Harvesting

1. Aim of soybean harvesting

The aim at harvest is to collect the maximum amount of soybean grain: 

• at the optimal time 

• with the highest possible sample quality, and 

• with the lowest possible losses. 

In addition to the seasonal conditions, there are many decisions that set a crop up for a successful harvest. For example, the grower and harvester operator can: 

• Ensure that agronomic practices and crop management are optimal for harvest. For example, decisions on paddock choice and preparation, row spacing, crop nutrition, variety choice, time of planting, crop nutrition, plant population, evenness of establishment, and weed and pest management affect the ease of harvest.

• Minimise pre-harvest losses and damage to the crop during the season. For example, using controlled traffic lanes and wide booms for spraying operations will minimise crop damage.

• Harvester maintenance, calibration and correct set-up for each crop will enable timely harvesting.

• Minimise gathering losses at the header front.

• Minimise processing losses in the harvester.

2. Terminology

In Australia local terms to describe grain harvesting equipment crops can be confusing as they differ to the terminology used in Europe, Canada or the United States of America (USA), where much of the world’s harvesting machinery is manufactured.

In the USA, the detachable front that cuts the crop is referred to as the header, head or header front. The header is designed differently to ‘head’ (or cut the grain heads off) different crops. A corn or maize header front is a different design to that used for wheat or soybean (Figure 1). 

In the USA, Europe and Canada, the rest of the machine to which the header front is attached is called a combine harvester (or combine for short). The term combine harvester refers to the combination of grain harvesting steps that are completed within a single machine, namely reaping, threshing, gathering and winnowing. Combine harvesters are one of the most economically important, labour-saving inventions and are credited with significantly reducing the proportion of the population engaged in agriculture. 

In Australia, the entire unit (combine harvester + header front) is sometimes colloquially referred to as ‘a header’. 

3. Crop management considerations

The interaction of crop management decisions such as row spacing, plant population, soybean variety choice and time of planting directly influence the degree of difficulty of harvesting operations. Soybean agronomic and crop management information is provided in the other modules of this manual.

Soybean plants grown in a narrow row spacing, e.g. 30 cm, and/or at a dense plant population, tend to grow taller and produce thinner, single stems with less branching and fewer pods on branches. The height from the ground to the lowest pods may be greater, allowing ease of harvest, but the yield may be lower due to plants being overcrowded and experiencing periods of moisture stress or resource constraints during the season.

Conversely, in crops with a wide row spacing (>75 cm), the canopy may not cover the interrow space, allowing weeds to establish or, depending on seasonal conditions, the crop may lodge into the interrow where it is difficult to pick up at harvest. In crops where the plant population is below the target recommended for the variety and the location, plants may be shorter in height with a low height to the bottom pods presenting a difficulty for header operators and the risk of picking up soil that downgrades the sample. 

4. Harvest timing and use of desiccants

Harvest timing

The ideal time to harvest soybean is when the grain has reached physiological maturity (see growth stages in the Plant growth module) and has dried naturally to a safe storable moisture content (MC) of 12–14%. Grain that is too dry (MC <10%) will result in losses due to increased risk of pod shattering and damage to the grain during threshing, e.g. splits. Grain that is too moist (MC >15%) will likely not thresh properly, increase the risk of blockages in the harvester and increase the risk of the grain developing mould during transport and storage.

Moisture measurement of the ripening soybean grain is critical, especially in humid conditions. Calibrate moisture meters (whether hand-held or on-board) against a reliable standard each season.

In some situations, harvesting at a higher than recommended grain moisture content may be unavoidable and must then be followed by physically drying and aerating the grain. Refer to the Safe storage module for more information.

Desiccants

Under normal growing conditions and with the even maturity of most of the current commercial soybean varieties in Australia, the use of crop desiccants/harvest aids like diquat (example trade name Reglone®) or glyphosate (example trade name Roundup PowerMax®) is not usually required. 

Desiccants may occasionally be required to manage green weeds in mature soybean crops, hasten leaf drop or facilitate more uniform harvest conditions in crops that have suffered damage during the season. 

Follow all label instructions including withholding periods. Refer to the receival standards before using any chemical on the crop and ensure that restrictions and withholding periods are strictly observed.

If the crop may be kept for planting seed ensure that the desiccant label states that it is safe to use on seed crops. 

Weigh up the costs of a desiccating operation including crop damage and losses due to running down some of the crop during application. Consult an agronomist experienced in desiccation of soybean crops when deciding when and how to desiccate. Remember that using a desiccant will only dry out (i.e. desiccate) what is there; it will not advance the maturity of the crop. Desiccating a soybean crop before it is physiologically mature will likely result in green seeds. 

In seasons with high pressure from pod-sucking bugs (e.g. green vegetable bug or Riptortus) or where these pests have not been adequately controlled earlier in the crop, uneven ripening can occur. In severe cases, pods may appear mature (brown) whilst the stems are still green. See the Pest management module in this manual for details on managing pod-sucking bugs in soybean crops.

Assessing soybean maturity 

The following information is most relevant to high rainfall coastal production areas, where use of desiccants to assist harvest is more likely.

In the lead up to harvest judging the right time to desiccate and harvest can be difficult. In this video Matthew Leighton, Bundaberg Canegrowers and Grain in Cane Co-op. shares some practical tips to help with these important decisions.

Preparing for harvest – with focus on coastal soybean crops

The first indicator that harvest is imminent is the green leaves starting to yellow and pods start to turn from green to yellow and then to a mature brown colour. Spots on the outside of the pods are a natural part of the maturing process.

Once the stem starts to go brown the crop is ready for harvest. Sometimes, if there are not enough pods on the plant, the stems can stay green, or if late rain falls the crop seems to hang on and just doesn't mature normally. This can only be countered by having good insect control and optimum plant population as this helps to achieve more even crop maturity.

One of the reasons for unevenness in maturity is a change of soil type or as a result of not being able to irrigate the crop evenly. Soybean crops are a great indicator of a change of soil type or soil moisture issues as they've been growing. Any areas that are stressed early on in the season tend to mature earlier than less stressed areas. The decision to desiccate and harvest needs to be based on the status of the majority of the block and that sometimes means losing small areas that mature too early. The aim is to get the majority of the block and the majority of the grain.

Soybean seed pods can shatter once they are fully mature, especially the variety Asgrow A6785. Shattering doesn't happen immediately that pods mature, it can take takes another two or three weeks before mature pods shatter. a Repeated rainfall events or physical impact by the harvester front can increase pod shattering and grain loss.

In coastal environments it is often necessary to harvest before the grain has  reach optimal moisture content. In drier inland production environments, soybean crops are often left in the paddock to until the seeds have dried down to 12 per cent moisture, but waiting for that to happen on the coast is very risky due to adverse weather. It is better to harvest at a higher moisture level and aerate the grain. .

There's normally a drying cost associated with meeting the standard of 12 percent moisture for the majority of the market places. Coastal soybean grain is often delivered at 13-14 per cent especially in the late April and early May periods where, relative to inland areas, coastal humidity is still high. The drying cost varies but is generally around $20–25/t and should be included in the budget.

It is very easy to lose some grain by waiting for the whole crop to be dryto 12% and, more importantly, in the situation where there is limited availability of harvest equipment, waiting for a crop to reach 12% may mean that another grower isn't able to harvest their crop because all the pods have shattered and the grain is on the ground. The Grain in Cane Cooperative in Queensland shares the cost and risk of grain moisture across all growers. Some crops may incur no drying costs while others need drying but everyone pays an average drying cost.

When to desiccate and arrange for the harvester

Desiccation is used to dry out the whole crop to assist in getting the best quality grain in the harvester and to market.

This key decision is hard to make. It needs to take into consideration the crop maturity and the desiccant chosen. Many coastal soybean crops will need to be desiccated to make it easier for the harvester to operate. Desiccation causesgreen weeds to drop their leaves and the stems become brittle. Having less green material going through the harvester reduces the risk of seed staining that can downgrade soybean quality.

Note that only diquat and glyphosate are currently registered for pre-harvest desiccation in soybean.

Notes from the label:

• Diquat (e.g. Reglone®) Pre-harvest crop desiccation (all states): Spray as soon as the crop has reached full maturity. Helps overcome slow and uneven ripening and weed problems at harvest. WHP: DO NOT harvest for 4 days after application.

• Glyphosate (e.g. Roundup®UltraMAXnote that not all glyphosate formulations are registered for this use) Soybean - Apply only after seed pods have lost all green colour and 80-90% of leaves have dropped. DO NOT harvest within 7 days of application. Speed of crop desiccation isdependent on crop stage, growing conditions and weather conditions during and after application. Application to crops intended for seed production or for sprouting may reduce germination percentage to commercially unacceptable levels.  WHP: DO NOT harvest within 7 days of application. 

Experience in coastal production areas suggests that when using glyphosate to desiccate the crop and kill any weeds, results are improved by waiting until at least 90 percent of the pods are yellow before spraying because any seeds in green pods will stay green. Receival standards specify alimit to the amount of green seed that will be accepted.. Allow at least 7 days WHP before harvest and check the label for specific instructions for soybean.

If using diquat (e.g. Reglone®), wait for at least four days before harvesting (as that's the withholding period), and generally harvesting four to six days after spraying is ideal.

Depending on prevailing conditions the crop may be ready to harvest as soon as the withholding period has been reached.

Other resources – GRDC Pre-harvest herbicide fact sheet

5. Types of harvesters and their maintenance

Types of grain harvester in Australia

The majority of new combine harvesters in Australia are fully imported, particularly from the United States of America (USA) and Europe.

The two major types of combine harvesters used in Australia are the rotary type (Figure 1) and the walker- or drum-type (Figure 2), with the rotary style dominating the current market. 

The modern draper-type fronts with floating cutter bars have improved grain harvest capacity and performance. It is estimated that the floating cutter bar and pickup reel can outperform the fixed/rigid platform and bat reel of older style harvesters by up to 50% (G. Quick, pers. comm.). By necessity a fixed platform will pitch and roll with the harvester as it traverses uneven ground. Maintaining a low and even cutting height is almost impossible with wide fixed platforms. Auto height controllers can be fitted to fixed or floating cutter bars. Rock barriers can also be fitted behind the cutter bar.

Harvester maintenance

A timely maintenance check may save many lost hours or days at harvest time. There are many useful ‘how-to’ videos on combine harvester maintenance, particularly those from experienced operators and service technicians in Canada, the USA and Europe. Many of the principles of combine harvester maintenance are relevant irrespective of the brand or model used in the maintenance video examples provided below.

This is a comprehensive front-to-back maintenance walk-through of a John Deere S-Series combine with Craig Windsor from Huron Tractor, Canada. This video has excellent internal views, close-up photographs and diagrams of critical working parts inside the combine harvester (feeding, threshing, separating, cleaning, and crop residue management) as well as general maintenance advice (16.11 minutes).

Greenmark Equipment in Michigan and Indiana, USA specialise in grain harvester servicing, run harvester summits and produce freely available videos. These short videos by Greenmark service technician Eric Yonker cover:

1. maintenance for grain and draper/flexi header fronts including critical points to check and common areas for wear. (4.48 minutes) 

2. and, belt maintenance, tension settings and reel settings for single and dual belt draper/flexi header fronts (8.00 minutes) 

These videos from Greenmark Equipment, service technician Keith Koetz and product specialist John Crumbaugh cover:

1. maintenance of the feeder house of a rotor combine, with a focus on grain quality (4.22 minutes) 

2. and maintenance of the grain separation elements of the chaffer, sheave and cleaning fan with a focus on the effect of windspeed variations on grain separation from chaff and power shut down to check performance (4.06 minutes)

In these three videos from Greenmark Equipment, service technician Kevin Wandless focuses on maintenance of a rotor combine harvester with reference to maize and soybean harvesting and the common wear points and areas of damage with excellent views inside the machine and advice on servicing and settings:

1. Threshing elements (5.52 minutes) 

2. Grain elevator and handling areas (6.20 minutes) 

3. Cleaning shoe, chaffer, chopper knives and chaff release areas (2.13 minutes) 

For walker-type combine harvesters Greenmark Equipment also produce a series of maintenance videos, for example, these videos with technicians Qort Schmicker and Rodney Teadt focus on: 

1. cleaning shoe and grain handling maintenance (26.55 minutes) 

2. and feeding and threshing maintenance (15.05 minutes) 

Maintenance checklist 

Set-up for soybean harvest

It is strongly advised that growers follow the set-up and safety recommendations of the manufacturer for their particular model of combine harvester. Do not assume that resellers understand all of the settings necessary to harvest soybean crops or that a new machine has been correctly calibrated for your crop or your situation. The crop and the situation vary each season, therefore, harvester settings frequently need adjusting.

Leading manufacturers of grain harvesters have developed a vast number of resources that are freely available on the internet. Well-made videos by experienced operators and service technicians are particularly useful to watch when considering harvester set-up and calibration. Some examples are provided below. 

In Australia, the Grains Research and Development Corporation (GRDC) have invested in harvester set-up workshops for Australian grain growers (e.g. project PRS2002-001SAX). Most of the examples used are of harvesting cereal or canola crops in southern or western Australia, however, the principles of measuring and minimising losses and knowing what controls to modify to improve harvesting performance apply to all crops. A series of videos of eight harvester forums are available on the GRDC website and are listed here:

Two examples of videos from the USA with specific focus on harvesting soybean crops are listed here:

1. Marion Calmer’s combine settings for a successful soybean harvest. The principles are applicable to John Deere, Case IH, New Holland, Fendt and other brands. (13.26 minutes) 

2. Case IH platform header front calibrations for soybean harvest in northern USA (9.42 min) 

6. Harvest losses

Soybean grain losses are broadly categorised as pre-harvest (in-crop), gathering (at the front of the harvester) or processing (inside the harvester, which is visible as grain lost from the back of the harvester with the chaff or crop residues). When commencing harvest and at times during harvest, it is recommended to check and measure the three categories of grain loss (Figure 3). 

The proportion of grain lost from each of the three categories is estimated in Figure 4. As gathering losses can account for up to 85% of lost grain (G. Quick, pers. comm.) it is advisable to focus on measuring and rectifying these losses.

Pre-harvest (in-crop) losses

Grain losses can occur before harvest and can be due to many factors including:

• incorrect choice of variety for the location or planting time (varieties from the Australian Soybean Breeding Program have been bred and selected for high tolerance to shattering in Australian conditions),

• physical crop damage due to spraying operations, uncontrolled traffic in the crop, or storms and other extreme weather,

• pod-sucking bugs (e.g. green vegetable bug and Riptortus) compromising the integrity of the pod wall through stinging and feeding on pods during the season, which then allows moisture, fungi and bacteria to enter the pod and degrade the seed,

• delayed harvest leading to the mature pods experiencing a series of wetting and drying cycles, which can cause weathering and shattering of the pods and mould to develop on the grain,

• pod damage including chewing by crickets, birds, mice or other animals.

Gathering (front) losses

This category accounts for the greatest proportion (~85%) of grain lost from a crop and many factors are implicated. Making only one adjustment at a time gives the operator a better idea of where performance can be improved. Many factors should be considered and investigated including: 

• shattering losses causing grain to fall out of the pod (and onto the ground) as the header front, reel and knives make contact with the plant; reducing the movement of the plant at this point reduces shattering,

• header front type, for example, fronts with fixed or rigid platforms are less able to adjust to variable ground or crop height and can leave unharvested pods in the field or cut stems with pods attached that are not fed into the harvester,

• incorrect setup and calibration resulting in the cutter bar not reaching below the lowest pods or some branches with pods slipping under the cutter bar,

• inability for the front to adjust to uneven or rocky ground,

• variable-width platforms may assist in harvesting short crops by minimising the ‘dead zone’ where the reel tines sweep over the platform and lift just ahead of the auger,

• broken or blunt knives cause the plants not to be cut correctly or cleanly and plants with pods may remain standing in the field after the harvester has passed,

• addition of knife guards or air reels may reduce losses by improving cutting and feeding of the crop into the harvester,

• type of knives used, for example, a narrow-pitched knife (e.g. Kwik-Cut or Tiger Jaws) may reduce front loss in soybean compared with the traditional 3 inch (75 mm) sickle sections and 3 inch guards. This is mainly due to causing less stem movement during cutting,

• type of reel used, for example, the ‘feathering’ pickup style of reel is preferred for harvesting soybean crops as the reel tines (or fingers) enter the crop vertically for least disturbance and gently sweep the crop over the cutter bar and into the auger. A bat style reel may be less expensive to buy but is likely to shatter the mature pods, especially in very dry crops (MC<10%),

• reel index (ratio of reel tip speed to forward speed) should be maintained around 1.25, which means that reel speed needs to be changed when the combine speed changes. Auto reel speed control can be fitted to the combine harvester,

• reel position and tine pitch need to match to crop conditions. Ideally, the reel tine pitch needs to be near vertical, otherwise the teeth may become tilted back towards the cutter bar if the crop is lodged,

• travel speed is a common cause of lost grain due to either overloading the combine harvester by travelling too fast or not adjusting speed to match the condition of the crop so that it feeds evenly into the harvester,

• low pod set can occur in the crop due to colder seasonal conditions producing shorter plants or lower bottom pod height, lower than recommended plant population or incorrect choice of variety for the location and planting time.

Processor (back) losses

Processor performance is best with smooth/even crop feeding into the harvester. Mature, dry soybean crops are comparatively easy to thresh and separate but remember that soybean grain has a thin seed coat and is susceptible to splitting and other damage. 

Australian Soybean Breeding Program varieties (e.g. Hayman, Richmond, Gwydir, New Bunya, Kuranda, Burrinjuck and Moonbi) have been specifically selected for even crop maturity and seed size, whole-plant dry down and clean leaf drop. 

Crops with green stems (and ripe pods) may result in heavy slugging and ‘roping’ in the harvester processor. In a high yielding crop that has green stems and green weeds present, ‘lumpy’/uneven feeding of the crop into the harvester and less-efficient threshing occurs. A draper-type head provides smoother flow and more crop feeding into the processor as it takes a ‘heads-first’ approach.

The processor shells the grain from the pods and should do that without causing excessive damage and splits. The cleaning system should remove weed seeds and foreign matter from the bin sample. 

By using the appropriate processor (rotor or cylinder) speed and settings, the operator must strike a balance between achieving a complete thresh and gentle threshing to maintain grain quality and reduce split grain. Thresher speed, for example, should be slowed to the point where damage and splits are acceptable but still maintaining acceptable threshing losses (i.e. very few intact pods in the sample). Monitoring the tailings return to check whether it is grain-rich or chaff-rich is one gauge of thresher performance. 

Operate to maintain a cushion of crop in the processor for least damage to soybean grain. When unloading, slow the engine to reduce seed damage by the unloading auger. Where possible, use belt conveyors and avoid augers when moving soybean grain.

Grain losses can occur during the many processing steps inside a combine harvester and can be influenced by a range of factors including:

• travel speed is too fast or too slow for even feeding and optimal threshing of the crop, 

• rotor clearances,

• rotor or cylinder speed too high causing grain damage. For soybean harvesting, the rotor or cylinder is recommended to be running at a peripheral speed of around 18 m/s (3500 ft/min). For a 30 inch (750 mm) rotor diameter, as on a John Deere STS or Case IH 9020, that equates to a rotational speed of around 450 rpm,

• fan speed,

• loose grain elevator chains,

• incorrect sieve settings for the grain size or broken/blocked sieve components,

• losses from the shoe (or bottom) sieve can be caused by operating too slowly or variably. Consistent engine and fan speed helps to minimise losses from the shoe sieve. Inspecting the tailings return flow gives an indication whether this part of the process is working optimally (Figure 5). To minimise losses from the cleaning shoe, remove any perforated screens under the elevator doors, cross augers or under the unloading auger tube. Open the chaffer (upper sieve) wide enough (e.g. 5/8 inch or 16 mm) to prevent clean soybean grain being carried onto the returns system, likewise, the lower sieve should be set initially at 3/8 inch or 9 mm.

Measuring losses

In 2021 and 2022, the Grains Research and Development Corporation (GRDC) invested in a collaborative project with the WA Grower Group Alliance to measure grain harvest losses in West Australia for wheat, barley, lupin, canola, oat, lentil, field pea, faba bean and chickpea. The study included seven brands of harvester and five different styles of header front. 

A summary of the findings from study is available here: https://www.gga.org.au/activity/measuring-harvester-losses-in-western-australia/ 

Early in the harvest and periodically throughout harvest, checking for lost soybean grain on the ground behind the harvester or using a pan to measure grain losses during harvest is essential. Loss monitors only measure relative loss and need periodic calibration. They indicate relative performance well, but a harvester operator must periodically assess (count) grain losses on the ground.

A useful factsheet on calculating harvest losses is available here:

A GRDC workshop specifically focussed on understanding and measuring grain losses at harvest is presented by Peter Broley (Primary Sales Australia), Ben White (Kondinin Group), and Kassie van der Westhuizen (harvesting specialist) below (20.44 minutes).

Use several sampling frames randomly placed in a uniform part of the crop and behind the machine. Get down on the ground and count soybean grains inside the frame(s). In simplest terms, four beans in a frame on the ground in 1/10th m² (say 32 cm x 32 cm) frame area represents 76 kg/ha loss.