POTASH IN MASSACHUSETTS SOILS 13 



A majority of the samples have higher potash in the silt-clay particles. How 

 ever, the averages for the ten surface soils show potash practically equal for the 

 two groups of soil grains. Since sands constitute approximately 75 percent of 

 the soils, however, it follows that the bulk of soil-potash is contained in them; 

 and, as Failyer has remarked, it is a large reserve to be gradually weathered into 

 availability for plants. 



Soil Potash Soluble in Water 



Potash in commercial fertilizers is required by law to be soluble in water. 

 The amount of water-soluble potash in soils has received comparatively little 

 study. 



Morse and Curry found that, in the soils around the New Hampshire Agricul- 

 tural Experiment Station, water-soluble potassium ranged from 6 to 18 parts 

 per million parts of soil in upland soils, and from 6 to 35 parts in lowland soils. 

 Fraps has reported water-soluble potassium in over 200 Texas soils, of which more 

 than half contained between 6 and 36 parts per million parts of soil. The re- 

 mainder of the soils extended the range as high as 16S parts. Shedd in Soil Science 

 has described eleven Kentucky soils of silty and silty loam types. In eight of them, 

 water-soluble potassium ranged between 14 and 30 parts per million parts of soil; 

 one sample contained 97 parts. King, in Bulletin 26 of the Bureau of Soils, U. S. 

 Department of Agriculture, has reported an exhaustive study of eight distinct 

 soils in as many different parts of the nation. The water-soluble potassium nat- 

 urally present in them ranged from 9 to 25 parts per million parts of soil. 



From these different reports it may be calculated that in many soils there 

 may be between 10 and 65 pounds of actual potash per acre in the surface 6 inches 

 that is immediately soluble in water. Furthermore, there is evidence that as 

 plants absorb the soluble potash, more of it passes into the soil solution from the 

 soil grains. 



King treated his soils eleven successive times with water, with a thorough 

 drying of the sample between the treatments, and succeeded in recovering from 

 128 to 273 parts of potassium per million parts of the soils. Fraps conducted pot 

 experiments with all of his soils in which he grew two successive crops without 

 adding fertilizer. The crops were analyzed. The first crop contained more than 

 three times as much potassium as was found in the water solution. Both crops 

 together contained about six times the amount. 



At this experiment station, in the different fertilizer experiments, plots without 

 potash have borne crops that contained from 20 to 90 pounds of potash per acre. 

 If these quantities were distributed in the surface 6 inches, there would be approx- 

 imately 13 to 60 parts of potash per million parts of soil, which dissolved in the 

 soil solution before being absorbed by the plants. 



Morse and Curry reported sixteen soils in which water-soluble potassium was 

 determined. The grass crops growing on these soils were also analyzed for potash. 

 The soils were divided into two groups of eight soils each. 



Water-soluble 



Potassium in Soils Potash in Crops 

 Percent Percent 



Group A 6.0 to 13.8 .79 to 1 .46 



Group B 15.8 to 35.1 .84 to 1.65 



The crops from the soils with the higher water-soluble potassium had absorbed 

 the larger percentages of potash. 



