Seeking Solutions

We all need food to survive, and that means someone needs to grow that food. Maintaining healthy crop production and sustaining the environment are constant challenges to modern agriculture. Growing crops and raising livestock removes nutrients from the land and can make the soil unhealthy. Degraded soils also tend to have poor soil structure and are not able to hold water effectively, which can result in erosion and negative impacts to water quality.

Wheat vista
Farmers in Eastern Washington who are lucky enough to use biosolids get healthy, green wheat fields like this one. 

Benefits of biosolids

Given the challenges of sustainable agriculture, biosolids are an ideal soil builder and fertilizer replacement. They are renewable, sustainable, and provide essential plant nutrients to help plants grow greener and increase crop yields. Biosolids can also repair unhealthy soils quickly and effectively. Unlike synthetic fertilizers, biosolids increase organic matter. Organic matter can help suppress plant disease, help beneficial microorganisms like earthworms thrive, improve soil structure, increase soil water holding capacity and reduce erosion. The addition of biosolids can also help to moderate highly alkaline or acidic soil conditions.

 Benefits of biosolids in agriculture

Soil Property

Benefits

Biological

Increases soil micoorganisms

Chemical

Adds macro and micronutrients

 

Increases cation exchange capacity

 

Provides slow release nitrogen and other nutrients

 

Keeps soil pH neutral

 

Increases soil carbon storage

Physical

Helps soil hold water

 

Improves soil structure (tilth)

 

Loosens compacted clay soils

 

Prevents soil erosion

 

Increases water drainage (infiltration)

 

Add air to the soil (aeratess)

 

Provides organic matter

 

Nutrients:

Plants need nutrients to grow. Each growing season, plants take up nutrients from the soil and store it in their leaves and stalks and roots. When we harvest crops, which later end up on our dinner plates, we are removing these nutrients from the farm. In order to maintain fertile land and healthy soil, we must return those nutrients back to the soil, the same way nature would.

Nutrient Cycle

Since biosolids are largely comprised of our own broken down food waste, using them as a fertilizer recycles those nutrients back to the land.

Once applied, the nutrients in biosolids are released slowly as microorganisms break down the organic matter, which provides fertilization as the plants need it. There is no excess of nutrients, so nutrients stay out of local water bodies, which keeps our rivers and streams clean and healthy.

In addition to being environmentally friendly, using biosolids can save farmers a lot of money. Farmers pay for the main plant nutrient, nitrogen, but biosolids also contain all the macro and micronutrients that plants need, so farmers get bonus nutrients for the price of one!

Key Plant Nutrients Provided by a Typical Application of Biosolids

   

lbs/acre

N

Nitrogen (available first year)

112

P

Phosphorus

210

K

Potassium

14

Fe

Iron

182

Mg

Magnesium

33

S

Sulfur (as sulfate)

4.0

B

Boron

0.2

Cu

Copper

6.5

Mo

Molybdenum

0.1

Mn

Manganese

13

Zn

Zinc

7.4

Ca

Calcium

258

 

What's happening?

In the Pacific Northwest, farmers are using biosolids as a fertilizer and soil conditioner for a range of crops. These include: pasture, dryland wheat, canola, hops, alfalfa, corn, grapes, and rangeland grasses. Additionally, gardeners and farmers use Class A biosolids on a wide variety of fruit and vegetables.

References

Sullivan, D.M., C.G. Cogger, and A.I. Bary.  2015.  Fertilizing with biosolids.  Pacific Northwest Extension Publ. 508. Oregon State University Extension, Corvallis, OR.  Available at: https://catalog.extension.oregonstate.edu/sites/catalog/files/project/p…

Biosolids are spread on a field at Boulder Park

In agriculture, biosolids are applied to soil to meet the exact nitrogen needs of the crop. Biosolids are typically applied with calibrated manure spreaders, while liquid biosolids can be sprayed or inserted below the soil surface.

Boulder Park spreader