The integration of site-specific measures of soil N status and climate in improving nitrogen fertilizer use efficiency in cool humid climates

人类最大的缺陷之一是未能发现和尊重生态极限。在土地管理和向环境输送养分方面尤其如此(11，17)。合成氮肥每年给环境增加1.2亿吨氮，有效地使地球上存在的活性氮翻了一番(16)。农业中使用的氮肥只有大约50%被作物吸收，其余的留在环境中(11)。氮素利用效率低下的原因是土壤中氮素流失的多种途径，以及天气事件在引发氮素流失中的作用。为了提高氮素的利用效率，我们必须更好地考虑包括土壤在内的所有氮素来源，并确保在氮素损失潜力较大的时期不会积累活性氮。提高氮肥利用效率与联合国17个可持续发展目标中的6个有关(1)。大西洋地区是这项研究的重点，因为那里的种植制度发生在低肥力土壤上，需要很高的氮肥加入量，而且非常接近脆弱的地表水和地下水系统。该地区是典型的凉爽、潮湿的农业生态系统，农业氮素对周围生态系统的影响最高。这项工作考察了气候对土壤氮素功能的影响，确定了气候在触发氮素过程中的作用，并评估了土壤氮素供应/损失的概率估计，为农业生产者和/或政策制定者提供了有用和有用的信息。溶解有机氮在控制植物获得氮素的作用和对环境的潜在损失方面知之甚少。我们将发现气候触发因素(冻结/融化、干/湿)与有机氮的溶解之间的联系，我们假设有机氮的溶解是土壤向植物供应氮素和向环境损失氮素的限速步骤。这将改善对土壤氮素供应的估计。我们将使用土壤氮素功能和气候的特定地点测量来生成基于概率的土壤氮素供应/损失的贝叶斯预测值。这些贝叶斯统计方法将建立在过去研究的基础上，并产生工具，使生产者能够整合当前气候信息和基于概率的、地理参考的土壤N供应估计，以制定特定地点、特定作物的N建议，从而提高N的利用效率并减少对环境的影响。土壤氮素功能的贝叶斯预测因子将与未来气候情景相结合，以研究气候变化对土壤氮素供应的潜在影响以及土壤氮素对环境的潜在损失。这些项目将结合实地和实验室研究，将以科学为基础的土壤氮素状况测量转化为概率的地理参考工具，农业生产者和政策制定者都可以使用这些工具来提高农业中氮素的使用效率和加拿大凉爽潮湿农业生态系统中农业的可持续性。

One of humanity's greatest short comings has been a failure to detect and respect ecological limits. This is particularly true of land management and nutrient loading to the environment (11,17). Synthetic nitrogen (N) fertilizer adds 120 million tonnes of N to the environment annually and has effectively doubled the reactive N present on the Earth (16). Only about 50% of N fertilizer used in agriculture is taken up by the crop, while the rest remains in the environment (11). Inefficient N use is a result of numerous pathways of N loss from soil and the role of weather events in triggering N losses. To improve the efficiency of N use we must better account for all sources of N, including the soil, and ensure reactive N does not accumulate during periods of high N loss potential. Increasing N use efficiency is tied to six of the seventeen UN Sustainable Development Goals (1). The Atlantic region is the focus of this research as cropping systems there occur on low fertility soils, require high rates of N fertilizer addition and are in close proximity to vulnerable surface water and groundwater systems. This region is typical of cool, humid agroecosystems which have the highest rates of agricultural N impacts on surrounding ecosystems. This work examines the influence of climate on soil N functions, determines the role of climate in triggering N processes, and evaluates probabilistic estimates of soil N supply/loss as usable and useful information for agricultural producers and/or policy makers The role of dissolved organic N in controlling the availability of N to plants and potential for loss to the environment is poorly understood. We will discover the link between climate triggers (freeze/thaw, dry/wet) and the solubilization of organic N which we hypothesize is the rate limiting step in soil N supply to plants and loss to the environment. This will result in improved estimates of soil N supply. We will use site-specific measures of soil N function and climate to generate probability-based Bayesian predictors of soil N supply/loss. These Bayesian statistical approaches will build on past research and produce tools that will allow producers to integrate current climate information and probability-based, georeferenced estimates of soil N supply to develop site-specific, crop-specific N recommendations, improving N use efficiency and reduced environmental impact. The Bayesian predictors of soil N functions will be used in combination with future climate scenarios to examine the potential impacts of climate change on soil N supply and the potential for soil N loss to the environment. These projects will combine field and laboratory studies to translate science-based measures of soil N status into probabilistic, geo-referenced tools that can be used by agricultural producers and policy makers alike to improve the efficiency of N use in agriculture and the sustainability of agriculture in Canadian cool humid agro-ecosystems.