Studies on the field establishment of Russell lupin (Lupinus polyphyllus x Lupinus arboreus).

Abstract

Three field experiments in 1988 and 1989 evaluated the agronomic factors affecting the emergence and establishment of Russell lupin (Lupinus polyphyllus X L. arboreus). The first experiment in 1988 looked at the combined effects of sowing depth and sward treatment, while the second examined the effect of seed scarification on emergence and establishment. The third experiment in 1989 produced data for a predictive model of establishment based on thermal time.

Herbage mass present had no effect on the total cumulative emergence, while the highest emergence of 45% was found from live and burnt herbage treatments. Depth of sowing had a highly significant effect on percent emergence with 55% emergence from 2 cm deep sowings. Surface, 1 cm and 3 cm deep sowings had emergences of 35%, 50% and 40% respectively.

The best establishment of 37% occurred under dead vegetation, while burnt and live vegetation had establishments of 35 and 26% respectively. Establishment was highest at the 2 cm depth with 40%.

The DM production at 45 DAS under herbage treatments were significantly higher from plants under dead and burnt herbage at 596 mg and 352 mg/plant respectively. The plants under live herbage produced only 65 mg/plant. At 45 DAS sowing depth had no effect on mean wt/plant at 338 mg/plant.

Mechanical scarification gave the highest cumulative emergence. However, until 13 days after sowing there was no significant difference in emergence between acid and mechanical scarification. By 18 days after sowing mechanical scarification gave the highest cumulative emergence of 81%.

A high proportion of abnormal seedlings were produced in all the treatments at 24 DAS. Acid scarification and mechanical scarification produced 53% and 51% abnormal seedlings respectively. Unscarified seed produced 45% abnormal seedling with the highest proportion (55%) of normal seedlings.

At 24 DAS, the DM production from normal plants was 65 and 51 mg/plant from acid and mechanically scarified seed respectively. Control plants from unscarified seed produced 31 mg/plant. The seed treatment had no effect on the DM production of abnormal seedlings. However, at 43 DAS, when DM production was analysed irrespective of normality or abnormality, mechanical and acid scarification produced plants with significantly higher DM (500 mg and 440 mg/plant respectively) than did the untreated seed (320 mg/plant).

The third experiment showed that as the mean temperature decreased the number of days to emergence and establishment increased. There was a significant linear relationship between duration rate to both emergence and establishment and mean temperature. The best fit was exhibited by the rate of emergence and establishment and the mean temperature derived from the meteorological data with an R² value of 80% (P=0.01) and 97.5% (P<0.01) respectively. The figures suggested base temperatures of 2°C for emergence and 3°C for establishment.

The number of degree days to emergence remained approximately constant at 190°C days while for establishment it was about 412°C days. A computer simulation model incorporating these required thermal days to emergence and establishment was produced. The relationship between actual days from sowing to emergence and establishment and predicted days from sowing to emergence and establishment was linear with an R² of 96% (p<0.01).

The model was used to predict emergence and establishment for four sowing dates over a six year period (1984-1989). Cool seasons delayed while warmer seasons enhanced emergence and establishment.