Risco climático para implantação do consórcio milho com brachiaria no estado do Maranhão

Abstract

Agriculture is susceptible to various types of risks that directly or indirectly affect production and, consequently, the economic return of the activity. Among these, climate risks are those that have historically caused the greatest damage to agricultural activity, by reducing production. The objective of this work was to analyze the climatic risk in which the varieties Zea mays L and brachiaria ssp are subject to define the best planting times. The survey was conducted in the state of Maranhão using the SARRA (Regional Agroclimatic Risk Analysis System) program. This system determines the soil water balance for agricultural crops. The analysis was based on the cycle and phenological phases of the corn crop, for cultivars with an average cycle of 120 days. Phases I and III were considered critical, with potential for the occurrence of water deficit, for the consortium, with durations of 10 and 45 days, respectively. The degree of climate risk considered for the crops was given as a function of the Water Requirements Satisfaction Index - ISNA, which represents the relationship between actual evapotranspiration and maximum crop evapotranspiration. Seven simulations were carried out in 10 homogeneous rainfall regions, always in the first ten days of each month, between the months of October and April, a period that corresponds to the growing season for rainfed crops in the state of Maranhão. Medium textured soils were considered. The results showed that all homogeneous precipitation regions presented favorable climatic conditions for the implementation of the consortium in the first 10-day period of each month of the analyzed period, except in October. In the first ten days of October, there is no water availability in the initial phase of deployment of the consortium in all homogeneous regions, however, as of November, water availability in the soil both in phase I (sowing and emergence of corn x brachiaria) and in the phase III (flowering and grain filling for corn) was favorable, with minimized risk, as it fully met the water requirements for planting. It is noteworthy that the planting period, although it can be carried out from the first ten days of November, is different in each homogeneous region