Antônio Heriberto de Castro Teixeira

Determining Regional Actual Evapotranspiration of Irrigated Crops and Natural Vegetation in the São Francisco River Basin (Brazil) Using Remote Sensing and Penman-Monteith Equation

Abstract: To achieve sustainable development and to ensure water availability in hydrological basins, water managers need tools to determine the actual evapotranspiration (ET) on a large scale. Field energy balances from irrigated and natural ecosystems together with a net of agro-meteorological stations were used to develop two models for ET quantification at basin scale, based on the Penman-Monteith equation. The first model (PM1) uses the resistances to the latent heat fluxes estimated from satellite measurements, while the second one (PM2) is based on the ratio of ET to the reference evapotranspiration (ET 0 ) and its relation to remote sensing parameters. The models were applied in the Low-Middle Sao Francisco river basin in Brazil and, after comparison against field results, showed good agreements with PM1 and PM2 explaining, respectively, 79% and 89% of the variances and mean square errors (RMSE) of 0.44 and 0.34 mm d −1 . Even though the PM1 model was not chosen for ET calculations, the equation for surface resistance (r

Large-Scale Water Productivity Assessments with MODIS Images in a Changing Semi-Arid Environment: A Brazilian Case Study

In the Brazilian semi-arid region, the intensification of agriculture results in a change of natural vegetation by irrigated crops. To quantify the contrast between these two ecosystems, the large-scale values of water productivity components were modelled in Petrolina (PE) and Juazeiro (BA) municipalities. The SAFER (Simple Algorithm For Evapotranspiration Retrieving) algorithm was used to acquire evapotranspiration (ET), while the Monteiths radiation model was applied for estimating the biomass production (BIO). Moderate Resolution Imaging Spectroradiometer (MODIS) satellite images were used together with agro-meteorological data. In Petrolina and Juazeiro, the mean monthly ET values for irrigated crops were 938 and 739 mm∙month−1, with the corresponding ones for natural vegetation of 385 and 194 mm∙month−1.Water productivity (WP) was analysed by the ratio of BIO to ET, defined here as the ratio of the net benefits from the mixed agricultural systems to the amount of water required for producing those benefits. The highest incremental WP values, as a result of the irrigated crops introduction, happened outside the rainy period. More spatial WP uniformity occurred in natural vegetation, when comparing with irrigated crops. The most frequent WP values in Petrolina were between 1.6 and 2.2 kg∙m−3 while in Juazeiro this range was from 1.0 to 1.6 kg∙m−3. The differences between the municipalities can be mainly explained by differences in precipitation and soil water storages conditions, promoting better rainfall use efficiency by the natural vegetation in the first one. The results of the current research are important for appraising the land use change impacts in situations of expanding irrigation areas.

Avaliação dos componentes do balanço de energia durante o primeiro ano de cultura da banana

Dados de saldo de radiacao, fluxo de calor no solo, gradientes de temperatura e pressao do vapor, coletados no Campo Experimental da Embrapa Semi-Arido, em Petrolina, PE, foram utilizados na avaliacao dos comportamentos diurno e sazonal dos componentes do balanco de energia, durante as fases fenologicas da cultura da banana, irrigada por microaspersao, no primeiro ano de producao. Em media, o saldo de radiacao representou 63% da radiacao solar global. A razao de Bowen foi utilizada na medicao dos fluxos de calor latente e de calor sensivel. A maior porcao do saldo de radiacao foi usada como fluxo de calor latente (87%) seguido pelo fluxo de calor no solo (11%) e pelo fluxo de calor sensivel (2%). O baixo percentual do saldo de radiacao usado como fluxo de calor sensivel deve ser devido a adveccao de umidade para a cultura proveniente do Rio Sao Francisco.

Guidelines for irrigation scheduling of banana crop in São Francisco Valley, Brazil . II - Water consumption, crop coefficient, and physiologycal behavior

The water consumption and the crop coefficient of the banana cv. Pacovan were estimated in Petrolina County, northeastern Brazil, in order to establish guidelines to irrigation water management. Evaluations were carried out since planting in January 1999 to the 3rd harvest in September 2001 on a microsprinkler irrigated orchard, with plants spaced in a 3 x 3 m grid. Average daily water consumption was 3.9, 4.0, and 3.3 mm in the 1st, 2nd and 3rd growing seasons, respectively. Crop coefficient values increased from 0.7 (vegetative growth) to 1.1 (flowering). Even with high soil water availability, transpiration was reduced due to high evaporative demand.

Aptidão agroclimática da cultura da videira no Estado da Bahia, Brasil

The use of agroclimatic indexes based on water balance and air temperature means, allowed the characterization of areas with different aptitude for grape (Vitis vinifera L.) crop growth in Bahia State, Brazil. Thornthwaite and Mather (1955) water balance for 120 mm soil moisture capacity, of the regions of natural dispersion and of areas of commercial crop production was used to determine the annual hydric index of Thornthwaite (Ih) in the characterization of ideal hydric conditions of climate for the crop growth. Monthly climatic values of temperature and rainfall were used to obtain the water balance for the same soil moisture capacity for 408 locations of Bahia State. It was observed that the State has no thermal limitation for the grape growth, being higher contents of sugar obtained in the regions with higher mean summer temperatures. So, the zones of full aptitude were subdivided according to the highest monthly value of temperature (Tq) of each place. The combination of thermal and hydric zones resulted in four classes of agroclimatic aptitude.

Application of Landsat images for quantifying the energy balance under conditions of land use changes in the semi-arid region of Brazil

In the Nilo Coelho irrigation scheme, Brazil, the natural vegetation has been replaced by irrigated agriculture, bringing importance for the quantification of the effects on the energy exchanges between the mixed vegetated surfaces and the low atmosphere. Landsat satellite images and agro-meteorological stations from 1992 to 2011 were used together, for modelling these exchanges. Surface albedo (α0), NDVI and surface temperature (T0) were the basic remote sensing parameters necessary to calculate the latent heat flux (λE) and the surface resistance to evapotranspiration (rs) at the large scale. The daily net radiation (Rn) was retrieved from α0, air temperature (Ta) and transmissivity (τsw) throughout the slob equation, allowing the quantification of the daily sensible heat flux (H) by residual in the energy balance equation. With a threshold value for rs, it was possible to separate the energy fluxes from crops and natural vegetation. The averaged fractions of Rn partitioned as H and λE, were in average 39 and 67%, respectively. It was observed an increase of the energy used in the evapotranspiration process inside irrigated areas from 51% in 1992 to 80% in 2011, with the ratio λE/Rn presenting an increase of 3 % per year. The tools and models applied in the current research, can subsidize the monitoring of the coupled climate and land use changes effects in irrigation perimeters, being valuable when aiming the sustainability of the irrigated agriculture in the future, avoiding conflicts among different water users.

Energy balance with Landsat images in irrigated central pivots with corn crop in the São Paulo State, Brazil

The energy balance (EB) components were quantified in a commercial farm with corn crop, irrigated by central pivots, in the Northwestern side of São Paulo state, Southeast Brazil. The SAFER (Simple Algorithm For Evapotranspiration Retrieving) was applied to retrieve the latent heat flux (λE), considering six pivots, covering irrigated areas from 74 to 108 ha. With λE quantified and considering soil heat flux (G) as a fraction of net radiation (Rn), the sensible heat flux (H) was acquired as a residual in the energy balance equation. Seven Landsat satellite images, covering all corn crop stages from 23 April 2010 to 29 August 2010, allowed relating the energy balance components according to the accumulated degree-days (DDac) from the planting to harvest dates. The average Rn values ranging from 5.2 to 7.2 MJ m-2 day-1, represented 30 to 45% of global solar radiation (RG). Considering the variation of the energy balance components along the corn crop growing seasons, the average ranges for λE, H and G were respectively 0.0 to 6.4 MJ m-2 day-1, -1.5 to 6.7 MJ m-2 day-1 and 0.1 to 0.6 MJ m-2 day-1. The fraction of the available energy (Rn - G) used as λE was from 0.0 to 1.3 indicated a good irrigation management, insuring that the water deficit could not be the reason of any yield reduction. Although Rn did not reflected well the crop stages, its partition strongly depended on these stages. λE higher than Rn and the negative H/Rn, happening sometimes along the corn growing seasons, occurred after the vegetative growth and before the harvest times, indicated heat advection from the surrounding areas to the irrigation pivots, which represented an additional energy source for the evaporative process. The models applied here with only the visible and infrared bands of the Landsat sensor are very useful for the energy balance analyses, considering the size of the corn crop irrigation pivots in Southeast Brazil, when subsidizing a rational irrigation water application in corn crop.

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

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 Monteiths 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.

Delimitação da aptidão agroclimática para videira sob irrigação no Nordeste Brasileiro

Long term weather data were used together with simple regression models involving crop coefficient (Kc), reference evapotranspiration (ET0) and accumulated degree days (DDac) to quantify the vineyard water requirement (VWR) of table and wine grapes in the Brazilian Northeast. VWR joined with precipitation, allowed the development of a vineyard water indicator (VWI), which was applied together with average values of air temperature for a growing season to characterize the agro-climatic aptitude. For table grapes it was observed that the region has no thermal limitation, however higher both sugar contents and grape yield would be obtained in the areas with higher values of air temperature. In relation to wine grape, it was observed that there are some thermal limitations for the wine quality, depending on the pruning date, being higher the alcohol content and lower acidity, in wines elaborated under conditions with higher values of air temperature. In relation to table grapes, the best pruning dates are between June and September, being highlighted the west areas of Bahia, Pernambuco, Paraiba and almost all areas of Rio Grande do Norte, Ceara, Piaui and Maranhao. Considering wine grapes, the best agro-climatic aptitude is for pruning dates from May to June, with highlights for the states of Bahia, Pernambuco, Paraiba, Alagoas and Sergipe, and a southeast area of Maranhao state.

Large-scale radiation and energy balances with Landsat 8 images and agrometeorological data in the Brazilian semiarid region

Abstract. Aiming to subsidize the rational water resources management, four Landsat 8 (L8) images along different conditions of the year 2014 were used for modeling the radiation and energy balances in the mixed agroecosystems inside a Brazilian reference semiarid area. The SAFER algorithm was applied to calculate the latent heat flux (λE); net radiation (Rn) was acquired by the Slob equation; ground heat flux (G) was considered a fraction of Rn; and the sensible heat flux (H) was retrieved by residue in the energy balance equation. For classifying the vegetation, the surface resistance algorithm (SUREAL) was used to estimate the surface resistance to the water fluxes (rs) with threshold values for rs. Clearly, one could see higher λE values from irrigated crops (ICs) than those for natural vegetation (NV) with some situations of heat horizontal advection. The respective λE, H, and G average ratios to Rn for the ICs ecosystem were 64% to 79%, 18% to 28%, and 3%, respectively. For the NV ecosystem, the corresponding fractions were 4% to 37%, 60% to 94%, and 4%, respectively. The algorithms proved to have strong sensibility to quantifying the large-scale energy and mass exchanges by applying L8 images in mixed agroecosystems of semiarid environments.