SHALLOW AND DEEP CULTIVATION 69 



washing of the soil. By filling up the little gulleys and the 

 ditches, which are washed out during a rain, they are pre- 

 vented from increasing in size, and thus washing to an 

 appreciable extent is avoided. (8) Cultivation increases 

 the depth of the seed bed. (9) Cultivation offers a means of 

 adding green manures and humus to the soil. (10) Cul- 

 tivation liberates plant food. This is an excellent means of 

 freeing plant food, because the stirring of the soil particles, 

 brings together the different elements. Chemical action is 

 thus increased and the plant food is liberated, which was 

 previously held in combination, with the other elements that 

 were not available to the plant. 



Shallow and Deep Cultivation. — The depth to which a soil 

 can be plowed in order to give the best results must neces- 

 sarily vary with the condition and the type of soil. On a 

 clay soil or any soil of a heavy type, deep plowing, as a 

 rule, should be recommended, while on the sandy or sandy 

 loam types of soil, deep plowing is not usually advisable, 

 especially if the soil is plowed in the spring. It is con- 

 ceded that the longer a soil is cultivated, the deeper and 

 the more thoroughly it should be pulverized. The depth of 

 plowing is also regulated by the season, the location and 

 the time of plowing. Land that has been cropped for a 

 series of years should be plowed deeper than new land, but 

 this varies somewhat, according to the section of the coun- 

 try. It has also been found that deep plowing will give 

 better results if it is done in the fall. The depth of plowing 

 should fluctuate, with different years, one year a little shal- 

 low, and the next year a little deeper, and so on. If one 

 depth is maintained continuously the pressure of the imple- 

 ments in time produces a hard bottom to the furrow, which 

 greatly interferes with plant growth. In regions of light 

 rainfall, deep plowing should only be done at intervals of 

 from four to five years. However, when the rainfall is 

 about the average for a good crop, deep plowing should 

 usually be the rule on heavy soils. 



Shallow cultivation should be given, as the crops advance, 

 and a mulch of fine earth should be kept on the soil. Where 

 frequent cultivation is followed, the capillary tubes near the 



