Towards a Better Understanding of the Soil-Plant-Atmosphere-Water Continuum

我们的NSERC支持的研究旨在设计农业水管理系统，节约水和能源，同时提高作物生产力。目前正在进行研究，以确定作物水分胁迫的定义，方法是根据对各种植物冠层大气参数的测量，包括蒸汽压力不足、冠层温度、相对湿度、光合速率和CO2通量，建立模型。然而，我们的水管理实地研究的初步工作表明，NO2通量比CO2更具有环境意义。一氧化二氮（N2 O）是一种重要的温室气体，受施肥量和施肥时间、灌溉和排水方式以及降水的影响。高水位有助于土壤厌氧条件，从而促进反硝化作用。 我们在现场安装了静态有机玻璃室，并手动收集了注射器中的气体样本，我们带回实验室进行N2 O分析，使用气相色谱法。这是一种非常耗时和繁琐的方法，并导致实验室中的样品积压，这需要大量的时间来分析。此外，由于我们手动采样，我们经常错过峰值排放，并且无法准确捕获降雨和施肥效应。此外，由于春季解冻期间土壤温度升高，微生物活性增加，我们通常无法捕获排放物。手动收集数据还有另外两个复杂问题。首先，通量与时间不是线性的，因此数据点之间的简单线性外推会导致N2 O的错误估计。其次，我们的数据表明，在站点内的N2 O通量的巨大变化。这使我们相信，有地理空间可变的土壤微生物热点，影响通量，我们需要区分生物源的N2 O。 我们建议使用PICARRO G5131-i N2 O浓度和同位素分析仪，以克服上述挑战，并更好地了解各种土壤水分条件下的作物生产力。它可以连续快速地测量N2 O气体浓度和同位素（例如，δ15N）。通过分配歧管，我们可以同时测量N2 O浓度和同位素比例，最多可测量16个基于现场的室。分析仪的小样本同位素模块2（SSIM 2）测量土壤、植被的气体演化，以及将稳定标记物掺入活生物体，这将使我们评估微生物-土壤-植物环境中N反应的方法完全现代化。我们还将能够测量溶解的N2 O释放，这是一种未被充分报道的N2 O来源。 大约25名研究生将接受分析仪使用方面的培训。通过培训，他们将成为加拿大可持续农业先进环境管理的领导者。

Our NSERC supported research is aimed at designing agricultural water management systems which conserve water and energy, while at the same time enhancing crop productivity. Studies are being undertaken to define crop water stress by developing models based on measurements of various plant canopy atmosphere parameters including vapour pressure deficit, canopy temperature, relative humidity, photosynthetic rate, and CO2 fluxes. However, preliminary work from our water management field studies has shown that NO2 fluxes are more environmentally significant than CO2. Nitrous oxide (N2O) is a significant greenhouse gas, influenced by the rate and timing of fertilizer application, irrigation and drainage practices, as well as by precipitation. High water tables contribute to soil anaerobic conditions, thereby promoting denitrification. We installed static Plexiglas chambers in the field, and manually collected gas samples in syringes, which we brought back to the lab for N2O analysis, using gas chromatography. This was a very time consuming and tedious method, and resulted in a backlog of samples in the lab, which took an inordinate amount of time to analyze. Furthermore, since we sampled manually, we often missed peak emissions, and were not able to accurately capture rainfall and fertilization effects. In addition, we often did not capture emissions due to increased microbiological activity under warmer soil temperatures during the spring thaw. There are two other complications with the collection of data manually. Firstly fluxes are not linear with time, so simple linear extrapolation between data points leads to erroneous estimates of N2O. Secondly, our data showed tremendous variability in N2O fluxes within sites. This leads us to believe that there are geospatially variable soil microbiological hotspots, influencing fluxes and we need to distinguish biological sources of N2O. We propose to use a PICARRO G5131-i N2O Concentration and Isotopes Analyzer, in order to overcome the above challenges, and to generate a better understanding of crop productivity under various soil-water conditions. It continuously and rapidly measures N2O gas concentration and isotopes (eg. δ15N). Through a Distribution Manifold we can simultaneously measure N2O concentrations and isotopomer ratios in up to 16 field-based chambers. The Small Sample Isotope Module 2 (SSIM2) of the Analyzer measures gas evolution from soils, vegetation, as well as the incorporation of stable labels into living organisms, which will completely modernize our method of evaluating N reactions in microbial-soil-plant environments. We will also be able to measure dissolved N2O evolution, an under-reported source of N2O. Approximately 25 graduate students will be trained in the use of the Analyzer. Through their training, they will become Canadian leaders in advanced environmental management for sustainable agriculture.