Rainfall instability and per capita production forecast for rainfed food crops in Maranhão State, Brazil

Abstract

We studied the instability of rainfall, harvested areas and aggregate yields of rice, beans, cassava and corn and made projections of per capita production of these crops between 2022 and 2031. Rainfall in Maranhão between the years 1933 to 2020 was placed into three periods: short, normal and rainy. Agricultural production and population data from IBGE were used. Annual rainfall was collected from the National Oceanic and Atmospheric Administration (NOAA). Variable instabilities were estimated by Coefficients of Variation. ARIMA models were fitted for forecasting. Population forecasts were made using instantaneous geometric rate of population growth in two scenarios. The results showed that it was possible to classify the rainfall in the three periods with a high level of instability, which manifested itself in harvested areas and yields. The general conclusion of the research is that the per capita production of these crops presented its highest value in 1982, and from that year on it showed a decline, in such a way that the projections made until the year 2031, in different scenarios of population growth in the state, point to decreases in per capita production.