Where is inorganic carbon stored

Wollastonite was tumbled with soil in large buckets for blending, with the aim being to achieve good mixing but with minimal disruption to soil texture. Testing a wide range of wollastonite dosage on experimental plots will help to understand which dosage range is best suited for field application, and determine an upper limit beyond which plant and mineral weathering benefits decline. A higher dosage was investigated to study the alfalfa since as a winter-hardy cover crop, it could be used in fields that decide to apply wollastonite at larger dosages in late-Fall post-harvest, just prior to alfalfa seeding.

Moreover, at the field scale, the highest suitable amendment dosage is not intended to be used in a single application, but could be thought of as the cumulative of several applications over multiple crop cycles.

Plots of various MSA compositions 1. Each microplot, with a dimension of 0. No other chemical, mineral or organic amendments e. The plots were open to drainage to emulate the setup as close as possible to the field conditions.

At the start of the experiment, the soils were supplied with adequate tap water, and later depended on rain water as the source of water supply. Daily climatic data from this study is reported in the Supplementary Material Figure S1. The maximum, minimum, and mean temperatures recorded during the experimental run are The schematic of the experimental set up is given in Figure 1 and Figure S1C.

The experiments ran for 14 weeks, from late June to early October, At the end of the experiment, the soil from each plot was sampled, using a soil core sampler 0. Figure 1 Schematic representation of the experimental setup.

The first row represents the plots with no plants, and first column represents the control plot using unamended soil as-received. The plant growth and development were analyzed based on the development stages. At the end of the experimental run, after 14 weeks, the plants were harvested by cutting them just above the soil level. The number of plants recovered from each microplot was: 30 soybean plants, and 15 alfalfa plants. The main growth parameters recorded were plant height, stem width, leaf blade width, root dry biomass, and above-ground biomass dry weight.

All such measurements reported in the results section were averaged among all collected plants from each microplot, and standard deviations values were calculated. The yield of the soybean pods collected from the plants at week 14 was determined from the combined mass of pods from each subplot with each microplot. Subplots contained 10 soybean plants. Thus the yield was averaged between the three subplots in each microplot, and standard deviation calculated.

The pH of the samples was determined using a ratio of soil and 0. Soil samples were suspended in MiliQ water 5 g in 20 ml , to which 7 ml of 4M HCl was added within in a sealed Erlenmeyer flask connected to a graduated water-filled manometer-style column that recorded the released CO 2 volume Eijkelkamp Calcimeter The amount of CaCO 3 accumulated in the soil as the result of the sequestration of the dissolved CO 2 present in the soil pore-water by the calcium ions dissociated from wollastonite is calculated using Equation 4.

The CaCO 3Initial value accounts for the carbonate content added to the soil as the result of wollastonite application which contains small amounts of naturally present calcite together with the initial CaCO 3 content in the untreated soil. The pH and calcimetry analyses were made in triplicates and mean results reported herein have been represented along with standard deviations.

The fine wollastonite consisted of The inherent calcite CaCO 3 amount of 3. Duplicate samples, in loose powder form, were analyzed for 20 min using standardless Omniam method, under helium and at 1 kW power, and concentrations were calculated as oxides. The average sum before normalization was The average concentrations of the detected oxides present in amounts greater than 0.

The particle size distribution of wollastonite was determined by wet laser diffraction Malvern Mastersizer SM , and the surface weighted Sauter mean diameter D [3,2] was found to be 4. Figure 2 shows the variation in the soybean root biomass and above-ground dry biomass, when grown with different wollastonite dosages, using a sample size n of 30 plants.

The plant height data is given in Figure S4. The soybean trials showed that the plants performed best in the 5 wt. In all treatments, the roots had reached the base of the growth containers and exhibited healthy root biomass. There was no significant change in the stem and leaf blade widths for the various treatments Table S2 in the Supplementary Material.

Figure 2 Variation in the soybean: a root biomass, and b above-ground biomass dry weight, with different dosages wt. The 5 wt. The yield decreased for the 7. At the end of the growth trial, the pH of the MSA 7. The suitable pH range for soybean is 6. Even though the yield in case of MSA 7. For MSA 10 microplot, root biomass was lower by Overall, all tested wollastonite dosages did not result in negative growth performance, i.

This implies that an appropriate amount of wollastonite, when added to the soil, supports good plant growth.

Figure 3 A Variation in the weight of the soybean pods with increasing wollastonite dosage analyzed per subplot of 10 plants. Overall, the growth of alfalfa was better than the control in all treatments. In contrast to the soybean trials, growth of alfalfa was best with 10 wt. At the end of the week growth period, the alfalfa grown in MSA 10 was taller in height by threefold Figure S7 , possessed higher above-ground dry weight by 3.

The pH of the control soil plot was 6. Alfalfa is a cover crop that is usually sown after the growing season, therefore this cover crop would be compatible with applying a higher wollastonite dosage that could help with speeding up wollastonite incorporation into the soil.

Then in the upcoming season, when other agricultural crops will be planted, the soil will be well mineralized with wollastonite as a result of the cover crop-timed application. Figure 4 Variation in the alfalfa: A root biomass and above-ground biomass dry weight, with different dosages wt. Wollastonite-amended soil promoted good plant growth, thus confirming its potential to be used as a soil amendment in the agronomic sector.

Canadian Wollastonite and its distributors have already been marketing wollastonite to farmers in Ontario and beyond, and assessing the effects and fate of wollastonite in commercial farms is also part of our current research. In the present study, increased soybean yield in wollastonite-amended soil, as well as healthier alfalfa growth, shows the positive effects of this alkaline-earth mineral. In addition to the aboveground plant growth, root biomass also showed a positive response to wollastonite addition.

Visual inspection of the roots showed no observable signs of swollen root tips, or root browning. Root nodules formed, thus indicating the unaltered activity of rhizobium bacteria in the wollastonite-containing soil environment. These positive responses of the growth performance may be due to the release of silica into the soil Equation 2 , which accumulates in certain plants in the form of phytogenic silica Keller et al.

Si is known to offer numerous benefits to plant growth including better yield and quality, nitrogen fixation, and alleviate the abiotic and biotic stress as a result of extreme temperatures, metal toxicity, salinity or drought Ma, ; Mitani and Ma, ; Van Bockhaven et al.

Coskun et al. Guntzer et al. The plant-available form of silicon in the soil is mainly as monomeric silicic acid H 4 SiO 4 Dietzel, , which is the hydrated form of SiO 2 , thus readily available when wollastonite weathers in soil.

Hodson et al. In the agriculture sector, wollastonite can be used as a liming agent, as it helps in increasing the soil pH reducing soil acidity by adding calcium and magnesium, thus reducing aluminum and manganese solubility in the soil Osman, ; Goulding, It can be applied using the same broadcaster as the traditional lime spreader.

Fertilizing the soil with Si is known to improve the yield of rice as well as sugarcane, especially in Si-deficient oxisol soils Savant et al. In fact, using wollastonite for Si fertilization of soil leads to Si accumulation in the aerial parts of the sugarcane Rodrigues, Hence, application of wollastonite in agricultural fields is a known practice; however, using wollastonite for sequestering carbon via terrestrial enhanced weathering is not well reported. In our recent study Haque et al.

Soils at two additional farms leafy vegetables, and potato that had voluntarily used wollastonite amendment for one or more crop cycles were also studied for evidence of CO 2 sequestration.

This study showed that application of wollastonite resulted in pedogenic carbonate accumulation, proportional to time since, and rate of, mineral amendment.

World reserves of wollastonite exceed million tons, and in Ontario, the nearest mine is located in Kingston Brioche, Hence, the availability and location of the alkaline-earth mineral are also important to determine its feasibility as a mineral soil amendment.

Wollastonite was used in this study because it is available in Ontario, Canada. This page has been archived and is no longer updated.

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