Frederico Terra de Almeida

Estimativas da evapotranspiração de referência em diferentes condições de nebulosidade

The objective of this work was to evaluate the performance of reference evapotranspiration (ETo) estimation methods, in different cloudiness conditions, in Seropedica, RJ, Brazil. The ETo estimates were compared with daily measurements made on weighing lysimeter, between 6/1/2006 and 7/31/2007, by pooling the data or discretizing them according to the variance of daily clearness index (KT), in four classes: KT 0.65, open sky (Op). The mean absolute error (MBE), the square root of the mean square error (RMSE) and indexes of adjustment and performance were used as quality indicators of the different methods. In the pooled data, Penman-Monteith FAO (PMF) and Hargreaves-Samani (HS) methods had 84.05 and 79.52% performance indexes, respectively, while Jensen & Haise, Linacre and Makking methods had performances below 60%. Changes in the cloudiness conditions affected the performance of ETo estimation methods. The best results were obtained with the solar radiation (86.1%) and Camargo (81.8%) methods, under the Op and Clo conditions. The PMF and HS methods can be employed in a complementary way, since their performance were 78.4% (Clo and PCDi) and 77.6% (PCOp and Op), respectively.

Hydrologic modeling in a small watershed part I: improvement of the HidroBacia model

Testes preliminares realizados com o modelo hidrologico HidroBacia, indicaram desequilibrio no seu balanco de massa, despertando a necessidade de estudos visando ao seu aperfeicoamento; assim, o presente trabalho consistiu no aprimoramento do modelo HidroBacia a partir da localizacao e correcao de falhas no codigo-fonte do seu programa computacional, essas falhas foram identificadas atraves da depuracao do modelo durante simulacoes do hidrograma de escoamento superficial, utilizando-se dados de uma microbacia hidrografica experimental. A principal causa relacionada com o desequilibrio do balanco de massa do modelo, tinha referencia com a solucao das equacoes do modelo de ondas cinematicas usado na propagacao dos hidrogramas de escoamento superficial, cujo problema foi contornado pela substituicao do algoritmo linear utilizado, Bras (1990), pelo algoritmo nao-linear apresentado por Li et al. (1975). A partir desta modificacao, considerada principal, e outras modificacoes implementadas, o balanco de massa do modelo HidroBacia foi ajustado e suas simulacoes passaram a gerar estimativas coerentes. Em virtude das alteracoes efetuadas, o HidroBacia evoluiu da versao 1.0 para a versao 1.1.

QUALIDADE FÍSICO-QUÍMICA DE UM LATOSSOLO SOB SEMEADURA DIRETA E SUCESSÃO SOJA-MILHO NO ECÓTONO CERRADO/AMAZÔNIA

The soybean-corn succession in no-tillage system (DSS) is the most common cultivation practice in the state of Mato Grosso. Soils submitted to this type of system are prone to the formation of fertility gradients and surface compaction, restricting crop productivity. The objective of this work was to evaluate the physical-chemical attributes of an Oxisol after 11 years of continuous succession of soybean and corn in direct seeding, using geostatistical analysis techniques and main components. The experiment was conducted at the Chão Nativo farm located in the municipality of Sinop, Mato Grosso, Cerrado-Amazonian ecotone. For this, a rectangular mesh was installed with 103 sampling points distributed in an area of 7.02 ha, in which the grain yield of the soybean was determined as well as the physical and chemical attributes of the soil in the layers 0-10 and 0.10 – 0.20 m. Soybean showed a grain yield between 2.83 and 3.70 Mg ha, which was positively correlated with the spatial distribution of pH, phosphorus and potassium. The soil presented low physical quality due to high soil resistance to penetration and macroporosity less than 10%; however, no spatial correlation of physical attributes with soybean yield was observed.