20 MASS. EXPERIMENT STATION BULLETIN 355 



seasons has ranked high in these tests, this season gave low yields, possibly be- 

 cause of leaf roll. In order of rank, the 8 varieties are as follows: Green Mountain, 

 Houma, Warba, Russet Rural, Cobbler, Katahdin, Chippewa, Golden. 



The Comparative Nutritive Effects of Copper, Zinc, Chromium, and Molyb- 

 denum. (H. Robert DeRose, W. S. Eisenmenger, and W. S. Ritchie.) Buck- 

 wheat and barley were again grown in white sand cultures, using Knops' nutrient 

 solution, to which the elements copper, zinc, molybdenum, and chromium, were 

 added. The sand used was shown to be free of any contaminating metals by 

 spectrograhic analysis, conducted by the workers in the laboratories of the United 

 States Department of Agriculture in Washington. 



The addition of small amounts of copper and zinc (less than 5 p. p.m.) had a 

 stimulating effect, increasing the total dry weight of the buckwheat. Any amount 

 above 5 p. p.m. of copper and 10 p. p.m. of zinc had a depressing effect, decreasing 

 the total dry weight of the plant as well as adversely affecting the root system. 



Molybdenum had a stimulating effect on buckwheat up to 10 p. p.m., beyond 

 which the total dry weight of the plant was decreased as was the general size of 

 the root system. 



Results obtained with the barley plant with copper and zinc were the same as 

 for the buckwheat plant. Barley was more tolerant to molybdenum than buck- 

 wheat, for the maximum dry weight was obtained with 40 p. p.m. 



Chromium had little if any stimulating effect on barley in small quantities, 

 while larger quantities (40 p. p.m.) killed the plants. 



Further Studies with Calcium Cyanamid as a Weedicide. (Lawrence S. Dick- 

 inson and Hrant M. Yegian.) On a Merrimac soil type, effective control of 

 crab grass was obtained in an established Kentucky' bluegrass lawn, known to 

 be heavily infested with crab grass seed. On plots receiving a single application 

 March 1, 10 to 15 pounds per 1,000 square feet gave the most effective control 

 of crab grass. Slightly better control of crab grass and less injury to the lawn, 

 however, resulted from two applications (10 pounds per 1,000 square feet on 

 March 1, followed by 10 pounds on June 5) than was obtained from the single 

 15-pound application on March 1. June 5 is just prior to the normal germinating 

 time of crab grass at Amherst. 



As a preseeding weedicide to control crab grass, calcium cyanamid, raked into 

 the surface two inches of the graded lawn at the rate of 20 pounds to 1.000 square 

 feet, reduced the crab grass population to a practical minimum. 



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 improve Havana 

 Seed tobacco was begun several years ago. The objective and the plan of work 

 were both given in last year's Experiment Station Annual Report. No important 

 changes have been made in either since the project was begun, although its differ- 

 ent phases have been stressed in progressive order, and the work done has been 

 varied as circumstances and needs of the problem necessitated. 



Many new strains of Havana Seed tobacco have been produced during the 

 course of the project. A large number of these strains have been tested experi- 

 mentally, and several of them have been found to possess much merit. 



