THE SOIL AND ITS IMPROVEMENT. 101 



the needs of the plants, but must not be "water-logged." Ex- 

 perience has shown that the condition of soil, with regard to 

 moisture, most favorable for plant- growth, js that in which the 

 particles of soil are moist, but the spaces between the particles 

 contain no water. 



4th". The soil must be in a state of minute division. The won- 

 derful fertility of the soil in many river bottom lands is largely 

 due to the fact that the particles of which they are composed are 

 exceedingly fine. When the soil is in lumps, or even in large, 

 coarse particles, the roots of plants can not draw from it the 

 nourishment they need, nor can the chemical changes, so essen- 

 tial for fertility, proceed with any degree of rapidity. 



5th. The soil must be in such condition that chemical action 

 can proceed rapidly, whereby the plant food it contains may be 

 rendered available. 



It will be seen by this that the requirements of a fertile soil 

 are many, and that an abundant supply of plant food is neces- 

 sary. This food, instead of being, as has often been supposed, 

 the one essential characteristic, is but one of several, all equally 

 needful. We will usually find all these essentials in a soil that 

 is composed of a due proportion of sand, clay, and humus ; that 

 is thoroughly drained, either naturally or artificially; that is 

 kept in fine condition by thorough cultivation, and that is sup- 

 plied with plant food by proper applications of manure. 



Improvement of Soils. There are three different meth- 

 ods by which soils may be improved, or by which the five essen- 

 tials of fertility can be secured. These are Drainage, Cultiva- 

 tion, Manure. 



Drainage. We place this first because when needed, the 

 improvement of the soil by the other two methods is impossible. 

 Cultivation and manure are alike wasted on a water-logged soil. 

 The practice of drainage is sufficiently explained in the chapter 

 on that subject, and we will need here only to give a brief ex- 

 planation of the scientific principles connected with it. 



One of the essentials of fertility we have seen is such a 

 condition of soil that chemical change can progress rapidly, 

 constantly converting plant food into available forms. This 



