ROTATION IN DRY AREAS 385 



The humus thus introduced prevents heavy clays 

 with their fine soil components from adhering too closely, 

 consequently they are much more easily tilled. They 

 are more completely aerated, and because of their more 

 friable condition the roots of plants can penetrate them 

 more readily. Plants that furnish humus tend to bind 

 together the particles in soils so light as to drift, by the 

 many rootlets that they furnish. In this way they aid 

 in preventing soil lifting. Humus furnishes food in 

 some instances at least in a readily available form, as 

 when the vegetable matter that furnishes it is in process 

 of decay. But one of the most important, if not the most 

 important benefits resulting from it is the influence 

 which it exerts on moisture in the soil. It tends to 

 absorb and hold moisture, whether in its upward or 

 downward movement, to the great advantage of the 

 crops that are growing. 



Where rotation is not practised, the labor called 

 for is too much congested at certain seasons, and at 

 other seasons it is too little congested. The preparation 

 of the land for sowing, to be in season, must be done 

 within a limited time. The same is true of the seeding 

 and harvesting of the crop, subsequently. Because of 

 this the outlay for labor is larger than would otherwise 

 be necessary in order to get the work done. The diffi- 

 culty of getting the work done properly and in season 

 would also be greatly increased. In proportion as it is 

 done not in good form and out of season, the hazard 

 of low yields would be present. Farming is usually safe 

 and profitable in proportion as the farmer is able to do 

 his own work within his own household, or at least when 

 the necessity for hiring much labor is not present. 



Negative reasons for rotation in humid areas. Rota- 

 tion is called for in humid areas: (1) to prevent the 

 undue accumulation of weeds ; (2) to prevent the undue 

 increase of insect pests ; (3) to prevent an increase of 



