• Development of the knowledge base to estimate crop water productivity for food production in rainfed and irrigated conditions under drought and deficient water supply
• Introduction of effective crop water management practices at farm level to optimize water productivity and food security under deficient water supply.

The great challenge for the coming decades will be the task of increasing food production with less water, particularly in countries with limited water and land resources. While on a global scale water resources are still ample, serious water shortages are developing in the arid and semi-arid regions, as existing water resources reach full exploitation. The situation is exacerbated by the declining quality of water and soil resources. The dependency on water has become a critical constraint for further progress and threatens to slow down development, endangering food supplies and aggravating rural poverty. Water productivity for food production was raised as one of the major issues at the Second World Water Forum convened in March 2000 by the World Water Council in The Hague, the Netherlands, where a vision towards water security was presented and a framework for action to achieve this. One of its main targets was defined as the need to increase water productivity for food production from rainfed and irrigated agriculture by 30% in 2015.

Water stress affects crop growth and productivity in many ways. Most of the responses have a negative effect on production but crops have different and often complex mechanism’s to react to shortages of water. Several crops and genotypes have developed different degrees of drought tolerance, drought resistance or compensatory growth to deal with periods of stress. Highest crop productivity is achieved for high yielding varieties with optimal water supply and high soil fertility levels. However, the same varieties are often highly sensitive to water stress and will obtain low yields or fail under conditions of even mild water stress during sensitive growth periods (see figure below).

Under conditions of irrigated crop production, water supply is assumed to be maximal, as irrigation supply capacity is traditionally designed to avoid crop water stress even in dry years and to meet maximum ET needs. With agricultural water supply increasingly limited, the original assumptions can not be maintained anymore. Many schemes are routinely operated according to maximum supply conditions and lack appropriate procedures and mechanisms to adjust supply and cropping pattern to water availability. Optimal supply may achieve maximum yield, but imposing water stress can be highly beneficial in terms of economic returns as taste and quality can be favorably effected by stress. Accurate knowledge on the impact of reduced water supply on yield and quality is required to define appropriate strategies to adjust crop water supply and scheme operation according to strict economic criteria that allow the optimization of net income under limited water supply.

Drought tolerance is a necessary trait for rainfed crops under varying rainfall conditions. Farmers have developed over centuries crop genotypes and cropping systems which are well adapted to the ecological conditions and minimize risks of crop-failure. A wealth of indigenous knowledge is still available, often insufficiently recognized, when introducing new varieties and new cropping practices.

To develop appropriate strategies to optimize crop production and economic benefits, while maintaining environmental requirements, it is of much importance to assess the effects of water stress on production, yield and quality of certain crops both at experimental level as well as at farm level and to integrate new knowledge with the traditional farmers knowledge through participating research and extension.

Precise knowledge on crop response to water is essential in a range applications for policies and investment strategies at national and regional level, as well as in practical management tools at basin, scheme and farm level, as outlined below:

• To assess the impact of drought, rainfall variability and climatic change on yield, production and environment;
• to evaluate water use efficiency and crop water productivity under prevailing rain patterns and traditional farm practices and define with farmers options for improvement and appropriate strategies to optimize yields and to reduce risks of crop failure related to crop choice, planting time, soil cultivation and crop cultural practices (weeding, density , fertility, ) and to define options for water conservation and supplemental irrigation;
• to define under irrigate crop conditions water supply strategies for optimal crop production and economic returns under conditions of reduced water supply and to advise farmers to optimize timing and application rate of crop irrigation for optimal yields and income also under limited water supply;
• to define national and regional policies to meet food requirements under conditions of drought and limited water supply in rainfed and irrigated agriculture;
• to identify research programmes in crop improvement and natural resources management for improved water productivity in both rainfed and irrigated crop production, including identifying opportunities for biotechnology;

The overall objective of the proposed project will be to increase water use productivity in the farmers field in response to the objectives of the Second World Water Forum and the FAO World Food Summit 5 Years Later demand for water and food security for all:

The specific objectives of the project will be:

• To develop the knowledge base in crop water productivity under various conditions of water supply and water stress;
• To test and develop practical procedures and guidelines to appraise traditional farmers knowledge in drought management and to introduce effective water management strategies for rainfed agriculture in the farmers field;
• To develop guidelines and criteria for irrigation scheme managers, irrigation advisory services and irrigation farmers to optimize available water and effective crop water use practices at field level supply for optimal economic and environmental benefits.
• To assist national and regional research institutes in defining practical strategies for national action plans and guidelines for effective water use by establishing a global network of researchers and research institutes.

FAO developed in the seventies procedures to estimate yield response to deficit water based on an analysis of an extensive range of available research studies on crop water yield relationships. The method developed by Doorenbos and Kassam and published in the FAO Irrigation and Drainage Series No 33 in 1979, has proven over the years that its empirical approach of determining crop yield in response to water, is robust and fairly insensitive to variations in the specific coefficients for crops. In situations where the availability of site-specific data is limited, its estimated yields results compare well with those derived from more sophisticated approaches at modeling water-limited crop production.

Since the development of the FAO 33 method, a large number of studies and research results have enhanced the information and knowledge base on yield response to water. There have been significant changes in the genetic characteristics of many crops and crop types. Moreover more advanced techniques and simulation studies have allowed a more precise and in-depth analysis of crop-soil-water relationships and yield water responses.

There is a need therefore to review the methodology and to confirm - with possible adjustments - that the FAO 33 production function method should be maintained as one of the main practical methods to estimate crop water productivity and to update the crop information and parameters with the large body of research performed on crop responses to water since the FAO paper was published in 1979.

The update should include a review of the various simulation models of crop production that have been developed over the last 15 years and which, given specific soil and weather information, produced predictions of water-limited yields of the principal crops. Such models are dynamic and could also be used to calibrate the more empirical production function model for locations where the specific soil and weather data are available. Among many modeling groups, there are two major efforts in modeling crop production, readily accessible, that deserve consideration for this effort: the CERES models, now managed under ICASA (former DSSAT) which have models of about 12-14 major crops; and CROPSYST, from Washington State University, which has parameters calibrated for the major crops. Other models could be considered as recommended by experts to be consulted.

Experience has demonstrated that the transfer of many research results and new technologies has found only limited application in a majority of the farmers’ fields in particular in developing countries. Many research results have proven of little practical value, and farmers often proved more ingenious based on their long experiences in addressing drought and water stress conditions. Defining strategies well adapted to actual farm conditions, while profiting of the wealth of experience of many farmers, requires a more innovative approach integrating research results into actual farm conditions.

A participatory research and extension programme would be most appropriate to develop procedures and strategies for improved water productivity at farm level in areas with recurrent droughts and where water supply is limited.

The pilot phase of the FAO Special Programme for Food Security could provide an attractive and appropriate vehicle to evaluate the value of farmers’ practices, to validate research results and adopt appropriate procedures and conditions to introduce water use efficient methods for greater productivity.

The project that is proposed to achieve the above stated objectives will consist of different stages and procedures in which the following activities and outputs will be achieved:

1. Review of appropriate simulation methodologies to assess crop water productivity relationships by a panel of experts;
2. Adoption of procedures to process the available research results and farm water use practices in terms of crop water productivity;
3. Establishment of a global network of researchers with specific knowledge on crop water use functions and ready access to crop water research data, classified according crops and crop types;
4. Processing of crop water data by each crop group cooperating in the research network according agreed procedures;
5. Synthesis of the crop water production functions by each crop group and development of crop-specific guidelines for crop water management and productivity under rainfed and irrigated conditions;
6. Defining field procedures to collect relevant data from pilot studies in the farmers’ field and assess performance indicators for water use productivity under various socio-economic and water supply conditions in irrigated and rainfed agriculture;
7. Implementation of a pilot field programme to evaluate farmers practices and developing strategies to introduce improved water use procedures,
8. Review of field results and synthesis of experiences leading to the development of practical guidelines in rainfed and irrigated agriculture for farmers, advisory services and scheme managers.
9. Development of national strategies and action plans to promote effective water use for water and food security and the environment.

1. Identification of knowledgeable experts, collaborators and partners in the research study and assignment of a coordinator to carry out the preparatory work and coordination of inputs;
2. An advisory meeting of experts would take place at an early stage (December 2001) to advise on procedures for the review study on water productivity. The expert consultation will advise on the review of methodologies and models to be considered, procedures to process and verify research data, as well as procedures to implement a pilot project to review field practices under rainfed and irrigated agriculture.
3. Experts on individual crops are identified and asked to cooperate in the identification and processing of the data and to establish a crop-based network ensuring the inputs of other experts and institutes on the water information base for each crop. Their specific tasks will include the development of a set of crop-specific recommendations for crop water management strategies under conditions of limited water supply. The information is reviewed and given a common format by a peer group of experts, selected from the Advisory Meeting,
4. Suitable field programmes are identified for pilot testing and data verification both on regional basis through the CGIAR centers as well as at national level through national research institutes involved in water development, the national committees of the ICID and the FAO SPFS field programme;
5. Preparation of Guidelines on Water production functions based on the processed research data by a group of authors with relevant applications for different groups of users.
6. Implementation of the guidelines on effective water use in a range of linked water development projects, such as the FAO SPFS and integrated water resources management projects and irrigation schemes in which effective water use practices are introduced and tested at field level;
7. Information exchange on experiences at farm level project through networking
8. Synthesis of the findings in guidelines and training manuals for farmers, technical support staff and extension staff.

A review of the various research articles would result in the identification of persons and institutes involved in crop based water research studies.

Initial activities proposed under the programme will be carried under the FAO Regular programme and will include the preparation and organization of the expert meeting in December 2001. A coordinator and a research assistance will be assigned for that purpose to carry out a review of present status of research work.

Based on the recommendation of the panel of experts, the establishment of the network will be carried out as a web-based activity by the project coordinator and research assistant.

For implementation of the field activities extra-budgetary funding will be identified from different donors and the FAO technical cooperation programme.