When grain enters storage it needs monitoring, just as a crop does throughout the growing season.
Regular monitoring means problems are detected early and can be managed before significant grain damage occurs. It also avoids surprises at out-loading, prevents costly rejections from grain buyers and maintains your reputation for supplying quality grain.
- Regular monitoring allows early action to be taken if insects or grain quality issues arise.
- Failure to monitor grain not only increases the risk of damage and loss but can delay delivery if an issue is first identified at out-loading.
- Monitor grain temperature and moisture content and check for insect pests.
- Testing grain retained for seed after harvest helps plan for the following season.
Monitoring starts at harvest — knowing grain condition and grade as it comes off the paddock determines the appropriate storage conditions.
- High-moisture grain requires drying or blending.
- Warm grain requires cooling.
- Variable quality grain will benefit from segregation.
When the grade is known (test at a registered receival site) ask what parameter(s) it’s close to for being downgraded or upgraded. It may be something that can be tested for and managed on farm, such as protein, screenings or test weight.
Having this information on hand at harvest can support segregating grain as it comes off helping it to stay within the grade. Alternatively, blending grain from lower-grade areas of the paddock with that from higher grade areas may improve the overall grade.
In some cases, insect pests can come from machinery, so check grain on the way into storage so it can be treated or fumigated. Note: contact pesticides are not an option in Western Australia.
When in storage, grain is vulnerable to quality loss. Poor management can see grain come out of storage in an unsaleable condition. Monitor grain so problems can be addressed early before they cause significant damage. Dealing with an issue earlier rather than later is easier and more cost effective.
Check stored grain at least once a month during the cooler months and fortnightly during warmer months. Collect samples from the bottom of storage and, if safe, at the top.
In warm conditions (>30ºC) many grain pests can complete their life cycle in as little as 3–4 weeks causing significant damage.
When monitoring stored grain check:
- For insect pests
- Grain temperature
- Grain moisture content
- Grain quality and germination
Sampling stored grain
Collect samples from the areas where insects and mould are most likely to establish first. These areas are generally around openings — hatches, doors, aeration fan inlets, filling and emptying points.
The most common place for insects and mould in a silo is at the top, just below the surface of the peak of grain (see Figure 1). This is because it’s the last place aeration cooling or drying reaches, it’s exposed to the sun heating the headspace, condensation from the headspace and provides easy access for insects through the top lid, inspection hole or vents.
Always follow occupational health and safety guidelines and only climb to the top of a storage if it’s safe to do so.
Always collect samples from beneath the grain surface. At the bottom of a silo this means opening an outlet to run a small amount of grain out. A sampling probe is ideal for collecting grain from the top of a silo, but it’s often impractical or unsafe to climb up a silo with a sampling probe.
Checking for insects
Grain pests can be difficult to find because they are small, fast moving and some prefer the dark while others can be seen on the surface. There are numerous ways to detect them.
Tie the trap to something inside the storage so it doesn’t get lost or forgotten about before out-loading. Position the trap so a small amount is protruding out the top of the grain to capture insects crawling across the surface as well as those hiding beneath.
Monitoring grain temperature is not only required to manage aeration, it can indicate potential mould or insect activity in the grain stack.
Insect activity generates heat, which provides favourable conditions for mould. When checking grain temperature, go beneath the surface, measuring in the same spot each time. Record test results to identify any temperature spikes, which will prompt further investigation.
Grain moisture content influences mould and insect activity (see Figure 2). Identifying a change in moisture can reveal an issue before it causes significant damage. For example, an increase in grain moisture at the top of a storage could be a result of a leak, condensation or problem with aeration management.
Seed germination and vigour
Storing grain at the optimum temperature and moisture content as shown in Figure 2 not only reduces the risk of mould and insects, it maintains grain quality and germination.
CSIRO research reveals how moisture content and temperature affect the rate at which seed germination declines. A trial was carried out with premium quality wheat at 12 per cent moisture content and an initial seed viability of 100 per cent, stored for 150 days.
Storing at 20°C decreased the seed viability by only 1 per cent but storing at 30°C decreased viability by 21 per cent over the 150 days. Reduced germination rates result from a breakdown of grain cellular structure and function, with related changes in chemical composition and modification to enzyme and other bio-chemical systems.
Stored grain deteriorates with time under any conditions, but poor storage conditions (high grain temperature and moisture) accelerate the deterioration process markedly.
Testing germination rates on retained seed
If retaining grain for seed, a germination test and seed count test performed a month after harvest can help guide how much seed needs to be kept to achieve acceptable paddock plant populations.
If the germination test at this stage is poor, it might pay to buy in seed. If germination is satisfactory, use that to guide how much extra seed to keep, adding an allowance for all the other factors that will reduce germination and seed establishment.
Factors influencing how much seed needs to be retained for sowing include:
- Germination rate tested at harvest.
- Further decline in germination between harvest and sowing.
- Screenings, foreign and small seeds lost at cleaning.
- Allowance for seeds that germinate but don’t emerge.
- Seed weight (grams per 1000 seeds).
- Buffer to allow for change of plans in planting area.
Before sowing, carry out another germination test to check for decline in germination rates during storage.
CSIRO research shows this decline can be around 21 per cent if grain is not stored in ideal conditions. A decline of more than 10 per cent in germination rate from harvest to sowing should prompt action to improve the storage conditions or management in future years.
Grain temperature has one of the largest influences on seed germination and vigor. Monitor temperature regularly and ensure sound aeration management.