Changes in Soil Chemistry and Soil Nutrient Stocks after 30 Years of Treated Municipal Wastewater Land Disposal: A Natural Experiment

María Jesús Gutiérrez-Ginés (), Brett H. Robinson, Sky Halford, Izzie Alderton, Vikki Ambrose, Jacqui Horswell and Hamish Lowe
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María Jesús Gutiérrez-Ginés: Institute of Environmental Science and Research (ESR), Christchurch 8041, New Zealand
Brett H. Robinson: School of Physical and Chemical Sciences, University of Canterbury, Christchurch 8041, New Zealand
Sky Halford: Institute of Environmental Science and Research (ESR), Christchurch 8041, New Zealand
Izzie Alderton: Institute of Environmental Science and Research (ESR), Christchurch 8041, New Zealand
Vikki Ambrose: Institute of Environmental Science and Research (ESR), Christchurch 8041, New Zealand
Jacqui Horswell: Institute of Environmental Science and Research (ESR), Christchurch 8041, New Zealand
Hamish Lowe: Lowe Environmental Impact, Palmerston North 4410, New Zealand

Sustainability, 2023, vol. 15, issue 23, 1-14

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.

Keywords: treated effluent; carbon stocks; phosphorus; nitrogen; sodium; pine; pasture; k?nuka (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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