Irrigation systems Agricultural meteorology 6 Crop production 6 Soil Temparature 6 Soil formation 6 Soil moisture 6 Soil organism 6 Tillage 6 soil acidity 6 soil alkality 6 soil clssification 6 soil erosion 6 soil salirity 6 Irrigation 4 Soil Water Management (Irrigation and Drainage), (Revised June 2002) 4 Water management 4 Drainage 2 Natural Resource Economics, (New March 2000) 2 Planning 2 Policy and Planning 2 Water Resources 2 Water policy 2 Agencies and Organizations 1 Agricultural Economics 1 Agricultural and Forestry Equipment (General) 1 Arid regions 1 Automation 1 Automation and Control 1 Canals 1 Community Participation and Development, (New March 2000) 1