Grazing and row spacing effect on barley

By BCG Staff and Contributors
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Take home messages

  • Dual purpose barley grown after grain legumes produced the highest yield and quality of forage by GS30.
  • Grazing barley at GS30 increased grain yield by 0.3t/ha.
  • Yield was unaffected by row spacing or previous crop type, but protein was higher in barley grown following grain legumes.

Background

Dual purpose cereal crops can fill the early winter feed gap for livestock producers, with the vigorous early growth of cereals providing feed faster than pastures can. Previous research conducted as part of the Grain and Graze project has shown that if crops are grazed early (before stem elongation), the residual leaf matter is able to recover without large penalties on grain yield or quality (Frischke and Ick 2014).

While the effects of preceding crop types and row spacing on yield in grain-only crops has been widely investigated by BCG, no previous studies have examined how these factors might influence the amount of feed provided by dual purpose crops, or how well they are able to recover yield following defoliation.

Aim

To investigate how previous crop type and row spacing influence the amount of forage that dual purpose cereal crops produce, and how well they recover from grazing.

Paddock details

Location: Kalkee
Annual rainfall: 467mm
GSR (Apr-Oct): 374mm
Soil type: Clay

Trial details

Crop type: Fathom barley
Treatments: Refer to Table 1
Target plant density: 140 plants/m²
Seeding equipment: Knife points, press wheels set at 225mm (9 inch), 305mm (12 inch) and 380mm (15 inch) row spacing
Sowing date: 24 May
Replicates: Four
Harvest date: 20 December
Trial average yield: 7.8t/ha

Trial inputs

Fertiliser: Granulock Supreme Z + Impact @ 50kg/ha at sowing and 100kg/ha on 19 July + 100kg/ha urea on 23 August

Pests, weeds and diseases were controlled according to best management practice.

Method

One factorial replicated trial was sown as a split-split plot design over the top of a failed 2015 stubble type by row spacing trial (Table 1). The crop types in the 2015 included Derrimut wheat, Compass barley, Bonito TT canola, Fiesta faba beans and Jumbo2 lentils. In 2016 plots were sown over the different stubble types on 225mm, 305mm or 380mm row spacings. Grazing was simulated at GS30 (8 August) using a line trimmer, cutting the crop to 7cm high.

Assessments included emergence counts (26 days after sowing), crop biomass analysis at grazing time and at anthesis and grain yield and quality parameters.

Feed quality was analysed in the 305mm row spacing treatment at GS30, but replicates were combined into one sample per treatment meaning statistical analysis was not possible.

To measure plant recovery, biomass cuts of grazed (GS65) and ungrazed treatments (GS70) were taken on the bean and wheat stubble on all row spacings.

Table 1. Row spacing, grazing and previous crop type treatments used in the experiment.

Grazing and row spacing effect on barley table 1

Results and interpretation

Biomass

Row spacing had no effect on plant establishment (P=0.25) with mean establishment being 123 plants/m². There was also no significant effect of previous stubble type on establishment.

Previous crop type had an effect on biomass at GS30, but no main effect or interaction between row spacings was apparent. The pulse crops presumably provided more nitorgen (N) to the subsequent barley crop which was able to support more vigorous initial growth. The barley on barley rotation presumably had less N to support early growth, and possibly higher root and foliar disease pressure.

With ample rainfall at the Kalkee site the crop was not limited by any nutritional or moisture
constraints. Grazing was the only treatment to significantly affect dry matter at anthesis, reducing it from 10.2t/ha to 8.6t/ha (P=0.006).

Table 2. Biomass (t/ha) of Fathom barley at GS30 sown over different crop types.

Grazing and row spacing effect on barley table 2

Feed tests

Feed tests were conducted on this trial to see if the previous crop type could influence the nutritional content of the barley at GS30.

Crude protein is the amount of true protein (composed of amino acids). Metabolisable energy is the feed energy available for animal growth. Digestibility (DMD) is the percentage of dry matter that is actually digested, and acid detergent fibre estimates the proportion of feed that is indigestible to animals. Dry sheep equivalent (DSE) grazing days assumes that each DSE requires 8 MJ ME/day. The higher the metabolisable energy the longer a DSE can be sustained for per kilogram of feed, therefore the more DSE grazing days.

Barley grown following lentils appeared to have the most favourable feed test (Table 3), however no conclusions can be drawn as feed tests were not replicated.

A 30kg lamb (growth rate of 300g/day) needs a minimum crude protein of 12.4 per cent, and lentils were the only previous crop type that provided this.

Table 3. Nutrient analysis of barley sown at 305mm at GS30 following different crop types.

Grazing and row spacing effect on barley table 3

Grain yield and protein

Grain yields were unaffected by row spacing or previous crop type, but were slightly improved by grazing; up from 7.7t/ha to 8.0t/ha (P=0.001).

This small increase may have been due to grazing reducing height of the crop, thus minimising lodging and header losses in the very favourable season of 2016.

Grazing decreased grain protein from 11.8 per cent to 10.8 per cent (P<0.001), probably due to the dilution of protein with greater yield. Proteins were higher following faba beans and lentils (Table 4), presumably due to higher N availability.

Screenings increased with row spacing from 3.1 per cent, 3.6 per cent and 3.8 per cent in 225, 305 and 380mm row spacings, respectively (P=0.002, LSD=0.5), however all are below five per cent.

Table 4. Grain protein of barley grown over different stubble types.

Grazing and row spacing effect on barley table 4

Commercial practice

This experiment has demonstrated that dual-purpose barley can produce more and higher quality feed by GS30 when grown following a broadleaf break crop, particularly legumes.

The higher levels of soil mineral N and reduced foliar and root diseases following legumes allows for more rapid early growth and N uptake, and in this experiment also resulted in higher grain protein.

Growers looking to maximise the amount of feed available from dual purpose crops should plant these following legume crops.

On-farm profitability

The improved whole-farm profitability that comes from including dual purpose crops and grain legumes in crop sequences in the Wimmera and Mallee has been widely studied and reported by BCG previously. This experiment demonstrated that the two practices are complimentary, and can allow growers to further increase profits if adopted in unison.

Acknowledgements

This research was funded by the Hugh D.T. Williamson Foundation.

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