Variabilidade espacial e temporal do potencial mátrico da água em terra roxa estruturada

Pacheco, F B P; Reichardt, Klaus; Tuon, Robinson Luís; Bacchi, Osny Oliveira Santos; Villagra, M. M.

doi:10.1590/s0103-90161994000200020

Cited by 4 publications

(5 citation statements)

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“…Os gradientes de potencial total medidos com ∆z de 0,30 e 0,20 m estão dentro da faixa de grandeza de outros estudos, como o de Pacheco et al (1994), que utilizaram ∆z semelhantes a esses. A princípio, a medida do gradiente de potencial total com ∆z menor é mais real, uma vez que a proporcionalidade entre a diferença de potencial total e o ∆z não se mantém constante, principalmente em solos heterogêneos ou solos com camadas compactadas.…”

Section: Resultsunclassified

Variação diurno-noturna do potencial mátrico e gradiente de potencial total da água no solo

Brito

Libardi

Mota

et al. 2014

Rev. Bras. Ciênc. Solo

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RESUMOO potencial mátrico em solos não saturados é um importante componente do potencial total e, portanto, deve ser medido da melhor forma possível. Este trabalho teve por objetivo avaliar a influência da temperatura do solo sobre o potencial mátrico e o gradiente de potencial total, durante a redistribuição da água num Latossolo Vermelho-Amarelo, em Piracicaba, SP, a partir de dados coletados por tensiometria. Em uma parcela circular de 3 m de diâmetro, foram instalados 10 tensiômetros com transdutor de tensão, modelo SWT3 da Delta-T, nas profundidades de 0,10; 0,15; 0,20; 0,25; 0,30; 0,35; 0,40; 0,45; 0,50; e 0,55 m, com os quais foram obtidos os potenciais mátricos para essas profundidades e o gradiente de potencial total, (∆φ ∆φ ∆φ ∆φ ∆φm/∆ ∆ ∆ ∆ ∆z)+1, para a profundidade de 0,25 m, com ∆ ∆ ∆ ∆ ∆z de 0,1; 0,2; e 0,3 m, utilizando os tensiômetros instalados nas profundidades de 0,20 e 0,30; 0,15 e 0,35; e 0,10 e 0,40 m para ∆φ ∆φ ∆φ ∆φ ∆φm, respectivamente. Na mesma parcela, foram também instalados termopares tipo T na superfície e nas profundidades 0,025; 0,050; e 0,075 m de solo. Ambas as leituras dos tensiômetros e termopares foram armazenadas em um Datalogger, Modelo DL2, da Delta-T, a idênticos intervalos de tempo. As avaliações detectaram oscilações na leitura do potencial mátrico da água no solo ao longo do dia e nos efeitos diferenciados nos tensiômetros instalados em profundidades diferentes, ocasionando oscilações também no gradiente de potencial total da água no solo. Os melhores horários para a realização das leituras dos tensiômetros são nas primeiras sete horas do dia ou após às 18 h.Termos de indexação: temperatura do solo, transdutor de tensão, tensiômetro.

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Section: Resultsunclassified

Variação diurno-noturna do potencial mátrico e gradiente de potencial total da água no solo

Brito

Libardi

Mota

et al. 2014

Rev. Bras. Ciênc. Solo

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“…found a large y m variability across a 0.15-ha trickle-irrigated chili pepper field and concluded that seven tensiometers were required to yield a fairly accurate mean of y m . Yeh et al (1986) observed that y m measured along a 290-m transect in New Mexico was spatially autocorrelated across distances of at least 6 m. However, no spatial dependence was detected when Pacheco et al (1994) analyzed the spatial variability of y m along a 125-m transect of a dark red latosol using either autocorrelogram or semivariogram analysis. These findings are of great value for irrigation scheduling, solute transport modeling, as well as other hydrological considerations and agricultural management (Ciollaro et al, 1990;Grayson and Western, 1998;Hupet and Vanclooster, 2002).…”

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confidence: 83%

Temporal Dynamics and Stability of Spatial Soil Matric Potential in Two Land Use Systems

Yang

Wendroth

Walton

2016

Vadose Zone Journal

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Core Ideas The spatial variance of ψm at the 10‐cm soil depth decreased with median ψm. Weekly precipitation and ψm had common temporal periodicities. The response of ψm to precipitation was faster and more common in cropland. Wavelet analysis revealed two different behaviors of water infiltration. The ψm spatial pattern was more related to elevation than soil texture in grassland. The spatial variability of the soil water status and its temporal behavior are essential for hydrological modeling and agricultural management. Changes in atmospheric conditions such as precipitation usually cause large temporal dynamics in the soil water status, whereas inherent soil properties such as soil texture and topography maintain their spatial pattern with time. Our objective was to identify the relevant spatial and temporal processes underlying soil water behavior. Along a 48‐ by 3‐m transect evenly distributed across two land use systems, i.e., cropland and grassland, the soil matric potential (ψm) was measured on a weekly basis from May to October 2013 at 1‐m intervals and at depths of 10, 30, 50, 70, 90, and 110 cm. The spatial variance of ψm at the 10‐cm depth decreased with weekly precipitation and the spatial median of ψm in both land use systems, owing to the enhancement of lateral water redistribution by elevated soil wetness. Temporal dynamics in ψm and its spatial variance diminished with soil depth. In contrast, the temporal stability of ψm generally increased with soil depth because of the decreasing impact exerted by precipitation. According to Spearman's rank correlation coefficients, the relative distribution of ψm in space was more strongly correlated with relative elevation than with soil texture in the grassland. These results have direct implications for irrigation management.

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“…Devido à dificuldade de medição na maioria das vezes a histerese precisa ser desconsiderada. Pacheco et al (1994) trabalharam em terra roxa estruturada em Piracicaba/SP com o objetivo de melhorar a caracterização das variabilidades temporal e espacial do potencial mátrico da água no solo. Os autores utilizaram tensiômetros de coluna de mercúrio para a determinação desse potencial e concluíram que, para obter um valor médio dentro de 10% do valor esperado, cinco pontos de medição são suficientes.…”

Section: Limitações De Uso Do Tensiômetrounclassified

“…A variabilidade no arranjo poroso de solos leva a diferentes condições de retenção de água e, conseqüentemente à variações da tensão (PACHECO et al, 1994). Há na literatura alguns trabalhos onde os autores comentam sobre essa característica.…”

Section: Tensiometria No Manejo Da Irrigaçãounclassified

“…Villagra et al (1988), trabalhando com tensiômetros instalados na zona arável do solo sob pivô central, apresentaram resultados detalhados sobre esta variabilidade e concluem que ela é fator importante, não podendo ser desprezada tanto em experimentação científica como em seu uso para manejo dos solos. Da mesma forma Pacheco et al (1994), estudando a variabilidade espacial e temporal do potencial mátrico da água em terra roxa estruturada na região de Piracicaba, com o uso de tensiômetros, concluíram que a medida do potencial matricial, neste tipo de solo, feita com tensiômetros, em camadas profundas do solo, tem coeficientes de variação da ordem de 5 % a 12 %, sendo tanto menor quanto mais seco o solo. Silva et al (2003) compararam o manejo da irrigação feito com lisímetro poroso e tensiometria na produção do melão rendilhado.…”

Section: Tensiometria No Manejo Da Irrigaçãounclassified

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Desenvolvimento de um sistema automático para irrigação de precisão em pivô central

Queiróz¹

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Development of an automatic system for precision irrigation with center pivot In order to developed an automation system so as to provide precision irrigation through center pivot equipment, softwares and hardwares were built at the Escola Superior de Agricultura "Luiz de Queiroz", University of Sao Paulo-ESALQ/USP, within the Piracicaba campus. This project was carried out in two stages, the one performed in Piracicaba, state of Sao Paulo, in which the system was developed, built and tested, and the second one in Barra do Bugres, state of Mato Grosso (MT), in which a laboratory experiment was performed to verify the operation. The evaluations were carried out in laboratory, except the radio range test. An apparatus to simulate a center pivot operation was built. Along the experiment, one used radio-frequency operating on 315 MHz and 433.9 MHz, liquid crystal displays, integrated circuits, discrete electronic components, connectors, cables and wires, material and tools for handmade printed circuit boards and a microcomputer. Along the entire work 12 circuits (hardwares) were developed, with 10 for computer interface and 2 to drive and transmit the tensiometer data. All circuits were tested both individually and grouped. At the end, all 10 computer interface circuits were grouped into a single printed circuit board, which was used in simulations in Barra do Bugres, MT. Six softwares were developed, three of which for the computer and three for the microcontrollers used. For computer software development one used Borland's Delphi 3, while the Basic Step softwares were developed in TBasic. No failures were detected in any of the softwares developed for the microcontrollers. The software developed for the computer was named PivoRF and presents three versions: user, administrator and monitoring. The user version is the more robust and destined for direct field application. The administrator version has the sole function of generating data files for the administrator version input; as for the monitoring version, it continually monitors a given irrigation section, and its application is more suitable for research. Tests were carried out to evaluate radio range, data transmission efficiency and center pivot control capacity. The results revealed that the radio-frequency moduli have short range and are not suited for real application in center pivot systems. Evaluated at below 50-meter distances the system proved to be efficient for data transmission with no failures. The user version was exhaustively tested, and operated adequately in over 300 tests. Based on the results, one verifies that the technology developed has a great potential for practical use, thus making irrigation management easier. However, radio-frequency moduli with higher range than those used are required, and those can be easily found in the market today.

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Variabilidade espacial e temporal do potencial mátrico da água em terra roxa estruturada

Cited by 4 publications

References 3 publications

Variação diurno-noturna do potencial mátrico e gradiente de potencial total da água no solo

Variação diurno-noturna do potencial mátrico e gradiente de potencial total da água no solo

Temporal Dynamics and Stability of Spatial Soil Matric Potential in Two Land Use Systems

Desenvolvimento de um sistema automático para irrigação de precisão em pivô central

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