| ?Objective?With the rapid development of integrating water and fertilizer technology,seriously relied on better solubility of chemical fertilizer,leading to a sharply decline of organic fertilizer application amounts.Additionally,long-term consecutive planting cotton.As a result,soil organic matter content is lowly,soil structure and tilth decline obviously,as well as soil biological activity in the oasis drip irrigation cotton field.In this study,a continuous 4-year field trial was carried out out in drip-irrigated conditions,which to research the impacts of substituting 20%,40% of chemical fertilizer by 3000 kg/hm2,6000 kg/hm2 organic fertilizer on soil physicochemical properties,enzyme activies and soil biological effects.The objective was to compare the effect of different fertilizer applications on soil pathogens and antagonistic bacteria community abundances in cotton field,explore the driving factors in altering soil microbial community abundances in cotton field.And investigate the mechanism of common organic fertilizer / bio-fertilizer mixed with chemical fertilizer on soil biological characteristic.What's more,to build good soil structure,improve fertility of soil arable layer,and provide technical support for oasis irrigation farmland also were our target.According to the reduction and substitution of chemical fertilizer in national policy,combining succession cropping and long-term solely chemical fertilizer application of cotton industry,buliding a fertilization strategy of suitability local condition.?Method?In the present research,a filed experiment was carried out in 2014,long-term experiment have already putted into effect for 3 years before my study,studying the effects of the chemical fertilizer substituted by different ratios of organic fertilizer on cotton soil physicochemical properties,enzyme activities,the change of pathogen and antagonistic and driver factors were used in our study.1.Dilution plate methods,soil enzyme and quantitative real-time PCR(q-PCR)were determined as the effect of different fertilizer application treatments on soil biological properties.2.The effect of soil physicochemical environment factors on soil biochemistry,microbial population and structure community diversity through comprehensive evaluation,including Rader diagram,Cluster analysis and Redundancy analysis.?Result?1.Compared with CF,organic fertilizer at different rates of 3000 kg/hm2 or 6000 kg/hm2 combined with chemical fertilizer increased water holding capacity by 16.5% ~ 33.3%;a significantly(P<0.05)reduction of soil bulk density(BD)was observed under organic manure treatments compared with CK.BD decreased by 14.8 % more with 60% CF + BF treatment than with CK treatment.Compared with CK treatment,the macroaggregate content in organic manure increased,0.25-2mm mechanical-stable aggregate take up 53.2 %-59.4 % the total soil;>0.25 mm water-stable aggregate in 80% CF + OF and 60% CF + OF treatment were higher than CK,respectively.Additionally,soil aggregate degree of particle size of reunion and stability were clearly increased under mineral N fertilizer reduction and organic fertilizer substitution.2.Mineral N fertilizer reduction and organic fertilizer substitution obviously changed soil p H,EC and CEC.There have a significant improving of soil TN,NH4+-N and NO3--N concentration(P<0.05)by organic fertilizer amendment.The highest level of soil N content was obtained with 60%CF+BF treatment.In contrast to CF,soil SOC and DOC content increased by 8.1%~22.2% and 12.7%~21.4%,respectively.The DOC content with 80%CF+OF,60%CF+OF,80%CF+BF and 60%CF+BF treatments were 1.7%,5.3%,8.0% and 13.5% higher than those of CF,respectively.In addition,Soil P and K contents were significantly increased by organic fertilizer application(P<0.05).3.Bolling and harvest periods of cotton showed the same result,a successive 4-year mineral N fertilizer reduction and organic fertilizer substitution in drip-irrigated condition,markly increased the activities of soil urease,protease,alkaline phosphatase,invertease,?-glucosidase and arylsulfatase(P<0.05).The effect degree of different treatments on soil enzyme activity followed the order of: BF >OF >CF > CK.Meanwhile,soil MBC and MBN were significantly increased by organic fertilizer or bio-organic fertilizer amendments while decreased MBC/MBN.In addition,two periods' soil basal respiration were significantly increased 23.2%~95.2%,13.7%~40.0% across all organic fertilizer added treatments compared with CF,respectively.4.The result showed that the resistant enzyme activities of catalase(CAT),peroxidase(POD),polyphenoloxidase(PPO)and fluorescein diacetate(FDA)were improved by the bio-fertilizer addition,the order of the soil enzyme activities was as follows: BF > OF > CF > CK.Both plate counting and q-PCR methods were used to evaluate the effects of different fertilizers on antagonistic bacterial population.The greatest number of Bacillus,Trichoderma and Pseudomonas appeared in60% CF + BF treatment;The greatest number of bacillus of 18.1 cfu × 103·(g · soil)-1(the average of60% CF + BF and 80% CF + BF treatments)appeared in bio-fertilizer treatment,which was higher by4.6 %,5.8 % and 50.0 % in comparison with the averages of 60% CF + OF and 80% CF + OF,chemical fertilizer and control,respectively.And the number of soil pathogenic microorganism,Fusarium and Verticillium dahliae significantly(P < 0.05)decreased with bio-fertilizer application using both plate-counting and q-PCR methods.5.Under successive 4-year mineral N fertilizer reduction and organic fertilizer substitution condition,soil aggregate stability and soil biological characteristic influence each other.ELT was significantly nagetive correlation with WMD,SOC,BS and enzyme activity.Meanwhile,SOC also was negative correlated with MBC/MBN,but were positively associated with BS,?-glucosidase and invertease.The result of Monte Carlo showed that WR0.25(Explains % = 43.4,Pseudo-F = 12.2,P = 0.002)was more sensitive responsed to different fertilization than PAD,WMD and ELT.RDA analysis demonstrated that the populations of Bacillus,Trichoderma and Pseudomonas positively correlated with POD,FDA,PPO and CAT activities.In addition,CK treatment positively correlated with Fusarium abundance,whereas CF positively correlated with Verticillium dahliae abundance.?Conclusion?1.In the bolling and harvest periods of cotton,mineral N fertilizer reduction 20% and 40% and organic fertilizer substitution 3000 kg·hm-2 or 6000 kg·hm-2 significantly increased the soil C,N,P and K concentration;in contrary to CF treatment,soil aggregate stability also was significantly improved(P<0.05).2.In drip irrigation cotton field,organic fertilizer combined with chemical fertilizer substantially improved soil microbial biomass,basal respitation,microbial quotient and soil enzyme activities.In addition,the higher the added fertilizer dose,the greater the soil biological activities with both organic and bio-fertilizer treatments,two periods' data have common tendency.3.The study indicating that organic alterations have a significant effect on suppressing the soil-borne pathogens Fusarium and Verticillium dahlia.Our results evidenced that SOC and AP(P < 0.05)were the major driving factors affecting the abundances of soil antagonistic bacteria,and soil BD and p H were dominant factors in the variation of soil Fusarium and Verticillium dahliae abundances.The fertilization strategy exhibited significant effects on SOC and biological properties as well as soil aggregate structure improving.Therefore,this method should be regarded as the sound fertilization management for improving soil quality,especially under drip-irrigated field. |
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