Biochar Selection Tool

How to Use This Tool

Progress through the tabs on the top bar to select the best type of biochar and amendment rate:

  • First, enter data about your soil's properties.
  • Read about potential deficiencies in your soil that biochar could ameliorate.
  • Based on your soil's needs, select goals you would like to achieve through biochar amendment.
  • View the PNW biochars in our database that best meet your goals.
  • Finally, determine the biochar amendment rate that most closely meets your goals.

Step 1: Provide as much information as possible from your soil testing or the soil explorer map.

Suggestion: populate data from soil map first and then edit to match test results.



Exchangable Concentrations



Step 2: Read about the test results to determine your soil's limitations.

Click through each soil property listed in the sidebar.


Carbon, in the form of soil organic matter, is an essential component of soil health that helps to prevent erosion and provides essential functions including soil water storage, fertility, and biological activity.

Soil organic matter content is typically between 0.5-5% mass in most soils.

Soils with a history of tillage often have lower organic matter content than uncultivated or reduced-tillage soils. Soils with organic matter contents >10% are referred to as organic soils, as their properties are dominated by organic matter rather than by mineral soil.

Your soil level is highlighted in the table below.

Building Soil Carbon

Soil organic matter content can be increased by leaving plant residues, by applying biochar, compost, or other types of organic matter, and by reducing tillage.

Note that very high organic matter contents can present challenges for crop growth. In organic soils, you may need to provide mineral amendments to account for the reduced mineral content of the soil.


Below are fertilizer recommendations published by Oregon State University for some field and vegetable crops. Select a crop to see whether you would benefit from adding nutrients from biochar or other sources. Biochars can be a source for phosphorous, potassium, sulfur, and magnesium.

Biochars generally do not provide nitrogen, and due to their high carbon content may reduce nitrogen availability in soil. It may be necessary to provide additional nitrogen when applying biochar.

Note: These recommendations are shown for illustrative purposes only. You should also consult a local extension office or farm advisor for more detailed recommendations.

Use the tables below to see how much of each nutrient is needed for the crop you chose. Your soil level is highlighted.



Soil Acidity

Below are tables showing lime application rates for Western and Eastern Oregon, based on the SMP buffer test.

Additional liming information for the inland PNW can be found through WSU Extension.

Reference: Table 3 in 'Applying Lime to Raise Soil pH for Crop Production (Western Oregon) (2013) N.P. Anderson et al., OSU Extension Publication EM 9057

Reference: Table 4 in 'Eastern Oregon Liming Guide (2013) D.M. Sullivan et al., OSU Extension Publication EM 9060

Soil Moisture

Soil moisture properties are determined by organic matter content and by soil texture. Soil texture refers to the size of soil particles. Soils with an abundance of large particles have more large pores, and drain water more readily than soils with an abundance of small particles. In contrast, soils with an abundance of small particles and small pores tend to evaporate more slowly and have higher water retention than soils with large particles.

Soil particles are divided into 3 size classes:

  • sand (>2000 micrometers)
  • silt (2-50 micrometers)
  • and clay (<2 micrometers).

A loam refers to a soil that is not dominated by any one particle size class, but has relatively equal influences from sand, silt, and clay particles. Loam soils have a balance of both relatively good drainage and water retention.

The table below shows representative data for the amount of water contained in soils when they are well-drained, ordered from most coarse to most fine soil textures.

Note that available water content is generally higher in soils with finer particles, because fine-textured soils evaporate and drain water more slowly.

Adding sources of organic matter, such as biochar, can improve water drainage or water retention. Choose a biochar with large particles to increase drainage, and one with a lot of fine particles to increase retention.

Step 3: Choose three goals for applying biochar.

Step 4: Read about which biochars can meet your goals.

Click through each goal in the sidebar. See more about these biochars using the Biochar Property Explorer.

Putting it together

A single biochar may not meet all of your goals. Here is a summary of how the biochars in our database meet your needs.

How do you choose? The ranking suggested below is based on assigning 3 points to biochars that meet your first priority, 2 points to those meeting your second priority, and 1 point to those meeting your third priority.

Step 5: Determine an appropriate amendment rate.

Estimated Carbon, Fertility, and Liming Benefits

Select a biochar and use the table below to see estimated benefits at several amendment rates.

Visit the next tab to compare the benefits provided to your crop requirements.

Stable carbon, nutrients, and lime equivalents provided by this biochar.

Soil Conditioning Impacts

The benefits shown in the table above relate only to readily-measurable chemical properties of biochars. Biochar is also considered to be a soil conditioner, meaning it enhances soil nutrient retention gradually over time. These effects, as well as changes in soil biology that may result from biochar addition, are inconsistent and more difficult to predict. It is also not possible to predict the synergistic benefits plants may experience from simultaneous changes in soil pH, fertility, moisture retention, and microbial activity.

A sound approach for selecting an amendment rate is to base your decision on readily-measurable properties. This will help to ensure predictable benefits from biochar, particularly in the first year following application.

Meeting Anticipated Crop Requirements

Here are estimates for the percentage of fertilizer requirements that could be met with this biochar amendment.

'Not required' indicates that your test levels are high or the crop does not require additions of that nutrient.

How to Use this Information

You will probably find that most biochars meets only a small fraction of crop nutrient requirements. Although there are some exceptions, most biochars have low fertility value, and have to be blended with compost or other fertility sources.

Use this information to guide your experimentation with biochar. These tables can help you anticipate the additional nutrients you will need to add with biochar, and to estimate how soil pH, carbon content, and water may also be impacted. Although every biochar has somewhat unique properties, the biochars shown here should help you anticipate the range of benefits you might expect.