Fill the Fodder Gap for Winter 18/19
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Factsheet: Whole Crop Cereal Silage (PDF)
- Establish the extent of the deficit in feed for next winter.
- When the rain comes, maximise grass growth for the Autumn by spreading fertiliser.
- Unproductive cows should be culled to reduce demand. Consider finishing heavy cattle before the winter.
- Forage crops including red start, rape and stubble turnips can play a role to fill the gap.
- If considering whole crop cereal silage, that decision needs to be made quickly. Only use high grain yielding crops.
- Avoid panic buying feeds and consider the factors below:
- Is a forage or concentrate needed? If the deficit is less than 20%, then the deficit can be filled by either forage or concentrate, otherwise most farmers will need to grow / purchase forage.
- What is the nutritional value of the feed?
- What is the cost of the feed relative to other feeds?
- Are there adequate storage, handling and feed out facilities for this feed?
- Have storage losses & variability in dry matter been accounted for?
- Is finance in place to buy feed?
David Wall and Mark Plunkett, Teagasc, Johnstown Castle
Drought is persisting into mid July so fertiliser applications will show no apparent benefit for grass growth until it rains and adequate soil moisture returns. Much of the fertiliser applied in the last 4-6 weeks still remains in the soil and will be re-activated once adequate rainfall occurs. Therefore, it is best to hold off on any further N fertiliser applications until temperatures decrease (i.e. dew at night) or prior to when rain is forecast on fields that were not fertilised in the last month. On fields that received an N fertiliser application after the last grazing rounds (i.e. where residual N is present in the soil) hold off on further N fertiliser applications until after it rains as the residual N in the soil will likely be sufficient to kick off grass growth.
In dryer soil conditions fertiliser containing Ammonium Nitrate & Calcium Ammonium Nitrate as their N source are more safe to spread, and have lower risk of volatilisation loss to the atmosphere, however, they are not likely to become active or taken up by plant roots until sufficient moisture is present.
Currently soil moisture deficits (SMD) range from >90mm in the southeast to 60 mm in the north west (Met Eireann 9th July). Once SMD >50 mm growth will become restricted and >75mm drought conditions set in and perennial ryegrass will go dormant. Large quantities of rainfall will be required to fill these soil moisture deficits in the soil (25mm [1 inch] rain = 250,000 litres/ ha [~22,000 gallons water/ac]). Applying slurry in hot sunny weather on very dry soil conditions will result in high N loss through volatilisation. In addition slurry spread with splashplate will coat the remaining green leaf area on grass with slurry and cause this grass to burn under the current sunny and dry conditions.
Figure 1:-Soil Moisture Deficit 9th July on moderately drained soils
Table 1:- Soil Moisture Deficit categories and the corresponding soil and growth status (SMD Model, Lambkin, Ag Met, 2016)
Fertiliser for silage swards that have been grazed
In recent weeks many grassland farmers has been forced to grazed land that was closed for 2nd cut silage in early June. This land is likely to have received either slurry + N fertiliser, or compound fertiliser at closing for this silage crop. See fertiliser requirements for silage in table 2 below.
Scenario 1: Fields with light to moderate grass covers
In fields with lighter grass covers (1500-2500 kg /ha grass DM) a large proportion of this N- P - K applied at closing time will still remain in the soil. Where this ground will be closed again for silage in August /early September aim to apply up to 40-50% of the N required by the silage crop so that N remaining in the soil will be utilised before harvest in late September early October.
Scenario 2: Fields with moderate to heavy grass covers
Where the decision is made to graze fields with heavier grass covers >2500 kg/ha DM, then up to 75% of the silage fertiliser requirement should be re-applied on closing the field for silage.
To alleviate fodder shortages on farm prioritise application of fertiliser to fields that received no fertiliser for the last month to ensure that adequate nutrients are available once rainfall is forecast and growth commences. Stressed plants will respond better to the application of compound fertilisers and with a high P & K concentration + Sulphur as the grass roots requires less energy to find these nutrients. Remember the last date to apply N and P fertilisers is September 14th so fertiliser plans need to be adjusted now for the remainder of the season (~2 months).
Keep in contact with your advisor, milk processor and feed supplier. Talking to people you trust about your situation can really help