Effects of cultural technique on establishment and growth of early-sown sugar beet.

Abstract

Yield of sugar is closely related to the amount of solar radiation intercepted by the sugar beet crop. Early sowing increases leaf area and radiation interception in May and June, when radiation is at its maximum. In the past, bolting has been an undesirable consequence of early sowing, but some modern cultivars have good bolting resistance and can be sown early with a limited risk of bolting. This study in 1999-2000 was a modified continuation of work on early sowing from 1994-98. In 1999, a comparison was made between two sowing dates at Oak Park and Davidstown, Co. Wexford, using cultivars Celt and Libra, and sowing on drills or flat. In addition, the effect of inter-row cultivation on crop yield was assessed. In 2000, the effect of seed priming on establishment was measured for two sowing dates and on drills and flat at two sites with the cultivar Celt. Inter-row cultivation was assessed on a commercial crop at Oak Park only. The effect of sowing date on plant establishment was not as clear-cut as in the previous experiments, with no significant differences in 1999 and conflicting results from the two sites in 2000. There was no difference in establishment between Celt and Libra. Seed priming gave faster establishment than untreated seed, particularly at the earlier sowing, but there was no difference in the final populations. Sowing on the flat usually gave better establishment than on drills. Early sowing always produced significantly higher root yields (average difference over four sites was 6.5 t/ha) than late March/early April sowing. There was no significant difference in sugar content between sowings, but extractability was slightly higher after the early sowing. Celt gave higher root yields but lower sugar contents and extractabilities than Libra. Seed priming did not improve root yields. Inter-row cultivation had no beneficial effect on root or sugar yields. There was no significant difference in root yield or sugar content between drill and flat sowing, even when plant populations on drills were lower. There were few bolters at either site in 1999, but in 2000 there were more bolters on the early-sown treatment and on those plots sown with unprimed seed. There were more forked roots on these treatments also at Oak Park, but there was no significant difference in Wexford. The main conclusions from the experiments were: 1. early sowing increases root and extractable sugar yields consistently; 2. while primed seed gives more rapid establishment, it has little effect on yield; and 3. inter-row cultivation has no effect on yield.