Sowing-date responses of early maturing indeterminate soybean genotypes in northern New South Wales

Abstract

The development of new cultivars has provided impetus for soybean (Glycine max) production in northern New South Wales to expand into dryland cropping areas. These new cultivars differ from the traditional irrigated types by being indeterminate and maturing 3-4 weeks earlier. There is no information on the response of this type of cultivar to agronomic factors such as sowing date. However, knowledge of the response to sowing date is of particular importance as it allows producers to decide whether or not to take advantage of good seedbed moisture outside the most favoured range for sowing date. This study utilised irrigated conditions to examine the phenological and yield potential responses to sowing date of 6 early maturing genotypes, including the recently released cultivars. For sowing dates from early November to December the phenological responses were minor and unlikely to influence sowing date decisions, but yield responses varied among genotypes. The recently released cultivars Farrer and Valder showed similar yielding ability across sowing dates from early November to early December. However, the other 4 genotypes (Williams, Calland, Bill 55, Witch 101) showed a marked yield depression with early sowings. Thus choice of cultivar is important when deciding on sowing dates, and tests of sowing date response are necessary for cultivars released for dryland production in the future.