94 MASS. EXPERIMENT STATION BULLETIN 388 



Miscellaneous Work 



Soil Acidity in the Orchard. Lime was applied to a Sudbury orchard in which 

 aluminum toxicity was suspected, as mentioned in the report of last year. It 

 appears that both grass and trees were improved by the treatment. With the 

 increasing use of wettable sulfur the danger of injuriously high acidity becomes 

 greater. Not only is there danger of aluminum toxicity, but nitrification in 

 the soil decreases as the soil acidit>' increases. 



Lime and Phosphorus in Planting Trees. We have as yet no evidence that 

 phosphorus is directly beneficial to apple trees on our soils; we know that it is 

 readily fixed in the soil and it follows that orchard applications may not pass 

 into the relatively deep-rooted apple trees. An orchard of 36 Mcintosh trees of a 

 single strain on three clonal stocks was planted in the spring of 194 L One third 

 of the trees were treated with 10 pounds dolomitic limestone, one third with 

 5 pounds triple superphosphate, and one third were untreated. The materials 

 were placed in the bottom of the planting holes and well mixed with the soil. 

 As measured by trunk diameter increase, the trees treated with lime grew most, 

 those treated with phosphorus least, while the untreated trees were intermediate. 



Weed Killing. The attempt to get rid of wild cherries, particularly choke 

 cherries, around the peach orchards was continued. A new weed killer, am- 

 monium sulfam.ate, was tried. It looks very promising. Used at the rate of 

 ^ pound per gallon water, one application was enough to kill small choke 

 cherries and kill or badly damage black cherries. Chlorate weed killers used at 

 the same strength were not so effective on choke cherries and were ineffective 

 on black cherries. 



Ethylene Dichloride Emulsion for Control of Peach Tree Borers. Because 

 of reports of damage from the use of this material in other sections, it is being 

 thoroughly tested in the station orchards. It has been used in 1939, 1940, and 

 1941 in one orchard and in 1940 and 1941 in several others. Applications have 

 been made at 15-day intervals during the fall. The emulsion has been used (1) 

 according to directions, (2) at slightly higher concentrations, and (3) in slightly 

 larger quantities, than recommended. Only one case of injury has occurred; 

 some very vigorous late-growing suckers from the base of some trees were in- 

 jured when applications of the emulsion at the concentration for three-3'ear old 

 trees was applied. This was an overdose for the year-old suckers. Unseasonably 

 hot weather following the application may have had an effect. Injury has never 

 occurred when applications were made according to standard directions. 



Sawdust Mulch. In the summer of 1938, a sawdust mulching program was 

 begun in a small block of bearing apple trees An average of about 4 inches of 

 sawdust was placed under alternate trees to determine the effect of sawdust on 

 subjugation of sod, on soil nutrients and acidity, and finally on tree growth and 

 production The sawdust had little efifect in subduing the grass, which pro- 

 ceeded to grow apace throughout the summer and fall. Unlike hay or straw, 

 which tends to mat down, sawdust does not tend to smother grass. No addi- 

 tional applications were made during the next three years. Neither deleterious 

 nor particularly favorable effects on soil or tree have been observed to date. 



In November and early December of this year, a considerably greater amount 

 of sawdust was applied to the same trees. This time, however, the sod on half 

 of the area under the branch spread was taken up and the soil shaken out. The 

 other half was left in sod. Sawdust to an average depth of 6 inches was applied 

 over the whole area. It is intended to determine the comparative feasibility of 

 using a sawdust mulch on cultivated soil and on sod in a bearing orchard. 



