27 March 1998


Target grass covers and

associated grass wedges at

certain critical times of the

year are detailed here by

BGS grazing consultant

Paul Bird

UNDER a rotational grazing system, grass the cows are about to graze will be longer than grass cows have just finished grazing. If you visualise all the grazing areas or paddocks in a line from the longest grass to the shortest you end up with a wedge shape or a GRASS WEDGE.

Use these target grass covers shown in the diagrams as approximate guides only. Each farm will have a slightly different set of grass cover targets depending on stocking rate, calving pattern and grass growth rates.

The amount of grass at different points along the grass wedge is described in terms of plate meter height or in other words what height the plate meter measures (compressed height). Add approximately one third on to the plate meter heights for a conversion to actual grass height.

The plate meter height has been converted into an estimate of the kilograms of dry matter a hectare (kgDM/ha) using the Ashgrove plate meter formula = dial m=reading x 125 + 640.

The most important figure to concentrate on is the average grass cover. This tends to affect grass growth and quality.

Grazing ground and silage ground that can be grazed is treated all as one and is included in the wedge. &#42

1. Average grass cover 2100kgDM/ha. Longest grass was last grazed in October

2. Actual turnout date will be determined by grass cover as well as calving pattern, and expected growth rates in February and March.

3. First grazing rotation should last until early to mid April or 40-60 days.

1. Summer wet areas – maintain average cover 2300kgDM/ha by removing surplus grass from rotation.

2. Summer dry areas – dont cut all surplus grass as silage, consider grazing some in July. Grass will need longer to recover from grazing as soil dries. Rotation should be lengthened to at least 30 days while there is still the grass quantity to do so.

When grass growth increases lengthen rotation to at least 40 days so grass cover increases for extended grazing. Average cover should be 2500-3000kgDM in October.

1. Grass cover may drop from turnout until grass growth exeeds animal demand for grass.

2. Average cover may drop to 1800-1900kgDM/ha.

1. Begin final grazing rotation some time in October. Graze between 1/40 and 1/60 of the farm per day. Average cover should be between 2500 and 3000kgDM/ha.

2. Finish grazing mid to end of November or when average grass cover drops below 1900-2000kgDM/ha.

1. If cows are grazing grass over 3000kgDM/ha take this out of the rotation for silage.

2. Maintain average cover on grazing area of 2200-2300kgDM/ha.

1. Now wait for turnout.

2. Dont graze with sheep.

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