Soils and Fertilizers for Pecans 85 



of its nourishment from great depths, the subsoil affords 

 unusual conditions for root spread and nourishment. 



Careful analyses have shown that most agricultural soils 

 contain, within the first two feet of the surface, enough phos- 

 phoric acid and potash to meet the fullest demands of a 

 pecan orchard for more than two generations of men. The 

 importance of making available more of these vast stores 

 should certainly not be overlooked. 



Aside from bringing certain mineral elements up from the 

 greater depths of the soil and rendering them more readily 

 available to the growing plant, cover-crops, when turned 

 under and incorporated with the soil, greatly increase its 

 moisture-holding capacity, which in many respects is more 

 important and more beneficial to pecan trees than are large 

 quantities of mineral fertilizers added without this organic 

 material. Moreover, the solubility of calcium, magnesium, 

 iron, and phosphoric acid is measurably increased by the addi- 

 tion of liberal cover-crop materials to the soil. This is caused 

 in part by the action of the inorganic salts on the organic 

 substances or their extracts, and in part by the solvent action 

 of the soluble organic compounds formed during organic de- 

 composition. Such action of organic material incorporated 

 with the soil has a decidedly beneficial effect towards over- 

 coming rosette in pecan trees as w^ell as in promoting a more 

 vigorous growth. 



While the phosphoric acid and potash in the soil are fixed 

 quantities, except when foreign materials such as commercial 

 fertilizers are added, the quantities of nitrogen available vary 

 with the ability of the leguminous cover-crop to extract it 

 from the air in the soil. The gain in nitrogen is brought 

 about by nitrogen-gathering bacteria (micro-organisms) which 



