What nutrients do biosolids contain?
Biosolids deliver a full suite of macro- and micronutrients, making it a superior source of plant food over synthetic fertilizers. Specifically they contain large amounts of nitrogen and phosphorus along with low amounts of potassium. Biosolids also have organic matter which provides food for soil microbes, builds soil tilth, and improves overall soil health. The micro-nutrients or significance are zinc, magnesium, manganese, copper, Iron, and molybdenum, which are just as important in maintaining healthy soil to meet your high yield goals.
Why are nutrients important?
During application of biosolids, volatilization (loss of nitrogen to the air) occurs, but with injection of biosolids, the loss is minimized; the remaining ammonia nitrogen is available to plants or converted to nitrate nitrogen.
The available nitrogen in both commercial fertilizer and biosolids could eventually find it’s way into the groundwater, which can cause a health risk to humans and animals if consumed. Strict NMA guidelines have been put in place to limit the amount of nitrogen that can be applied through biosolids. This limit will vary with crop type and application timing.
Phosphorus is a main component in both commercial fertilizers and biosolids. Forty percent of the phosphorous in biosolids is released during the first year after application, the remainder is slowly released over time. Biosolids are most effective when applied to soils that are deficient in phosphorous. Soils are considered deficient when the soil has less than 60mg/l (ppm) of (sodium bicarbonate extractable) phosphorous.
Although excess levels of phosphorous are not toxic to plants, erosion of phosphorous laden soil can lead to surface water quality problems such as excessive algae and weed growth. Legislation in Ontario (Nutrient Management Act) does not permit application of biosolids where soil tests indicate the presence of more than 60 milligrams per litre (ppm) of sodium bicarbonate extractable phosphorous within the top 15 centimeters of soil.
What about organic matter?
What are the fertilizer equivalencies of nutrients in biosolids?
Only a portion of the nutrients applied are available within the first year. Below is a calculated average of what the benefits of biosolids may look like on a typical field within the first year of biosolids application:
|Nutrient||Total Amount from Biosolids Application||Available in First Year of Application||Typical Requirements for a Crop of Corn|
|Nitrogen (TKN, NH3, etc.)||kg/ha||330||132||135|