Crop and Pasture Science Crop and Pasture Science Society
Plant sciences, sustainable farming systems and food quality
Crop and Pasture Science

Crop and Pasture Science

Volume 66 Numbers 3 & 4 2015

Dual Purpose Cropping Systems

CPv66n4_FODual-purpose cropping – capitalising on potential grain crop grazing to enhance mixed-farming profitability

Lindsay W. Bell, Matthew T. Harrison and John A. Kirkegaard
pp. i-iv

CP13380Effects of grazing on crop crown temperature: implications for phenology

Matthew T. Harrison, Walter M. Kelman and Jim M. Virgona
pp. 235-248

Temperature is a fundamental driver of crop development, which has important implications for dry matter partitioning, the timing of flowering and grain yield. Although defoliation initially delays crop ontogeny, elevated microclimatic temperatures of up to 6–7°C significantly enhance post-defoliation development rates as the growing season progresses from winter into spring, mitigating the extent of the delay by anthesis. These results will be useful in designing experiments that propose using grazing or defoliation to manipulate crop flowering time and in interpreting the implications of defoliation on phenology and grain yield.

CP14241Effect of defoliation by grazing or shoot removal on the root growth of field-grown wheat (Triticum aestivum L.)

J. A. Kirkegaard, J. M. Lilley, J. R. Hunt, S. J. Sprague, N. K. Ytting, I. S. Rasmussen and J. M. Graham
pp. 249-259

Grazing of dual-purpose crops often reduces above-ground biomass by 50-80% but few studies have investigated impacts on roots.  We found little impact of grazing on rooting depth of wheat, except in early (4-leaf) and repeatedly grazed crops.  However the root length density in surface layers can be reduced after long-term grazing due to reduced proliferation of the nodal root system.

CP14319Forage and grain yield of diverse canola (Brassica napus) maturity types in the high-rainfall zone of Australia

S. J. Sprague, J. A. Kirkegaard, J. M. Graham, L. W. Bell, M. Seymour and M. Ryan
pp. 260-274

Experimental studies at six sites across the Australian high rainfall zone assessed the forage production and effect of defoliation or grazing on grain yield of spring, winter x spring and winter canola maturity types. Forage production ranged from 0.9-6.8 t DM ha–1 with an average of 2.4 and 2.8 t ha–1 of grain yield in defoliated and undefoliated crops, respectively. The study confirms the potential for dual-purpose canola across the HRZ when suitable maturity types are sown, managed and grazed appropriately.

European winter canola varieties (Brassica napus) can be successfully grown in southern Australia as spring-sown biennial dual-purpose crops. Currently available varieties sown in colder, long-season high rainfall environments can be sown from mid-October to provide 2.5 to 4.0 t/ha of forage from grazing (January to June) and recover to produce high grain yield (2.5 to 5.0 t/ha) with good oil content. Further refinement of crop and grazing management is warranted to maximize the potential benefits and reduce the risks of this new option.

CP13411Effect of timing and height of defoliation on the grain yield of barley, wheat, oats and canola in Western Australia

Mark Seymour, Jonathan H. England, Raj Malik, David Rogers, Andrew Sutherland and Allen Randell
pp. 287-300

Treatments simulating high-intensity ‘crash’ grazing to ground level or to a height of 5 cm reduced grain yield unless conducted early in vegetative growth. ‘Clip’ grazing by removing only the top 5–10 cm reduced grain yield to a lesser extent than crash grazing, and in several instances could extend the safe cutting period past Z30 and/or the end of July for cereals, or past mid-July for spring canola, provided the developing reproductive parts of all crops were not damaged.

DM production and grain yield of wheat, barley and oats cultivars, with and without defoliation, at a range of growth stages were measured in dryland farming systems in southern Australia. Results suggest that there are opportunities to incorporate the grazing of cereals to fill a winter feed-gap in the low-rainfall zone of southern Australia.

CP13421Evaluating the feasibility of dual-purpose canola in a medium-rainfall zone of south-eastern Australia: a simulation approach

Jeffrey I. McCormick, Jim M. Virgona, Julianne M. Lilley and John A. Kirkegaard
pp. 318-331

APSIM-Canola model was modified to simulate dual-purpose canola production to determine its feasibility in drier inland areas with a shorter growing season. The simulation analysis confirmed significant opportunities to achieve valuable livestock grazing from canola crops sown in an early window (before May) without compromising potential yield.

Australia’s high-rainfall zone is suited to the use of dual-purpose crops, which offer grazing for livestock and later produce grain, but no national analysis of cropping potential has been made. This analysis predicts large opportunities for dual-purpose wheat crops, with the potential to achieve 1700–3000 days of sheep grazing per ha and grain yields of 6–10 t/ha across the zone. Potential to expand the use of grain-only or dual-purpose wheat into new regions where they are currently rarely used appears significant.

Expansion of cropping into Australia’s high-rainfall zone offers significant potential for the use of dual-purpose crops such as canola, which offer an alternative to grass-based pasture and cereal crops. Crop simulation predicts significant opportunity to use dual-purpose canola crops successfully throughout the high rainfall zone, with average grain yields of 3.3–5.0 t/ha and 900–2500 days of sheep grazing per hectare. Early sown, long-season winter types offer much greater grazing potential than spring types, whereas grain yield of different phenology types is similar when the appropriate sowing dates are selected.

CP14200Integrating dual-purpose wheat and canola into high-rainfall livestock systems in south-eastern Australia. 1. Crop forage and grain yield

S. J. Sprague, J. A. Kirkegaard, H. Dove, J. M. Graham, S. E. McDonald and W. M. Kelman
pp. 365-376

A systems experiment conducted over 2 years evaluated the benefits of integrating dual-purpose wheat and canola, both individually and sequentially, for crop and livestock production in south-east Australia. Wheat provided more grazing than canola, while grazing both crops sequentially increased grazing by 43% compared to wheat alone. Grain yield was generally unaffected by grazing and was similar between individually and sequentially grazed crops. High yields of wheat and canola can be maintained after significant forage grazing, and access to crops sequentially can significantly increase the duration and amount of grazing achieved.

Short-term grazing of crops intended for grain production can provide an opportunity to increase the supply of winter feed and allows annual pastures to be rested from grazing early in the growing season. This study found that additional value to pasture productivity and utilisation through pasture deferment is likely to be low in a typical mixed-farming system in Western Australia. The main benefits of grazing spring-variety crops will come from early access to winter feed in the crop itself and improved animal growth, by avoiding the need to graze establishing annual pastures where the intake of livestock is restricted because of low forage accessibility.

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