FERTILIZERS 55 



decay, (29) ; (c) Increasing the moisture holding 

 power and friability of the soil. (90.) 



2. To obtain the nitrogen which they gather 

 during their growth. (30). 



3. To set free unavailable plant foods by the 

 direct action of their roots. (Insoluble substances 

 are coroded, and dissolved and taken up into the 

 plant tissue and later become available as the plant 

 decays.) 



4. To prevent soil washing and leaching by win- 

 ter rains. 



83. The common vetch (Vicia Sativa) is at pres- 

 ent the most popular legume for the California orch- 

 ardist. Field peas, some clovers, and other varieties 

 of vetch are also used. Barley and other non legu- 

 minous plants have not the same nitrogen gather- 

 ing power but are beneficial as far as their roots set 

 free unavailable forms of potash and phosphoric 

 acid. 



The volunteer non-leguminous plants and weeds 

 such as alfilerea mallow, foxtail and others, are per- 

 haps as beneficial as legumes plants for their humus 

 value and root petetration and while it is not cer- 

 tainty known just now how much nitrogen may be 

 added by various legumes it is probably safe to 

 assume that they add some and for this reason are 

 preferred to the non-leguminous plants. 



COVER CROPS AND WATER. 



84. It is well known that the winter cover crops 

 use up a good portion of the rain that falls so that 

 comparatively the clean culture orchards begin the 

 dry season with more moisture in the ground. While 

 this loss is usually more than compensated for by 



