Chapter Twenty-One 

 SOIL IMPROVEMENT 



Good root growth is necessary for healthy plant growth. 

 It is easy to see how important the soil becomes in root de- 

 velopment, since the roots must obtain water and mineral 

 salts, and grow in the soil, pushing between the soil particles, 

 and finally, as they grow in diameter, pushing larger masses 

 of soil aside. The soil has been explained as a complex mass 

 in Chapter 7, and it is safe to say, that any kind of improve- 

 ment will be beneficial in more than one way. Most soils can 

 be improved at a small expense if the effort is continued over 

 a period of time. 



Soil with a good texture is of a loose, crumbly consistency, 

 which allows proper aeration for root growth and the in- 

 crease in the growth and the number of soil organisms. It 

 must be remembered that as the activity of the organisms 

 increases the humus is destroyed more rapidly. With its in- 

 creased growth, however, the root adds more humus as it 

 decays. Pavlychenko of the University of Saskatchewan, 

 found that single plants of grass had a root system with a 

 total length of 300 miles, but no root was more than 7 feet 

 long. A total length of 150 miles of root system grew each 

 season and about the same amount died each year, leaving 

 the soil porous and adding the decaying roots as humus. 

 The roots for this study were washed free from the soil with 

 extreme care. An example of this important work made a 

 most attractive educational exhibit at the Atlantic City 

 (1936) meeting of the American Association for the Ad- 

 vancement of Science. 



Plowing and cultivation keep the soil loose. Worms 

 greatly aid cultivation by making burrows through which 



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