Soil Physics Nitrogen 4 Soil Chemistry and Mineralogy 4 Soil Fertility 4 Biomass 3 Grasslands and Rangelands 3 Phosphorus 3 Plant Nutrition 3 Plant Production 3 Plant nutrition 3 Soil Biology 3 Soil management 3 Agricultural soils 2 Agriculture 2 Analytical chemistry 2 Atmosphere 2 Chemical composition 2 Crop production 2 Crop yield 2 Erosion 2 Erosion: Soil and Water Conservation 2 Fertilizers and other Amendments 2 Forage and Fodder Crops, (New March 2000) 2 Grasslands 2 Irrigation 2 Leaching 2 Meteorology and Climate 2 Natural Resource Economics, (New March 2000) 2 Nitrogen fertilizers 2 Nutrient availability 2