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Soil Health

There are several key issues in soil health: erosion, organic carbon content, contamination with metals and other pollutants, acidification, salinization, biodiversity, sealing with impermeable material, nutrient balance, compaction, and waterlogging 1. Following we consider erosion and soil carbon.

Erosion

Worldwide, 20-30 billion tons of soil are lost to water erosion, and an additional uncertain amount to wind erosion 1. With water erosion causing an estimated $25/ton of damages (2020 dollars) 2, erosion may cause at least $500-750 billion of damages worldwide every year.

Agriculture is the main cause of erosion 3.

The image: "erosion.svg" cannot be found!

Conventional agriculture causes significantly more erosion than natural biological and geological processes, while conservation agriculture is comparable. Conservation agriculture is a farming methodology that, among other things, seeks to minimize soil disturbance by avoiding tilling. Erosion rates are global averages, and values can vary widely by location, though are generally higher in hillier terrain. Source: Montgomery 4.

Agroforestry to create windbreaks 5 and terracing on hilly terrains 6 also help reduce erosion.

Problem:
Erosion
Solution:
Windbreaks
Problem:
Erosion
Solution:
Terracing

Soil Carbon

The ability of soils to hold carbon is of great interest especially due to climate change. The transport of carbon in and out of soils is as follows.

The image: "soil_carbon_transport.svg" cannot be found!

Source: NASA 7.

Since the beginning of agriculture, soils have lost an estimated 133 million tons of carbon, or about 15 years of world CO2 emissions at current rates 8, though estimates vary widely 9.

Agriculture generally results in a loss of soil carbon, and conservion of land to other uses, especially forests, generally results in a gain.

The image: "soil_carbon.svg" cannot be found!

Source: 9

Arsenic

High concentrations of arsenic in soil can result in high arsenic in crops, causing health problems. Arsenic exposure causes bladder and lung cancer, diabetes, pulmonary disease, cardiovascular disease, and other problems 10. Arsenic exposure is believed to cause 43,000 deaths in Bangladesh annually 10.

The World Health Organization sets standards of at most 0.2 mg/kg (0.2 parts per million) arsenic concentration in soil and 50 micrograms/liter in drinking water 11. Arsenic concentrations in both the soil and water exceed these values in many parts of the world 12. Natural sources of arsenic are as follows 12.

  • Volcanic eruptions
  • Ocean spray

Anthropogenic sources include the following 12.

  • Domestic and industrial waste
  • Arsenic-containing pesticides
  • Burning of arsenic-rich coal
  • Contaminated soil amendments
  • Mining, particularly goal mining
  • Cattle dipping vats (an arsenic-containing solution to kill ticks)
  • Chicken litter

One solution to soils contaminated by arsenic and other heavy metals is phytoremediation: the growing of plants or fungi to collect the metals out of the soil 13. Intermittent flooding of soils and iron-based soil amendments can also help reduce soil arsenic, and proper plant breeding can reduce the uptake of soil arsenic by plants 11.

References

  1. Intergovernmental Technical Panel on Soils. "Status of the World's Soil Resources". Food and Agriculture Organization of the United Nations. 2015. ↩ ↩2

  2. BIO-Intelligence Service, Food and Agriculture Organization of the United Nations. "Food Wastage Footprint - Impacts on Natural Resources – Summary report". 2013. ↩

  3. Lichtfouse, E., Navarrete, M., Debaeke, P., Véronique, S., Alberola, C. Sustainable Agriculture, Volume 1. Springer Science & Business Media. November 2009. ↩

  4. Montgomery, D. "Soil erosion and agricultural sustainability". Proceedings of the National Academy of Sciences of the United States of America 104(33), pp. 13268-13272. August 2007. ↩

  5. Udawatta, R. P. "Agroforestry practices for water quality and quantity benefits". Proceedings of the 4th European Agroforestry Conference, Agroforestry as Sustainable Land Use, 28-30 May 2018, Nijmegen, The Netherlands 2018 pp.269-273 ref.14. 2018. ↩

  6. Chen, D. "Effects of terracing practices on water erosion control in China: A meta-analysis". Earth-Science Reviews 173, pp. 109-121. October 2017. ↩

  7. Riebeek, H. "The Carbon Cycle". NASA Earth Observatory. June 2011. ↩

  8. Sanderman, J., Hengl, T., Fiske, G. J. "Soil carbon debt of 12,000 years of human land use". Proceedings of the National Academy of Sciences of the United States of America 114(36), pp. 9575-9580. August 2017. ↩

  9. U. S. Global Change Research Program. "Second State of the Carbon Cycle Report, Chapter 12: Soils". 2018. ↩ ↩2

  10. World Health Organization. "Arsenic". February 2018. ↩ ↩2

  11. Punshon, T., Jackson, B. P., Meharg, A. A., Warczack, T., Scheckel, K., Guerinot, M. L. "Understanding arsenic dynamics in agronomic systems to predict and prevent uptake by crop plants". Science of the Total Environment 581, pp. 209-220. March 2017. ↩ ↩2

  12. Kayode, O. T., Aizebeokhai, A. P., Odukoya, A. M. "Arsenic in agricultural soils and implications for sustainable agriculture". IOP Conference Series: Earth and Environmental Science 655: 012081. 2021. ↩ ↩2 ↩3

  13. Saldaña-Robles, A., Abraham-Juárez, M.R., Saldaña-Robles, A. L., Saldaña-Robles, N., Ozuna, C., Gutiérrez-Chávez, A. J. "The Negative Effects of Arsenic in Agriculture: Irrigation Water, Soil and Crops, State of the Art". Applied Ecology and Environmental Research 16(2), pp. 1533-1551. January 2018. ↩