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Neste trabalho, teve-se como objetivo apresentar duas estratégias de gerenciamento de lâminas de irrigação de precisão a partir da análise dos atributos físico-hidráulicos do solo e da evapotranspiração da cultura do milho de uma área agrícola localizada no município de Sorriso-MT. Os atributos físicos do solo têm grande importância para o dimensionamento e manejo dos sistemas de irrigação, em projetos onde se busca eficiência e adequada operação. Os atributos analisados da área foram: textura, densidade do solo e das partículas, porosidade total e de aeração, carbono, condutividade hidráulica e retenção de água no solo. Por meio dos resultados foram recomendados quatro mapas temáticos de lâminas de irrigação de precisão, sendo um a partir da variabilidade espacial (v.e.) da capacidade de água disponível (CAD), outro a partir da v.e. da água facilmente disponível (AFD) e os dois últimos a partir da correlação positiva dos mapas de classes dos atributos físico-hidráulicos do solo com os mapas de CAD e AFD. Palavras-chave: geoestatística; capacidade de água disponível; zona de manejo CERESOLI, L. L.; SOBENKO, L. R.; SILVA, B. K.; ARMINDO, R. A. SPATIAL VARIABILITY OF SOIL HYDRAULIC PROPERTIES AND IRRIGATION PRECISION DEPTH DETERMINATION ABSTRACTThis study aimed to present two strategies for managing irrigation precision. These strategies were based on hydraulic soil physical attributes and on corn evapotranspiration. The study was conducted an agricultural area located in Sorriso city, Mato Grosso state, Brazil. Texture, bulk and particle densities, porosity and air-filled porosity, carbon, hydraulic conductivity and water retention were analyzed in this area. By the results, four thematic maps of irrigation precision were recommended, one from the spatial variability (s.v.) of the available water capacity (AWC), another from readily water range s.v. (RAW) and the last two between the positive correlation of physical attributes maps and of AWC and RAW maps.

Venturi injectors are commonly employed for fertigation purposes in agriculture, in which they draw fertilizer from a tank into the irrigation pipeline. The knowledge of the amount of liquid injected by this device is used to ensure an adequate fertigation operation and management. The objectives of this research were (1) to carry out functional tests of Venturi injectors following requirements stated by ISO 15873; and (2) to model the injection rate using dimensional analysis by the Buckingham Pi theorem. Four models of Venturi injectors were submitted to functional tests using clean water as motive and injected fluid. A general model for predicting injection flow rate was proposed and validated. In this model, the injection flow rate depends on the fluid properties, operating hydraulic conditions and geometrical characteristics of the Venturi injector. Another model for estimating motive flow rate as a function of inlet pressure and differential pressure was adjusted and validated for each size of Venturi injector. Finally, an example of an application was presented. The Venturi injector size was selected to fulfill the requirements of the application and the operating conditions were estimated using the proposed models.

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SUMMARYDue to the lack of basic information on water required by maize (Zea mays L.) in Brazil, the large amount of water applied usually exceeds crop requirements, wasting water and energy. In this study, we measured crop evapotranspiration (ETc) as evaporative heat flux from a centre pivot-irrigated maize plantation in Southern Brazil during winter and summer seasons, using the Bowen ratio method to evaluate how the degree of canopy-atmosphere coupling affects crop water needs and irrigation management. Irrigation requirements were determined by comparing ETc with reference evapotranspiration (ETo), derived from the Penman–Monteith equation and expressed as the ETc/ETo (Kc) ratio. In this study, the average Kc values obtained were 1.31 and 0.90 for the winter and summer, respectively. Using aerodynamic and canopy resistance measurements, the decoupling factor (Ω) was computed. Ω values tending to zero (0.09 and 0.20 for winter and summer, respectively) showed that strong coupling of maize plants to the atmosphere and sensitivity to high air temperatures, vapour pressure deficits and wind speed caused variations in Kc in relation to ETo ranges. During the experimental period, the Kc value ranged from 0.92 when the ETo exceeded 4 mm d−1 to 1.64 when the ETo was less than 2 mm d−1.

RESUMO -O milho "safrinha" é considerado uma cultura de alto risco devido à baixa disponibilidade hídrica no período em que é cultivado. Assim, o objetivo deste trabalho foi verificar o desempenho de dois modelos de estimativa de evapotranspiração de referência (ETo), visando realizar o manejo da irrigação, via balanço hídrico, em três cenários com índices pluviométricos distintos no município de Sorriso-MT. O estudo foi realizado para uma área de 9,3 ha, utilizando-se dados climatológicos diários dos anos considerados médio, seco e úmido para estimativa da ETo pelos modelos de Hargreaves-Samani e Priestley-Taylor. Realizou-se o balanço hídrico para a cultura em sistema de irrigação por aspersão convencional com turno de rega fixo de três dias. Consideraram-se os coeficientes de correlação (r), determinação (r 2 ), concordância de Willmott (d), desempenho (c) e estimativa do erro padrão (EEP) avaliando os modelos comparando-os com os valores estimados pelo método de Penman-Monteith (PM). Os modelos estudados apresentaram desempenhos "ótimo" e "muito bom" para os três cenários, porém não se mostraram sustentáveis. Geraram-se equações para validar o uso dos modelos estudados para as lâminas que superestimaram PM. O cenário seco apresentou a maior lâmina total (irrigação e precipitação efetiva), enquanto que o chuvoso demandou menores lâminas de irrigação. Palavras-chave: balanço hídrico, evapotranspiração, simulação, aspersão, Zea mays L. ESTIMATION OF FERTILIZATION REQUIREMENTS IN THE OFF-SEASON MAIZE THROUGH AGROCLIMATOLOGICAL METHODSABSTRACT -Off-season maize is considered a high-risk culture due to the low water availability in the growth period. The objective of this study was to evaluate the performance of two reference evapotranspiration (ETo) estimation models, in order to carry out irrigation management by water balance, in three scenarios with different rainfall in Sorriso-MT. The study was conducted in an area of 9.3 ha, using daily climatological data for the years considered medium, dry and wet to estimate the ETo by the models of Hargreaves-Samani and Priestley-Taylor. The water balance was made for crop grown under conventional sprinkler irrigation system with fixed irrigation interval of three days.To evaluate the performance, models were considered: the correlation (r) and determination (r²) coefficients, Willmott agreement (d), performance (c) and standard error estimate (EEP), taking Penman-Monteith (PM) as reference. The studied models presented performances classified as "great" and "very good" for the three scenarios, but they aren't sustainable as the correct use of water. Equations were generated to validate the use of the studied models for the water depths that overestimated the PM values. The dry year demanded greater total water depths (irrigation and effective precipitation), while the rainy year demanded lower irrigation depths. Keywords: water balance, evapotranspiration, simulation, sprinkler irrigation, Zea mays L. Sorgo, v.15, n.3, p. 543-556, 2016 RESUMO -O milho "safrinha" é...