viii CONTENTS 



XXV. SOIL ORGANISMS 315 



Macro-organisms Rodents Insects Worms Plants 

 Micro-organisms Injurious Organisms Beneficial Organ- 

 isms Distribution and Conditions for Their Activity 

 Distribution Conditions for Development Loss of Ni- 

 trates Leaching Denitnfication. 



XXVI. TILLAGE 325 



Objects of Tillage Pulverizing and Loosening the Soil 

 Turning Under Vegetable Matter Killing Weeds 

 Storing and Conserving Moisture Compacting the Soil 

 Planting the Seed Implements of Tillage Plows 

 Harrows Compacters Seeders Cultivators Plowing 

 Time of Plowing Depth of Plowing Dynamiting Effect 

 of Deep-rooting Crops 'Preparation of the Seed Bed 

 Wheat Corn Oats Cultivation Value of Mulch 

 Root Injury Level Cultivation. 



XXVII. SOIL EROSION 358 



Cause of Erosion Effect of Topography Texture and 

 Structure of the Soil Vegetative Covering Character of 

 the Rainfall -Results of Erosion Removal of Organic 

 Matter and Nitrogen Changes Physical Character of 

 Soil Changes of Color Kinds of Erosion Sheet Erosion 

 Methods of Prevention and Reclamation Application 

 of Limestone Protection by Crops Residues Increas- 

 ing the Organic Matter Deep Contour Plowing Contour 

 Seeding Terraces Reforesting Tiling Gullying 

 Methods of Prevention and Filling Straw-brush Dams 

 Vegetation Filling with Soil. 



XXVIII. ROTATION 376 



Advantages of Rotation Better Distribution of Work 

 Control of Insects and Plant Diseases Control of Weeds 

 Variation in Depth of Root Systems Maintenance of 

 Good Tilth Maintenance of Organic Matter Toxic 

 Substances Increased Yields Planning a Rotation 

 Places in Rotations for Crops Practical Rotations Corn 

 and Winter Wheat Belt Cotton Belt Hay and Pasture 

 Province Spring Wheat Region Great Plains Province. 



APPENDIX I. SOIL FERTILITY 389 



Permanent Agriculture Are Soils Inexhaustible? Plant 

 Food Elements Removal of Plant FoodCrop Require- 

 ments Supply of Plant Food in Soils Nitrogen 

 Phosphorus Potassium Other Elements. 



APPENDIX II 407 



Average Yield of Crops Per Acre by States in United States, 

 Ten-year Average, 1906-1915 Average Yield of Wheat 

 Per Acre for Ten Years, 1905-1914, United States and 

 European Countries. 



APPENDIX III > . . . 410 



Farm Land Value Per Acre Farm Property Value Corn 

 Acreage Corn Production Oats Production Spring 

 Wheat Acreage Winter Wheat Acreage Wheat Produc- 

 tion. 



