Phytoliths And PhytOC Content Characteristics Of Buckwheat And Their Correlations With Soil Physical And Chemical Properties In Southwest China Karst

Phytoliths are extremely stable,and the stable existence of their stored organic carbon is one of the important mechanisms for the long-term stable carbon sink of terrestrial ecosystem.Even herb crops without carbon sink contribution in traditional cognition have obvious organic carbon sequestration by phytoliths.In order to explore the contribution of PhytOC sink of buckwheat planting,this study takes 6species and 17 varieties of buckwheat plants planted in buckwheat base in Xixiu District,Anshun City,Guizhou Province,such as F.esculentum Moench,F.tataricum(L.)Gaertn,F.Tatari-cymosum QF Chen,F.cymosum Trev.Meisn.,F.megaspartanium QF Chen and F.pilus QF Chen,as the research object.Buckwheat plant materials planted in March in spring were collected in May(full-bloom stage)and July(maturation stage)2021,respectively.Plant phytoliths were extracted by wet ashing method,and the PhytOC content was determined by alkali solution spectrophotometry.The characteristics of total silicon,phytolith and PhytOC content of buckwheat plants in different species,varieties,organs and growth stages were studied,and the relationship between total silicon,phytolith and PhytOC content of buckwheat plants and soil environmental factors was discussed,in order to contribute to carbon sink of buckwheat planting in Karst Southwest China,carbon sink estimation of farmland ecosystem and provide theoretical basis and practical support for crop scientific planting in farmland ecosystem in karst area.The main results are as follows:(1)There were significant differences in soil physicochemical properties and rhizosphere soil chemical properties of buckwheat plots with different species.There is a significant correlation between the physical and chemical factors of plot soil and the chemical factors of rhizosphere soil.There was a significant negative correlation between plot soil bulk density and rhizosphere SOC,C:P and N:P;There was a very significant correlation between plot soil p H and rhizosphere SOC,TN,TP,C:P and N:P;There was a significant correlation between available silicon in plot soil and p H,N:P in rhizosphere;There was a significant positive correlation between plot SOC and available silicon and TP in rhizosphere;There was a significant negative correlation between plot TP and available silicon and TP in rhizosphere,and a very significant positive correlation with SOC,C:P and N:P in rhizosphere;There was a significant correlation between plot C:N and available silicon and N:P in rhizosphere.Plot C:P was significantly correlated with SOC,TN and TP in rhizosphere,and negatively correlated with C:P and N:P;There is a significant negative correlation between plot N:P and rhizosphere SOC,TN and C:P,a significant positive correlation with rhizosphere TP,and a very significant negative correlation with rhizosphere N:P.(2)The phytolith content of different plants varied from 1.96-13.27g/kg,with an average of 5.60 g/kg.The phytolith content of F.esculentum Moench was the highest and that of F.cymosum Trev.Meisn.was the lowest.The PhytOC content of varied from 0.06-0.39 g/kg,with an average of 0.16 g/kg.The PhytOC content of F.esculentum Moench was the highest and that of F.megaspartanium QF Chen was the lowest.There were also significant differences in phytolith content and PhytOC content between different varieties.Whether it is F.esculentum Moench,F.tataricum(L.)Gaertn,F.tatari-cymosum QF Chen or F.megaspartanium QF Chen,there are significant differences in phytolith and PhytOC content among their varieties.(3)On the whole,the phytolith content of buckwheat in different organs was root>leaf>stem,and the PhytOC content was leaf>root>stem.The content of phytolith and PhytOC in different organs of the same species were significantly different.The content of phytolith was root>leaf>stem,the content of P PhytOC in different organs of F.cymosum Trev.Meisn and F.megaspartanium QF Chen was root>leaf>stem,and the content of PhytOC in different organs of other species was leaf>root>stem.The content of phytolith in different organs of the same variety was root>leaf>stem,and the PhytOC content was leaf>root>stem.The PhytOC content and phytolith content in roots and leaves is high,which may be related to the strong transpiration of plant leaves,the plant root is the main organ for plants to absorb soil nutrients and water content,the physiological characteristics of buckwheat plants and the contact area between roots and soil.(4)There were significant differences in phytolith content and PhytOC content in different growth stages.The content of phytolith was July>may,and the PhytOC content was also July>May.The PhytOC content and phytolith content in different growth stages of the same species was July>May.In different growth stages of the same variety,except for F.tataricum(L.)Gaertn phytolith content in May>July,the phytolith and PhytOC content of other different varieties in different growth stages are July>may.This may be because buckwheat plants are in the mature stage in July,and the plant silicon absorption and carbon storage have reached a high stage.(5)There was a very significant positive correlation between total silicon content and phytolith content.There is a very significant positive correlation between total silicon content and PhytOC content,and there is a very significant positive correlation between phytolith content and PhytOC content.The results showed that plant total silicon,phytolith and PhytOC affected and interacted with each other.(6)The phytolith content of buckwheat was positively correlated with soil C:P and N:P,negatively correlated with soil TP,and not significantly correlated with other soil physical and chemical factors.The content of PhytOC has a very significant positive correlation with soil SOC and C:P,TN and N:P,and no significant correlation with other soil physical and chemical factors.The phytolith content of buckwheat has a very significant positive correlation with rhizosphere TP,a very significant negative correlation with rhizosphere C:N and C:P,and a significant negative correlation with rhizosphere N:P.There was a significant positive correlation between PhytOC content and rhizosphere TP,a very significant negative correlation with rhizosphere C:P,and a significant negative correlation with rhizosphere C:N and N:P.The results showed that SOC,TP,C:P,N:P and rhizosphere TP,C:N,C:P,N:P are the key influencing factors of phytolith and PhytOC content of buckwheat.