The scientific research and the agricultural practice proved that tobacco is a crop which tolerate itself as previous crop. Although, unlike the single-crop system, the rotation brings its benefit for obtaining high yields of tobacco, of better quality and profitable, making that the soils keep their normal agro-productive features and determining the reduction of the rate of infestation with weeds, diseases and specific pests.

The research was conducted at the Experimental Field Voicesti, in long-term rotation with Oriental tobacco and in single-crop system, having in view the place of tobacco in this system, and also the evolution of soil fertility and the maintenance of yield capacity and tobacco quality at a high level for a quite long period of time: 1982-2000.

For the Oriental tobacco, the following crop rotations were studied:

a) crop rotation of 2 years: wheat-tobacco; barley-tobacco; oats-tobacco;
b) crop rotation of 3 years: wheat-tobacco-corn; barley-tobacco-corn;
c) crop rotation of 4 years: wheat-tobacco-corn-vegetables; wheat-tobacco-barley-vegetables.

Very good results of yield and quality were obtained for Oriental tobacco Djebel in 4 year rotations like: oats-tobacco-corn-beans or oats-tobacco-corn-corn, by a well balanced application of the chemical and organic fertilizers.

The agrochemical and microbiological analyses of the soil made at the end of each 4 year cycle of experiment showed the important role of the 4 year rotation and of the fertilization (organic, chemical, mixed) in the maintenance of the best content of NPK in the soil and of the most appropriate biotic activity of the soil with favourable contribution upon the yield and quality of the Oriental tobacco. Compared with the single-crop system, the 4 year rotation brings considerable increases in yield, this rings an alarm signal for those that consider the benefit of one-crop system for Oriental tobacco.

This system, practised for a long time (16-20 years) led to a poor use of the fertilizers, situation which was aggravated because of the droughts in the last years, with obvious impacts upon yield and even upon industrial and chemical-smoking quality of tobacco.

The 4 year rotation makes that also the unfertilized check for a long period (16-20 years) to record a quite high average yield for the Oriental tobacco, maintaining its genuine quality.