CORN 



(i) A great deterioration in the physical condition of the soil, 



(2) A waste of the soil fertility, especially of the humus and 

 nitrogen. 



(3) An increase of the weed enemies and the insect pests that 

 attack the crop, and as a result of all these, decreased crop yields. 



HUMUS. The productive capacity of most of the land of the 

 corn belt is largely measured by its physical condition and its content 

 iif humus and nitrogen, ilumus as defined by Ho[)kins includes only 

 that i)art rif the organic matter that has passed the most active stage 

 of deciimpwsition and has completely lijst the physical structure 

 of the materials from which it is made. Deterioration in the physical 

 condition of a soil is accompanied In' soil \\-ashing and lessening oi its 

 water-holding capacit3^ 



MANURE SPREADER IN OPERATION ON PASTURE LAND WHICH IS TO BE PLANTED TO 



CORN THE NEXT TEAK. 



These results are lirought about by the rapid exhaustion of 

 the humus. The frequent cultivation which is given the corn crop 

 promotes the aeration of the soil and thus permits the organic matter 

 to be rapidly oxidized. The humus serves as a binding material to 

 hold the soil particles together. In fine grained soils, such as clays, 

 it gives a more loam}- texture, such as is seen in soils which are 

 in good condition. Such soils will not bake or become cloddy, or run 

 together when wet, and are not so subject to washing as soil contain- 



