Anion Exchange Membrane Soil Nitrate Predicts Turfgrass Color and Yield

Desirable nitrogen (N) management practices for turfgrass supply sufficient N for high quality turf while limiting excess soil N. Previous studies suggested the potential of anion exchange membranes (AEMs) for predicting turfgrass color, quality, or yield. However, these studies suggested a wide range of critical soil nitrate‐nitrogen (NO 3 –N) values across sample dates. A field experiment, in randomized complete block design with treatments consisting of nine N application rates, was conducted on a mixed species cool‐season turfgrass lawn across two growing seasons. Every 2 wk from May to October, turfgrass color was assessed with three different reflectance meters, and soil NO 3 –N was measured with in situ AEMs. Cate‐Nelson models were developed comparing relative reflectance value and yield to AEM desorbed soil NO 3 –N pooled across all sample dates. These models predicted critical AEM soil NO 3 –N values from 0.45 to 1.4 μg cm −2 d −1 Turf had a low probability of further positive response to AEM soil NO 3 –N greater than these critical values. These results suggest that soil NO 3 –N critical values from AEMs may be applicable across sample dates and years and may serve to guide N fertilization to limit excess soil NO 3 –N.