Jon Morgan in an article in The Dominion late last year claimed that nitrate nitrogen was the “elephant in the room” with regard to water quality. It is and will remain so until it is recognised and accepted that excessive use of nitrogen fertiliser brings about a steady decrease in total pasture production.
Nitrogen fertiliser can be useful when used strategically in small quantities to manipulate early spring and late autumn pasture production. Its regular application throughout the growing season as a replacement for nitrogen supplied by clover can only be temporary.
Nitrogen fixed at no cost by clover is highly efficient as it is held in organic matter and released on an as required basis to maximise plant growth when climatic conditions dictate.
Fertiliser nitrogen is expensive and excess use results in a decline in soil carbon particularly in the top 30cm of the soil. It is soil carbon that stores both nutrient and moisture with each kilogram of soil carbon able to hold 4 kilograms of moisture.
Total Carbon measures from two farms near Edgecumbe, one implementing a ‘biological’ soil fertility programme based on CalciZest and DoloZest, the other a conventional fertiliser nitrogen driven programme show the property using a CalciZest/DoloZest based programme has 34,700 kg of extra carbon per hectare in the top 30cm of the soil.
With each kilogram of carbon able to hold 4 kilograms of soil water there is an extra 138,800 kg of moisture available for plant growth. This helps make sense of the observations that properties using high rates of nitrogen dry out more quickly and are slower to recover after rain.
A change from a conventional system where regular fertiliser nitrogen is applied to a far more efficient system growing up 20 – 30% more pasture using minimal fertiliser nitrogen can be introduced seamlessly over a three year period.
An application of Golden Bay dolomite at 250kg/ha (depending on soil test and production data), is normally sufficient to meet the annual magnesium requirements of intensive dairy production, start the process of improving physical soil structures, deepening the root zone and markedly improving animal health.
No longer can pastoral farmers and their representative organisations claim that as generators of much of the country’s wealth they are somehow not responsible for a decline in water quality.
Clean fresh water is a right enjoyed by all New Zealanders, and as the water we have is the only water there is, even free title to land does not give farmers the right to allow an increase in nitrate nitrogen, or any other minerals, to be carried in the water draining through their soils.