POTASH IN MASSACHUSETTS SOILS 15 



The investigations by Briggs and Shantz showed that clover transpired about 

 twice as much water as corn in proportion to its weight, which would make it 

 possible to get more potash into its tissues. Grasses were between corn and clover 

 in the amount of water transpired. 



Economical Use of Potash Fertilizers 



The field and laboratory data often show that more potash is applied in fertiliz- 

 ers than the crops will take up. 



Two soil tanks at the New York State Agricultural Experiment Station received, 

 over a period of sixteen years, muriate of potash that was equivalent to 1184 

 pounds of potassium per acre. The crops took up the equivalent of 894.9 pounds 

 of potassium and the drainage water carried away 77.5 pounds of potassium per 

 acre. There remained in the soil 212 pounds of potassium, which was more than 

 17 percent of the amount applied. 



Fixation of potassium in the soil by transformation of soluble potash salts into 

 less soluble soil compounds has been much studied by investigators of soils. The 

 opinion was general at the First International Congress of Soil Science that potas- 

 sium thus fixed in the soil was later available for crops. 



When soluble potash is abundant in the soil, crops may take up more than ap- 

 pears to be needed for growth. In our pot experiments it was found that soybeans 

 grown in soil with residual potash weighted 393 grams and contained 4.8 grams 

 of potash. On the same soil with a liberal addition of sulfate of potash, the pots 

 produced 390 grams of crop which contained 8.5 grams of potash. Similar results 

 were obtained with Japanese millet in other pots filled with the same soil. An 

 excessive supply of fertilizer potash is not economical when taken up by the crop. 

 The only short cycle of recovery of the potash in the crop, other than plowing 

 the crop under, is to feed the crop to animals and return the potash in farm manure. 

 Losses occur in such a cycle, some of which cannot be avoided. 



Lyon and Bizzell in Memoir 134 of the Cornell University Agricultural Experi- 

 ment Station described experiments with soil tanks in which, during fifteen years, 

 536 pounds of potash per acre had been applied in farm manure. During this 

 period the drainage water had carried away 975 pounds of potash per acre. The 

 decomposing manure apparently decomposed some of the mineral potash, as 

 Vandercavey has shown with decomposing straw in investigations reported by 

 him in Soil Science. 



The application in fertilizer of all the potash that a crop can take up may be 

 an extravagance. It is using the deposits of potash salts, which exist in limited 

 areas, for wide distribution with the possibility of their ultimate exhaustion. 

 The naturally available soil potash may require reenforcement, but its reasonable 

 use may be considered as income from a substantial principal. 



The fundamental differences between the soils which have appeared to need 

 potash and the soils which have not needed it are differences in soil texture and 

 in water supply. Light soils with their larger proportion of sand grains yield 

 their potash sparingly to the soil water, which is also scanty unless rains are 

 frequent. Heavy soils, with much more of clay and silt, hold more water in which 

 the potash dissolves more freely from the fine soil particles. 



Efficient use of fertilizer potash requires consideration of the soil texture and 

 the water supply. Abundance of water will enable a crop to make use of soil 

 potash. Scanty water supply should be supplemented with easily dissolved 

 potash fertilizers. 



