Dec, 1909.] POTASH IN CLAY LOAM SOILS. 49 



2.31, while the grasses from the same plats averaged 1.99. 

 Hence a ton of clover would take up about six pounds more pot- 

 ash than mixed grasses. 



Compared with timothy the difference is even greater, as that 

 crop averaged in 1908 1.64 per cent, potash in the unmanured 

 plats. 



Clover also, as is well known, returns more nitrogen to the soil, 

 since the results obtained in 1907 on the samples just mentioned 

 were 2.37 per cent, of nitrogen in the clover and only 1.09 per 

 cent, in the grasses. 



It is easily seen then that by growing a crop of clover and 

 returning it to the soil, either by plowing under or in the form 

 of stable-manure, its decay in the soil will increase the avail- 

 able potash and by the increase in available nitrogen, enable 

 new crops to use even more of the soluble native soil-potash. 



EFFECT OF LIME AND PLASTER. 



Lime and gypsum, or plaster, are often mentioned by agri- 

 cultural writers as beneficial to soils by reason of their action 

 on the potash minerals in the soil. Numerous experiments were 

 tried, both in field and laboratory, to determine just what their 

 effect might be. 



In order to test this in the laboratory a number of soils were 

 treated with lime and stirred with water. After about two 

 months these water solutions were analyzed for potassium. It 

 was found that the solutions from the unlimed samples carried 

 just as much potassium as the solutions from the limed samples. 

 Samples of soil taken from limed and unlimed portions of plats 

 gave no different results with respect to soluble potassium. Many 

 samples of limed soil gave slightly less soluble potassium than 

 samples of similar unlimed soil. Since no effect was produced 

 by liming the soils it seemed well to try the effect of lime and 

 gypsum on the solubility of the potassium in feldspar. Feldspar, 

 as has been stated, is the natural mineral source of potassium 

 and is also free from clay and other disturbing factors. The 

 high potassium content of the feldspar permits of more pro- 

 nounced and more rapid results. 



In this series of experiments equal quantities of feldspar were 

 treated with lime and gypsum and stirred with water for ten 



