No abstract

The timing of bunch covering during the development of bananas was examined to find the optimum for fruit quality and reduction of maturity bronzing. Bunch covers, either open or sealed, were applied at various stages of bunch development. The experiments were carried out at South Johnstone, North Queensland. Sealed covers increased the severity of maturity bronzing whenever they were applied. Sealed covers applied for the period either before or after finger diameter of the third hand had reached 2.7 cm increased maturity bronzing, but not by as much as when covers remained sealed throughout bunch filling. These data indicate that sealed covers increase maturity bronzing throughout fruit growth. Maturity bronzing was slightly less when open covers were applied as the last female bract lifted on the bunch (early), compared with a week or so later when the fingers had curled up. Bunch weight was not increased by the application of open covers, but the use of sealed covers increased bunch weight by up to 9%. This was due to increased finger length along the entire bunch. The application of covers (both open and sealed) at earlier than conventional times increased finger length at the proximal end of the bunch, the effect being greater the earlier covers were applied. Open covers reduced the time taken from bunch emergence to harvest by 5-11 days compared with no covering. Very early and early covering gave the largest reductions. Sealed bunch covers delayed harvest by up to 16 days compared with no covering. There was a non-significant reduction of 2-4 days in fruit greenlife, related to the delay in bunch filling caused by sealed covers. Sealed covers led to some fruit abnormalities, including severe spotting by Deightoniella sp., slightly s-shaped fruit, and dull fruit appearance. Early application of open bunch covers is recommended to reduce maturity bronzing. This treatment also increases finger length, and bunch filling time is reduced by about 1.5 weeks. This effect suggests sensitivity to the environment during and soon after bunch emergence.

Bananas cv. Williams were grown at a range of plant densities (1 157-2825 plants ha-1) in single and double rows in North Queensland for 3 crop cycles to determine the best spacing in double rows and to compare yield and plant characteristics of different planting systems. Yield increased with increasing density in each crop cycle (from 16 to 2 1 t/ 1000 plants over the range tested). The duration of the crop cycle was unaffected by density in the plant crop. In the ratoons, the length of the crop cycles increased with increasing density (from 9 to 12 months in ratoon 1 and from 10 to 12 months in ratoon 2). Thus productivity (t ha-1 year-1) averaged over the 3 crop cycles only increased by 10 t/ 1000 plants over the range tested. Single rows had taller following suckers than did double rows at harvest of the plant crop (average of 207 v. 177 cm). Together with the shorter pseudostem height at which single rows bunched, this led to more rapid cycling than at similar densities in double rows in ratoon 1 (9 v.11 months). In double rows, spacings of 1.5 m between the 2 rows of the double row and 1.5-1.8 m between plants in the row made for considerably easier selection of followers than did closer spacings.

No abstract

The effects of nitrogen (N) and potassium (K) on coffee (Coffea arabica L.) growth and yield in a shallow sandy soil in North Queensland were studied over 5 years following field establishment. High rates of N (416 and 624 kg/ha) applied frequently were necessary for rapid growth and yield of cvv. Kairi Typica (K2), Caturra Rojo (CR33), Catuai Rojo (CR35), and Bourbon Red (B61). Although data were not significant, mean yields with 416 and 624 kg N/ha were greater than with 208 kg/ha by 124 and 145% in 1986, by 12 and 26% in 1987, and by 38 and 31% in 1988. Increasing rates of K (63, 126 and 189 kg K/ha) did not affect growth and did not significantly increase yield in the later stages of the experiment. Neither N nor K had any affect on green bean size or time of berry maturity. CR35 was the highest yielding cultivar (3752 kg/ha of green bean in 4 years of cropping) and B61 the lowest (2067 kg/ha). Height and girth were ranked K2 > CR35 > CR33 > B61. B61 also had significantly fewer and shorter longest primary laterals. CR35 ripened later than other cultivars, while B61 produced the highest percentage of large beans, and K2 the highest percentage of small beans. Preliminary recommendations for coffee growers in this region are 100 kg N/ha in year 1, increasing to 400 kg/ha in year 4; and 80 kg K/ha in year 1, increasing to 320 kg K/ha in year 4. Monthly, rather than quarterly, applications are recommended.