Maximising a summer of grass growth

Northern farms are having an exceptional summer with grass growth consistently above demand and quality excellent, were good grassland management has prevailed. The focus now must turn to rotation length; extending the grazing round to 23/24 days, pre grazing covers must increase marginally to achieve this, by how much will depend on grass allocation and stocking rate.

For example, a herd allocated 17kgDM/cow, stocked at 3.5LU/ha and on a 21-day round will have a target pre-grazing cover of 1250kg/ha (17 x 3.5 x 21).

If the rotation was extended to 23 days: PGC = 1430kg/ha (17 x 3.5 x 24).

The target rotation length is altered now to achieve 25-day round by the end of July and 30-32 day round by August 31. On farms where a section of the grazing block is taken for second-cut silage then a third ‘cut and graze’ option can be implemented. This involves applying 2000gallons of slurry on the area were second cut has been taken off, topping this up with 40 units N/acre. This will accumulate a PGC of >2,000kg/ha of high quality feed by early-mid September (depending when second cut was taken off), grazing this will automatically extend the grazing rotation, meaning that on farms were this is possible, the rotation length can be maintained at 21-22 days now, rather than 23-24 days as suggested above. The area involved in this third cut/graze plan will dictate by how much we can extend the grazing round in September:

For example: 2,000kg/ha x 8ha = 16,000kg.

For a 100-cow herd, this would equate to 160kg/cow or a rotation length increase of 10 days (160/16kg per cow/day). 

Grazing at a lower cover of 1,600kg/ha would extend the round by eight days – two extra days are very significant.

This is an option that I have used with silage ground ¾ mile down the road from the farmyard. As it is after-grass, pre grazing covers of 2,000kg/ha can be easily grazed down to zero, resulting in excellent quality grass in the subsequent rotation, (final grazing round). This ground will then continue to grow over winter owing to its clean base. The secret to maximising growth on this area is slurry application to replenish nutrient off take from the soil and also a discipline on your behalf to avoid grazing this area until it reaches a PGC of 2,000kg/ha or above.

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