Effects of Different Phosphogypsum Addition Amounts on Cow Manure Composting Maturity and Nitrogen Loss

Puepose To study the effects of different phosphogypsum addition amounts on cow manure composting maturity and nitrogen loss.

Methods Dry and wet separated cow manure was used as the composting material, 0%, 3%, 6%, and 9% phosphogypsum was added respectively, and the composting process was conducted using a windrow composting technique for 35 days, monitoring the changes in temperature, pH value, seed germination index, carbon-to-nitrogen ratio (C/N value), nitrate nitrogen content, ammonium nitrogen content, ammonia release rate, and nitrogen loss rate during composting.

Results The addition of 3% to 9% phosphogypsum shortened the time for the temperature of cow manure compost to rise above 50 °C by 3 to 6 days, increased the maximum temperature by 1 to 4°C, and extended the time of the temperature remained above 50 °C by 0 to 3 days. The pH value of the compost products decreased by 3.02% to 7.95%, the C/N value decreased by 9.57% to 16.50%, the seed germination index increased by 9.27% to 22.17%, and the nitrate nitrogen content increased by 7.04% to 16.92%. The ammonia release rate was reduced by 15.13% to 37.87%, and the total nitrogen loss rate decreased by 6.53% to 15.36%. The highest nitrogen retention efficiency was observed when the phosphogypsum addition was 6%.

Conclusion In the windrow composting of cow manure, the addition of 3% to 6% phosphogypsum not only improves the composting maturity and product quality, but also effectively reduces ammonia release during composting. This study provides theoretical support for further resource utilization of phosphogypsum and optimization of cow manure composting technology.