Effect of sowing date on plant count, true-leaf growth stage and vernalisation of fodder beet and sugar beet

Abstract

The effect of date of sowing on plant population, true - leaf growth stage, and vernalisation impact was investigated in a trial in 2015 in Canterbury. Fodder beet and sugar beet (Beta vulgaris) were sown at six different sowing dates (mid-and late-September, mid-and late-October and mid-and late-November) at rate of 100,000 and 110,000 seeds/ha, respectively. Higher plant populations were found in late-November sowing for fodder beet in comparison to the earliest sowing (81,000 versus 45,000 plants/ha). A median true-leaf growth stage eight on fodder beet plants was reached faster at the late-October (45.5 days), mid-November (44 days) and late-November (43.5 days) sowings, compared with the earlier sowings (mid-September: 58.5 days; late-September: 56.2 days; and mid-October: 52 days). For sugar beet plants, a true-leaf growth stage eight was reached faster in late-November and late-October than plants from mid-September, late-September, mid-October and mid-November sowings. Thermal time to reach the median true-leaf growth stage eight was calculated for each cultivar at each sowing date, and differed between both sowing date and cultivar. The highest and the lowest thermal time calculated for the true-leaf growth stage eight was in late-November (520°C for fodder beet and 497°C for sugar beet) and late-October (456°C for fodder beet and 409°C for sugar beet), respectively. The impact of the lower temperature in the early sowing had a greater impact on vernalisation on the fodder beet crop with a calculated number of 83 bolters/ha. These results indicate clear differences between date of sowing for plant populations and time to true-leaf growth stage achievement, and between cultivars the differences in vernalisation demonstrates the genetic selection of cultivars can substantially reduce this occurring with earlier sowings dates.