ANNUAL REPORT, 1947-48 65 



Killer at the rate of 2 to 3 gallons per acre were very effective in controlling 

 weeds in fields of sweet corn as well as snap beans. Granular cyanamid at the 

 rate of 600 pounds per acre prevented weed growth in sweet corn for about 4 

 weeks. 



The Culture and Nutrition of Vegetables. (William H. Lachman.) 



1. Tomato plants mulched with manure produced fruits higher in soluble 

 solids, nitrogen, and phosphorus than those mulched with straw or sugar cane 

 fiber or unmulched. Plots mulched with sugar cane fiber produced lower yields 

 than any of the other treatments, but fruits from these plots were highest in 

 total sugars, carotene, ascorbic acid, calcium, phosphorus, and potassium. The 

 soil in the plot mulched with manure was in the best physical condition, and the 

 organic matter and nitrogen were higher than in the other treatments. (In 

 cooperation with Dr. Holmes of the Chemistry Department.) 



2. Defoliation in determinate varieties of tomatoes such as Pennheart is 

 very serious just as ripening of the fruit begins. Through experiments with 

 varying degrees of blossom removal at anthesis, it was found that an inverse 

 relation exists between fruit load and retention of the foliage. 



3. A chlorotic condition found on the older leaves of greenhouse tomato 

 plants has been diagnosed as magnesium deficiency. Experiments using soil 

 known to be deficient in magnesium indicate that this chlorotic condition may 

 be alleviated by applications of magnesium sulfate or dolomitic limestone. 

 More response from this treatment results if it is combined with a heavy applica- 

 tion of manure. Applications of potash aggravate the chlorotic symptoms. 



4. The use of a plant hormone applied as a spray was effective in increasing 

 the early set of tomatoes. Fruits set well on flowers that had been emasculated 

 before anthesis and were entirely seedless. 



5. Automatic surface watering of greenhouse tomatoes has a distinct pos- 

 sibility but the proper level of soil moisture content has not been determined. 

 A layer of sand about one inch deep on the surface of the soil was found to be of 

 value in distributing water laterally over and through the beds. 



DEPARTMENT OF POMOLOGY 

 A. P. French in Charge 



The Influence of Various Clonal Rootstocks on Apple Varieties. (W. D. Weeks 

 and F. W. Southwick.) Although frost reduced the 1947 crop in the large stock- 

 scion orchard, the crop was the largest to date. Eight-year-old trees of Red 

 Spy on Mailing II averaged over a bushel of fruit per tree, while trees on Mailing 

 XVI averaged less than one-tenth bushel. In general, the yields of other vari- 

 eties were greater on Mailing I and II than on other stocks. 



Seeds of two ornamental type crabapples, Malus sikimensis and Malus torin- 

 goides, which show promise as rootstocks, were obtained from the Arnold Ar- 

 boretum. Seedlings of these will be budded to several commercial varieties for 

 testing as to their value for root-stocks. 



Lethal Incompatibilities Between Clonal Stocks and Varieties of Apples. 



(W. D. Weeks.) More evidence was obtained to show that the lethal factor in 

 Mcintosh strain R can be transmitted to the congenial Mcintosh strain G. It 

 was also demonstrated that the lethal factor in strain R does not depend on 



