Applying sawdust to reduce nitrogen leaching

applying sawdust for nitrogen leaching
applying sawdust for nitrogen leaching

Applying sawdust to reduce nitrogen leaching

We’re always looking at new environmental practices to improve soil health, whether it’s for the growth of plants and trees or for the growth of grass for your livestock to graze. However, nitrogen from paddock soil can lead to an increased level of harmful pollutants in our waterways. This natural process of excretion can drain through your farming lands and pollute our fresh waterways.

Although it’s important for soils to have nitrogen for plant and grass growth, once nitrogen drains past root systems, it can become a pollutant. When the ground across paddocks becomes overly wet through rainfall or irrigation, the soil will reach a point where it can’t hold water anymore. This happens because the air pockets within the soil become filled with water and will drain downward. During that process, nitrogen particles are carried with them to fresh waterways. This is called nitrogen leaching.


Nitrogen Leaching Environmental Initiatives


The New Zealand government’s Freshwater Management policy requires councils to work with their regional farmlands to reduce nitrogen leaching. This is a great initiative, but it has also increased awareness of the potential environmental impacts of nitrogen leaching.


So what can we do to decrease leaching and reduce the risk of harsh chemicals in fresh waterways? We can look for natural solutions or alternative options to improve the health of your paddock soil and contribute to the overall health of our waterways. 


Ag Research is currently conducting a three-year study on ways to reduce nitrogen leaching called the Soil Armour Project funded by Sustainable Land Management and Climate Change program. In this particular study, they’re applying hay across pieces of farmland for feed, but also to act as a sponge to nitrates from urine, fertilisers, and other excretions to reduce nitrogen leaching. 


As we’ve followed this study, we’ve been inspired to discover other natural solutions and alternatives for farmers to decrease nitrogen leaching on their own farmlands. From our knowledge of technical media applications for over 30 years, we understand how media affects soil.


Sawdust is one of those medias. It’s a natural alternative that can work similarly to how hay is applied in the Soil Armour Project, but sawdust can offer other benefits to pastures and livestock.


Benefits in sawdust applications
  1. Increase organic matter to help grass grow
  2. Reduce mud for better animal welfare
  3. A natural acting sponge that can absorb nitrogen


Spreading sawdust will offer benefits to livestock and have positive effects on the environment. Our core values include being resourceful and making the most of what we have been given. So we’ll continue finding the best natural alternatives to decrease environmental pollutants. If you’re interested in learning more about applying sawdust or other media to your grazing lands, get in contact with us. We offer custom solutions to meet the specific requirements of your paddock soil including standard sawdust, blended sawdust, aged sawdust as well as customised solutions such as superfine sawdust for fast soil penetration. 

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Recommended depths

Typically you need a finishing layer of screened soil of 100mm when working with an uneven surface. 100mm of soil will allow to even out any hollows and give enough depth to create a flat surface

A general rule for compost is to allow for the depth of the current root structure of your plants with an additional 30-50% to mix in with the base. If you’re planting into holes or filling up a vege garden  you will need to accommodate for this prior to filling up

We recommend 100mm (10cm) deep for new bark gardens and planting into bare areas. For existing gardens with some cover, we recommend 75mm-100mm (7.5cm-10cm)

Note: Barked areas for playground impact protection need to meet NZS5828:2015 standards and is calculated on the fall areas and the height of the playground. Please contact us to discuss your barked playground areas

For paths and driveways which are often exposed to car and foot traffic, we recommend 100mm-125mm (10cm-12.5cm) on newly prepared areas due to settling of product.

This excludes preparation, compaction or drainage gravel underneath. For existing areas 75mm thickness is recommended for areas needing a small top-up.