110 SOILS 



possible irrigation should be used to supplement dry 

 farming. 



TILLAGE TO PROMOTE FERTILITY 



The longer a soil lies idle, so far as the farmer is 

 concerned, but is covered with Nature's crops year 

 by year, the richer it becomes. The chief reason 

 for this is pointed out in Chapter XII. Nature's 

 crops die, decay and are returned to the soil, adding 

 to it what they have taken out and improving 

 its texture; the farmer's crops are mostly removed. 

 On the other hand, it is also true that tillage makes 

 the soil more fertile. It will do so as long as the 

 supply of humus that is in the soil when it is cleared 

 for cropping is maintained, and provided as much 

 plant food is added to the soil each year as is re- 

 moved in crops. But since neither of these con- 

 ditions are complied with, it usually happens that 

 the longer the soil is tilled the poorer it gets. The 

 falling off in its ability to produce crops would be 

 very much greater, however, were it not for the 

 food-producing power of tillage. 



How Tillage Increases Fertility The explana- 

 tion of the power of tillage to increase fertility 

 is very simple. In Chapter I it was statea 

 that the chief agency that has broken up the 

 rocks and made them into soil is weathering the 

 action of water, air, heat and cold. This action is 

 still going on; soils are being weathered, as well as 

 rocks and stones; their grains are becoming finer, 

 their plant food more available. Tillage makes 

 a soil more fertile chiefly because it loosens it, thus 

 allowing a free entrance to these agencies that 

 make it finer, and hence expose more surface for 

 the roots to feed upon. Every time that a soil 



