Twenty two years of tillage and mulching impacts on soil physical characteristics and carbon sequestration in Central Ohio

Knowledge about the changes in carbon (C) concentration and mechanical and hydrological properties under different tillage and mulch treatments is necessary to assess the feasibility of adoption of conservation practices for sustaining productivity and protecting the environment. It is widely recognized that no-till (NT) farming conserves soil and water, saves energy, improves the environment and enhances soil quality. However, the magnitude and direction of tillage and mulch-induced changes are soil and site specific. Therefore, a field study was conducted on a long-term on-going experiment to evaluate the effects of three tillage {NT, ridge till (RT) and plow till (PT)} and three mulch rates (0,8 and 16 Mg ha(-1) yr(-1)) on soil physical properties and total C concentrations in macro (250-2000 mu m) and micro (<250 mu m) aggregates. The experiment was initiated in 1989 on a Crosby Silt Loam (Stagnic Luvisol) in Central Ohio. The data show positive effects of mulch rate on soil physical attributes and total C concentration under NT. Significant (P < 0.05) variations in bulk density (rho(b)) and penetration resistance (PR) along with their interactions were observed among tillage and mulch treatments. The water infiltration capacity (i(c)) ranged from 1.2 cm h(-1) (PT) to 4.6 cm h(-1) (NT). With increase in mulch rate from 0 to 16 Mg ha(-1), saturated hydraulic conductivity (K-s) for 0-10 cm depth increased from 1.78 to 3.37, 1.57 to 2.95 and 1.37 to 2.28 (x10(-2) cm h(-1)) under NT, RT and PT, respectively. Analyses of variance indicate significant interaction between tillage, mulch and soil depth for the K-s. Similarly, the mean weight diameter (MWD, mm) increased from 0.36 to 1.21, 0.29 to 0.84, 0.25 to 0.62 under NT, RT and PT, respectively, with increase in mulch rate from 0 to 16 Mg ha(-1). Total C (%) increased from 1.26 to 1.50, 1.20 to 1.47 and 0.95 to 1.10 under NT, RT and PT, respectively, with increase in mulch rate from 0 to 16 Mg ha(-1) Macro-aggregates (250-2000 mu m) contained 30% more total C and N concentrations than microaggregates (<250 mu m). Under NT, the soil showed a higher structural stability than PT with significantly lower compaction values. Further, with NT the soil showed a higher capacity to retain C than PT. Thus, long term use of NT along with mulch application enhances soil quality with respect to soil mechanical, hydrological properties along with carbon concentration in the soil. (C) 2012 Elsevier B.V. All rights reserved.