|Melkonian, J - Cornell University - New York|
|Poffenbarger, H - Iowa State University|
|Ryan, M - Cornell University - New York|
|Moebius-clune, B - Natural Resources Conservation Service (NRCS, USDA)|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2017
Publication Date: 9/7/2017
Citation: Melkonian, J., Poffenbarger, H.J., Mirsky, S.B., Ryan, M.R., Moebius-Clune, B.N. 2017. Estimating nitrogen mineralization from cover crop mixtures using the Precision Nitrogen Management model. Agronomy Journal. 109:1944-1959.
Interpretive Summary: Cover crops influence carbon and nitrogen cycling in agricultural systems. Specifically, the concentration of carbon and nitrogen contained in the cover crop shoot and root biomass influences microbial activity, the decomposition rate of the cover crop, and the subsequent availability of nitrogen released from the cover crop as well as that which comes from the soil. Growers need decision support tools that can estimate the effects of cover crops, in real-time, to make decision on their fertility management. Therefore, data collected from cover crop decomposition studies at Beltsville Agricultureal Research Center were used to calibrate and test a dynamic simulation model (Adapt-N) for simulating C and N dynamics following cover crop termination in maize (Zea mays L.) production systems. Calibration resulted in a good fit between measured and modeled N release from the terminated cover crop mixtures. The revised, calibrated model will be used in N management (Adapt-N decision support tool for maize N recommendations) and in studies of N dynamics in maize agro-ecosystems that include cover crops. Adapt-N, has recently been purchased by the private sector and will therefore have broad use among the farming community in addition to researchers. The model will allow growers the ability to maintain optimal crop yields while minimizing over-application of nitrogen fertilizer.
Technical Abstract: Cover crops influence soil nitrogen (N) mineralization-immobilization-turnover cycles (MIT), thus influencing N availability to a subsequent crop. Dynamic simulation models of the soil/crop system, if properly calibrated and tested, can simulate carbon (C) and N dynamics of a terminated cover crop and estimate crop-available N over diverse production environments. This study was conducted to calibrate and test a dynamic simulation model for simulating C and N dynamics following cover crop termination in maize (Zea mays L.) production systems. Data from a 2-yr field study of different cover crop combinations, fertilizer sources and rates, and tillage practices for maize production were used in model calibration and testing. First order rate constants governing plant residue decomposition were calibrated so that statistical measures of model best fit were optimized. Calibration resulted in a good fit between measured and modeled N release from the terminated cover crop mixtures (root mean square error (RMSE) and Willmott’s index of agreement (IA) ranging from 10 – 13 kg N ha-1 and 0.87 – 0.95, respectively). The calibrated model performed reasonably well in the testing phase (RMSE and IA ranging from 21 – 30 kg N ha-1 and 0.67 – 0.92, respectively). Simulated and measured N remaining were similar (within 20 kg N ha-1) for most treatments, particularly in the time period when in-season N fertilizer applications typically occur. The revised, calibrated model will be used in N management (Adapt-N decision support tool for maize N recommendations) and in studies of N dynamics in maize agro-ecosystems that include cover crops.