New Research Shows How Pine Slash Can Improve Soil Quality

Pine slash could be chipped and used to rehabilitate soil.

Mon 24 Jul 23


New research from the University of Canterbury suggests that pine slash could be chipped and used to rehabilitate soil.

Te Whare Wānanga o Waitaha | University of Canterbury Master’s student Mingyuan (Kathy) Liu has been investigating using pine waste mixed with urea fertiliser on silt-covered soils from Canterbury and Gisborne. 

She found combining pine waste with urea is the most effective for plant growth, compared to urea alone or using compost or other organic matter on the soils.

The study found that pine slash – a waste product from commercial forestry – can be used to fix silt-covered soils.

As Cyclone Gabrielle swathed through New Zealand’s central North Island, trees snapped like twigs. The cyclone put a renewed focus on the environmental damage caused by pine slash.

“We’ve looked at blending pine waste into finer sawdust particles and mixing them with the soil and some fertiliser to make the soil more porous – better for water drainage and for plants to grow,” Liu says. 

The results, limited to the campus greenhouse, show a significant increase in soil fertility, with testing in the field now required.

Oats, a popular green manure, were planted in soil treated with pine sawdust and fertiliser.

“Oats are really helpful for stabilisation of the soil structure,” Liu says. 

“We could immediately see the difference in the crops grown in pine sawdust mixed into the soil.”

Liu’s Supervisor, UC Science Professor Brett Robinson, says preliminary results are exciting.

“Pine slash is a current issue facing New Zealand and the rest of the world.” 

“To date, we know of no other reports detailing the rehabilitation of flood-deposited sediment using pine waste.” 

We hope to take it to the next stage – field testing – soon,” he says.

Different levels of fertility were observed across different plantings. (Photo Credit: University of Canterbury)

The work collaborates with Dr Maria Jesus Gutierrez-Gines, a science leader at ESR (Institute of Environmental Science and Research) who has co-supervised Liu’s research.

ESR has supported the research by providing technical time and analysis and organising the sediment delivery from flood-affected Gisborne.

Professor Robinson says pine contains substances known to inhibit plant growth. 

Still, when applied in the trials to work on the structure of sediment or silt, it created the capacity for the soil to retain nutrients.

“Essentially, it acts like a sponge and breaks down to humus which is beneficial to the soil.”

The role of forests during natural disasters

Last month, Wood Central reported that forests are nature’s sponges during significant rain events, absorbing nearly 60% of rainfall, according to new research provided by New Zealand-based Scion.

This absorption process prevents immediate water flow across the terrain and into waterways, significantly reducing potential downstream flooding.

The high-resolution data that led to these revelations were collected from Mahurangi Forest near Auckland during major rain events, including Cyclone Gabrielle.

New research from Scion observed how forests absorb and store water during major weather events. (Image Credit: Scion Research)

Backed by the NZ Ministry of Business, Innovation and Employment (MBIE), this project deploys over 1,700 sensors across ten national forests to capture data at five-minute intervals, offering unprecedented insights into forest hydrology.

Dr Dean Meason, a leading scientist at Scion, is leading the project.

Renowned globally for his work as a tree ecophysiologist, Dr Meason aims to predict and optimise water use and supply in planted forests through the programme.

Dr Meason believes the approach will unveil secrets about how water moves and is stored in catchments.

“Our field sensors, meteorological and hydrological equipment network has been collecting data for about two years now,” he said.


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