16 MASS. EXPERIMENT STATION BULLETIN 369 



tilled, fertilized, and seeded to a pasture mixture once every 3 to 6 years. Pastures 

 of this type have given very satisfactory results in Massachusetts and the acreage 

 of such pastures is increasing rapidlj'. The success of semi-permanent pastures 

 may be largely explained on the following basis: 



L Tillage of the soil, accompanied by adequate fertilization improves the 

 soil's physical condition and raises the level of soil fertility to such a point 

 that nutritious and productive pasture species are able to establish them- 

 selves and remain productive for several years. 



2. The use of a seeding mixture has permitted the introduction of desirable, 

 high-yielding pasture species which not only increase the total production 

 of pasture herbage but also aid in maintaining a more uniform production 

 of herbage throughout the pasture season. 



3. The importance of desirable grazing management practices has been fre- 

 quently demonstrated on pastures of this type with the result that grazing 

 management technique, in general, is given careful consideration. This 

 favors a more uniform production of a high quality herbage throughout 

 the grazing season and aids in prolonging the life of the seeding. 



COOPERATIVE TOBACCO INVESTIGATIONS 



Conducted by the Bureau of Plant Industry, United States Department of Agri- 

 culture in Cooperation with the Massachusetts Agricultural Experiment Station 



C. V. Kightlinger, U. S. D. A., in Charge 



Black Root-Rot. (C. V. Kightlinger.) This project, to develop new strains of 

 Havana Seed tobacco which will be highly resistant to black root -rot and accept- 

 able for type and quality of tobacco and producing capacity under Connecticut 

 Valley conditions, is being continued. 



Havana Seed 211 is the most acceptable of the new strains of tobacco which 

 have been developed and tested thoroughly in the course of the project so far. 

 It is grown commercially in considerable amounts each year in the Connecticut 

 Valley, and is bought and used in like amounts each year by most of the dealers 

 and manufacturers who deal in and use Connecticut Valley tobacco. It comes 

 near to fulfilling the principal objectives of the project, but it needs some improve- 

 ment in minor characteristics. Selections within the strain are being made and 

 tested each year, in an attempt to improve the strain in this respect. 



New strains are also being produced by crossing the most acceptable selections 

 of Havana Seed 211 and highly approved strain? of regular Havana Seed, and 

 selections from the progeny of these crosses and their backcrosses are being made 

 and tested, to provide new material for use in the project, in case the selections 

 of Havana Seed 211 do not possess all the improvements that may be desired. 



Overwintering of Common Tobacco Mosaic Virus in Soil under Natural Con- 

 ditions. (C. V. Kightlinger.) One purpose of this project was to ascertain whether 

 common tobacco mosaic virus contained in plant material could overwinter in 

 soil under natural conditions in the Connecticut Valley, and if so, to what extent 

 the virus overwintered in such manner might constitute a source of inoculum for 

 infections of mosaic in succeeding crops of tobacco, under the conditions of the 

 experiment. Another purpose was to ascertain to what extent mosaic inoculum 

 might be disseminated from diseased to nondiseased tobacco plants by means 

 of ordinary cultural practices. 



The land used in working the project had not grown an>' Solanaceous crops 

 and had not had any refuse material of such crops placed upon it for more than 



