Sharing comprehensive soil health data

15 April 2021

Fertiliser Association of New Zealand's Response to the Ministry for the Environment's report 'Our Land 2021'

Full Phosphate data tells different story

Good soil fertility is critical for our agricultural economy
"We welcome today's report from the Ministry for the Environment and Statistics NZ, which focuses on the importance of soil health and fertility to provide food and export production for New Zealand," says Dr Vera Power, Chief Executive of the Fertiliser Association of New Zealand.
"As the report states, land is central to our identity as people of Aotearoa New Zealand-it is our tūrangawaewae, our place to stand.
"One of the areas highlighted in the report is soil quality, and in particular, soil fertility as measured by the 'Olsen P' soil test. However, the report's analysis is based on a limited data set," said Dr Power.
New Zealand's fertiliser co-operatives encourage their shareholders to regularly test their soils to inform their nutrient use. Over the last year, the Fertiliser Association has compiled Olsen P results from this data.
"The analysis covers approximately 100,000 soil samples analysed each year over an eight-year period, making it probably the most substantive analysis of soil quality data ever undertaken in New Zealand," Dr Power states.
The analysis can be viewed on the Fertiliser Association's website at
"Our soils and their health are core to who we are, and how we grow our food, says Dr Power.
"The MFE report brings together some new information, it also highlights significant data and information gaps and the need for more targeted data.
Our data set shows that many drystock farms are operating at the low end of the target range for Olsen P levels, with most dairy farms operating within the target range for productive soils. Dairy farms on ash soils tend to be at the top end of the range reflecting their historical high phosphorus demand.
"Our analysis suggests a slightly different picture than presented in the MfE report," commented Dr Power.
Based on this new data, the national median Olsen P value for dairy farms across all soil types is below 35, well within the target range. This is based on more than 270,000 records over five years. This contrasts with a higher median figure for dairy farms of 67 mentioned in the MfE report.
Based on about 270,000 more data points than the MfE analysis, the national median for Olsen P for dairy farms is virtually half of that stated in the ministry's report. Inaccurately estimating soil fertility levels across the country presents real risks and potential costs for 'New Zealand Inc.' We look forward
to working with the Ministry and Statistics NZ on how we can share this information so that it can be represented in future reports.
"The larger data set, based on data from certified laboratories, is likely to give a more realistic view of soil fertility levels across New Zealand," said Dr Power.
It is important to note that phosphate fertiliser use in New Zealand has declined. A recent paper titled Why are median phosphorus concentrations improving in New Zealand streams and rivers? indicated that we are seeing an improvement in phosphate levels in rivers.
"This was attributed mostly to better management on-farm-an encouraging sign for us all," added Dr Power.