Temperature effects on the early field development of cotton

Abstract

The germination and early development of cotton in the Namoi Valley, New South Wales, was examined in three seasons, and related to temperature by regression analysis and by growing degree day (GDD) summations. Temperature variation was achieved by planting date and season. It was found that cotton development between planting and squaring would cease below 11.4°C. A delay of one week in planting decreased the planting to emergence phase by 0.9 days, the emergence to squaring phase by 2.2 days and the squaring to flowering phase by 0.4 days. Therefore, the selection of cultivars for cold tolerance should concentrate on the emergence to squaring phase in particular. For wet soil, increasing temperature was strongly associated with per cent and speed of emergence. For dry soil, temperature had a smaller effect.