Purpose
Manure nitrogen losses from agricultural soils presents a significant challenge with far-reaching implications for global food security and environmental health. This project evaluates common manure application practices and studies some mechanistic factors and relationships that influence manure nitrogen losses via leaching and volatilization when manure is soil applied. The study highlights the tradeoffs between reduction of ammonia emissions and nitrogen leaching aiming to promote effective manure management techniques that increase crop nutrient use efficiency while minimizing nutrient losses to the environment.
What Did We Do?
Dairy manure was applied to a silt loam agricultural field using different manure applications. The study involves six experimental treatments, each applying 94 m³ ha-1 of liquid dairy manure through different methods: injection, incorporation, surface broadcast, and two treatments with urease inhibitor-one injected and one surface broadcast. Additionally, there are control plots with no manure application. Immediately after manure application, ammonia emissions were routinely measured using an FTIR while cumulative nitrate leaching for the growing season was assessed using the resin cartridge methodology. Corn silage was planted and yield data collected at the end of the growing season and nitrogen use efficiency following each experimental treatment determined.
What Have We Learned?
Preliminary results suggest that manure incorporation and injection with or without the urease inhibitor, have a comparable significant impact on corn silage yield when compared to surface manure application and plots with no manure application. However, there were no significant differences in N uptake among treatments. Additionally, there were significant differences in the cumulative nitrates leached when comparing the manure application methods to the no-manure plots. Manure injection and incorporation resulted in the highest significant nitrates leached with averages of 104.4 kg ha-1 and 108.4 kg ha-1 respectively, in comparison to surface manure application. Overall, current project data suggests that ammonia emissions tend to be lower in the manure injection especially when the manure is treated with urease inhibitor compared to when manure is surface applied.
These preliminary results suggest that certain manure application practices may offer superior environmental benefits while the agronomic benefits may remain comparable across different practices.
Future Plans
The field project will be extended into a second year under similar soil types to collect additional data for better comparisons and identifications of trends among experimental treatments. Future plans will also include a new project involving the incorporation of biochar and investigating its potential in simultaneously reducing ammonia volatilization and nitrogen leaching in manure and crop systems.
Authors
Presenting & corresponding author
Juma Bukomba, PhD Candidate, University of Wisconsin-Madison, bukomba@wisc.edu
Additional authors
Rebecca Larson, Associate Professor, University of Wisconsin-Madison;
Mathew Ruark, Professor, University of Wisconsin-Madison
Acknowledgements
This material is based upon work supported by the National Science Foundation under Grant No. EFMA-2132036. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
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