LandWISE has three pilot projects being run with Te Ahikawariki, the Vegetable Industry Centre of Excellence based in Pukekohe. The projects include cover cropping, soil stability testing and use of a device to read nitrate test strips more accurately.
Te Ahikawariki/VICE is a government-funded project that is setting up a cutting-edge vegetable research farm in Pukekohe. The project is a collaboration between mana whenua and vegetable growers that aims to create a central location for research to support the entire vegetable industry and protect the land.
Cover crop options for vegetable growers – preliminary scoping study
Over the last few years, we have been posting reports of trials and tribulations with our cover cropping activities at the MicroFarm. Growing a cover crop is easy. Growing a cover crop that ticks boxes for maximum species diversity, non-herbicide termination, and allows the land to be ready for a crop on a certain date specified by processing companies is quite another thing. Our discussions with growers in Tairawhiti and Canterbury confirm we are not alone!
The Te Ahikawariki project involves us and regional contacts interviewing leading growers and industry people with experience in or desire to introduce cover cropping in vegetable production systems. By including five regions, Hastings, Pukekohe, Levin, Gisborne, and Canterbury, we are seeking to compile findings to give a national overview that identifies regional and sector specifics.
A summary from interviews, a resource inventory and literature review will identify where suitable information is available and where key gaps lie. This will provide a base on which to develop a longer-term research strategy and work programme for VICE.
Farmer Friendly Nitrate Testing
Since 2018, we have been using and promoting the Nitrate Quick Test from the University of California Davis (Hartz, 2010). The method was tested for NZ conditions under a previous SFF project through FAR and Plant & Food Research. The Nitrate Quick Test has much potential to help growers identify required nitrogen base and side-dressing rates and to justify applications.
Our Te Ahikawariki project is comparing results from Nitrate Quick Test strips using the current visual concentration assessment and estimate of soil moisture bands with the Nitrachek concentration and moisture determined by microwave drying soil and with commercial laboratory mineral nitrogen tests. A key part of the project is engaging with growers to demonstrate and support valid paddock sampling and correct use of the test methods, thus ensuring the knowledge is held within each regional community.
In parts of Europe, farmers must have approved soil nitrate testing completed before nitrogen fertiliser applications may be made. One accepted European methodology uses the Nitrachek™ device to read the test strips, removing the human eye variable and providing much more accurate readings. It also includes drying test-soil so there is no need to estimate soil moisture.
SLAKES: a cost-effective measure of soil structural stability
Soils with stable aggregates are usually found to be more productive than soils with poor aggregate stability. They typically have more organic matter present in the soil, which acts as a glue holding aggregates together, retain more moisture and have higher infiltration rates, and plant roots can penetrate deeper into the soil which means crops will be more drought tolerant and have better productivity. During rain events, soils containing unstable aggregates will disperse filling pore spaces and making the soil susceptible to erosion and compaction. Eroded soil will remove nutrients with it reducing soil fertility, compaction can cause aeration reduction, water logging and root disease which will affect crop health.
Many different methods have been used to measure aggregate stability, including Cornell University’s wet aggregate stability, Yoder’s wet sieving and Landcare Research – Manaaki Whenua’s (LRMW) wet sieving. However, these methods are time consuming and costly. The Soil Health Institute recommends testing aggregate stability with a smartphone app called SLAKES which was developed by the University of Sydney (Soil Health Institute, 2024).
Our SLAKES project is comparing results from SLAKES with the LRMW wet-sieve aggregate stability test and looking for correlations with VSA scores, bulk density, and total soil carbon levels. In March and April, we are trialling SLAKES with selected growers in Pukekohe, Gisborne, Hastings, Palmerston North and Levin. This will give us a range of soil and crop types to see how the methods compare in our young New Zealand soils.
We will report on our progress at LandWISE 2025! See you there.