Predicting nitrogen mineralization from long term application of dairy manure in a semiarid cropping system

Authors: Leytem, April; MOORE, AMBER - Oregon State University; Rogers, Christopher; Dungan, Robert - Rob

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2023
Publication Date: 12/15/2023
Citation: Leytem, A.B., Moore, A.D., Rogers, C.W., Dungan, R.S. 2023. Predicting nitrogen mineralization from long term application of dairy manure in a semiarid cropping system. Soil Science Society of America Journal. 88(1):71-88. https://doi.org/10.1002/saj2.20599.
DOI: https://doi.org/10.1002/saj2.20599

Interpretive Summary: Manure management will continue to be a critical part of dairy operations and detailed understanding of nitrogen (N) mineralization will allow improved strategies for use on a range of crops. This is particularly important in crops with quality parameters that are sensitive to N and thus, this research will potentially increase the land area on which manure can be applied. Results from the study provide evidence of the relative contribution of manure, residue, and soil parameters in determining N mineralization amounts seasonally. While manure application rates, specifically N content, are an important factor for estimation of N-mineralization, additions of broadleaf residues, such as sugarbeet leaves and potato tops, must be considered in manure amended systems as these additions alter N mineralization. Soil organic matter (OM) and electrical conductivity (EC) were also important parameters for determining the best fit model representing a source of both carbon (C) and N as well as an understanding that enhanced soil salinity through high rates of manure applications over long times periods is important as it alters microbial community function. Further, our research on N-mineralization from dairy manure in semiarid production areas and crop data will provide greater understanding of specific crop response under a range of manured conditions. Finally, the developed model for N mineralization from dairy manure is a substantial improvement, as estimation tools are currently unavailable in the region and should be incorporated into manure fertilizer recommendations for cropping systems.

Technical Abstract: Approximately 37% of US milk production occurs in semiarid regions providing an opportunity to recycle manure nutrients through a variety of cropping systems. Accurate prediction of nitrogen (N) mineralization is critical to determine manure application suitability in intensive irrigated agriculture as many crops in the region have quality parameters that are sensitive to N. Research was conducted in south central Idaho to evaluate N mineralization via a buried bag methodology to develop a predictive N-mineralization model. The study was arranged in a randomized complete block design with manure application rates of 18, 36, and 52 Mg ha-1 both annually and biennially with synthetic fertilizer and untreated check treatments. The crop rotation included small-grain and broadleaf crops. Greater manure applications resulted in an increase in soil organic matter (SOM), total nitrogen (TN), and nitrate (NO3-N) at the culmination of the study. Nearly five-times as much N was mineralized annually in the 0 to 30 cm depth as compared to the 30 to 60 cm depth. Increased rates of mineralization for each kg of added N occurred in years when residue from broadleaf crops (slope = 0.17) was applied as compared to small-grain years (slope = 0.07). Stepwise modeling determined that the most predictive model for seasonal N mineralization (R2 = 0.79) included manure N, residue N, soil organic matter, and electrical conductivity. These results allow preplant N mineralization estimation and will prove critical for managing manure in semiarid regions for agronomic, economic, and environmentally sound crop production.