Relações entre as instabilidades pluviométricas e as produções de lavouras de sequeiro no Ceará, Piauí e Rio Grande do Norte

Abstract

The instability of rainfall is the rule in the areas in the semi-arid region and constitutes the great adversity for the populations that live under these regions, especially for those who work in agriculture. In these places, the agricultural production is especially unstable, and has as a defining element the occurrence of rainfall. The general objective of this research is to analyze the interface between rainfall instability and harvested areas, productivity and prices of rainfed crops: beans, cassava, corn and cashew in municipalities of the states of Ceará, Piaui and Rio Grande do Norte between 1974 and 2020. Specifically, the research sought: (a) To classify the distribution patterns of rainfall occurring in these states, as well as the levels of instability in the period from 1901 to 2020. (b) Adjust the rainfall patterns observed for each state, to the studied municipalities in Ceará, Piauí and Rio Grande do Norte between the years 1974 and 2020, years in which there is availability of information about the crops; (c) assess the patterns of instability associated with the defining variables of the production of beans, cassava, corn and cashew in the municipalities in the studied period; (d) to assess the interactions that exist between rainfall instabilities and the production of beans, cassava, corn and cashew in the climatic periods defined in the research for the selected municipalities of the states, between the years 1974 and 2020; (e) to assess the existence of resilience to rainfall stresses in the production of these crops in the municipalities and in the years studied. To classify the states' rainfall into drought, normal, and rainy periods, the historical mean and standard deviations of the observed rainfall between the years 1901 and 2020 were calculated. To gauge the instabilities the research used the coefficients of variation of rainfall. To evaluate the synergy between the rainfall of the municipalities studied and the variables that define the production of crops, the productivity index (IPROD) was created among the variables that define the production of crops. For this, it was used the methodology of factor analysis with the decomposition technique in principal components. To assess the occurrence of resilience, the data from the rainfall series of the municipalities were organized in the sequence before and after the droughts, with the IPROD estimated in these periods. Graphical and mean purchase analysis was used to test the resilience hypothesis. The results of the research showed that it was possible to classify the climatic regimes of the states. It also showed that rainfall instabilities are confirmed in the states over the period studied which is transmitted to the variables used to construct the IPROD. The overall conclusion of the research is that there is resilience to rainfall stresses in the states investigated.