SOIL MOISTURE AND PREPARATIOM OF SOIL. 63 



(c) If a farm contain certain areas of each of these 

 kinds of soil, what use can the farmer make of this sug- 

 gestion of Nature ? Are any of tlie same kinds of plants 

 found upon all of these soils? If so, compare their con- 

 ditions. 



(d) Can you give reasons for these conditions? In 

 which soils can the air enter freely? Which with more 

 difficulty? Which gives the best support in time of 

 storms? Will each soil require the same treatment? 



Experiments 9 and 10 show how essential soil 

 moisture is to plants. Water and air not only 

 furnish 95 per cent, of the food of plants, but 

 the remaining 5 per cent, cannot be obtained 

 from the soil except through the agency of air 

 and water. Heat and light are also important 

 factors in plant growth. It has been shown that 

 soils vary in the power to admit air, and in the 

 power to absorb and retain heat, and that the 

 condition with regard to soil moisture affects 

 these variations. The farmer can, by proper 

 methods of drainage and tillage, greatly modify 

 or regulate Xki^s^ factors of plant grozuth — water, 

 air, and heat — in the soil. It is evident that dif- 

 ferent soils require different methods, and that 

 the same soil requires different treatment for 

 different plants. Tillage does not add plant- 

 food to the soil, but it does render food already 

 in the soil available to the plant. 



^.—PREPARATION OF THE SOIL. 

 The first thin^' for a farmer to do, and then to 

 continue doing, is to study Ids soils, taking into 



