MANURE, YIELD AND SOLUBLE SALTS IN SOILS. 



Changes in amounts of water-soluble phosphates, expressed 

 HPO 4 , after fifty days. 



47 



as 



Associated with the increased amounts of nitrates and sul- 

 phates and of other water-soluble salts, and with the changed 

 physical and other conditions which favor the increased rates 

 of nitrification, there were other changes occurring which 

 placed the phosphates in conditions preventing their recovery 

 from the soils by single three-minute washings in distilled water 

 in as large amounts as were recovered from the same soils imme- 

 diately prior to their being placed in the nitrification experi- 

 ment. The soils were under quite different physical conditions, 

 so far as soil moisture and soil air were concerned, but how far 

 these may have determined the changes referred to cannot yet 

 be stated; but what seem to be comparatively slight physical 

 differences are undoubtedly responsible directly or! indirectly 

 for very different results in the amounts of some of the water- 

 soluble salts recoverable from different soils. The truth of this 

 statement will be clear from a comparison of the amounts of 



