Abstract: http://randd.defra.gov.uk/Document.aspx?Document=HL0196_9660_ABS.docx Aim of Initiative: To develop precision irrigation technologies to reduce water and energy consumption and improve post harvest quality of high value horticultural crops. Commercial and Technical Background: Irrigation of field vegetables has changed relatively little over the last 3 decades, but rising energy costs and supermarket demands for premium quality produce are forcing growers to address the impacts of irrigation variability (non-uniformity) on crop quality whilst simultaneously reducing energy and water consumption. This is not just a UK issue (Morison et al., 2007), but an international priority (Molden, 2007). Field vegetables are the most important crop in the UK after potatoes in terms of irrigated area and crop value (Weatherhead, 2007). Nearly three-quarters are irrigated using overhead methods which are inefficient in energy and water use, with consequent impacts on crop quality. Whilst drip irrigation can improve water efficiency and crop quality in some sectors (HL0165) it is not the solution for field-scale horticulture, where sequential plantings and rotational cropping are better suited to portable overhead systems. Water regulation is also impacting on production, with water availability and reliability likely to become major constraints on horticultural businesses. Growers will have to demonstrate efficient and sustainable use of water to renew their abstraction licences and comply with supermarket grower protocols. Developing innovative approaches to combine knowledge of soil, crop and equipment management practices to reduce the variability in crop quality through precision irrigation is an industry priority. The Problem/Opportunity: Making maximum use of soil moisture and rainfall, knowing precisely where and when irrigation has to be applied, and then applying it accurately and uniformly, are the fundamental steps in the ‘pathway to water efficiency’ (Knox et al., 2006). Irrigation is already an essential component in horticultural production to maximise yields, but there is growing evidence that optimised irrigation regimes also lead to improved post harvest product quality leading to reduced crop waste through the supply chain. However, growers are currently restricted in their ability to match the timing and frequency of irrigation applications to spatial and temporal variations in soil moisture and crop growth. They generally have only limited information on plant water status, rely on limited point measurements of soil as a proxy for field scale soil moisture availability; and use irrigation systems that lack the flexibility and control for variable water application. Recent developments in soil sensors, wireless telemetry and application equipment provide a timely opportunity to develop a closed-loop system capable of applying water variably across field crops on overhead irrigation systems. In addition, new techniques that rapidly measure plant water status and improved soil moisture sensing technology will allow irrigation to be scheduled from plant responses rather than solely soil water availability. The combination of using irrigation trigger points at defined physiological set points combined with a precision application system will enable significant water savings in field-scale horticultural production, with an associated reduction in nutrient leaching and energy used for pumping. Scientific Background: Vellidis et al. (2008) developed a prototype real time soil sensor for scheduling irrigation on cotton under arid conditions in the USA. This research will develop an equivalent wireless soil moisture sensor array for scheduling irrigation on lettuce and onions grown under supplemental rainfall conditions. HL0165 showed that precision application of water (using drip tape) could save up to 60% of water and that reduced irrigation regimes could improve post harvest quality of lettuce crops. However, although drip irrigation can be managed with a high degree of control, it cannot apply water variably (emitters are designed to provide uniform discharge). Overhead systems are more suited to variable rate application. In HLO168, an approach to scheduling irrigation was developed where water was applied to mitigate plant stress (assessed by perturbed stomatal behaviour). The variability in irrigation application and its impacts on crop yield and quality has been modelled by Lacey (2007), and a prototype precision irrigation system using Bluetooth technology has been developed to provide variable applications on arable crops under centre pivots (Kim et al., 2007). This research will develop equivalent technologies for use under UK conditions where growers use portable overhead booms and sprinklers. Scientific Approach – The aim is to develop an intelligent irrigation management system which integrates soil moisture sensing, wireless communication and variable delivery technology, to improve crop quality and reduce water consumption and other environmental impacts. We will use small-scale instrumented university experimental sites to (i) design, develop and test a real time wireless soil moisture sensor array, and (ii) to evaluate the role of plant water status measurement techniques (including thermal imaging) for monitoring varying levels of crop water stress, using lettuces and onions as reference crops. The crop measurements will be used to calibrate the soil moisture sensor readings to define trigger irrigation points. Technologies for applying water variably from both booms and valved sprinklers and their associated control systems will be then developed and tested under bare soil conditions. The soil sensing, crop monitoring and variable application technologies will be coupled to form a ‘closed loop system’ which will be evaluated under contrasting crop, soil and agroclimatic conditions at two grower sites. This will include an assessment of system performance, practicality (ease of management), impacts on yield and post harvest quality, and economic appraisal. The fieldwork will inform decisions regarding technology transfer to other horticultural crops