Introduction
The field trial of composted soil conditioner containing 10% (w/w) zeolite (CompostZ) was designed and supervised by BioCarbon Soil at a property called Hyland, on the Warral Birthmere Road, Warral, near Tamworth, NSW. The zeolite was provided by Castle Mountain Zeolites and was co-composted with garden organics and paunch as detailed in the companion report “Trial of zeolite in commercial composting”. The purpose of the field trial was to measure the agronomic effect of using Compost Z and other compost treatments in the production of Canola, a common winter crop in the area. This report presents results for one year only (2023).

Results
All the treatments increased yield compared to the control. The control yield of 1,866 kg/ha is close to reported average dryland yields in NSW of 1,890 kg/ha. This was a high yield given that rainfall for July September 2023 was 60% of mean rainfall. Higher yield was achieved from Compost Z and Compost M treatments. Compost Z contain significantly higher (3-5 times) the levels of N available in the first year as ammonia and nitrate.

Conclusion
This field trial adds to the evidence that compost use can be an affordable farm management practice for
building soil health in dryland cropping systems over time. Application of Compost Z resulted in the greatest
increase in organic carbon and nitrogen, which are indicators of soil health, in year one. Affordability is
improved if compost blends can be supplied that contain higher levels of ammonia, nitrate, and other plant available (in year one) primary nutrients, particularly phosphorus, which are relatively costly to add using synthetic fertilisers due to the limitations on fertiliser use efficiency in soils with low soil organic matter. This can be achieved by blending compost with either zeolite and/or cow manure.
The significantly increased yield associated with the Compost M is only partially explained by the additional ammonia N supplied by the manure. Only 25% of the blended Compost M product was cow manure. Cow manure typically contains 2.5-3% nitrogen with <0.5% as ammonia N, part of which can be lost when surface applied. Total nitrogen in the compost is 1.5-2% with 0.1-0.2% ammonia and nitrate. Therefore, it appears that the additional benefit of this blend extends beyond what can be explained by additional ammonia N supply. Replication of the trial is required to confirm that these results are typical.

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For additional information contact Angus Johnston on 0466 411 241 or info@biocarbonsoil.com.au .