Effects of Biochar on Yield, Nutrient Recovery, and Soil Properties in a Canola (Brassica napus L)-Wheat (Triticum aestivum L) Rotation Grown under Controlled Environmental Conditions

Biochar applications have proven effective in highly weathered tropical and subtropical soils. However, less is known about how different biochars behave as amendments when added to temperate soils. Previously, studies have used high biochar rates (tens to hundred t ha-1) but such high rates are impractical for farm application because of its low density and powdery nature. Therefore, a study was conducted to evaluate the response of canola and wheat grown in rotation to biochars at three different rates (0, 1, and 2 t ha−1) added to a Brown and Black Chernozem soil from Saskatchewan, Canada, in a controlled environment experiment. Five different biochars were obtained from three feedstock sources and added at 0, 1, and 2 t ha-1 with, and without, nitrogen (N) and phosphorus (P) fertilizer at 50 or 100 kg N ha-1 and 25 kg P2O5 ha-1. Application of fast pyrolysis wheat straw fine fraction and willow fine fraction biochars resulted in significant increases in canola biomass yield when added to the Black Chernozem soil, while the other biochar types had no effect. No significant responses to application of any of the biochars were observed on the Brown Chernozem. For the wheat crop, only flax straw fine biochar added at 1 t ha-1 had a significant residual effect on yield. Biochar did not alter the availability of N and P, and its effects on soil pH, organic carbon, and electrical conductivity were minor. We suggest that biochar applications at 1-2 t ha-1 to prairie Chernozems will not have large effects on plant growth or soil properties.