20 MASS. EXPERIMENT STATION BULLETIN 297 



9. Likewise, the several cropping; systems produced hardly perceptible changes 

 in stable or semi-permanent organic matter of the soil. Only in the case of 

 timothy used as a cover crop or in rotation was there any increase in the organic 

 matter which could be assigned to anything more than chance variation. How- 

 ever, it does not necessarily follow that because of a failure to produce measurable 

 permanent changes in the amount of soil organic matter, the added organic matter 

 has not been of value. 



References 



L Anderson, P. J., Swanback, T. R., and Street, O. E. Tobacco Substation at 

 Windsor, Report for 193 L Conn. (State) Agr. Expt. Sta. Bui. 335 (1932). 



2. Anderson, P. J., Swanback, T. R., and Street, O. E. Potash requirements 



of the tobacco crop. Conn. (State) Agr. Expt. Sta. Bui. 334 (1932). 



3. Beaumont, A. B. Soil shifting in the Connecticut Valley- Science 56: 



282-283 (1922). 



4. Beaumont, A. B., Larsinos, G. J., Piekenbrock, P., and Nelson, P. R. The 



assimilation of nitrogen by tobacco. Jour. Agr. Research 43:559-567 

 (1931). 



5. Beaumont, A. B. The toxicity of ammonium compounds for tobacco. 



Proc. Second Internatl. Cong. Soil Sci. 4: 65-78 (1932). 



6. Brown, D. E., and Lunn, W. M. Cropping tests with tobacco. Md. Agr. 



Expt. Sta. Bui. 275 (1925). 



7. Chapman, G. H. Tobacco investigations: progress report. Mass. Agr. 



Expt. Sta. Bui. 195 (1920). 



8. Doran, \\ m. L. The growth of tobacco and brown root rot of tobacco as 



affected by timothy infusions of different ages. Jour. Agr. Research 36: 

 281-287 (1928). 



9. Heck, A. F. A method for the determination of total carbon, and also 



for the estimation of carbon dioxide evolved from soils. Soil Sci. 28: 

 225-233 (1929). 



10. Hendrickson, C. L An economic study of the agriculture of the Connecticut 



Valley. 4. A history of tobacco production in New England. Conn. 

 (Storrs) Agr. Expt. Sta. Bui. 174 (1931). 



1 1 . Jenkins, E. H. Requirements of the tobacco trade, and how can the grower 



meet them? Rpt. Mass. Bd. Agr. 5* (1906) : 157-172 (1907). 



12. Johnson, Jas., and Ogden, W. B. Rotation and the tobacco crop. Wis. 



Agr. Expt. Sta. Bui. 412 (1930). 



13. Jones, J. P. Report of progress in tobacco investigations. Mass. Agr. 



Expt. Sta. Circ. 74(1927). 



14. Jones, J. P. The effect of other crops on tobacco. Jour. Amer. Soc. Agron. 



21:118-129(1929). 



15. Lathrop, P., and Stockbridge, L. Culture of tobacco as an agricultural 



product. Rpt. Mass. Bd. Agr. 10 (1862) Pt. 1 : 63-69 (1863). 



16. Olson, Otto. Cigar-tobacco production in Pennsylvania. U. S. Dept. Agr. 



Farmers' Bui. 1580 (1929). 



17. Smith, J. M. Tobacco and its culture in the Connecticut River Valley. 



Rpt. Mass. Bd. Agr. 30 (1882) : 136-160 (1883). 



18. Stockbridge, Levi. The rotation of crops. Rpt. Mass. Bd. Agr. 17 (1869) 



Pt. 1:142-154 (1870). 



19. Tisdale, \V. B. Tobacco culture in 1 lorida. Fla. .\gr. Expt. Sta. Bui. 198 



(1928). 



