Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2015
Publication Date: 12/11/2015
Publication URL: http://handle.nal.usda.gov/10113/62826
Citation: Feng, G.G., Tewolde, H., Ma, L., Adeli, A., Sistani, K.R., Jenkins, J.N. 2015. Simulating the fate of fall- and spring-applied poultry litter nitrogen in corn production. Soil Science Society of America Journal. 79:1804-1814.
Interpretive Summary: Conventional methods to track mineralized N from soil-applied manures and quantify the amount lost due to various causes during the year are difficult to implement, inaccurate, and expensive. The RZWQM2 (Ver.6.25) simulation model provided an alternative to estimate these values. The model was calibrated and evaluated for simulating the fate and balance of N from 18 Mg ha-1 poultry litter applied in the fall or in the spring on a field under continuous corn production in Mississippi. The model prediction was sensitive and accurate enough to quantify the mineralization and loss of N derived from poultry litter applied at different times. The model estimated that approximately 30 to 50% of fall-applied litter N (assumed to be 100% in the organic form at application) converted to mineral forms by spring when corn was planted. Such high mineralization rate in the absence of an actively growing crop is not desirable because of the vulnerability of the mineral N to loss. In fact, the model estimated that 10 to 25% of the total N applied is lost between the time the litter is applied in the fall and the corn is planted in the spring. When the litter is applied in the spring, the model simulated the mineralization to be about the same as the fall-applied litter. Approximately 25 to 51% of the total litter N applied in the spring mineralized during the growing season. This compares with the corresponding mineralization of 30 to 50% of the total fall-applied litter N. However, the loss was much less if the litter was applied in the spring than in the fall. The loss of litter N between application and harvest was an average across the 3 yr of 119 kg ha-1 if applied in the fall and only 34 kg ha-1 if applied in the spring. The greater loss of litter N if applied in the fall is consistent with the grain yield reduction of 12.8% if the litter was applied in the fall instead of spring (Tewolde et al., 2013). These results clearly show that poultry litter should not be applied in the fall in the southeastern US to fertilize spring planted crops such as corn. We believe the best time to apply litter to fertilize spring-planted crops in regions with mild winters like that of the southeastern US is around planting from both productivity and environmental quality perspective. If spring application is not an option for some growers, the quantitative information on nitrogen availability and loss by each pathway is provided to help with a better management if the litter is applied in the fall. Future long-term simulations using historical weather data may provide more insightful information on the fate and balance of N derived from poultry litter under various management practices. Such simulations could help determine the optimum poultry litter application time and rate under various cultivation senarious and help frame the guidelines for profitable, sustainable, and environmentaly safe application of poultry litter in the southeastern US and similar environments.
Technical Abstract: Monitoring the fate of N derived from manures applied to fertilize crops is difficult, time consuming, and relatively expensive. But computer simulation models can help understand the interactions among various N processes in the soil-plant system and determine the fate of applied N. The RZWQM2 was calibrated and evaluated using 3 yr (2006-2008) of field data to simulate the fate and balance of N derived from broiler litter applied to a continuous corn production system. One rate of litter (18 Mg ha-1) and one rate of NH4NO3-N (202 kg ha-1) were applied in each fall or spring of the 2006 to 2008 growing seasons to determine the right application timing of litter in a corn field near Starkville, MS. Generally, simulated grain yield, biomass, soil nitrate, and plant N uptake responded correctly to the timing of litter or NH4NO3 application. The model estimated that 57% (279 kg/ha) of the total litter N applied in the fall and 51% (249 kg/ha) of that applied in the spring mineralized by the end of the first growing season. The combined litter N loss to leaching, denitrification and volatilization by the end of the first year was 24% of the total if applied in the fall and only 9% if applied in the spring. At the end of the experiment in November 2008, 88% of the total 1507 kg/ha litter N applied in the previous three falls and 72% that applied in the previous three springs was mineralized. The loss of mineralized litter N averaged across the 3 yr was 162 kg/ha (32% of the total N applied, 37% of the mineralized N) if applied in the fall and only 35 kg/ha (7% of the total applied, 11% of the mineralized N) if applied in the spring. The primary avenue of litter N loss was leaching if applied in the fall and denitrification if applied in the spring. Overall, this work provided reasonable estimates of N mineralization and loss from poultry litter applied in the fall versus spring. Results clearly demonstrated that spring is the best time to apply litter for fertilizing spring-planted crops in the southeastern US.