Effects Of Humic Acid On Cotton Growth And Soil Microorganism In Cotton Field In Northern Xinjiang

Xinjiang is an important cotton producing area in China,which hinders soil nutrient circulation in cotton field for many years.In soil ecosystems,microorganisms drive almost all nutrient transformation processes.A new type of organic fertilizer humic acid(HA)has been widely used in agricultural production in recent years because of its effects on slow-release fertilizer,promoting soil microbial activity and increasing crop yield and quality.At present,there is a lack of comprehensive understanding of the effect of humic acid on soil microorganisms in cotton fields in northern Xinjiang.In this study,the experimental materials were XLZ-74 and humic acid(powder).Four treatments were used:conventional fertilization(CK),conventional fertilization with humic acid 30 kg·hm-2(?.HA),conventional fertilization with humic acid 60 kg·hm-2(?.HA),conventional fertilization with humic acid 120 kg·hm-2(?.HA).The effects of application gradient of humic acid on cotton yield and quality,soil physical and chemical properties of cotton field were analyzed by agronomic character survey,field yield measurement,fiber quality test and soil physical and chemical properties.The full length of soil bacteria 16S and fungal ITS1 area sequenced by high throughput sequencing technology were analyzed for the changes of microbial community in cotton rhizosphere soil and for exploring the effect of responding bacteria and fungi on cotton growth.The main findings are as follows:1.Through laboratory and field experiments,the agronomic traits of cotton were investigated.It was found that humic acid could promote cotton growth and increase yield.Both plant height and SPAD value of potted cotton increased firstly and then decreased with the increase of its application amount.There was no significant difference in the number of fruit branches,single boll weight and lint percentage by investigation in the field.Both the number of bolls and the yield of seed cotton per plant of ?.HA treatment and ?.HA treatment increased significantly.The fiber quality of the treated II.HA was the best,including the average fiber length of 32.5 mm,the mean value of uniformity index of 87.9,the mean value of fracture specific strength of 35.2 cN·tex-1,the mean value of Macron of 4.2,and the mean value of elongation of 6.1.2.The physical and chemical properties of rhizosphere soil in cotton field were determined by field experiment.The soil organic matter and total nitrogen content of the treated ?.HA increased significantly,with 7.8%and 35.1%respectively compared with the CK;the available phosphorus and potassium content of the treated ?.HA increased significantly,with 48.9%and 27.3%respectively;and the soil pH value was stable.3.Using the PacBio platform,the total length of bacterial 16S was sequenced in the rhizosphere soil of cotton,and the measured sequence was OTUs by 97%consistent copolymerization.The distribution of OTUs showed that the increase of humic acid positively effected the number of species on the basis of CK flora.Through Alpha diversity analysis,it was found that the diversity in treatment II.HA was the highest,and the rhizosphere bacterial community was more stable than the CK.Compared with CK,humic acid fertilizer increased the relative abundance of beneficial bacteria that can enhance soil fertility,including the Acidobacteria,Brevundimonas,Bacillus litoralis,Anammox 13 and Nitrospira bacterium SG8₃.However,humic acid fertilizer reduced the relative abundance of Alcaligenes and Cutibacterium that usually inhibit the activity of denitrification.The bacterial community structure of cotton rhizosphere soil was also changed due to the changes of bacterial diversity and species abundance composition.4.NovaSeq6000 was used for fungi ITS1 sequencing in cotton rhizosphere soil.The consistent and the copolymers of measured sequences were 97%and 2169 OTUs.The distribution of OTUs showed that the increase of humic acid dosage significantly increased,the number of species on the basis of CK flora.Through Alpha diversity analysis,it was found that the fungi were sensitive to the external environment,the species uniformity of the community was low,and there was no significant difference in diversity for all treatments.Ascomycota and Basidiomycota are the dominant fungi of cotton rhizosphere soil fungi.The application of humic acid significantly enhanced the activity of beneficial fungi such as Penicillium,Issatchenkia and Auricularia,which could increase the content of soil organic matter.The increased fungi Sebacina and Chaetomium could promote germination and growth and prevents cotton fusarium wilt,respectively.The inhibited Phoma and Alternaria could cause leaf blight and cotton rotavirus,respectively.The fungal community structure of cotton rhizosphere soil was changed with the changes of fungal community diversity and species abundance.To sum up,the results in this study provide data support for the application of humic acid drip in cotton production in northern Xinjiang and a theoretical basis for humic acid fertilization soil.