To construct a grass wedge, you should graph your paddocks in order of decreasing grass cover, as shown below.

This can be done on a simple computer spreadsheet or even by using a pen and paper.

Decisions are made based on the demand line, which runs from your target pre-grazing height to your target residual. Target height equals: daily demand per hectare (stocking rate in LU/ha x 18) multiplied by rotation length (target 18 to 21 at this point) and target post-grazing cover (100kg to 150kg DM/ha).

Draw a straight line between your target pre- and post-grazing covers from your heaviest to lightest paddock.

Theoretical farm

  • Eight paddocks.
  • Grazing stocking rate: 3LU/ha.
  • Daily demand: 55kg DM/ha.
  • Rotation length: 21 days.
  • The target residual: 150kg DM/ha (4.5cm).
  • The target pre-grazing yield: 1,300kg DM/ha (9.2cm).

    • Optimum

    Thirteen days ahead; 702kg DM/ha farm cover.

  • This is the perfect scenario for grassland management, but don’t rest on your laurels.
  • The farm should be walked once a week to continue monitoring grass growth.
  • If grass growth exceeds 70kg DM/ha/day, the farm should be walked twice per week.

    • Surplus

    Sixteen days ahead; 864kg DM/ha farm cover.

  • Pre-grazing yields are too high and decisions need to be made to rectify the problem in order to maintain quality.
  • Firstly ensure the target residual is being achieved.
  • Remove surplus paddocks as silage – this should be completed as soon as possible so the paddock is back in rotation quickly.
  • Caution should be exercised so that excessive grass is not removed resulting in a deficit – look at the weather forecast. Will growth rates stay high?

    • Deficit

    Ten days ahead; 540kg DM/ha farm cover.

  • Do not speed up the rotation prior to magic day.
  • Increase the grazing area if possible or alternatively, lower stocking rate.
  • Supplement with concentrates or grass silage.
  • Re-graze area closed for silage if the pre grazing yield is not excessive.
  • Consider increasing fertiliser application provided weather forecast lends itself to growing conditions.
  • Work out your stocking rate in LU/ha and multiply the figure by 18 to find the daily grass demand in kg DM/ha.
  • Divide the figure into the average grass cover (kg DM/ha) on the farm.
  • Decisions are made based on the targets in Table 1 below.

    • Remember: a rough guide is that there are 250kg DM/ha in every centimetre measured above 4cm (residual).