| The area of arable land sustained decline,as the population continued to grow,especially in the humid subtropical red soil,accounting for 30%arable land of China.Because of the long-term unreasonable land use and fertilization,soil degradation and low productivity of arable land were extremely serious.Soil organic carbon,although only a small fraction of the total amount of soil,it could provide sufficient nutrients for plant growth and was also an important source of energy and matter in soil organisms.It was very critical for the maintenance of ecosystem productivity and stability,and many other ecological functions.Based on 30 years long-term fertilizer experiment in red soil,we intended to explore the effects of long-term different fertilization,on soil physical properties,chemical properties and microbiological properties.The fertilization regimes involved were no any fertilizers input(CK),application of chemical fertilizers(NPK),organic manure combined with chemical fertilizers(NPKM).The main conclusions of this study are as follows:1)The results of soil aggregate content showed that the amount of water stability aggregates(>0.25mm)in paddy soil was CK 42.40%,NPK 45.70%,NPKM 59.95%.And the content in upland soil was CK 34.98%?NPK 45.80%?NPKM 58.27%.After 30 years of fertilization management,whether in the paddy or upland soil,the pH value of NPK treatment was lowest,and it was the highest level in NPKM treatment.Compared with CK treatment,NPK and NPKM treatment significantly increased the soil organic matter content by 40.2%and 47.8%respectively in paddy soil.And in the upland,NPK and NPKM treatment also increased the content of soil organic matter,but did not reach significant levels.In paddy soil,compared with CK treatment,NPKM treatment significantly increased levels of total nitrogen(p<0.05,the same below).And in upland soil,compared with CK treatment,NPK treatment increased total nitrogen the amount of the increase,but did not reach a significant level,while NPKM treatrment significantly benefited to total soil nitrogen levels.Meanwhile,NPK and NPKM treatment also could increase the soil phosphorus and potassium content,and had significant differences in NPKM treatment.2)The study showed that fertilization had no significant impact on the content of dithionite-citrate-(Fed,Ald).Compared with CK treatment,only NPKM significantly reduced the content of Fed,Ald in upland soil.The oxalate-(Feo,Alo)and pyrophosphate extractable(Fep,Alp)on response to different fertilizer amorphous were the same basically.In paddy soil,compared with CK treatment,NPK and NPKM treatment significantly increased the content of Feo,Alo,Fep and Alp,and NPKM treatment increased the most significant effect.In upland soil,fertilization could increase Fep,Alp,Feo and Alo,but compared with CK treatment,NPKM treatment increase significantly.3)The results of soil enzyme activities showed that compared with CK treatment,NPKM treatment significantly increased the activity of invertase(INV),cellulase(CEL),?-glucosidase(BGL)and xylanase(XYL)in paddy soil.And NPK treatment significantly promoted enhanced the activity of INV,CEL and XYL,and no significant effect on BGL activity.In upland soil,compared with CK treatment,NPK and NPKM treatment significantly contributed to increase activity in these four kinds of soil enzymes,and compared with NPK treatment,INV and BGL activity was also significantly increased in NPKM treatment.In each of paddy and upland soil treatment,the effects of fertilization on soil microbial biomass biomass carbon(SMBC)and microbial biomass biomass nitrogen(SMBN)were basically the same.NPK and NPKM treatment could increase the content of SMBC and SMBN.And compared with CK treatment,growth of NPKM treatment reached significant levels,and the NPK treatment also increased significantly in paddy soil.4)In paddy soil,NPK and NPKM treatment could make microbial community structure changed significantly,reduced fungal/bacterial ratio and increased soil microbial biomass,which NPKM treatment was favorable to the G-bacteria,fungi,actinomycetes and protozoa growth,and NPK treatment was favorable to G+ bacteria growth.In upland soil,the all indicators were close with NPKM treatment,while NPK treatment related with fungal/bacterial ratio stronger.Further study on paddy and upland soils showed that,compared with CK treatment,NPK treatment could easily lead to reduced soil microbial activity,while NPKM treatment could improve the ability of microorganisms to carbon utilization and its functional diversity.5)The maps of three-dimensional fluorescence spectrum showed that CK and NPK treatment primary fluorescence peak appeared at Ex/Em = 240/340 nm in paddy and upland soil.It showed that the peak area was area of tryptophan,and fluorescence spectra of NPKM treatment was in tryptophan,fulvic acid and humic acid region.Humic acid region was weaker compared with the area of tryptophan and fulvic acid fluorescence.6)Correlation analysis showed that almost the flora PLFAs had a significant positive correlation with soil organic matter and total nitrogen,and was not high with available nutrient in paddy soil.The Fed and Ald had a significant negative correlation with StOC and SOC(p<0.01,the same below);and in upland soil,fungi and G+ bacteria had a positive correlation with soil organic matter and total nitrogen.It was indicated that Feo,Alo,Fep,Alp,had a positive correlation with StOC and SOC in paddy and upland soil.While Fed and Ald had a negative correlation with StOC in upland soil,had no correlation with TOC,StOC and DOC in paddy soil.In summary,this study showed that,the NPK treatment increased soil organic carbon and total nitrogen,improved soil fertility,but it could easily lead to reduced soil microbial activity.The NPKM could significantly increase the soil physicochemical and microbiological indicators.So it should be to maintain and improve soil quality in Jiangxi Province.The results would have guiding significance for management and fertilization practices and reduce CO2 emissions in farmland soil. |
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