Horse Manure and Cranberry Fruit Composting Kinetics and Measures of Stability

Abstract

Horse manure and cranberry fruit (5:1) amended with cow manure were composted in duplicate 25 m3 piles for 252 days. Piles were mixed and aerated with a front loader. Temperature was recorded at up to 80 points in each pile; it reached 74°C on day 7, and averaged >45°C through day 157. Oxygen content was measured 7 times at 27 points in each pile up to day 31, and varied from 0.1 to 13%. Volume and total mass reductions achieved were 73% and 71%, respectively, despite the addition of water on 3 occasions. The quality of the product, horse manure cranberry fruit compost (HCC), was examined on samples removed periodically from each pile and analyzed for pH, moisture, volatile solids, total carbon, nitrogen species, chemical oxygen demand of a water extract (COD), cation exchange capacity, and the ratios C/N, COD/N, C/NH4+-N, and COD/NH4+-N. The biodegradation kinetics for dry mass followed a nearly first order decay (k= 0.0187 kg/kg-day). Fecal streptococci, used as an indicator of sanitation, were reduced by >4 log-units. Phytotoxicity tests performed on aqueous compost extracts found decreasing sensitivity for seeds in the order: arabidopsis ≈ lettuce » tomato > wheat > cucumber, corresponding with seed size and food reserve capacity. The germination index (GI) improved with composting time. Multiple regression analysis between GI and physical-chemical parameters revealed that ammonia concentration was the most influential chemical factor affecting (negatively) germination. Samples of composting material taken at 31, 157 and 252 days were assessed as container plant growth media alone and combined with commercial Promix (1:1). Seedlings emerged and grew faster in the Promix and Promix:HCC compared with HCC alone, and plants grew poorest in the young HCC alone.