Effects of Biochar Amendments on Wheat Productivity Under Chemical-Fallow.

Soil organic matter (SOM)) continues to decline under the traditional winter wheat summer fallow cropping system (WW-SF) that is predominant in the Pacific Northwest. The continuous depletion of SOM is beginning to threaten sustainability of WW-SF. The decline in SOM is mostly attributed to insufficient residues (one crop in two years) and tillage that accelerates SOM decomposition. Chemical fallow slows down SOM decomposition but does not make up for the insufficient residues. Given that the WW-SF is reliability and may be the only viable system in drier areas ways to increase SOM in this system have to be devised. Biochar may provide the answer. Biochar is charcoal produced from pyrolysis (combustion at low oxygen levels) and is resistant to decomposition. Biochar increases soil water holding capacity, cation exchange capacity, nutrient retention capacity, fertilizer use efficiency, and soil microbial populations, conditions required for sustained crop production. This study evaluated the effects of biochar derived from forest wastes on wheat grown in a chemical fallow field at rates of 0, 10, 20, and 40 tons/acre. Biochar increased soil pH and grain yields from 45 to 60 bu/acre, an increase of 26 to 33%. However, applying biochar at rates above 10 tons per acre did not significantly increase yield.  Biochar application did not influence ears m² and test weight.