This study analyzes the effects of aggregation and yield classification for corn, soybean, and wheat yields so that resulting management maps, based on crop yields, reflect the spatial heterogeneity within fields at a scale that may be appropriate for crop management. The spatially explicit yield values obtained from yield monitor data were ag gregated into various resolution scales, and standard deviations within each cell and within each resolution were determined. The results indicated that aggregation had minimal effects on summarizing land areas, drastically reduced the number of data values, and did not compromise the information contained in the original data. Differences between original and aggregated crop yields were generally less than 0.2t/ha and the standard deviations within cell resolutions rarely exceeded 0.7 t/ha. Based on crop yields alone, 0.4 hectare grids with yield classifications of 8-10% of the average yield for each crop were found to be appropriate for the creation of unique management areas in the three fields studied.

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The study presented here deals with the basic mechanical properties such as Young's modulus and bearing capacity of thin cement composite elements reinforced with welded square geogrid mesh and hexagonal (chicken) mesh subjected to direct flexure. The major parameters investigated in the study are the number and type of mesh layers in terms of effective reinforcement as well as volume fraction of reinforcement and thickness of the cement composite elements. Sixteen elements were cast and tested after 28 days of curing. By analyzing experimental data, equations for estimation of Young's modulus, first crack stress, first crack moment and ultimate moment of the composite have been developed for practical design. Test results show that the Young's modulus and the bearing capacity at first crack and ultimate of cement composite elements are greater for chicken mesh than for the geogrid mesh.

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Conservation of water quality and quantity is needed in Cidanau Watershed, West Java of Indonesia, for the sake of agricultural and industrial development. It is necessary to understand the mechanism of land use change, in order to propose proper plans for land use management and to decrease soil erosion from the watershed. This paper first aims to find some causes and a mechanism of environmental degradation induced by land use change, using some census data at the desa (village) level and intensive field investigations and interviews. Investigation of data was mainly focused on the period of economic crisis in 1997-1998. After discussing the effects of the economic crisis in Southeast Asia from 1997 to 1998 on the socio-economic status and the natural environment in this area, this paper discusses some important aspects of effective environmental policies, including economical land use management countermeasures in this watershed.

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The Chao Phraya Delta of Thailand has both problems of water shortage and flooding. There are many gaps between the ideal concept and the present methodology of water management. It is essential to achieve a stable and fair water supply for cultivation in the dry season. Available water resources for cultivation should be maintained and developed by saving water. The authors propose improving methods of water allocation planning and practical water operation, and also comment on flood control. The proposals are limited to measures that can implement within the authority of the Royal Irrigation Department (AID). The proposals refer to upstream dam operation, effective use of side flow, release from the diversion dams, water allocation for cultivation, frequent regulation of main intake regulator, effective use of rainfall in the field, and so on. Their aim is to provide useful ideas for water management based on present experience. The proposals are worthy of being implemented now, basically because they do not need much special budget allocation, they do not have any negative impact in particular, and they will contribute to carrying out water management with greater accountability. The Modernization of Water Management System Project started the development of a decision support system for practical water management to realize some of the proposals.

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The Mwea Irrigation Scheme (MIS) is a paddy irrigation project servicing an area of 5, 890 ha in central Kenya; the scheme was developed from 1954 to 1973. Until 1993, recurrent and sometimes serious shortages of irrigation water occurred in the lower reaches of the MIS. In 1991, a technical cooperation project with the Japan International Cooperation Agency was started in the MIS. One of the activities of the project was the improvement of irrigation water distribution. This paper describes the changes and improvement in water distribution in the MIS from 1994 to 1998. The organisation of water distribution was restructured and a water distribution plan was drawn up based on 9 selected flow-measuring structures named Check Point Nos. 1-9. Water resource shortages, mainly due to droughts, were experienced in 3 of the 5 years that this new plan was implemented. During the implementation period, farmers upstream of the scheme area started using irrigation water for horticultural crop cultivation, especially during the dry season, thus placing further pressure on the limited water resources.

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The rationale for Participatory Irrigation Management (PIM) in Zambia is derived from operation and maintenance, market and government inadequacies in managing irrigation projects on the one hand, and, on the other, from the inadequate capacity for the government to subsidize initially heavily subsidized irrigation projects as well as the need for user management. This paper looks at smallholder irrigation projects and attributes their poor performance and outright failure, in certain cases, to lack of involvement and mutuality of understanding of needs, roles, and social-economic factors among stakeholders in the cycle and process of development. The role and impact of PIM in irrigation development projects is ascertained through contrastive assessment of irrigation economic efficiency and performance of the projects. Economic efficiency of projects is based on the projects' economic viability, evaluated using economic indices based on the Economic Internal Rate of Return (EIRR) and Net Present Value (NPV). Project performance is evaluated on the basis of irrigation water utilization based on the difference between total irrigation water supplied and actual water beneficiaries used for irrigation.
This study concludes that PIM enhances overall performance of irrigation projects against low EIRR and NPV that are indicative of projects' economic viability. Project efficiency and/or performance of economically viable irrigation projects are negatively affected by the absence of PIM. A procedural framework model for implementing PIM in smallholder irrigation projects is proposed, with the aim of ensuring self-sustainability and fostering “full cost recovery” by beneficiaries.

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