Adriano Marlisom Leão de Sousa

Albedo da cultura da soja em área de avanço da fronteira agrícola na Amazônia

O avanco da fronteira agricola na Amazonia pode acarretar graves impactos ambientais, constituindo a mudanca no albedo da superficie um dos principais forcantes. Avaliou-se, neste trabalho, o albedo da soja (Glycine Max (L.) Merryl), plantada em condicoes naturais de campo, na cidade de Paragominas, PA, regiao com grande avanco da fronteira agricola na Amazonia, e se observou relacao direta entre o albedo da soja e o seu indice de area foliar, valor maximo diario variando entre 0,24 e 0,25 associado a um IAF de 7,17 correspondente a 1297,62 graus-dia acumulados. Em termos medios, encontrou-se que a o estadio fenologico mais critico da cultura, tendo como base a mudanca no albedo, e o estadio fenologico de frutificacao na qual a mesma apresenta um albedo medio maximo de 23,3% (± 0,0007). Modelos empiricos foram ajustados para simular a variacao diaria do albedo em funcao do IAF e umidade do solo, ao longo do ciclo, e a variacao diurna do albedo na elevacao solar, para cada estadio fenologico da soja.

IMPACTS OF SOYABEAN EXPANSION ON THE AMAZON ENERGY BALANCE: A CASE STUDY

SUMMARY A micrometeorological experiment was carried out in an area of soyabean cultivation located in northeastern Para state, Brazil, in order to evaluate impacts on the local energy balance due to replacement of forests by soyabean. The meteorological data from forest ecosystems were collected in Caxiuana forests located in central Para. The energy balance components were obtained using the Bowen ratio technique. Differences in energy balance components between ecosystems were significant during the soyabean growing season and more significant between growing seasons. During the soyabean growing season mean impacts of −15%, −9% and −27% on net radiation, latent heat flux (LE) and sensible heat flux (H), respectively, were observed. At specific soyabean stages, LE was higher than in the forest because of the high soyabean surface conductance of water vapour. However, during the production off-season the impacts were more significant (p < 0.05), showing a reduction of 78% in LE and a substantial increase in H (84%) because of the absence of vegetation cover over this period.

Simulation of soybean growth and yield under northeastern Amazon climatic conditions

The objective of this work was to parameterize, calibrate, and validate a new version of the soybean growth and yield model developed by Sinclair, under natural field conditions in northeastern Amazon. The meteorological data and the values of soybean growth and leaf area were obtained from an agrometeorological experiment carried out in Paragominas, PA, Brazil, from 2006 to 2009. The climatic conditions during the experiment were very distinct, with a slight reduction in rainfall in 2007, due to the El Nino phenomenon. There was a reduction in the leaf area index (LAI) and in biomass production during this year, which was reproduced by the model. The simulation of the LAI had root mean square error (RMSE) of 0.55 to 0.82 m2 m-2, from 2006 to 2009. The simulation of soybean yield for independent data showed a RMSE of 198 kg ha-1, i.e., an overestimation of 3%. The model was calibrated and validated for Amazonian climatic conditions, and can contribute positively to the improvement of the simulations of the impacts of land use change in the Amazon region. The modified version of the Sinclair model is able to adequately simulate leaf area formation, total biomass, and soybean yield, under northeastern Amazon climatic conditions.

Diurnal Energy Balance in a Mango Orchard in the Northeast of Pará, Brazil

This study aimed to evaluate the diurnal energy balance during the reproductive stage of two growing seasons of a mango orchard in the northeast of Pará, Brazil. Therefore, a micrometeorological tower was installed and instrumented, in the center of the experimental area, to monitor meteorological variables, besides the phenological evaluation of the mango orchard, which was carried out during growing seasons of 2010-2011 (October 2010 to January 2011) and of 2011-2012 (September 2011 to January 2012). The energy balance was obtained by the bowen ration technique, and the available energy partitioned into heat flux to the ground, sensible heat and latent heat. The amount of rainfall was crucial to the partition of the net radiation in the energy balance components. It provided the variation in the consumption of available energy between 69% and 78% as latent heat flux, and between 23% and 32% as sensible heat flux. The heat flux to the ground was small, representing less than 1% of the net radiation, showing that the mango orchard exhibits good soil cover preventing large variations in soil heating.

PRODUÇÃO DE ÁREA FOLIAR E BIOMASSA E PRODUTIVIDADE DO FEIJÃO-CAUPI SOB REGIMES HÍDRICOS EM CASTANHAL, PARÁ

This work evaluated the effect of soil water availability on growth and productivity variables of cowpea in northeastern Pará, Brazil. The experiment was carried out in a field of 2,100 m at the experimental site of the Federal Rural University of Amazon, during the driest season of the years 2011, 2012 and 2013, in a completely randomised design with two treatments (irrigated and non-irrigated), both with 12 replications in the reproductive phase (2012 and 2013). Growth and productivity data were submitted to analysis of variance with two variation factors (water regime and experimental year) at 5% probability. Students t-test at 5% probability was used in the means of the stomatal conductance data, since this was monitored only in 2012. Final biomass production presented a reduction of 54.3% in 2012 and 26.4% in 2013 as a result of water deficit (DEF) of 76 and 26 mm, respectively. Mean stomatal conductance was reduced by 73% in the grain-filling stage as a result of the lower water availability during this period. Average cowpea productivity under water deficit reached 1,257 kg ha in 2012 and 1,396 kg ha in 2013. The reduction in water supply over the reproductive period significantly decreased production by 72 and 41% (F test, p < 0.05) in 2012 and 2013, respectively. An accumulated water deficit during the reproductive phase caused a maximum LAI reduction of 47% in 2012 (DEF of 76 mm) and of 13% in 2013 (DEF of 26 mm).

WATER REQUIREMENT ESTIMATE FOR THE REPRODUCTIVE PERIOD OF MANGO ORCHADS IN THE NORTHEAST OF THE STATE OF PARÁ, BRAZIL

O objetivo deste trabalho foi estimar o consumo hidrico em pomar de mangueiras durante as suas fases fenologicas, na regiao nordeste do Estado do Para. Para isso, foi instalada e instrumentada uma torre micrometeorologica em um pomar de mangueiras cv. Tommy Atkins de 22 anos de idade, com os dados coletados durante o periodo reprodutivo das safras de 2010/2011, e de 2011/2012. A evapotranspiracao atual de cultura foi estimada pelo balanco de energia atraves da tecnica da razao de Bowen. As safras ocorreram em condicoes meteorologicas distintas, com menor quantidade de chuva na safra 2, tendo como consequencia diferencas significativas na razao de Bowen. A evapotranspiracao tambem sofreu influencia das condicoes meteorologicas ocorridas no periodo. A evapotranspiracao atual da cultura variou entre 402,9 e 420 mm, apresentando um consumo medio diario de 3,8 mm na fase floracao, de 4,25 mm na fase de queda, de 3,56 mm na fase formacao, de 3,0 mm na fase de maturacao e de 3,73 mm para toda a fase reprodutiva.

Episode of Low Level Jets in the north and northeast coast of state of Para: a case study of 2002 april 21st to 22nd

Neste estudo descreve-se as caracteristicas da estrutura vertical de um episodio de Jatos de Baixos Niveis (JBN) ocorrido no litoral do Para, utilizando-se para tal, dados das radiossondagens de Ajuruteua, Municipio de Braganca coletados durante o experimento DESMATA (Impacto do Desmatamento Junto ao Litoral Atlântico da Amazonia) realizado no periodo de 08 a 22 de abril de 2002. Dentre os casos detectados no periodo chuvoso, selecionou-se um que se manteve por 12 horas com velocidade media de 15m/s e que estava direcionado de Nordeste para Leste, no ponto de maxima velocidade. Os resultados observacionais indicaram que, este JBN localizado no litoral Paraense foi resultado da acao combinada de dois fatores: (1) oscilacao inercial e (2) baroclinia superficial. Estes dois fatores combinados sustentaram este JBN com intensidades entre 10 e 13m/s durante o dia e entre 14 e 16m/s durante a noite, localizado a uma altitude media de 800m acima da superficie.