Sustaining Winter Wheat Production using Biochar Amendments in Northeast Oregon
Sustainability of winter wheat – summer fallow (WW-SF), the predominant cropping system in inland Pacific Northwest (iPNW) is under threat from soil health deterioration attributable to soil organic carbon (SOC) depletion (>60% of original SOC) and soil acidification (pH<5.5). Growing one crop in two years produces insufficient residues for SOC accretion in both conventional and no-till WW-SF systems. Lowering of soil pH is largely due to continuous use of ammonia-based fertilizer that produce acidity (H+) when converting to nitrate, the nutrient that plants readily absorb. However, WW-SF system remains popular and more reliable than annual cropping in low precipitation zones (<12 inches).
We propose to improve soil health and enhance sustainability of WW-SF systems using biochar, charcoal produced from pyrolysis (biomass combustion at low oxygen levels). Biochar is high in organic carbon that is resistant to decomposition and can increase SOC instantly while lowering soil acidity if it is alkaline.
Our objectives are to 1) evaluate the impact of biochar derived from wheat and Douglas Fir on soil physical, chemical, and biological properties including SOC and pH, 2) evaluate how these changes impact wheat productivity, 3) determine if biochar impacts last beyond one year, and 4) share results with growers, extension agents, and crop consultants to facilitate adoption of biochar practices.
Biochar will be applied only once on 5 farms within a 100 mile radius in 2019-20 crop-year and evaluated for at least two crop-years to fulfil above objectives. Results will be disseminated through grower-led field tours, extension publications, newspapers, radio, webinar, and journal articles. Based on our preliminary results, biochar increased grain yield by 12%, translating into gross profits of about $94 million. Biochar carryover effects can improve soil health and sustainability of WW-SF system.
Our preliminary studies , showing positive impacts of biochar on SOC and soil pH were obtained from very small experimental plots (5 x 20 ft) that farmers can hardly relate to. For growers to adopt biochar amendment practices, we plan to scale up and evaluate biochar amendments in commercial-sized and commercially managed plots. Five growers, namely Gary Betts, Eric Nelson, Kevin Melville, Virginia Blakelock, and Bob Johns have volunteered to use their land for biochar evaluation (see attached letters of support and cooperation). These growers are interested in improving soil health and sustainable crop production. The main objectives are:
1) To evaluate the impacts of biochar amendments on SOC, pH, active C, mineralizable C and N, bulk density, water holding capacity (WHC), electrical conductivity (EC), cation exchange capacity (CEC), base saturation, N, P, K, Ca, Mg, S, Na, Al, Fe, Mn, and Zn. Available literature indicates that biochar has potential to improve soil physical, chemical, or biological properties and thereby provide promising agronomic effects [14-18].
2) To investigate if soil improvements (Objective 1) due to biochar amendments increase wheat emergence, biomass accumulation, wheat N use efficiency, water use efficiency, and grain yield.
3) To determine if biochar impacts persist beyond the first year. Biochar carbon is resistant to decomposition and is known to last for hundreds of years. We are interested in knowing whether this is also true for associated changes in soil properties and grain yield.
4) To communicate the research and disseminate findings through an effective education and outreach plan.
Biochar will be evaluated in WW-SF systems at five farms located within a 100-mile radius of CBARC in northeast Oregon. Soils are Walla-Walla silt-loam soils (coarse-silty, mixed, mesic Typic Haploxeroll) and precipitation ranges from 12 to 16 inches . In August 2019, biochar will be applied only once to fallow area that will be planted to wheat in the fall of 2019. In August 2020, biochar will be applied only once to the area that was under wheat in 2019 but now in fallow before planting wheat in the fall of 2020. Given budget constraints, we will replicate the study in space (individual farms) and time (years) [22, 23]. There will be three treatments: 1) 0 biochar, 2) 5 ton acre-1 wheat-straw biochar, and 3) 2.5 ton acre-1 Douglas-fir biochar. Different rates of biochar are used in order to supply proportionate amounts of C based on biochar analysis. Biochar will be applied and incorporated within the top 0-15 cm soil depth using a field cultivator. The whole field will be managed based on each farmer’s practice (tillage, fertility, and weed control). Wheat-straw biochar was donated by Ag Energy Solutions Inc. (Spokane, WA) and Douglas-fir biochar was donated by Oregon Biochar Solutions (White City, OR).
Objective 1 (Agricultural professionals):
Before biochar application and after harvest, 20 soil samples will be collected from each plot using a hand probe and composited by 0-15 cm and 15-30 cm depth-intervals, air-dried and ground to pass a 2 mm sieve. Soil water content will be calculated as the difference of field-moist and air-dry soil masses, and bulk density by dividing air-dry soil mass with its volume . Soils will be analyzed for pH and EC electrometrically , water holding capacity using soil-saturation method , SOC and total N by dry combustion ; active C using potassium-permanganate method , inorganic-N (NH4+ and NO3–) colorimetrically , and Bray-P . Soils will be incubated for 24 days at 25ºC and 60% moisture to determine mineralizable C by analyzing CO2-C produced and mineralizable N as the increase in inorganic-N following incubation . Subsamples will be sent to a commercial laboratory to determine NH4(HCO3)-extractable K , KCl-extractable Ca, Mg, Na, and Al , DTPA-extractable S, Fe, Mn, and Zn , and CEC using sodium-acetate method . Base saturation is calculated by diving sum of the bases with CEC . Relationships among soil properties will be evaluated using correlation analysis and regression models, and variation in crop yield parameters (Objective 2) with soil properties will be compared at and across study-sites using appropriate statistical models, multivariate analysis, and intraclass correlation coefficient based analysis [22, 23].
Objective 2 (Agricultural professionals & producers):
Wheat will be planted and managed by producers. Wheat emergence will be determined when 50% of wheat has emerged. Plant population will be determined by counting plants in 10 random 1-m long crop-rows within each plot about two weeks after emergence. At physiological maturity, wheat bundles will be taken from 6 random 1-m quadrats within each plot by cutting wheat at the crown level and weighing to obtain total aboveground dry-matter yield (TDM). Heads will be cut off and counted to determine heads m-2. Heads will then be thrashed and grain weighed to determine total grain weight (GM). Harvest index will be calculated by dividing GM by TDM. The rest of the wheat will be combine-harvested by the producer to obtain wheat grain yield per plot. Subsamples of wheat straw and grain will be ground to pass 0.5 mm sieve and analyzed for tissue-N by dry combustion method . Total crop N uptake is calculated as the summation of grain-N and straw-N . Crop water use efficiency is calculated as the ratio of grain yield and growing-season evapotranspiration . Regression models will be computed to determine the biochar type that increased wheat N and water use efficiency and grain yield.
Objective 3 (Agricultural professionals & producers):
We will continue monitoring SOC, pH, and grain yield in the second crop year. We will solicit more grant funding from WSARE and other funding institutions to continue monitoring these parameters for at least another 3 years after the end of the first grant period. We expect biochar effects to last more than a year given its recalcitrant nature.
Objective 4 (Agricultural Professionals & producers [See Educational Outreach Plan and Materials section].
Single replicates of biochar treatments at the five farms will allow for the evaluation of biochar impacts on soil health and crop productivity and also allow for more general conclusions and more widespread technology transfer to take place than one well replicated experiment at only one farm. Growers learn best from each other and the involvement and cooperation of five growers maximizes the opportunity for technology transfer.
Educational & Outreach Activities
Work conducted to date involved accessing and applying biochar on 7 grower fields. The biochar was obtained from Ag Energy Company in Oregon and applied at 2 tons/acre on fallow land in the summer of last year. Before biochar application, we collected soil samples and sent the samples for a full analyses to establish baseline information on soil nutrients and soil health as a whole. Wheat was planted into the fields with biochar in the fall of last year (2019). We now await the results that will be obtained after wheat harvest in July this year (2020). The experiments will terminate after two seasons but without further applications of biochar.