Does the duration of no-till implementation influence depth distribution of soil organic carbon, hydro-physical properties, and computed tomography-derived macropore characteristics?

Abstract

No-till (NT) is a sustainable alternative to conventional-till (CT), however, the impacts of NT and its duration on the depth distribution of soil organic carbon (SOC), physical and hydrological parameters are less studied. Therefore, the objective of this study was to evaluate the changes in soil hydro-physical properties and X-ray computed tomography (XCT)-derived macropore characteristics to a depth of 40 cm as influenced by the duration [short-(5-yr) and long-(30 yr) term] of NT practice on a previously conventionally-tilled (CT) soil. The treatments included: CT, initiated in 1991; long-term NT (LTNT),1991; and short-term NT (STNT), 2016 established on silty clay loam soil (Udic Haplustolls). Four replicated intact soil cores were collected from each treatment at 0–10, 10–20, 20–30, and 30–40 cm depths. Data showed that the LTNT stored 23% more SOC stock in the 0–40 cm depth as compared to the CT. The LTNT also increased the total nitrogen (TN) stock, soil water retention (SWR), plant available water (PAW) content, and saturated hydraulic conductivity (Ksat) to the depth of 40 cm as compared to the CT. The LTNT increased the XCT-derived soil macroporosity [pores with > 500 µm equivalent cylindrical diameter (ECD)] and pore connectivity up to 20 cm than the CT. However, the STNT implementation increased the SWR at − 0.6, − 5, and − 30 kPa, pore connectivity, and Ksat only for the 0–10 cm depth than the CT. In addition, PAW showed a high correlation with SOC content [Pearson correlation coefficient (δ) = 0.71], and Ksat was highly correlated with the modulus of XCT-derived Euler-Poincaré characteristic (a measure of local connectivity; δ = 0.61). The study highlighted that pore connectivity and Ksat in surface soil (0–10 cm) were most responsive to the implementation of NT on a previously tilled soil. Data suggest that a longer duration of NT implementation was required to improve the SOC and soil hydro-physical parameters to a deeper soil profile (0–40 cm). Therefore, we conclude that the conversion of tilled soil to NT practice has beneficial effects, depending upon the duration of NT implementation, in enhancing the SOC and hydro-physical conditions, which may help in storing more water in deeper soil for enhanced production.