sheep2.jpg (87031 bytes) In winter, there is little or no grass growth. As warmer weather approaches in spring, the grass starts growing again. In order to grow commercial quantities of grass, fertiliser has to be added. This takes the form of manufactured fertiliser. Without it, the grass yield will be drastically reduced. Grass responds well to nitrogen fertiliser. This is applied in early spring and then regularly throughout the growing season. Natural fertilisers such as dung, are rarely sufficient alone.

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A considerable amount of research has taken place over decades to establish the optimum timing for fertiliser application. The timing and chemical make-up of the fertiliser is influenced by a number of factors. If the farmer spreads fertiliser too early in the year, it will not be taken up by the grass and rain will wash it away. Conversely, if fertiliser is applied late, the yield of grass will be significantly reduced. This will have a detrimental effect on the profitability of the farm for the rest of the year.

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The result of this research is a national indicator known as the T-200 sum. It is arrived at by adding up the average temperature for each day, starting from 1st January. Only positive figures over 00C are included. When the sum of daily temperatures reaches the 200 mark, the T-200 sum is said to have been reached. It is then warm enough for grass to utilise fertiliser. Progress towards the T200 sum is widely published in the farming press, for example, The Farmers Weekly.

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However, just because the T-200 sum has been reached, it does not automatically mean that the farmer will apply fertiliser, as his local conditions may vary. For example, the figure is a national average and the farm's locality may have experienced different weather conditions. The farm itself may be on wet soils, making it impossible for machinery to travel to spread the fertiliser early in the year, or may be situated in a cold north facing valley.