Conclusions

Repeated manure use on agricultural fields at agronomic N rates has created a redistribution of P in soils which increases the risk of P contribution to surface waters. If manure use continues at current rates, refined prescriptions will be needed to reduce and prevent P losses from deteriorating surface water quality. Gypsum use as a soil amendment seems promising as a BMP to reduce P losses from agricultural fields. The current study provides valuable information needed to fine-tune current prescriptions for BMPs needed to maintain environmental sustainability.

 

Recommendations

Where P application rate or P application method will create an unacceptable risk for runoff according to the Alabama P index, either agricultural or FGD gypsum may be used as a BMP at the time of P application. A recommended rate of 2-ton acre¹ is needed to obtain the greatest benefit of reducing the threat of P loss from pastures fertilized with poultry litter.