Profitable header set-up

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Key points

  • A lower stubble height can benefit subsequent crops by allowing better weed control with herbicides and faster crop establishment.
  • Harvesting low can cost more: each 10cm reduction in harvest height results in an average 10 per cent reduction in speed.

A flexible approach to managing stubble means that crops can be harvested high or low, depending on the season, stubble load and weed management, and that various strategies can be implemented post-harvest if required, depending on seeder type, the following crop and the farming system. Large stubble loads can potentially create challenges for all sowing systems and influence the ability of seedlings to emerge, the type and effectiveness of herbicides that can be applied, the ability of the crop protection chemicals to reach the intended target (soil, weed, pest or crop), and the effect that thick stubble load can have on emerging seedlings.

Harvest height

Harvesting high or using a stripper front are the quickest and most efficient methods and produce the least amount of residue, which needs to be threshed, chopped and spread as evenly as possible. As part of the GRDC’s Stubble Initiative several farming systems groups and CSIRO compared harvest efficiency and costs at different harvest heights (Table 1). As a general rule, there is a 10 per cent reduction in harvest speed for every 10-centimetre reduction in harvest height, meaning it can cost significantly more to harvest low.

Tall standing stubble is more suited to disc-seeding operations, or where post-harvest operations, such as grazing, mulching, incorporation (with or without added nutrients), baling or burning are planned. However, there can be some negatives to retaining tall stubble. Several groups found that wheat sown into taller wheat stubble (45cm compared with 15cm) received less solar radiation and may be exposed to cooler temperatures, which can reduce early growth and tiller numbers.

Table 1 Harvesting wheat in 2014 at Streatham, Victoria, at three harvest heights (engine load = 90%) using a Case IH 9120 header and cost analysis determined at contract rates of $400 per hour.

Stubble height Average speed (km/h) Percentage difference in km/h Time to harvest 100ha (hours) Harvest costs
($/100ha)
Fuel cost
($/100ha)
Cost ($/ha)
50cm 7.05 15cm vs 50cm = 38.3% 8.3 3305 789 $41
30cm 5.45 30cm vs 50cm = 22.7% 10.7 4264 1040 $53
15cm 4.35 15cm vs 30cm = 20.2% 13.3 5332 1272 $66

SOURCE: Southern Farming Systems

Weed management

Herbicide-resistant weeds have also become a problem in the modern stubble-retained farming system and harvest height is an important factor in the successful implementation of non-chemical harvest weed-seed control techniques, such as chaff carts, chaff decks, narrow windrow burning and, more recently, use of the Integrated Harrington Seed Destructor (iHSD).

The prototype iHSD was tested at Furner, South Australia; Inverleigh, Victoria; and Temora, NSW (by MacKillop Farm Management Group, Southern Farming Systems and FarmLink Research) in 2015-2016, at a constant speed of four kilometres per hour, to compare efficiency and cost. At Furner, reducing the harvest height from 30cm to 15cm increased the engine load by 10 per cent and fuel use by 15 per cent (Table 2). Activating the prototype iHSD further increased engine load and fuel use.

While the iHSD works well, the major issue is getting the weed seeds into the harvester front. Harvest height is critical. Research by Dr John Broster, from Charles Sturt University, shows that about 88 per cent of annual ryegrass was captured when harvesting at 10cm compared with 48 per cent at 40cm, depending on the season, ryegrass maturity at harvest and orientation.

Table 2 A Case IH 9120 harvesting wheat conventionally at 30cm, 15cm for baling or narrow windrow burning, or at 15cm with prototype iHSD in Furner, SA, in 2016.

Harvest height Grain yield (t/ha) Speed (km/h) Engine load (%) Fuel use (L/ha)
30cm 4.7 3.8 59.8 14.3
15cm 4.6 4.0 65.5 16.4
% change from 30cm to 15cm ns ns +10% +15%
15cm + iHSD 4.6 4.0 88.7 22.7
% change from 15cm to 15cm + iHSD ns ns +35% +38%

SOURCE: Mackillop Farm Management Group

Contributors to this research were: Birchip Cropping Group, CSIRO, Central West Farming Systems, FarmLink Research, MacKillop Farm Management Group, Riverine Plains, Southern Farming Systems and Yeruga Crop Research.

GRDC Research Codes BWD00024, CSP00186, CWF00018, CSP00174, MFM00006, RPI00009, SFS00032, YCR00003

More information:

Tony Swan, CSIRO
02 6246 5142
tony.swan@csiro.au