Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO, 80523, USA.
Water Management and Systems Research Unit, USDA Agricultural Research Service, 2150 Centre Avenue, Bldg D Suite 320, Fort Collins, CO, 80526, USA.
Sci Rep. 2023 Aug 31;13(1):14269. doi: 10.1038/s41598-023-40459-0.
Water and nitrogen (N) are the most limiting factors to plant productivity globally, but we lack a critical understanding of how water availability impacts N dynamics in agricultural systems. Plant N requirements are particularly uncertain when water is limited because of the interactive effect of water and N on plant growth, N demand, and plant uptake. We investigated impacts of N application and water availability on plant growth and N movement, including above and belowground growth, water productivity, N productivity, N uptake, N recovery, and greenhouse gas emissions within a semi-arid system in northeastern Colorado, USA. Moderately high soil N availability depressed grain yield and shoot growth under both limited and full water availability, despite no indication of physical toxicity, and came with additional risk of deleterious N losses. Under low N availability, plant N concentrations in aboveground tissues showed greater recovery of N than what was applied in the low N treatments under both full and limited water availability. This enhanced recovery underscores the need to better understand both plant soil foraging and processes governing resource availability under these conditions. Finally, limited water availability reduced N uptake across all N treatments and left 30% more soil nitrate (NO) deep in the soil profile at the end of the season than under full water availability. Our results show that plant N needs are not linearly related to water use and emphasize the need for an integrated understanding of water and N interactions, plant foraging for these resources, and the dynamics of processes that make N available to plants.
水和氮（N）是全球限制植物生产力的最主要因素，但我们缺乏对水分可利用性如何影响农业系统中 N 动态的关键认识。由于水和 N 对植物生长、N 需求和植物吸收的相互作用，当水受到限制时，植物的 N 需求尤其不确定。我们在美国科罗拉多州东北部的半干旱系统中研究了 N 施用量和水分可利用性对植物生长和 N 迁移的影响，包括地上和地下生长、水分生产力、N 生产力、N 吸收、N 回收和温室气体排放。在有限和充分的水分供应下，适度高的土壤 N 有效性降低了籽粒产量和地上部生长，尽管没有物理毒性的迹象，但存在额外的有害 N 损失风险。在低 N 有效性下，在充分和有限水分供应下，地上组织中的植物 N 浓度显示出比低 N 处理中施入的 N 有更高的恢复。这种增强的恢复突出表明需要更好地理解在这些条件下植物对土壤的觅食和控制资源有效性的过程。最后，有限的水分供应减少了所有 N 处理的 N 吸收，并使土壤剖面中深层的硝酸盐（NO）比充分水分供应下多保留 30%。我们的研究结果表明，植物 N 需求与水的利用不是线性相关的，并强调需要综合了解水和 N 的相互作用、植物对这些资源的觅食以及使 N 可被植物利用的过程动态。
