Grains Research and Development

Date: 31.08.2015

Profitable pulses – it’s all about the harvest window

Author: Tim Weaver

Key points

  • Correct desiccation timing provides uniformity in seed moisture
  • Harvesting at the optimum moisture content means fewer grain defects
  • Premium prices come from harvesting at the optimum moisture
  • Correct storage of pulses ensures optimum germination if retaining for seed
  • Setting up header front and drum speeds correctly improves pulse quality 

With this year’s pulse production up on previous years, buyers may be more discerning about quality; research continues to show the benefits of harvesting at the optimum time

Image of a harvester

Take extra care when harvesting pulses for seed to reduce grain cracking, even if this means making a poor sample. Gentle harvesting will give the best seed quality.

PHOTO: Pulse Australia

When it comes to delivering high-quality pulses likely to attract price premiums from buyers, there are several factors to consider.

Grain quality and prices can also suffer if there is mechanical damage, weathering and seed staining. Moisture levels at harvest also affect the quality of grain in storage.

If harvesting for seed, germination is improved if grain is harvested at 12 to 14 per cent moisture and stored in aerated silos, or graded and bagged as soon as possible. Crop-topping with herbicides before crop maturity may reduce grain quality and seed germination.

Harvest delays cost growers and the pulse industry a lot of money. It is not unusual to see a four-to-six-week spread in the harvesting of pulse crops that were established on the same sowing rain. Many late-harvested crops are often about eight per cent moisture, whereas the maximum moisture content for receival is 14 per cent with market preference at 12 per cent.

There are several reasons why delaying the harvesting of pulses might be tempting:
  • a clash with wheat or barley harvesting;
  • the perception of a greater chance of achieving premiums for Prime Hard or Australian Hard wheat or malting for barley, even though in reality the premiums for harvesting pulses at the optimum time are often greater;
  • the false perception that pulses tolerate
  • the weather well;
  • uneven ripening if not desiccated or windrowed, especially when grown on heavy clay or variable soils; and
  • the false belief that pulses are slower or more difficult to harvest (this is not the case if they are desiccated and the header is correctly configured).

Pulses can be profitable if a professional approach is taken to production and marketing, rather than treating them as ‘secondary crops’ planted last, harvested last and sold to the nearest buyer.

Delays lower yield

Image of windrowing

When windrowing faba beans set the cutting height just below the bottom pods with the reel following the top of the crop. Set the reel speed slow. The delivery opening in the windrower needs to be large enough to prevent blockages or there will be lumps in the windrow. Dense and tightly knit windrows will produce the best results. Curing usually takes 10 to 12 hot days. However, heavy infestations of radish and other weeds could delay drying.

PHOTO: Pulse Australia

Yield losses increase the longer harvest is delayed. For example, while faba beans are not normally prone to pod splitting and shelling out in all but extreme wet weather conditions, they are prone to pod splitting and pod drop after weather events if the plant has dried.

From a financial perspective, grain losses from a two-to-four-week harvest delay have ranged from $93 to $238 per hectare, depending on seasonal conditions.

Most losses were caused by pod loss at the header front or from unthreshed pods lost out the back of the machine.

In faba beans, for example, lodging can increase the longer they are left standing, and the risk is higher if the crop is high yielding and planted on wide rows.

It is also worth considering what a loss of moisture below the Australian pulse receival standard of 14 per cent moisture content maximum leads to, for example:  

  • 500 tonnes of faba beans at 14 per cent grain moisture and $450/t is worth $225,000; and
  • the same grain harvested at 8 per cent moisture delivers 470t and at $450/t is worth $210,600 – a loss of $14,400.

Quality losses

Grain quality deteriorates the longer mature pulses are exposed to weather.

For example, seed coats of faba beans are prone to cracking if exposed to wetting and drying from rain or heavy dew.

Expansion of the seed as it absorbs moisture and then contraction as it dries weakens the seed coat, rendering seed more susceptible to mechanical damage during harvest.

Levels of cracked and damaged grain can be as high as 50 per cent in extreme cases of weathering and prolonged rainfall.

Faba beans and broad beans that do not meet the number one receival standard of six per cent maximum defective beans need to be graded. This results in:

  • $15 to $25/t in grading costs; and
  • downgrading of the seconds into the stockfeed market at a value of $120 to $140/t.

Early harvested pulses are more resilient to breakage during harvesting and subsequent handling, even at low moisture contents.

Some faba beans and broad beans are processed into dahl or flour by removing the seed coat (hull) and splitting the cotyledons. However, the visual appearance is still critical for marketing.

Older seed, darkened with age, splits better than new-season grain. The milling process uses abrasive-type mills to gradually abrade the seed coat from the cotyledons and is reliant on the seed coat being firmly attached to the cotyledons.

Cracking and weakening of the seed coat before processing substantially reduces the recovery percentage of splits and the quality of the final product.

Faba beans and broad beans that have been weathered after rain are difficult to thresh at harvest and often contain higher levels of unthreshed pods and pod material.

Darkening of the seed coat is caused by oxidation of polyphenol compounds (tannins). Conditions that accelerate seed-coat darkening include rainfall, cool-to-mild temperatures, high humidity and sunlight.

While there is usually no direct penalty or discount for a moderate degree of seed-coat darkening, it does have a significant impact on the marketability of the product and the reputation of the Australian industry as a supplier of high-quality product.

Quality is becoming increasingly more important as Australian traders attempt to establish market share against other bean-exporting countries (France and the UK).

It is likely we will see more segregation and premiums paid for lighter-coloured, large-seeded faba beans and broad bean types as new varieties with these traits are developed and the Australian industry becomes more quality conscious.

Weathering and mould

Weathering of seed caused by delayed harvesting can increase mould infection. High levels will also cause darkening of the seed coat. Humid (above 70 per cent relative humidity), wet conditions favour the development of a range of fungi in late-harvested bean crops.

While Alternaria species usually predominate, Aspergillus, Cladosporium and Penicillium species may also be present.

Increased risk of late ascochyta infection can develop on dry, senescing pods under wet conditions, and can penetrate through to the seed in susceptible varieties.

The current export receival standard for visible ascochyta lesions is a maximum of one per cent on the seed cotyledon (kernel). Current Australian Pulse Standards are available on the Pulse Australia website.

Native budworm can occasionally attack senescing faba beans and broad beans, particularly where rainfall has softened the pod.

Insect-damaged seeds are classified as defective beans and cannot exceed the tolerance level of three per cent.

Marketing opportunities

Delayed harvest can often mean missing out on premiums being paid for early-harvested, high-quality crops. This is the case in some years, with the exception of seasons that encounter major production problems leading to a ‘shorts’ marketplace.

Weathering and mechanical damage are also more likely in late-harvested crops.

Early harvest also gives some degree of control over how and when the crop is marketed.

 

Quick tips for pulse harvesting

Pulses are easily threshed, so open the concave clearance and reduce the drum speed (Table 1).

If there are summer weeds the drum speed may need to be increased to ensure weeds do not block the machine. Pulses are larger than wheat so a concave with many wires or blanked-off sections can stop grain separation. For best performance, remove alternate wires and blanking-off plates. A clean sample can be achieved with maximum wind settings and barley sieve settings.

If there are summer weeds, blank off the rake at the back of the sieves to stop them entering the returns. Summer weeds may cause walkers and sieves to block completely, causing high grain losses.

Take extra care when harvesting pulses for seed to reduce grain cracking. Gentle harvesting will give the best seed quality. Rotary harvesters are gentler on the crop and will generally cause less grain damage than conventional harvesters.

Faba beans can be harvested with minor adjustments and modifications. Open-front or pick-up fronts are best suited to the job.

Harvest faba beans as soon as they mature because the pods will fall if harvest is delayed.

The crop varies in height from 15 to 80 centimetres with pods held up in the canopy so direct heading without crop lifters is possible with open front and closed front machines, although some fingers may have to be removed when using closed-front machines.

Faba beans thresh easily but are prone to cracking so adjust thresher speed (400 to 600 revolutions per minute) and concave (10 to 30 millimetres) to suit. Removing alternate wires and blank-off plates from the concave will help reduce cracking. If possible cover the rasp bars with plate.

Harvesting grain at high moisture levels (up to 14 per cent) minimises cracking. Harvest early before summer weeds become a problem to reduce clogging, staining and sample contamination. Desiccating the crop will kill summer weeds and ensure even crop ripening.

 

   Chickpeas  Faba beans
 Green lentils
 Red lentils
 Lupins Field peas
Vetch
Table 1 Harvester settings for pulses
Reel speed
 Medium Slow
Slow
Slow
Slow
Medium
Slow
Spiral clearance  High  High Low
Low
 High  Standard Low
Thresher speed
400 to 600rpm
400 to 600rpm
350 to 450rpm  350 to 450rpm
400 to 600rpm
400  to 600rpm
400 to 600rpm
Concave clearance
10 to 30mm 15 to 35mm
20 to 30mm
10 to 20mm
10 to 30mm 10 to 30mm
10 to 30mm
Fan speed
High  High High
High
High
High
Medium
Top sieve
32mm 32 to 38mm
32mm 16mm 32mm  25mm 25mm
Bottom sieve 16mm 16 to 19mm
8 to 16mm
 3 to 10mm
16mm  16mm 10 to 16mm
Rotor speed* 700 to 900rpm
700 to 900rpm
350 to 450rpm
350 to 450rpm 700 to 900rpm
700 to 900rpm
 Slow

Modifications and aids

Image of harvesting tool

Figure 1 Finger tyne reel with four finger guards and open second fingers to reduce vibrations

Image of farm machinery

Plastic extension fingers fitted to the knife of a harvester can save significant losses for little financial outlay. Pods that would have fallen in front of the knife are caught on the fingers and pushed into the comb by the incoming crop.

PHOTO: Gordon Cumming, Pulse Australia

Early harvesting can solve many problems and losses are reduced as the pods are less prone to shattering or dropping. The crop is also easier to gather because it stands more erect, allowing the harvester front to operate at a greater height and reducing the dirt, rocks and sticks entering the harvester.

A straw chopper may be of value to chop up the stubble and spread it uniformly. Crop lifters are not required unless the crop is badly lodged or late-sown and drought-affected.Set the finger tyne reel to force material down onto the front. For example, moving the broad elevator auger forward can improve the feeding of light chickpea material.

Vibration due to cutter bar action, plant on plant, reel on crop impact and poor removal of cut material by the auger all cause shattering and grain loss. Grain loss can be reduced by harvesting in high humidity or at night to minimise pod shattering. Avoid harvesting in extreme heat.

Finger reels are less aggressive than bat reels and cause fewer pod losses. Double-acting cutter bars reduce cutter-bar vibration losses. Four finger guards with open second fingers also reduce vibrations (Figure 1, right).

A lupin breaker is an inexpensive device to increase harvesting capacity and reduce grain loss. It is a small, serrated plate that attaches to the front spiral and creates an aggressive, positive feed action to clear cut material from the front of the knife.

Other options include the Aussie-air, Harvestaire, the Vibra-mat, extension fingers, extended fronts, platform sweeps and draper fronts.

Assess carefully any investments in these technologies as a small area of pulses may not justify their cost to the business.

Image of faba bean comparison

The optimal stage to desiccate or windrow a faba bean crop is when most seeds have reached physiological maturity (90 to 95 per cent of the crop). This is assessed as being when the hilum (scar-like area where the seed attaches to the pod) is turning black on the seeds in the upper (25 per cent) pods. At this stage the upper pods are still bright green and there is still green leaf present, but the lowest pods are starting to turn black and have seeds with completely black hilums.

PHOTO: Gordon Cumming, Pulse Australia

More information:

Tim Weaver,
0427 255 086,

timw@pulseaus.com.au;

Pulse Australia

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Why frost needs a risk-management mindset

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Pulse pioneer’s chapter in cropping history

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