16 



USE OF FELDSPATHIC ROCKS AS FERTILIZERS, 



pure feldspathic i-ock, rich in potash, of which enormous quantities are to be 

 had in Norway. It was ground as finely as possible by Messrs. J. & J. Cunning- 

 ham, of Leith, and thereafter sifted through a sieve of 120 wires to the linear 

 inch, and was found to contain about 12 per cent of potash. The whole quantity 

 of sifted feldspar was very small, less than a half hundredweight, and as it was 

 received late in the season, the experiment was made simply to afford informa- 

 tion which might indicate whether it was desirable to try the experiment on a 

 larger scale the following season. There were two small experiments made — 

 one by Mr. R. Shirra Gibb. at Boon, on a crop of peas, and one at Pumpherston 

 on turnips. The experiments were on plots of one-fortieth acre, and the follow- 

 ing were the manures employed and the" results obtained: 



Kind and quantity of fertilizers. 



[Sulphate of potash, 3 pounds 

 1. -[Sulphate of lime, 3 pounds .. 



[Superphosphate, 6 pounds . . 



(Ground feldspar, 12 pounds . 

 2. -^Sulphate of lime, 3 pounds. . 



[Superphosphate, 6 pounds . . 

 „ (Sulphate of lime, 3 pounds.. 



iSuperphosphate, 6 pounds . . 



Peas. 



Dried in 

 bulk. 



Grain. 



Pounds. 

 114 



102 

 96 



Pounds. 

 3.8 



3.5 



Turnips. 



Bulbs. 



Pounds. 



482 



496 

 476 



Although the whole experiment is on a small scale, and the crops are below 

 the average, there is nevertheless a clear indication that the feldspar has acted 

 as a potash manure. In both cases where no potash was applied the crop is 

 the smallest. At Boon the plot with no potash was unable to mature its seed, so 

 that it could not be thrashed, while on the other two plots the amount of seed 

 was not very different, and (juite in proportion to the total crop, viz, about one- 

 fortieth. The smallness of the crop does not detract from the value of the 

 experiment as a means of indicating whether or not feldspar acts as a potash 

 manure. Had the crop been sown at the proper time it would have been much 

 larger. In the case of the turnip crop the ground feldspar has done better than 

 the sulphate of potash. That may be accidental, but it may be that the insoluble 

 form in which potash is contained in feldspar is more favorable for turnip 

 growing than the soluble sulphate. Soluble potash manures, when applied to the 

 turnip crop, sometimes diminish rather than increase the crop, and this is 

 especially the case where the crop is dunged in the drills ; but no dung has been 

 put on the Pumpherston station these twelve years, and the results obtained all 

 over the field show that potash is now required for turnip growing on that land. 



Upon the whole, the result of this experiment may be talcen as showing that 

 potash feldspar when ground to an exceedingly fine powder is capable of acting 

 as a potash manure even in a single season. 



In 1889 the Maine State experiment station," under Balentine, in- 

 dependently of any previous experimenters, investigated the use of 

 ground feldspar as a source of potash on oats. The results are given 

 verbatim from the records of the station : 



In connection with the experiments with finely gi'ound phosphatic rock as a 

 source of phosphoric acid for plants, pot experiments have been undertaken to 

 determine to what extent plants can avail 'themselves of the potash of potash 



aAnn. Kept. Maine State Col. Exp. Sta., 1889, p. 143. 



104 



