Coupling MODIS images and agrometeorological data for agricultural water productivity analyses in the Mato Grosso State, Brazil

Abstract

Mato Grosso state, Central West Brazil, has been highlighted by the grain production, mainly soybean and corn, as first (November-March) and second (April-August) harvest crops, respectively. For water productivity (WP) analyses, MODIS products together with a net of weather stations were used. Evapotranspiration (ET) and biomass production (BIO) were acquired during the year 2012 and WP was considered as the ratio of BIO to ET. The SAFER (Simple Algorithm For Evapotranspiration Retrieving) for ET and the Monteith's radiation model for BIO were applied together, considering a mask which separated the crops from other surface types. In relation to the first harvest crop ET, BIO and WP values above of those for other surface types, happened only from November to January with incremental values reaching to 1.2 mm day^-1; 67 kg ha^-1 day^-1; and 0.7 kg m^-3, respectively; and between March and May for the second harvest crops, with incremental values attaining 0.5 mm day^-1; 27 kg ha^-1 day^-1; and 0.3 kg m^-3, respectively. In both cases, during the growing seasons, the highest WP parameters in cropped areas corresponded, in general, to the blooming to grain filling transition. Considering corn crop, which nowadays is increasing in terms of cultivated areas in the Brazilian Central West region, and crop water productivity (CWP) the ratio of yield to the amount of water consumed, the main growing regions North, Southeast and Northeast were analyzed. Southeast presented the highest annual pixel averages for ET, BIO and CWP (1.7 mm day^-1, 78 kg ha^-1 day^-1 and 2.2 kg m^-3, respectively); while for Northeast they were the lowest ones (1.2 mm day^-1, 52 kg ha^-1 dia^-1 and 1.9 kg m^-3). Throughout a soil moisture indicator, the ratio of precipitation (P) to ET, it was indeed noted that rainfall was enough for a good grain yield, with P/ET lower than 1.00 only outside the crop growing seasons. The combination of MODIS images and weather stations proved to be useful for monitoring vegetation and water parameters, which can contribute to the sustainability of the agro-ecosystems exploration in Mato Grosso state, avoiding water scarcity in the near future.