The almost forgotten technique in the UK of grazing cereals is something being widely practised across Australia in areas with widely varying rainfall levels. The Australian Grain Research and Development Council have produced a report titled Grain and Graze which sets out to evaluate the advantages and disadvantages of grazing a range of cash crops. We begin serializing this report over four coming issues to explore what is currently an untapped resource.
In Direct Driller Issue 3 we started looking at the potential opportunities of grazing winter crops. One of the greatest downsides is the risk of potential reduction in grain production and value due to grazing. This is where we pick up our content on grazing winter crops.
The Possible Costs (the downside)
The greatest downside risk is the potential reduction in grain production and value due to grazing. Results from Grain and Graze and other experiments show a wide range of yield and quality responses to grazing, from large reductions in grain yield to no yield losses or even increases in yield.
Reduction in grain yield
Grain yield data from 2004 to 2013 was collected across 53 cereal trials and 246 measurements in Western Australia, South Australia and Victoria where a grazed and ungrazed comparison could be measured (figure 1). This included wheat, barley, triticale and oats.
The results also include treatments where grazing was less than ideal, including grazing after stem elongation and when crops were under stress. These extreme treatments were imposed to appreciate the size of the yield and quality loss under adverse conditions.
Figure 1 highlights several key points:
• Cereal grain yield declined under grazing most of the time crops were grazed (78%), although the severity of the decline varied. The most common result was a yield decline of less than 250 kg/ha (25% of cases), with yield loss of between 250 kg/ha and 500 kg/ha occurring a further 15% of the time.
• Increases in grain yield were recorded in 22% of cases. The most common increase was up to 250 kg/ha although some larger gains were also recorded. The main reasons for the gains were attributed to reductions in lodging and less leaf disease, both a consequence of the removal of early growth by grazing.
• Large losses in grain yield were recorded (24% of cases). Four factors are believed to contribute to the large yield decline (table 1).
Canola
Grain data for grazed canola was limited. Most of the information was collected from Southern Victoria when the crop was sown at the conventional sowing time (late April to early May). Dry matter production was generally lower than cereals sown at the same time and the crop was slower to recover from grazing. This resulted in severe yield penalties. Best practice sowing guidelines for canola are to sow in Late March to early April, but this may be difficult to achieve in some areas because of stubble burning restrictions and weed control.
However, the availability of new canola varieties with strong winter habit provides the opportunity to sow by taking advantage of out of season rainfall (October through to February), where the crop is treated like a brassica fodder for grazing before being locked up and taken through for grain.
Changes to grain quality
Grazing resulted in a variable response to cereal grain quality. In some trials grazing improved grain quality characteristics, in other trials grain quality declined. The general conclusions from the spread in results are discussed. Protein Grazing did not affect the average grain protein in wheat but did with barley. Of the 64 wheat results examined, the average change in wheat protein from grazing was -0.1%, with a similar number of increases in protein recorded as decreases (figure 2).
The grain protein response to grazing for barley was different, with grazing more commonly resulting in a decline in grain protein (65% of the time). The average decrease across all trials for barley was 0.3% (figure 3).
The reasons for the decline in grain protein with grazed barley is not obvious. The results used in the analysis were collected across many years, using different varieties, nitrogen applications and time of grazing. This makes it difficult to identifying the possible reasons for changes in grain protein. The only loose association from the information is between grain yield and protein. It appears if grain yield is increased because of grazing, which happened in 40% of all the barley trials, then grain protein decreased (i.e. was diluted).
Grain size
Grain size in wheat and barley was generally not affected by grazing. Of the 54 comparisons with wheat and 42 comparisons with barley, slightly more than half the observations showed a reduction in grain size due to grazing. The average reduction in wheat was 1% and 2% for barley. The limited (less than 10) observations of grain size for triticale and oats showed similar responses to grazing as wheat.
Screenings
Screenings increased slightly for both wheat and barley as a result of grazing. More than 73% of wheat and 68% of barley comparisons showed an increase in screening compared to no grazing (figures 4 & 5). The average increase in screenings for wheat was 0.9% and 1.4% for barley. There was a slight correlation between increasing screenings and a reduction in yield after grazing.
Calculating the value of grazing crops
Calculating the value from grazing winter crops can be challenging because while there are immediate benefits through feed for livestock, the flow on effects are often more difficult to quantify. These flow on effects may include potential grain yield loss from grazing, building a ‘feed wedge’ because pastures can be spelled and making different livestock management decisions. The gains are realised within the farming system and not simply by comparing the potential loss of grain yield with the livestock gain when the crop is grazed.
Modelling undertaken by the CSIRO2 would suggest the potential benefits to whole farm profitability are very significant, in the order of AUS$100/ ha to AUS$200/ha. Attention to variety selection, early sowing, adopting best grazing practice and increasing stocking rate are all required to achieve this potential. Individual farm considerations such as weed and disease issues, chances of favourable climatic conditions to enable early sowing, adequate farm infrastructure and cash flow to run more livestock and the manager’s position on risk may temper these potential benefits.
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