0800 843 809 info@esi.org.nz

During the 1990’s when dairy payouts were escalating and there was an abundance of flat land, primarily in Canterbury, suitable for conversion the key to ramping up pasture production was the application of urea.

The sign to the wider community that the operation was serious and sizable was the erection of a urea silo.

Although not necessarily intended as a status symbol, the silo along with new utes and 120hp tractors sent an undeniable signal to the wider community that serious farming had now arrived.

Synthetic nitrogen is an exceptionally effective development tool when used in conjunction with new grass species particularly true annual grasses and winter growing hybrids.

Because of the immediate increase in growth, it is assumed that a continuation of regular nitrogen inputs will provide an ongoing lift in total growth.

That doesn’t occur and a ceiling is soon reached, and when heavier rates are applied to achieve the same boost there’s a steady downward spiral.

This will not be immediately obvious and any reduction in annual growth can be attributed to unfavourable climatic conditions that occurred during the season, with climate change a convenient scapegoat.

Synthetic nitrogen works by creating a rapid rise in bacterial activity in the soil.  As they multiply a food source is required to maintain their activity and carbon is consumed releasing nitrogen for plant growth.

Should more carbon be consumed than sequestered from primarily dung and old root, a reduction in moisture and nutrient holding capacity occurs and a degree of resilience is lost.

When all climatic conditions are favourable growth can still reach expectations however the drop off with a change in soil temperatures or moisture becomes increasingly rapid.

It may take several decades for a significant loss in total soil carbon however it is the labile, or mobile, fraction that is most rapidly depleted and that fraction is largely responsible for the speed at which nutrient is cycled.

To compensate, larger and more frequent amounts of water-soluble nutrient is often applied with potentially a short-term gain, but the long downward grind continues.

Nitrogen is an essential growth element and if not applied in the synthetic form it must come from another source and in permanent grazed pastures that is from clovers.

The 1984 edition of Fertiliser and Soils in New Zealand Farming by Peter During containing a significant amount of nitrogen fertiliser research, shows that pastoral soils here may contain between 5,000 – 14,000kg N/ha in the top 15cm.

Of that approx. 450kg is taken up by herbage and after accounting for that returned via uneaten herbage, dung and urine, 240kgN/ha is required to be fixed by clover to balance the uptake.

Clover in a well-managed sward can fix far more than that, provided astute grazing management as taught in the 1970’s and 80’s is employed, and those skills are readily obtained.

There are farmers today growing and producing well in excess of district average with no reliance on synthetic nitrogen that may provide the blueprint for those wishing to reduce costs significantly and develop their operations independent of mainstream doctrine.

Over twenty years ago Functional Fertiliser developed the two products CalciZest and DoloZest containing soft carbons inoculated with a wide range of selected beneficial fungi and bacteria that improve physical soil structures and rapidly increase the rate of nutrient cycling.

When used as the base of total nutrient programmes, the reliance on synthetic nitrogen can be rapidly phased out with more total pasture grown at a lower cost.  Over time urea silos on properties may well come to signify inefficiency rather than rapid development.

For more information contact Peter on 0800 843 809.

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