firm enough to afford proper support to the plant. It should be loose 

 enough to permit water to percolate and admit without hindrance the 

 free growth of delicate root fibers. The soft points of roots will not 

 penetrate hard lumps, but will pass around and adhere to them in their 

 effort to secure food and water. 



We know that plant food in solution forms a film around each par- 

 ticle of soil, and that the very minute roots throw their tentacles around 

 it and secure nourishment by osmosis. Therefore, the advantage of a 

 thoroughly pulverized seed-bed is very apparent when we realize that 

 the available feeding area contained in a lump of soil is increased one 

 thousand-fold when it is broken up and all of the particles are separated. 

 While tillage does not increase the amount of plant food elements in the 

 soil, it does make available those which are there. We know that mil- 

 lions of acres, rich in plant food, are producing less than one-half of 

 their capacity, simply because the fertility is not available or within 

 reach of plant roots, and because stored water cannot move upwards on 

 account of obstructions which could be avoided. In the judgment of 

 the writer, a farmer takes out an insurance policy against crop failure 

 when he uses the disc harrow before and after plowing. 



DRAINAGE 



WE will not attempt to enter into a lengthy discussion of this sub- 

 ject, believing that every observing farmer is convinced of the bene- 

 fits to be gained by thoroughly draining his land. We will, however, 

 mention a few of the reasons why lands are made more productive and 

 the possibility of failures eliminated by thorough drainage. 



1. Farm crops are not aquatic; that is, the roots will not perform 

 their function of gathering plant food and water if they are submerged 

 in water. 



2. Plant roots and soil bacteria require free atmospheric oxygen. 

 If for any reason air does not circulate through the soil, the plant will 

 be smothered and bacteria will not transform elements into compounds. 



We have stated in a previous chapter that because of the irregular 

 shape and variety of sizes of soil particles, air spaces exist when any 

 number of particles are brought together. These air spaces constitute 

 from twenty-five to fifty per cent of the volume of soil. If air spaces 

 did not exist, the soil would be a solid stone. Again, many soil particles 

 are not solid, but perforated, thereby further increasing the volume of 

 air spaces. Air spaces between and through the particles of soil are : 



1. To permit a free circulation of atmospheric oxygen through the soil. 



2. To permit water to pass downward. 



3. To promote capillary attraction. 



