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Sward measurement

Solution name: Sward measurement

Aim: Show different ways to measure swards and management tools

Description:

  • Grazed pasture is the cheapest feed for sheep production systems
  • It is important to maximise the production and maintain the supply of high quality grazing swards throughout the year on sheep farms
  • Grass is usually measured in kilograms dry matter per hectare (kg DM/ha)
  • Ideal grazing covers for sheep are between 1200-1500 kg DM/ha

    Topic: Nutrition and Management

    Production:  Dairy / Meat

    Animal Category: Adult / Lamb / Replacement

    Issue: Grazing and grassland management

    Level of Solution: Knowledge, Practical

    Country: Ireland

     

     

     

     

     

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    How to implement it

    Swards can be measured using the following techniques:

    1) Cutting and weighing

    • Quadrat (0.5 x 0.5m), shears, weighing scales and plastic bag are required
    • Place the quadrat on an area that is representative of the paddock or take a few quadrat cuts per paddock
    • Clip the grass in the quadrat to the target post grazing height with the shears
    • Place all the clipped herbage in the bag and weigh
    • Estimate herbage dry matter percentage and use the following calculation:
      • Weight of grass (kg) x grass DM% x 40,000 = kg DM/ha in the paddock

    2) Rising platemeter

    • The rising platemeter measures the compressed height of a sward, each of the mechanism ‘clicks’ represents 0.5cm of compressed height
    • Record the start number on your platemeter before taking heights in a paddock
    • Target 30 heights across the entire paddock in a ‘W’ pattern to give accurate representation of a paddock
    • Record the end number after taking your heights, subtract your start number and then divide by 2 to get your compressed sward height in cm, then divide by 30 if you took 30 height measurements
    • Compressed sward height = (start number-end number)/2 ÷ number of heights taken
    • Subtract your target post grazing height (e.g. 4cm) from the sward height of each paddock
    • Multiply the figure you get by 300 as there is typically 300kg DM/ha per cm in sheep swards
    • Automated platemeters (e.g. Grasshopper) can calculate sward height automatically and transfer data to online database or smartphone

    3) Sward Stick

    • Easy to use and low investment
    • Use gauge on side to show when swards are grazed out, growing, should be grazed or have covers too heavy for grazing

    How to use data:

    • Manually calculate the whole farm cover together with animal demand, days grazing ahead, pasture growth rate from last measurement etc. or use an online application e.g. PastureBase Ireland or Agrinet
    • Average farm cover is calculated by multiplying each paddock cover by its area, totalling all paddocks and then dividing by total area
    • Animal demands varies depending on age, stage of lactation etc. as a guide daily intake for ewes rearing twins will range from 2.4 kg DM from 1 week post lambing to 3.4 kg at 7 weeks post lambing
    • Pasture management decision support tools (e.g. PastureBase Ireland, Agrinet) automatically calculate growth rates, average farm cover, days grazing ahead, stocking rate and animal demand when all paddock covers and stock information are uploaded. Pasture management decision support tools create reports to show total pasture production for each paddock on the farm
    Expected benefits
    • Higher grass production, improved sward quality, extended grazing season, high feed value silage production, all of which increase animal performance and can reduce feed costs
    • Using applications (e.g. PastureBase/Agrinet) will also construct a comprehensive grassland database for your farm, determine the quantity of grass that can be grown and identify best and worst performing paddocks
    Prerequisites and/or limits
    • Need to invest in grazing measuring equipment
    • Need to learn how to use equipment correctly and how to calculate or upload paddock information to database

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