Making Silage on Wet Land

Currently, grass crops are very stemmy and it is at least two months since they were fertilised with nitrogen. In the normal course of events, such swards should now have a relatively high concentration of sugars and a low buffering capacity, making them fairly straightforward to preserve properly. Although buffering capacities are likely to be quite low at present, sugars concentrations may range from low to high depending on the crop. Sugar concentrations will be reduced by wetness on the crop - thus, once these crops dry out they are most likely to be relatively easy to preserve provided they can be ensiled properly. If nitrogen was put on late to boost yellow slow crops, it would use up nitrogen at the rate of 1-2 units per day, so after putting out a bag of Urea per acre, for instance, allow 23 days in good growing weather or up to 40 days where growth has been slow, for the nitrogen to have been used up in the crop. With good sunny weather and wilting, nitrogen is unlikely to be a problem, because sugars will be high. If in doubt, your Teagasc advisor can sample your grass precutting in a few minutes for sugars and nitrogen. Preserving grass properly as silage at present requires: 1. Quickly putting the harvested grass into an air-free environment (sealed silo or wrapped bale) and maintaining such conditions thereafter. 2. Ensiling the grass cleanly, free of soil contamination. 3. Promoting an adequate lactic acid fermentation. Thus, steps to consider with uncut silage swards are: 1. Defer commencing harvesting until sure that, once commenced, the job can be finished. Once harvesting commences, complete it as quickly as possible and seal the silos perfectly, making sure the grass is not being contaminated with soil. The worst scenario is to harvest under completely unsuitable conditions resulting in soil contamination of wet grass - the resultant silage is quite likely to preserve poorly and the field may be destroyed in the process. Almost as bad is to mow a crop and then be unable to harvest it or be unable to complete harvesting it. Therefore, it is important to be prepared to wait for drier conditions, despite the fact that crop digestibilities are already low and that target harvesting dates have been passed. 2. When ground conditions dry out, harvest the fields that can be safely travelled. Alter cutting height and angle to remove as much of the crop as feasible, but avoid contamination with soil. Similarly, operate the working height of the pick-up tines so as to prevent soil contamination. Try to move machinery across any part of the field as few times as possible. In some cases, modifying air pressure in tyres or changing the types of tyres may help spread machinery loads on ground and thereby improve trafficability. Similarly, it may be appropriate not to completely fill trailers with grass. Use more than one gateway if feasible. Consider using a more manoeuvrable machinery system such as baler/wrapper on wetter fields once they subsequently dry out sufficiently. Keep the concrete apron in front of silos clean and free from soil while silos are being filled - otherwise there is a risk that this soil will be brought onto the grass in the silo during filling/rolling. 3. Any degree of drying of swards will be beneficial - in particular this is true for the sodden butt beneath the crop. If this can be achieved, it will greatly enhance the likelihood of producing well preserved silage. Additionally, ground conditions can often dry quickly between rows of mown grass, facilitating greater ease of machinery operation without soil contamination. 4. If weather conditions improve and a crop can be wilted, preservation should be relatively straightforward. Thus, if feasible, this must be an objective. These crops will need to be excellently sealed to ensure they are stored under genuinely air-free conditions. Otherwise there is a risk of mould growth. They will also need to be well managed during feedout to avoid heating and ultimately mould growth. 5. If crops have to be harvested while they are still very wet, but can be harvested cleanly, it would be ideal to analyse a representative sample for sugar concentration. Where sugar concentrations are above 3% of the grass juice and all other silage-making requirements are fulfilled, then good preservation should be achieved without the use of an additive. If grass sugar concentrations are genuinely very low and harvesting cannot be deferred any longer, the even and adequate application of acid (2.5 to 3.5 litres/tonne wet grass) or sugar (10 to 20 litres molasses or 50+kg molassed beet pulp or citrus pulp per tonne wet grass) -based additives are the most reliable ways to aid preservation. Fresh yields of wet grass will be very high on many farms, and yields in excess of 40 tonnes per hectare will not be uncommon. Application rates of additives will need to take such potentially high yields into account. 6. Under conditions where grass is ensiled wet, considerable volumes of effluent may be released quite quickly from the silo. An effective drainage system based on tiles/pipes or straw bales will help remove effluent quickly from the silo and prevent a large build-up of effluent which can cause the silage to split and shift within the silo. The effluent needs to be collected and stored until it can be safely landspread - it cannot be allowed reach either surface or ground water. In many cases after harvesting, long semi-horizontal stubbles will remain due to the lodged nature of the preceding meadow. These are best removed by grazing soon after mowing, managing the animals to avoid poaching damage. Article by Padraig O"Kiely, Teagasc, Grange Research Centre and David Colbourne, Teagasc Ballyhaise.