Land application of effluent has become a recognized, environmentally responsible choice for wastewater treatment. In New Zealand, effluent is often applied to the radiata pine plantation environment, as contaminants are removed from the food chain, and plantations can benefit from nutrient additions.

A large lysimeter research facility (LLRF) was set up in Whakarewarewa Forest, Rotorua, New Zealand, to develop an understanding of wastewater irrigation issues in forest ecosystems. The facility had 36 plots (21 in volcanic soil and 15 in dune sand soil) with 5m × 5m area each, and with 9 trees in each plot. Secondary (containing 15-20 g N m^-3and containing 3-6 g P m^-3 in average) and tertiary (containing 6-11 g N m^-3 and containing 3-6 g P m^-3 in average) treated effluents were irrigated for over 3 years at 0, 30 and 60 mm/week.

Tree growth and foliar nutrition are often used as indicators of the soil chemical condition in New Zealand forests, and are the basis for determining factors for fertilisation decisions. We analysed three years of growth and nutrition for all of the LLRF treatments. The effects of soil type, and effluent addition levels produced significant responses in tree growth and changes in foliar nutrition, predominantly in the sand plots, where significant increases in growth were observed with increases in foliar N, P, and several other nutrients. Depression of foliar Mg was observed in the volcanic soil treatments. The study highlights the effects that effluent quality, loading rate, and soil have on Pinus radiata growth and nutrition.