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Submitted to: Western Nutrient Management Conference Proceedings
Publication Type: Proceedings Publication Acceptance Date: 2/20/2017 Publication Date: 3/2/2017 Citation: Delgado, J.A. 2017. Effect of management on nitrogen budgets and implications for air, soil, and water quality. Western Nutrient Management Conference Proceedings. P. 1-9. Interpretive Summary: There are different approaches that can be used to assess nitrogen budgets and to calculate nitrogen use efficiencies and system use efficiencies. This proceedings paper covers some of these different approaches and methods to conduct nitrogen budgets to assess management practices, nitrogen use efficiencies and nitrogen losses to the environment. New information about using long-term nitrogen budget approaches to assess system use efficiencies and nitrogen losses to the environment, as well as new research questions that we need to answer, will also be discussed. Preliminary results suggest that the method of using linear regressions to conduct C and N balances (modeled in SAS using PROC MIXED with a first-order autoregressive covariance structure for repeated measures over years on the subject plot, together with lack-of-fit analysis [LOF] and adjusted p-values with using PROC MULTTEST with the false discovery rate [FDR] method) is a strong approach to assess changes of nitrogen with time and nitrogen balance. These preliminary results suggest that the cycling of N from added fertilizer is larger than expected and net N losses from the system are larger, with potential global and regional implications. Additional assessment of the pathways is critical to determine the pathway(s) for losses (denitrification [N2]; leaching [NO3]; ammonia volatilization [NH3], etc.). However, other studies have found the potential for nitrogen sequestration and minimization of nitrogen losses to the environment. Nitrogen is key for agricultural production and to increase yields, economic returns and food security. There is the potential to use best management practices to minimize the losses of nitrogen to the environment. Additional research is needed to better understand the long-term effects of best management practices and to identify site-specific management practices that could contribute to sustaining yields while minimizing losses of nitrogen to the environment. Technical Abstract: Nitrogen is a key nutrient for both national and global food security, and nitrogen inputs from organic and/or inorganic sources are essential to maintain sustainable and economically viable agricultural systems. The challenge with nitrogen is that it is very dynamic and mobile, and some forms are subject to biogeochemical transformations that contribute to atmospheric, surface and leaching losses. Although nitrogen provides important rural, national and global economic benefits, nitrogen losses can impact the environment and have negative economic impacts at the farm level or on larger scales. Managing nitrogen is key to increasing nitrogen use efficiencies and minimizing nitrogen losses. The scientific literature is full of publications assessing the pathways for nitrogen losses. Understanding the mechanism(s) for these losses is important for the development of management practices that reduce the off-site movement of nitrogen. For example, precipitation events could contribute to the transport of nitrogen out of the root zone, increasing the potential for it to be transported to surface and underground water bodies. There are different approaches that can be used to assess nitrogen budgets and to calculate nitrogen use efficiencies and system use efficiencies. This presentation will cover some of these different approaches and methods to conduct nitrogen budgets to assess management practices, nitrogen use efficiencies and nitrogen losses to the environment. Results from studies conducted using 15N isotopic approaches, non-fertilizer (control) plots, long-term data, and simulation modeling approaches will be presented. Additionally, examples of how best management practices such as cover crops, crop rotations, conservation agriculture, controlled release fertilizers, nitrification inhibitors, and other practices could be used to increase nitrogen use efficiencies to contribute to the conservation of air, soil, and water quality, will also be presented. New information about using long-term nitrogen budget approaches to assess system use efficiencies and nitrogen losses to the environment, as well as new research questions that we need to answer, will also be discussed. |
