DAFWA research: Evaluation of dual purpose canola and cereals grazed with cattle
The grain yield of a wide range of canola and cereal varieties sown in mid April were unaffected by the grazing of cattle at a stocking rate of 20-22 dry sheep equivalent (DSE) per hectare (ha) for up to four weeks at Esperance in 2011. The grazed crops yielded the same as ungrazed crops sown at currently recommended times.
Aim
To investigate and demonstrate the importance of dual purpose crops (canola, wheat and barley) to improve the feed availability for cattle (in late autumn to early winter) in mixed farming systems of the high rainfall environment of Western Australia (WA).
Method
In separate paddocks (6.5ha) at the Esperance Downs Research Station we sowed one canola and one cereal experiment (Figures 1-4). The experiments were split plot designs with species and variety subplots randomised within grazing and time of sowing (TOS main plots) and three replicates. Dates of sowing were TOS1 = April 15 and TOS2 = May 18 and individual plots were 20m long x 1.44m. Yield was measured using machine harvest. The conventional/Clearfield canola blocks were treated as conventional canola and were sprayed with Lontrel and grass herbicide mixes, while RoundupReady blocks were sprayed with glyphosate at six-leaf stage only.
TOS2 plots were not grazed. Grazing of the TOS1 plots with cattle commenced on 15 June 2011 which was the earliest date allowable within the constraints of chemical withholding periods (e.g. Jockey treated canola seed). Grazing of cereals ceased four weeks later on 14 July, while the canola grazed plots were divided into two treatments – a short duration where grazing ceased on 4 July after 18 days (labelled two weeks), and a second treatment where cattle continued to graze until 14 July (labelled four weeks).
Stocking rates during the four week grazing period varied from 12–30 DSE/ha during the first two weeks of grazing as the grazing area available was manipulated to ensure adequate grazing pressure. The average stocking rate was 22DSE/ha for cereals and 20DSE/ha for canola.
Growing season rainfall in 2011 (April-October) was 358mm, slightly below the long term average (LTA) of 374mm. Winter rainfall in 2011 was below average at 121mm (LTA = 185mm) whilst October rainfall in 2011 was a record of 113mm (LTA = 43 mm).
Results
Canola
The majority of varieties handled grazing well, with similar yields to the ungrazed 1TOS treatments and ungrazed 2TOS treatments (Figures 1 and 2). Exceptions were 45Y22RR which lost yield if grazed for four weeks (but even then still produced 2.4t/ha - equal to any of the other Roundup Ready lines grazed for four weeks); CB Agamax which lost yield if grazed for four weeks compared to sowing later (2TOS); and Hyola 404RR which lost yield if grazed for four weeks but handled a shorter period of grazing well.
Cereals
Despite being grazed past stem elongation (Z30) the yield of cereals was not reduced by grazing for four weeks (Figures 3 and 4). In some instances sowing in mid April and grazing led to increased yield compared to sowing in mid-May (e.g. Endure, Wedgetail, and Urambie).
Preliminary analysis of yield component data indicates that while grazed cereals produced less biomass at maturity than ungrazed crops, they had similar number of heads, which filled to similar levels and subsequently grazed plots had improved harvest index. Record October rainfall is thought to have favoured the later maturing grazed plots.
Conclusion
Our preliminary analysis of the 2011 experiment indicates that a wide range of early sown canola and cereal varieties grazed by cattle maintained grain yield at Esperance in 2011. This confirms research conducted in other parts of Australia and experiences of growers who have adopted the practice in the region in recent years.
In WA we have extensive areas of crops sown from late April to late May and relatively low stock numbers (high crop to livestock ratio). As a result, we believe there is a need to determine how the mainstream crops sown in a more typical window (early to mid-May) recover from grazing as the opportunities for early sowing (March to mid April) are limited in many areas. It may be that lighter grazing (clip grazing) of more extensive areas is a better system to capture value from grazed crops for WA mixed farming systems.
An essential question is the level of recovery of crops from a wider range of grazing intensities (height/duration/time) sown over a wider range of dates (late April to late May) and at more locations with variable season length to better assess the potential for WA mixed farming systems.