1188 EARLE V. HARDENBURG 



region. The increase in yield obtained by growers using $15 worth or more 

 of manure and fertilizer, over that obtained by growers using less, was 

 sufficient to warrant the extra cost. Only twelve growers in this region 

 used more than $25 worth of manure and fertilizer per acre. In view of 

 the decreasing rate of increase in yield between the last two groups, 

 it is doubtful whether a larger expenditure than $25 an acre would have 

 shown a profitable increase. The correlation coefficient for this factor and 

 yield, as shown in figure 139, is 0.169 db 0.038. This indicates a significant 

 relation, but one not so strongly marked as that for the other three regions. 



Yield per acre, in bushels . 



SOO>-OQ*OOOQ 

 <M*Ot^O<NiOl^O 



20 

 90 

 111 

 52 

 13 

 8 

 1 

 2 

 1 



11 27 49 52 76 38 26 14 5 298 

 r = 0.169 0.038 



FlG. 139. CORRELATION OF VALUE OF MANURE AND FERTILIZER, AND YIELD, ON 298 FRANKLIN 

 AND CLINTON COUNTY FARMS IN 1913 



Analysis of fertilizer 



The average potato grower of New York is even yet none too familiar 

 with the significance of fertilizer .analyses. As previously stated, it was diffi- 

 cult to get information as to the analyses of the brands used, many of the 

 growers having been more impressed by the price paid or the brand name. 

 Most of the fertilizer experiments for some years have justified the practice, 

 as found in the surveyed regions, of using fertilizers in complete form for 

 potatoes. 



Aside from the more fundamental physiological processes stimulated by 

 each of the essential plant-food elements in plant growth, nitrogen func- 

 tions principally in producing foliage, phosphorus in hastening maturity, 

 and potash in increasing starch production. These elements in combina- 

 tion naturally maintain a balance of value in successful potato production. 



Whitney (1910), in summarizing fertilizer tests on potatoes up to 1908, 

 showed that: (1) there has been a consistent increase in the average yield 

 of potatoes with the increase in the number of minerals used in mineral 

 fertilizers; (2) there has been a similar increase in the average yield from 

 an increase in the number of minerals used in combination with organic 



