1 Ocr., 1898.] QUEENSLAND AGRICULTURAL JOURNAL. 263 
POTATO CULTURE. 
POTASSIUM SALTS AS THE BASIS OF POTATO FERTILISERS. 
Or all crops grown, the potato is the one which shows the greatest content of 
potash in the mineral constituents withdrawn from the soil. Hence the well- 
known value of soil derived from granitic detritus for potato culture. In it we 
haye abundance of potassium silicate derived from the decomposing felspar and 
slowly set free in other forms for the uses of the plant. Hence may be gathered 
the datum that, given a soil not very liberal in its return of tubers, the defect 
is probably in that the potash percentage is low. 
Where ground has been annually cropped with potatoes for many years 
without a rotation, it is mainly owing to the potash having been used up. Then 
the remedy is to supply that ingredient. This may be done either by a direct 
application of sulphate or chloride of potassium as a chemical top-dressing, or 
by a proportionate quantity of wood ashes. : 
The matter has been gone into carefully by the United States Experi- 
ment Stations from 1888 to1896 . . . Part of their summing up was as 
follows :-— 
“Two hundred pounds sulphate of potash produced an increased yield 
slightly exceeding that given by 80 loads of stable manure. The results were 
the same with potassium chloride. There was a profit of 21°438 on the plot 
with sulphate of potash alone. The increase on plot 11 with 80 loads of barn- 
yard manure did not yield enough per cent. to pay for the hauling out of the 
manure. The results show that the profit is in the use of potash compounds, 
and that the money spent on ammoniac sulphate and superphosphate was entirely 
lost” [meaning in potato culture].—M. A. Servell, Kentucky Experiment 
Station, 1888, Bulletin No. 16. : 
‘Neither superphosphate nor nitrate of soda (Chili saltpetre) used 
separately or together were of appreciable benefit; but when either was used 
with sulphate of potash, great advantage accrued.”—Jdem, 1889, Bulletin No. 
22. 
“The experiments of three years, 1884-1886, show that the yield was 
largely increased by fertilisers containing potash. In 1884 the plot receiving 
potassium chloride was free from scab.”—M, A. Goessmann, Massachusetts 
Experiment Station, 1886. 
“The soil here is gravelly loam. Potash was evidently more beneficial 
than either superphosphate or nitrogen (ammoniac nitrate). Alone, it pays by 
itself and more, but is more effective when used in conjunction with both 
phosphoric acid and nitrate of soda. For the soil, the formula of a fertiliser 
would be about as follows :—Nitrate of soda, 30 lb.; superphosphate, 60 lb. ; 
chloride of potassium, 100 Ib.’—W. L. Phillips, Marblehead Experiment 
Station, 1892, Bulletin No. 18. ; 
“ Soil, a heavy loam. The average of three years’ experiments shows that 
nitrates produced 10:74 bushels increase, phosphates 10°11 bushels, potash 41:45 
bushels. It is clear, then, that in this soil the commercial fertilisers should 
contain much more potash than is usually the case.’—L. W. West, Hadley 
Experiment Station, 1890. 
“Hyery test adds to the position that vastly more potash is needed than 
our potato fertiliser manufacturers give us. The average fertiliser (New 
Hampshire) should be phosphoric acid, 9-1L per cent.; nitrogen, 2-4 per cent. ; 
potash, 9-15 per cent.; whereas the fertilisers in the market average— 
Phosphoric acid, 11 per cent. ; nitrogen, 2°5 per cent.; and potash, 2°5 per cent. 
only. I recommend (of course, for potatoes) dissolved bone black (de., 
superphosphate), 340 lb.; potash chloride, 160 lb.”—E. 8S. Whittlemore, 
Colebook (N.H.) Experiment Station, 1890, Bulletin No. 12. 
“Mo plot 5, no fertilisers were added. To plot 3, 400 Ib. of super- 
phosphate and 800 Ib. kainit (potassium and magnesium chloride) per acre 
were applied. The yield of plot 5 was 86% bushels per acre; that of plot 3 
