250 SOILS AND FERTILIZERS 



well prepared, the soil warms up more readily. The 

 loosening and pulverizing of the land enables the heat 

 from the sun's rays to more readily penetrate the soil 

 and bring the land into good condition for promoting 

 growth. 



334. Aeration of Seed Bed Necessary. Air is 

 required for functional purposes by the roots of crops. 

 In sand and loam the air spaces make up a half or more 

 of the total volume. With such soils it is not neces- 

 sary to cultivate with the view of increasing the air 

 spaces, but in compact soils, as heavy clays, plowing 

 should result in aeration of the soil and an increase in 

 the number of air spaces, as the air of the soil takes an 

 important part in rendering plant food available. (See 

 Section 53). If soils are plowed when too wet they 

 are not sufficiently aerated. The amount and kind of 

 cultivation to secure the ventilation and aeration neces- 

 sary for crop production must be regulated according 

 to the character of the soil as sand, clay or loam, and the 

 climatic conditions. The cultivation which is given 

 soils for purposes of conservation of the moisture also 

 secures the proper aeration. 



335. Preparation of Seed Bed Without Plowing. 

 - Loam soils which have been subjected to a sys- 

 tematic rotation of crops and upon which corn has been 

 grown, need not be plowed but the seed bed for the 

 succeeding grain crop can be prepared simply by disk- 

 ing. Surface tillage of the corn crop has sufficiently 

 loosened and aerated the soil and has caused an accu- 

 mulation of available plant food near the surface which 



