Diagnosing poor quality seed in narrow-leafed lupins
Lupin has large seeds that are prone to mechanical damage during harvesting and subsequent handling, which may reduce seed viability. Other factors such as wet weather prior to harvest, effect of chemicals and the age of seeds can also affect viability.
What to look for
- Reduced germination and/or weak seedlings that are usually uniformly mixed with normal seedlings in a paddock.
- Seeds swell but fail to germinate properly.
- Seeds germinate but seedlings are malformed or too weak to reach the surface.
- Broken and deformed roots, cotyledons, hypocotyl or growing point on emerged plants.
What else could it be
|Diagnosing seedbed constraints in narrow-leafed lupins and field peas||Reduced and staggered germination||The problem is more likely to vary between rows, and with changes in soil or landscape position.|
|Diagnosing water repellence||Reduced and staggered germination||The problem is more likely to vary between rows, and with changes in soil type.|
|Diagnosing allelopathy in narrow-leafed lupins||Reduced and staggered germination. Malformed seedlings||Allellopathic affected plants remain pale, distorted and stunted and may be caused by toxins leaching into the seedbed or from contaminated seed.|
|Diagnosing waterlogging in narrow-leafed lupins and field peas||Reduced and staggered germination||Waterlogged and saline areas are often clearly defined, and the problem is ongoing.|
Where did it come from?
Several factors can reduce seed viability:
- Legumes are more prone to mechanical damage than cereals, becoming more susceptible with increasing seed size.
- Wetting then drying of mature lupin crops causes small cracks in the seed coat that makes them even more susceptible to mechanical damage.
- Legume seed viability declines more rapidly than cereals.
- Viability of lupin seed harvested with 15 per cent moisture or above declines rapidly in unaerated silos.
- Lupin seed stored with green wild radish residues causes allelopathy.
- Native budworm and lucerne seed web moth burrow into lupin pods to eat the seed.
- Premature maturity from causes such as drought, bean yellow mosaic virus, herbicide damage and other factors cause shrivelled and smaller seed. Plants grown from this seed is has less early vigour and stress resistance.
- Seed borne diseases such as anthracnose, phomopsis and cucumber mosaic virus.
- Manganese deficiency causes split seed, and apparently undamaged seed with less than 13mg/kg manganese can have lower germination and vigour.
- Seed with less than 0.25 per cent phosphorus will produce small seedlings that will not cope with stresses during early growth.
- Submit a representative sample of each seed lot for testing as soon as possible after harvest. Samples can be taken from the seed stream as seed is being transferred to a silo.
- Good quality seed should be rested after 2 years.
- Ensure that the moisture content of lupin to be stored and sown next year is no greater than 13 per cent.
- Minimise the handling of lupin seed as much as possible.
- Screw augers are the most damaging. To reduce the damage, slow down the auger and make sure it runs full. Augers should also be as short as possible and used at the lowest possible angle. Avoid worn augers, and augers with a diameter smaller than 125 mm.
- Check that airseeder air pressure is no greater than the minimum needed to ensure reliable operation.
- Harvest future seed from paddocks with adequate manganese and phosphorus.