CROPPINCx SYSTEMS FOR TOBACCO 17 



Although there is no experimental evidence that these methods are better than 

 that of continuous culture, they appear to be satisfactory for the conditions 

 prevailing in those sections. In comparison with the conditions and practices of 

 the Connecticut Valley, it should be pointed out that comparatively small amounts 

 of commercial fertilizer and manure are used. Also, yields per acre of tobacco are 

 much below that of the Connecticut Valley. 



In experiments with cropping systems conducted in Maryland (6), rotations 

 were shown to produce more tobacco than did continuous culture, but the results 

 were lacking in consistency. Inconsistent results were obtained from the use of 

 cover crops; rye, and crimson clover having depressed the yield, while vetch in- 

 creased it. The authors concluded from the e.Kperiments: "Except in the case of 

 red clover in a three-year rotation with tobacco and wheat, the results indicate 

 that the legumes in these tests cannot be relied upon to give uniformly satisfac- 

 tory results with tobacco if grown more than two or three times in continuous 

 culture of tobacco or in short rotation of tobacco with other crops." 



In Wisconsin, an important tobacco section, it is rather common practice to 

 rotate tobacco with other crops, but Johnson and Ogden (12) have shown that 

 rotations involving sod-forming crops may be very harmful to tobacco. They 

 ascribe the disease of tobacco known as brown root-rot to the effect of preceding 

 crops, and estimate that over 50 per cent of the tobacco crops of Wisconsin are 

 affected more or less adversely by preceding crops. Timothy and alfalfa in parti- 

 cular are known to produce harmful effects on tobacco. Continuous culture of 

 tobacco is a remedial practice. Conditions surrounding the production of tobacco 

 in Wisconsin more nearly parallel those of the Connecticut Valley than do those 

 of other regions considered. The main differences are in the cropping system and 

 the quantity and method of applying fertilizer. Connecticut Valley farmers use 

 five to ten times as much commercial fertilizer as do Wisconsin tobacco farmers, 

 and less manure. Brown root-rot usually causes more damage in Massachusetts 

 than in Wisconsin. 



In Lancaster County, the principal tobacco-growing section of Pennsylvania, 

 a three- or four-year rotation is common practice. Wheat and clover or alfalfa 

 are commonly present in the rotation, and sometimes corn is grown. It is gener- 

 ally believed (16) that yield and quality of tobacco are better in the short rotation 

 which omits corn. For tobacco comparatively large quantities of manure are 

 used, and this furnishes the bulk of the applied nutrients. Experiments have shown 

 that when the manure is supplemented with commercial fertilizer both yield and 

 quality of the tobacco are enhanced. 



The Connecticut station (1) has reported no experiments with tobacco rotations, 

 but has reported some benefits from the use of cover crops for tobacco in continuous 

 culture. Of several cover crops used, rye, oats, and vetch have produced best 

 results. With respect to cover crops, results in Connecticut agree rather closely 

 with results at this station but different results were obtained from the use of man- 

 ure. In their experiment manure was found to have a progressively bad effect on 

 yield and quality of the crop, while in the Massaachusetts experiments manure 

 gave the best results. There are several possible causes for this difference. In 

 the Connecticut experiments two to four times as much manure was used as in ours. 

 Furthermore, there may have been a difference in the quality of the manure usetl 

 in the two experiments, due to different proportions and kind of bedding materials, 

 etc. The manure used in the Massachusetts experiments was mixed horse and 

 cow manure with a comparatively small amount of sawdust, and being from the 

 accumulation of a year in each case, was in a fair stage of decomposition when 



