FERTILIZERS 59 



other salts before water can carry their elements to 

 the roots of plants. (29). 



The decomposed matter (humus) is attacked by 

 nitrifying bacteria and these require oxygen for 

 their work. Cultivation increases this supply of 

 oxygen so that nitrification proceeds faster, and 

 better growth results. The more frequent and deep 

 the cultivation, the better the nitrifying bacteria can 

 work. The size of fruit can be increased in this way, 

 or a short season made equal to a long one. 



Cultivation therefore uses up humus very rapidly 

 so that the supply must be frequently renewed. The 

 extra growth and yield are probably proportional 

 to the supply of humus and frequency of cultivation. 



92. This principle of aiding nitrification applies 

 to all forms of animal and vegetable fertilizers such 

 as yard manure, blood, raw bone, guano, tankage, 

 and peas and clover, planted for their fertilizing 

 value when ploughed under. 



Frequent, deep cultivation increases the supply 

 of water in soils. Several well-known acids, result- 

 ing from decomposition, unite with soil moisture 

 and dissolve what ordinary water will not. Insol- 

 uble forms of fertilizers, such as phosphate of lime 

 and silicate of potash, are probably thus made 

 available to the plant. 



93. Moist soils swell and are more permeable. 

 Roots can develop faster in them, and the fertilizers, 

 applied to the top, six inches, as they gradually dis- 

 solve, can be carried more easily and deeply, increas- 

 ing the feeding area of the roots and the develop- 

 ment of the plant. 



Frequent and through cultivation, helps and 

 multiplies these beneficial effects of soil moisture. 



