Daniel Ginting

Portable Probes to Measure Electrical Conductivity and Soil Quality in the Field

Abstract Soil electrical conductivity (EC) is a useful indicator in managing agricultural systems, but tools for convenient and inexpensive measurements in the field are generally lacking. Handheld conductivity probes were designed to evaluate in‐field naturally occurring and human‐induced total soluble electrolyte levels in soil and water. The probes were used to survey and monitor EC in the field and to assess soil and water quality as related to environmental stability and sustainable food production. A pencil‐sized 16‐cm probe (PP) was connected to a handheld Hanna (DiST WP 4) conductivity meter, resulting in an economical, compact, and easy to use device. The tool provided accurate and precise results compared with laboratory instrumentation under standardized conditions of soil water content and temperature. Soil samples, varying widely in texture and organic matter content, and having ECs ranging from 0.13 to 2.32 dS m−1 were used for comparison. Mean values and coefficients of variation were similar for the PP and the commercial laboratory EC meter with values determined with the two instruments being strongly correlated (r2=0.96–0.99). The handheld and PP probes effectively replaced expensive and cumbersome laboratory and field instruments used to measure EC in water and soil samples. The probe measurements were useful alternatives to conventional methods as they enabled accurate and precise measurement of EC, were a manageable size for field use, and were reliable and economic. The utility of EC as an indicator of soil health, plant‐available N, and environmental quality is also presented. This article is a joint contribution of the U.S. Department of Agriculture and University of Nebraska, Lincoln. Published as Journal Series Number 14402.

Construction and Testing of a Simple and Economical Soil Greenhouse Gas Automatic Sampler

ABSTRACT Quantification of soil greenhouse gas emissions requires considerable sampling to account for spatial and/or temporal variation. With manual sampling, additional personnel are often not available to sample multiple sites within a narrow time interval. The objectives were to construct an automatic gas sampler and to compare the accuracy and precision of automatic versus manual sampling. The automatic sampler was tested with carbon dioxide (CO2) fluxes that mimicked the range of CO2 fluxes during a typical corn-growing season in eastern Nebraska. Gas samples were drawn from the chamber at 0, 5, and 10 min manually and with the automatic sampler. The three samples drawn with the automatic sampler were transferred to pre-vacuumed vials after 1 h; thus the samples in syringe barrels stayed connected with the increasing CO2 concentration in the chamber. The automatic sampler sustains accuracy and precision in greenhouse gas sampling while improving time efficiency and reducing labor stress.