8 MASS. EXPERIMENT STATION BULLETIN 369 



yield and quality of tobacco. However, 1939 was regarded as an unusually good 

 tobacco year in this locality, and the differences in yield and quality of tobacco 

 following the various crops were not so great as in 1938, which was considered 

 a poor tobacco year. 



Tobacco Grown on Old Sod. An attempt has been made to overcome the un- 

 favorable effects on tobacco yield and quality usually witnessed when old sod is 

 plowed under preceding a crop of tobacco. 



An old timothy sod area was divided into four plots. Plot 1 was given an 

 application of 200 pounds of nitrogen in midsummer of the year before tobacco 

 was grown, and plowed immediately; Plot 2 received no nitrogen, but was plowed 

 at the same time as Plot 1 ; Plot 3 was given the same nitrogen treatment as Plot 

 1, but was not plowed until the following spring; and Plot 4 received no nitrogen, 

 but was plowed at the same time as Plot 3. 



Plot 1 showed the highest yield and crop index, indicating that the addition 

 of nitrogen to sod plowed the previous summer had caused the greatest decomposi- 

 tion of the ligneous materials in the sod. On the other hand, applying nitrogen 

 the previous summer and allowing the grass to grow produced an accumulation 

 of vegetation which only added to the supply of tissue and retarded the growth 

 of the tobacco. There was probably more nitrogen in the vegetation and soil 

 of this plot (3) than of Plot 4, but it was of little avail in the presence of too much 

 tissue. Lignin is one of the last components to decompose, while ammonification 

 and nitrification are contingent upon the first stages of decomposition. 



The Use of Nitrogen as an Aid in Decomposing Old Sod. (Karol J. Kucinski 

 and Walter S. Eisenmenger.) Calcium cj'anamid at the rates of 100 and 50 

 pounds of nitrogen per acre was added to an old sod before it was plowed under 

 in the fall of 1938. Another similar sod area, receiving the same fertilizer treat- 

 ment, was plowed under in the spring of 1939. Although this year's growing 

 season was exceptionally dry, thus hindering the decomposition and nitrification 

 of the old sod, it was found that yields of potatoes, corn, and cabbage were in line 

 with those obtained in previous years. Determination of nitrate nitrogen 

 throughout the growing season for the past three years showed that the rate 

 of decomposition of the old sod was faster where nitrogen was plowed under. 



Although the differences in yields and chemical analyses between the re- 

 spective treatments were not as great as in previous years owing to the abnormally 

 dry growing season, yet the addition of nitrogen to old sods before they are 

 plowed under seems to aid in their decomposition and thus lessens their usually 

 harmful effect. 



The Relative Rate of Nitrification of Nitrogen Materials on Certain Tobacco 

 Soils. (Walter S. Eisenmenger and Julien Richard.) The purpose of this in- 

 vestigation was to ascertain the fate of various forms of nitrogen from different 

 sources and to establish the length of time each form could be depended upon to 

 furnish a supply of nitrogen to the growing tobacco plant. The materials used 

 were urea, sulfate of ammonia, dried blood, and cottonseed meal. Addition of 

 phosphorus increased the rate of nitrate formation. Organic matter supply was 

 important in increasing nitrate formation. The maximum rate of nitrate forma- 

 tion was reached in approximately thirty-five days, and nitrification apparently 

 stopped in fifty days. In general rate of nitrification, the several materials are 

 ranked as follows (in decreasing order): (1) urea, (2) sulfate of ammonia, (3) 

 dried blood, and (4) cottonseed meal. 



The Absorption by Food Plants of Chemical Elements Important in Human 

 Nutrition. (Walter S. Eisenmenger and Karol J. Kucinski.) Lettuce, cabbage, 

 and celery were grown on soil to which the cations sodium, potassium, magnesium, 



