Predicting Cover Crop Nitrogen Content with a Handheld Normalized Difference Vegetation Index Meter

Cover crop (CC) biomass nitrogen content (CC-N; kg ha(-1)) is related to a number of ecosystem services but is rarely measured by farmers and agronomists because of the expense of sampling and analysis. We hypothesized that normalized difference vegetation index (NDVI) measured by a handheld meter could predict CC-N. Using a dataset of 598 observations, we predicted fall biomass N with two separate calibrations for (i) clover-type legumes and (ii) CCs consisting of brassicas (Brassica spp.), cereal grasses, vining legumes, and grasslegume-brassica mixtures. Spring biomass N was predicted with three separate calibrations for (i) cereal grain CCs, (ii) brassicas, and (iii) CCs consisting of pure legumes and grass-legume-brassica mixtures. Quality of the calibrations ranged from r(2) = 0.72 to r(2) = 0.87. Rapidly and inexpensively estimating CC-N with an NDVI meter could enhance the ability of farmers and agronomists to routinely monitor and manage the N related ecosystem services provided by CCs.