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Title: PHOSPHORUS LEACHING POTENTIAL FROM COMPOST AMENDMENTS IN A CARBONIC SOIL

Author
item Reed, Stewart
item SHINDE, DILIP - EVERGLADES NATL PARK
item KONOMI, KENICHIRO - FORMER FIU
item JAYACHANDRAN, KRISHNASWAMY - FL INTL UNIV
item NKEDI-KIZZA, PETER - UNIV OF FLORIDA
item Savabi, M

Submitted to: American Society of Agronomy Meetings
Publication Type: Other
Publication Acceptance Date: 11/12/2006
Publication Date: 11/12/2006
Citation: Reed, S.T., Shinde, D., Konomi, K., Jayachandran, K., Nkedi-Kizza, P., Savabi, M.R. 2006. Phosphorus leaching potential from compost amendments in a carbonic soil. American Society of Agronomy Meetings.

Interpretive Summary: Composts are applied to carbonatic soils (soils formed from limestone and small round grains of calcium carbonate) in south Florida to improve their physical characteristics and increase water retention. Blends of sludge and municipal solid waste are often combined to increase the nutrient content of the compost. However, the high phosphorus (P) content of some compost has led to concerns about the potential for P movement into shallow ground water. Column studies were conducted to determine the potential for P leaching in compost-amended soil. Bedminster (Bed) was the most suitable compost in terms of a lower potential for P leaching. A sorption study indicated that, Bed only slightly enhanced P sorption in the amended soil. Bromide breakthrough curves (BTCs) showed the presence of physical non-equilibrium processes in the porous media indicating that water did not flow downward in a even, direct pathway. Each compost-amended soil demonstrated a slight decrease in P leaching at 1 pore volume of rainfall (one pore volume is the volume of rain needed to completely fill all the air space in a given volume of soil). The high P content of the composts made it unlikely that additions of these materials to soil would improve P sorption capacity. However, Bed and Clean Organic Waste (COW) did not significantly increase P leaching above that of the soil. Caution should be exercised when applying these composts since materials themselves contain an enormous amount of phosphorus that could be eventually transported into the groundwater.

Technical Abstract: Composts are applied to carbonatic soils in south Florida to improve their physical characteristics and increase water retention. Blends of biosolids and municipal waste are often combined to increase the nutrient content of the compost. However, the high P content of some compost has led to concerns about the potential for P movement into shallow ground water. Studies were conducted to determine the potential for P leaching in soil amended with municipal solid waste and biosolids (Bio), clean organic waste (COW) and Bedminster (Bed) composts. Bed was the most suitable of the composts used in terms of a lower potential for P leaching as a result of enhanced P sorption in the amended soil. Each compost-amended soil demonstrated a slight decrease in P leaching at 1 pore volume (PV) after simulated rainfall (21 cm). Pore volume was defined as the total volume in a column less the volume of solids. The high P content of the composts made it unlikely that additions of these materials to soil would improve P sorption capacity. However, Bed and COW did not significantly increase P leaching above that of the soil. Caution should be exercised when applying these composts since materials themselves contain an enormous amount of phosphorus that could be eventually transported into the groundwater.