Precision nutrient management for maximum productivity

IO1: Commercial forestry and ecosystem services

Getting the right balance between supply and demand is at the heart of any successful business. The same applies when growing trees.

With many of New Zealand’s planted radiata pine forests already in their third consecutive rotation, and some entering their fourth, Scion has been investigating the balance between nutrient supply and demand as a rotation develops, to determine if current levels of productivity can be sustained, or even improved, in future rotations.

Scion’s precision nutrient management model, NuBalM, has been developed for this purpose.

NuBalM enables forest growers to predict the supply of nutrients to their planted forest estate, over multiple rotations. Soil Scientist Dr Simeon Smaill says that with a third of the country’s planted forest soils classified as low nutrient soils, increased fertiliser use is a clear option to boost productivity and New Zealand’s forest export earnings.

“Predicting the productivity gains from fertiliser use in planted forests is complicated, so there has been a strong industry demand for this type of model,” says Simeon. “NuBalM has been incorporated into our forest growth model, Forecaster, so that growers can access forest growth data and set nutritional targets based on demand.

“NuBalM will provide growers with vital information about nutrient flux throughout a rotation. It can also be used to predict the environmental outcomes of different management practices, and is being developed as a robust regulatory tool for forest managers and regional councils. This will enable a new level of precision in forest nutrient management.”

Simeon has been working on the model since 2006, expanding on a concept first introduced in 1994 to match nutrient supply with demand over the life of a rotation. NuBalM was introduced to the forestry sector in 2009, with grower interest snowballing in recent years.

Scion’s Growing Confidence in Forestry’s Future programme, launched in 2013 to double the productivity of New Zealand’s planted forests, presented the opportunity to expand the model further. This year has seen improvements to the nitrogen cycling module and the addition of a new module to predict phosphorus demand.

In 2015, Scion received further funding from the Forest Growers Levy Trust to develop a roadmap, in consultation with the forestry sector that sets the direction for further improvements to the NuBalM platform. The roadmap was completed in March 2016, along with the addition of a water balance module designed to assess the potential for environmental risk. The FGLT is funding further improvements to NuBalM over the next two years.

The NuBalM model is currently being used to evaluate end-of-rotation data from long-term productivity trials, and pre-harvest data from an accelerator trial to establish the nutrient requirements needed to boost productivity up to a specified target.

The future of NuBalM

Future enhancements to NuBalM have already been identified in the roadmap, the most critical being the need to reduce uncertainty around the growth response to nitrogen fertiliser. Other enhancements will include predictions of nitrogen fixation by weed species, and the addition of other nutrient modules. The ability to predict how management decisions will influence nitrogen leaching is considered a key regulatory issue for stakeholders.

Collaborators / Partners: Kaingaroa Timberlands, NuBalM industry steering group
Investment: MBIE, FGLT