Environmental considerations will be at the forefront of soon-to-be implemented regulations. And as with all major change, it’s likely the pendulum will swing too far in favour of the environment before coming back to reality.

This is particularly so when dairy and beef herds are seen as having an environmentally negative impact; and Overseer regards all nitrogen as equivalent, whether applied, fixed naturally by clover, or direct from the atmosphere.

Animals should not be regarded as having a negative impact. They should be seen as the catalyst that ensures carbon from the atmosphere is stored in the soil as humus. If that seems an outrageous claim, please view Alan Savory’s Ted Talk on desertification.

Without grazing, much of New Zealand would rapidly revert to low-fertility grasses and weeds before reverting to scrub and bush.

Removing sufficient atmospheric carbon dioxide to minimise climate change is only achievable by sequestering carbon in soil under grazed permanent pastures.

It is rapidly growing plants that have the greatest demand for carbon dioxide. It powers their growth and, because for at least nine months of the year rotationally-grazed pasture is actively growing, carbon dioxide is being removed.

The grazing process encourages regrowth and the treading action helps mix dung and dead grasses, stimulating the biological activity necessary to incorporate it into the soil and store as humus.  Humus is what remains of organic matter after it has been fully digested by soil life, and it stays in the soil indefinitely. This requires nitrogen and the best is that fixed naturally by clover.

Pastoral soils contain between 5000 kg/ha and 15,000kg/ha of nitrogen in the top 25cm, and it’s not the shortage of N, but the availability of it for plant uptake that limits pasture growth.

Plant uptake is only a small fraction of the total soil-held N, and most is recycled. Clovers in a well-managed sward can comfortably fix all the N required.

The urea content of animal urine is extremely variable, with research from the 1970s showing a range of 0.75 per cent to 2.5 per cent. The notion that all the urea in urine stays concentrated in the area in which it is deposited is also false, with data from here and overseas showing the soil/plant benefit from urine is likely to be two-five times larger than the actual area covered.

The only reliable leaching figures are from the concentrations of Nitrate-N in water taken from below grazed pastures. Trial work by Functional Fertiliser on a farm using only clover to create N showed a 70 per cent reduction in Nitrate-N compared to a neighbouring property applying urea regularly throughout the season.

For a real improvement in soil quality and pasture growth a rapid reduction in the current 750,000 tonnes of urea applied annually is required. Applied N ‘burns’ organic matter releasing N for plant uptake. Too much N and soil carbon levels decrease.

What does carbon do?

Carbon in the form of humus works as a filter. Soils with steadily increasing humus have excellent physical structures, encouraging plant roots to fossick at greater depth, extracting nitrate and phosphorus before they reach groundwater. 

Clover and milk urea

Extra clover in the sward doesn’t necessarily result in higher milk urea levels. The concentration of N in plants is at the highest during the rapid growth phase. With the onset of maturity most of the nitrates turn into full protein.

Therefore, pastures not grazed until maturity contain less nitrate-N. Thus less urea is deposited in urine by grazers, resulting in lower nitrate-N losses. Pastures with higher levels of protein also contain more energy, and milk solid production and animal weight gains increase.

Calculating protein by multiplying plant nitrogen levels by 6.25 will lead to regulations that will do little to improve water quality.

Stock reductions are not the answer

Animal numbers on Irish dairy farms have been restricted to two per hectare for a number of years.  Urea usage has not changed during that time and consequently water quality has not improved.

Focusing on animal numbers shows a misunderstanding of the causes of high levels of nutrients lost to groundwater.

Soil fertility inputs should be the focus, with fertiliser-N limited to 30kg/ha annually. By grazing animals appropriately, the optimum stocking rate will become apparent.

Rapid improvement happens

Farmers with excess animals grazing immature pasture and applying N in an attempt to fill a feed deficit are wary of change.

Under a Functional Fertiliser Farming Systems’ programme the feared transition phase does not occur. Pasture production increases almost immediately and with improved grazing management a year-on-year steady lift in production occurs. For more information, contact Peter on 0800 843 809.