Phosphorus Uptake By Potato (Solanum tuberosum) from Fertilizers Recovered from Anaerobic Digestion.

Field experiments were conducted in the Columbia Basin of Washington to assess the yield of potato (Solanum tuberosum) in response to phosphorus enriched materials recovered from anaerobic digestion of manure. The treatments were four rates (0, 56, 112 and 168 kg P₂O₅ ha^-1) of P from five sources: three recovered from anaerobic digesters (AD); AD-dairy P-enriched solids (ADD); AD centrifuged poultry solids (ADP); and AD dairy struvite (ADS) compared to a commercial poultry fertilizer (PBP); a mono-ammonium phosphate (MAP) and a non-amended control (No-P). P fertilized treatments had higher total yields than the No-P treatment. Increasing application rates of P did not affect tuber yield. Phosphorus P source and application rate had significant effects on petiole P concentrations. Incremental increases in petiole P ranged 300 – 500 mg kg^-1 tissue with each application rate increase for MAP and ADS. Tuber yields among P fertilizers and rates of P application were not significantly different but were different between years and greater than the No-P treatment, averaging 2 Mg ha^-1 and 10 Mg ha^-1 higher than the No-P treatment. Tuber size distribution in 2014 showed a significant shift from smaller tubers < 170 g to the 285+ g tuber classes. The P recovery efficiency averaged 42% among treatments recieving 56 kg P₂O₅ ha^-1 and declined to 22% for higher rates of ADS, ADD, and MAP. Recoveries were lowest for poultry derived materials (ADP, PBP), ranging 20 to 30%.  Our results indicate that all P fertilizer sources performed similarly when equal rates were applied.