| Summary
Points |
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The purpose of fertiliser application to grassland is to produce an
appropriate level of soil fertility to support adequate crop growth (and
animal performance) and to maintain an adequate level of soil fertility by
replacing all nutrient off-takes, be they in the forms of milk, meat or
crops, (grass/silage). |
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No ecosystem, whether natural or managed, is completely "leak-free"
e.g. all soils whether fertilised or not give up finite quantities of
nutrients to percolating water. |
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In order to accurately target soil nutrient deficiencies, soil
analysis is critical. |
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Over 50% of all samples are deficient in Phosphorus (P) and
Potassium (K) and a further 25 to 30% of soils require annual maintenance
inputs of P and K i.e. to replace removals. |
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A deficiency of N restricts the growth of individual leaves (leaf
size) and their photosynthetic capacity as well as
restricting the number of tillers that develop. |
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Generally, herbage response to N application follows an initial
linear phase of 15-30 kg DM/kg N, usually up to an
application rate of within the range 250-400 kg N/ha. |
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Regardless of how much N is applied, the production of grass will be
significantly less than its potential if other
essential soil nutrients are deficient. |
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Restricting Nitrogen (organic and inorganic) levels on Irish
dairy farms would significantly reduce farm income. |
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Phosphorus is very important for crop establishment and
root development / growth and plays an important role in
the nutrition of livestock. |
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Investigations into environmental deterioration of
water
bodies should first exclude point sources (both in-farm
and off-farm) before considering diffuse sources. |
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The recent reduction in fertiliser K usage in Ireland is of
particular concern. |
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In Sulphur (S) deficient areas, grass yields are
substantially reduced especially in summer and early
autumn. |
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Trace element deficiencies are occurring with increasing
frequency in grassland. |
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The dry matter and level of nutrients in slurry can vary
enormously. |
