Dairy notes March 2007
The Value of Early Grass
Running short of silage - is early turn-out an option? Grass covers are building up rapidly on fields closed since last October/November. With levels of 2700 -2800 KG dry-matter/ha on the best fields, the potential for early turnout exists on many farms.
Research at AFBI Hillsborough has shown that two hours grazing can reduce silage requirements by 25 percent, increase yield by up to 2.5 litres and raise milk protein by over 0.1 percent. This will improve returns by £50day in a 70cow herd – an important boost to income at current milk prices.
A slow transition to full time grazing over four to seven week period will allow cows to gradually adapt to a grass based diet, reducing the potential risk of the health and fertility problems normally associated with rapid turn-out.
Turn the cows out for two to three hours/ day as soon as possible. It is essential to make the first rotation of the grazing area last until the 3rd/4th week of April when grass growth rates are fast enough to meet the herds demand from full-time grazing. Restricting grazing time will ensure the first rotation is not completed too early.
Grazing Guidelines
Early grazing is possible, even on heavy land, provided access is good and the herd is encouraged to graze aggressively for the short period they are out:
- Ensure cows go out with an edge to their appetite. Ideally they should be finished their silage an hour or more before morning milking. Feed the majority of meal in the evening if possible. If necessary hold the cows in the cubicle house for one to two hours after morning milking, especially if it is raining.
- Graze as square an area as possible Cows graze out square areas better. They tend to walk around more and leave grass behind in long, narrow paddocks.
- Use a back-fence to ensure cows are only on an area for one grazing. Sward damage, if it occurs, will then be restricted to a small area. Also it is important to protect re-growth.
- Leave the cows out for only two to three hours. Keep an eye on the herd and bring them in when they have finished grazing as this is when most tramping occurs.
- Be flexible – if conditions are bad keep the cows in.
Fertiliser for silage
What fertiliser do you need to apply for first cut? Under the recently introduced phosphate regulations, chemical fertilizers containing phosphate (for example, 27.6.6 or 25.5.5) should not be applied to land unless there is a proven requirement – soil analysis is required. On fields with high phosphate (P) and potash (K) indices of 2 or higher an application of over 17000 litres/ hectare (1500 gallons/acre) of cattle slurry will meet the P & K requirements for a silage crop. A straight nitrogen fertilizer can be used.
If the P index is 1or lower, slurry will not provide all the P required and a compound fertilizer (27.6.6 or 25.5.5) could be used. Where P index is 2 or above but K index is low (0 or 1) a zero P compound such as 27.0.6 should be used along with slurry.
Allowance should be made for the significant contribution to nitrogen supply from February/March applied slurry. A 34,000 litres / hectare of cattle slurry will provide 25-30 KG of nitrogen/ha – a saving of about 2 bags of high nitrogen fertiliser/ha. (3000 gallons/acre will provide 20-25 units N/acre – a saving of ¾ bag/ acre).
With the possible exception of reseeds there is no yield benefit in applying more than 120KGs/ha (96 units/acre) of nitrogen for silage production.
If a silage field is to be grazed before closing for silage, make allowance for carry over of 50 percent of the nitrogen from urea applied in from February onwards.