Soil pH from soil Ambient and CO2

This dataset comprises soil pH measurements collected from controlled greenhouse experiments designed to evaluate the effects of single and combined heavy metal (HM) treatments on paddy soil under ambient (RK) and elevated CO₂ (RKCO₂) conditions. Three heavy metals—Cadmium (Cd), Zinc (Zn), and Iron (Fe)—were applied individually and in binary combinations across multiple concentration levels. Soil pH was monitored at three rice growth stages: 65, 95, and 130 days after planting.

Heavy Metal Treatment Structure

Heavy metals were applied at five concentrations each:

Cd (ppm): 5, 10, 15, 20, 25

Zn (ppm): 150, 200, 250, 300, 350

Fe (ppm): 200, 250, 300, 350, 400

Combined treatments followed matched pairs representing increasing HM stress:

Cd+Zn: (5–150), (10–200), (15–250), (20–300), (25–350) ppm

Cd+Fe: (5–200), (10–250), (15–300), (20–350), (25–400) ppm

Zn+Fe: (150–200), (200–250), (250–300), (300–350), (350–400) ppm

All treatments included a 0 ppm control for both greenhouse environments.

Soil Sampling and Preparation

Soil samples were air-dried, gently ground, and sieved through a 250 μm mesh to remove debris, following standard soil preparation procedures (Jones et al., 2021). The processed samples were subsequently used to assess soil pH and heavy-metal-related physicochemical properties.

Soil pH Determination

Soil pH was measured using a 1:2.5 soil-to-deionized-water ratio, modified from established protocols (Duddridge & Wainwright, 1981; Smith et al., 2020). For each sample, 10 g of soil was mixed with 50 mL of deionized water, shaken for 30 minutes, and the pH was recorded using a glass-electrode pH meter (WTW INOLAB Level 1).

Dataset Structure

The dataset contains:

pH values for single-metal treatments (Cd, Zn, Fe)

pH values for combined-metal treatments (Cd+Zn, Cd+Fe, Zn+Fe)

Measurements across two atmospheric conditions:

RK (ambient CO₂)

RKCO₂ (elevated CO₂)

Measurements at three time points:

65 days

95 days

130 days

Statistical significance assessed at p < 0.05

Purpose of the Dataset

This dataset provides high-resolution soil pH responses to heavy metal stress under current and future CO₂ scenarios, enabling evaluation of:

soil acidification dynamics,

HM–CO₂ interaction effects,

temporal shifts in soil chemistry during rice growth,

early indicators of soil degradation under combined environmental stressors