The first steps of the 2021 silage campaign have been completed on Owen and James Martin’s farm in Dromintee, Co Armagh. This involved carrying out a soil analysis across the farm and drawing up a nutrient management plan for the year ahead.

The Martins run 160 Holstein cows in a fully housed system, so the main focus in the fields is to produce three or four cuts of high-quality grass silage each season.

The repeated silage cutting was evident from the soil analysis results, as half the farm showed a deficiency in potassium (K).

On Dairylink farms in Northern Ireland, the Olsen soil test is used and the recommendation for intensive grassland soils is to have a K index of 2- and phosphorus (P) index of 2+.

The results from the Martin farm showed that 46% of the land area analysed at a K index of 1, 32% was 2-, 12% was 2+ and 10% of land had a K index of 3 or more.

A study of the distribution of nutrients across the farm by CAFRE adviser Anna Truesdale found that fields that were located further away from the farmyard tended to have lower K indices and soil pH.

Silage ground is at greater risk of having a K deficiency than land mainly used for grazing. The element is important for strengthening the grass plant against external stresses and ensuring optimal uptake of fertiliser nutrients.

Anna helped develop the fertiliser plan for the Martin farm by using the crop nutrient calculator, which is available through DAERA online services.

Fields with a K index of 1 are to receive around 22-33m3/ha (2,000-3,000 gallons/ac) slurry plus 390-430kg/ha (3-3.5 bags/ac) of 23:0:10 chemical fertiliser. A number of fields that were identified as being low in P as well as K may also receive additional inorganic P.

On fields where K index is 2- or greater, around 22-33m3/ha (2,000 - 3,000 gallons/ac) of slurry will be spread plus 330-370kg/ha (2.7-3 bags/ac) of 27:0:0 fertiliser.

It is also planned to provide additional dressings of K using muriate of potash (0:0:60) during the year to build up levels of soil K on the farm. Other discussions are taking place about applying lime to fields with a low pH (less than 6.0).

Owen and James plan to apply slurry as soon as ground and weather conditions allow and plans are being put in place to order fertiliser.

Assessing ration fibre content

An assessment of the physical fibre content of the total mixed ration (TMR) being fed to the lactating groups was carried out on the Martin farm.

Diets with reduced particle size have been shown to lead to less time spent chewing by dairy cows and an increased risk of acidosis.

But when particle size is too long, there is an increased risk of dietary sorting by cows and, ultimately, the diet consumed is very different to the one originally formulated.

A Penn State particle separator kit is composed of four trays with differing sieve sizes (0mm to 19mm). These are placed on top of each other in order of increasing sieve size. A TMR sample is placed in the top tray and the sample is shaken.

The resultant material caught in each tray is weighed to determine the proportion of different sized particles within the ration.

The findings for the Martin farm are outlined in Table 1. While the figures shown for the diet in the upper trays (larger sieve sizes) may not appear to match the original targets set, this is probably due to differences in chop length and dry matter content between local dairy cow diets and North American rations.

The results from the lower trays (smaller sieve sizes) more closely matched targets and the butterfat of milk produced recently has been strong for the herd at 4.29%, suggesting the physical structure of the diet is adequate.

Mixed ration for high-output cows

The latest monthly benchmarking figures for the Martin farm show that average annual milk yield is 9,691l from 3.6t of concentrates.

The milking herd is split in two feed groups. The high-yielding group is offered 42kg of silage, 6kg of a 24% crude protein blend and 4kg of caustic wheat. This is formulated for maintenance plus 28l and cows are fed to yield in the parlour with a 17% crude protein nut. The low yielders are on 42kg of silage, 3kg of blend and 2.5kg of caustic wheat. This ration is for maintenance plus 18l and all cows in this group are offered 1kg of parlour nuts on a flat rate basis.

Weekly round-up

  • Dairylink farmers are developing nutrient management plans based on soil analysis results.
  • Slurry is being targeted at fields with low P and K indices and compound fertilisers may be used on this ground too.
  • Lime will also be applied to soils that have a pH below 6.0.