Cooperative Effects Of Earthworm And Mycorrhiza On Maize Growth In Saline Alkali Soil

Earthworms and arbuscular mycorrhizal fungi(AMF)play an important role in improving soil fertility,promoting plant growth and stress resistance.In this study,the cooperative impacts of earthworms and AMF on soil structure,nutrient uptake and physiological adapation of salt tolerance of maize in natural saline alkali soil were studied with the rhizosphere and hyphosphere experiments.The Illumina Meseq sequencing technique,qPCR and structural equation model analysis were used to clarify the mechanism of salt resistance of maize and soil nitrogen transformation by cooperation of earthworms and AMF in saline-alkali soil.Researchs provide a theoretical support for improving the biological fertility of saline-alkali soil and the sustainable development of agriculture.The main results of this study were following:(1)The growth of maize was increased in the slight salinity soil,and inhibited under the intermediate and severe salinities.The slight salinity could increase maize biomass by increasing the uptakes of P,K,Mg,Cu,B and Mn by maize.In the intermediate and severe salinity soils,the salt content,Na adsorption ratio and shoot Na were increased,which lead to the reduction of the uptakes of K,P,N,Ca,Mg,Cu and Mn,etc by maize to inhibit maize growth.The intermediate salinity increased the root IAA to decrease the root nutrient uptakes and growth,while increased the root Me-JA to enhance the root C/N,subsequently resist salt osmotic stress.In the intermediate and severe salinity soils,the increased shoot ZR possibly could resist the oxidative damage and osmotic stress induced by the high shoot Na to keep the maize growth.(2)Under the intermediate salt stress,earthworms and AMF can promote nutrient uptakes and maize growth by decreasing the salt content and increasing soil catalase activity.Earthworm addition significantly increased the soil P availability and the relative abundance of Pontibacter fragments(phosphate-solubilizing bacteria).AMF inoculation significantly decreased the soil total N content and increased the soil microbial biomass carbon.Earthworms and AMF decreased the soil salt content,soil pH and available potassium,and increased the soil organic carbon.Earthworm addition significantly increased the mycorrhizal infection and arbuscular abundance.The combination of earthworms and AM fungi could increase the relative abundance of Trichoderma fragments(plant-promoting bacteria)and reduce the relative abundance of Stachybotrys fragments(plant pathogen).The earthworms and AMF cooperatively increased the uptake of nitrogen,phosphorus and potassium of maize,and finally increased the maize biomass.(3)Under severe salt stress,earthworms and AMF could improve the soil physical structure and increase the physiological tolerance and growth of maize.Earthworm and AMF cooperatively reduced the soil salt content,increased the soil aggregates proportion and osmotic regulation,then increased the nutrient uptakes and photosynthesis to promote maize growth under severe salt stress.Earthworm could reduce the soil salt content,increase the maroaggregates and root Na content,and promote nutrient uptakes(N,K,Ca and Mg).AMF could reduce the shoot Na content,increase the K transport from root to shoot,reduce oxidative damage,promote photosynthesis and carbon accumulation to improve the salt tolerance of maize.(4)In the hyphosphere,the cooperation between earthworms and AMF hyphae could increase soil nitrogen availability to promote the N uptake by maize.Earthworms and AMF hyphae could promote the soil nitrogen transformation by improving soil physical structure and regulating soil nitrogen-cycling bacteria including nitrogen fixer(nifH),ammonia oxidizer(AOB amoA)and denitrobacteria(nirS,nirK and nosZ).Earthworm addition significantly increased the hyphal length density in saline soil.At both day 40 and 60,earthworm and AMF hyphae could promote the formation of macroaggregates to increase the soil microbial biomass nitrogen,then increased the soil N03--N content.At day 60,earthworms and AMF hyphae increased the soil nitrogen fixers(nifH)and ammonia oxidizers(AOB amoA)by improving soil structure,then increased the soil NO3--N content and NH4+-N content;Earthworm and AMF cooperatively increased the soil NH4+-N content by promoting mycorrhizal hyphal growth.