0800 843 809 info@esi.org.nz

P.W.Burton

One well-known farm consultant derides any alternative to the superphosphate, muriate of potash, and urea driven soil fertility system as “flying in the face of sixty years of science”, with performance data being rejected as anecdotal.

The value of soil tests showing results in Base Saturation figures rather than just MAF Quick Test and Olsen P figures are dismissed by another scientist as “failed science”.

MAF Quick Test and Base Saturation figures are calculated from the actual amount of the element extracted.  MAF QT figures are reported as a number while the Base Sat figures relate the amount extracted to the storage capacity of the soil, reported as a percentage.

Both measures are valid and are contained in the earliest comprehensive work undertaken by government scientists in the 1940’s.  One can be converted to the other, and back again, with a simple formula, in much the same way as fuel usage can be expressed as miles per gallon or litres per 100km.

When the long-term results from the use of any alternative soil fertility system can no longer be denied by any measure, the products used are referred to by some as “snake oil”, with the obvious inference for those selling them.

In one instance when Functional Fertiliser’s total nutrient packages were referred to as such, it was quickly followed by, “but it works”.

The manufacture and widespread use of superphosphate does go back 60 years and beyond.  The use of muriate of potash (potassium chloride) followed soon after.  However the widespread application of urea was embraced only after the ammonia urea plant in Taranaki came on-stream in the late 1980’s.

It is assumed by most farmers and consultants that there are volumes of trial work backing their use.  This is not the case. Although there is much short-term work around the use of these products, there is little that can be regarded as long term trial data.

All the research information available, therefore, requires careful interpretation.  The mainstream systems that have evolved over the last fifty years have been based on common practice, and that has changed little by little over time, corresponding more to manufacturing and storage capability rather than farmer requirement.

Initially, high-quality phosphate rock from Ocean and Nauru Islands was available at low cost, and because pastures responded to the application of both phosphorus and sulphur, single superphosphate plants were commissioned.  This allowed a cheap effective product to be applied with positive results.

Cost at that time was important, as farming was very much in the early development stage, with every expense carefully scrutinised, resulting in ‘lowest-cost’ becoming part of the culture.

Once the supply of rock from the Pacific Ocean was exhausted in the 1980s, phosphate rock was purchased from more distant places.  In a competitive marketplace the reason for anything being cheap is because it’s not wanted by others and, in the case of phosphorus, the cheapest rock contains the highest level of impurities, usually cadmium.

There are now large areas of our most productive land with levels of cadmium that limit what can be grown on it.  

Because of the steadily increasing Nitrate-N levels in groundwater, there is a strong movement now underway to replace the very large tonnages of urea spread, by nitrogen fixed naturally, primarily by clover.

The other reason for this shift is that pasture production under conventional N-driven programmes is steadily declining to the point where an increasing number of farms are becoming uneconomic.

That decline has taken place gradually since the introduction of urea, before which top quality pastures were growing more than 18 tonne of dry matter annually.  Some figures being quoted now are as low as 10-13 tonnes.  In a good season 14 – 15 tonne is now the maximum for properties using urea for nitrogen, while the production from Functional Fertiliser’s ‘alternative’ programme is now as high as 20 tonne/ha annually, with steady incremental increases over the last thirteen years. For more information call Peter on 0800 843 809.

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