Taking Advantage of the Chemical Properties of Rock Phosphate Fertilizer to Sequester Carbon

The application of rock P fertilizer to soil that is P deficient can significantly increase crop yields and help facilitate carbon sequestration building soil health. Increased soil P promotes early germination and more extensive root growth resulting in larger, more productive plants. The increased biomass from the P addition, especially that in the roots, facilitates greater sequestration of carbon from the atmosphere into the soil. Root derived carbon accounts for between 60 and 75% of soil organic carbons showing that root biomass and C are important determinants of soil organic carbon (Balesdent and Balabane, 1996).

Rock Phosphate Fertilizer Application

Rock phosphate can be supplied as a granular or powder 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 required in large amounts for optimal plant growth and yield. Phosphorus availability in the soil for crop uptake is often limited (IPNI, 1999). Fertoz summarized from peer reviewed research and internal trials, the percent yield benefit from rock phosphate applied alone compared to no rock phosphate applied (control) and concluded that a 15% increase in yield from rock phosphate is expected. Over 80 treatment comparisons were made from 13 articles in several crops including legumes, corn, cereals, potatoes and oilseeds. Past research demonstrates that increased yield and plant biomass boosts soil organic matter resulting in more carbon sequestered in the soil. Sequestration potentials are tabulated for crops and soil types based on incremental yield increases. A 15% yield benefit from rock phosphate application is used to calculate the yield increase above average yield for each crop type. The net kg CO2 eq for each kg of grain produced (determined through past research) is multiplied by the yield increase to determine the carbon sequestration potential. Each ton of carbon sequestered is equal to 1 carbon credit.

Fertoz Rock Phosphate fertilizer is tool we provide to organic growers to achieve greater annual crop yields as well as build long term soil fertility. Fertoz Rock Phosphate is a natural, organic approved, sedimentary fertilizer that is direct mined and minimally processed, and is 100% sourced in North America. Fertoz also offers additional all-in-one NPKS products that provide plants with all macro nutrients vital to plant growth and boosting crop yield.

Rock Phosphate Soil Mineralization

Rock phosphate can be part of larger mineral complexes called apatite in which minerals, typically calcium (Ca), but also iron (Fe) can be present. The common use of Ca-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., 2018). An alternative to conventional geologic 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 via reaction with CO2 gas and/or aqueous CO2 (Ca, Mg)SiO3 (s) + CO2 (g)à(Ca, Mg)CO3 (s) + SiO2 (s). 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 result in either the formation pedogenic carbonates or be delivered to the oceans via run-off; both routes store carbon with an estimated lifetime of tens of millennia (Hartmann et al., 2013; Renforth & Henderson, 2017).

Phosphate Fertilizer Imports

Furthermore, The US is heavily reliant on imports of phosphate fertilizers from Morocco and Russia, importing over one $1 billion in phosphate fertilizer in 2019. However, the U.S. Department of Commerce (Commerce) has recently determined that these imports are subsidized by the governments of those countries, which has adversely affected the US industry (USITC, 2021). It is evident that the US should reduce its reliance on fertilizer imports and shift to more sustainable, locally sourced phosphate fertilizer. Fertoz Rock P and other fertilizer products fill this space.

Carbon Sequestration with Phosphate Fertilizer

In organic production, phosphorus deficiency is a major concern due to continual removal through harvest. To ensure continuous phosphorus availability, off-farm sources are often required. Fertoz rock phosphate serves as a highly effective solution for common phosphorus deficiencies in organic and regenerative crop production. Multiple peer reviewed research studies have demonstrated the yield benefits from the application of rock phosphate fertilizer, most of which show statistically significant yield increases. Lal et al., 1998 studied the transformational effects of good fertility management on crop yield, biomass, residue and correlation to soil organic carbon sequestration. A carbon sequestration rate of 50-150 kg CO2/ha/yr (20-60 kg CO2/ac/yr) 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 farming practices on yield and carbon sequestration. They determined through their trials that for each kg of wheat grain produced, a net 0.027–0.377 kg CO2 eq is sequestered into the soil (Gan et al., 2014). One bushel of wheat is equal to 27.216 kg. In organic production, the average yield of wheat is 20 bu/ac (544.32 kg/ac). A 15% increase in yield can be expected through the application of rock phosphate as stated above; which is approx. 3 bu/ac (81.648 kg/ac). An additional 2.2 kg CO2/ac to 30.78 kg CO2/ac can be sequestered through the application of rock phosphate on a wheat crop based on yield increase of 3 bu/ac. Mathewa et al., 2017 analysed the response of soil organic carbon to different crop types and allocation of carbon to roots, shoots and the soil from 389 field trials. They used data from many different climatic regions, soil textures, pHs, bulk densities, and tillage practices. Their results relevant to crop type and root carbon stocks are summarized in the figure below in graph (c).

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

CROPRoot Carbon stock (Mg C/ha/yr)Additional root carbon stock with a 15% yield and biomass increase from rock phos (Mg C/ha/yr)Soil organic carbon sequestration potential from Rock Phos (Mg C/ha/yr)Soil organic carbon sequestration potential from rock phos (kg C/ac/yr)
Cereals0.70.110.06626.71
Legumes0.250.03750.02259.11
Oilseeds0.30.0450.02710.93

Rock phosphate 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 carbon to the soil through a 15% increase in biomass. Jarecki and Lal, 2003 reviewed the benefits of various good farm management practices contributing to increased yields and potential carbon sequestration.

Their review expands across multiple regions globally, under various management practices, soil types, and crops. The table below summarizes their findings separated by crop type that correlate average worldwide yields to carbon sequestration.

Fertoz wants to broadly encourage producers to lower their carbon footprint while making conventional operations more sustainable and making organic farms more productive to feed the growing demand for organic, regenerative, sustainable food.

References

Balesdent, J., and Balabane, M. 1996. Major contribution of roots to soil carbon storage inferred from maize cultivated soils. Soil Biology and Biochemistry, Volume 28, Issue 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, R.L., Campbell, C.A., and Zentner, R.P. 2014. Improving farming practices reduces the carbon footprint of spring wheat production.  Nature communications, 5:5012, DOI: 10.1038/ncomms6012

Hartmann, J., West, A. J., Renforth, P., Köhler, P., De La Rocha, C. L., Wolf-Gladrow, D. A., … Scheffran, J. (2013). Enhanced chemical weathering as a geoengineering strategy to reduce atmospheric carbon di-oxide, supply nutrients, and mitigate ocean acidification. Reviews ofGeophysics,51(2), 113–149.https://doi.org/10.1002/rog.20004

Jarecki, M. K., and R. Lal. 2003. Crop management for soil carbon sequestration. Critical Reviews in Plant Sciences 22:471–502.

Lal, R., Kimble, J., Follett, R. F., and Cole, C. V. 1998. The Potential of the US Cropland to Sequester Carbon and Mitigate the Greenhouse Effect. Ann Arbor Press, Chelsea, MI.

Mathewa, I., Shimelisa, H., Mutemaa, M., and Chaplot, V. What 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 Injure U.S. Industry, Says USITC. United States International Trade Commission. URL: Phosphate Fertilizers from Morocco and Russia Injure U.S. Industry, Says USITC | USITC. (accessed April 2022).

Renforth, P., & Henderson, G. (2017). Assessing ocean alkalinity for car-bon sequestration. Reviews of Geophysics,55(3), 636–674. https://doi.org/10.1002/2016R G000533

Sowers, T.D., Stuckey, J.W. & Sparks, D.L. 2018. The synergistic effect of calcium on organic carbon sequestration to ferrihydrite. Geochem Trans 19, 4. https://doi.org/10.1186/s12932-018-0049-4

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