68 MASS. EXPERIMENT STATION BULLETIN 449 



Chemical Control of Weeds. (J. S. Bailey.) In 1946 and 1947 it was found 

 that ammonium sulfamate and a proprietary weed killer containing sodium 

 chlorate and a deflagration agent could be used around apple trees four years of 

 age to control weeds. A report of this work appeared in Vol. 51 of the Proceed- 

 ings of the American Society for Horticultural Science. 



To see whether these materials could be used around year-old apple trees and 

 how much, applications were made in August, 1947. Ammonium sulfamate 

 was used at %, IJ^, 3, and 6 pounds per gallon and the proprietary mixture at 

 1,2, and 4 pounds per gallon. One gallon of each concentration was sprayed in a 

 circle about 6 feet in diameter around a tree. Treatments were made in quad- 

 ruplicate. 



Ammonium sulfamate at 6 pounds per gallon caused the trees to lose all their 

 leaves in the late summer of 1947. A new crop of leaves started to appear later 

 but these trees all died during the winter. The other concentrations caused a 

 dwarfing of the trees roughly proportional to the amount used. Also, they caused 

 in 1948 a chlorosis of the leaves which varied from a yellowing of the margins to 

 a yellowing of the entire leaf. 



One and two pounds of the proprietary mixture caused a slight dwarfing of 

 the trees. Four pounds caused considerable dwarfing. 



Since a circle 6 feet in diameter contains an area of about 28 square feet, the 

 quantity of each concentration applied was nearlj^ four times the amount which 

 would ordinarily be used. 



All concentrations of both materials killed all weeds including quack grass 

 {Agropyron repens). A considerable growth of clover and some annual weeds in 

 1948 indicate that the soil was not sterilized for any great length of time. 



In the spring of 1947 experiments were started on the control of weeds in straw- 

 berry beds with 2,4-D. A comparison was made between 2,4-D acid put in solu- 

 tion with Carbowax 1500, the sodium salt of 2,4-D, and an ester formulation. 

 The ester formulation appeared to be too toxic to the strawberry plants. The 

 2,4-D acid and the sodium salt appeared about equally effective in the control of 

 broad-leaved weeds and the effect on the strawberry plants was slight and tem- 

 porary. The sodium salt is much easier to put into solution. 



In the spring of 1948 these experiments were continued and expanded. One 

 series of plots was laid out in a renovated bed where the sodium salt of 2,4-D, 

 isopropyl-N-phenyl carbamate, dinitro-ortho-secondary-butylphenol, phenyl- 

 mercuri acetate, Stoddard solvent, and some combinations of these are being 

 tried. Another series of plots was laid out in a newly set bed where the sodium 

 salt of 2,4-D, isopropyl-N-phenyl carbamate, phenyl-mercuri acetate, phenyl- 

 mercuri triethanol ammonium lactate, and ammonium sulfamate and combina- 

 tions of some of these are being tried. 



Nutrition of the High-Bush Blueberry, Especially in Relation to Soil Reaction. 



(J. S. Bailey.) Leaf symptoms, which were very similar to those produced in 

 sand cultures by withholding magnesium, appeared on a few of the blueberry 

 bushes in the University planting at Amherst. In order to find out whether 

 this was magnesium deficiency and whether or not it could be corrected by appli- 

 cation of magnesium, a series of plots was laid out on some of which magnesium 

 sulfate at 500 pounds per acre was broadcast on the soil and on others it was 

 sprayed on the plants. 



Leaf samples were obtained from these plots before and after treatment and 

 from normal appearing bushes in the Cape Cod section. These samples were 

 analyzed for P, K, Mg, and Ca by Mr. C. Tyson Smith of the Feed and Fertilizer 

 Control Service. Compared with apple leaves, the content of P, K, and Ca was 



