Submitted to: American Water Resources Association Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/2008
Publication Date: 11/20/2008
Citation: Hively, W.D., Lang, M.W., McCarty, G.W., Keppler, J., Sadeghi, A.M., McConnell, L.L. 2008. Using satellite remote sensing to estimate winter cover crop nutrient uptake efficiency [abstract]. American Water Resources Association Annual Meeting. 2008 CDROM.
Technical Abstract: The practice of planting winter cover crops (rye, wheat, barley) following summer row crops (corn, soybean) is recognized as an effective agricultural conservation practice that can significantly reduce nitrogen losses to groundwater. Accordingly, state cost-share programs have been established to promote the cultivation of winter cover crops on farmland throughout the Chesapeake Bay watershed. However, current estimates of cover crop nutrient uptake are generally based on plot studies extrapolated to the watershed scale based solely on enrollment acreage. Satellite remote sensing provides a tool for real-time estimation of cover crop biomass production on working farms distributed throughout the landscape. This project combined cover crop cost-share program enrollment data with satellite imagery and on-farm sampling to evaluate three years of cover crop performance on over 1200 agricultural fields distributed within the Choptank River watershed on Maryland's Eastern Shore. Agronomic factors influencing cover crop biomass production and nutrient uptake included cover crop species (rye > barley > wheat), planting date (September > November), planting method (drilled > broadcast > aerial), and previous crop (corn vs. soy). Overall, early-planted drilled rye outperformed other methods. The average autumnal nutrient accumulation for rye, barley, and wheat crops, respectively, was 24, 21, and 8 kg ha-1, corresponding to biomass production rates of 1275, 1120, and 410 kg ha-1. Springtime residual nitrate concentrations were reduced from a high of 14 mg kg-1 on sampled fields with low cover crop biomass to < 4 mg kg-1 on fields with biomass greater than 1000 kg ha-1. By utilizing remotely sensed data, cover crop efficiencies can be derived at the landscape scale, accounting for the effects of spatial variability (watershed position, soil type, hydrology) as well as agronomic factors. Study results have strong implications for evaluating and improving the success of the cover crop programs and promoting effective water quality protection strategies. Combining remote sensing with farm program data can provide important insight into the success of various conservation practices, allowing programs to more effectively utilize scarce conservation resources while increasing water quality benefits.