Dryland wheat production is a cornerstone of agriculture in Eastern Oregon, where growers operate in a semiarid climate with limited rainfall and narrow margins for managing soil moisture, fertility and crop risk.
By showing that one biochar application can improve soil pH, increase nutrient retention and store carbon for more than a decade, the study provides practical evidence for a soil health strategy that could support both farm productivity and climate-smart agriculture.
For decades, winter wheat–summer fallow systems helped farms produce reliable wheat crops by conserving precipitation. But over time, low crop residue, intensive production and long-term use of ammonium-based nitrogen fertilizers have contributed to two growing soil health problems: declining soil organic carbon and increasing soil acidity.
Those changes can reduce soil structure, water retention and nutrient availability. In more acidic soils, wheat can face greater risk from nutrient imbalances, disease and winter injury. As productivity declines, growers may need more fertilizer to maintain yields, increasing costs and environmental risk.
Researchers at Oregon State University and Washington State University tested whether biochar could provide a long-lasting way to address both problems.
Researchers Paulina B. Ramírez and Stephen Machado at the OSU’s Columbia Basin Agricultural Research Center (CBARC) near Pendleton and Shikha Singh of Washington State University at Lind Dryland Research Station evaluated a long-term field experiment established in 2013 on Walla Walla silt loam soil near Pendleton.
The study tested biochar made from forest waste and applied once at three rates in a winter wheat–spring pea rotation. Researchers compared those plots with plots that received no biochar and with plots that received nitrogen fertilizer alone.
After more than a decade, the results showed that the one-time biochar application in 2013 continued to improve soil conditions for more than 10 years.
Biochar increased soil pH by up to 0.9 units, with the strongest and longest-lasting effects in plots that received higher rates. The pH improvement was concentrated in the surface soil layer, where the biochar had been incorporated and where crop roots take up many nutrients.
The increase matters because soil pH affects nutrient availability. Higher pH was associated with improved cation exchange capacity, a measure of the soil’s ability to hold and supply nutrients. This helps soils retain nutrients that crops need during the growing season.
Biochar-amended soils also showed higher levels of calcium, magnesium, potassium and zinc, while reducing iron solubility associated with more acidic conditions.
Biochar stored carbon
The study, published in the journal Frontiers in Sustainable Food Systems, also found that biochar increased soil organic carbon stocks and that much of that benefit persisted for more than 10 years.
Soil organic carbon supports soil structure, water-holding capacity, nutrient cycling and long-term productivity. In dryland systems with limited rainfall and low biomass production, rebuilding carbon can be difficult.
Biochar added stable carbon directly to the soil. Compared with non-amended control plots, soil organic carbon stocks increased by 95% to 207%, depending on the application rate. Although carbon levels were somewhat lower in later measurements, biochar-treated plots still showed lasting gains.
Moderate rates showed promise
Early yield data showed that biochar paired with mineral nitrogen improved crop performance compared with nitrogen alone, though responses differed by crop.
Wheat showed modest gains at moderate biochar rates. Spring peas showed a stronger response at the lowest rate tested. The highest rate did not provide additional yield benefit and was associated with greater year-to-year variability in wheat.
Those findings point to a practical lesson: biochar may work best when matched to soil conditions, crop needs and fertilizer management rather than applied as a one-size-fits-all amendment.
Ramirez is an OSU research associate at CBARC. Machado is a professor of crop physiology/agronomy in the OSU Department of Crop and Soil Science and Extension dryland cropping system agronomist, based at CBARC. Singh is a research assistant professor in the Department of Crop and Soil Sciences WSU based at Lind Dryland Research Station.
Public value
OSU research is helping dryland growers and agricultural decision-makers evaluate tools that can protect soil productivity, reduce long-term input pressure and strengthen resilience in semiarid farming systems.
By showing that one biochar application can improve soil pH, increase nutrient retention and store carbon for more than a decade, the study provides practical evidence for a soil health strategy that could support both farm productivity and climate-smart agriculture.
Applied research like this gives growers region-specific information they can use to make management decisions that protect public and private investment in agriculture.
Funding for this work was provided by the U.S. Department of Agriculture’s Agricultural Research Service through the project Soil Health and Crop Productivity in Pacific Northwest Dryland Wheat Production Systems. Additional funding came from Wallowa Resources, Portland General Electric and OSU’s Agricultural Research Foundation.
