Mind the gap

1 June 2017

A bit of number crunching now will boost your farm’s performance come spring.

Managing pasture supply and demand is a balancing act and the transition from winter to spring is particularly important. If there is too much pasture available, there’s a risk the feed could be wasted and go rank. If there is not enough, stock may be underfed and pastures that are overgrazed also take longer to recover. Both scenarios could reduce the growth and/or quality of subsequent pasture.

Estimating pasture availability

On most farms, an average pasture cover of 2200 to 2400 kilograms of dry matter per hectare (kg DM/ha) is a good target for the calving period in order to meet peak demand in spring. You may be able to assess how you stand in relation to this target from a farm walk or from historical records. There are also online tools, which can estimate your grass growth forecast based on regional data.

Alternatively, consider using a rising plate meter to measure the volume of grass in each paddock (or a representative sample of paddocks) and obtain your total pasture cover. Subtract your residual cover target (usually recommended at around 1500kg DM/ha) to determine the available pasture cover figure.

Assessing demand

The first step is to calculate how much feed your herd requires. This will depend on body condition score, stock breed and type (i.e. milking cow, dry cow, bulls etc.). Again, there are many online resources to help with these estimates or you can seek advice from your farm consultant.

You are now able to plot your pasture growth against your feed demand to predict pasture surpluses and deficits. Note that each farm’s curves will be different, so you will need to apply the principles to your own data.

Filling the gap

If your available pasture cover estimates are lower than your feed demand estimates, then you will need to consider a way to fill the gap, otherwise pasture, stock and production could suffer.

There are a number of ways to manage a feed deficit, including adding more nitrogen (N), increasing feed supply and reducing feed demand.

  1. Use nitrogen to grow more pasture
  2. This needs to be done at least a month before you reach the point where feed demand equals feed supply, so that the flush of growth arrives when it’s needed.

    Pasture response to nitrogen will depend on:

    • Available (nitrate) N in the soil – the less available N, the greater the response. In late winter/early spring it’s common for plants to be N-deficient. Nitrate can leach from the soil over autumn and winter. Clover doesn’t hold nitrogen very well in low soil temperatures and mineralisation of N from organic matter is also slow over winter. These factors reduce the levels of plant-available N in soil and increase the response to N fertiliser.
    • Soil temperature – the warmer the soil, the greater the response. Soil temperature should be consistently above six degrees Celsius (°C) at 9:00 am.
    • Moisture – too much or too little water will lower the response.
    • Application rate – there is a diminishing response at high application rates.

    N-Guru is a decision support tool developed by Ballance Agri-Nutrients and Ag-Research, which can help refine your decisions about nitrogen use. Using the N-Guru software program, you can target application to paddocks where it is likely to get the best response and manage grazing accordingly. N-Guru can also help you work through the economics of nitrogen application.

  3. Increase feed supply
    • Stand off stock or put them on paddocks that are due to go into a crop to avoid over-grazing and/or pugging and protect future pasture growth. Pugging lowers growth rates for the following three to four months at least. Note you will need to manage the environmental impact of using stand off areas/sacrifice paddocks.
    • Use or buy in additional feed
    • Slow the rotation
  4. Reduce feed demand
    • Lower your stocking rate (e.g. move later calvers or drystock off the farm)
    • Prioritise stock (colostrum and milking cows first, then springers and dry cows) and check intakes. Intake at calving is less than peak intake.

Remember, the sooner you take action, the more options you have and the quicker your pasture will recover.

For more advice on pasture management from winter through to spring simply contact your local Fonterra Farm Source TSR or Ballance Agri-Nutrient Specialist.

Article supplied by Ballance Agri-Nutrients