Dairying – Management Notes, May
May 6, 2021
Introducing a multi-cut silage system
As we approach the silage season, paying attention to cut and wilt times will help boost quality and reduce dependence on concentrates through the winter. Adopting a multi-cut silage system could help maximise quality and performance from the same acreage. Although cutting earlier will reduce yield per cut, quality in terms of protein, digestibility and metabolisable energy (ME) will increase. Cutting early and wilting rapidly to achieve a dry matter (DM) of 28-32% will significantly help milk from forage. For example, grass cut in early May instead of mid May will be cut at a higher quality with a high D-value.
Rapid wilting is essential as sugar levels start to decline as soon as the grass is cut. Wilting increases DM and reduces clamp losses from effluent. After cutting, there is a two hour window when the stomata of the plant remain open; water loss is at its greatest at about 100 litres per tonne of grass every hour. After that, water is lost where the leaves are broken or the crop has been conditioned. As first cut is taken earlier in a multi-cut system, when weather conditions may not be ideal, tedding allows for air movement over the crop, helping evaporation.
Ideally, in a multi-cut system the time between cuts is reduced to four or five weeks. Individual cuts will be lighter compared to the traditional system. Therefore, it is worthwhile discussing the effect of the lighter cut on price with your contractor. A 1.0 MJ per kg DM increase in ME is generally achievable when moving from a traditional to multi-cut strategy. DM intakes can increase by over 1.0 kg DM per cow per day when feeding this forage. This enables an increased target for milk produced from forage. Increased milk production from home grown sources will reduce concentrate requirement and therefore more than pay for the extra contracting costs of cutting more frequently.
With reduced cutting intervals, pay special attention to crop nutrition to ensure all the nitrogen is absorbed before harvesting. Apply slurry immediately after harvesting. Fertiliser should also be applied as soon as possible and not more than 2.5 kg of nitogen per hectare (two units per acre) for each growing day between cuts. As crops are lighter consider how long they are wilted. To achieve 28-32% in ideal weather conditions, 24 hours wilting should be sufficient. As the grass is leafier, fibre levels will be lower. Increasing the chop length to 5 cm will help with ensiling and fermentation. To maintain rumen health, the diet may need to be supplemented with extra fibre such as straw or haylage.
Clamp management
Clamp management is key to minimising loss of nutrients. If dry matters are desirable, the silo needs to be filled quickly and grass distributed evenly. The aim is to remove the air and make the clamp as airtight as possible. Spread the grass in shallow layers and roll continuously. Ideally, the silo should be covered immediately and the cover weighted effectively, paying particular attention to the shoulders of the pit.
Slurry and fertiliser application
The phosphate (P) and potash (K) recommendations for second cut silage vary according to soil reserves. If you have
a recent soil analysis for your silage fields, use the online CAFRE Crop Nutrient Recommendation Calculator to work
out slurry and fertiliser requirements for second cut silage.
As a guide, at soil index 2 for P and index 1 for K, typical of fields normally cut for silage, slurry has the potential to provide some of the nitrogen (N) and K and all the P needed. Practically, a 22,000 litre application of dairy cow slurry per hectare (2,000 gallons per acre), ideally using a low emission spreading technique, contains 17 kg of N, 26 kg of P and 63 kg of K. Top up with 375 kg per hectare of a 22:0:10 type fertiliser (three hundred weight bags per acre) to meet second cut needs. The majority of second cut silage swards will give a positive response to applying fertiliser containing sulphur.