They say timing is everything. According to findings from the Stored Grain Research Laboratory, that couldn't be truer for harvesting pulses and avoiding quality loss before storage.
The CSIRO research team, in collaboration with the NSW Department of Agriculture, investigated key factors determining the best harvest time and safe storage conditions for two varieties of field peas (Jupiter and Bohatyr) and three of lupins (Ultra, Kiev mutant and Merrit). The project was supported by growers through the GRDC.
Researchers assessed the effects of different harvest times upon changes in yield and seed quality, and determined the subsequent safe storage limits of temperature and moisture content.
Highest quality at 15 per cent
For machine-harvested pulses, the highest yields and seed quality were obtained when the plants were harvested fully mature, with a seed moisture content around 15 per cent.
Project leader Julie Cassells said harvesting of pulses is often delayed, as growers give reference to cereal harvesting. Consequent weathering and drying of the pod and seed result in lower yield and quality.
A trial measuring the effect of shattering on yield showed that yield loss due to shattering was least in Ultra lupins.
"Bohatyr field peas were the most vulnerable as the pod and seed gradually dried during the harvest period," said Mrs Cassells. Delays in harvesting the mature Bohatyr crop resulted in 30 per cent of the crop (1.3 t/ha) being lost to shattering.
Slow harvest = loss of quality
Generally, grain quality deterioration paralleled an increasing delay in harvesting. The extent of the quality changes varied with pulse type and variety. For the human consumption market, it often means lost dollars.
Storage temperature and moisture
Safe storage of pulses is mainly influenced by moisture content at harvest, storage temperature and period of storage (see table below). The safe moisture content limits are shown at 20° C and 27° C. Under these conditions seed maintains germination and colour, and mould growth is inhibited.
Pulse colour changed with increase in temperature, relative humidity and time in storage, said Ms Cassells. Colour degradation was more notable in field peas, especially in the green-hued Jupiter. The researchers also found 'breakability' of field peas was not related to storage but was due to the repeated wetting and drying of the seed before harvest.
Suggested safe moisture content storage limits at 20°C and 27°C for field peas and lupins. Grain moisture content given as % wet basis.