Effect Of Polyaspartic Acid Water-retaining Agent On Soil Microecology And Isolation And Identification Of Degrading Bacteria

Polyaspartic acid water-retaining agent(PASP)is an environment-friendly,biodegradable,high-molecular hydrogel material with water and fertilizer retention capabilities.It is suitable for alkaline sandy loam soil and plays an important role in solving the shortage of water resources in Xinjiang agriculture.The effects of PASP on soil water content,soil microbial community,soil physical and chemical properties and other soil micro-ecological indicators,as well as cotton yield and fiber quality were studied.The application of polyaspartic acid water-retaining agent could significantly improve the water holding capacity of cotton fields.During the whole growth period of cotton,the volumetric water content of cotton field soil had increased by more than 4%on average,and kept the cotton roots at a high water content level for a long time.Compared with the control group,PASP treatment significantly increased the content of soil organic matter,available phosphorus,and ammonium nitrogen,increased the enzyme activities of catalase and alkaline phosphatase,and decreased the activity of urease.The application of PASP changed the microbial community structure of the soil and had a greater impact on the bacterial community than on the fungal community.The application of PASP has a significant effect on Methylophaga,Sphingomonas,Cupriavidus,Pseudeurotium,Fusarium and Nectria.Compared with the control group,application of 15 kg ha^-1,75 kg ha^-1,and 150 kg ha^-1PASP increased seed cotton yields by 3.94%,8.31%,and 7.71%,respectively.The application of PASP in the cotton field also improved the reflectance,micronaire value and short fiber index of cotton(p<0.05).Experiments had shown that 75 kg ha^-1of PASP could effectively alleviate drought stress in arid and semi-arid regions.Using cultivable technology and molecular biological analysis to isolate and identify polyaspartic acid water-retaining agent degrading bacteria.In this paper,the soil samples of cotton field applied with PASP were used as research materials,and the culture medium with PASP as the only carbon and nitrogen source was used as the separation medium.A total of 278 strains of 18 genera were isolated,including Streptomyces,Bacillus,Rhizobium,Novosphingobium,Nocardioides,Herbaspirillum,Stenotrophomonas,Sphingomonas and Aquabacterium accounted for higher proportions.Through the preliminary screening of the degradation function of polyaspartic acid water retaining agent,25 functional strains were obtained,and the degradation performance of the new strain TRM 66268-LWL was verified.It was found that the degradation rate of PASP exceeded 70%.A new species of actinomycete TRM 66268-LWL with PASP degradation function was identified by multiphase classification method,named as Streptomyces polyasparticus.The strain was observed to be Gram-stain-positive and to form greyish-white aerial mycelia that differentiated into straight spore chains with round spores.The strain could grow on the medium with PASP as the sole carbon source or carbon and nitrogen source.The genome of strain TRM 66268-LWLwas approximately 10.2 Mb in size with DNA G+C content of 70.11mol%.The average nucleotide identity value(ANI)between strain TRM 66268-LWL and the phylogenetically related strain Streptomyces indicus IH32-1^Twas calculated to be 85.49%.The digital DNA-DNA hybridization value(d DDH)between them was 30.40%.The types of whole-cell hydrolyzed sugars were ribose,mannose and arabinose.The whole-cell sugar pattern of TRM 66268-LWL consisted of ribose,mannose and arabinose,and the principal phospholipids were found to be diphosphatidylglycerol,phosphatidylethanolamine,phosphatidylinositol mannoside,phosphatidylinositol and two undetermined polar lipids.The main fatty acid types of this strain were iso-C_16:0(14.01%),anteiso-C_15:0(13.44%),cis-C_16:1(13.35%),C_15:0(11.92%)and C_16:0(10.56%).The predominant menaquinones were MK-7,MK-7(H₄),MK-9(H₈),MK-10(H₆).The optimal growth conditions were 28?,1%Na Cl,and p H 7.0.The deposit number is TRM 66268-LWL=CCTCC AA 2020003=LMG 32106.