RYEGRASS UTILIZATION OF NUTRIENTS RELEASED FROM COMPOSTED BIOSOLIDS AND COW MANURE

Use of composts as soil amendments to enhance crop growth requires a k nowledge of rates and amounts of nutrients released. A greenhouse stud y was conducted using ryegrass (Lolium perenne L.) as a test plant to evaluate this release from composts. The experimental design consisted of four blocked replicates in a complete factorial with two types of compost (wastewater treatment plant biosolids and cow manure), four ap plication rates (1, 2, 5 and 10 percent of weight of sand), and three fertilizer treatments (0, 100 mg N/kg mixture, and 100 mg P/kg mixture ). Rye-grass top growth was harvested after 21 days. The regrowth was harvested three additional times. Roots were recovered after the fourt h harvest. Total N uptake was significantly and positively affected by the total amount of N supplied by the compost or compost plus N ferti lizer (r(2) values ranged from 0.992 to 0.999). Initial N uptake depen ded on the mineral N concentration in the compost and was higher from biosolids than from cow manure compost. Biosolids compost contained 10 times more mineral N and this N was primarily taken up in the first t wo harvests. Cow manure compost, however, provided N gradually over th e entire 84 day test. In addition to N, both composts also supplied P, K, and other major and minor nutrients essential for plant growth.