Analysis of soil test results shows that sheep farms in NI have lower levels of soil fertility when compared with those producing beef or dairy.

At last Monday’s National Sheep Association (NSA) event in Ballymena, Alex Higgins from AFBI presented results from the soil-sampling programme funded through the EU’s Exceptional Adjustment Aid package in 2017.

Across 522 farms, 12,618 soil samples were submitted for analysis.

Across all NI farms, 200,000t of lime are required to be spread annually just to maintain current soil pH levels

Results showed that 43% of farms are below optimum levels for soil pH and, on average, would require 2t/ha of lime to raise pH for grassland to 6.0.

Breaking farms down into type, 52% of beef farms and 55% of sheep units required lime. Dairy farms fare better, with 34% requiring lime.

Across all NI farms, 200,000t of lime are required to be spread annually just to maintain current soil pH levels, said Higgins.

However, average actual application rates are estimated at 180,000t, meaning soil pH will continue to fall. He added that a total of 1.2mt of lime would be required to bring NI soils up to the optimum pH level.

P and K

In terms of soil nutrients, 23% of farms were below the optimum index II for phosphate (P), with 24% below index II for potash (K).

Sheep farms had lower fertility levels than beef units, with both worse than dairy farms. The west had lower P and K levels than the east, as higher volumes of rainfall increase nutrient losses.

Silage

Higgins also said that 20% of surveyed farms apply insufficient P and K for first and second-cut silage, thereby reducing yield potential (where P is applied it should only be done where a soil analysis shows there is a requirement).

Similarly, 50% of farms apply insufficient nitrogen levels for second, third or fourth-cut silage, partly because they over-estimate the N availability of slurry in summer applications.

Sulphur

Sulphur deficits are also an increasing problem on-farm. Sulphur should be routinely applied to all grassland in spring. The additional cost is £4/ha, but increased sward yields are worth up to £90/ha.

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