;j24 MASS. EXPERIMENT STATION BULLETIN 229 



May in 1922, 1923, and 1924, and in April, 1925. 



During each growing season observations on growtli were recorded. Im- 

 mediately after the crop was harvested roots from each plot were examined 

 for black root-rot. 



No yield records were taken in 1921 because of tlie uneven stand, due prin- 

 cipally to setting at different periods. When the crop of 1922 was harvested, 

 160 plants from the four center rows of each plot were weighed. These green 

 weights are recorded in Table I. At the time of harvesting in 1923, 192-t-, and 

 192-5, the tobacco from each entire plot, except for the borders, was hung, 

 stripped, and cured separately. The weights of cured leaves are tabulated 

 by plots in Table I, and the results summarized in Table II. Sorting records 

 for the crop of 1925 were made, and the percentage for each grade and 

 length of leaf in each plot is given in Table III. 



The work and results of each of the last four years are presented separately 

 before discussing conclusions from the whole experiment. 



Season of 1922 



Throughout the summer it was apparent that (1) the timothy strips were 

 making a poorer growth than those which had no cover crop or had clover; 

 (2) the limed plots were making a better growth than the corresponding un- 

 limed plots both on the inoculated and uninoculated parts of the field; (3) 

 the inoculated half was not making as much growth as the uninoculated. 

 These field observations were all substantiated l)y the yield records as given 

 in Table I and summarized in Table II. This siiows that by liming there was 

 a. gain of 12 per cent both on inoculated and uninoculated plots; by the use 

 of a timothy cover crop there was a loss of 13 per cent on the inoculated 

 and 18 per cent on the uninoculated half; and finally that the inoculated half 

 was 15 per cent lighter all through than the uninoculated' half. After cutting 

 the tobacco, some of the roots from each plot were dug and washed. Lesions 

 were found on practically all of the roots from the inoculated plots, but were 

 not much worse on the limed than on the unlimed plots. They were located 

 especially on the large roots at the bottom of th.e stalk where the roots had 

 to grow through the handful of infested earth that was deposited at planting 

 time. A few lesions were found on the roots from the uninoculated half. 



In 1922 the use of lime was associated with an increase in the yield of to- 

 bacco, and was not associated with any great increase in the amount of root- 

 rot. 



This year there was a decided loss in weight of tobacco following the tim- 

 othv cover crop. The percentage of loss from timothy was not as heavy on 

 the inoculated half as on the uninoculated half. 



Inoculated plots uniformly yielded a lighter crop than uninoculated, al- 

 though examination of the roots did not indicate very severe infection. Most 

 of the injury was in the region where the handful of infested soil was in con- 

 tact with the roots and not general over the whole root system. 



Season of 1923 



About the middle of the summer it became apparent that in the infected 

 half of the field the tobacco on the limed strips was lagging behind the un- 

 limed strips in growth. This diiference increased throughout the summer. The 



