XIX.--FARM MANURES 171 The functions of manures and fertilizers 171 Classification 171 Importance of farm manures 172 Barn or stable manure 173 Loss of value 173 Checking the losses 176 Applying the manure to the soil 177 Proper condition of manure when applied 179 Composts 181 XX.--FARM MANURES, CONCLUDED 183 Green-crop manures: Functions 183 Benefits 185 Character of best plants for green-crop manuring 185 The time for green-manure crops 186 Leguminous green-manure crops 186 Non-leguminous green-manure plants 191 XXI.--COMMERCIAL FERTILIZERS 192 The raw materials 192 Sources of nitrogen 193 Sources of phosphoric acid 195 Sources of potash 199 Sources of lime 200 XXII.--COMMERCIAL FERTILIZERS, CONTINUED 202 Mixed fertilizers: What they are Many brands Safeguard for the farmer Low grade materials Inflating the guarantee 202 Valuation 205 Low grade mixtures 207 Buy on the plant food basis 209 XXIII.--COMMERCIAL FERTILIZERS, CONCLUDED 211 Home mixing of fertilizers 211 Kind and amount to buy 212 The crop 213 The soil 215 The system of farming 215 Testing the soil 215