282 MAINE AGRICULTURAL EXPERIMENT STATION. I915. 



different amounts of potash. Four different mixtures were 

 used. In each case the fertilizer contained 4 per cent of nitro- 

 gen (five per cent of ammonia), of which one- third was in the 

 form of nitrate of soda, and 8 per cent of available phosphoric 

 acid. The potash varied as follows : On one plot there was 

 none, on another 2 per cent, on another 5 per cent, and on 

 another 8 per cent. The plots were one-half acre each and 

 they were planted in duplicate. The land had been in grass 

 for two years, one year in oats and the year before that had 

 been in potatoes. No fertilizer had been used since the potato 

 crop of 191 1. In each case the fertilizer was applied at the 

 time of planting at the rate of 1500 pounds per acre. Other 

 than the amount of potash used, all the plots were treated 

 ■exactly alike. 



Throughout the growing season the vines on both the no 

 potash plots were a distinctly brighter green and had a thriftier 

 look than on the adjoining plots. The difference was so marked 

 that it attracted much attention from visitors at the farm. Al- 

 though some slight irregularities occurred in the yield from the 

 different plots, the average figures show fairly consistent in- 

 creases with the increase in potash. The plots without potash 

 yielded no barrels or 302 bushels of merchantable potatoes. 

 The plots with 2 and 5 per cent potash gave practically the 

 same yields of 116 barrels of 320 bushels per acre. The 8 per 

 cent potash plots averaged to yield 120 barrels or 331 bushels 

 per acre. This is an increase of 10 barrels from the 8 per cent 

 plots over the no potash plots. This amount is undoubtedly 

 large enough to be significant and to indicate that the potash 

 increases the yield of potatoes in Aroostook county. 



On the other hand, no barrels (302 bushels) per acre is a 

 good yield — considerably above the average in the county in 

 1915. So far as the results of this one year are concerned, 

 they indicate that a profitable yield of potatoes can be obtained 

 on Aroostook soils without the addition of potash for at least 

 one year. In a few farmers' trials made by the various fertil- 

 izer companies, in which no exact records were made, satis- 

 factory results were obtained without the use of potash by all 

 the growers from whom the Station has heard. 



