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Soil fertility

Agriculture

Soil fertility

Land is probably the most expensive resource on a dairy farm and one of the most important. However, soil analysis results in Northern Ireland over the last decade indicate that many soils are sub-optimal for at least one of the following; lime, phosphate (P), potash, (K), resulting in reduced production potential. Some soils are grossly oversupplied with P but there are also some soils with high potash indexes. High soil P indexes can have negative environmental consequences (resulting in high P levels in water bodies) and greater potential for grass tetany with cows grazing high K soils.

At CAFRE Greenmount Campus there is an ongoing programme of regular soil analysis, coupled with action as required to ensure that soils have the correct lime status and are in the optimal soil indexes for P and K. It is an ongoing cost to maintain adequate lime status. However, the cost of not doing so will far outweigh the cost of applying lime. The availability of many nutrients is markedly reduced when lime status is inadequate, so while on paper soil P and K indexes may be adequate, the availability of nutrients will inhibit crop production and grass yields. However, with grass production, particularly for silage, it is not easy to get a measure of the amount of grass produced per field and as a consequence, poorer performing fields may not be easily spotted.

At Greenmount Campus grazing paddocks are regularly measured for dry matter production, using the Agrinet grass budgeting programme and this allows a comparison of production between fields with underperforming fields considered for reseeding. For silage fields, the weight of fresh grass per field is obtained when grass is being harvested (trailers are weighed across the scales platform for each load) and grass samples are analysed for dry matter content. This helps to identify underperforming silage fields and aids the decision making process around reseeding priorities.

Soils recently submitted for analysis by farmers in Business Development Groups indicate that there is very little improvement in the proportion of soils that are optimal for nutrient status. Furthermore, fields used mostly for silage have lower potash status, indicating that nutrient management on many farms could be improved.

Click on the PDF’s in the Additional Information section on this page for more information on soil analysis from fields across Northern Ireland submitted by farmers in Business Development Groups and for CAFRE Greenmount Campus soil analysis.