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

一项创新的五年研究计划正在进行，旨在调查地下滴灌（SDI）在加拿大东部集约化蔬菜生产的潜在功效和效益。我们的假设是，SDI有一个上级的水利用效率相比，地面滴灌和高架喷灌系统，如果设计得当，可以减少养分淋溶根区以下。对于加拿大东部的矿物质和有机土壤，目前没有关于土壤表面以下滴灌线放置的最佳深度和要施用的最佳水量的设计标准，以实现最大的作物产量。这项研究结合了田间、温室和计算机模拟研究。实地研究将在麦吉尔大学园艺研究站的矿物质土壤上进行，并在蒙特利尔以南100公里的有机土壤上进行，在那里密集种植蔬菜。用甜椒（Capsicum annuum. L）和番茄（S.番茄）作为试验作物，将滴灌管安装在土壤表面以下20和30厘米处，产生两个SDI处理。安装在土壤表面的滴灌线将作为对照。三种土壤水分补充水平（100%、70%和50%田间持水量-代表3种作物水分胁迫水平）将应用于两种SDI和DI处理，产生9种处理组合，将进行统计学重复。将测量几个参数，包括作物产量和商品收成、降雨量、蒸散量、灌溉应用和土壤湿度。孔隙水样品将收集从吸力蒸渗仪在9个处理组合后，每次施肥，亚硝酸盐，硝酸盐和氨进行分析。这些数据将有助于决定土壤表面以下SDI线的适当深度，以实现最佳节水和作物产量，并减少矿物和有机土壤上的养分流失。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有效辐射），并用于为SDI和DI的每种水分胁迫条件制定作物水分胁迫指数（CWSI）。这些数据将导致一种新的技术，灌溉调度的基础上作物指标，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一个创新的作物水分生产力模型。对2种试验作物的温室研究，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的两种SDI处理下的土壤水分分布进行详细评估。计算机建模将使SDI设计标准（安装深度和发射器间距）的土壤和环境条件的范围内的推导。 该研究为加拿大和科学和工程界带来了SDI，有机土壤灌溉，CWSI和作物水分生产力建模的新发现。作物生产者、灌溉者和水资源管理者因竞争性水需求和气候变化以及水成本上升而面临水资源短缺，他们将从研究结果中受益。加拿大水果和蔬菜产业的可持续性和竞争力，每年价值15亿加元，将通过采用研究结果进一步提高。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作出贡献。

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.