Abstract
Apparent soil electrical conductivity (EC a ) measurements can be used for crop management in precision agriculture. However, EC a is a soil attribute that presents spatial and temporal variability. It is affected by a group of factors that act simultaneously on the soil, such as the soil texture, moisture content, organic matter content and ionic concentrations in the soil solution, which complicates analysis. For soil and crop management, it is important to determine whether the pattern of the EC a spatial variability changes over time. Thus, EC a measurements have the potential for delimiting management zones that are stable over time. The objective of this work was to determine whether the spatial variability pattern of EC a is maintained over time and under different soil conditions. To this end, the EC a was measured at different soil depths using a portable sensor on two crop fields. The first step was to measure and generate an EC a map for each area. By defining a path with the maximum EC a variability, 50 sampling points were located on each field. The EC a values were measured on 20 different dates in the 0 – 20 cm, 0 – 40 cm and 0 – 60 cm soil layers. The soil water content was measured at the same points in the 0 – 20 cm layer on the same dates. The temporal stability of the EC a was analyzed using spatial and temporal variability maps, a correlation analysis and a coefficient of variation over time for each field. In both areas, the EC a exhibited temporal stability in the spatial pattern variability at the three evaluated depths, even though the soil water content values changed on each date. EC a determination presents an important alternative for mapping agricultural fields for crop management in precision agricultural systems.
Highlights
Precision agriculture has been intensively developed in recent years, especially due to rapid advances in information technology and Geographic Information Systems (GIS)
Among the new sensing technologies employed in precision agricultural systems, the apparent soil electrical conductivity (ECa) has become an important tool for understanding the spatial variability of agricultural production systems
Many studies have reported the relationship of ECa with other soil attributes, including texture, water content, salinity, pH, cation exchange capacity (TERRÓN et al, 2011; HEIL; SCHMIDHALTER, 2011; ISLAM et al, 2012; SERRANO et al, 2012; VALENTE et al, 2012a) and crop yield (MANN et al, 2011; ALCÂNTARA et al, 2012)
Summary
Precision agriculture has been intensively developed in recent years, especially due to rapid advances in information technology and Geographic Information Systems (GIS). A large number of sampling points are necessary to provide sufficient information to generate a precise map of soil attributes. The acquisition and analysis of these samples are expensive and time-consuming task, which in some cases renders the process unfeasible. To overcome this problem, new technologies for direct and remote sensing have been developed for the acquisition of relevant spatial information from production fields to reduce the money and time expended for soil map generation. Among the new sensing technologies employed in precision agricultural systems, the apparent soil electrical conductivity (ECa) has become an important tool for understanding the spatial variability of agricultural production systems. ECa mapping may provide a rapid and effective means of identifying areas with similar features at a lower cost, allowing for needsbased management (FAROOQUE et al, 2012; VALENTE et al, 2012b)
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