Effects Of Long-term Fertilization On Soil Microbial Characteristics In China Based On Meta-analysi

The microorganisms in soil participate in various biogeochemical cycles and play an important role in soil biochemical processes,which can sensitively reflect soil health quality.In human agricultural practice,long-term excessive fertilization has a significant impact on soil microbial properties and ecological environment.However,the influence of long-term fertilization on microorganisms is mostly site studies,and its influence on microbial properties in greater scope is still not clear,which need a comprehensive analysis of the impact of microbial properties in long time series to provide sustainable agricultural development strategies.In this study,6,211 data from 109 long-term stations were collected through the literature databases of CNKI and Elsevier Science Direct and Web of science,with the time period from 1978-2021 and the keywords "fertilization","microbial" and "enzyme activity".By means of Meta-analysis,The effects of fertilization treatments(nitrogen fertilizer,nitrogen,phosphorus and potassium,nitrogen,phosphorus and potassium combined with straw,nitrogen,phosphorus and potassium combined with manure),fertilization duration,climatic conditions and soil texture(sandy loam,silty loam,clay loam)on soil microbial properties(including microbial biomass carbon,microbial biomass nitrogen,Shannon index,PLFA,bacteria,fungi,actinomycetes,urease,catalase,invertase and phosphatase).The main results are as follows:1.Compared with the control group,long-term fertilization had significant effects on soil microbial properties.Among these,the effect sizes of MBC and MBN increased by 35% and63%,respectively.The PLFA was increased by 37%.Bacteria,fungi,and actinomyces increased by 65%,62%,and 73%,respectively.Urease,invertase,and phosphatase activities were significantly increased,at 47%,39%,and 28%,respectively.However,the Shannon index and catalase activity showed smaller increases by 3% and 2%,respectively.2.From the perspective of the four fertilization types,chemical fertilizer combined with organic fertilizer could significantly increase the effect size of microbial properties.Compared with the control group,MBN,PLFA,fungi,actinomycete,urease,catalase and phosphatase increased the most under NPKM,increasing by 111%,110%,88%,97%,77%,15% and 58%,respectively,and the least under N.They were 19%,-7%,43%,44%,25%,-11% and 4%respectively.Bacteria increased by up to 123% under NPKM treatment and by up to 33% under NPK treatment.The effect size of MBC increased by 77% under NPKS and 8% under N.Shannon index increased by the highest 5% and the lowest 1% under NPKS.3.The effects of long-term fertilization on soil microbial properties were different in different climate regions.In arid regions,microbial properties usually increased the most after fertilization compared to control.The increase of MBC reached the highest value of 125.3%under NPKM in arid region,and only 0.016% under N.The Shannon index varied the three humid regions,reaching the highest value of 6.95% under NPKS in semi-arid regions.PLFA increased more in arid regions,reaching 180.47% under NPKM and 10.65% under N,while negative growth of-10.74% and-9.07% under N in semi-arid and humid regions,respectively.In arid areas,MBC increased 2.23 times under chemical fertilizer combined with organic fertilizer compared with NPK,and 1.77 times under straw combined with chemical fertilizer compared with NPK,while MBN in humid areas increased 2.83 times compared with NPK under NPKM.Under the NPKS,the increase was 2.88 times.In semi-arid areas,NPKM increased the number of bacteria,fungi and actinomycetes the most,which were 142%,97%and 118%,respectively.MBC,MBN and Shannon index increase in the semi-arid region until reaching the peak in 20 years,and then the growth rate gradually decreased.PLFA increased the most in the first 10 years of cultivation in arid region,while the peak value in semi-arid and humid regions was delayed after 17 and 20 years of fertilization,respectively.4.The effect size of long-term fertilization on microbial properties was significantly different under different soil texture conditions.Compared with no fertilization,the microbial properties in sandy loam reached its peak earlier.MBC reached its peak after 15 years in sandy loam,but extended its peak after 20 years in silty loam and clay loam.MBN reached its peak after 18 years in sandy loam and silty loam,but 28 years in clay loam.Meanwhile,PLFA in sandy loam soil was highest in the fifth year of fertilization(385%).After 11 years of clay fertilization,catalase activity reached its lowest level(-80.49%).The increase of microbial properties in clay was the largest and showed the highest and lowest values.Compared with the silt loam,the enzyme activity in the clay loam did not show a higher increase in the first 10 years of fertilization due to the anaerobic environment and adsorption.Combined application of chemical and organic fertilizer is beneficial to the improvement of soil microbial properties,which is the best way to improve soil quality and maintain the sustainable development of agricultural soil.However,fertilization should be adjusted according to soil texture distribution and climatic conditions.Moreover,these climate controls should be applied to make fertilization strategies more adaptable to global change.