24 



USE OF FELDSPATHIC KOCKS AS FERTILIZEES. 



stunted and much less developed than those in the other two plats. 

 The tobacco grown in plats Xos. 1 and 2 was evenly developed, fully 

 matured, and of a good quality. It was carefully harvested in the 

 usual way and the yield of green tobacco weighed. After curing, the 

 actual yield of leaf was also recorded. The results, which are shown 

 in the following table, appear to indicate that the feldspar potash 

 was available to quite the same extent as that which was added as 

 potassium carbonate : 



Table III. — Result!^ of (/rcoiliouxc crpcriments vith tobacco plants. 



No. 



of 



plat. 



Source of potash. 



Potassium carbonate 

 Ground feldspar 



, . , Estimated , „^,■,a^ 



^vti'Sfof'^^■^*^^^^'^^vtigMof 



^eencrop. %frl^,T' curel leaf. 



Pounds. 

 1.54.0 

 1.55. 

 128.5 



I'ounds. 

 30,800 

 31,000 

 25,700 



Poinids. 

 .5.70 

 6.30 

 5.30 



Estimated 



weight of 



cured leaf 



per acre. 



Pounds. 

 1,140 

 1,260 

 1,060 



These yields do not in any case equal those obtained in the field 

 under the best crop conditions, but for a winter greenhouse crop 

 raised in shallow beds they are satisfactory. 



On the completion of the greenhouse experiments arrangements 

 were made to carry on field trials in Connecticut and Florida under 

 standard crop conditions. In the tobacco-growing district of Con- 

 necticut it is cu.stomary to use from 150 to 250 pounds of carbonate 

 of potash to the acre of tobacco. The cooperation of several promi- 

 nent tobacco growers was obtained, who each agreed to try an acre, 

 substituting for the usual carbonate 1 ton of potter's spar, running 8.3 

 per cent of pota.sh, or 186 pounds to the ton. The broadcasting and 

 working in of the feldspar was done under the personal supervision 

 of representatives of the Department of Agriculture, and none of the 

 experimental acres received any pota.sh except that contained in the 

 ground spar. All the experimental fields did as well as any in their 

 neighborhood and matured excellent crops. The following letters 

 were received from the growers themselves in regard to the use of 

 feldspar : 



Tariffville, Conn., February 11, 1907. 



Dear Sir : In reply to your letter of February 5, I would say that I used the 

 ton of finely ground feldspar as a potash fertilizer for tobacco, and used no other 

 form of potash on the plat in connection with the feldspar. This plat (one-half 

 acre) was treated exactly like the rest of our tobacco lands as regards nitrogen, 

 phosphoric acid. lime. etc. 



We had a fine large growth of tobacco where the feldspar was used ; fully as 

 large as any in our fields, and much larger than in some sections of our fields. 



I do not consider this an absolute or hardly a fair test of the feldspar, as it 

 was used on land that had previously grown tobacco for several years, and each 

 104 



