low in phosphorus acidic soil.(2)With the change of leaching time,the total phosphorus concentration in the leachate is following the order of Diammonium hydrogen phosphate(DHP)>Calcium superphosphate(CSP)>Bovine bone char(BC)≈CK,under the same amount of phosphorus input.The trends of the total dissolved phosphorus(TDP),particulate attached phosphorus(PP)and total phosphorus(TP)concentration were basically the same under each treatment.The change of total phosphorus leaching in soil under different treatments was also following the order of DHP>CSP>BC≈CK,with a variation of 43～320mg/kg,the latter being without phosphorus input in CK.The DHP had the highest total amount(320 mg/kg),followed by the CSP treatment(156 mg/kg).There was no significant difference in the leaching loss between the bovine bone char and the CK.After 45 days of leaching,the application of phosphorus significantly increased the total phosphorus content.More specifically,the treatments of DHP,CSP and bovine bone char increased by 16%,35%and 48%,respectively.The content of Olsen-P was significantly higher under each phosphorus treatment.The Olsen-P content of CSP and BC treatment were about 20%higher than that of CK,while in the treatment of DHP it was 11%higher than CK.The continuous extraction of soil phosphorus fractions after leaching showed that chemical phosphate fertilizer treatment increased the active phosphorus fractions,however it had no significant effect on the soil stability of the phosphorus fractions.The soil activity,medium activity and stability of the phosphorus fractions were all increased under the treatment of BC.(3)Compared with chemical phosphate fertilizer,the pH of soil applied by Bovine bone char increased by 0.5 unit,the cation exchange capacity increased by about 10%,and the total nitrogen of soil increased by 4%;the application of Bovine bone char increased the yield of Pakchoi(between 5 and 30%)and the quality was improved;the root-shoot ratio of BC is significantly reduced(>45%),and phosphorus utilization rate is increased more than 20%.These effects are achieved with pyrolyzed Bovine bone char at 700℃.Meanwhile,the soil acid phosphatase activity increased by 37%,and the soil active phosphorus fraction and acid-soluble phosphorus fraction increased by 20%and 25%,respectively.Therefore,the animal bone char in domestic waste can be used for phosphate fertilizer instead of the chemical phosphate fertilizers,and can contribute to the high-yield and high-quality production of vegetables.Appropriately by raising the temperature more phosphorus efficient biochar can be obtained. |
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