xiv CONTENTS 



XII. NiTKOGEN, Phosphobus Am> Potassium in Relation to Soil 



Fektility 187 



1, Fertilization and the Theory of Fertilizers. 2. Green 

 manuring: (a) Green manuring and its benefits. (5) Crops 

 for green manuring — ^legumes best, (c) Plowing under the 

 crop — ^when, how and for what crops, (d) Feeding vs. plow- 

 ing imder the crop, (e) Some hints on green manuring. 



3. Commercial Fertilizers: (a) Four classes of commercial 

 fertihzers. (6) Nitrogen fertilizers and their value. Legumes 

 to solve nitrogen problem, (c) Phosphate or phosphorus 

 fertihzers and their uses, (d) Potash or potassium fertil- 

 izers and their value, (e) Mixed fertilizers. (/) Concerning 

 commercial fertilizers in general, (g) Soils and crops deter- 

 mine kind to use. {h) Home mixing of fertihzers. (i) How 

 commercial fertilizers may be apphed. (j) Lasting effect of 

 fertihzers. 4. Manure as a Fertihzer: (a) Some facts about 

 manure: (1) FertiHzing value about $2.34 per ton. (2) 

 Manures differ in fertihzing value. (3) Feeding affects 

 value of manure. (4) Amount of manure produced by farm 

 animals. (5) Liquid portion of manure valuable, (b) Some 

 practical pointers on use and care of manure: (1) Manure 

 has three-fold value. (2) Manure a quick fertilizer. (3) 

 Stall manm-e better than open-yard manure. (4) Hints on 

 storing manure. (5) Light appHcations better than heavy 

 apphcations. (6) Plowing under vs. discing in manure. 

 (7) Applying manure to clover fields. (8) Manure not a 

 perfect fertihzer. 



Xm. Soil Acidity and Liming in Relation to Soil Fertility .... 229 

 1- Soil Acidity Explained. 2. Soil Acidity Lowers Soil 

 Fertihty (Productiveness). 3. The Meaning of Liming. 



4. How Liming Improves Acid Soils: (a) Available calcium 

 is added for clover and alfalfa, (b) Absence of acidity favors 

 the helpful soil organisms, (c) Plant-food elements are 

 rendered more available, (d) Greater returns are secured 

 from fertihzation. (e) Lime tends to improve tilth on 

 heavy soils, (f) Helps to control mahiutrition diseases of 

 truck crops, (g) Weeds may be better controlled. 5. Crops 

 Benefited by Lhning When Grown on Acid Soils. 6. Crops 

 Which Tolerate Acidity. 7. How Acid Soils May be Deter- 

 mined: (a) By the use of blue litmus paper; (6) by chemical 

 tests; (c) by alfaKa and clover failures; (d) by the growth of 

 certain plants. 8. 'Low Wet Lands not Necessarily Acid. 

 9. How Soils Become Acid — ^Extent of Acid Soils. 10. The 

 Nature of Soil Acidity. 11. Kinds of Agricultural Lime. 

 12. Comparative Value of Agricultural Limes — ^the Best to 

 Use. 13. Amount of Lime to Apply. 14. When, How and 

 How Often to Apply Lime. 15. Deep Plowing Cannot be 

 Substituted for Limuig. 16. Soils Derived from Lime- 

 stone May Become Acid. 17. Soil Fertihty is Regulated 

 Through Liming. 



XIV. Harmful Agents fN Soils Affecting Fertility , . 255 



1. Worms and Insects in Soils May Destroy Crops. 2. 

 Diseases in Soils May Cause Crop Failures. 3. Too Much 

 Water in Soils is Harmful. 4. Alkali Salts in Soils is 

 Injurious. 5. The Toxin Theory of Infertihty. 6. Other 

 Harmful Agents. 



