doi:10.2489/jswc.71.3. FEATURE Impact of soil erosion on soil organic carbon stocks Kenneth R. Olson, Mahdi Al-Kaisi, Rattan Lal, and Larry Cihacek oil erosion by wind and water and impacted the net primary productivity of reported that the SOC stock of timberland subsequent sediment transport and the land as a source for SOC stocks and and prairie soils declined with cultivation Sdepositional processes may lead to the environment (Lal et al. 1998). in North America. The rate of decline was soil organic carbon (SOC) loss especially Before determining the impacts of 25% + 33% for southwestern, 36% + 29% from a sloping agricultural land unit. wind and water erosion, and their related for southeastern, 34% + 24% for northwest- The erosion processes change land unit processes of transport and deposition on ern, and 22% + 10% for the northeastern SOC stock by transporting SOC-rich SOC stocks, we need to establish clear United States. Lal (1999) reported SOC sediment off an agricultural land unit, standard for SOC stock recharge. This stock loss by cultivation of 30% in the oxidizing SOC stocks, and releasing car- mechanism is referred to as SOC seques- north-central United States. This compares bon dioxide (CO2) into the atmosphere, tration (Olson 2013; Olson et al. 2014a, with a summary of historical studies in the as well as causing loss of SOC through 2014b; Sundermeier et al. 2005; Lal et Great Plains by Cihacek and Ulmer (1995). surface runoff. Thus, erosion, transport, al. 1998; Mann 1986). The definition of Depending on the length of time, cultiva- and depositional processes redistribute soil C sequestration requires that an agri- tion resulted in SOC losses of 7% to 51% landscape SOC, enhance oxidation, and cultural land unit with borders must be with longer periods of cultivation showing create a SOC source and a sink. However, identified for monitoring soil C seques- more SOC loss than shorter terms of culti- redistributed SOC to bottomland soils tration, storage, retention, and loss. There vation (see table 1). They also summarized is not sequestered SOC if it originates are three basic types of land units (study the effects of tillage or residue management outside the borders of the measured land plots) often used by researchers for actu- where the latter showed positive increases unit. In order to establish an active sink ally measuring SOC stock change and in SOC while various intensities of till- for soil carbon (C) sequestration, plants sequestration: (1) eroding, (2) depositional, age reduced SOC by 1% to 51% (see table on a land unit must take CO2 from the and (3) mixed landscape (combined erod- 2) (Cihacek and Ulmer 1995). However atmosphere and store it in the humus ing and depositional). The SOC of these these “classical” studies do not often clearly or SOC fraction within the agricultural three types of land units is impacted dif- define what their baseline SOC stock was land unit. Therefore, the objective of this ferently by the mechanisms of wind and at the start of the studies to permit verifica- review and analysis paper is to understand water erosion, transport, and deposition. tion of results. and highlight the effects of soil erosion, The underlying effects of soil erosion pro- These losses in SOC can be attributed to transport, and deposition of SOC stock. cess are biological, physical, and chemical several processes that include the accelera- Natural or so-called geological erosion, changes of the SOC stocks. Soil erosion tion of SOC loss by mineralization of SOC an important terrestrial process, has shaped processes and mechanisms negatively stock and water and wind erosion where the surface of the earth and formed some affect the SOC sequestration amounts and sloping soils are devoid of crop residue cover. of the most fertile (alluvial and loess) soils rate, and jeopardize soil productivity (Lal The role of erosion process in changing soil since the beginning of time. However, 2003) and increase greenhouse gas (GHG) C stocks is by a preferential transport of the acceleration of this process by anthropo- emissions (MEA 2005). light organic component and alteration of genic activities (e.g., deforestation, biomass Land units, especially sloping and erod- the soil physical and biological properties, removal/burning, plowing, drainage, and ing, under row cropping systems with which are drivers for soil C sequestration. change in land use by conversion of natural intensive tillage, can lose considerable Results from field experiments ecosystems to managed agroecosystems) amount of sequestered SOC stock and (Salemme and Olson 2014; Olson et al. has adversely affected the SOC stock, sediment through water and wind ero- 2014c, 2013a, 2011; Kumar et al. 2012; impacted water resources, and negatively sion. Troeh et al. (2004) state, “The sorting Gennadiyev et al. 2010) have shown, after action of either water or wind removes a approximately 150 years of agricultural high proportion of the clay and humus use and accelerated soil erosion, that the Kenneth R. Olson is professor emeritus in the Department of NRES, College of Agriculture, Con- from the soil and leaves the less productive agricultural lands have significantly less sumer, and Environmental Sciences, University coarse sand, gravel, and stones behind. Most SOC stocks of the same soil than when of Illinois, Urbana, Illinois. Mahdi Al-Kaisi is a of the fertile soil is associated with the clay previously under a native forest or prairie. professor of agronomy, Department of Agron- omy, College of Agriculture, Iowa State Univer- and humus.” Change in land use is a major Table 1 summarizes the percent change sity, Ames, Iowa. Rattan Lal is a professor in the factor affecting the SOC stock, especially in in native SOC stocks after 90 to 150 School of Environment and Natural Resources, sloping soils prone to erosion, as the land years of agricultural use. Some research- The Ohio State University, Columbus, Ohio. use is changed from native prairie or forest ers (Salemme and Olson 2014; Olson et Larry Cihacek is an associate professor of soil science, School of Natural Resources Science, to conventional and erosive row crop agri- al. 2014c, 2013a, 2011; Kumar et al. 2012; North Dakota State University. cultural systems (Olson et al. 2012, 2013a, Gennadiyev et al. 2010) reported that the 2013b). Franzluebbers and Follett (2005) conversion of prairie to agricultural land JOURNAL OF SOIL AND WATER CONSERVATION **PROOF - NOT FOR DISTRIBUTION** MAY/JUNE 2016—VOL. 71, NO. 3 61A for 90 to 140 years resulted in a loss of Table 1 between 20% and 51% of the SOC stock, The effects of soil erosion through land use change on soil organic carbon (SOC) stocks. and conversion of forest to agricultural land for 100 to 150 years resulted in a Soil organic carbon SOC stock loss of 10% to 52%. Thus, it Years of (% change from native is essential to understand the effects of Location Land use cultivation vegetation baseline) References soil erosion in the context of agricultural Brookings, South Dakota Prairie — Baseline Olson et al. 2014c use, especially in intensive agriculture Cropland 90 –20% production systems, where erosion pro- Harlan, Iowa Prairie — Baseline Salemme and Olson 2014 cess becomes a driver in establishing C Cropland 140 –51% Knoxville, Illinois Forest — Baseline Olson et al. 2013a sources and loss as CO2 rather than a sig- nificant contributor to soil C retention Cropland 150 –52% within a land unit (Lance et al. 1986). Albany, Illinois Forest — Baseline Olson et al. 2011 Olson et al. (2013b) and Young et al. Cropland 150 –48% (2014) showed that nearly level (<1%) Dixon Springs, Illinois Forest — Baseline Olson 2007 upland agricultural plots were also subject Cropland 140 –10% to erosion, transport, and deposition of Hanover, Illinois Forest — Baseline Gennadiyev et al. 2010 SOC-rich sediments. It has often assumed Cropland 140 –35% that plots with nearly level (<1%) slope Hoytville, Ohio Forest — Baseline Kumar et al. 2012 gradients have been significantly affected Cropland 100 –52% by erosion. Tillage can accelerate the loss Wooster, Ohio Forest — Baseline Kumar et al. 2012 of soil C stocks in conventional agriculture Cropland 130 –35% systems. Intensive tillage plays significant role in accelerating soil C loss through WIND AND WATER EROSIONAL Cihacek et al. (1992) worked with sand oxidation of organic matter, destruction PROCESSES IMPACT ON SOIL ORGANIC grain–sized wind erosion sediments on of soil aggregates, and reduction in water CARBON STOCK high clay soils (Vertisols) and soils with infiltration rate leading to significant water Soil erosion is a four-step process: (1) higher SOC stock. Soil particles smaller erosion and surface runoff of C-rich sedi- breakdown of structural aggregates, (2) than sand moved if wind has enough ments. Olson et al. (2013b) used a fly ash transport of C and sediment in water energy. In contrast, heavy particles (sand method and determined the SOC concen- runoff or wind, (3) redistribution of C and fine gravels) move in close proxim- tration of Muscatune and Sable soils for a and sediment over the landscape, and (4) ity to the ground surface (Stoke’s law) by nearly level (<1%) agricultural plot area deposition and burial of C and sediment a process called “saltation” by which one located near Monmouth, Illinois. The crop in depressions under inundated anaerobic particle strikes another setting up a chain sequence was corn (Zea mays) and soybean conditions (figure 1) (Lal 2003). reaction (Troeh et al. 2004). (Glycine max) for the previous 27 years, and Basic principles governing the fluvial Deposition of soil particles by salta- plot area had been cultivated for the last processes are similar for wind erosion tion or surface creep also results in wind 130 years. There was no tile drainage sys- whereby aggregates are disrupted exposing erosion sediments often being deposited tem in the plot area.