Field Measurement of Soil Surface Chemical Transport Properties for Comparison of Management Zones

Abstract

Management of chemicals in soil is important, yet the complexity of field soils limits prediction of management effects on transport. To date, few methods have been available for field measurement of chemical transport properties, but a recently developed dripper–time domain reflectometry technique allows rapid collection of data for determining these properties. The objective of this work was to apply this technique for comparison of chemical transport properties for different soil management zones. Experiments were conducted comparing four interrow management zones: no‐till nontrafficked, no‐till trafficked, chisel plow nontrafficked, and chisel plow trafficked. Drip emitters were positioned at 12 locations in each zone and used to apply water followed by a step input of CaCl2 tracer solution. Breakthrough curves were measured via electrical conductivity with time domain reflectometry probes. The mobile–immobile model was fit to the breakthrough curves to determine chemical transport properties. Mean chemical transport properties were 0.34, 0.11 h−1, 10 cm h−1, 164 cm2 h−1, and 5 cm, for the immobile water fraction, mass exchange coefficient, average pore‐water velocity, mobile dispersion coefficient, and dispersivity, respectively. All five properties showed significant differences between management zones. Differences in mass exchange and mobile dispersion coefficients coincided with differences in tillage, while differences in mean pore water velocities coincided with differences in traffic. The immobile water fraction was largest for the no‐till nontrafficked zone. These results represent one of very few reports for field measurement of chemical transport properties and the first application of this approach for comparison of chemical transport properties across management zones.

A piecewise analysis model for electrical conductivity calculation from time domain reflectometry waveforms

“…For example, Peng et al (2019) and Coppola et al (2016) performed crop water demand predictions, irrigation optimizations and soil salinity controls based on soil EC measurements; Sanches et al (2018) used EC values as a reference to adjust soil pH via lime additions; Yang et al (2019) and Luo et al (2020) measured EC variations of highway roadside soil samples following concrete surface grinding to assess the effects of concrete waste on soil chemical properties and plant growth. In addition, continuous EC measurements over time with specific tracers, e.g., KCl or CaCl 2 , are used to study soil chemical transport properties and provide breakthrough curves for a range of soil types under a variety of managed field conditions, such as compaction or tillage (Gaur et al, 2007;Heitman et al, 2007).…”

Role of Air Flow on Changing Soil Properties and Plant Nutrition in Egyptian Alluvial Soil

“…However, these impacts are still poorly understood, and the findings of the few researches that have looked into this topic thus far appear to be contradictory. Compaction is thought to restrict the extent of preferred flow because it interrupts or kills macro pores in soil [16].In sieved and repacked samples, it was discovered that compaction increased preference flow in a sandy loam, whereas preferential flow was recorded in a clay loam at all compaction levels. Dye tracing investigations have shown that any macro holes that remain after the compaction event or those that are subsequently re-generated due to physical (i.e.…”