Using calcium silicate nanoparticles to reduce phosphorus solubility in poultry litter treated with alum or sodium...

Treating poultry litter with alum is a best management practice (BMP) used to reduce ammonia (NH₃) volatilization and phosphorus (P) runoff and leaching. However, recently we have observed that alum additions to litter have not always reduced soluble reactive phosphorus (SRP). The objectives of this research were (1) to determine why alum additions to litter occasionally fail to reduce SRP and (2) to determine if aluminum (Al), calcium (Ca), and/or iron (Fe) nanoparticles applied alone or in combination with dry acids used for NH₃ control (alum or sodium bisulfate) would reduce SRP in litter. Five lab studies were conducted. Results showed when litter had previously been treated with sodium bisulfate was treated with alum, it increased SRP, possibly due to the formation of sodium alunite. Applications of sodium bisulfate alone to poultry litter also increased SRP. While the addition of Al and Fe nanoparticles to litter had relatively little effect on SRP when applied alone or in combination with alum or sodium bisulfate, the addition of a calcium silicate based nanoparticle had a synergistic effect on reducing SRP when applied with alum or sodium bisulfate. When TPX was applied with sodium bisulfate at rates of 1.25%, 2.5%, and 5%, the SRP decreased from 3410 mg P kg^-1 to 1220, 541, and 233 mg P kg^-1 litter, respectively. However, TPX increased litter pH, which may negatively affect the efficacy of alum and poultry litter treatment on reducing NH₃ emissions, indicating more research is needed on this practice to determine if it is a cost-effective BMP for reducing P runoff.