Contents & Foreword, Characterizing And ... - IRRI books

ing, remote sensing, and computing technologies have further strengthened the applicabilityof AEZ in agricultural planning and development. Many countries have usedthe AEZ methodology (FAO 1994) in assessing land productivity and populationsupportingcapacity; in land evaluation and land-use planning; in assessing environmentaldegradation due to agricultural production; and in research planning, technologytransfer, farming systems analysis, and recommendations for input applicationand supply. Detailed information on these applications was published in the FAO’sWorld Soil Resources Report Number 75 (FAO 1994).Application of the characterization and classification of the environments ofagricultural production has recently been extended to quite a new area: the evaluationof investments in agricultural research. The methodology for evaluating alternativeresearch investments calls for assessing the impacts of past research on production(ex post analysis) and the possible or potential impact of the currently proposed researchalternatives (ex ante analysis). Characterizing and classifying the environments,especially those that employ the AEZ methodology, can provide quantified inputs tosuch assessment (Pardey and Wood 1991, Wood and Pardey 1993). Dividing geographicspace into AEZs provides an estimate of the area that could benefit from theresults of the proposed research investments. The homogeneous conditions undereach AEZ, on the other hand, facilitate quantifying the response to (or outputs of) theapplication of new technologies resulting from the proposed research investments.Research investments could then be disaggregated to commodities, subtypes, environments,and problem and discipline domains.For example, investments in rice research can be grouped into irrigated, rainfedlowland, upland, and deepwater and tidal wetland, and then into genetic improvement,crop management, and crop protection. The products of the research investmentscould be further classified into non-site-specific (applied equally to all AEZs),site-specific (applied to only one AEZ), or multivariable site-specific (variable AEZs).Rice production factors as guidelines for environmental characterizationVariety, ecological conditions during the growing season, and the socioeconomic factorsthat affect farmers’ crop management determine the yield of a rice crop. Thefactors affecting rice production have undergone substantial evolution during the past30 years. This requires more attention to the classification and characterization of theenvironments of rice production in the future.Rice varietal developmentThe rapid growth in world rice production during the 1980s (Table 1) came mainlyfrom the gain in productivity. The results of the maximum yield studies carried out byIRRI during the 1970s showed that, in tropical climate areas, the potential yield ofrice varieties was about 3.7–6.8 t ha –1 in irrigated ecologies, 2.5–4 t ha –1 in rainfedlowlands, and 2 t ha –1 in upland and other ecologies (Table 5). Cassman et al (1997)reported that yields of 4 to 5 t ha –1 are normally obtained in irrigated areas in severaltropical countries. The average yields in 1997 in major rice-producing countries such42 Van Nguu Nguyen