Effects Of Tillage And Straw Returning On Soil Fungal Diversity And Organic Carbon Stability In Wheat-maize Cropping Fields

This study was conducted from 2021 to 2022 at the long-term positioning experimental site of Agronomy Experimental Station(36° 09′30.78″-36° 09′27.59″N,117° 09′13.79″-117° 09′12.02″E),Shandong Agricultural University,Tai’an City,Shandong Province(since 2002).The experiment was a split plot design.In the main plot,there were two tillage measures: no-till and subsoiling,and in the secondary area,there were two levels: full straw returning and no straw returning.There were four treatments: subsoiling with the returning of straw(STs),subsoiling(ST0),no-till with the returning of straw(NTs)and no-till(NT0).The experiment adopted the two crops a year planting system of winter wheat(Ji Mai 22)and summer maize(Zheng Dan 958).The effects of tillage and straw returning on soil fungi and cementing materials,and the effects of fungi and cementing materials on aggregates and carbon components were studied.The results were as follows:(1)The diversity of fungi was increased during wheat filling stage at subsoiling with the returning of straw,the diversity of fungi was increased at subsoiling furrow,the richness of fungi was increased at subsoiling clearance,the diversity of fungi was increased at the hotspot of enzyme spectrum,and the richness of fungi was increased by the non-hot spot.At the phylum level,the top three dominant fungal communities in wheat and maize were Ascomycota,Mortierellomycota and Basidiomycota.Among the top five dominant fungal communities at the genus level,Mortierella was the primary factor affecting the changes of aggregates at filling stage of wheat and maize,and the contribution of aggregates in wheat and maize reached 33.20% and 40.40%,respectively.Mortierella was the main fungal community affecting the carbon component in wheat filling stage,contributing 30.10% to the carbon component at wheat filling stage.Cercophora was the main fungal community affecting the carbon component at maize filling stage,contributing 38.70% to the carbon component at maize filling stage.(2)The contents of polysaccharide,furic acid,humic acid and complex ferric oxide in soil were increased by 4.91%,9.32%,1.58% and 6.93%,respectively,compared with those of no-till with the returning of straw,and the contents of free ferric oxide and amorphous ferric oxide were decreased.Soil polysaccharide,fulvic acid,humic acid and complex ferric oxide have significant positive correlation with the mean weight diameter and geometric weight diameter of aggregates,and have significant positive correlation with each carbon component.By increasing the content of soil polysaccharide,fulvic acid,humic acid and complex ferric oxide,the stability of aggregates can be improved.It enhanced the protective effect of aggregates on organic carbon,and finally increased soil organic carbon content and carbon storage.(3)The spike number and 1000-kernel weight of wheat increased by 38.42% and1.95%,respectively,compared with no-till with the returning of straw.The yield of wheat increased by 23.52% compared with that of no-till with the returning of straw.The number of grains per ear and 1000-kernel weight of maize increased by 7.63% and 1.77% compared with no-till with the returning of straw.The yield of maize increased by subsoiling with the returning of straw,which increased by 15.29% compared with no-till with the returning of straw.In conclusion,subsoiling with the returning of straw can improve the fungal richness at filling stage of wheat,increase the contents of polysaccharide,fuluric acid,humic acid and complex ferric oxide in soil,improve the stability of aggregates,increase the content and storage of carbon components in soil,and increase wheat and maize yields,which is more suitable for popularization in this region.