Adequação do sistema de avaliação da aptidão agrícola das terras às condições edafoclimáticas do semiárido

Abstract

The rational use of soil requires a correct adequacy of agricultural land uses, basing on the potentialities and limitations of each area; for this, there are several systems of interpretative classification technical. The System of Agricultural Land Suitability Evaluation (SALSE) is widely utilized, firstly developed for countries of the temperate climate and adapted afterwards to regions of Brazil that have humid tropical climate where edaphoclimatic conditions are distinct from conditions of the semiarid northeast. Thus, the aim of this study was to propose adjustments to the SALSE to edaphoclimatic conditions of the Brazilian semiarid region, reducing the restrictions imposed by the attributes rock fragments and effective soil depth, and also by the limiting factor water availability. This work assessed the agricultural potential of the land Mesoregion South of the Ceará using the SALSE, from a conventional method and from the adaptation of this system to the edaphoclimatic conditions of the semiarid region. These adaptations were denominated adapted method I and adapted method II. In the adapted method I the water availability factor was disregarded, while at method adapted II new limits were established for the classes of effective soil depth, besides disregarded the water availability factor. Furthermore, was used geotechnologies to survey the land use and land cover and the mapping of susceptibility to erosion of this mesoregion. The adaptations established in SALSE resulted in an increase of 177.19% of the areas with regular suitability for crops to the detriment of areas with limited suitability for crops and with suitability only planted or natural pasture. Altogether, the changes made to SALSE resulted in an expansion of the agricultural suitability of 41.26% of the mapping units, of which 16.77% of this increase was due to the changes related to the effective depth soil and the other 26 35% were due to changes related to the water availability factor. The results related to water availability factor were equivalent to results observed by analysing the use dynamics and land cover as a consequence of rainfall, then was demonstrated increase the land destined the dry farming and reduction of fallow areas, and pastures in the years that occurred rainfall within the normality climate. These results show that the water deficit is the main limitation to agricultural use of semiarid land. Moreover, 16.53% of the study area have a high susceptibility to water erosion and the modifications established in SALSE, not always, have intensified the risk of degradation of these lands.