Production Of Biochar-based Potassium-released Fertilizer And Its Application On Agriculture

In our country’s agricultural production,the main supplementary way of soil available potassium is using chemical potash fertilizer.According to information,Chinese potash fertilizer production accounts for only 0.34 percent of the world,while consumption has accounted for 14.7 percent.Although the country imports 200 million tons of potash per year,it still cannot meet the needs of agricultural production of potash.The content of soil potassium in our country is rich,but 95 percent is mineral,and mainly exists in feldspar and mica.The content of available potassium which can be absorbed by the plants directly is less than 2 percent of total potassium.Therefore,it has important theoretical and practical significance for agricultural production to study how to promote the release of soil mineral potassium.Bacillus mucilaginosus has an ability to decompose soil silicate minerals,and it is often used as microbial fertilizer in agricultural production.As a kind of microbial fertilizer,its agents can colonize in the rhizosphere soil and maintain a higher survival rate,is the important factor of the artificial inoculation agents can improve the yield and quality of crop or not.Being charred from biomass by pyrolysis(350-500℃)under complete or incomplete absence of oxygen condition,biochar is a highly aromatic and low density carbonized solid matter with infusibility.It has rich pores,which from nanometers to tens of microns,and this structure provides attachment sites and a larger living space for microorganisms.It also contains a certain amount of decomposable organic matter,which can provide carbon and nitrogen source for the growth of microorganisms;however,there are differences in the characteristics of biochar,which has different materials to produce,and the high pH of biochar may have adverse effects on the survival of microorganisms.Therefore,we attempt to adjust the properties of different materials’ biochar for selecting the suitable biochar carrier,and then compound the carrier and Bacillus mucilaginosus to produce biochar-based potassium-released fertilizer,finally,making further improvement on the efficiency of releasing soil insoluble potassium.Field experiments were exploded to investigate the effects of biochar-based potassium-released fertilizer on the yield,quality of tomato and potato.The main conclusions are as follows:(1)The survival rate of Bacillus mucilaginosus which inoculate in the neutral biochar had been improved significantly,compared to non-neutral treatments.Up to 35d,the viable count magnitude of neutral biochar was about 105～106,while the untreated was about 102.Compared with neutral rice shells biochar,peanut shells biochar and corn stalks biochar,the viable count number of neutral wheat straw biochar(NWB)was the highest,there were still 6.4×106 cfu·g-1 biochar until 35d,during the culture period.At the same time,the content of various nutrient of NWB had relatively higher than other biochar,and it had bigger specific surface area,so NWB could be used as the best carrier for Bacillus mucilaginosus.(2)The biochar-based potassium-released fertilizer(BC+M)could improve the content of soil available potassium;meanwhile,biochar as carrier could significantly increase the survival rate of bacillus mucilaginosus in soil.From the beginning to the 35d,the colony number of BC+M reduced from 1.0×109cfu·g-1 soil to 1.4×107cfu·g-1 soil,while bacterial liquid(M)reduced to 9.0×105 cfu·g-1 soil.Compared with the initial content of soil available potassium of each treatment,the content of soil available potassium of BC+M improved 23.08%,while M increased only 13.52%.(3)The results showed that the biochar-based potassium-released fertilizer(BC+M)could increase the yield of tomato,and improve the quality of tomato fruit.The yield,the content of vitamin C,and the content of plant and fruit total potassium of BC+M were higher than neutral wheat straw biochar(BC)and bacterial liquid(M);BC+M had the lowest content of nitrate,was 72.49 mg·kg-1,it was reduced by 5.48%,25.14%and 19.63%,compared with CF(compound fertilizer),BC and M.(4)The biochar-based potassium-released fertilizer(BC+M)could improve the yield and single fruit weight of potato,and improve the quality of potato,significantly.BC+M had the highest yield,which was 22.09 t·hm’2,increased by 16.57%～25.87%;BC+M had the highest single fruit weight,which was 170.79g,increased by 10.42%～30.17%;BC+M had the highest content of starch,which increased by 4.99%.