Grazing Winter Crops – FAQ – 1/3

All this week on Table Talk, we are focusing on the theme of Grazing Crops.

Livestock in mixed farming systems are regularly exposed to periods of forage deficit (feed gaps) that can reduce both animal performance, but also lower the ‘safe’ carrying capacity of the farm (CSIRO, UTAS). When managed well, grazing crops can assist with flexibility and productivity in a mixed farming system.

With many already grazing winter crops, we thought it was the perfect time to bring together findings from over a decade of research on grazing crops throughout Australia.

In this first post, we will look at the following questions:

  1. How can cereal grain crops be utilised by livestock?
  2. Does variety matter?
  3. When can I start grazing?
  4. How do I graze? What stocking rate should I use?
  5. When should stock be removed?

How can cereal grain crops be utilised by livestock?

Grain and Graze3 (GRDC) present six ways in which cereal grain crops can be utilised by livestock:

  1. Grazing crops during the late vegetative and early reproductive phases with the intention of preserving most – if not all – of the grain yield.
  2. Sacrificial grazing during mid-late reproductive phases, where there is little prospect of a commercial grain harvest, such as in a drought.
  3. Conserving crop biomass prior to harvest, where crops may be cut either for hay (usually early in reproductive growth) or for whole-crop silage (later in reproductive growth). This option can be attractive at times when there is a scarcity of fodder in other regions.
  4. Grazing standing crops after maturity, where livestock utilise both the grain and the stover. This is often done to carry other fodder over into the summer period when it may be in short supply.
  5. Grazing dry crop stubbles after harvest, traditionally done in many cropping systems
  6. Grazing stubble regrowth after harvest. This often occurs with weak perennials such as grain sorghum; if the crop is not killed at harvest re-sprouting of shoots can occur, producing new vegetative biomass that is able to be grazed.

Our focus in these blog articles will be on #1.

Does variety matter?

Phillip Barrett-Lennard of agVivo stated that variety does and doesn’t matter:

“All crops can be grazed. The so-called “dual purpose” varieties are winter types with a vernalisation requirement for flowering, and can be sown very early.”

Kondinin Group (2016)  stated “A common misconception amongst many Western Australian farmers is that special dual-purpose crop varieties must be sown when grazing crops.”

When can I start grazing?

  • Earliest time to start grazing is when the plants are well anchored and reach the tillering stage (NSW DPI)
  • Grazing can start as soon as cereal plants are well anchored – use the ‘tug test (GRDC funded research)

How do I graze? What stocking rate should I use?

Dr Hugh Dove’s GRDC funded research found that a useful ‘rule of thumb’ is to graze with about 1000kg of stock liveweight per hectare. This could be, for example, 33 sheep at 30kg each or three cattle at 330kg each. He stated:

  • Very low stocking rates – about 10 dry sheep equivalents (DSE) per hectare – give good liveweight gains because there is so much cereal forage. Although they are uneconomic because they do not make best use of it.
  • At a higher stocking rate – from 15 to 20 DSE/ha – ‘patch grazing’ can develop, where stock overgraze cereals in patches while the rest of the crop continues to grow and becomes less preferred by stock.

CSIRO experiments used six fields involving a variety of stocking rates, grazing regimens and different cultivars at Canberra, ACT, and Young, New South Wales, in southern Australia in 2007 and 2008. They found that:

  • Early sown crops supported 800–2500 DSE grazing days from June to August, and recovered to produce high seed yield (2.8–5.6 t/ha) with high oil content (42–48%).

Phillip Barrett-Lennard of agVivo stated that “don’t get hung up on stocking rate”.

“The initial thinking in WA was that a high stocking rate for a short period was preferable to avoid overgrazing and to speed up crop recovery. However we have found over time that due to low stock numbers and large paddock sizes, implementing more intensive grazing management on crops in WA is often not practical. The alternative is usually a low stocking rate over a longer period. This has proved to be very successful in the vast majority of cases. It reduces labour (shifting stock) and the need for temporary electric fencing (reducing paddock size). The only downside of a low stocking rate is that livestockdual pur will often unevenly graze a crop. If the grazing period is relatively short, say 2 or 3 weeks, the unevenness rarely causes too many problems.”

Image: The Land – Oliver Wythes, Rockdale Grazing Company, “Canford”, Canowindra, monitors the growth

When should stock be removed?

  • Dr Hugh Dove’s GRDC funded research stated that timing of stock removal rather than stocking rate is the critical factor to ensure good recovery and yield.
  • Frost injury to grazed crops can be severe, particularly if crops are only a few centimetres high and the soil is loose and dry. Under severe frosty conditions, stock should be removed nightly. (NSW DPI)
  • Stock should be removed before GS31 (stem elongation) to prevent yield losses (FarmLink Research through Murrumbidgee Grain & Graze Project (2004-2008))
  • Grazing is an ‘unsafe’ period after the initiation of reproductive stem elongation (GS30 in cereals or stem elongation in canola) (CSIRO Agriculture Flagship & Kalyx Young).
  • To avoid risk of yield loss in canola, residual biomass levels greater than 2.5 t DM/ha are required if grazing continues after late July. A similar critical level is less clear in cereals but appears to be about 1-1.5 t DM/ha required at lock-up in mid-August.  (CSIRO Agriculture Flagship & Kalyx Young).

In our second post, we will look at the following questions:

  1. What is the nutritive value of grazing crops? What growth rates should I expect?
  2. What livestock health issues should I be concerned about?

And in our final post, well will look at the following questions:

  1. Does grazing winter crops reduce grain yield?
  2. Have any cost benefit analyses been done?
  3. What else should be considered?