Comment: Dr Doug Edmeades takes a look at the problems with the Government's nitrogen fertiliser caps.
The Government's recent decision to cap N fertiliser inputs at 190 kg N/ha/yr is doomed to failure because it ignores the basic science.
When an animal urinates, it applies N at the rate ofabout 500 to 1000 kg N/ha.
This is too much for the pasture and soil to accommodate and hence results in a huge excess of soluble N in a localised spot of soil, which is then subject to leaching into waterways.
It is for these reasons that the animal urine patch is the source of most (about 95 per cent) of the nitrogen getting into waterways. Thus, the key to controlling the amount of N leached is to control the number and frequency of urine patches, especially in the autumn/early winter period.
There are three sources of N in the animals' diet and hence in the urine:
The largest is the clover N. Clover is a legume and it converts atmospheric N into plant protein. This "fixed N" feeds the soil with N, which is taken up by companion grasses.
The other two sources of N come across the farm boundary on to the farm, as either fertiliser N or the N in supplementary feeds.
Racing now to the point - if fertiliser N is capped there are two likely outcomes.
Farmers will simply import more supplementary feed to maintain production, and/or, the clover component in the pasture, and hence the amount of fixed N will increase compensating for the decline in fertiliser N.
Can you see the problem?
Either way the total amount of N in the soil/plant/animal system will remain unchanged.
Ipso facto the amount of urine N and hence N leaching will remain the same. Water quality will not be improved.
The proposed fertiliser N cap is technically flawed. This is what happens when policy development is undertaken by those who, in my opinion, have no understanding of the science of farming.
There are other more philosophical and political reasons to reject this piece of flaky policy.
Dr Doug Edmeades. Photo / Supplied
We had, or at least I thought we had, rejected the European approach to developing and implementing environmental policy, based on controlling inputs.
Our approach was, I thought, to be focused on managing outputs. The difference is very important in terms of the growth and development of society.
Consider the current dilemma. The goal is to change on-farm behaviour to improve water quality. Fair enough. The input controllers say cap fertiliser N. If that does not work (as predicted above) then we will control something else, like, cap stock numbers, or, get rid of all fertilisers, or reduce farming activity, or become vegan and get rid of animals – and so on, and so on - control, control, control.
The output control approach says: we (i.e. society) will set limits on the concentration of nitrogen in waterways. Indeed, this is exactly what has already been done, in many regions in New Zealand. With the limit set, the farmer can do whatever he likes on the farm providing the freshwater N goal is achieved.
This approach encourages inventiveness and entrepreneurship.
It allows the farmer to think of other options - put the animals in a herd home, especially during the rainy season, so that the urine can be collected and returned to the soil at an appropriate agronomic rate.
Or, tile drain the flats so that the N moving down through the soil is intercepted, captured and returned to the soil.
Listen to Jamie Mackay interview Dr Doug Edmeades on The Country below:
Input controls restrict the growth, development and the progressive evolution of society. Output controls encourage growth and innovation. The choice is often dressed up in the various political colours: green, red or blue. More precisely the choice is between progress or extreme environmentalism.
And to add insult to injury, I think this N cap policy is contemptible, at this Covid time.
To control the pandemic, we have accumulated significant debt. This debt will have to be confronted at some future point and the one industry that has the size and capacity to deal with this is the pastoral sector.
And so, at the very moment when you need your "A" team "pumped and motivated" you kick them in the guts - again!
Why? Why do you do that?
- Dr Doug Edmeades, MscHons, ONZM (Services to Agriculture), is an independent soil scientist based in Hamilton.
