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.
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Using nutrient-rich wastes in plant nurseries, forestry and native plantingsWhat 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 in different ways:
- wastewater can be used for irrigation or fertigation in nurseries or planted areas.
- unprocessed or minimally processed sludges, slurries and solids can be used as planting mix supplements
- composted or processed slurries or solids can be used as planting mix.
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.
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. |
dairy factory,
meat processing,
food processing
Avoids water stress.
Decreases amount of clean water needed.
Re-uses wastewater.
Improves soil structure.
Improves soil biological activity.
Adds slow-release nutrients.
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. |
Helps soil hold more water.
Improves soil structure.
dairy factory
Decreases the amount of clean water needed.
Reduces discharge to aquatic systems.
application
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. |
woody mulches
Prevents erosion.
Saves water in dry/warm sites.
Suppresses weeds.
Stops browsing animals (deer, hares, rabbits).
Enhances nutrition when mixed with compost.
Helps soil hold more water.
Improves soil structure.
Improves organic matter.
Adds slow-release nutrients.
municipal
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.