ARID AGRICULTURE. 



57 



as soon after every heavy rain or snow as it is 

 dry enough. Do not wait too long, for when too 

 dry the soil will dust and drift. Light rains 

 may cause actual loss of soil moisture by form- 

 ing a connection which lilts the water to the sur- 

 face, where it is lost into the air. Judgment 

 should be used and the ground cultivated as 

 earlv and often as the conditions indicate. 



HUMUS AND 



VEGETABLE 

 MOLD 



PACKING 

 THE SOU, 



There is much misconception about what 

 humus is. Often when we speak of humus, we 

 do not mean true humus, but refer to the par- 

 tially decayed plant substances, which were bet- 

 ter called vegetable mold. True humus is the 

 final product of the decay of organic matter in 

 the soil. It is a very complex chemical com- 

 pound, which contains nitrogen, and may act in 

 an important way toward the change and use of 

 soil plant foods. On the other hand, it is the 

 partially decayed vegetable matter which has so 

 much to do with tilth. This substance absorbs 

 water, holds the soil particles apart, aerates the 

 soil, and fosters bacterial and chemical changes 

 which are of most value to living plants. This 

 decaying condition must be kept up by continual 

 renewal of organic matter. 



There are three or more conditions of soil 

 which call for the use of some form of packer. 

 Soils that are covered with so much grass that 

 they do not naturally fall close enough to shut 



