June, 1940] Experiments With Potatoes 21 



Jackson farm results : 



TABLE XXI. Fertilizer treatments and organic carbon in pounds per acre at 

 the beginning and end of 12-year period, with odds for significance. 



Treatment 1927 1939 Difference OddT 



4-8-7 Check 75.000 65,600 - 9400 >100-1 



4-8-7 (3,000 lbs.) 79,600 68,000 - 11600 



4-8-14 6 vrs" j ^^'^^^ ^^'^^^ - "^^^^ 



4-16-7' ' ^' 69,600 66,600 - 3000 



4-8-0 + L* 72,600 65,200 - 7400 V 



4-8-7 + L* 72,000 66,600 - 5400 



*L in this table equals 2 T. ground limestone. 



TABLE XXIL Fertilizer treatments and per cent and average yearly increase 



or decrease in organic carbon. 



Treatment Per Cent Increase or Yearly 



Decrease in O. C. Average 



Lane farm — 6 years 



-3.80 -0.63 



-3.E0 -0.63 



+4.29 +0.72 



+2.95 +0.49 



-3.14 -0.52 



-7.99 -1.33 



-0.-9 -OOi 



-2.73 -0.46 



-2.48 -0.41 



-5.00 -0 33 



-6.96 -1.16 



8-16-14 (1000 lbs.) -3.73 -0.62 



4-8-7 No Mg. -4.56 -0.76 



Jackson farm — 12 years 



4-8-7 Check -12.5 -1 01 



4-8-7 (3000 lbs.) -14.6 -1.22 



4-8-10 — 6 vrs. I , -, , i r.-, 

 4-S-14 — 6 vrs. ) 



4-16-7 - 4.3 -0.36 



4-8-0 + L -10.2 -0.85 



4-8-7 + L -10.3 -0.86 



Discussion of Results 



The losses of organic carbon from the check plots on the Lane farm 

 were not statistically significant. However, several other treatments of 

 similar natm'e gave significant or nearly significant resnlts for similar de- 

 creases. These inclnded the one-half ton 8-16-14 application and the 

 4-8-7 no magnesium application. Little, if any, benefit was derived from 

 the magnesium in crop yields. These three treatments gave total losses 

 of 2000, 2100, and 2400 pounds of organic carbon per acre for the six 

 year period. These values represent losses of 0.63, 0.62, and 0.76 per 

 cent per year. 



