Nitrogen 5 Nitrogen-fixing plants Legumes 4 Nitrogen-fixing microorganisms 2 Plants 2 Symbiosis 2 Agroforestry 1 Agroforestry and Multipurpose Trees: Community, Farm and Social Forestry 1 Azolla 1 Biochemistry and Physiology of Microorganisms, (New March 2000) 1 Cover crops 1 Cropping systems 1 Crops 1 Effect of nitrogen on 1 Fabaceae 1 Ferns 1 Fertilizers and other Amendments 1 Field Crops, (New March 2000) 1 Fixation 1 Fodder legumes 1 Forage and Fodder Crops, (New March 2000) 1 Forests and Forest Trees (Biology and Ecology) 1 Green manures 1 Horticultural Crops, (New March 2000) 1 Innovation adoption 1 Multiple cropping 1 Nitrification 1 Nitrogen content 1 Nitrogen fixation 1 Nitrogen fixing bacteria 1