October 31, 2011
The amount of global carbon outputs have increased with the industrial revolution and rising need for agriculture, brought about by a rapid population growth. Agriculture over the years has become a major contributor to the global carbon cycle, especially as it now accounts for approximately 14% of global land use. It tends to deplete soil carbon because land used for agriculture has a lower net primary productivity than land that is kept in it’s natural state with undisturbed soil and processes.
In order to better understand the ways in which we are emitting carbon and effecting the carbon cycle, one must better understand the cycle itself. Carbon is absorbed by plants during photosynthesis in the form of carbon dioxide, along with sunlight and water. Plants then produce glucose and oxygen. When plants decompose, the carbon is transferred to the soil, where it is stored along with mineral carbon. Additionally, when animals eat plants, the carbon is passed from one to the other. Therefore this carbon can be released into the atmosphere during the respiration of plants and animals, the burning of fossil fuels, or, in the case of farming, when soil is tilled (Soil Science and Management 5th Edition, Plaster).
California’s agriculture tends to differ from that in the rest of the US in that it grows a large amount of perennial crops and specialty crops such as vegetables, nuts and fruits. California’s climate makes it the ideal provider of specialized high value crops to the rest of America, and much of its economy has been built on this industry. Perennial orchards and vineyards account for roughly a third of agricultural land (Kroodsma and Field). Since California has long hot summers, irrigated soils go through distinctive wet and dry cycles between water applications, which impacts the amount of dissolved organic carbon in soils. For these reasons, it’s evident that the carbon cycle is particularly vital in California industries and agriculture (Kroodsma and Fields).
California has smaller levels of carbon sequestration, most likely largely due to warmer temperatures, irrigation, and a strong lack of conservation tillage. This practice disturbs the soil less, but is not practiced as much in California because there is less of a risk of erosion than in the rest of the US. However, carbon storage in California is improved by the growth of perennial agriculture. It agitates the soil less and decomposes faster than annual plants.
There are practices, both farming and industrial, that can be put into effect in California’s agriculture to reduce carbon emissions. Farmers can implement increased use of conservation tillage to leave soil undisturbed and reduce emissions. They can also return pruning of plants to the soil as mulch. It has been proven that if soil is mulched, rarely tilled and has plants growing, loss of CO2 is decreased. Waste wood from orchards and vineyards can be used in biomass power-plants, both to reduce waste and the burning of fossil fuels. California has already begun decreasing field burnings, as that releases CO2 (Kroodsma and Fields). These practices implemented together would reduce carbon emissions while simultaneously improving crop yields and productivity.
About the authors: Lily Phillips and Ariana Verdu are working towards their bachelor degrees in the USC Dornsife College of Letters, Arts and Sciences.