A leading NZ Soil Scientists Perspective

NZ Soil Scientists Perspective

Apart from not seeing a property, it’s difficult to be able to make an informed comment on soil tests for a number of reasons including:

  • A more accurate interpretation of a soil test is only possible after knowing something about a farm, its management and history, including the condition of the soil and pasture, to interpret the data correctly.
  • Knowing the amount of organic matter from test results of a pastoral farm, as soil organic C (carbon) levels can be the “holy grail” of a farm as it affects all aspects of a farm’s performance.
  • Soil tests are OK to a point, however herbage tests allow for an assessment of the efficiency of the uptake of nutrients in the soil by the pasture. This is key but is something that isn’t widely appreciated.
  • Many commentators might say you need a capital application of a phosphatic fertiliser for example, but just how much P is actually required will be indicated by the amount of P in the herbage and the biomass, and the activity of the P contributing soil microbes.
  • While Olsen P, Resin P and the Total P figures are helpful, many often treat the fertility expressed in soil tests as an exact science. In reality, this is far from the truth, because without the herbage and biological tests, you have little idea of the potential contribution of the all-important soil biological fraction.
  • Most plant available P and N occurs in the organic fraction of the soil, and soil tests cannot provide a clear indication of the actual nutrient status of the soil.


It’s notable how lifting the biomass performance of the soil microbes can lift soil fertility due to the close relationship between the two. The biological health of the soil is the “engine room” of a farm and money spent on getting this right with a biological fertiliser approach will have a better long-term return on investment than applying quick release fertilisers. Over time, fertiliser expenditure will come down because nutrient supply and turnover become much more efficient via a microbial pathway. Apart from the soil fertility benefits, a farm will also see benefits in improved animal health, reduced empty rates, reduced insects, pests and so on.

On a final point- an effective lift in the functionality of the micro life in the soil won’t occur overnight, so it’s important not to go “cold turkey” on the N (Nitrogen) front for example. A product like BioActive Soils BioBoost is an excellent way to assist with a transition away from high N fertilisers, as it has useful amounts of N in it, while carrying beneficial microbes to improve the soil biomass and long-term soil fertility. This product results in performance gains as well as environmental gains, and because they are ocean sourced products, they contain trace elements, providing another reason to be considered value for money fertilisers.

Key points summarised extract taken from a leading NZ Soil Scientist farm follow up communication

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