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Characterizing and understanding rainfed environmentsBook is availableCHARACTERIZING AND UNDERSTANDING RAINFED ENVIRONMENTS Proceedings of a workshop, 5-9 December 1999 Edited by T.P. Tuong, S.P. Kam, L.Wade, S. Pandey, B. Bouman, and B. Hardy Istiqlal Amien and Irsal Las Limited suitable land for rice production in the past has forced the development of terraced and bunded rice fields at a higher elevation. Because the rice-cropping system lacks terrestrial water resources, it totally depends on available rainfall. Java, North Sumatra, and South Sulawesi have the largest areas of rainfed lowland rice fields, 796,900, 210,300, and 259,100 ha, respectively. Because of high competition for space, rainfed rice area is steadily declining on Java but is relatively stable outside Java. A high proportion of the rainfed rice area is in the northern part of Java and eastern part of South Sulawesi. The soils of rainfed areas in West Java were formed from acid tuft. In the other provinces of Java and South Sulawesi, the soils were formed from limestone or marine sediments. Less fertile soil that is low in P and K and the low adoption of modern technology in rainfed areas resulted in lower rice yields. Yields in rainfed areas were 10% to 25% less than the average yield in Java and 15% to 20% less than the average yield in South Sulawesi. Yield levels of lowland rice on Java are inversely related to the proportion of rainfed lowland rice areas. With monsoonal rainfall patterns, the rainy season begins in October in West and Central Java, in November in East Java, and in March in South Sulawesi. West Java and South Sulawesi have no distinct dry period, while in Central and East Java the dry period varies from 4 to 5 mo. During El Niño years, the rainy season comes about a month later, with rainfall less than 70% of that of normal years. Dependence on rainfall also makes rainfed rice more susceptible to drought, particularly during El Niño years. This rainfed rice system helps reduce water runoff during the rainy season, but differs with deep-rooted vegetation, because the water retained is mostly lost through evapotranspiration. In the increasingly globalized economy, labor shortages and more competitive markets threaten the sustainability of the rainfed rice system. A. Boling, T.P. Tuong, B.A.M. Bouman, M.V.R. Murty, and S.Y. Jatmiko The typical rainfed cropping system in Central Java includes a dry-seeded rice crop grown from November to February (gogorancah), followed by a transplanted rice crop from March to June (walik jerami). Earlier studies showed that the yield of the walik jerami crop was lower and less stable than that of the gogorancah crop. This study assessed the climatic and agrohydrologic (groundwater depth) constraints to rice production and explored management strategies to increase the yield and yield stability of the double-rice cropping system using the crop growth simulation model ORYZA. The model was validated with data of field experiments in 1995-96 in Jakenan. Long-term simulation of potential and rainfed rice yield of cultivar IR64 was carried out on a 15-d planting interval for the period 1977-98. Three water table depth scenarios (medium, shallow, and deep), which were derived from 1995 to 1999 measurements, were used. The average simulated potential yield of walik jerami rice (about 7 t/ha) was higher than that of gogorancah rice (about 6 t/ha), indicating that radiation and temperature are not the determinants of the observed relatively low yields of walik jerami rice. Simulated yields of rainfed rice sown with a shallow water table depth in mid-November-February equaled the potential yield. Rainfed rice yield was reduced by 45% in the medium water table scenario and by 70% in the deep water table scenario. With medium water table depths, simulated rainfed yields of walik jerami crops declined sharply if planted later than early March. Supplemental irrigation increased the yields of rainfed walik jerami crops. The combined yields of gogorancah and walik jerami rice could be increased by using shorter-duration varieties. The results highlight the critical planting dates of the walik jerami crop, and indicate the potentials of using on-farm reservoirs and of growing shorter-duration varieties to increase the combined yields and yield stability in the area. Planning and managing rice farming through environmental analysis K. Borkakati, V.P. Singh, A.N. Singh, R.K. Singh, A.S.R.A.S. Sastri, and S.K. Mohanty Environmental analysis provides insights into planning and managing rice farming according to the prevailing conditions. This helps in developing situation-specific technologies and in selecting areas suitable for the application of promising technologies, particularly in rainfed conditions. Studies carried out in eastern India characterized and classified the rainfed rice area in different rice ecosystems and subecosystems and elucidated the main problems and opportunities for enhanced productivity in them. A detailed analysis of the principal rice subecosystems provided the periods and quantities of water surplus and deficit and moisture use and recharge patterns along with other climatic variables during the rice-cropping season. This information was used for selecting the technological interventions that were considered suitable for managing rice farming in such areas. The interventions were compared with the farmers' normal practices by monitoring crop performance at selected locations in two rice ecosystems. Regional land-use analysis to support agricultural and environmental policy formulation B.A.M. Bouman, R. Roetter, R.A. Schipper, and A.G. Laborte Characterizing rainfed environments is not a goal in itself, but it depends on the type of information to be generated. It needs to be based on a sound understanding of the prevailing biophysical and socioeconomic processes at the field, farm, or regional level. Conflicts in land-use objectives such as food security, farmers' income, employment, and environmental protection are one reason for local governments to initiate active land-use policies. Characterizing socioeconomic and biophysical conditions is an essential part of methodologies for land-use studies that address policy design, formulation, and implementation. Methods and data requirements depend on whether information is needed for identifying current land-use problems, projections of current trends, land-use explorations under changed policies, or feasible interventions to achieve identified objectives. In this chapter, we introduce regional characterization as required for resource assessment and description of production activities in methodologies for future-oriented land-use studies. This is illustrated by two different case studies: (1) an exploratory study on Ilocos Norte Province, Philippines, and (2) a predictive study on the Northern Atlantic Zone, Costa Rica. Both studies use optimization models with quantified input-output relations of production activities as input. All calculations refer to land units considered as homogeneous in biophysical and socioeconomic conditions. Within the modeling framework, (multiple-goal) linear programming techniques, technical coefficient generators, and geographic information systems are applied. In the exploratory study for Ilocos Norte, the focus is on opportunities for increasing food security and income if water constraints could be partially removed by either water sharing or expansion of irrigated areas. The aim of the Northern Atlantic Zone study is to predict land-use changes as affected by the introduction of policy measures that stimulate forest conservation and reduction of biocide use. Both types of study aim at identifying options and quantifying trade-offs among conflicting goals. The type, accuracy and spatial resolution of required input data differ considerably, however, according to agroecological diversity and different study objectives. Both exploratory and predictive land-use studies have in common that they synthesize fragmented agricultural knowledge and integrate data on resources over time and space. In rainfed rice areas, the high temporal and spatial variability of production resources complicates the analysis. Farmers' diverse responses to climatic and economic risks must be taken into account, which eventually demands stronger links between on-farm research and operational research for meaningful policy formulation and implementation. A. Clough, I.P.G. Widjaja-Adhi, J. Sri Adiningsih, A. Kasno, and S. Fukai Extractable soil phosphorus (P) and potassium (K) mapping began in Indonesia to define soil fertility in lowlands and uplands that were under rice or likely to be brought under cultivation. These maps, however, have not been published and have therefore been largely inaccessible to researchers outside of Indonesia. This chapter reviews the history of soil P and K map production in Indonesian lowlands and uplands, how mapping has been used to improve P and K fertilizer recommendations in mapped regions, and limitations of the present mapping approach in determining accurate P and K fertilizer requirements. The latest edition of soil nutrient status maps produced in 1998 covers all the lowlands of Java, Lampung in southern Sumatra, and some of the smaller outer islands with a scale of 1:250,000 or 1:500,000. The soil P and K status of the lowlands has been defined as low, medium, or high based on the responsiveness of rice crops grown in field trials to fertilizer P and K. Trials and soil surveys have shown that there is a good relationship between expected P and K requirements and actual P and K responses in lowland rice grown in soils with a low P and K fixation capacity. The maps, however, have limited application in lowland areas with high fixation capacity and their low resolution can lead to fertilizer recommendations being inaccurate. Despite these limitations, soil P and K mapping in lowlands has resulted in the blanket recommendations given in the 1960s being replaced by recommendations specific for small regions within provinces. Few extractable soil P and K maps have been developed for upland rice-cropping regions. The usefulness of soil P maps as a tool for developing fertilizer recommendations is limited in uplands because many soils have high P sorption capacity, particularly in Lampung. Fertilizer recommendations for upland rice cropping are still broad, especially for K. Christopher M. Edmonds and Suan Pheng Kam This chapter reviews research incorporating socioeconomic and biophysical variables into analysis to characterize rainfed rice environments. The use of geographic information systems (GIS) as a tool for integrating these two types of data is highlighted. GIS starts as a useful tool for organizing and displaying geo-referenced social and economic data. The increasing ease of use of GIS software and improvements in geographic positioning systems and remote-sensing technology facilitate the generation of more accurate, spatially referenced data that can be integrated into analyses of agricultural practices and outcomes. GIS software, combined with other software, provides analytical techniques for converting distinct types of biophysical and socioeconomic data to a common scale amenable to analysis as an integrated database. These techniques are outlined. A final area of GIS application in socioeconomic analysis involves linking GIS analysis with other modeling techniques. Econometric modeling and linear programming models using spatially referenced biophysical and socioeconomic data are examples of this type of research. In the second part of the chapter, we review research that the International Rice Research Institute is carrying out in the Mekong River Delta of Vietnam in collaboration with the Institute of Agricultural Sciences in Ho Chi Minh City. The research applies geo-informational techniques and methodologies, and review of it enables consideration of the material covered in part one. Here, we develop a spatial economic model of crop choice and land-use intensity to provide an analytical framework for empirical examination. Empirical estimates provide insight into the roles that biophysical and socioeconomic constraints play in explaining changes in land use and productivity, and enable exploration of the interrelation between biophysical and socioeconomic production constraints. Random effects probit estimates show which factors influence farm land use. This estimator uses the panel structure of the data, and provides robust estimates. Ordered probit and multinomial logit estimates of cropping intensity and cropping pattern adopted were carried out using single years of the survey to enable estimation of the effect of time invariant characteristics on these outcomes. Findings from these estimates are reviewed and extensions and future applications of GIS econometric integration are considered. Characterizing rice pests in the rice-wheat system of India F.A. Elazegui, R.K. Srivastava, H.M. Singh, and S. Savary The relationships among rice-cropping practices, biotic constraints, and rice yield in the eastern part of Uttar Pradesh, India, were studied. The investigation was conducted at the center of a geographic area representative of the rice-wheat system of South Asia, and covered a large diversity of production situations undergoing intensification. A survey procedure was used to collect data for three consecutive years (1993-95) on 251 individual farmers' fields. The analytical approach used characterized relationships among variables using cluster and correspondence analyses. Seven patterns of cropping practices were distinguished, reflecting a wide variation in production situations, especially in terms of use of fertilizers and manure, and degree of water control. Six types of disease profiles, four insect injury profiles, and four weed infestation patterns were identified. Correspondence analysis, based on patterns of cropping practices and injury profiles, yielded a path of increasing attainable yield associated with varying levels of intensification and combinations of injuries. The analysis highlighted the effect of changes in patterns of cropping practices on injuries caused by weeds, brown spot, sheath blight, and deadhearts. The significance of these findings with respect to current and future integrated pest management needs is discussed. S. Fukai, J. Basnayake, and M. Cooper Characterizing and understanding the nature of the limitations imposed by rainfed lowland environments within a target region are important for developing an efficient rice breeding program. Major factors determining the environment as it influences plant performance are soil properties and water availability. Rainfall is a major determinant of the water environment, but its seasonal variability is high in northeast Thailand. Simulation models are useful in determining many features of the paddy water environment, as they can readily estimate water availability as a probability function by using past rainfall patterns as inputs. The RLRice model was developed for simulating the paddy water balance and growth of cultivar KDML105 for the rainfed lowlands in Thailand. The model was used to quantify the water balance of paddies of the several locations used in the rainfed lowland rice breeding program in northeast Thailand. Yearly variation in simulated yield at any location was related to variation in rainfall during crop growth. However, sensitivity analysis results showed that simulated yield varied greatly with changes in components of the water balance, particularly the deep percolation rate, lateral water movement, and initial water level at transplanting. Simulated yield was generally associated with the time of disappearance of water relative to flowering, and the depth of the free water level at flowering. The simulation results indicate a strong interaction of genotype and water environment through variation in water availability in relation to phenological development of each genotype. Y.T. Garcia, M. Hossain, and A.G. Garcia Myanmar's rainfed rice land covers 79% of its total cultivated rice area, which translates into about 4 million hectares, one of the largest in the world. Because of a lack of irrigation facilities, rice is generally grown once a year during the monsoon season. A study in the Ayeyarwardy Delta, a major rice-producing area in southern Myanmar, was conducted to characterize the different production systems of rice farmers. The study also investigated the operations of the output and input (i.e., land, labor, and capital) markets and how farmers' access to these markets shaped the distribution of income and resources in the village economy. The biophysical and socioeconomic factors leading to the adoption of new rice-based technnologies, such as summer rice, double monsoon rice, the use of high-yielding varieties, and rice-fish culture, were identified. Furthermore, biotic and abiotic factors that significantly constrained rainfed rice production were evaluated in terms of reduction in rice yield and productivity. Alternative management practices and policy options were proposed to help minimize the adverse effects of these constraints. D. Harnpichitvitaya, G. Trébuil, T. Oberthür, G. Pantuwan, I. Craig, T.P. Tuong, L.J. Wade, and D. Suriya-Arunroj For coarse-textured soils of high subsoil permeability, research has demonstrated the benefits of subsoil compaction for improved water- and nutrient-use efficiency in rainfed lowland rice (Oryza sativa L.). To better define soil conditions suited to this subsoil compaction, on-farm experiments were carried out on soils varying in subsoil clay content. Rice (cv. KDML105 in 1993 and cv. RD6 in 1994) was grown in main plots comparing shallow dry tillage without compaction, shallow dry tillage with subsoil compaction, and deep dry tillage with subsoil compaction. Soil was compacted in seven farmers' fields in the south of Ubon Ratchathani Province, with 10 passes of a vibrating road roller on 19 and 23 May 1993. The effects of subsoil compaction on changes in soil physical and hydrological properties differed according to subsoil clay content, which ranged from 1.4% to 12.0%. Subsoil compaction decreased soil hydraulic conductivity sufficiently for fields with subsoil clay content greater than 2%. When subsoil clay content was higher than 10%, the justification for using relatively costly subsoil compaction was questionable, as the hydraulic conductiviy was already low and the gains in water-storing capacity seemed limited. Based on these results, proportions of soils with subsoils of <2%, 2-5%, 5-10%, or >10% clay were mapped using geographic information systems for an area of about 40,000 ha within the Ubon Ratchathani Land Reform Area. About 40% of the mapped area had subsoils with clay % between 2 and 10, suggesting that substantial areas could be suitable for subsoil compaction. More investigations are needed to assess its economic and social acceptability, to better understand variability and probability of response, and to further refine soil suitability in relation to clay type, clay content, and groundwater changes at the toposequence level. Gary C. Jahn, Pheng Sophea, Pol Chanthy, and Khiev Bunnarith Because rainfed lowland rice (RLR) accounts for 86% of the rice-growing area of Cambodia, it is important to investigate the biotic constraints to rice in this ecosystem. Over 3 years, a total of 73 RLR fields in Cambodia were studied to determine the effect of pests on destabilizing Cambodian RLR yields, which pests and pest combinations affect RLR yields, and how cropping practices affect pest levels. Pests included insects, weeds, and diseases of rice. Pesticides were not used in any of the fields in this study. Information on crop characteristics and biotic constraints was gathered at four crop development stages: tillering, booting, milk, and maturity. The incidence of damage caused by insects and diseases was recorded from 10 hills chosen randomly from each field. Weed infestation was recorded as the percentage weed cover in three 1-m2 areas. The rice yield of each field was estimated from an average of three randomly selected 10-m2 areas. Correspondence analysis was used to characterize the patterns of cropping practices, pest infestations, environmental conditions, and yields. The results of this analysis generated testable hypotheses about the factors contributing to pest problems. Fields of early duration rice tended to have low levels of hispa and high levels of Pentatomids, while late-duration fields had high hispa and low Pentatomid levels. Fields without standing water had higher than average levels of weeds, cutworm, hispa, and Pentatomids. Brown spot and narrow brown spot were the only diseases observed frequently enough to make inferences about their relation to cropping practices. As a component of systems research in rice plant protection, this study assisted in predicting the effects of cropping practices on pest infestations. These techniques have several limitations, however: the danger of drawing false conclusions, difficulties in interpreting results, insufficient attention to the soil type and relative rates of fertilizer, the inability to capture time adequately as a variable, the lack of information on the relative contribution of pests to variation in yield data, the incomplete coverage of pests, and the fallibility of observers. Each limitation is discussed in detail. The results of this study contributed to an assessment of relative pest importance and thereby helped prioritize research to develop integrated pest management recommendations. P.K. Joshi and Suresh Pal In a scarce and dwindling research resource scenario, characterizing production environments is a prerequisite for allocating resources more efficiently and developing a demand-driven research agenda for wider impact. This study intends to illustrate how characterization of a production system can facilitate efficient allocation of research resources. The objectives are twofold: 1) characterize the rainfed rice production system and identify existing and potential production constraints, and 2) assess research programs in an ex ante framework to allocate resources more efficiently and meet national objectives. The study has been undertaken in the rainfed rice production system, which is largely confined to eastern India. This production system lagged far behind the Green Revolution belt in agricultural development. It has now been recognized that future sources of agricultural growth lie in the rainfed rice production system. Therefore, investment in agricultural resources should be able to tap the potential of this production system. It has been characterized based on its agroclimatic features and the economic contribution of important enterprises. Characterization has aimed to delineate a homogeneous production environment to better understand common production constraints, identify technological options to alleviate these constraints in a target domain, and accelerate adoption to increase the impact of research resources. Five criteria were used to assess potential technological options in the ex ante framework: efficiency, household food security, gender issues, crop diversification, and sustainability of natural resources. These criteria have been considered important for their contribution to meeting the socioeconomic and environmental objectives in the rainfed system. The impact of efficiency has been measured using the economic surplus approach and quantifying the net present value and internal rate of returns for each technology option. Other criteria have been assigned ranks between 1 and 5 depending on their contribution. The ex ante assessment of various programs and technological options in the rainfed production system noted that the research agenda was biased in favor of a few commodities and ignored some important and potential activities. Reallocation of research resources has been proposed to develop demand-driven technological choices. The characterization of the production system also helped to identify niches for disseminating potential technological options in the target domain. Nguyen Tri Khiem, Sushil Pandey, and Nguyen Huu Hong Low food security, high population growth, and environmental degradation are some of the major problems for agricultural intensification in the uplands of Vietnam. Although Vietnam has now become a major rice exporter, food production in these remote upland environments is insufficient to meet the needs of the country's growing population. To increase farmers' incomes and their access to food, the government of Vietnam has encouraged production of cash crops in uplands through investments in marketing infrastructure and institutional reform. Using farm-level survey data, this chapter examines the effects of improved access to markets and improvements in lowland productivity on land-use intensity, labor productivity, and food security in the uplands. The results indicate that these changes have reduced the intensification pressure on uplands and generally improved the food security of upland households. Constraints to the adoption of modern varieties of rice in Bihar, eastern India Anjani Kumar and A.K. Jha The introduction of high-yielding modern varieties (HYVs) and seed-fertilizer technology in agriculture during the mid-1960s has led to a marked increase in the growth of agricultural output and has been instrumental in transforming traditional household agriculture into modern, commercial agriculture in some agriculturally developed states. The rainfed rice production system, which is largely confined to the eastern part of India, lagged far behind the Green Revolution belt in agricultural development and prosperity. Of late, it has been recognized that future sources of agricultural growth lie in this region. The adoption of modern varieties and associated technologies seems to offer an opportunity to increase output and income substantially. But even now, the pattern and pace of adoption of modern rice varieties and other component technologies have had only partial success in the rainfed rice system. Several biotic and abiotic stresses and socioeconomic and institutional constraints limit their adoption in the rainfed rice system. This study aims to analyze constraints to the adoption of modern varieties and other component technologies in the rainfed lowland ecosystem of Bihar. Both cross-sectional primary data and time-series secondary data were used. The bulk of rice is harvested in the kharif season, which suffers from the vagaries of the monsoon characterized by drought or floods and vulnerability to pests and diseases. The technical constraints to the adoption of modern varieties and component technologies are highly variable according to soil-water relationships, which differ from one ecosystem to another. The lack of tolerance for submergence, insect pests such as gall midge and brown planthopper, and diseases such as tungro, sheath blight, and bacterial blight are likely to be important obstacles inhibiting adoption in the rainfed lowland rice ecosystem. Several studies have reported the unavailability of modern varieties as the major limitation to their adoption in the rainfed rice production system. Bihar also suffers from outdated tenurial relations that adversely affect adoption. A related problem in the entire eastern region is the fragmentation of holdings. There is a need to undertake tenurial reforms in a large way and simultaneously consolidate holdings. In addition to the unavailability of modern varieties, their poor threshability and thatchability, the requirement for additional capital and labor, excessive weed infestation, the lack of timeliness or availability of fertilizer, and lack of credit along with knowledge and cultural practices may be instrumental to their slow adoption in this region. The adoption of component technologies such as fertilizer and pesticides seems to have been affected by the adulteration prevalent in the market. The input delivery system is very weak in Bihar. The region also lacks research and development and appropriate extension services. Poor roads, communications, and market infrastructure are also important constraints. Addressing some of these constraints through appropriate research and policy intervention could have a large impact on the adoption of modern varieties and their component technologies. Economics of intensive rainfed lowland rice-based cropping systems in northwest Luzon, Philippines M.P. Lucas, S. Pandey, R.A. Villano, D.R. Culannay, and T.F. Marcos Farming in the rainfed lowlands of Ilocos Norte, Philippines, is highly intensive, diversified, and commercialized. The cropping system is predominantly rice-based in the wet season and high-value cash crops are grown during the dry season. The profitability of cash crop production has encouraged farmers to use high levels of purchased inputs such as chemical fertilizers and pesticides. Concerns are being raised about the long-run sustainability of such intensive systems. This chapter assesses the sustainability of such systems using a total factor productivity analysis. The trend in total factor productivity was positive (1992-95) initially but then became negative (1996-97). However, the total factor productivity estimates for six years do not show any clear negative trend. Groundwater pollution, particularly with NO3-N, has occurred as a result of the excessive use of fertilizers on dry-season crops. If the effect of this negative externality were also captured in the total factor productivity estimates, the decline for recent years could have been sharper. Although fluctuations in total factor productivity within the short period analyzed may be attributed mainly to climatic factors, technological interventions for improving input-use efficiency are nevertheless needed to reduce both the input cost and the contamination of groundwater. C.G. McLaren and L.J. Wade In heterogeneous rainfed environments, cultivar performance interacts with crop management, soil type, topography, and agrohydrology to complicate the task of selecting better-adapted cultivars. To make consistent progress with selection in the presence of these genotype by environment interactions (G × E), it is important to clearly identify the target population of environments and to know how well actual test environments represent this population. This chapter evaluates a methodology for using measurements on a set of reference lines to classify sites according to previously identified response patterns for a target population of environments. Strategies for choosing reference lines, classifying new sites, and deducing their environmental characteristics are examined. The results showed that the reference set was able to capture repeatable G × E patterns provided it contained representatives of all discriminatory genotype groups. The methodology for characterizing new environments on the basis of reference line responses relied heavily on an ability to impute missing values. Although no optimal solution was available, a heuristic solution in the pattern analysis algorithm was satisfactory. Reference lines should be chosen based on how well they match the discriminatory pattern of the genotype group, their agronomic features, knowledge of their physiological responses, and practical issues such as the availability of seed. Based on this analysis, we conclude that a series of small field trials at many locations could be employed to obtain a useful characterization of new environments and allow breeders to weight responses of test lines appropriately. If detailed physical and climatic measurements are also made in these environments, the responses can be integrated with geographical information, physiological understanding, and crop modeling to quantify environment frequency, predictability, repeatability, and risk. Characterizing environments for sustainable rice production Van Nguu Nguyen Growth in the world's rice production has slowed down. Since 1990, the growth rate of rice production has been lower than that of the population. This indicates the need to increase efforts to improve rice productivity and bring more land area under rice cultivation. Substantial efforts have been made to characterize and classify the environments for agricultural production in general and for rice production in particular during the past three decades. Major efforts in the characterization and classification of these environments are reviewed and selected examples of the contribution of these exercises to rice production via the development of rice technologies, expansion of rice area, transfer of rice technologies, and others, such as the assessment of investments in agricultural research, are provided and discussed. Rice production factors such as varieties, water and land/soil resources, insects and diseases, socioeconomic issues, and global climate have also evolved substantially during the past 30 years. A new generation of rice varieties with higher yield potentials and better resistance to abiotic and biotic stresses has been developed using hybrid rice and biotechnology. The increasing deficiency of nutrient elements and pressure from insects and diseases have been observed in intensive rice production systems. Socioeconomic factors such as labor availability and wages and availability of inputs and credits have changed with improvements in the economies of rice-producing countries. The global climate has been warming and discussions cover the implications of these changes for the suitability of rice production under different environments. The globalization of the world economy and the decline in public investments for agricultural research activities require that future efforts in characterization and classification be evaluated in terms of returns to agricultural production. Discussions refer to the issues affecting the efficiency and applicability of characterizing and classifying the environments of rice production such as universality, completeness, objectivity, and scales and costs of the exercises. T. Oberthür and Suan Pheng Kam Previous studies that assessed the soil resources in northeast Thailand create the impression that soils are universally infertile because of their light texture and low inherent nutrient contents. In reality, variations within micro-catchments are sufficient to influence land productivity factors over short distances. This chapter describes a study carried out to examine soil variability in the rainfed lowlands of northeast Thailand and to develop quantitative methods of spatial prediction that provide useful soil resource information for agronomic management. Our methodology is based on geostatistical mapping, using soil data collected in soil surveys supplemented with less costly auxiliary information. The auxiliary information included knowledge of local farmers and soil experts about soil-landscape relations (providing a 5-category classification referred to in this study as the updated farmers' field classification, or UFFC). A soil sampling scheme was devised equivalent to that employed for producing soil maps at a mapping scale of 1:50,000 to 1:100,000. Hence, application of the proposed method in areas that have been mapped at these scales will only require a reanalysis of existing data and collection of complementary data at lower costs. Soils of loamy sand or loam texture were found in many parts of the study region, indicating that the soil texture of these soils is not altogether unsuitable for rice cultivation. Conventional statistical analysis of the soil survey data reveals very high spatial variability that cannot be ignored. Many topsoil and subsoil properties related to nutrient availability (Bray-II-P, cation exchange capacity, exchangeable bases) had large coefficients of variation (CVs), including those properties that are considered relatively stable, such as organic matter and clay content. Further statistical analysis shows that this soil map only accounts for less than 8% of the variance in measured soil properties, not enough to provide agronomically important information. There was no discernible distinction in soil fertility characteristics among the mapped soil types. The UFFC accounted for higher proportions of the total variance (ranging from 0% to 43% for both soil depths), and indicated that soil productivity declines in the order alluvial fields > fields in low topographic position > fields in medium and high topographic position > fields with upper, deep sandy horizons. Geostatistical indicator approaches that can either use or ignore auxiliary information were adopted for modeling of soil heterogeneity to enable estimation and mapping of mean, median, conditional variance, and conditional CV, and also of the 0.2- and 0.8-quantiles of the conditional cumulative distribution function. Quantile maps are very useful for mapping soil properties tailored to specific land management questions. Maps produced without auxiliary information show distinct spatial distribution patterns of average clay, silt, and sand contents in relation to the regional physiography. Maps generated with auxiliary information reveal more spatial detail; texture changes gradually and follows the local topography and drainage patterns. These maps assign much land (25%) to a soil texture class that is suitable for rice production (loam and heavier). In conclusion, our results depart from the general belief that soils of the Korat Plateau are universally coarse-textured and infertile. The reliance on soil maps has contributed to the long-held views about soil texture in northeast Thailand. Our maps strongly support an alternative hypothesis of soil genesis in the Korat Plateau that combines colluvio-alluvial erosion processes over short distances and in situ soil development with long-range Quaternary alluvial sedimentation. Characterizing rainfed rice environments: an overview of the biophysical aspects V.P. Singh, T.P. Tuong, and S.P. Kam The literature reveals that rainfed rice environments have been characterized for various purposes at differing scales using a range of techniques. This chapter reviews the biophysical aspects of characterization undertaken in rainfed rice environments, more specifically at sites of the Rainfed Lowland Rice Research Consortium. It presents the status of the work done; provides an inventory of techniques applied; discusses scale, variability, and accuracy; pinpoints gaps in knowledge; and provides future directions for work from which these sites can benefit. The chapter brings out commonalities of characteristics across rainfed sites, provides insights into which issues new technological developments should focus on when addressing major limitations to production enhancement, and identifies opportunities for making future work more efficient and relevant to needs. Examples for each of these aspects are drawn from case studies in the rainfed rice regions, and specific cases where environmental characterization has made a significant impact on national systems are cited. Weed communities of gogorancah rice and reflections on management H. Pane, E. Sutisna Noor, M. Dizon, and A.M. Mortimer Developing strategies to protect rice yields in the long term involves understanding the structure and dynamics of weed species in response to management. Where weed control is imperfect and farmers change rice crop establishment methods and control tactics, weed shifts can occur. Furthermore, in rainfed rice, the inherently complex abiotic nature of the cropping environment may result in variation in weed composition. A survey of the weed communities remaining after farm weeding practices was conducted during booting of gogorancah rice (dry-seeded bunded rice) in rainfed lowland areas of Pati and Rembang, Indonesia. Counts were made of all weed species present in four randomly placed 1 sq. m. quadrats at low, mid, and upper points of the land toposequence in fields at each of 25 farm sites. In addition, soil nutrient status (pH, N, P, K, and organic matter) at each site was measured. Fifty-six weed species covering 18 families were recorded. The average total weed density was 175 plants per sq. m., with the greatest number of species occurring in upper toposequence locations. Weed communities remaining after farmer weeding at the upper and mid positions of the toposequence were broadly similar in species composition (Lindernia species, Echinochloa colona, Fimbristylis miliacea, and Murdannia nudiflora). These differed from those at the base of the toposequence, which was dominated by Ammania bacifera, E. colona, F. miliacea, and Leptochloa chinensis. Cyperus species were also abundant across the toposequence, but differed in relation to position. Cyperus tenuispica at the top was replaced by C. iria in the middle, and, at the lower points, C. difformis was predominant. L. chinensis, a competitive grass weed, was also abundant in sites at the bottom of the toposequence. Canonical correspondence analysis was used to examine interrelationships among sampling sites based on species composition and nutrient status. Sites at the base of the toposequence were delineated sharply from those in the mid and upper positions, in which there was greater similarity in weed flora. Multivariate analysis showed that sample sites differed in soil nutritional status, especially for P and pH, which in turn was reflected in species composition. The results indicate that, under current weed management practices, the residual weed flora is strongly governed by hydrological factors with respect to toposequence in addition to soil factors. Future research and weed management options are discussed in the context of this baseline characterization of weed communities. Thelma Paris, Abha Singh, Mahabub Hossain, and Joyce Luis This chapter uses gender analysis in characterizing and understanding farm-household systems in typical rainfed lowland rice villages in Faizabad district in eastern Uttar Pradesh, India. It uses different methods of data collection such as household surveys (structured and unstructured interviews), the participatory rural appraisal, and focused group interviews. Results of the study reveal that small farming households from the lower caste tend to exploit their female family members to meet competing labor demands between farm and home-based activities. Women from the lower caste provide 60% to 80% of the total labor input in rice production. They participate in almost all rice operations, except in land preparation and application of chemicals. When valued, the labor contributions of female members on their own farms and through exchange arrangements make up about 20% of the total labor costs in rice production per hectare. Women's labor is also crucial to nonrice crops and livestock, which are integral in rainfed rice farming systems. Because of the significant contributions of poor women in farming, their roles and needs should be considered in technology development and dissemination. Efforts are now being made to provide women farmers with access to new information and new seeds by involving them in the early evaluation of rice genotypes through participatory rice varietal selection in drought and submergence rice environments in eastern India. Agrohydrologic and drought risk analyses of rainfed cultivation in northwest Bangladesh Abul Fazal M. Saleh, M.A. Mazid, and S.I. Bhuiyan Drought is a common problem in the northwest region of Bangladesh, where the monsoon season (June-October) receives only about 1,000 mm of rainfall. For drought characterization, long-term (1961-93) weather data were analyzed and the impact of drought on rice establishment and farmers' management practices was studied for two wet seasons (1994-95). The probabilities of two and three consecutive 5-d droughts occurring during the grain-filling period of transplanted rice (TPR) are 73% and 53%, respectively. In an average year, rainfall may be adequate for transplanting by mid-July. But, twice in ten years, the required rainfall may not be available by 15 August and transplanting may be delayed. The average seasonal relative water supply (RWS) from rainfall is 0.79. Because of late transplanting, the RWS is expected to be only about 0.51, twice in ten years, and can be very detrimental to crop yield. Dry-seeded rice (DSR) may be established early, by the first week of June in an average year, and, twice in ten years, by the third week of June. DSR yields are similar to those of TPR, but DSR matured 1-2 wk earlier than TPR and left a better soil-water regime for the subsequent nonrice crop. A.S.R.A.S. Sastri and V.P. Singh Climate is an important component of environment. In environmental characterization for developing strategies to improve productivity, an agroclimatic inventory is a prerequisite. In eastern India, comprising the states of Orissa, Bihar, West Bengal, eastern Madhya Pradesh, eastern Uttar Pradesh, and the northeastern states, rice is grown mostly under rainfed conditions in upland, lowland, and flood-prone ecosystems. As this region comes under the influence of the southwest monsoon from June to October, crop productivity depends entirely upon the vagaries of monsoon. Also, because of monsoon activity, the sky is mostly overcast and radiation becomes a limiting factor. In this study, the moisture regime was analyzed using simple measures such as amount of rainfall and number of rainy days and derived parameters such as moisture availability and stable rainfall periods at different probability levels. We found that the average rainfall in eastern India matches mostly with 30% or, in some cases, 40% probability levels, indicating that any average rainfall-based strategy for improving rice productivity is successful only once in three years. Therefore, a concept of stable rainfall period has been developed by defining it as a period when weekly rainfall exceeds 50 mm. Stable rainfall periods even at a 60% probability level are very short in some parts of the region, suggesting a need to develop viable location-specific water management practices. The thermal regime in this region is not generally a limiting factor, except on a few occasions. Because radiation is a limiting factor during the active monsoon months, however, we need to identify rice varieties with higher energy-use efficiency. Rainfed rice, risk, and technology adoption: micro-economic evidence from eastern India H.N. Singh, S. Pandey, and R.A. Villano Risk and risk aversion are often believed to be important factors that constrain the adoption of technology by poor farmers. The nature and magnitude of risk and how farmers manage risk, however, have been poorly studied in the context of rainfed rice. This chapter provides an analysis of variability in rice production and farmers' coping strategies using farm-level panel data from two villages of eastern Uttar Pradesh, India. The results indicate that crop diversification is an important farmer strategy for dealing with risk. Through crop and income diversification, farmers have been able to reduce the effect of risk in rice production on the variability of total household income. The economic cost of risk in rice production was found to be quite low, implying that yield-increasing rather than yield-stabilizing rice technologies are likely to be more appropriate in these environments. The adoption of modern varieties was conditional on irrigation, farmers' education, farmers' age, and their wealth status as represented by farm size. Implications of these results for technology design and policy reforms are discussed. Monitoring rainfed and irrigated rice in Southeast Asia using radar remote sensing Rob Verhoeven, Hans van Leeuwen, and Eric van Valkengoed Rice is the main food crop in the Asia-Pacific region and reliable spatial information such as area, yield, crop type, and secondary crops is therefore essential for management of the rice-growing areas and food policy. Space-borne remote sensing provides a synoptic view over extensive areas on a regular basis and has proven to be useful as an independent data source for agricultural statistics. Radar remote sensing can be useful for mapping and monitoring cloud-covered areas and can be used to identify and monitor rice fields. This is demonstrated on the basis of some current and past projects on rice in Southeast Asia. Using an integrated spatial approach, combining information from remote sensing and other spatial data sources in a geographic information system, rice crops can be identified in both the dry and wet season and useful information such as area, number of harvests, and eventually yield can be estimated. |
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Planning and managing rice farming through environmental analysis Regional land-use analysis to support agricultural and environmental policy formulation Characterizing rice pests in the rice-wheat system of India Constraints to the adoption of modern varieties of rice in Bihar, eastern India Economics of intensive rainfed lowland rice-based cropping systems in northwest Luzon, Philippines Characterizing environments for sustainable rice production Characterizing rainfed rice environments: an overview of the biophysical aspects Weed communities of gogorancah rice and reflections on management Agrohydrologic and drought risk analyses of rainfed cultivation in northwest Bangladesh Rainfed rice, risk, and technology adoption: micro-economic evidence from eastern India Monitoring rainfed and irrigated rice in Southeast Asia using radar remote sensing |
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