BIOCHARS AS AMENDMENTS FOR SASKATCHEWAN AGRICULTURAL SOILS

Abstract

Biochars are the product of high temperature treatment of carbonaceous materials with little or no oxygen present, termed “pyrolysis”. Biochars derived from the pyrolysis of biomass feedstocks have proven effective amendments on highly weathered tropical soils. However less is known about their impact on temperate soils and associated crop growth. Moreover, there is inadequate knowledge of the impacts of different biochars produced from different feedstocks under differing pyrolysis conditions. Therefore, a study was conducted to evaluate the effectiveness of different biochars as amendments to improve soil conditions for crop growth, with emphasis on soil fertility and crop nutrition impacts. The response of canola-wheat in rotation to five biochars was evaluated in controlled environment and field experiments conducted on Brown and Black Chernozem soils over a two-year period. Treatments were biochar added at 1 and 2 t ha 1 without and with nitrogen (N) and phosphorus (P) fertilizers at 50 or 100 kg N ha 1 and 25 kg P2O5 ha 1. Parameters evaluated were crop biomass and grain yield, N and P uptake, % recovery of applied N and P, residual soil nutrients (NO3 N, and PO4+ P), pH, electrical conductivity (EC), % organic carbon (% OC) and gravimetric soil moisture. Biochar application resulted in significant increases (p<0.05) in canola yield compared to the control for two fast pyrolysis biochars originating from wheat and flax straw added to the Black Chernozem soil in both studies. No significant response was observed for any of the biochars on the Brown Chernozem. Slow pyrolysis biochar derived from willow feedstock appeared less effective did not show any significant response. Occasional depressions in crop yield were observed in both crops with both soils. In these calcareous Chernozems, biochar did not greatly alter the N and P availability, and its effects on soil pH, % OC, EC and moisture content were small and often non-significant. These results suggest that biochar applications at 1 2 t ha 1 to prairie Chernozemic soils will not have large effects on soil properties or plant growth. Higher rates of application will require development of application technology due to the dusty, powdery nature of the biochar material.