Anion-exchange membranes used to assess management impacts on soil nitrate

Our goal was to determine if anion-exchange membranes (AEMs), which can be placed in situ in soils and act as anion exchangers, were better soil nitrate (NO_3-) assessment tools than soil extraction. During winter 1993–1994 we compared NO_3-in the surface of tilled and non-tilled soils that were subjected to rye cover crop and fallow winter coverage treatments. Estimates of soil solution concentrations of NO_3-based on KCl extracts of the AEMs were between 1 to 5 fold higher than concentrations based on soil extracts. Both methods of NO_3-assessment documented a general decline in N_O3-availability during the winter; however, only the AEM NO_3-data produced statistically significant results. AEM data suggested that the combination of fall tillage and winter fallowing increased soil NO_3-contents and led to more potential for loss of NO_3-during the 1993–1994 winter than reduced tillage practices or planting a rye cover crop.