Measuring grass using a simple system brings major advantages
Published 19/04/2011 | 14:02
What a difference one year can make. This time last year we were still feeding nuts and fodder-beet to lambed ewes. The only ewes getting any food but grass this spring are the few triplets and hoggets with twins.
By the end of March our grass was almost all eaten. To boost growth, 1 1/4 bags of 24-2.2-4.5 were spread on any ground that was grazed. The response has been really good with growth of 45kg/day recorded.
I measured grass with a plate metre. Firstly, record the number on the plate metre (eg 11,029). Then take 10 measurements randomly throughout the paddock.
This could give a recorded number (eg 11,141). To do your sum, subtract the first number from the second number and divide the answer by 20 to get the height of the grass.
11,141 - 11,029 = 112 ÷ 20 = 5.6cm.
This is your overall grass height so you subtract what will not be eaten. We aim to leave 3.5cm behind so there is 2.1cm to eat. Each centimetrein height is 200kg/ha, which gives 420kg/ha. Multiply by the size of the paddock -- 1.5ha gives 630kg of grass.
5.6cm - 3.5cm = 2.1cm x 200kg x 1.5ha = 630kg
Now allow for what each ewe will need to eat. A ewe rearing twin lambs of four weeks old needs 3kg/day. So a group of 50 ewes will need 150kg/day. We divide our total cover that will be eaten by our daily requirement (630kg ÷ 150kg) to give us 4.2 days grass for the 50 ewes and their lambs. I hope to manage my grass by using this method for this year. I will know when I have too much grass and I can take out paddocks for baled silage, and when there's not enough I can adjust numbers, spread fertiliser or wean the lambs earlier.