Título en español

Two experiments, one in 1062-63 and the other in 1963-64, were conducted at the same site to determine the effect that fumigating undisturbed soil has on the effectiveness of methyl bromide as soil fumigant in tobacco seedbeds. Beds were made of concrete blocks. A layer 8 to 10 inches high of sandy soil was placed over a layer 3 to 4 inches deep of gravel. Methyl bromide was applied at the rate of 2 pounds per 100 square feet under plastic covers during 4 days. In both experiments plots in which undisturbed soil was fumigated with methyl bromide produced more seedlings than beds where the soil was prepared, the difference been significant at the 5-percent level the first year. The data show that, under the conditions of the experiments, the effectiveness of methyl bromide as a soil fumigant was not affected by fumigating unprepared soil. Thus it is not necessary to prepare the soil for making tobacco seedbeds. Consequently, the cost of production is lower in seedbeds where the soil is not disturbed than in those where the soil is prepared. Further studies are necessary to determine the maximum length of time that undisturbed soil could be used for tobacco seedbeds without affecting the effectiveness of methyl bromide and/or the quality of seedlings. Until additional information is obtained it may be recommended that the seedbed be prepared by fumigating unprepared soil with methyl bromide for at least 3 consecutive years.