Harvest stubble and weed seed management in wheat and barley

By Paul Breust, SFS

Key messages:

  • TrialsBookCoverHarvesting at 15cm is 20 per cent less efficient than harvesting at 30cm.
  • Harvesting at 15cm is 38 per cent less efficient than harvesting at 50cm.
  • Harvest efficiency increases at approximately 10% per 10cm of harvest height.
  • Additional fuel and hours from 15cm to 30cm cost $13/ha.

This trial was setup initially to determine the effects on harvest efficiency of harvesting low compared to harvesting high. Harvesting low, 15cm, to facilitate easy establishment of the following year’s crop is common practice. Harvesting low requires a drop in ground speed, and therefore harvest efficiency, to process larger quantities of dry matter due to the shorter harvest heights, ie 15cm compared to 30cm or 50cm.

Harvesting low is practiced to reduce stubble loads to manageable levels and can be achieved by baling or burning harvest windrows or simply spreading trash and straw evenly as possible across the header swathe. The work in 2014 has established how much slower the 15cm harvest process is and the additional fuel consumption required.

Aim: To test harvest efficiency and efficacy of weed seed capture techniques implemented when harvesting cereal crops of wheat and barley at 15cm, 30cm and 50cm.

Design

Replicated single block on farm trial using commercial equipment. Four replications by three harvest weed seed control processes. Report 5 design

Results

The crop of Bolac had a total dry matter of 8.4t/ha. Of that 3.04t/ha was grain and the remainder was 5.36t/ha of straw and chaff. A 43% harvest index.

Table 1: Variation in harvest speed due to harvest height at 90% engine load for a Case IH 9120. Streatham, Bolac wheat 2014.

Run Height cm Engine load % Speed km/hr Av. km/hr % Difference in km/hr Time 100ha @ 7.5ha/hr
1 15 90 4.3  4.35 15cm v 30 cm -20.18% 15cm
13.33hrs
2 15 90 4.4
3 30 90 5.1  5.45 30cm v 50cm -22.70% 30cm 10.66hrs
4 30 90 5.8
5 50 90 6.9  7.05 15cm v 50cm -38.30% 50cm 8.26hrs
6 50 90 7.2

At this site we adjusted the header speed according to 90 per cent engine load. It’s not surprising that harvesting at 15cm high is 20 per cent slower than harvesting at 30cm high. When we increased the height to 50cm we found that harvesting at 30cm was 22 per cent slower than 50cm. We suggest from this information that a rule of thumb is 10 per cent efficiency increase for every 10cm of harvest height. If a 100ha crop is harvested at 30cm it will take 20 per cent more time to harvest at 15cm. If harvested at 50cm it would take 38 per cent more time to harvest at 15cm.

Picture 1: Trash quantity from harvesting at 15cm. Case IH 9120.

Figure 1: Trash quantity from harvesting at 15cm. Case IH 9120.

Image 2: Trash quantity from harvesting at 30cm. Case IH 9120.

Image 2: Trash quantity from harvesting at 30cm. Case IH 9120.

Image 3: Left stubble height 30cm. Right stubble height 15cm.

Image 3: Left stubble height is 30cm. The stubble on the right is 15cm.

Image 4: Windrow burn treatment, right hand side treatment is 30cm.

Table 2: Variation in harvest efficiency due to harvest heights at Streatham, Revenue wheat 2014. JD 9770 STS header.

    Average of 7 or 8 strips Difference for 100Ha’s
Strip No. Harvest height Yield Km/Hr Ha/Hr* T/Hr L/hr Hours Litres
7 30 cm 4.455 7.16 8.86 39.86 61.43 11.29 693.5
8 17 cm 4.498 6.00 7.59 32.88 64.38 13.18 848.5

Table 3: Dry matter break down, Revenue wheat, Streatham 2014. Harvest index (HI) of 35% grain. Some frosting occurred and the dry finish impacted on HI.

Total crop DM T/ha Grain yield T/ha Stubble DM Av stubble DM T/ha
12.12 4.47 7.65 6.86
10.37 4.47 5.90
11.65 4.47 7.18
11.20 4.47 6.73
Image 5: 15cm stubble height JD 9770 STS.

Image 5: 15cm stubble height JD 9770 STS.

report 5 image 7

Image 6: 30cm stubble height JD 9770 STS.

Discussion

The aim of the trials is to accurately measure harvest efficiency impacts from a range of stubble heights in agronomic and economic terms. We will also evaluate the efficacy of harvest weed seed control techniques, costs and problems encountered specific to each technique.

Harvesting low and treating weed seeds has potential to reduce soil weed seed banks over time. This can assist with weed control and herbicide resistance management. However successfully burning windrows requires suitable weather conditions and a commitment of time and resources from the grower.

Livestock play an important role in many enterprises and they may impact negatively or positively on harvest weed seed control systems.

Harvesting high and burning has been standard practice for many growers in the western districts for many years. Hot burns can reduce weed seed banks but are much less effective than harvest weed seed control measures.

Burning is becoming more difficult to implement with increases in resources required and tighter restrictions on burning operations. Burning can also reduce pest and disease impacts from carry over stubble in cereal on cereal rotations.

What is the cost of harvesting at 15cm compared to 30cm?

Preliminary data for 9120 Case IH header from table 1 suggests that there is a $10/ha cost to harvesting at 15cm compared to 30cm. For a 100ha cereal crop it would take 2.67 additional hours to harvest a crop at 15cm compared to 30cm. Costed at contract harvesting rates of $400/hr this equates to $10.68/ha.

The 15cm height uses an additional 155l of fuel for every 100ha. At $1.50/l this equals $2.32/ha. Higher harvest heights are expected to provide additional savings of approximately $7.50/10cm of extra height.

Table 3: Cost analysis 15cm v 30cm harvest heights. *Estimated not recorded

Stubble height Time/100ha Harvest cost $ Fuel $  Cost $/100ha Cost $/ha Saving $/ha
15cm 13.33hrs 5332 1272 6604 66.04
30cm 10.66hrs 4264 1040 5304 53.04 13
50cm 8.26hrs 3305 789* 4094 40.94 13.90

There are many more variables to account for within the whole production year and we will collect data and information as 2015 season progresses.

We plan to measure and cost: time plus input savings from not burning, herbicides, impacts on crop establishment, fertiliser, soil moisture, weed seed banks, weed control, crop growth, pests, disease and yield for each treatment.

Percentages of weed seed above and below 15cm

The efficacy of any harvest weed seed capture techniques is determined by how many weed seeds are collected into the header front at harvest. For annual rye grass the shorter barley crop proved much more efficient at removing weed seeds (89%) than the taller Bolac crop, (65%).

Table 4: Weed seed per metre squared above & below 15cm harvest height. Bolac wheat Streatham 10/12/14

Weed Seed Species Av/m2 above 15cm % above 15cm
ARG 354 65
Giant Brome 80 64
Wild Oats 6.4 100
Av/m2 below 15cm % below 15cm
ARG 230 35
Giant Brome 51 36
Wild oats 0 0

Table 5: Weed seed per metre squared above & below 15cm harvest height. Gairdner barley Inverleigh 10/12/14

Weed Seed Species Av/m2 above 15cm % above 15cm
ARG 89 94
Av/m2 below 15cm % below 15cm
ARG 5 6
report 5 picture 7

Image 7: ARG & Giant brome in standing Bolac wheat Streatham.

report 5 picture 8

Image 8: ARG & Giant brome in 30cm stubble Bolac wheat Streatham.

report 5 picture 9

Image 9: Wild oats in 30cm stubble Bolac wheat Streatham.

report 5 picture 10

Image 10: Regrowth 2015 30cm stubble conventional harvest + burn treatment Inverleigh.

report 5 picture 11

Image 11: Regrowth 2015 windrow burn treatment Inverleigh.

report 5 picture 12

Image 12: Regrowth 2015 low harvest spread treatment Inverleigh.

Table 4: Barley regrowth numbers for each harvest management treatment.

Barley regrowth 2 Feb. 2015 Av/m2 (3m from the centre of each strip)
Harvest 15cm + Windrow burn 110.4
Harvest 30cm + stubble burn 9.4
Harvest 15cm + spread & direct drill 170.4
Cultivated with Speed tiller 168.9

NB. Found scattered wild radish plants at Inverleigh mainly in the 30cm height? Very few in 15cm harvest height. May only be due to paddock variability but worth looking at later.GRDCLogoStacked_TM_CMYK

SFS greatly appreciate the co-operation of Dr Nicholas Berry, Dr Chris Saunders, Gary Meek, Stewart Hamilton and Craig Drum for providing equipment and resources for these trials. This work is funded by GRDC as part of the GRDC project BWD 00024 – Maintaining profitable farming systems in retained stubble in Victoria & Tasmania.

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About BCG

Birchip Cropping Group Inc. (BCG) is a not-for-profit agricultural research and extension organisation led by farmers in the Victorian Wimmera and Mallee.
This entry was posted in Research results, Stubble management at harvest, Weed management and tagged , , , , , . Bookmark the permalink.

4 Responses to Harvest stubble and weed seed management in wheat and barley

  1. Pingback: 2014 field trials | The stubble project: Victoria and Tasmania

  2. Pingback: Desired stubble characteristics for the Wimmera and Mallee | The stubble project: Victoria and Tasmania

  3. Pingback: Stubble management at harvest | The stubble project: Victoria and Tasmania

  4. Pingback: Weed management in stubble retained systems in the south west | The stubble project: Victoria and Tasmania

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