Fertoz: Leveraging the Chemical Properties of Rock Phosphate Fertilizer to Sequester Carbon

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Applying P rock fertilizer to P-deficient soil can significantly increase crop yields and help facilitate carbon sequestration and boost soil health. Increasing soil P promotes earlier germination and more extensive root growth, resulting in larger, more productive plants. The increase in biomass due to the addition of P, particularly that of the roots, facilitates greater sequestration of carbon from the atmosphere into the soil. Root-derived carbon represents between 60 and 75% of soil organic carbon, showing that root biomass and C are important determinants of soil organic carbon (Balesdent and Balabane, 1996).

Application of rock phosphate fertilizer

Phosphate rock can be supplied as a granular or powdered soil amendment applied directly to the soil in agricultural cropping systems. Phosphorus is vitally important for many plant functions including photosynthesis, metabolic processes, cell division, germination, and is needed in large amounts for optimal plant growth and yield. The availability of phosphorus in the soil for uptake by crops is often limited (IPNI, 1999). Fertoz summarized from peer-reviewed research and in-house trials, the percentage yield advantage of rock phosphate applied alone versus no rock phosphate applied (control) and concluded that an increase in 15% of the yield of rock phosphate is expected. More than 80 treatment comparisons were made from 13 articles in several crops including legumes, corn, cereals, potatoes and oilseeds. Previous research has shown that increasing plant yield and biomass stimulates soil organic matter, leading to greater carbon sequestration in the soil. Sequestration potentials are tabulated for crops and soil types based on incremental yield increases. A 15% yield advantage from rock phosphate application is used to calculate the yield increase above the average yield for each crop type. The net kg of CO2 eq for each kg of grain produced (determined by previous research) is multiplied by the increase in yield to determine the potential for carbon sequestration. Each ton of sequestered carbon is equivalent to 1 carbon credit.

Fertoz Rock Phosphate fertilizer is a tool we provide to organic growers to achieve better annual crop yields as well as to boost long-term soil fertility. Fertoz Rock Phosphate is a natural, organic approved sedimentary fertilizer, directly mined and minimally processed, and 100% North American sourced. Fertoz also offers additional all-in-one NPKS products that provide plants with all essential macronutrients for plant growth and increased crop yield.

Rock phosphate soil mineralization

Phosphate rock can be part of larger mineral complexes called apatite in which minerals, usually calcium (Ca), but also iron (Fe) can be present. Routine use of calcium-containing soil amendments may have a beneficial effect on OC retention in soils with significant concentrations of Fe oxide, which in turn may affect soil fertility (Sowers et al. al., 2018). An alternative to conventional geological sequestration is carbon mineralization, where CO2 is reacted with metal cations such as magnesium, calcium and iron to form carbonate minerals. Mineral CO2 sequestration seeks to mimic the natural weathering process in which calcium or magnesium silicates are transformed into carbonates by reaction with CO2 Gaseous and/or aqueous CO2 (Ca, Mg)SiO3 (s) + CO2 (g)to(Ca, Mg)CO3 (s) + If O2 (s). The formation of Ca, Mg, and Fe carbonates is expected to be the primary means by which CO₂ is immobilized. Applied silicate minerals like rock phosphate undergo reactions with CO2 in the rhizosphere, releasing base cations (e.g., Ca2+mg2+) and alkalinity. Depending on soil chemistry, this can lead to the formation of pedogenic carbonates or be released to the oceans through runoff; both pathways store carbon with an estimated lifetime of tens of millennia (Hartmann et al., 2013; Renforth & Henderson, 2017).

Imports of phosphate fertilizers

Additionally, the United States relies heavily on phosphate fertilizer imports from Morocco and Russia, importing over $1 billion worth of phosphate fertilizer in 2019. However, the U.S. Department of Commerce (Commerce) recently determined that these imports are subsidized by the governments of these countries, which has harmed the American industry (USITC, 2021). Clearly, the United States should reduce its reliance on imported fertilizers and shift to more sustainable, locally sourced phosphate fertilizers. Fertoz Rock P and other fertilizer products fill this space.

Carbon sequestration with phosphate fertilizers

In organic production, phosphorus deficiency is a major concern due to continuous removal during harvest. To ensure the continued availability of phosphorus, off-farm sources are often required. Fertoz Phosphate Rock is a very effective solution for common phosphorus deficiencies in the production of organic and regenerative crops. Several peer-reviewed research studies have demonstrated the yield benefits of applying phosphate fertilizers, most of which show statistically significant yield increases. Lal et al., 1998 studied the transformational effects of good fertility management on crop yield, biomass, residues and the correlation with soil organic carbon sequestration. A carbon sequestration rate of 50-150 kg CO2/ha/year (20-60 kg CO2/ac/year) is possible through good soil fertility management that includes the application of NPK fertilizers (Lal et al., 1998).

Gan et al., 2014 studied the effects of good agricultural practices on yield and carbon sequestration. They determined during their trials that for every kg of wheat grain produced, a trickle of 0.027 to 0.377 kg of CO2 eq is sequestered in soil (Gan et al., 2014). A bushel of wheat is equivalent to 27.216 kg. In organic production, the average wheat yield is 20 bushels/acre (544.32 kg/acre). A 15% increase in yield can be expected with the application of rock phosphate as noted above; which is approx. 3 bushels/acre (81.648 kg/acre). An additional amount of 2.2 kg of CO2/ac at 30.78 kg CO2/ac can be sequestered by the application of rock phosphate to a wheat crop based on a yield increase of 3 bushels/acre. Mathewa et al., 2017 analyzed the soil organic carbon response to different crop types and carbon allocation to roots, shoots and soil from 389 field trials. They used data from many different climatic regions, soil textures, pHs, bulk densities, and tillage practices. Their results regarding crop type and root carbon stocks are summarized in the figure below in graph (c).

Root-derived carbon represents between 60 and 75% of soil organic carbon, showing that root biomass and C are important determinants of soil organic carbon (Balesdent and Balabane, 1996). The additional carbon stock from rock phosphate assumes a 15% increase in yield and biomass (including root biomass) calculated by multiplying the carbon stock by 0.15. The potential for soil organic carbon sequestration (from a 15% increase in yield due to rock phosphate) assumes that only 60% of soil organic carbon comes from root-derived carbon. A multiplication factor of 0.6 was used to calculate soil organic carbon from roots.

Phosphate rock has the potential to contribute an additional 26.71 kg C/ac (cereals), 9.11 kg C/ac (legumes) and 10.93 kg/ac (oilseeds) of soil carbon through an increase of 15 % of biomass. Jarecki and Lal, 2003 reviewed the benefits of various good agricultural management practices contributing to increased yields and potential carbon sequestration.

Their review spans multiple regions of the world, under various management practices, soil types, and crops. The table below summarizes their findings separated by crop type that correlate average global yields with carbon sequestration.

Fertoz wants to widely encourage producers to reduce their carbon footprint while making conventional operations more sustainable and making organic farms more productive to meet the growing demand for organic, regenerative and sustainable foods.

References

Balesdent, J. and Balabane, M. 1996. Major contribution of roots to soil carbon storage inferred from maize-grown soils. Soil Biology and Biochemistry, Volume 28, Number 9, Pages 1261-1263, ISSN 0038-0717, https://doi.org/10.1016/0038-0717(96)00112-5. (https://www.sciencedirect.com/science/article/pii/0038071796001125)

Gan, Y., Liang, C., Chai, Q., Lemke, RL, Campbell, CA, and Zentner, RP 2014. Improving agricultural practices reduces the carbon footprint of spring wheat production. Nature communications, 5:5012, DOI: 10.1038/ncomms6012

Hartmann, J., West, AJ, Renforth, P., Köhler, P., De La Rocha, CL, Wolf-Gladrow, DA, … Scheffran, J. (2013). Improving chemical weathering as a geoengineering strategy to reduce atmospheric carbon dioxide, deliver nutrients, and mitigate ocean acidification. Reviews of Geophysics,51(2), 113-149.https://doi.org/10.1002/rog.20004

Jarecki, MK, and R. Lal. 2003. Crop management for soil carbon sequestration. Critical Reviews in Plant Science 22:471-502.

Lal, R., Kimble, J., Follett, RF and Cole, CV 1998. The potential of cropland in the United States to sequester carbon and mitigate the greenhouse effect. Ann Arbor Press, Chelsea, Michigan.

Mathewa, I., Shimelisa, H., Mutemaa, M., and Chaplot, V. Which crop type for atmospheric carbon sequestration: results from a global data analysis. Agriculture, Ecosystems and Environment 243: 34-46

O’Laughlin, P. 2021. Phosphate Fertilizers from Morocco and Russia Harm US Industry, Says USITC. United States International Trade Commission. URL: Phosphate Fertilizers from Morocco and Russia Harm US Industry, Says USITC | USITC. (accessed April 2022).

Renforth, P., & Henderson, G. (2017). Assessment of ocean alkalinity for carbon sequestration. Geophysical Journals,55(3), 636-674. https://doi.org/10.1002/2016R G000533

Sowers, TD, Stuckey, JW & Sparks, DL 2018. The synergistic effect of calcium on organic carbon sequestration in ferrihydrite. Geochemistry Trans 19, 4. https://doi.org/10.1186/s12932-018-0049-4

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