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ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #155850


item Hummel, John

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2006
Publication Date: 8/1/2006
Citation: Yildirim, S., Birrell, S.J., Hummel, J.W. 2006. Laboratory evaluation of an electro-pneumatic sampling method for real-time soil sensing. Transactions of the ASABE. 49(4):845-850.

Interpretive Summary: In modern agriculture, the combination of low-cost computers, real-time controllers, navigational systems and developments in sensors make it possible to accurately and automatically apply soil amendments according to the needs of sub-field land areas. However, the success of this site-specific crop management depends on the ability to accurately characterize the variability within fields. This important soil, crop, and pest data must be collected using automated systems that include both sensors and a mechanism to obtain the soil sample. The sensor part of such a system has shown promise to be able to provide on-the-go soil nutrient measurements. The challenge remaining before using these sensors in real-time soil measurement is to build a rapid and precise soil sampling method. This paper reports on the initial development of an automated, compressed-air-activated soil sampling method to collect and transport soil samples for analysis. The compressed-air system could have some advantages over a mechanical sampling system, including being simpler, faster, more suited to digital control, and better at collecting a precise mass of soil. This on-the-go soil sampling technology, with appropriate sensors, could be used by crop consultants and corn producers to optimize target fertilizer application rates across a field. When coupled with computer-controlled applicators and navigational systems, the amount of fertilizer applied to each subfield area can be optimized for the crop being produced. A greater portion of the nutrients would then be utilized by the crop, resulting in reduced impact of agricultural practices on the environment, which benefits all consumers.

Technical Abstract: An automated electro-pneumatic soil sampling method based on pressurized air for real-time soil analysis was developed and tested under laboratory conditions. Pressurized air was applied for 36 ms across a 2.5-cm-diameter cylinder to cut a sample from a soil column and convey the sample along a delivery pipe into a container. An electro-pneumatic regulator valve was used to regulate the air pressure at 550, 690, and 830 kPa (80, 100, and 120 psi) using an analog electrical signal. A two-position solenoid valve controlled by a stand-alone microprocessor was used to control pulse duration. Laboratory tests were conducted to determine effectiveness of positive high-pressure air as a cutting force for different soil conditions. The effects of air pressure level, soil moisture content, soil compaction, and soil type on the quantity of soil sample obtained were investigated. Moisture content and pressure level were the most significant factors, while compaction was not significant (alpha=0.05) in terms of mass of soil obtained. Laboratory test results proved that pressurized air was effective in cutting and transporting a soil sample in a short time period (36 ms) for all different soils studied in this experiment. The electro-pneumatic method was also capable of obtaining a consistent amount of soil sample with a coefficient of variation of less than 20%, for any individual treatments in the experimental design. The electro-pneumatic soil sampling method is a viable candidate as a soil sampling system for continuous, on-the-go soil analysis.