Nitrogen and water availability effects dynamics of soil nitrogen mineralization in a maize (Zea mays) system

Authors: Donovan, Tyler; Comas, Louise; SCHNEEKLOTH, JOEL - Colorado State University; SCHIPANSKI, MEAGAN - Colorado State University

Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2025
Publication Date: 4/22/2025
Citation: Donovan, T.C., Comas, L.H., Schneekloth, J., Schipanski, M.E. 2025. Nitrogen and water availability effects dynamics of soil nitrogen mineralization in a maize (Zea mays) system. Nutrient Cycling in Agroecosystems. https://doi.org/10.1007/s10705-025-10406-8.
DOI: https://doi.org/10.1007/s10705-025-10406-8

Interpretive Summary: Nitrogen fertilization and water availability can independently affect soil and plant processes. Importantly, nitrogen and water affect nitrogen mineralization, the process through which soil microbes make nitrogen available to the crop system that provides a major source of nitrogen for crops like maize. To better understand these effects, we grew maize under two levels of water availability (full and limited) and 3 levels of nitrogen fertilization (low, optimal, and high). We found that nitrogen mineralization rates were highest early in the growing season before the main period of plant uptake. Later in the season when plants take up most of their nitrogen, high N fertilization under full water availability limited the amount of nitrogen available from mineralization, while low nitrogen fertilization under limited water availability also limited this nitrogen pool. Soil enzyme activities, which are associated with total nitrogen mineralization, increased with nitrogen fertilizer and were not affected by water availability. Further research is needed to better understand the opposing effects of nitrogen and water on the total nitrogen pool from mineralization and verify that the effect of soil enzymes on gross nitrogen mineralization. Lastly, although maize nitrogen uptake increased with fertilizer for both water availabilities, under limited water availability, the increased nitrogen accumulation in the plants did not lead to larger yield. This limitation was likely due to the impact of water stress during grain fill.

Technical Abstract: Nitrogen (N) fertilizer and water availability can independently stimulate or limit soil N dynamics through direct and indirect processes. Importantly, soil N mineralization (Nmin) is a major N source for maize but affected by N fertilization and water availability. We examined in-situ net Nmin, soil enzyme activity, and maize N uptake in a semiarid region of North America in response to two levels of water availability (100% and 70% crop evapotranspiration, ET) and three levels of N fertilization (22–275 kg ha-1 capturing low, optimal, and excess N fertilization. Nitrogen mineralization rates peaked relatively early in the growing season leading to asynchrony between soil N supply and plant demand. Later in the season when plant N uptake was highest, Nmin rates were high under low N with full water supply, and high under high N with limited water supply, resulting in an N fertilizer and water interaction. Soil L-leucine amino peptidase (LAP) and ß-1,4-N-acetyl-glucosaminidase (NAG), which can be indicators of gross Nmin, increased with N fertilizer additions but were not affected by water supply. Further research is needed to understand the mechanisms underlying this interaction as well as exploring if gross Nmin has a similar response. Maize N uptake increased with N fertilizer additions under both levels of water availability but was higher in the full water supply. In the limited water availability, increased plant N uptake with increased N fertilization did not translate to large grain yield increases highlighting the impact of water stress, especially during grain fill.