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Development of on-the-go soil sensing technology for mapping soil pH, potassium and nitrate contents

Balaji Sethuramasamyraja, University of Nebraska - Lincoln


The main objective of precision agriculture is optimized management of spatial and temporal field variability to reduce waste, increase profits and protect the quality of the environment. Knowledge of spatial variability of soil attributes is critical for precision agriculture. Different approaches to assess this variability on-the-go have been pursued through development of soil sensors. One of the methods, direct soil measurement (DSM), has been applied in a commercial implement for on-the-go mapping of soil pH. In this research, DSM was evaluated in terms of extendibility to other soil chemical properties, including soluble potassium and residual nitrate. Further, superior ISE based approach called agitated soil measurement (ASM) has been developed and analyzed. Electrode calibration, precision and accuracy while performing DSM and ASM under laboratory and field simulation conditions were analyzed. The potential applicability of DSM/ASM for studied chemical soil properties declined in the order: pH > potassium > nitrate. The reason for this decline was attributed to the nature of the methodology itself. While developing ASM technique, the following factors have been evaluated: soil-water ratio (SWR), quality of water used for electrode rinsing (QWR) and for ion extraction (QWE), presence of ionic strength adjuster (ISA) and solution agitation (stirring). It was concluded that for on-the-go mapping agitated purified water extraction without ISA, addition of a fixed amount of water (1:1 SWR), and regular (tap) water for ISE rinsing should be used. To physically implement the ASM methodology, an Integrated Agitation Chamber Module (IACM) was developed and incorporated into the commercial soil pH mapping equipment. Based on the field simulation test, neither precision nor accuracy estimates have been improved as compared to the DSM field simulation test (precision error ranged between 0.11 for pH to 0.22 for pNO3). However, in addition to reduced electrode abuse, laboratory evaluation of ASM has revealed significantly lower measurement errors for all three properties and, therefore, retained the potential for improved quality of on-the-go field mapping. ^

Subject Area

Agriculture, Soil Science|Engineering, Agricultural

Recommended Citation

Sethuramasamyraja, Balaji, "Development of on-the-go soil sensing technology for mapping soil pH, potassium and nitrate contents" (2006). ETD collection for University of Nebraska - Lincoln. AAI3208086.