| Fertilizing soil quickly,increasing soil organic carbon,improving soil physical and chemical properties,and the capacity of water and fertilizer conservation are the keys to control desertification soil in alpine sandy regions of northwest Sichuan.Straw and spent mushroom substrate?SMS?are agricultural waste which is rich in organic carbon and nitrogen,phosphorus and potassium nutrients,at the same time they are also using as natural water and fertilizer conservation materials.Applying Straw and SMS to desertified soil can not only avoid environmental pollution and waste of biomass resources,but also effectively increase the soil organic carbon and improve soil fertility.In this study,straw and SMS were granulated respectively with PAM,microbial agents,nitrogen,phosphorus and potassium fertilizer by granulation machine.Through field experiment,blank control?CK0?,chemical fertilizer?CK1?and local conventional yak dung treatment?CK2?were used as control.Two kinds of amendment were set up:granulated straw amendment?JG?and granulated SMS amendment?JZ?,with four application rates:6,12,18,24 t·hm-2.The effects of JG and JZ on soil physical and chemical properties,carbon pool and ryegrass growth in sandy land and their long-term effects were studied.It provides theoretical basis and technical support for soil improvement and agricultural waste resource utilization in sandy land of northwest Sichuan.The main results are as follows:1.The application of chemical fertilizer,yak dung,JG and JZ all reduced the soil bulk density,increased the soil porosity,moisture and the content of large aggregates,and increasing the application of amendment can further improve the soil physical properties.The improvement effect of organic material amendment on soil physical properties was better than that of chemical fertilizer.the overall effect was JG>JZ>CK2>CK1,and the organic material amendment had long-term effect on soil bulk density,porosity and macroaggregates.2.The application of exogenous substances significantly increased soil total nitrogen,total nitrogen storage and nitrate nitrogen content,and with the increase of amendment application amount,soil nitrogen content increased significantly.The nitrate nitrogen content showed a trend of decrease with time,and the decrease of chemical fertilizer treatment was the largest which decreased by 96.2%in the second year compared with the first year.Organic material amendment had a long-term effect on the improvement of soil nitrogen,and effectively reduced the leaching loss of soil nitrogen.Compared with chemical fertilizer treatment,the leaching rates of exogenous nutrients in yak dung,JG and JZ treatments decreased by 81.5%,80.7%and 80.9%,respectively.Overall,JG was better than JZ.When the application of JG was 12 t·hm-2and JZ was 18 t·hm-2,the soil nitrogen content of the amendment treatment was significantly better than that of the conventional yak dung treatment.3.The application of chemical fertilizer,yak dung,JG and JZ increased the content of soil total organic carbon?TOC?,labile organic carbon?LOC?,microbial biomass carbon?MBC?,total carbon storage?TCS?and soil carbon pool management index?CPMI?in alpine sandy land.Take the second year for example,the TOC content of chemical fertilizer,yak dung,JG and JZ increased by 6.4%,65.2%,96.4%and 69.6%,respectively,compared with CK0.The LOC increased by 34.5%,49.6%,157.7%and 82.8%,respectively,and the MBC increased by 76.0%,691.1%,934.0%and 956.1%,respectively,and the TCS increased by5.5%,67.6%,100.1%and 66.7%,respectively,and the CPMI increased by 38.2%,41.4%,169.4%and 81.7%,respectively.The improvement effect of organic amendment was better than that of chemical fertilizers,and had a long-term effect on the improvement of soil carbon pool and CPMI,while chemical fertilizers could only be improved in the short term,not in the long term.Overall,JG amendment was better than JZ amendment.4.The application of chemical fertilizer,yak dung,JG and JZ significantly increased the basic seedling,plant height,chlorophyll content and dry weight single plant of ryegrass,and effectively promoted the root morphological development of ryegrass,and increased the population dry matter quality,and the addition of amendment significantly promoted the growth of ryegrass.In the short term,the effect of chemical fertilizer on the growth of ryegrass was obvious,but it had no long-term effect.The organic amendment promoted the growth and development of ryegrass continuously and effectively,and had a long-term effect.Overall,when the application of JG and JZ was 12 t·hm-2,the growth of ryegrass with the amendment was better than that of the conventional yak dung treatment.In conclusion,the application of exogenous organic amendment effectively improved soil physical properties,increased soil total nitrogen storage,total nitrogen and nitrate nitrogen content,increased soil total carbon storage,organic carbon component content and soil CPMI,and promoted the growth of aboveground vegetation.The improvement effect of sandy soil and the growth of aboveground vegetation increased with the increase of the applicationt of amendment applied.The application of organic material amendment had a long-term effect on improving sandy soil and promoting the growth of aboveground vegetation.According to the combination of soil improvement and aboveground vegetation growth,when the application of JG amendment was 12 t·hm-2and the JZ amendment was 18t·hm-2,the effect of the amendment on soil improvement in alpine sandy land was better than that of conventional yak dung. |
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