| There are many problems in most agricultural production in China,such as high input,high consumption,heavy pollution and low output,The unequal ratio of production to investment seriously destroys the internal metabolism and circulation of nitrogen and phosphorus in nature,resulting in environmental pollution such as soil and lake.Due to its good physical and chemical properties and structure,and wide sources of raw materials,biochar has multiple benefits in increasing crop yield,realizing resource utilization of waste biomass,improving soil texture and fertility,reducing environmental pollution,and has become a research hotspot in many fields.Because of the difference of raw materials,the influence of different biochar on nitrogen and phosphorus is also quite different.Therefore,to explore the role of biochar made of new raw materials on nitrogen and phosphorus is conducive to enrich the research of biochar in agriculture and provide scientific basis for the realization of green and sustainable waste resources in the future.In the present study,two kinds of industrial wastes from tobacco factory and brewery and corn straw were used as raw materials of biochar,the raw materials were pyrolyzed at 450℃to make tobacco foam biochar（YM）,distiller’s grains biochar（JZ）and corn straw biochar（JG）.Then,the YM and magnesium silicate fertilizer were mixed and pyrolyzed again to make the modified biochar（M-YM）.Analysis of physical and chemical properties of four biochar.The adsorption characteristics of four kinds of biochar on nitrogen and phosphorus in water under different initial concentrations,different times and different pH conditions were studied through adsorption experiments.By adding four kinds of biochar with different proportions（0,1%,2%,4%）to the soil for indoor culture,we explored the changes of nitrate nitrogen,ammonium nitrogen and available phosphorus contents in the soil under different charcoal-soil ratio and different culture time.Four kinds of biochar were mixed with three kinds of nitrogen fertilizer（A1:urea;A2:urea+potassium chloride;A3:urea+potassium dihydrogen phosphate）,and the effects of four kinds of biochar on volatilization,volatilization rate,cumulative volatilization amount and volatilization rate of ammonia gas were analyzed.At the same time,four kinds of biochar were mixed with three kinds of phosphate fertilizer(（B1:potassium dihydrogen phosphate;B2:dihydrogen phosphate potassium urea;B3:potassium dihydrogen phosphate+potassium chloride）,and the effects of four kinds of biochar on the fixed amount and rate of phosphorus were analyzed.In the present study,by studying the effects of different biochar on the adsorption and availability of nitrogen and phosphorus in water and soil,we explored the feasibility of using waste materials from different sources in water pollution and soil nutrient fixation.And through the experiment of mixing with chemical fertilizer,in order to provide theoretical research for biochar to make hefei.The main results are summarized below:The adsorption capacity of nitrogen and phosphorus of the four biocharcoals all increased with the increase of the initial concentration,and the adsorption capacity of nitrogen and phosphorus was the largest at the initial concentration of 1000 mg·l-1.At this concentration,the adsorption capacity of nitrogen was 41.97 mg·g-1,43.427 mg·g-1,27.80mg·g-1,17.17 mg·g-1,and the adsorption capacity of phosphorus was 31.99 mg·g-1,27.14mg·g-1,22.52 mg·g-1,16.86 mg·g-1.The results of the isothermal adsorption curve fitting of nitrogen and phosphorus show that the adsorption of nitrogen and phosphorus by M-YM and JZ and the adsorption of phosphorus by JG are more consistent with the Langmuir equation.YM adsorption of nitrogen and phosphorus and JG adsorption of nitrogen are more in line with Freundlich adsorption equation.In the process of nitrogen adsorption,JG first reached the equilibrium state at 6h,while YM,M-YM and JZ reached the equilibrium at 8h,and the order of nitrogen adsorption effect at equilibrium was M-YM>YM>JZ>JG.In the phosphorus adsorption process,YM and JZ reached equilibrium at 8h,and M-YM and JG reached equilibrium at 12-24h.The adsorption effect of four biochar on phosphorus was consistent with that of nitrogen,and the order of size was M-YM>YM>JZ>JG.According to the adsorption and fitting data of the kinetic equation of nitrogen and phosphorus,compared with the pseudo-second-order equation,the adsorption of nitrogen and phosphorus by the four biochar more conforms to the pseudo-first-order equation.On the whole,when the pH of the four biochar is 2-11,the adsorption capacity of nitrogen and phosphorus increases first and then decreases with the increase of pH.The adsorption capacity of nitrogen and phosphorus is the largest when the solution is neutral and weak alkaline,and the adsorption capacity when pH is strong alkaline is greater than that when pH is strong acid.In the process of biochar and soil culture,the amount of biochar has a significant effect on the content of soil nitrate.In general,the greater the amount of biochar added,the higher the soil’s nitrate nitrogen content.After the 60th day of culture,the 4%addition amount of the four biochars was 13.26 mg·kg-1,12.9 mg·kg-1,2.31 mg·kg-1,3.28 mg·kg-1higher than the control treatment,respectively.The content of ammonium nitrogen in the soil supplemented with M-YM was significantly lower than that of the other three treatments during the entire 4%treatment period,and it was 61.19 mg·kg-1 lower than the control at the 60th day.The content of ammonium nitrogen in the soil added with JZ was significantly lower than the treatment with biochar added in the first 15 days,but from the 15th day,the control treatment was significantly higher than that with all biochar added.The content of ammonium nitrogen in the soil with 4%JG addition was significantly lower than the other three treatments in each cultivation time.In the 15 days before the cultivation,the content of ammonium nitrogen in the control treatment was significantly higher than that with the biochar added.Throughout the cultivation period,the order of the available phosphorus content in the soil of 4%added YM,JZ,JG was 4%added amount>2%added amount>1%added amount>control treatment.The order of effective phosphorus content of M-YM in the first 30 days of culture is:control treatment>1%addition amount>2%addition amount>4%addition amount;but when the culture time is 30-60 days,the effective phosphorus content order:4%added amount>2%added amount>1%added amount>control treatment.During the culture time,the ammonia volatilization of A1,A2,and A3 treated by YM,M-YM,and JZ increased first and then decreased.For JG,there was no ammonia volatilization in the A1,A2,and A3 treatments within 10 days before the culture.From the10th day,the ammonia volatilization amount increased slowly.The A1,A2,and A3 treatments of all biochars had significant differences in the cumulative volatilization of ammonia and all showed:A1>A2>A3.Comparing the cumulative ammonia volatility of the four biochars under A1,A2,and A3 treatments,it can be seen that the order of the cumulative ammonia volatility of the four biochars is:JZ>M-YM>YM>JG;The Elovich equation can better fit the trend of the cumulative ammonia volatilization and culture time of YM,M-YM,JZ,and JG fits better with Bangham equation.The order of ammonia volatilization rate of A1,A2,and A3 treated by YM is:A1>A2>A3,and the ratio of the three fertilizers shows a trend of ammonia volatilization rate increasing first and then decreasing with time.The volatilization rate of ammonia treated by M-YM and JZ in A1,A2,and A3 showed a trend of increasing first and then decreasing during all incubation times.From the 10th day of JG culture,the intermediate ammonia gas treated by A1,A2,and A3 was slowly released,and then the three fertilizer addition ratio treatments showed an increasing-decreasing-increasing trend with the increase of the culture time.Under the treatment of B1,B2,and B3,the amount of phosphorus fixation reached the maximum on the 5th day,and then the amount of phosphorus fixation decreased sharply with the increase of the culture time.Except for the B1 of YM,the fixed amount of phosphorus in the B1,B2 and B3 treatments of all biochar was the lowest on the 10th day.When the culture time was from the 10th to the 15th day,the fixed amount of phosphorus increased sharply,and reached another peak on the 15th to the 20th day,then the fixed amount of phosphorus tended to be stable.Different treatments of B1,B2 and B3 had little effect on the fixed amount of phosphorus in JZ and JG,but had great effect on YM and M-YM.Under the treatment of B1,B2 and B3,the order of phosphorus fixation rate of four biochar is:M-YM>YM>JG>JZ. |
