Chemical and Physical Changes Following Co-Composting of Beef Cattle Feedlot Manure with Phosphogypsum
2005
Zvomuya, Francis | Larney, Francis J. | Nichol, Connie K. | Olson, Andrew F. | Miller, Jim J. | DeMaere, Paul R.
Nitrogen (N) loss during beef cattle (Bos taurus) feedlot manure composting may contribute to greenhouse gas emissions and increase ammonia (NH₃) in the atmosphere while decreasing the fertilizer value of the final compost. Phosphogypsum (PG) is an acidic by-product of phosphorus (P) fertilizer manufacture and large stockpiles currently exist in Alberta. This experiment examined co-composting of PG (at rates of 0, 40, 70, and 140 kg PG Mg⁻¹ manure plus PG dry weight) with manure from feedlot pens bedded with straw or wood chips. During the 99-d composting period, PG addition reduced total nitrogen (TN) loss by 0.11% for each 1 kg Mg⁻¹ increment in PG rate. Available N at the end of composting was significantly higher for wood chip–bedded (2180 mg kg⁻¹) than straw-bedded manure treatments (1820 mg kg⁻¹). Total sulfur (TS) concentration in the final compost increased by 0.19 g kg⁻¹ for each 1 kg Mg⁻¹ increment in PG rate from 5.2 g TS kg⁻¹ without PG addition. Phosphogypsum (1.6 g kg⁻¹ P) addition had no significant effect on total phosphorus (TP) concentration of the final composts. Results from this study demonstrate the potential of PG addition to reduce overall N losses during composting. The accompanying increase in TS content has implications for use of the end-product on sulfur-deficient soils. Co-composting feedlot manure with PG may provide an inexpensive and technologically straightforward solution for managing and improving the nutrient composition of composted cattle manure.
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