The effects of time of planting on irrigated sunflower were tested at Emerald during the 1969-70 and 1970-71 summer seasons. Plantings ranged from September to March. A growing degree day summation from a base of 0�C (GDDo) was the most reliable index of commencement of flowering (cv. 5.7 per cent). Sunfola commenced flowering at 1331 � 76 GDDo. In both seasons significantly higher seed and oil yields were obtained from a December planting (Seed yields 2628 kg ha-1 1969-70, 1808 kg ha-1 1970-71, oil yields 1025 kg ha-1 1969-70, 61 5 kg ha-1 1970-71). Lower yields at all times of planting in the second season were attributed to rust infection (Puccinia helianthi Schw) . A good correlation was obtained between oil quality (proportions of oleic and linoleic acids) and temperatures during the post flowering period. Oleic acid levels ranged from 12 to 48 per cent. Linoleic acid levels ranged from 39 to 73 per cent. Oil quality (per cent linoleic acid) improved with late sowing in association with lowered temperatures

Four irrigation frequencies and six nitrogen (N) fertilizer rates (0-300 kg ha-1) were applied to cotton (Gossypium hirsutum L.) grown on three Vertisols in the Emerald Irrigation Area, central Queensland. The purpose was to describe lint production responses to the plant available water before irrigation and N fertilizer, in terms of the crop N content and the efficiency of crop N use for lint production. Lint yield was greatest when the plant available water before irrigation was 50-80010 of the plant available water capacity (PAWC) of each soil. The rate of N fertilizer for maximum yield varied with plant available water and soil type. Plant available water before irrigation >60% and <37% PAWC, and rain after irrigation reduced the crop N content at the time of maximum leaf area index. Relative yield generally responded to 130 kg crop N ha-', although the range from 101 to 141 kg crop N ha-1 reflected differences in the maximum yield of each treatment. If the crop N was <130 kg ha-1, yield was mostly determined by the crop N content, whereas if the crop N content was >130 kg ha-1, yield and the efficiency of crop N use for lint production was determined by the plant available water before irrigation and soil type. Nitrogen fertilizer strategies to achieve the maximum yield of cotton (var. Deltapine 61) should focus on obtaining 130 kg crop N ha-1. This crop N content produced maximum yields for a range of plant available water contents before irrigation, and for three soil types.

No abstract

The effects of time of planting on irrigated sunflower were tested at Emerald during the 1969-70 and 1970-71 summer seasons. Plantings ranged from September to March. A growing degree day summation from a base of 0�C (GDDo) was the most reliable index of commencement of flowering (cv. 5.7 per cent). Sunfola commenced flowering at 1331 � 76 GDDo. In both seasons significantly higher seed and oil yields were obtained from a December planting (Seed yields 2628 kg ha-1 1969-70, 1808 kg ha-1 1970-71, oil yields 1025 kg ha-1 1969-70, 61 5 kg ha-1 1970-71). Lower yields at all times of planting in the second season were attributed to rust infection (Puccinia helianthi Schw) . A good correlation was obtained between oil quality (proportions of oleic and linoleic acids) and temperatures during the post flowering period. Oleic acid levels ranged from 12 to 48 per cent. Linoleic acid levels ranged from 39 to 73 per cent. Oil quality (per cent linoleic acid) improved with late sowing in association with lowered temperatures