Fertiliser costs a big factor in low soil fertility levels

Pic Roger Jones.
Pic Roger Jones.
Brian O'Kelly and 5 months old Brian Óg from Borris, Co.Carlow at the Graiguenamanagh parade, Co.Kilkenny. Photo: Mary Browne
Joe Kelleher

Joe Kelleher

The spring started, then it stopped and then started again. Let's hope we don't get too many more stops. Before the weather broke around February 20, many farmers had taken the opportunity to get some early fertiliser out.

These farmers got a good response to this fertiliser with growth rates of around 25kg DM/Ha per day being common for those who had nitrogen out. But a large cohort of farmers didn't get any fertiliser out during this window and now there is a bit of catching up to be done.

Many cows across the country have only seen grass for the first time this year in the past week or so.

This creates its own challenges with the key challenge now being to ensure that there is sufficient grass on the farm when we start the second rotation.

Paddocks grazed in early February will have close to 60 days to grow grass in time for the start of the second rotation, whereas those grazed for the first time in the past week will only have approximately 30 days to grow a sufficient cover of grass.

This will require the grass plant to grow at 30kgs/Ha/day plus from mid March to mid April to have sufficient cover (1,000kgs Dm/Ha) available for the start of the second rotation.

The likelihood of this happening depends hugely on the weather, but fertiliser is also a large factor.

Any farmer stocked at greater than 2Lu/Ha on the milking platform needs to aim to have 100 units of nitrogen out by May 1. For those stocked below this level, 70 units should suffice.

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Urea is generally the product of choice for springtime nitrogen for two reasons; 1. It is the cheapest source of nitrogen available; and 2. its ability to bind with soil is better than CAN based products in times of high rainfall. However, (at the time writing), the weather appears settled and perhaps we should be looking at getting some compound fertiliser out.

National statistics show that approximately 90pc of our soils are deficient in terms of soil fertility.

Many argue that this has occurred as a result of restrictions applied under REPS and other schemes, and this is probably true on some individual farms.

The reality is that it is no coincidence that as the price of compound fertilisers were increasing over the past 10 years, their usage was falling. This, I suspect, is the main reason why our national soil fertility has remained low.

One tonne of 18.6.12 can be bought today for €350 approximately. This figure was hovering around €400 for the past number of years. I am aware of some farmers who bought 18.6.12 three or four months ago for €300/t.

This represents great value for money, and perhaps while the price is relatively low we should be spreading up to our limits of phosphorus and potassium.

Derogation records are being submitted daily at present up to the end of March deadline, and I know from looking at the fertiliser records being submitted, that a large cohort of farmers only spread a small percentage of the total phosphorus and potassium allowed. Perhaps this is the year to reverse this trend?

Sulphur is another element that has to be remembered around this time of year, particularly on sandy or free draining soils.

Sulphur is essential for the formation of amino acids, the building blocks for proteins which are needed for growth and development in plants and animals.

It is also required to convert nitrogen to plant dry matter. As grass grows, both sulphur and nitrogen are used together so a sulphur deficiency will decrease nitrogen use efficiency and so reduce yield.

It is recommended to apply 16 units of sulphur annually to grazing swards.

Joe Kelleher is a Teagasc advisor based in Newcastle West, Co Limerick

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