Tillage-Effects on Quality of Two Contrasting Soils.

Agricultural soils are often being tested under different management practices with the aim of improving crop yield. However, tillage-impacts on quality of organic or muck soil systems are scanty and tillage-induced changes in soil characteristics when compared to contrasting soils are poorly understood. The aim of this research is to evaluate impacts of long and short-term tillage on two contrasting soils (organic: Mc and mineral: CrB) of Central Ohio. Soils managed under on-farm conditions were sampled during April and May, 2013 in Ohio, USA, at similar landscape positions under conventional tillage (CT) with moldboard ploughing, and no-till (NT) practices. Treatments included NT and CT for both sites, however, while the muck site has been continuously tilled for ~10 years with the adjacent no-tilled bare field with patches of grasses, the mineral site has been predominantly no-tilled for ~10 years with short-term (one year) introduction of CT. Soils sampled from 0-10, 10-20, 20-40, and 40-60 cm depths were analyzed for pH, electrical conductivity (EC), soil organic carbon (SOC), total nitrogen (TN), bulk density (BD), available water capacity (AWC), penetration resistance (PR), water stable aggregates (WSA), and texture (% of sand, silt and clay). All monitored parameters were significantly (p < 0.05) affected by soil type, however, some properties were changed by tillage practices only in the mineral soil (CrB). Tillage did not have any significant effects in organic soil probably due to porous nature and high organic matter content. Compared to mineral soil, the organic soil had 6.4 and 5 times higher SOC and TN concentrations, respectively, irrespective of the sampling depth. On the other hand, CT significantly affected BD, PR, WSA, and AWC, especially in the surface layer (0-10 cm) of CrB. The BD and PR were significantly reduced by CT for CrB soil by up to 14 (NT: 1.6 Mg m^-3), and 21% (NT: 611 kPa), respectively. Residue incorporation in CT plots in the plough layer (up to 20 cm) increased aggregation by 19% and SOC by 15% in CrB soil compared with those under NT (total aggregation: 70%, SOC: 2%).