Affiliation:
1. Institute of Environmental Science and Research (ESR), Christchurch 8041, New Zealand
2. School of Physical and Chemical Sciences, University of Canterbury, Christchurch 8041, New Zealand
3. Lowe Environmental Impact, Palmerston North 4410, New Zealand
Abstract
The benefits and risks of irrigation with treated municipal wastewater (TMW) on soil quality and crop production have been largely investigated. However, there is a lack of knowledge on the effect of plant species on the interaction between soil quality and TMW. We leveraged a natural experiment investigating the effect of 30 years of TMW irrigation at a rate of 4 m y−1 (eq. 1860 kg N ha−1 y−1, and 264 kg P ha−1 y−1) on a sandy soil under pine plantation and pasture, compared with soil under New Zealand native Kunzea robusta. There was a consistent increase in soil P with irrigation under both pasture (Olsen P in topsoil 40 mg kg−1 vs. 74 mg kg−1) and pine (18 mg kg−1 vs. 87 mg kg−1), which was significant down to 2 m deep. The pH, electrical conductivity, total organic C and N, inorganic N and Na were affected by both irrigation and vegetation type. Beyond P soil accumulation, there was no evidence of soil degradation by Na or trace element accumulation. Estimations of nutrient mass balance indicated that 80% and 60% of the total applied P was lost under pine and pasture, respectively. This percentage increased to 96% and 83% for N, respectively. Although plant species had a significant effect on soil quality and N and P losses from TMW-irrigated areas, adjusting irrigation rates to levels that can be managed by plants is the only way to design sustainable TMW irrigation schemes.
Funder
Ministry for the Environment of New Zealand’s Freshwater Improvement Fund
Ministry of Business, Innovation and Employment
Subject
Management, Monitoring, Policy and Law,Renewable Energy, Sustainability and the Environment,Geography, Planning and Development,Building and Construction