Harvesting good quality, cost-effective forage is about timing, writes James Duggleby, of Krone. That includes when to mow the crop, how long it should be left to wilt and how to present the crop ready for harvesting. The two factors which dictate timings are weather and output. If you want to ensure you are in control of productivity, it is important to own and use suitable forage harvesting equipment.
When it comes to harvesting, preparation is everything. Make sure equipment is well maintained and ready to go to avoid costly breakdowns at critical times. There are a number of different factors to consider when it comes to mowing, tedding, raking and harvesting, so it’s important to assess the farm needs, labour availability and handling capacity to maximise efficiencies and silage quality.
The growth stage of the crop will determine the type of silage produced. Young, leafy grass will be higher in energy and lower in bulk, as the crop matures, the digestibility (D value) will decrease as the yield increases – a trade-off between yield and D value is required to suit the livestock being fed.
Mowing timing should be dictated by the plant’s growth stage and not the calendar.
The best time to mow is in the afternoon as grass sugar levels will be peaking. Exposure to the midday sun will allow the grass to photosynthesise, resulting in higher energy levels and the ley should be free from rain or dew. The use of a conditioner is often debated. With the waxy cuticle being broken by the conditioner, wilting can be increased by up to 20%. The problem is if it rains the conditioned leaves will then reabsorb water more quickly. If you do use conditioner it is important to ensure it is set correctly – too harsh and it will pulp the grass and increase fuel usage – too light and it will be ineffective. The mower should be set to achieve a stubble height of about 5cm – cutting too low will impede grass regrowth and add little nutritional quality to the silage, as the base of the plant is low in D value.
Mower blades will also be blunted and the risk of contamination from soil and stones will increase. It is important to carry out regular in-field checks to make sure you are getting the best from your harvesting machinery. They do not take long and can have huge benefits. Mower blades should be regularly changed as blunt blades will not cut the grass cleanly, dramatically slowing regrowth. Setting your mower to spread or swath is down to conditions on the day, but this basic rule can help. If the ground is dry, set the mower to spread full width to maximise the surface area of the crop for rapid wilting. If the ground is wet, leave the grass in a swath, allowing the ground to dry out either side before tedding.
Tedding will help to achieve a rapid wilt and ensure the grass is evenly mixed, ensuring a uniform wilt and therefore more uniform quality, with fewer hot/wet spots in the clamp or bale. The tedder tines must be set to 2-4cm above the ground, and this should be set in the field. To check the correct working height, drive forward slowly and check if the tines are scraping the soil or leaving grass behind. Too low and you will contaminate the silage and increase machinery wear, too high and you will leave a mat of grass behind. It is also important to match the forward speed of the tractor with the RPM of the pto shaft – if you need to cover more ground go for a wider spread; do not drive faster as it will affect silage quality. The diameter of the tedder rotors and the number of tines will play an important role in the quality of the spread; different tedders have different sized rotors.
Generally speaking there are three rotor diameters, suited to different applications. Large diameters (seven tine arms) are typically suited for silage, where one pass is required tedding out the mower swaths. When sizing a silage tedder each swath should fit between each pair of rotors. The smaller the diameter (five tine arms), the finer the spread and the more consistent the wilt, ideal for tedding hay. However, many tedders are required to spread a variety of crops behind a range of mowers; a medium diameter rotor (six tine arms) will provide the best all-round solution.
Presentation of the swath to the subsequent harvesting machine has a big impact on efficiencies and quality – an even, box-shaped swath for a smooth, consistent flow is required. Row up just before harvest so the grass quality remains uniform – too long in the swath and the top will wilt more than the bottom, producing an inconsistent dry matter.
Correct working height of the rake is important, otherwise you will either pick up stones and soil, or leave grass on the ground which will rot and damage the subsequent cuts. Ideally a rake with electric height adjustment should be used as the rotor working height can be adjusted on-the-move to suit varying conditions. Again, as with tedding, match the tractor forward speed to the RPM of the pto shaft; higher dry matter crops will take less moving then wetter crops, so you risk throwing it too far or leaving some behind.
The type of silage required will influence which harvesting technique is used. Commonly a forage harvester or wagon is used for high-quality silage, with lower energy crops being baled for feeding to dry cows. When choosing equipment, ensure there is enough capacity to manage the crop in the clamp at the same time as harvesting, so that every stage of the silage-making process can be undertaken at the correct time. The same is true of using a contractor – ensure they can do what you want, when you want, to achieve the right quality silage. Savings on contractor fees can quickly be lost through reduced quality forage. Silage is made by pickling the grass, which is the result of good bacteria fermenting some of the grass sugars into lactic acid, which in turn prevents the growth of bad bacteria and preserves the nutrients.
The fermentation process is anaerobic, and will therefore only happen once all the air is excluded from the clamp or bale. Furthermore, soil introduced into the grass as a result of poor harvesting techniques can introduce harmful bacteria which will spoil the silage and pose as a potential health risk to the livestock. When collecting grass from the swath make sure the pick-up height is set correctly preventing the tines from collecting soil or stones. Whichever harvesting technique you have chosen, all knives should be kept sharp as this will produce a cleaner cut and reduce fuel consumption. Many people wrongly think that giving the knives an occasional ‘good’ sharpen is best practice, when actually sharpening a little and often will save time and fuel while helping to prolong the life of the knifes.