Using nutrient-rich wastes in plant nurseries, forestry and native plantings — Fact sheet

This research looks at the feasibility of using nutrient-rich wastes in plant nurseries, and for managing plantings of tree species. The research includes exotic and indigenous (native) forestry species.

What are nutrient-rich wastes?

Nutrient-rich wastes include:

  • animal waste from milking sheds
  • municipal wastewater. This is water used in household or business bathrooms, kitchens or laundries that is treated at a water treatment plant
  • biosolids (treated human waste)
  • plant waste — including the leftovers from forest harvesting to lawn clippings.
  • dairy and meat processing wastes.

They are rich in nutrients such as nitrogen, phosphorus, potassium and/or organic matter.

Uses

Nutrient-rich wastes can be used:

  • for irrigation or fertigation in nurseries or planted areas (wastewater)
  • as planting mix supplements (unprocessed or minimally processed sludges, slurries and solids)
  • as planting mix (composted or processed slurries or solids).

Benefits

There are benefits to using nutrient-rich wastes.

Using municipal wastewater can decrease the amount of clean water needed. It also provides an enriched water supply for nurseries.

Adding slurries, sludges or solid waste to soil helps it hold more water. The wastes improve the soil’s structure and biological activity. They also provide nutrients. These benefits encourage productivity.

The use of nutrient-rich wastes in forestry and nurseries supports New Zealand’s move to a circular economy.

Risks

The potential benefits need to be balanced against the management of risks. Potential health, safety and environmental risks depend on the type of waste used. Most risks can be managed by:

  • treating the waste
  • managing the rate and method the waste is applied.

There can be social and cultural issues, in particular with the use of human waste (biosolids). These issues can be dealt with through appropriate engagement processes.

nutrient wastes report
Tip
Whenever you are introducing potentially hazardous waste to your operations, make sure all regulations are followed and risk assessments have been carried out.

Using nutrient-rich wastes in nurseries

Nutrient-rich wastewater is beneficial for nurseries. Water access is critical for nurseries. The wastewater decreases the amount of clean water used and provides an enriched water supply.

Using solid or slurry waste can reduce the need for fertilisers or substrate.

Being near to a wastewater plant is an important factor. This study found 6 nurseries servicing the commercial forestry sector within 5km of a waste processing plant.

Potential uses of nutrient-rich wastes in plant nurseries

Waste Use Incentive for use
Wastewater: municipal,
dairy factory,
meat processing,
food processing
Irrigation Beneficial in water-deficient areas.
Avoids water stress.
Decreases amount of clean water needed.
Re-uses wastewater.
Sludges/solid materials Supplements to seedling beds Helps soil hold more water.
Improves soil structure.
Improves soil biological activity.
Adds slow-release nutrients.
Composted/modified sludges/solid materials Planting mix Improves soil biological activity.
Re-uses waste materials/offsets use of new materials.
Reduces need for inorganic fertilisers.
Waste
Wastewater: municipal,
dairy factory,
meat processing,
food processing
Use
Irrigation
Incentive for use
Beneficial in water-deficient areas.
Avoids water stress.
Decreases amount of clean water needed.
Re-uses wastewater.
Waste
Sludges/solid materials
Use
Supplements to seedling beds
Incentive for use
Helps soil hold more water.
Improves soil structure.
Improves soil biological activity.
Adds slow-release nutrients.
Waste
Composted/modified sludges/solid materials
Use
Planting mix
Incentive for use
Improves soil biological activity.
Re-uses waste materials/offsets use of new materials.
Reduces need for inorganic fertilisers.

Using nutrient-rich wastes in forestry plantings

The main opportunity for using nutrient-rich wastes in forestry is to increase production. The wastes can cut rotation time (the number of years between planting and harvesting) with little loss to wood quality.

Applying wastes to commercial forestry sites has lots of potential. About 260,000 hectares of commercial forestry is on sandy soils. These sites are within 20km of a processing plant that produces nutrient-rich waste. Sandy soils have the potential to benefit most from the waste.

Potential uses of nutrient-rich wastes in commercial forestry

Waste Use Incentive for use
Sludges/solid materials Site preparation Adds slow-release nutrients for growth promotion.
Helps soil hold more water.
Improves soil structure.
Wastewater: municipal,
dairy factory
Irrigation Avoids water stress.
Decreases the amount of clean water needed.
Reduces discharge to aquatic systems.
Sludges In-forest
application
Adding slower-release nutrients helps deficiencies and promotes growth.
Waste
Sludges/solid materials
Use
Site preparation
Incentive for use
Adds slow-release nutrients for growth promotion.
Helps soil hold more water.
Improves soil structure.
Waste
Wastewater: municipal,
dairy factory
Use
Irrigation
Incentive for use
Avoids water stress.
Decreases the amount of clean water needed.
Reduces discharge to aquatic systems.
Waste
Sludges
Use
In-forest
application
Incentive for use
Adding slower-release nutrients helps deficiencies and promotes growth.

Using nutrient-rich wastes for native plantings

Using nutrient-rich wastes for native plantings can increase growth rates resulting in quicker canopy closure. This helps survival rates too.

Other wastes like woody debris are useful for managing weeds and excluding browsing animals.

Native plantings on poor quality soils will get the most benefits from nutrient rich wastes, especially when the aim is to bring back the native ecosystem. Poor quality soils have poor structure and little organic matter and nutrients. The natural humus layers and woody materials in the soil are gone.

New plantings need water to survive. Using tankers to apply nutrient-rich wastewater reduces the need for clean water.

Potential uses of nutrient-rich wastes for native plantings

Waste Use Incentive for use
Woody debris,
woody mulches
Site preparation Protects microsites.
Prevents erosion.
Saves water in dry/warm sites.
Suppresses weeds.
Stops browsing animals (deer, hares, rabbits).
Enhances nutrition when mixed with compost.
Sludges and modified sludges Site preparation Improves degraded soils and builds soils.
Helps soil hold more water.
Improves soil structure.
Improves organic matter.
Adds slow-release nutrients.
Wastewater:
municipal
Irrigation after planting Decreases amount of clean water needed.
Waste
Woody debris,
woody mulches
Use
Site preparation
Incentive for use
Protects microsites.
Prevents erosion.
Saves water in dry/warm sites.
Suppresses weeds.
Stops browsing animals (deer, hares, rabbits).
Enhances nutrition when mixed with compost.
Waste
Sludges and modified sludges
Use
Site preparation
Incentive for use
Improves degraded soils and builds soils.
Helps soil hold more water.
Improves soil structure.
Improves organic matter.
Adds slow-release nutrients.
Waste
Wastewater:
municipal
Use
Irrigation after planting
Incentive for use
Decreases amount of clean water needed.

Next steps

  • Form partnerships between nutrient-rich waste producers and nurseries, landscape suppliers (where these provide planting mix to nurseries) or forestry companies. Build knowledge between providers and recipients of each other’s requirements. Requirements could include composition of wastes or supply needs.
  • Gather information on the nutrient qualities of different nutrient-rich wastes from producers. Evaluate how suitable they are for different purposes, for example as supplements added to planting mix.
  • Further location-specific assessment of the benefits and constraints. Evaluate what nutrient-rich wastes are available within reasonable closeness to the site.

Complete further research on:

  • the influence of nutrient-rich wastes on soil mycorrhizae (root fungi)
  • the role of nutrient-rich wastes on restoring whole ecosystems
  • how much increased plant growth increases carbon storage.

One Billion Trees Programme research

This research was commissioned by the One Billion Trees programme.

Read about other One Billion Trees science projects on the Ministry for Primary Industries’ website.