Evaluating the Effect of Soil Texture on the Response of Three Types of Sensors Used to Monitor Soil Water Status

Abstract

Accurate monitoring of soil water status can be an important component of precision irrigation water management. A variety of commercial sensors measure soil water status by relating sensor electrical output to soil water content or soil water potential. However, sensor electrical output can also be affected by soil characteristics other than water content, such as soil texture, salinity, and temperature. This makes it difficult to accurately measure and interpret soil water status without prior on-site calibration. In this study, we investigated the impact of soil texture on the response of three types of sensors commonly used to monitor soil water status, including the Decagon EC-5, the Vegetronix VH400, and the Watermark 200ss granular matrix sensor. A replicated laboratory experiment was conducted to evaluate the response of these types of sensors using four major soil textural classes commonly found in South Carolina. We found that the three types of sensors had a significant response to changes in soil water content, but while the EC-5 and VH400 sensors had a linear response, the Watermark 200ss had a curvilinear response that was explained by an exponential decay function. The response of the three sensor types, however, was significantly affected by soil texture, which will significantly affect the trigger point used to initiate irrigation based on the output from these sensors. Therefore, it is suggested that guidelines on how to use these sensors for local soils need to be developed and made available to farmers, so that they can make better irrigation scheduling decisions.

Calibração do sensor capacitivo de umidade do solo EC-5 em resposta a granulometria do solo

“…O conhecimento e monitoramento do conteúdo de água no solo detém importante ferramenta para o fornecimento de informações destinadas a gestão da agricultura, como manejo da irrigação; estudos hidrológicos e calibração e validação de modelos de água no solo (PAYERO et al, 2017;PIZETTA et al, 2017). A determinação da umidade do solo pelo o método direto (método padrão) é considerado preciso e de baixo custo, entretanto é destrutivo e altamente trabalhoso, impossibilitando tomadas de decisões rápidas em campo (MATOS et al, 2017).…”

“…Em resposta a essas deficiências no monitoramento do solo o uso de sensores eletromagnéticos (método indireto) apresentam-se como uma alternativas viáveis, uma vez que estes podem fornecer e registrar valores atuais de conteúdo de água de forma não destrutiva e instantânea (GOMES et al, 2017;PIZETTA, 2017), levando a redução significativa do uso da água enquanto mantém ou aumenta os rendimentos da cultura (PEREIRA et al, 2018;GASCH et al, 2017).…”

“…Há estudos que mostram a importância da calibração de sensores de umidade e da confecção de curvas de calibração para cada tipo de solo, estrutura e profundidade, seja em condição de laboratório ou em campo (SOUZA et al, 2013;PARVIN e DÉGRE, 2015). E que essas calibrações possibilitaram o incremento da precisão do sensores na leitura do teor de água no solo (PEREIRA et al, 2018;PIZETTA, 2017;GOMES et al, 2017;GASCH et al, 2017;PAYERO et al, 2017).…”

An Arduino-Based Wireless Sensor Network for Soil Moisture Monitoring Using Decagon EC-5 Sensors

“…In this process, knowing the amount of water added to the soil was not critical, since the target was just to create a range of water contents among the four soil samples, and it was already known from previous work that the sensor's output was linearly related to changes in VWC [11]. The four sensors were first connected to the microcontroller and readings were taken by alternatively immersing each sensor into the appropriate media.…”

“…The EC-5 sensors were selected for this study because of their affordability and because they had been tested in previous lab and field studies and have been shown to have a fast response that linearly relates to VWC [11]. The EC-5 sensors measure VWC by measuring the dielectric constant of the media using capacitance/frequency domain technology [12].…”