Preparation Of Straw Carbon Based Slow Release Compound Fertilizer And Its Effect On Crop Growth

The application of chemical fertilizers(CF)has been increasing globally year by year,however,there are problems such as high dissolution rate,rapid nutrient loss,and mismatch between nutrient release characteristics and plant demand,resulting in lower effective utilization rate.In addition,the long-term fertilization method of"chemical fertilizers over organic fertilizers"does not allow humus to be replenished in time,causing soil consolidation,soil degradation and micro-ecological damage,which has seriously restricted the sustainable development of modern agriculture.Therefore,in order to balance the comprehensive effects of crop yield,quality and environment,and to promote the"reduction of fertilizer application and increase of efficiency",it is urgent to develop new green,nutrient-balanced slow-release fertilizers to improve the effective utilization rate of fertilizers and improve the soil environment at the same time.Based on this,this study used functionalized wheat straw biochar as a carrier to prepare straw biochar-based slow-release compound fertilizer by blending and granulation of nitrogen and phosphorus inorganic nutrients and anaerobically digested digesting digesting residue/pig manure organic fertilizer;the basic physicochemical properties and slow-release performance of the above compound fertilizer were systematically studied;three typical model plants were selected and compared with traditional chemical fertilizers to investigate The effects of the above compound fertilizers on the germination and growth of lettuce,soybean and corn were investigated by comparing them with traditional chemical fertilizers;the costs of chemical fertilizers and the above compound fertilizers and the economic benefits of applying them to different crops were statistically analyzed.The results of the study were as follows:(1)Physicochemical indexes of biochar-based slow-release compound fertilizer(BCF)containing digestate and its effects on lettuce growth:(1)Biochar-based slow-release compound fertilizer containing digestate was prepared by blending method,and its basic physicochemical indexes were investigated.The results showed that the p H of BCF was 5.65,the N and P contents were 6.7%and 15.3%,the total nutrient content was 27.5%,and the organic matter content was 46.08%,all of which were in accordance with the National Standard of GBT18877-2020 Organic Inorganic Compound Fertilizer;BCF had Excellent slow release performance,the N and P release rate at 50 h,respectively,is 44.26%and 59.74%lower than that in chemical fertilizers.(2)The results of germination tests showed that the root length of lettuce in the BCF treatment group increased by 61.18%on average,germination potential by 13.33%,germination rate by 8.57%and germination index by 24.76%compared with CF,indicating that BCF can effectively promote the germination of lettuce seeds.(3)The results of lettuce pot trials showed that BCF had a significant growth-promoting effect on lettuce,and the indices of lettuce in the BCF group were generally higher than those in the blank control group,CF treatment,biogas treatment alone and biochar treatment alone.In particular,compared with CF,the BCF treatment group significantly promoted the growth of lettuce at the same fertilizer application rate,although the nitrogen content in BCF was halved.The above-ground fresh weight of lettuce increased by 33.2%,plant height increased by 18.5%,root length increased by 40.4%,leaf number increased by8.3%,chlorophyll content increased by 32.5%,and net photosynthetic rate increased by103.1%,and the BCF application rate of 2 g/pot had the most obvious effect on lettuce growth promotion.(2)Physicochemical properties of granular pig manure compound fertilizer(GPCF)and digestate compound fertilizer(GBCF)and their effects on crop growth:(1)GPCF and GBCF prepared by granulation method,the basic physical and chemical index test results show that:granular fertilizer with particle size between 1.4 mm-4.3 mm,granulation rate>80%;organic matter is>40%,total nutrients>15%,N/P/K and other single nutrients are>3%,p H>5.5;the above indicators are in line with GBT18877-2020organic inorganic compound fertilizer National Standard".In addition,the seed germination index of the 2 granular fertilizers was>50%,and the production of GPCF and GBCF was tentatively judged to be feasible.(2)The germination test results showed that the root length of corn treated with GPCF and GBCF increased by 16.56%and 21.37%,germination potential increased by 5.88%and 11.76%,germination rate increased by 11.11%,and germination index increased by2.92%and 8.26%,respectively,compared with CF;the root length of soybean treated with GPCF and GBCF increased by 15.5 times and 22.2 times,respectively,compared with CF group,germination potential increased by 100%,germination rate increased by 81.82%,and germination index increased by 195.64%and 202.38%,respectively.GPCF and GBCF treatments increased root length by 15.5 and 22.2 times,germination potential by 100%,germination rate by 81.82%,and germination index by 195.64 and 202.38%,respectively,compared with the CF group.GPCF and GBCF significantly promoted seed germination mainly because of the good slow-release properties of granular fertilizer,which slowed down the release of nitrogen and phosphorus nutrients,thus reducing the inhibitory effect of salt stress effect on seed germination.(3)The results of slow release performance of GPCF and GBCF showed that GPCF and GBCF had excellent slow release performance of nitrogen and phosphorus,and after 48 h of slow release,the cumulative release rates of GPCF on nitrogen and phosphorus were reduced by 67.6%and 68.9%,respectively,compared with that of chemical fertilizer(CF);the cumulative release rates of GBCF on nitrogen and phosphorus were reduced by 66.7%and 63.6%,respectively,compared with that of chemical fertilizer(CF).Preliminary studies on the slow release kinetics showed that the release process of both granular fertilizers on N and P was subject to the synergistic control of multiple steps,mainly dissolution,desorption and diffusion.(4)The results of soybean and maize pot experiments showed that the application of GPCF and GBCF were more effective in increasing plant height,stem thickness,root length,leaf area,aboveground dry matter accumulation and chlorophyll fluorescence parameters in both soybean and maize compared to the CF group with equal N content.Application of GPCF and GBCF also significantly promoted all growth parameters of soybean and maize when N content was reduced by 30%and 50%compared to CF.(3)GPCF and GBCF economic benefit analysisCompared with CF,the application of GPCF and GBCF can reduce input costs to obtain higher economic benefits at the same acreage of soybean and corn,planting soybean can increase net income by 502.5 yuan/hm~2and 784.5 yuan/hm~2,respectively:planting corn can increase net income by 603 yuan/hm~2and 1026 yuan/hm~2,respectively.In summary,biochar-based slow-release compound fertilizers can significantly improve crop yield and quality in reduced amounts,and have greater potential for application in improving the slow-release capacity and effective utilization of fertilizers,resource utilization of straw,reducing fertilizer application and increasing efficiency,as well as promoting sustainable agricultural development.