Soil Fertility Soil fertility 12 Soil Chemistry and Mineralogy 9 Phosphorus 6 Nitrogen 5 Plant Nutrition 5 Plant nutrition 5 Pollution and Degradation 5 Soil Biology 5 Soil management 5 Soil organic matter 5 Sustainability 5 Cycling 4 Erosion: Soil and Water Conservation 4 Fertilizers and other Amendments 4 Field Crops, (New March 2000) 4 Irrigation 4 Nutrient availability 4 Nutrient uptake 4 Plant Cropping Systems 4 Plant Production 4 Soil Physics 4 Soil degradation 4 Soil types 4 Biomass 3 Chemical composition 3 Crop production 3 Erosion 3 Forage and Fodder Crops, (New March 2000) 3 Grasslands and Rangelands 3