A field trial to determine the effect of the land application of treated municipal wastewater onto selected NZ-native plants on Banks Peninsula Alexandra Meister1, Maria Jesus Gutierrez-Gines2 and Brett Robinson1* 1School of Physical and Chemical Sciences, University of Canterbury, 20 Kirkwood Ave, Christchurch 8041 2Institute of Environmental Science and Research (ESR), 27 Creyke Rd, Christchurch 8041 *
[email protected] Executive Summary • The application of Treated Municipal Wastewater (TMW) on NZ-native vegetation is a management option under consideration for towns on Banks Peninsula and elsewhere. There is little information on the effect of TMW on the growth of NZ-native plants or the fluxes of nutrients or contaminants in the underlying soil. • In July 2015, 1350 native species were planted onto a 20 m x 55 m plot on Piper’s Valley Road, Duvauchelle, Banks Peninsula. The plants were arranged into 27 blocks (4.5 m x 4 m), with 12 of the blocks receiving TMW. There were three NZ-native vegetation types tested: Type 1 (Phormium tenax, Phormium colensoi, Cordyline australis, Griselinia littoralis, Pittosporum eugenioides), Type 2 (Leptospermum scoparium, Kunzea robusta) and Type 3 (Coprosma robusta, Pseudopanax arboreus, Podocarpus laetus, Olearia paniculata). Irrigation with TMW at a rate of 1000 mm/yr started in January 2016. • In October/November 2018 forty soil pits were opened and samples taken from five depths (0-5, 15, 30, 45 and 60 cm). From January 2016 to the time of sampling, the soils received a total of 3400 mm of TMW. Soils were analysed for pH, total elements, and soluble (‘phytoavailable’) fractions of key nutrients and contaminants (ammonium, nitrate, Olsen phosphorus, heavy metals).