Narrowing the Soil-Sample to Fertilizer-Application Gap Using Soil Sensors.

The greatest impediment to manual soil sampling followed by laboratory measurement for crop nutrient management is the time and expense associated with sampling, transportation, and analysis of the sample. When GPS-aided sampling came along in the early 1990’s, and increased number of samples per field, it was believed that the extra expense to derive soil nutrient maps would be offset by the increase in value obtained from improved nutrient crop-use efficiency with map-based variable-rate fertilizer applications. While improvements have been made relying on conventional soil sampling methods, many farmers perceive a marginal value to this type of sampling and mapping. The conclusion of many has been that more efficient and less expensive tools and procedures are needed for managing within field nutrient variability. From such has grown the development of on-the-go sensors. Soil sensors employing a wide array of different physical and chemical techniques have been lab tested and in some cases moved to crop production fields. Sensor-based nutrient management technologies offer higher spatial resolution, even though individual measurement accuracy may be less than that achieved by more controlled laboratory analysis. In the end, the higher mapping resolution along with sensing automation is projected to create increased economic value for producers as they manage crop nutrients. This presentation will review recent developments in the use of sensors to accomplish soil measurement and analysis for nutrient management.