By Peter Burton
I recently read a report on the experience of a large dairy operation where there was a 20% reduction in pasture production Year 1 when changing from a conventional N driven soil fertility programme to a certified organic programme.
In time a permanent reduction of 10% in growth is anticipated, and it’s probably the expectation of those contemplating reducing or eliminating fertiliser nitrogen, and yet there are alternatives.
Removing any input from a fertiliser programme and not replacing it energetically will result in less growth, guaranteed.
So, when fertiliser N is removed from a programme it must be replaced by nitrogen from another source if a reduction in growth is to be avoided.
Within the top 200mm of the soil under grazed pasture there is usually somewhere between 5,000 – 15,000 kg of nitrogen held in soil organic matter.
That’s many years of reserve and although it must be replaced, in the short term some of it may be utilised by improving physical soil structures and speeding the rate at which nutrient is naturally cycling.
Initially that can be achieved by lifting plant available calcium. Worm activity increases markedly after lime is applied and the analysis of worm cast shows they contain significantly more nitrogen than surrounding soil.
Soil rapidly becomes more friable encouraging plant roots to delve deeper accessing nutrient from below their normal feeding depth.
Increased calcium encourages clover growth and ultimately this is where the bulk of the nitrogen for plant growth will come from.
The speed at which this happens is surprisingly rapid. Lime applied in late spring early summer can have a marked effect on nitrogen availability, and clover growth, by autumn given reasonable summer moisture.
Clover rich pasture provides a wide range of benefits. Its markedly higher in calcium, protein, and energy, the key components of rapidly growing animals and high producing dairy cows.
It’s also more digestible which means animals eat more in their naturally allotted daily grazing time.
It can be left longer between grazings and therefore be more mature when grazed with no loss in palatability or digestibility.
And the incidence of bloat caused by clover when driven by calcium is far less than when driven by potassium.
Management is the other key component to lessening the impact of reducing fertiliser nitrogen dependence.
Winter applied nitrogen brings forward spring growth therefore slightly later lambing and calving date will bring peak demand closer to the time of most rapid growth.
Summer growth will be stronger than previously experienced because clover is strongest when soil temperatures are at or above 20℃.
Live weight gains and milk production improves with more clover in the sward, as does animal temperament.
Pastures to which N is regularly applied nearly always contains excess nitrate at the expense of full protein. Nitrates put extra pressure on both kidneys and liver and animals become irritable.
It takes only a week to ten days for unsettled stock when fed on mature clover-based swards to become settled and more easily managed.
Pasture energy levels also increase resulting in less total feed being required to meet animal requirements resulting in higher per animal and overall farm production.
There are fertiliser programmes that can be relied on to comfortably transition farms from fertiliser N dependence to increased reliance on N from natural sources without difficult to manage feed deficits.
Functional Fertiliser has products and programmes that have been in place on properties for over fifteen years and independent performance analysis shows higher pasture production, lower environmental impact and improved profitability is achievable.
For more information contact Peter on 0800 843 809.