Culture alternation, effect on soil in tobacco zones of Pinar del Rio province

The tobacco constitutes an important source of income to the Pinar del Rio province. However, production technologies have contributed to the degradation of soils; crop alternating is one of the effective measures to mitigate this effect. The objective of the investigation was to evaluate the incidence of different variants of alternation in some chemical and physic - chemical properties of the soil. The work was developed in areas dedicated to the tobacco crop, the variants of alternation evaluated were uncultivated soil, tobacco - fallow, tobacco - corn and tobacco - polycultures. In the selected areas, 96 samples were collected at depths of 20 cm and 40 cm and 40 producers were surveyed. Descriptive statistical methods were applied to compare the means in each variant of land use. The results showed that the predominant pH was slightly acidic, the tobacco-fallow variant showed values close to neutrality. The content of organic matter did not exceed 1% in the variants of cultivated soils inferior to those not cultivated, changeable bases and cation exchange capacity were similar in the cultivated soils, and the calcium showed the highest values in tobacco-fallow. It is concluded that the different land use variants did not have a marked effect on the pH values. The content of soluble phosphorus increased in all the variants of cultivated soils. The alternation of crops, as the only measure of improvement, does not guarantee an improvement in the chemical and physic - chemical properties of the soils.