Maine Agricultural Experiment Station. 1917. 113 



Discussion of Results 



The 1915 results showed that while there was a consistent 

 increase of yield with the use of potash, nevertheless a profit- 

 able yield of potatoes was obtained without its use. Last yekr 

 the plots without potash averaged to yield at the rate of 110 

 barrels per acre, while the plots with 8 per cent potash gave 120 

 barrels. 



The yields on the different plots in Series I for 1916 show 

 that the addition of potash has resulted in a very marked in- 

 crease in yield. There are some irregularities in that the 8 per 

 cent potash yielded slighly less than either the 2 or the 5 per 

 cent. These differences are probably only random fluctuations 

 due to irregularities of the soil. It must be remembered that 

 field experiments of this kind are at their best very rough com- 

 parison. Such fluctuations are to be expected unless a series 

 of replicate plots are used. A crude comparison of the effect of 

 potash on this soil may be made by averaging the yield of the 

 three plots which had potash and comparing with the average 

 yields of the two plots which had no potash. The three plots 

 averaged 152 barrels per acre, while the two no-potash plots 

 averaged 110 barrels per acre. At the current prices of pota- 

 toes in Aroostook at harvest this means a difference of about 

 $100 per acre. There seems to be no question but that the addi- 

 tion of potash to this kind of land was a very paying proposi- 

 tion under the seasonal condition of this year. 



It will be noted that in the case of Series II, 1916, there is 

 no such marked increase due to the addition of potash as was 

 found in the former series. The first four plots show no signi- 

 ficant difference in yield. The fifth plot on which an 8 per cent 

 potash was used shows an increase of nearly 20 barrels per 

 acre over the preceding. Whether this increase is due to the 

 extra potash alone, or whether it is partly due to soil differences 

 cannot be ascertained. It seems very probable that there was 

 a considerable residue of potash in the soil from the preceding 

 crops and that this amount was sufficient to obscure any possible 

 differences in yield due to application of small amounts of potash 

 in 1916. 



From the results of these 3 trials' in 2 seasons the following 

 tentative conclusions may be drawn: First, that the addition of 



