José Alves Júnior

Propriedades físico-hídricas em Latossolo do Cerrado sob diferentes sistemas de manejo

The objective of this study was to evaluate the physico-hydric soil properties under different management systems in comparison with the native Cerrado, in Santo Antonio de Goias, Goias State, in areas cultivated since 1993. The evaluated systems in the depths of 0 - 0.10 and 0.10 - 0.20 m were: system S1 (soybean/bean/rice/pearl millet /bean), system S2 (soybean/pearl millet/corn), system S3 (corn + Brachiaria brizantha in integrated crop-livestock system) and system S4 (native cerrado). To compare the results obtained in the several soil management systems, the interval of confidence was used, at a probability level of 5%. The use of area under Brachiaria brizantha pasture for animal grazing caused compaction of the soil in the surface layer, verified through the reduction of the macroporosity, and increase of the microporosity and soil bulk density.

Spatial analysis of the influence of meteorological elements on the reference evapotranspiration in the State of Minas Gerais, Brazil

In general the methodologies most used and recommended to estimate crop water requirements are based on meteorological data. The aim of this study was to evaluate the effect of some meteorological elements on reference evapotrasnpiration (ET0) estimate in Minas Gerais State, Brazil. The values of ET0 were estimated daily by the Penman-Monteith-FAO method, using daily data over a period of 17 years. The influence of each meteorological element on ET0 values was determined by sensitivity tests and interpolated map analysis for each element under study. The results showed that the reference evapotranspiration is very variable in Minas Gerais, with annual average values between 2.51 to 4.59 mm d-1. The sensitivity analysis showed a high variation effect of meteorological elements in ET0 in Minas Gerais, with high sensitivity to vapor pressure deficit, wind speed and radiation. The radiation was the most important meteorological element, with the highest influence in ET0.

Eficiência de métodos para o cálculo de coeficientes do tanque classe A na estimativa da evapotranspiração de referência

The class A pan coefficients (Kp) can be determined with several methods, most based on wind speed, relative humidity and conditions and extension of the border which circles the pan. This study aimed at evaluating the performance of methods used for estimating the Kp, as well as an average and constant Kp (0.70), to evaluate the reference evapotranspiration (ET 0 ) under Brazilian Savannah conditions, in Santo Antonio de Goias, Goias State, Brazil. The methods were assessed on an annual basis and during the dry and rainy seasons. The ET 0 resulting from the class A pan evaporation, multiplied by the Kp values estimated with the aid of the Doorenbos & Pruitt (1977), Cuenca (1989), Snyder (1992), Pereira et al. (1995) and Allen et al. (1998) methods, were compared with the ET 0 estimated by using the Penman-Montheit equation. The coefficients of determination (r 2 ), correlation (r), Willmott index of agreement (d) and performance (c), as well as the mean and maximum absolute errors, were also estimated. Considering the weather conditions during the experiment, the best Kp method to estimate the annual ET 0 was the one proposed by Pereira et al. (1995). For the dry season, the method proposed by Cuenca (1989) performed better, while, for the rainy season, all methods showed a low performance, with the Pereira et al. (1995) method being the most efficient one. The use of a constant Kp of 0.70 resulted in a good performance and showed to be a practical option, however, it is necessary to determine it where it will be applied.

Citrus root distribution under water stress grown in sandy soil of central Florida

O experimento foi conduzido na Universidade da Florida (Centro de Ensino e Pesquisa em Citrus), em Lake Alfred, Polk County, Florida-EUA. O objetivo deste estudo foi avaliar os efeitos do estresse hidrico na distribuicao de raizes de laranjeira Valencia enxertada em citrumelo Swingle, em um pomar de 11 anos de implantacao. Tres tratamentos foram aplicados: 1) plantas irrigadas por microaspersao no periodo seco (Nov-Mar); 2) plantas nao irrigadas no periodo seco, e 3) plantas nao irrigadas no periodo seco e tambem sem chuva no periodo umido. As plantas do tratamento 3 nao receberam chuva durante o periodo umido, e os tratamentos 1 e 2 receberam chuva normalmente durantes 3 anos consecutivos (2003-2006). A irrigacao normal foi recomecada em todos os tratamentos, em meados de marco. Amostras de raizes foram coletadas utilizando um trado de boca (0,09 m de diâmetro e 0,25 m de altura) nos dois lados da linha de plantio, em 3 distâncias horizontais do tronco da planta (1, 2 e 3 m) e 4 profundidades (0,0-0,15; 0,15-0,30; 0,3-0,60 e 0,6-0,9 m). Os resultados mostraram que uma significante diferenca na distribuicao de raizes entre as plantas irrigadas e nao irrigadas.

AFRICAN MAHOGANY SUBMITTED TO DRIP IRRIGATION AND FERTILIZATION

1 Received on 22.01.2015 accepted for publication on 11.11.2016. 2 Universidade Federal de Goiás, Escola de Agronomia, Goiânia, GO Brasil. E-mail: <jose.junior@pesquisador.cnpq.br>. 3 Universidade Federal de Goiás, mestre em Agronomia, Goiânia, Goiás Brasil. E-mail: <luishantunes@hotmail.com> and <flaviodeoliveirarosa@gmail.com>. 4 Universidade Federal de Goiás, Escola de Agronomia, Goiânia, GO Brasil. E-mail<awpego@pesquisador.cnpq.br>. 5 Universidade Federal do Recôncavo da Bahia, Centro de Ciências Agrárias, Ambientais e Biológicas, Cruz das Almas, BA Brasil. E-mail: <lucasvellame@gmail.com>. *Corresponding author.