CHAPTER XV 

 TILLAGE AND IRRIGATION 



THE yield and quality of a vegetable crop depends much 

 upon tillage. The objects of tillage are as follows : (i) 

 to improve the physical condition of the soil ; (2) to pre- 

 serve and control the soil moisture ; (3) to modify soil 

 temperature ; (4) to destroy weeds and to cover humus- 

 producing materials, as manure or cover crops ; (5) to 

 aerate the soil and thus hasten its chemical action and 

 make plant food soluble. 



Plowing. In the Middle West, fall plowing is preferred. 

 The broken furrows collect water, hence a maximum supply 

 of soil moisture is assured, and on sod land, the sod has 

 time to decompose. Fall plowing destroys many insects 

 and thus reduces their injury to the crops. Fall-plowed 

 land may be harrowed and planted earlier in the spring. 



The proper depth of plowing depends upon the crop to 

 be planted as well as upon the natural depth of the top 

 soil. Deep plowing is usually best for vegetable crops al- 

 though the turning up of subsoil is always detrimental to 

 these crops. 



Harrowing. Fall-plowed land should be harrowed as 

 soon as the ground is fit to work in the spring. If plowed 

 in the spring, the ground should be harrowed immediately 

 after plowing. 



The function of harrowing is to pulverize the soil and 

 smooth the land. Disk and cutaway harrows are especially 



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