i;jO MASS. EXPERIMRN'T STATION BULLETIN 276 



Tahi.k 6. — Incrka;-f. in yield of tobacco on limed i'lots resulting from 

 acidiikatiox tueatments of soil. 



Increase in yield* — per cent 



Acidification treatment 



Plot No. (Pound.s per acre) 1!>26 19-.2T 1928 1929 1930 



9a. 21a Sulfur 200, in 1926 and 1927 49.0 None 20.5 11.0 



91), 21b Sulfur 200, in 1926 only 27.5 34.0 None 14.0 8.0 



10a, 22a Sulfur 400, in 1926 and 1927 43.5 None 14.0 17.0 



10b, 22b Sulfur 400. in 1926 only 34.5 50.5 None 12.5 16.0 



11a. 2:>a Sulfuric acid 1800 + orthophosphoric 



acid 440, in 1926 and 1927 87.0 4.5 19.5 18.0 



lib, 23b Sulfuric acid 1800 + orth()])hosphoric 



acid 440, in 1926 only 58.5 33.5 20.0 10.5 2.0 



* Means for percentage Increase in yields of duplicate limed plots acidified, over 

 their most nearly adjacent check plots (limed but not acidified). 



Beiiinning- in 192(j, tlie tol)acco on limed plots grew nnich better on those 

 plots which had received applications of sulfur or of sulfuric and orthophos- 

 ]>iioric acids than on plots not acidified. The beneficial eit'ect of the acids in 



1926 on the groA\ th of plants on limed plots, as compared with growth on 

 limed plots not acidified, is shown in Figure 2. Yields of tobacco on limed 

 plots were increased by all treatments as comiiared with yields on limed plots 

 not acidified. 



Tlie application of sulfur to plots not limed, and therefore without black 

 root-rot as a factor, did not significantly affect yields that year. (In another 

 field with a less well-buffered soil, its pH value two months after the treat- 

 ments was lowered as follows from an initial pH value of 6.2: by sulfuric 

 acid, 2000 pounds per acre, 0.6; by sulfuric acid, 2000 pounds, and ortho- 

 ])]iosphoric acid, 500 pounds i)er acre, 0.6; bj- orthophosphoric acid, 1000 

 pounds per acre, 0.3; and by sulfur (inoculated), -iOO pounds per acre, 0.4 

 In the practical a7)sence of Thielavia hasicola from the soil of this field, none 

 of these treatments affected the yields of tobacco). 



In 1927 limed plots to which sulfuric and orthophosphoric acids had been 

 ai)])lied for two years (1926 and 1927) yielded as much as plots without lime 

 (and of course without black root-rot). The application of these acids to 

 limed plots for one year only increased yields in 1927 much less than in 1926, 

 the year of application. 



Sulfur, 200 or -IOO pounds per acre, applied in 1926 increased yields on 

 limed plots more in 1927 than in 1926, the year of its api)lication. Sulfur, 400 

 pounds per acre, was mcire eft"ecti\ e in increasing yields in botii years than 

 Avas sulfur, 200 pounds 2)er acre. 



Sulfur aj)i)iic(l to plots not limed, and w itii black root-rot not a factor, 

 resulted in 1927 either in no effect on yields or in increased yields, as com- 

 l)ared with yields of plots not limed and not acidified. Even on unlimed jjlots 

 4h and Kia (with soil pll value 5.-5) to wiiicii sulfur to a total of 800 pounds 

 per acre vas a])j)Hed in 1926 and 1927, yields in 1927 were 6 or 17 per cent 

 larger tiian llic yields of the nearest plots, 6 and 18 respectively, without lime 

 and without acidification. Similarly, on unlimed i)lots 4b and 161), to which 

 sulfur, 400 pounds per acre, was applied in 1926, yields were increased in 



1927 l)y 34 and 16 per cent resj>ectively, as compared with yields of nearest 

 ])l()ts not limed and with no sulfur. Even these relatively heavy applications 



