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.

Wiltshire Horn-Merino (WH-M) crosses of 1/2, 5/8 and 3/4 Merino content were compared over 10 years for wool shedding, blowfly strike frequency and wool production traits. Merinos and 1/2 Merino WH-M were compared over 4 years. For wool production traits, 1/2 and 5/8 Merino WH-M ewes were compared to Border Leicester-Merino (BL-M) ewes over 2 years. Shedding increased with age for all WH-M genotypes, with 3/4 Merinos showing less shedding than 1/2 Merinos at all ages. At 1 and 2 years of age, 5/8 Merinos were intermediate between the other 2 WH-M genotypes, but at later ages they were similar to 1/2 Merinos. All genotypes showed less shedding at the belly site than the head, neck and breech as lambs, but not at older ages. Phenotypic correlations between sites on the same sheep were high, averaging 0.85. Repeatability estimates for each site ranged from 0.26 to 0.45. Shedding increased most with age in the 1/2 Merinos, and least in the 3/4 Merinos. Little or no shoulder and back wool was shed by most sheep. All 1/2 and 5/8 Merinos and most 3/4 Merinos had bare legs and points. Blowfly strike incidence was far higher in Merinos than 1/2 Merinos, in all years. Among WH-M, blowfly strike incidence increased as Merino content increased, in all years. All WH-M were far inferior to both Merinos and BL-M in total greasy wool weight and all its components, and also in clean fleece weight, with their level of inferiority increasing as their Merino content declined. Wool fibre diameter for all WH-M was coarser than for Merinos, but was a little finer than for BL-M. Fibre diameter increased in the WH-M as their Merino content declined. All WH-M had lower wool yields than the Merinos or BL-M. In some years the 314 Merinos had lower wool yields than the 1/2 and 5/8 Merinos, which were similar in all years. Shedding caused numerous genotype x age interactions in wool weight and its components, as Merinos and BL-M did not shed, and with the WH-M shedding increased most with age in the 1/2 Merinos, and least in the 3/4 Merinos. Due to preferential shedding from the belly and other low-value areas, the WH-M inferiority in total wool weight was less severe for fleece weight. Winter shearing succeeded in harvesting some wool from WH-M that would be shed before a summer shearing, but not enough to alter rankings among genotypes. All WH-M genotypes have wool too coarse, and not enough of it, to compete as a wool sheep with the Merino at current wool prices under usual Australian pastoral conditions. In areas where mustering is difficult or blowfly strike unusually severe, WH-M genotypes may find a niche.

No abstract

We examined relationships between peanut (Arachis hypogae L.) cropping frequency and some properties of the tilled layer of krasnozem and euchrozem soils of the South Burnett area of southeastern Queensland. The average period of cultivation for the sites studied was 22 years. Organic carbon (OC) was not significantly correlated (P<0.05) with the period under cultivation, indicating that OC had reached equilibrium with the cropping pattern imposed. Frequency of peanut cropping in the 10 years before sampling was correlated negatively with OC (r = 0.49 1, P < 0.001), percentage of dry aggregates 0.5-5 mm (r= -0.385, P<0.01) and water stability of dry aggregates 2-5 mm (r = - 0.499, P< 0.001), and positively with percentage dry aggregates < 0.5 mm (r=0.313, P<0.05). Both OC and mean-weight-diameter of water-stable aggregates were approximately halved as frequency of peanut cropping increased from 0 to 10 crops in the 10 years before sampling. Estimated return of dry matter to the soil is consistent with differences in OC, as peanuts produce approximately half the dry matter of alternative crops. However, apparent rates of loss of OC due to peanut cropping are high for soils that are not newly cultivated, and intensive tillage associated with peanut cropping may increase rates of loss of OC due to increased disruption of aggregates.

Nitrogen, phosphorus and potassium concentrations were determined in plant tops harvested every four weeks from nine tropical grasses fertilized with nitrogen on ten occasions at eight week intervals. Nitrogen was applied at three rates-25, 50 and 100 kg/ha (N25, N50, N100)-on each occasion. Grasses were rain-grown without grazing at a site near Gympie with an average annual rainfall of 1160 mm. Overall, nitrogen concentration in the tops increased and potassium concentration decreased with increasing nitrogen application. Phosphorus concentrations were constant at N25 and N50, but were lower at N 100. Mean nitrogen concentration was highest at 2.4% in Pennisetum clandestinum cv. Whittet, and lowest at 1 .9% in Chloris gayana cvv. Callide and Katambora, with intermediate concentrations occurring in Digitaria decumbens, Setaria sphacelata var. sericea cv. Narok, Panicum maximum cvv. Gatton and Makueni, Brachiaria decumbens cv. Basilisk and Paspalurn plicatulum cv. Bryan. Phosphorus concentration was highest in Whittet at 0.38% and lowest in Bryan at 0.25%. Potassium concentration was highest in Whittet at 2.53% and Narok at 2.29% and lowest in Katambora at 1 .48%. The implications of these concentrations and calculated nutrient uptakes are discussed in relation to animal and plant nutrition.