Abstract

Pyrolysis temperature is a key factor that determines the characteristics of biochar and nutrient availability. However, little is known about how pyrolysis temperature affects phosphorus (P) bioavailability and uptake as well as the underlying mechanism when poultry litter biochar (PB), or its combination with NPK, is applied as a soil amendment on peri-urban cropland. To determine the influence of low and high pyrolysis temperatures on PB and its impact on P bioavailability, uptake and maize yield, we set up a randomized block design field study with the following treatments: (i) No amendment (CK), (ii) NPK mineral fertilization, (iii) biochar pyrolyzed at 300 degrees C (PB300), (iv) biochar pyrolyzed at 600 degrees C (PB600), (v) PB300 + NPK, and (vi) PB600 + NPK. Our results demonstrate that differences in pyrolysis temperatures (300 degrees C) - low and (600 degrees C) - high at which PB was pyrolyzed had no controlling influence on P bioavailability, uptake, soil microbial biomass P, alkaline phosphatase enzyme activity, mycorrhizal fungi components (spores, colonization, glomalin, mycelium density), and maize yield. Similarly, regardless of pyrolysis temperature differences, the combination of PB with NPK (PB300 + NPK and PB600 + NPK) significantly (p 0.05) increased soil P availability by 24% and 13%, uptake 46% and 42%, soil microbial biomass P 63% and 60%, C 8% and 2%, alkaline phosphatase 58% and 37%, and maize yield 37% and 36%, respectively, compared with NPK. PB + NPK, regardless of pyrolysis temperature, retained more P from total P input, which indicates that PB could be a veritable soil amendment technology for mitigating P leaching and enhancing P use efficiency and recycling on peri-urban croplands.