Pedosphere 27(1): 172–176, 2017 doi:10.1016/S1002-0160(17)60301-1 ISSN 1002-0160/CN 32-1315/P c ⃝ 2017 Soil Science Society of China Published by Elsevier B.V. and Science Press Letter to the Editor Effects of Tillage Practices and Land Use Management on Soil Aggregates and Soil Organic Carbon in the North Appalachian Region, USA Arun Jyoti NATH 1,2,∗ and Rattan LAL 1 1 Carbon Management and Sequestration Center, Ohio State University, Columbus OH 43210 (USA) 2 Department of Ecology and Environmental Science, Assam University, Silchar 788011 (India) (Received May 18, 2016; revised October 17, 2016) ABSTRACT Promoting soil carbon sequestration in agricultural land is one of the viable strategies to decelerate the observed climate changes. However, soil physical disturbances have aggravated the soil degradation process by accelerating erosion. Thus, reducing the magnitude and intensity of soil physical disturbance through appropriate farming/agricultural systems is essential to management of soil carbon sink capacity of agricultural lands. Four sites of different land use types/tillage practices, i) no-till (NT) corn (Zea mays L.) (NTC), ii) conventional till (CT) corn (CTC), iii) pastureland (PL), and iv) native forest (NF), were selected at the North Appalachian Experimental Watershed Station, Ohio, USA to assess the impact of NT farming on soil aggregate indices including water-stable aggregation, mean weight diameter (MWD) and geometric mean diameter (GMD), and soil organic carbon and total nitrogen contents. The NTC plots received cow manure additions (about 15 t ha -1 ) every other year. The CTC plots involved disking and chisel ploughing and liquid fertilizer application (110 L ha -1 ). The results showed that both water-stable aggregation and MWD were greater in soil for NTC than for CTC. In the 0–10 cm soil layer, the > 4.75-mm size fraction dominated NTC and was 46% more than that for CTC, whereas the < 0.25-mm size fraction was 380% more for CTC than for NTC. The values of both MWD and GMD in soil for NTC (2.17 mm and 1.19 mm, respectively) were higher than those for CTC (1.47 and 0.72 mm, respectively) in the 0–10 cm soil layer. Macroaggregates contained 6%–42% and 13%–43% higher organic carbon and total nitrogen contents, respectively, than microaggregates in soil for all sites. Macroaggregates in soil for NTC contained 40% more organic carbon and total nitrogen over microaggregates in soil for CTC. Therefore, a higher proportion of microaggregates with lower organic carbon contents created a carbon-depleted environment for CTC. In contrast, soil for NTC had more aggregation and contained higher organic carbon content within water-stable aggregates. The soil organic carbon and total nitrogen stocks (Mg ha -1 ) among the different sites followed the trend of NF > PL > NTC > CTC, being 35%–46% more for NTC over CTC. The NT practice enhanced soil organic carbon content over the CT practice and thus was an important strategy of carbon sequestration in cropland soils. Key Words: aggregate stability, macroaggregates, microaggregates, no-till, water-stable aggregation Citation: Nath A J, Lal R. 2017. Effects of tillage practices and land use management on soil aggregates and soil organic carbon in the north Appalachian region, USA. Pedosphere. 27(1): 172–176. More than 50% of the global annual carbon (C) emission (about 11 Gt) is absorbed by natural sinks (land and ocean); therefore, the annual uptake by the atmosphere ranges between 4 and 5 Gt C year −1 for the decade ending in 2015 (Le Qu´ er´ e et al., 2015). Hence, it is important to develop strategies that increase the C sink capacity of the natural sinks, especially those in the terrestrial biosphere so as to reduce the net uptake of CO 2 by the atmosphere (Lal, 2008). Soil organic C (SOC) as well as its potential to become a “managed” sink for atmospheric CO 2 has been a priority research area since the beginning of the 21st century (Lal, 2004; Sainju, 2006; Saha et al., 2011) because of its multiple benefits including the positive effects on soil physical, chemical, and biological properties (Carter, 1996; Lal, 2004). Therefore, in-situ SOC conservation should be prioritized in any management system to harness the soil C sink capacity. Conservation tillage, comprising a wide range of practices, is widely promoted as the best agricultural management practice to reduce soil ero- sion and maintain high SOC content (Lenka and Lal, 2013). The no-till (NT) practices have the potential to sequester SOC ranging from 0.3 to 0.4 Mg C ha −1 year −1 in European agricultural land (Freibauer et al., 2004). Similar values (0.2–0.4 and 0.3–0.4 Mg C ha −1 year −1 ) have also been reported from USA and Cana- * Corresponding author. E-mail: arunjyotinath@gmail.com.