42 PRODUCTIVE FARMING 



15. Describe tip-layering of black raspberries. 



16. Describe vine-layering for grapes. 



17. What is mound-layering? 



18. Describe the cutting, storing, and planting of grape or currant 

 cuttings. 



19. What plants may be propagated by soft-wood cuttings? 



References.— U. S. Farmers' Bulletins: 113, The Apple and How to 

 Grow it; 157, The Propagation of Plants; 408, School Exercises in 

 Plant Production ; 423, Forest Nurseries for Schools. 



CHAPTER IV. 

 HOW SOILS ARE FORMED. 



The soil is one of those common things most of us think 

 very little about. We see it every day, we walk on it, we 

 eat and wear its products, but we very seldom give it a 

 thought. It may even surprise some of us to know that we 

 get from the soil not only our food, our houses and our cloth- 

 ing, but that all animal life comes indirectly from the soil. 

 For every living thing comes originally from two primary 

 sources, the air and the soil. All elements or substances 

 found in plants or animals are from either the soil or the air. 



The foods which plants secure from the air are too abun- 

 dant to ever become exhausted by large farm crops. No 

 human efforts are required to make them available to plants, 

 except for the securing of nitrogen from air, when ingculation 

 with certain bacteria may be necessary. The foods taken 

 from the soil on the other hand are much less available, and 

 the ability of plants to secure them may depend very largely 

 on the efforts of the farmer. It is necessary for the farmer 

 first of all to study his soil to see how he can make its plant- 

 food most available. 



What Soil is. — That part of the earth's surface which 

 can be tilled, and in which plants grow, is called soil. It is 

 the loose, highly decomposed layer of mineral matter result- 



