Relação entre potássio na solução do solo, umidade e condutividade elétrica aparente do solo

Abstract

Precision agriculture that is based on the physical and chemical properties of soil requires a dense sampling to evaluate spatial variability in the field. This dense sampling is often expensive and time consuming. One technique to reduce the number of samples is to define management zones based on information that is collected in the field. Some researchers have demonstrated the importance of the electrical properties of soil in defining management zones. Thus, the objective of this study was to evaluate the relationship between the apparent soil electrical conductivity and soil properties in mountainous areas of coffee production. The electrical conductivity of soil was evaluated at soil depths ranging from 0.00-0.20 m (EC20) and 0.00-0.40 m (EC40) using a portable meter. The mean values of EC20 and EC40 were 1.80 mS m-1 and 1.22 mS m-1 , respectively. Both EC20 and EC40 exhibited comparatively low correlations with the soil properties, whereas higher correlations were obtained for measurements of remaining phosphorus, wherein values of 0.427 and 0.465, respectively, were obtained. RESUMO-A agricultura de precisão baseada nas propriedades físicas e químicas do solo exige uma amostragem densa para se determinar a variabilidade espacial no campo. Essa amostragem densa, muitas vezes apresenta custo e tempo consumido elevado. Uma das técnicas para reduzir o número de amostras é definir zonas de manejo em função de informações coletadas no campo. Alguns pesquisadores têm demonstrado a importância desempenhada pelas variáveis elétricas do solo para definir zonas de manejo. Dessa forma, este trabalho teve como objetivo avaliar a relação entre a variabilidade espacial da condutividade elétrica aparente e propriedades do solo em regiões de produção de cafés de montanha. A condutividade elétrica foi medida no perfil de solo de 0,00-0,20 m (CE20) e 0,00-0,40 m (CE40) usando um sensor portátil. Os valores de CE20 e CE40 foram de 1,80 mS m-1 e 1,22 mS m-1 , respectivamente. Ambas CE20 e CE40 apresentaram baixa correlação com as propriedades químicas e a textura do solo, sendo que, a correlação mais elevada foi obtida para o fósforo remanescente com valores de 0,427 e 0,465, respectivamente. Palavras-chave: Agricultura de precisão. Zonas de manejo. Sensores. *Autor para correspondência 1 Recebido para publicação em 02/08/2011; aprovado em 01/05/2012 Parte da Tese de Doutorado do primeiro autor apresentada ao Programa

Metrological assessment of TDR performance for measurement of potassium concentration in soil solution

“…The shape of soil particles can also be a secondary source of error (Jones et al, 2002). The discrepancy presented in that study indicates that the error Although the same concentrations of KCl were applied to both soils, the amplitude of errors for the clay soil was lower than that for the sandy soil; this may be due to the fact that at higher concentration of clay particles, ions migrate from the soil solution to the particles micelle, thereby decreasing the electrical conductivity of the soil solution (Santana et al, 2007;Oliveira et al, 2011).…”

“…A grid of soil columns, initially air-dried, was formed, consisting of 24 treatments for each soil type ( Figure 1A), following the methodology proposed by Andrade Neto et al (2012) and Santana et al (2007). Each column had specific conditions of moisture and electrical conductivity, obtained by applying a KCl solution to the column ( Figure 1B).…”

“…6: Figure 2A illustrates the behavior of the absolute sample error (RE) associated with the estimate of potassium concentration by TDR versus the electrical conductivity of the soil solution. As implied by Santana et al (2007), the greater the electrical conductivity of the soil solution, the greater the uncertainties associated with the estimate of TDR readings. Furthermore, it should be noted that there is symmetry between the increase in error by overestimation and underestimation for both soil materials: Loany Sand (Figure 2A), Eqs.…”

“…This application is facilitated through the combination of two models. The first, mentioned previously, determines CEw, and the second is characterized by the relationship between the electrical conductivity of the soil solution and the concentration of a specific ion, Ci, Santana et al, 2007;Souza & Folegatti, 2010;Andrade Neto et al, 2012) Much research has been directed toward the quantification of the dielectric losses (K") and its influence on the determination of the dielectric constant (Ka) and the apparent electrical conductivity (ECa). Cataldo et al (2008;2009) stated that even with appropriate calibration criteria, TDR readings can be affected by systematic or random errors, causing fluctuations in measurements.…”

Potassium estimation in the soil solution based on electrical conductivity and soil water content

“…The soil solution may be an alternative for obtaining nutrient levels by laboratory analysis or by using kits for fast determination of levelsof these nutrients. Nutrient levels in soil solution may also be estimated by models from bulk electrical conductivity (ECw) or soil solution electrical conductivity (ECss) (Rhoades et al, 1976;Vogeler & Clotheir, 1996;Muñoz-Carpena et al, 2001;Santana et al, 2007).…”