Dealing with the aftermath of prolonged wet weather on grass swards

The prolonged extremely wet weather since late summer 2017 has resulted in many grass swards being not harvested, damaged or ineffectively grazed since August or September last year. What can be done to manage such swards as ground conditions improve this spring?

Decaying sward of heavy grass.

Sward assessment is key starting point. The ratio of green leaf to dead material must be assessed. Where swards have a large proportion of decaying leaf, the options for this are limited – can the material be grazed? Is stock available that can utilise this material without causing animal health issues? Should the poorest quality material, if harvested, be recycled as farmyard manure in an environmentally acceptable manner?

Spreading slurry

• With tanks full, farmers need somewhere to spread slurry
• Where heavy unharvested dead covers are still on swards, splash plating 3,000 gallons per acre of slurry over them will not produce high quality grass for first cut silage
• Trailing shoe slurry spreading equipment will help to get slurry onto the soil surface under the grass canopy

Grazing heavy covers

• In some cases sheep have done more harm than good by tramping heavy covers into the ground.
• This may have been due to letting sheep wander through the fields unchecked, rather than allocating a daily area and controlling the grazing.
• Ideally, move stock daily or use two day paddocks at most to ensure a rapid and thorough sward clean-off.
• For heavy but grazeable covers, start by getting out young stock as soon as conditions permit and graze a relatively small area reasonably tightly to graze the sward quickly and effectively.
• Low yielding late lactation dairy cows could do the same job, but lighter young stock will do less further damage to swards and soil when ground conditions are marginal.

Unharvested silage swards

• There is a major difficulty where 2nd and 3rd cuts were unable to be harvested and these areas are to be used for first cut.
• The quality of these first cut swards will potentially be substantially compromised.
• Where a zero grazer is available, harvest this poor quality forage as soon as ground conditions permit to let the sward regrow before first cut.  After zero grazing the sward can be assessed for damage and repaired as appropriate.
• Care must be taken if feeding this zero grazed material due to its likely low dry matter content, poor nutritional value and the potential for soil contamination.
• Some farmers are considering letting swards with a reasonable proportion of leaf grow on for an early 1st cut, accepting that quality would be relatively poor.
• This poor first cut would not be suitable for milking cows but could be fed to youngstock and dry cows. More frequent later cuts would then be necessary to produce silage for milking cows.

Repairing Sward damage

• What prevented utilisation of the forage last year? Are there drainage, or access issues that need to be addressed?
• Soil structure – check for compaction – plan to address any compaction issues through ploughing and/or sub-soiling.
• Where heavy covers have been tramped into the ground there may be extensive winter kill, requiring a full sward reseed.
• Where larger areas are to be repaired, a similar seed mixture to the original should be stitched in using Einbock type machine.
• For DIY repair, the area should be chain harrowed and then again a similar seed mixture to the original should be broadcast and then rolled.
• Seed rates should be appropriate to the extent of the damage.
• Nutrient management planning based on soil analysis to determine lime, slurry, and fertiliser requirements should always be practised.

Slurry and fertiliser

Nitrogen in slurry is used more effectively in spring, as close to the period of grass growth as possible.  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.
It is important to choose the correct fertilizer based on soil reserves, slurry applications and crop need to ensure money isn’t wasted or that crop productivity is compromised. Crop Nutrient Calculators are available on the DAERA website.

The CAFRE booklet “Five steps to managing nutrients” will help you to interpret your soil analysis report, improve soil fertility and crop yield and also save money.

In summary

Patience is essential. Ensure that ground conditions are satisfactory whatever course of action is taken - there is no point in causing more compaction or soil damage at this stage when ground conditions will eventually improve.

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