It's well established that identical soils with different moisture levels will have varying pH.
The item I'm not finding is a citation for pH shifts in containers with regard to wet dry cycles.
Biologically it seems that many plants and most soil biology would have evolved, for the most part, to exploit the dynamics of wet/dry since steady state soil moisture would be uncommon.
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http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=2211&context=usdaarsfacpub
Nutrient Cycling in Agroecosystems
The effect of soil moisture on mineral nitrogen, soil electrical conductivity,
and pH
Inorganic nitrogen in the soil is the source of N for non-legume plants. Rapid methods for monitoring changes
in inorganic N concentrations would be helpful for N nutrient management. The effect of varying soil moisture
content on soil mineral nitrogen, electrical conductivity (EC), and pH were studied in a laboratory experiment. Soil
NO3-N increased as soil water-filled pore space (WFPS) increased from 0 to 80 cm3 cm−3. At soil moisture levelsgreater than 80 cm 3cm−3,NO3-N concentration declined rapidly and NH4-N concentration increased, likely dueto anaerobic conditions existing at higher WFPS levels.
Soil pH did not change as soil moisture increased from 100 g kg−1to 400 g kg−1 and increased from 6.2 to 6.6 at higher levels of soil moisture. Soil EC was correlated with soil mineral N concentration when measured in situ with a portable EC meter ( R2=0.85) or in the laboratory as 1:1 soil water slurries (R2=0.92). Results suggest that EC can be used to rapidly detect changes in soil inorganic N status in soils where salts and free carbonates are not present in large amounts
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SHORT-TERM EFFECTS OF MOISTURE CONTENT ON SOIL SOLUTION pH AND SOIL EH
Zárate-Valdez, José L.1; Zasoski, Robert J.2; Läuchli, André E.2
This laboratory study examined the short-term effects of soil moisture on the soil solution pH (pHss). Within minutes after adding water to dry soil, soil solution pH changed. As moisture increased, pH increased, whereas redox potential (Eh) decreased, and consequently, soil Eh and pHss were negatively correlated (
r2 = 0.90). Soil pH and Eh changes in relation to moisture content fit sigmoidal curves well (
r2 > 0.96). Altered pH and Eh response to moisture levels in chloroform treatments suggested that the observed pH changes were microbially mediated. We suggest that the rapid pH decrease observed in soil incubated at "field capacity" is due to proton generation associated with nitrification. Increased pH in saturated soils seems to be due to denitrification reactions. Addition of a nitrification inhibitor to soils resulted in smaller pH decreases. It seems that conditions conducive to denitrification occur at water contents much below saturation. In saturated Yolo silt loam, soil solution pH increased rapidly in the first 8 h and was nearly constant for the next 2 days. Proton consumption in saturated soils and proton production in soils maintained at field capacity fit as a power function very well. Based on the rapid changes in pHss in several agricultural soils, we conclude that soil pH as commonly measured (soil/water ratio 1:1-1 h of equilibration) may not reflect the pHss at longer time periods or be a good measure of soil pH in the field. The effects are especially pronounced in weakly buffered coarse textured soils.
