Seasonal Variation of Physical and Chemical Properties in a Black Soil under No-Till and Conventional Tillage in Northeast China

Most studies on changes in soil properties under no-till (NT) and conventional tillage (CT) systems were focused on the annual differences, and only a few on the seasonal variation. This study assessed the seasonal changes of soil properties under NT and CT in two separate fields, i.e., flat farmland and sloping farmland, during the maize-growing season in a typical Black soil of Northeast China. We measured the total porosity (TP), >1 mm water stable aggregate (PA(1)), the mean weight diameter (MWD), infiltration rate (initial and steady infiltration rates, IIR and SIR), soil organic carbon (SOC), ammonium nitrogen (NH4+-N) and total phosphorus (TOP) content. In conventional tillage, there was a decline in TP, PA(1), MWD, infiltration rate and SOC during the experimental period in both farmlands. For NT, the infiltration rate decreased during the season but TP changed slightly; PA(1), MWD and SOC were higher in August compared with the other months. The highest values of NH4+-N and TOP were in June under both tillage systems in both farmlands. Compared with NT, there was higher TP and IIR in CT but lower MWD and SIR in May. As the season progressed, PA(1), MWD and infiltration rate were lower in CT than in NT from June to October. The greatest differences in PA(1) and MWD were observed in August at both sites. There was higher SOC and NH4+-N in NT but lower TOP in CT. There was better soil structure and infiltration rate in the early stage of crop growth in CT, while NT had a beneficial effect on soil structure stability and infiltration capacity at both sites during the growing season. NT also improved SOC and NH4+-N content and should be applied widely in the Black soil area of Northeast China.