Agricultural Best Management Practices to Mitigate Gaseous Carbon and Nitrogen Losses from a Zea Mays Silage System

View the project final report

Commodities

• Agronomic: corn

Practices

• Animal Production: feed/forage, manure management
• Crop Production: application rate management, conservation tillage, continuous cropping, cover crops, fertilizers, no-till, nutrient cycling, nutrient management, organic fertilizers
• Education and Training: extension, farmer to farmer, networking, on-farm/ranch research
• Energy: energy conservation/efficiency
• Farm Business Management: budgets/cost and returns
• Natural Resources/Environment: carbon sequestration, soil stabilization, greenhouse gas mitigation
• Production Systems: organic agriculture
• Soil Management: green manures, nutrient mineralization, organic matter, soil analysis, soil chemistry, soil microbiology, soil quality/health

Traditional agricultural practices often result in gaseous losses of nitrous oxide (N2O), ammonia (NH3), and carbon dioxide (CO2), representing a net loss of nutrients from agricultural soils, which negatively impacts crop yield and requires farmers to increase nutrient inputs. By adopting best management practices (BMPs; i.e., no-till, cover crops, and applying manure at the appropriate time of year), there is great potential to reduce these losses. Because N2O and CO2 are also greenhouse gases, climate change mitigation via BMP adoption and emissions reductions would be an important co-benefit. However, adopting a no-till and cover cropping system has had setbacks within the Northeast, primarily due to the lack of data. Therefore, we propose to study a no-till and cover crop system with a field trial in Alburgh, VT, which consists of two tillage treatments (conventional and no-till), two cover crop treatments (presence versus absence), and spring or fall manure application. Our objectives are first to determine which combination of BMPs will directly mitigate gaseous nitrogen and carbon losses, second to observe how efficient cover crops are at retaining residual nitrogen, and third to understand the microbial molecular mechanisms driving N2O fluxes. We will meet these objectives by measuring in-field N2O, CO2 and NH3 measurements, mineral soil nitrogen, cover crop root/shoot nutrient content, and through a viable qPCR analysis on nitrifying/denitrifying bacteria. Our results will be paired with ongoing UVM Extension measurements (e.g., cash crop yield and quality) to provide multi-dimensional information on the outcomes of adopting conservational BMPs within the Northeast.

Objective 1: Quantify N2O, NH3, and CO2 emissions from a continuous maize system under a combination of CC versus no CC, NT versus CT, and application of spring manure versus fall manure.
Hypothesis 1: Tillage will have the greatest impact on CO2 emissions, with NT plots having the lowest emission by lessening the amount of oxygen introduced to the soil and by protecting labile organic matter in larger soil aggregates. Further, NT plots that include CC are expected to reduce all three emissions by incorporating excess C and inorganic-N into biomass. Relative to fall manure application, manure applied in the spring will decrease CO2 and N2O emissions as crop nutrient demand will be greatest, though it will increase NH3 emissions due to greater solar radiation and atmospheric temperature.
Hypothesis 2: Weather events (e.g., presence or absence of precipitation, above average temperatures, strong winds at the time of manure application, etc.) will be the largest factor affecting all gas emissions and CC productivity, regardless of treatment.

Objective 2: Quantify above and belowground CC biomass as well as CC N-use efficiency from NT and CT plots with application of spring manure and fall manure.
Hypothesis 1: Cover crop biomass and N-content will be greatest with fall manure application as CC seeds are sewn shortly after that period, thereby providing the crop with adequate nutrients for rapid growth before soils freeze. Tillage will have less of an effect, though CT will promote greater CC biomass by loosening the soil for ease of root growth.

Objective 3: Gain a rigorous understanding of the molecular mechanisms responsible for N2O fluxes before and after manure application with respect to the presence or absence of CC and the presence or absence of tillage via a viable qPCR analysis.
Hypothesis 1: N2O fluxes will be greatest after manure application, regardless of treatment; however, CT plots without CCs will have the largest fluxes relative to NT plots with CCs as more residual nitrate will be available for denitrification and because labile C substrates will be liberated after tillage as a result of breaking apart soil aggregates.
Hypothesis 2: N2O fluxes will be greatest after manure application, regardless of treatment; however, NT plots will favor denitrification (and thus N2O production) relative to CT plots due to the greater soil water content.