Managing swards in unpredictable weather

Met Office data has shown Northern Ireland to have more than double its average rainfall for the month, with 185.4mm (207% of the long-term average). This is a far cry from 2022 weather when Northern Ireland saw temperature records exceed 31oC in the same month.

Keep Dry matter intakes consistent to avoid unsettled stock.

Judith McCord, Senior Technologist at College of Agriculture, Food and Rural Enterprise (CAFRE) highlights that this untimely wet weather has resulted in grass swards being ineffectively grazed, damaged or not harvested and as we already know this set back not only effects herd performance now, but it also impacts winter forage diets. 

Grasscheck data has shown that across Northern Ireland, average grass growth to the end of July 2023 was down 11.4% compared to the long-term average (7.06 T DM/ha compared to 7.97 T DM/ha).  Current metabolisable energy (ME) and crude protein (CP) are similar compared to previous years, however the dry matter % (DM) has consistently been lower than normal throughout most of July.  Wetter silages and lower grazed grass quality will reduce dry matter and energy intakes so diets will have to be adjusted to compensate for this.   There is variation in grazing and cutting scenarios across the province with some 2^nd cut silages cleared up in the last couple of weeks and some multi-cut systems having 3^rd cut in.  Although these have been mostly ‘snatch and grab’, the desire for high ME silage and efficient grazing may be subject to change for 2023 as we only can work with what we have.  Weather is set to be unsettled in August so what can be done to manage swards?

Grazing

Younger or lighter stock will do less damage to wetter ground so where possible keep heavier stock on drier soil conditions. Moving stock regularly, i.e., at least once daily and preferably more frequently will help to minimise poaching damage with the addition of more entrance/exit ways into paddocks where possible.  Sward assessment is more crucial than ever with dry matter intake (DMI) reduced in wetter conditions.  Where possible, keep DMI consistent with the ability to buffer feed silage at milking times and keep pre-grazing grass covers at no more than 3000 kgDM. Doing this will result in less grass being wasted through trampling.  On-off grazing should be considered as animals are capable of eating all their daily requirements for grass in two, three-hour sessions. Damage through poaching will be minimised if animals can be taken off the grazing area when not grazing. It is also helpful to graze the furthest paddock first and use a back fence to protect the recently grazed area.

Silage

Minimising compaction is a major challenge, so it is important to consider the harvesting process. Make sure mowers are correctly set for the ground conditions, plan your mowing route to avoid wet patches and leave areas that are too wet to cut- this can potentially be baled later.  If conditions remain difficult, consider mowing dry and grouping rather than tedding and raking.  At this stage you want to avoid damaging ground and soil contamination.  Where ground conditions are heavy, consider leaving and baling later when conditions improve. For the ‘snatch and grab’ cuts, remember that silage additive may help in the fermentation process and advice should be sought beforehand.

Unharvested swards

Where swards have been growing 8 or more weeks, but conditions remain difficult to harvest the advice is do not damage ground by trying to ‘snatch and grab’ a cut.  The nutritional quality of these swards has already been substantially compromised and the delay in cutting each week accounts for 10% increase of dry matter yield, digestibility drops by 3.5% and ME reduces by 0.6 MJ/kg DM. It has to be reasoned that wet and nutritionally poorer quality silage will not be suitable for milk cows alone and preparing for a drier 3^rd cut may help in the winter rationing.  Where possible split your cuts based on DM for easier accessibility come winter rationing.

Managing effluent

Effluent is an inevitable part of making silage however this year will see a larger volume due to heavier crops harvested in wetter conditions.  Grass harvested at 18% DM will produce approximately 150 litres of effluent per tonne. Grass harvested at 25% DM will produce around 25 litres of effluent per tonne. Before filing the silo firstly inspect the walls and floor to ensure they are free from cracks, are impermeable and no effluent can escape and if need be carry out any necessary repairs. Consider lining silo walls, particularly at joints to help seal the silo.  Check silo channels are clear of debris to prevent overflows and effluent flow is direct to a suitable storage tank – do this on a regular basis once the pit is full.  Given the current wet weather, wilting may not always be possible leaving an increased pollution risk from bales produced. Choose a suitable location to store silage bales - if stored on concrete there must be run off collection. If you are storing in a field then try to place them close to a track or lane to avoid compaction during winter months.

Repairing sward damage

Where heavy covers have been tramped and there is extensive damage, there may be a requirement for full sward reseed.  Plan to address any compaction issues by sub soiling or ploughing when soils dry out.  Where larger areas are to be repaired, a similar seed mixture to the original should be stitched in using a suitable machine. For DIY repair, the area should be chain harrowed and a similar seed mixture to the original should be broadcast and then rolled.  Advice on seed mixture and rate should be sought beforehand along with a nutrient management plan on fertiliser and slurry application.  It is reasonable to expect to have to reseed 10%-20% of the farm per year to achieve the farm’s full grass growth potential however with a year of potential damage this may prove to be more.

Slurry and fertiliser

If you are fortunate enough to have effectively cut silage ground, then applying slurry for the successive cut is next.  Recent weather has left conditions difficult but as with harvesting plan for the drier fields first along with a nutrient management plan and soil analysis to estimate how much needs to go on. Typically for every kilogram of nitrogen applied (from bag/slurry) you can see a 25kg DM response.  Nitrogen in slurry is prone to volatilization losses so should ideally be spread on a dull, drizzly day but not when heavy rain is falling or expected.  Using LESSE equipment is compulsory for all slurry spread by contractors, farms under derogation spreading after the 15 June, the spreading of anaerobic digestate and larger farmers ie. over 200 Livestock units and/or 20,000kg of nitrogen or more from pigs. 

This is a year to have a contingency plan in place. It is important to produce the highest quality silage and grazing that we can, however weather conditions have been practically impossible to work with in some regions.  ‘Snatch and grab’ where able but avoid soil contamination at all costs. It is easier to feed a lower quality silage than a contaminated one.

Notes to editors: 

1. Follow DAERA on Twitter and Facebook.
2. All media queries should be directed to the DAERA Press Office: pressoffice.group@daera-ni.gov.uk

Share this page