Farm Ireland

Wednesday 21 February 2018

Plan fertiliser levels to hit the ground running

Michael Gottstein

Fertiliser is an important tool to help you manage your grass and to encourage extra growth during critical periods of the year when demand from grazing livestock is highest.

One of the biggest challenges for sheep farmers is to have sufficient grass at turnout for freshly lambed ewes. This is where applying nitrogen in the form of either slurry or chemical fertiliser comes in to play. Except in cases where a farming enterprise is run at a very low stocking rate it will be essential to have some amount of fertiliser spread before turnout.

The extremely cold weather has damaged much of the grass that was accumulating over the autumn/winter period and grass growth during the cold spell will have been nil. While ground conditions a few weeks ago were suitable for getting out slurry where tanks were full, they were not ideal for spreading chemical fertiliser (ie too cold or too early). Hopefully, as you read this article, the rain will have stopped and the ground will start drying out. The recent milder weather will also make conditions more conducive towards achieving a response from chemical fertiliser.

Given the volatility in chemical fertiliser prices over the past few years many farmers have adopted a wait and see approach towards buying their year's fertiliser requirement early in the year. The problem with this is that once conditions become suitable for spreading fertiliser there is a big rush to get fertiliser delivered to farms. Plan ahead somewhat and have sufficient fertiliser in stock so that you can avail of the spreading opportunities as they arise.

On farms where slurry is available this is an ideal substitute for chemical fertiliser nitrogen. By applying 2,000ga of watery cattle slurry you can expect the equivalent of around 20 units of nitrogen per acre to be available to the sward. The best response in terms of being able to capture the nitrogen fraction of the slurry will be got where it is applied in the springtime. The disadvantage of spreading the slurry is that you should allow a grazing interval of at least four weeks between spreading and grazing.

On farms where slurry is not available chemical fertiliser should be used. At this time of year, urea (46pc N) is the product of choice as it is much cheaper per kg of nitrogen than CAN or the other compounds that are based on CAN. As a general recommendation your first application should be about 20-25 units of nitrogen per acre. This is the equivalent of about a bag (50kg) of urea or almost a bag (50kg) of CAN per acre.

Once you have spread the initial fertiliser application you should plan for the second round. Ideally, this should take place four weeks after the initial application but not later than six weeks. The aim of this second application is to keep the grass growing until growth really takes off in late April or early May. The quantity of fertiliser that should be applied in the second dressing will depend on your stocking rate. On highly stocked farms, a second application of around 25 units will be appropriate. Again, this application can be made in the form of slurry where it is available.

Blanket spreading of the entire farm is a good idea from a labour point of view. For the initial application I would hold off applying fertiliser on very heavy covers (1,400kg +) until after they have been grazed out. Also, paddocks that are very bare (ie less than 4cm cover) will not respond well to urea and should be targeted with CAN or compound fertilisers when temperatures increase further.

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Remember that where lime has been applied in the last three months, you are unlikely to get a good response from urea or the nitrogen fraction in slurry. The reason for this is that the lime and the urea interact and the nitrogen fraction is lost. Therefore, if this is the situation on some of the fields on your farm you should use CAN or compound fertilisers instead.

The amount of phosphorous that is available in the soil can also have a dramatic effect on spring grass growth. Where soil samples show deficiencies of P you should take steps to correct these by applying P (and K) as required in the autumn. If this didn't happen last autumn then small quantities of these elements at regular intervals should help to improve grass growth rates. If you are unsure as to the fertility status of your soil then get a soil analysis carried out before you spread any fertiliser, slurry or farmyard manure (FYM).

Spring grass has a higher energy and protein content than concentrate feed. In addition it is cheaper than concentrate feed even where fertiliser is used to grow it. On top of all the economic advantages there are also advantages in terms of less labour to feed, bed and water the animals as well as health benefits (e.g. less footrot etc.). Get organised now so that you can take advantage of favourable weather conditions when they arrive.

Irish Independent