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Tillage influence on soil properties and crop productivity depends on soil, crop, climate, and duration. Two long-term experimental sites with contrasting soils were selected to assess the influence of no-till (NT), minimum tillage (MT), and plow tillage (PT) under continuous corn (Zea mays L.) and cornsoybean [Glycine max (L.) Merr.] (CS) rotations on soil organic C (SOC) stock, bulk density (p,,), water-stable aggregation (WSA), aggregate tensile strength, penetration resistance, available water capacity (AWC), and corn yield. Experiments began in 1962 in northeast Ohio on a well-drained silt loam soil and in 1964 in northwest Ohio on a poorly drained clay loam soil. Results were compared with soil under an adjacent undisturbed woodlot (WL). The WL soils had the highest SOC content and stock. In the cultivated silt loam soil, stock was higher under NT (20.7 Mg ha"!) followed by MT (17.3 Mg ha"!) and PT (16.8 Mg ha~i) for the 0-to 10-cm depth. Soil pj, for this depth was lower under NT by 8 and 3% than PT and MT, respectively. The percentage of total WSA >2000 \im in soil under NT (47%) was significantly higher than under MT (38%) or PT (34%). A similar trend was observed for the clay loam soil. Rotation also influenced soil properties. Corn yields were higher (3 yr) and lower (1 yr) during 5 yr for the silt loam soil under PT than NT and unaffected or slightly higher under NT for the clay loam soil. Long-term (47-49 yr) use of NT practices are highly sustainable and result in higher SOC and WSA, lower Pl,, and greater AWC content than MT or PT.

Johnson et al., 2016). Removal of crop residue reduces soil organic carbon (SOC), and impacts soil productivity. However, the impacts of residue removal rates on soils depend on certain factors such as soil texture, soil topography, initial contents of SOC, tillage, and cropping system (Blanco-Canqui et al., 2013). Water is the most limiting factor for crop production in regions where either irrigation is not available or precipitation is limited (Das et al., 2017). Water stored in the soil profile helps to fulfill the water requirement for following crop in the rotation. Corn residue left behind after corn harvest helps to conserve water in soil (Iqbal et al., 2013) and plays an important role in water conservation and hence increase grain yields where irrigation or precipitation is a limiting factor in crop production (Van Donk et al., 2010; VanLoocke et al., 2012). The long-term adoption of CC could negate the adverse effects of residue removal and increase SOC and improve soil water dynamics, eventually improving crop production and soil productivity (Basche et al., 2016a; Basche et al., 2016b; Kahimba et al., 2008). A study by Chahal and Van Eerd (2018) showed that cover crop increased SOC concentrations by 8.4 to 9.3% and crop yield by 7.9 to 22% compared with no cover crop treatment. Basche and DeLonge (2017) showed that adoption of CC for more than 10 yr improved soil hydrological properties

Core Ideas Long‐term annual application of manure maintained the soil pH but inorganic fertilizer decreased it. Manure application increased soil organic carbon (SOC) and total nitrogen (TN). Higher manure rate helps in improving the water stable aggregates compared to inorganic fertilizer at 0‐ to 10‐cm depth. Manure enhances soil fertility and crop yield; however, an optimum rate of manure application is important to avoid any negative impacts to soils and the environment. This study was conducted to assess the long‐term impacts of manure and inorganic fertilizer rates on soil organic carbon (SOC), total nitrogen (TN), water stable aggregate (WSA), pH, and electrical conductivity (EC) under corn (Zea mays L.)‐soybean (Glycine max L.) rotation at Beresford (established in 2003) and Brookings (established in 2008), South Dakota (SD). Study treatments included low (LM), medium (MM) and high (HM) manure, medium (MF) and high (HF) inorganic fertilizer, and control (CK). Soil samples were extracted from four replicates at 0‐ to 10‐cm, 10‐ to 20‐cm, 20‐ to 30‐cm and 30‐ to 40‐cm depths from either site in 2015. Results showed that manure application maintained the soil pH at 0 to 10 cm depth; whereas, inorganic fertilizer decreased it compared to the control treatment at either site. The highest SOC concentrations at 0‐ to 10‐cm depth were observed under HM (38.3 g kg–1) as compared to that under MM (30.9 g kg–1), LM (27.6 g kg–1), MF application (24.0 g kg–1), HF (25.8 g kg–1) and CK (23.3 g kg–1). Furthermore, HM treatment significantly increased SOC for each depth increment from 0‐ to 40‐cm compared to the inorganic fertilizer at either site. A similar trend was observed for the TN but differences were not always significant. On an average, manure increased the EC (1.56 dS m–1) by 2.2 times compared to that of fertilizer (0.71 dS m–1) for 0‐ to 10‐cm depth. Similarly, manure significantly increased WSA by 7.2 and 5.6% compared to that of fertilizer at 0‐ to 10‐cm depth for Brookings and Beresford, respectively. Data from this study concluded that the long‐term annual application of manure improved selected soil properties compared to that of inorganic fertilizer.

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