Impact of dissolved organic matter on Zn extractability and transfer in calcareous soil with maize straw amendment

PurposeCrop straw return into arable land is a common method of disposing of excess straw in China and can improve soil dissolved organic matter (DOM) that is known to modify soil zinc (Zn) extractability and mobility.Materials and methodsWe conducted a soil box (internal dimensions, 160x140x80mm(3)) experiment to evaluate the response of Zn extractability and transfer by diffusion to DOM after maize straw amendment (St, 0 and 15gkg(-1)) in calcareous soil treated with ZnSO(4)7H(2)O (Zn, 0 and 20mgkg(-1)). Soil treated with St(0)Zn(0) (control), St(15)Zn(0), St(0)Zn(20), or St(15)Zn(20) was isolated in the 10-mm center of the box, and untreated soil was placed in compartments at either side.Results and discussionResults revealed that addition of St(0)Zn(20) or St(15)Zn(20) increased the concentration of Zn extracted with diethylenetriaminepentaacetic acid (DTPA-extractable Zn) in the central layer compared with control or addition of St(15)Zn(0). Over the course of 45days, transfer of DTPA-extractable Zn into the adjacent untreated soil was detected at 15-20mm in soil with St(15)Zn(20) but at 10-15mm with St(0)Zn(20) and only 0-5mm with St(15)Zn(0). Additionally, a higher amount of DTPA-extractable Zn transfer into the adjacent untreated soil also occurred in St(15)Zn(20). This increased DTPA-extractable Zn transfer may be associated with the formation of Zn-fulvic acid complexes with the provision of DOM derived from straw.ConclusionsSoluble Zn combined with straw return may be a promising strategy for improving both Zn mobility and extractability in calcareous soil.