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Fate of unemerged lupin seedlings on sandplain soils of western Australia

K. McCarthy and R. Delane

Department of Agriculture, PO Box 110, Geraldton WA 6530

Lupin establishment experiments conducted in the major lupin growing areas of Western Australia have shown that, on average, 20% of all viable seeds do not establish plants (this figure may vary from 0 to 60% depending on soil type and seasonal influences). Common causes of emerged seedling failing to establish include disease, wind and insect damage, inadequate soil moisture and toxicity from fertilisers and herbicides. No information existed on the fate of seeds which fail to emerge.


Unemerged seedlings were excavated from one metre lengths of seeding row, using a hand trowel and sieve, within plots sown in late April, mid May and late May at a site with a history of poor lupin establishment. Seedlings were classified into groups shown in Table 1.

Results and discussion

Emergence increased with later sowings as the soil moisture status increased (Table 1). Results indicated that the principle causes of unemerged seedling mortality were inadequate soil moisture, particularly where the radicle of the newly germinated seed was exposed to drying soil, and disease (Rhizoctonia solani ZG 3) which attacked radicles and cotyledons. A large proportion of seedlings from sowings in late April and mid May had imbibed and germinated but had not emerged. Imbibed seeds were still viable under germination test conditions. There were no indications that poor germination, making or 'silly seed' syndrome (gravitropism/ geotropism) were significant causes of seeds not emerging.

Table 1. Effect of sowing data on the fate of unemerged seeds three weeks after sowing. Results are expressed as percentages of the total number of seedlings excavated. Figures in parentheses represents the rainfall (mm) recorded from the sowing date to the sampling date for each time of sowing.


The following assistance is acknowledged: (i) disease identification - Mr W. MacLeod; (ii) financial support - GRC (WA) and GLRD, and (iii) technical support - Ms T. I'Anson.

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