48 



TEXAS AGRICULTURAL EXPEKIMENT STATION. 



There is little relation between these figures, except that, in a gen- 

 eral way, with the exception of the Houston black clay, a higher per- 

 centage of active potash is accompanied by a higher percolation of 

 potash. The percolation of potash depends, however, not only on the 

 solubility of the soil potash but also on the fixing power of the soil, 

 and, as we have seen, the fixing powers of these soils are such as to 

 reduce to a minimum the loss of fertilizer potash by percolation, except 

 with the Norfolk sand. It is of some interest to note, however, the 

 quantities of potash which percolated from the uncultivated soil. It is 

 evident that losses of soil potash take place during the winter and spring 

 months, when there are often heavy rains, and the soils are not covered 

 with crops. 



PHOSPHORIC ACID. 



The quantity of phosphoric acid in some of the percolates is given 

 in Table No. 22, but the quantities are very small. The maximum 

 quantjt}' lost in 1913 is 11.5 milligrams, or about 1.5 pounds per acre. 

 The average quantity lost is 4.1 mg. per pot or 0.5 pounds per acre. 

 These figures serve to show the small losses of phosphoric acid from 

 these unfertilized soils. 



LIME. 



As was to be expected, large losses of lime occurred. Table Xo. 23 

 shows the lime and magnesia in parts per million, and Table Xo. 24 

 in milligrams per pot. With one exception, the addition of potash in- 

 creased the loss of lime, although the increase is slight with several of 

 the soils. 



TABLE NO. 22. 

 Phosphoric Acid in Percolates. 



Table Xo. 21 shows the -loss of lime and magnesia in pounds per 

 acre. The loss of lime varies from 70 to 582 pounds per acre per year, 

 on the average of three years. The loss of lime and magnesia is, in a 

 general way, related to the lime soluble in strong hydrochloric acid. 

 This is brought out in the table below. 



