Soil-Plant-Water Dynamics and Water Productivity Benefits of Subsurface Drip Irrigation

加拿大将开展一项创新的五年研究计划，旨在调查地下滴灌(SDI)在加拿大东部集约化蔬菜生产中的潜在效果和好处。我们的假设是，与地面滴灌和架空喷灌系统相比，SDI具有更高的水分利用效率，如果设计得当，可以减少根区以下的养分淋失。目前，对于加拿大东部的矿物和有机土壤，没有关于滴管在土壤表面以下的最佳放置深度以及实现最大作物产量的最佳水量的设计标准。这项研究结合了田间、温室和计算机模拟研究。**田间研究将在麦吉尔大学园艺研究站的矿物土壤上进行，并在蒙特利尔以南100公里处的有机土壤上进行，那里是蔬菜精耕细作的地方。采用甜椒(Capsicum annuum.L)和番茄(S.Lycopsicum)作为试验作物，将在地表以下20和30厘米处铺设滴灌管道，从而形成两个SDI处理。安装在土壤表面的滴灌管道将起到控制作用。三个土壤水分补充水平(田间持水量的100%、70%和50%--代表3个作物水分胁迫水平)将应用于两个SDI和DI处理，从而产生9个处理组合，这些组合将在统计上重复。将测量几个参数，包括作物产量和商品收成、降雨量、蒸散量、灌溉应用和土壤水分。在每一次施肥后，将从9个处理组合的吸力蒸渗仪中采集孔隙水样本，并分析亚硝酸盐、硝酸盐和氨。这些数据将为在土壤表面以下放置SDI线的适当深度提供决策信息，以实现最佳的节水和作物产量，并减少矿物和有机土壤上的养分淋失。**此外，还将测量作物小气候参数(冠层温度、气孔导度、叶片叶绿素含量和光合作用有效辐射)，并利用这些参数为SDI和DI的每种水分胁迫条件制定作物水分胁迫指数(CWSI)。这些数据将产生一种基于作物指标的灌溉计划新技术，而不是传统的土壤水分测量。此外，CWSI、节水和作物产量数据将有助于为加拿大东部开发创新的作物水分生产力模型。对两种试验作物进行的温室研究，再加上使用Hydrus-2D的计算机模拟研究，将允许对矿物和有机土壤在两种SDI处理下的土壤水分分布进行详细评估。计算机模拟将能够针对一系列土壤和环境条件推导出SDI设计标准(安装深度和滴头间距)。**这项研究为加拿大和科学界和工程界带来了关于SDI、有机土壤灌溉、CWSI和作物水分生产力模型的新发现。由于相互竞争的用水需求和气候变化以及不断上涨的水成本，面临缺水的作物生产者、灌溉者和水资源管理者将从研究结果中受益。加拿大每年价值15亿美元的水果和蔬菜产业的可持续性和竞争力将通过研究结果的采用而进一步增强。麦吉尔大学的五名研究生和几名本科生将在该项目下接受培训，从而为灌溉和农业部门培养高技能人才做出贡献。

An innovative five year research program is to be undertaken, aimed at investigating the potential efficacy and benefits of subsurface drip irrigation (SDI) for intensive vegetable production in Eastern Canada. Our hypothesis is that SDI has a superior water use efficiency compared to surface drip and overhead sprinkler irrigation systems, and if properly designed could reduce nutrient leaching below the root zone. There are currently no design criteria on the optimum depth of placement of the drip lines below the soil surface, and the optimum amount of water to be applied, to achieve maximum crop yields, for both mineral and organic soils in Eastern Canada. The research combines field, greenhouse and computer modeling studies.**Field studies will be conducted on a mineral soil at the McGill University Horticulture Research Station, and on an organic soil, 100 km south of Montreal, where vegetables are intensively cultivated. Using sweet bell pepper (Capsicum annuum. L) and tomato (S. lycopersicum) as test crops at both sites, drip irrigation lines will be installed at 20 and 30 cm below the soil surface, resulting in two SDI treatments. Drip lines installed on the soil surface will serve as a control. Three soil water replenishment levels (100%, 70% and 50% of field capacity - representing 3 levels of crop water stress) will be applied to the two SDI and the DI treatments, resulting in 9 treatment combinations, which will be statistically replicated. Several parameters including crop yield and marketable harvest, rainfall, evapotranspiration, irrigation applications, and soil moisture will be measured. Pore water samples will be collected from suction lysimeters in the 9 treatment combinations after each fertigation, and analyzed for nitrite, nitrate, and ammonia. This data will inform decisions about the appropriate depth of placement of the SDI lines below the soil surface, for optimum water savings and crop yields, and reduced nutrient leaching on mineral and organic soils.**Additionally crop-microclimate parameters (canopy temperature, stomatal conductance, leaf chlorophyll content, and photosynthetically active radiation) will be measured, and used to develop a Crop Water Stress Index (CWSI) for each water stressed condition for both SDI and DI. This data will result in a new technique for irrigation scheduling based on crop indicators, rather than on traditional soil moisture measurements. Furthermore, the CWSI, water savings and crop yield data will enable the development of an innovative crop-water productivity model for Eastern Canada. A greenhouse study with the 2 test crops, coupled with a computer simulation study using HYDRUS-2D, will permit a detailed assessment of soil moisture distribution under the two SDI treatments for both mineral and organic soils. The computer modeling will enable the derivation of SDI design criteria (depth of installation and emitter spacing) for a range of soils and environmental conditions. * *The research brings new findings on SDI, irrigation of organic soils, CWSI and crop-water productivity modeling to Canada and the scientific and engineering communities. Crop producers, irrigators and water managers who are faced with water scarcity due to competing water demands and climate variability, and rising water costs will benefit from the research findings. The sustainability and competitiveness of the Canadian fruit and vegetable industry, worth $1.5 billion annually, will be further enhanced by adoption of the research results. Five graduate students and several undergraduate students at McGill University will be trained under the project, thereby contributing to the development of highly skilled personnel for the irrigation and agricultural sectors.