Temporal Effects of Biochar and Dairy Manure on Physicochemical Properties of Podzol: Case from a Silage-Corn Production Trial in Boreal Climate

A field experiment was conducted to evaluate the effects of biochar and dairy manure (DM) on physicochemical properties of podzolic soils, as well as to establish the relationships between selected physicochemical properties and soil electrical conductivity (EC) in a silage-corn production system. Nutrient requirements of the crop were met through different nutrient sources considering soil nutrient status, nutrient availability from DM (DM, DM + biochar) and regional crop nutrient recommendations. Experimental treatments included control, inorganic nitrogen (IN), IN + biochar, IN + DM, and IN + DM + biochar. DM was applied at 30,000 L ha(-1), whereas biochar was applied at 20 Mg ha(-1) and mixed within the top 20 cm of the soil. Disturbed soil samples as well as time domain reflectometry (TDR) measurements were collected from treatment plots on four field days. Results showed no significant (p > 0.05) treatment effects on soil pH and cation exchange capacity (CEC) within each field day. However, significant temporal effects were recorded for pH, EC, apparent electrical conductivity (ECa) and electrical conductivity of the soil solution (ECw). Soil depth (0-10 cm and 10-20 cm) had no significant effect on treatments. Significant positive correlations were recorded for EC with soil organic carbon and CEC (ECa, ECw 0-10 cm, & 10-20 cm, p = 0.000). Correlation results show that ECa measurements as a proxy to investigate the variability of key soil properties over large areas, but further investigation between ECa data and soil properties should be carried out to address uncertainties associated in predicting these properties.