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Seeding date and rate of conventional and semi-leafless field peas

E.L. Armstrong and S.G. Fisher

Agricultural Research Station, Cowra , N.S.W., 2794

The Introduction of semi-leafless field peas with a more determinant and dwarf growth habit heralds a significant change from the traditional types currently cultivated in Australia. Therefore, agronomic practices such as seeding date and density need re-evaluation.

A series of experiments commenced at the Agricultural Research Station, Cowra, N.S.W. in 1987 with these objectives in mind.

Methods

Three genotypes (Dundale, Wirrega and Dinkum) were sown at 3 dates (30 April, 25 May and 3 July) and at 4 seeding rates (aiming at 15, 30, 45 and 60 plants/square metre). A split plot design was used with sowing time as the main blocks. Plots were 14 metres by 6 rows (18 cm spacings), and were replicated 3 times. Rainfall during the growing season (May to October) was 332 mm, slightly above the long term average (307 mm). The trial was located on an acidic grey loam derived from granite with a pH (CaCl2) of 4.8. Rhizobium was applied at sowing using water injection.

Results and discussion

Dinkum (PSA 6), a semi-leafless, semi-dwarf type, responded similarly to conventional types with respect to seeding date - yield was highest at the

25 May sowing (see figures). Sowing earlier than this resulted in taller plants with a greater number of reproductive nodes. However, disease and extensive lodging prevented many of these from setting, and grain yields were lower. Sowing later did result in less disease, but reproductive node number and seed yields were severely reduced as a consequence of the shortened growing season.

When sown on 25th May, the yield of Dinkum increased with increasing density, but this was not significant after 45 plants/square metre (see figures). Optimum plant densities for Dundale and Wirrega were around 35 and 45 plants/square metre, respectively. These results suggest that only minor density increases are necessary for the cultivation of semi-dwarf, semi-leafless types in this environment. Their ability to produce basal branches can compensate for their reduced indeterminancy.

Figures 1,2 and 3. The effect of changing plant density and sowing date on seed yield of conventional (Dundale and Wirrega) and dwarf, semi-leafless (Dinkum) pea genotypes.

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