O brejo e a cana: estudo da variabilidade das chuvas e sua relação com a produtividade da cana-de-açúcar na bacia hidrográfica do rio Icatú, Barra/Ba.

Abstract

This work analyzed the interannual variability of rainfall and its correlation with the productivity of sugarcane in the marshes of the River Icatú Drainage Basin (municipality of Barra/BA), in order to identify the variability of rainfall and its influence on sugarcane productivity. For the analysis of rainfall variability and its relationship with sugarcane productivity in the Icatú River Drainage Basin (IRDB) marshes, a 40-year time series of monthly rainfall data was used, corresponding to the period 1980 to 2020, obtained from the National Institute of Meteorology (INMET), more precisely from the Barra/BA Meteorological Station. The data of planted area, harvested area and quantity produced of sugarcane from the Municipal Agricultural Production (PAM-IBGE) of the municipality of Barra/BA were also used. We adopted a dynamic approach from Geographic Climatology regarding the study of landscape in the context of Geography. The landscape was adopted as a category of Geography and in an integrated geosystemic approach in the perspective of Monteiro (2001) in his works developed in Bahia. The concept of variability guided the development of this work, which was based on the variability of rainfall as mechanisms inherent to atmospheric dynamics and climate and the influence of rainfall variability in sugarcane productivity in the marshes of the Icatú River Drainage Basin (IRDB). The study of rain variability was based on the concepts developed by Marin (1990), Ribeiro (1996), Monteiro (2003), Sant'Anna Neto (1998, 2003) and Tavares (2004). This research was carried out in five stages: the first stage was the collection of specific works for the theoretical basis of the proposed theme, for the characterization of physical-natural and human aspects of the study area as well as to contextualize the origination of sugarcane planting in the marshes. The second stage consisted of collection, selection and statistical treatment of the climatological data of rainfall and temperature and the data of sugarcane production. The third stage is the acquisition of empirical data through interviews and questionnaires in the area of the marshes. The fourth stage consisted of analysis and integration of the results obtained, and finally, the fifth stage consisted in systematization and elaboration of the Master’s Dissertation. The statistical procedures were used to perform the analysis of rainfall variability applied to the treatment of monthly rainfall data to investigate interannual variability. Variability is one of the main characteristics of the tropical semi-arid climate of IRDB. It was observed the occurrence of more than half of the years of the historical series with rainfall below the historical average, while the years with above average rainfall were few for the period of 40 years of record. There is a weak positive correlation between the independent variable rainfall and the dependent variable productivity of sugarcane in the marshes of IRDB. The correlation coefficient R was 0.4 and the Coefficient of Determination (R2) 0.16, which characterizes a weak correlation. Even weak, there is a positive correlation between the rains and the productivity of sugarcane in the marshes. The production of sugarcane in the IRDB marshes in years with rainfall below average (in dry and extreme dry years) was smaller as the harvested area, quantity produced as well as productivity. On the other hand, the years of higher productivity of sugarcane in the IRDB marshes are linked to the "good winters", that is, to rainy years.