6 MASS. EXPERIMENT STATION BULLETIN 297 



first, tobacco grown continuously without a cover crop; second, tobacco grown 

 continuously with a cover crop; and third, tobacco grown in a short rotation. 

 The combinations used in the main experiment were: 

 Tobacco grown continuously: 



1. No cover (check) 



2. Manure 



3. Manure and timothy cover 



4. Timothy cover (old series) 



5. Timothy cover (new series)^ 



6. Timothy cover (residual)^ 



7. Red top cover 



8. Rye cover 



Tobacco grown in rotation : 



9. With corn (maize) and timothy (.A.nimal husbandry rotation) 

 10. With corn (maize) and clover (Animal husbandry rotation) 



1 L With potatoes and onions (Cash crop rotation) 

 In addition there were certain other combinations in a supplementary experi- 

 ment running from 1924-1929 which will be described later. Cover crops were 

 sown on a seed-bed prepared by disking the soil immediately after cutting tobacco, 

 at the following rates: Timothy, 25 pounds per acre; red top, 20 pounds peracre; 

 and rye, 1.5 bushels peracre. 



The Soil Used 



The soil on which the experiment was conducted is considered good for tobacco 

 growing, but not the best of the upper Connecticut Valley. It is a water-worked 

 glacial till, and not so productive as some of the deeper alluvial deposits of this 

 section. The surface soil has a medium texture, isclassifiedasa fine sandy loam or 

 loam, and is fairly retentive of moisture. At a depth which varies from almost 

 nothing to about fifteen inches it is underlaid by coarse gravel three feet or more 

 deep. The fine-earth (below 2mm) portion of the soil contained 11.2 per cent 

 fine sand (0.25-0.10 mm), 33.8 per cent very fine sand (0.10 - 0.05 mm), 42.5 per 

 cent silt (0.05 - 0.005 mm), and 8.5 per cent clay (0.005 mm and smaller). The 

 initial reaction of the soil was about pH 5.2 and the organic-matter content at 

 the beginning of the experiment was 2.72 per cent. The efTect of the cropping 

 systems on these soil characteristics will be discussed later. 



This experiment began with the crop of 1924, although tobacco was grown on the 

 field in 1923. For about fifteen years previously a variety of crops, including 

 asparagus, onions, potatoes, squash, corn, and strawberries, was grown. All 

 these crops were well fertilized. 



The Fertilizer Used 



The experiment did not involve any question concerning fertilizers except that 

 of supplying a uniform material in general conformity with the best practice of 

 the growers of the region. Throughout the period of the experiment a 5-4-5 mix- 

 ture was used. Due to differences between guaranteed and actual analysis of the 

 fertilizer ingredients used, there was some variation from the standard from year 



'In 1928 the growth of timothy as a cover crop was discontinued on five plots where it had been 

 grown from 1924-1927; and from 1928-1931 the residual effect of the timothy was studied on these 

 plots. At the same time the use of timothy as a cover crop was started on five plots where it had 

 not been grown previously. 



