Abstract:
The objectives of this study were to evaluate (1)
the fertilizer potential of bone char, (2) the effects of
wood biochar on plant-available phosphorus (P), and (3)
the role of root-mycorrhizae-biochar interactions in
plant P acquisition from a P-fixing soil.
Methods Incubation and pot experiments were conducted with a P-fixing soil and maize with or without root
hairs and arbuscular mycorrhizae (AM) inoculation.
Olsen-, resin-P and plant P accumulation were used to
estimate P availability from bone char, co-pyrolyzed
bone char-wood biochar, and separate bone char and
wood biochar additions produced at 60, 350 and 750 °C,
and Triple Superphosphate (TSP).
Results Maize inoculated with AM showed similar P
accumulation when fertilized with either 750 °C bone
char or TSP. Pyrolyzing bone did not increase extractable P in soil in comparison to unpyrolyzed bone, apart
from a 67 % increase in resin-extractable P after additions of bone char pyrolyzed at 350 °C. Despite greater
Olsen-P extractability, co-pyrolysis of bone with wood
reduced maize P uptake. Wood biochars reduced resin-P
from bone char by 14–26 %, whereas oven-dried wood
increased resin-P by 23 %.
Conclusions Bone char is an effective P fertilizer, especially if root-AM interactions are simultaneously considered. Biochar influences plant access to soil P and
requires careful management to improve P availability.
