I listened to the RNZ rural news podcast linked below back in July 2012 which includes a review of a water quality related project around Lake Rotorua. 2:30min in is a discussion on the “P Project”. Their project does seem to have some links to keyline plowing.
http://www.boprc.govt.nz/environment/water/rotorua-lakes/lake-water-quality/
No reference to biochar in following 2010 report (but hardly surprising)…
http://www.boprc.govt.nz/media/99964/the_efficacy_of_strategies_to_mitigate_the_loss_of_phosphorus_from_pastoral_land_use_in_the_catchment_of_lake_rotorua.pdf