Soil properties and crop yields in a dryland Vertisol sown with cotton-based crop rotations

Information on the effects of growing cotton (Gossypium hirsutum L.)-based crop rotations on soil quality of dryland Vertisols is sparse. The objective of this study was to quantify the effects of growing cereal and leguminous crops in rotation with dryland cotton on physical and chemical properties of a grey Vertisol near Warra, SE Queensland, Australia. The experimental treatments, selected after consultations with local cotton growers, were continuous cotton (T1), cotton-sorghum (Sorghum bicolor (L.) Moench.) (T2), cotton-wheat (Triticum aestivum L.) double cropped (T3), cotton-chickpea (Cicer arietinum L.) double cropped followed by wheat (T4) and cotton-wheat (T5). From 1993 to 1996 land preparation was by chisel ploughing to about 0.2 m followed by two to four cultivations with a Gyral tyne cultivator. Thereafter all crops were sown with zero tillage except for cultivation with a chisel plough to about 0.07-0.1 m after cotton picking to control heliothis moth pupae. Soil was sampled from 1996 to 2004 and physical (air-filled porosity of oven-dried soil, an indicator of soil compaction; plastic limit; linear shrinkage; dispersion index) and chemical (pH in 0.01 M CaCl2, organic carbon, exchangeable Ca, Mg, K and Na contents) properties measured. Crop rotation affected soil properties only with respect to exchangeable Na content and air-filled porosity. In the surface 0.15 m during 2000 and 2001 lowest air-filled porosity occurred with T1 (average of 34.6 m3/100 m3) and the highest with T3 (average of 38.9 m3/100 m3). Air-filled porosity decreased in the same depth between 1997 and 1998 from 45.0 to 36.1 m3/100 m3, presumably due to smearing and compaction caused by shallow cultivation in wet soil. In the subsoil, T1 and T2 frequently had lower air-filled porosity values in comparison with T3, T4 and T5, particularly during the early stages of the experiment, although values under T1 increased subsequently. In general, compaction was less under rotations which included a wheat crop (T3, T4, T5). For example, average air-filled porosity (in m3/100 m3) in the 0.15-0.30 m depth from 1996 to 1999 was 19.8 with both T1 and T2, and 21.2 with T3, 21.1 with T4 and 21.5 with T5. From 2000 to 2004, average air-filled porosity (in m3/100 m3) in the same depth was 21.3 with T1, 19.0 with T2, 19.8 with T3, 20.0 with T4 and 20.5 with T5. The rotation which included chickpea (T4) resulted in the lowest exchangeable Na content, although differences among rotations were small. Where only a cereal crop with a fibrous root system was sown in rotation with cotton (T2, T3, T5) linear shrinkage in the 0.45-0.60 m depth was lower than in rotations, which included tap-rooted crops such as chickpea (T4) or continuous cotton (T1). Dispersion index and organic carbon decreased, and plastic limit increased with time. Soil organic carbon stocks decreased at a rate of 1.2 Mg/ha/year. Lowest average cotton lint yield occurred with T2 (0.54 Mg/ha) and highest wheat yield with T3 (2.8 Mg/ha). Rotations which include a wheat crop are more likely to result in better soil structure and cotton lint yield than cotton-sorghum or continuous cotton.

Sap properties and alk(en)ylresorcinol concentrations in Australian-grown mangoes.

Physical and chemical properties of sap and sap concentrations of constitutive alk(en)ylresorcinols were determined in several varieties of mango grown in different locations in Queensland, Australia, over two consecutive cropping seasons. Sap weight from individual fruit, sap pH, percentage of non-aqueous sap and concentrations of constitutive alk(en)ylresorcinols (5-n-heptadecenylresorcinol and 5-n-pentadecylresorcinol) in sap varied significantly among the varieties. 'Calypso', 'Keitt', 'Kensington Pride' and 'Celebration' had the greatest proportion of non-aqueous sap, whereas 'Nam Doc Mai' had the least. The highest concentrations of 5-n-heptadecenylresorcinol were found in the sap of 'Kensington Pride', and the lowest in 'Honey Gold' and 'Nam Doc Mai'. Highest concentrations of 5-n-pentadecylresorcinol were found in sap of 'Calypso' and 'Celebration', and the lowest levels were in 'Honey Gold' and 'Nam Doc Mai'. There was a direct relationship between the percentage of non-aqueous sap and the concentrations of alk(en)ylresorcinols (r(2) = 0.77 for 5-n-heptadecenylresorcinol, and r(2) = 0.87 for 5-n-pentadecylresorcinol). The alk(en)ylresorcinols were distributed mainly in the upper non-aqueous phase of 'Kensington Pride' sap. Growing location also had significant effects on the composition of mango sap but the effects appeared to be related to differences in maturity. Sap removal is necessary to prevent sapburn, but considerable quantities of alk(en)ylresorcinols that assist in protecting the harvested fruit from anthracnose disease are also removed.

Characterization of tree-to-tree variation in morphological, nutritional and medicinal properties of Canarium indicum nuts

As part of a feasibility study of the commercialization potential of C. indicum nuts as Agroforestry Tree Products in Papua New Guinea, preliminary characterization studies have examined the tree-to-tree variation in morphological traits (nut and kernel mass and kernel:nut ratio), as well as nutritional (carbohydrate, fat, protein, sodium, vitamin E) and medicinal traits (anti-oxidant activity, anti-inflammatory activity and phenolic content) of kernels from 18 to 72 trees in a small number of different villages of Papua New Guinea (East New Britain Province). There was continuous variation in these traits indicating opportunities for multiple trait cultivar development targeted at food and pharmaceutical markets. Certain traits, for example anti-inflammatory activity, in which tree-to-tree variation was highly significant, present greater opportunities than others, such as saturated:unsaturated fatty acid ratio. This intraspecific variation was greater within populations than between populations. The data presented has allowed the development of a strategy to domesticate C. indicum for cultivation in homegardens and cocoa-coconut agroforests, using a participatory approach aimed at the production of agroforestry tree products (AFTPs) to empower small-holders and enhance their livelihoods and income.

Odour sampling. 2. Comparison of physical and aerodynamic characteristics of sampling devices: A review

Sampling devices differing greatly in shape, size and operating condition have been used to collect air samples to determine rates of emission of volatile substances, including odour. However, physical chemistry principles, in particular the partitioning of volatile substances between two phases as explained by Henrys Law and the relationship between wind velocity and emission rate, suggests that different devices cannot be expected to provide equivalent emission rate estimates. Thus several problems are associated with the use of static and dynamic emission chambers, but the more turbulent devices such as wind tunnels do not appear to be subject to these problems. In general, the ability to relate emission rate estimates obtained from wind tunnel measurements to those derived from device-independent techniques supports the use of wind tunnels to determine emission rates that can be used as input data for dispersion models.

New insights into the altered adhesive and mechanical properties of red blood cells parasitized by Babesia bovis

Sequestration of parasite-infected red blood cells (RBCs) in the microvasculature is an important pathological feature of both bovine babesiosis caused by Babesia bovis and human malaria caused by Plasmodium falciparum. Surprisingly, when compared with malaria, the cellular and molecular mechanisms that underlie this abnormal circulatory behaviour for RBCs infected with B. bovis have been relatively ignored. Here, we present some novel insights into the adhesive and mechanical changes that occur in B. bovis-infected bovine RBCs and compare them with the alterations that occur in human RBCs infected with P. falciparum. After infection with B. bovis, bovine RBCs become rigid and adhere to vascular endothelial cells under conditions of physiologically relevant flow. These alterations are accompanied by the appearance of ridge-like structures on the RBC surface that are analogous, but morphologically and biochemically different, to the knob-like structures on the surface of human RBCs infected with P. falciparum. Importantly, albeit for a limited number of parasite lines examined here, the extent of these cellular and rheological changes appear to be related to parasite virulence. Future investigations to identify the precise molecular composition of ridges and the proteins that mediate adhesion will provide important insight into the pathogenesis of both babesiosis and malaria.

Soil type does not affect seed ageing when soil water potential and temperature are controlled

To investigate the effects of soil type on seed persistence in a manner that controlled for location and climate variables, three weed species—Gomphocarpus physocarpus (swan plant), Avena sterilis ssp. ludoviciana (wild oat) and Ligustrum lucidum (broadleaf privet)—were buried for 21 months in three contrasting soils at a single location. Soil type had a significant effect on seed persistence and seedling vigour, but soil water content and temperature varied between soils due to differences in physical and chemical properties. Warmer, wetter conditions favoured shorter persistence. A laboratory-based test was developed to accelerate the rate of seed ageing within soils, using controlled superoptimal temperature and moisture conditions (the soil-specific accelerated ageing test, SSAAT). The SSAAT demonstrated that soil type per se did not influence seed longevity. Moreover, the order in which seeds aged was the same whether aged in the field or SSAAT, with L. lucidum being shortest-lived and A. sterilis being longest-lived of the three species.

Characterisation of sweetpotato from Papua New Guinea and Australia: Physicochemical, pasting and gelatinisation properties.

The physicochemical and functional properties of flours from 25 Papua New Guinean and Australian sweetpotato cultivars were evaluated. The cultivars (white-, orange-, cream-, and purple-fleshed, and with dry matter, from 15 to 28 g/100 g), were obovate, oblong, elliptic, curved, irregular in shape, and essentially thin-cortexed (1-2 mm). Flour yield was less than 90 g/100 g solids, while starch, protein, amylose, water absorption and solubility indices, as well as total sugars, varied significantly (p < 0.05). Potassium, sodium, calcium, and phosphorus were the major minerals measured, and there were differences in the pasting properties, which showed four classes of shear-thinning and shear-thickening behaviours. Differential scanning calorimetry showed single-stage gelatinisation behaviour, with cultivar-dependent temperatures (61-84 degrees C) and enthalpies (12-27 J/g dry starch). Oval-, round- and angular-shaped granules were observed with a scanning electron microscope, while X-ray diffraction revealed an A-type diffraction pattern in the cultivars, with about 30% crystallinity. This study shows a wide range of sweetpotato properties, reported for the first time.

Quantifying differences between treated and untreated coir substrate

The aim of this project was to quantify differences between treated and untreated coir (coconut industrial residues) products and to identify differences in growth, yield and quality of cut flowers grown in different coir products. This has been brought about largely by the concern that some coir products, washed in low quality (saline) water may have detrimental effects on plant productivity and quality. There is concern in the flower production industry and among media suppliers, that lower quality products are favoured due to price alone, which as this project shows is a false economy. Specifically the project examined: • Differences in physical and chemical properties of treated and untreated coir along with another commonly used growing media in the flower industy; • Potential improvements in yield and quality of Gerbera (Gerbera jamesonii); • Potential differences in vase life of Gerbera as a result of the different growing media; and • Cost-benefit implications of treated (more expensive) coir substrate products versus untreated (less expensive) coir including any subsequent differences in yield and quality. By first examining the physical and some chemical properties of different coir substrates and other industry standard media, the researchers have been able to validate the concerns raised about the potential quality issues in coir based growing media. There was a great deal of variation in both the electrical conductivity and sodium contents. Physical properties were also variable as expected since manufacturers are able to target the specific physical preferences of plants through manipulation of the particle size distribution. A field trial was conducted under protected cropping practices in which three growing media were compared in terms of total productivity and also flower quality parameters such as stem length, flower diameter and vase life. The trial was a completely randomised design with the three growing media comprising treated coir discs, untreated coir discs and a pine bark coir mix. Four cultivars of Gerbera were assessed: Balance®; Carambole®; Dune® and Picobello®, all new products from Florist de Kwakel B.V., Denmark. Initial expansion from tissue culture was conducted at the Highsun Express Facility, Ormiston, Queensland. The trial included 12 replications of each cultivar in each media (a total of 144 plants) to ensure all data collected, and the derived conclusions were statistically rigorous. The coir supplied with no pre-treatment or buffering produced significantly less flowers than those grown in a pine bark coir mix or the pre-treated coir. Interestingly, the pine bark coir mix produced a greater number of flowers. However, the flowers produced in the pine bark coir mix were generally a shorter length stem. Productivity data, combined with flower quality data and component costs were all analysed through a cost/benefit economic model which showed that the greater revenue from better stem length outweighed the stem numbers, giving a cost benefit ratio of 2.58 for treated coir, 2.49 for untreated coir and 2.52 for pine bark coir mix. While this does not seem a large difference, when considering the number of plants a producer maintains can be upwards of 50,000 the difference in revenue would be, at a minimum $60,000 in this example. In conclusion, this project has found that there are significant effects on plant health, growth, yield and quality between those grown in treated and untreated coir. The outcome being growers can confidently invest in more expensive treated products with the assurance that benefits will outweigh initial cost. It is false economy to favour untreated coir products based on price alone. Producers should ensure they fully understand the production processes when purchasing growing media. Rather than targeting lower priced materials, it is recommended that quality be the highest priority in making this management decision. In making recommendations for future research and development it was important to consider conclusions from other researchers as well as those of the current project. It has been suggested that the media has greater longevity, which although not captured in this study could also lead to further cost efficiencies. Assessment of the products over a longer time period, and using a wider range of plant species are the major recommendations for further research to ensure greater understanding as to the importance in choosing the right growing media to meet specific needs.

Mile-a-minute (Mikania micrantha): its distribution, growth and physical and socio-economic impacts in Papua New Guinea

Mikania micrantha, Kunth. H.B.K (Asteraceae) or mile-a-minute is a weed of Neotropical origin in 17 Pacific Island countries. It is becoming increasingly regarded as an invasive weed in Papua New Guinea and is now the focus of an Australian Government-funded biological control program. As part of the program, growth rates, distribution and physical and socia-economic impacts were studied to obtain baseline data and to assist with the field release of biological control agents. Through public awareness campaigns and dedicated surveys, mikania has been reported in most lowland provinces. It is particularly widespread in East New Britain and West New Britain Province. In field trials, mikania grew more than 1 metre per month in open sunny areas but slightly slower when growing under cocoa. The weed invades a wide range of land types, impacting on plantations and food gardens, smothering pawpaw, young cocoa, banana, taro, young oil palms and ornamental plants. In socia-economic surveys, mikania was found to have severe impacts on crop production and income generated through reduced yields and high weeding costs. These studies suggest that there would be substantial benefits to the community if biological control of mikania is successful.

Evaluation of wood characteristics of tropical post-mid rotation plantation Eucalyptus cloeziana and E. pellita: Part (c) Wood quality and structural properties.

This study provides information about wood quality, structural properties, processing characterists and product suitability of wood harvested from fast-grown hardwood plantations. Wood quality attributes tested included density, extractive content, unit shrinkage, heartwood proportion and sapwood width. Structural properties tested included small clear and full section strength and stiffness, hardness, joint group, visual grade assessment and natural vibration-based grade assessment. The variation between the inner, intermediate and outer heartwood zones and the variation between provenances was also tested. Overall, the wood qualtiy attributes measured for 19 year-old E. cloeziana and 15 year-old E. pellita plantation material fall between those expected from the wood of mature, native forest trees and those found in younger plantation material of the same species.

Mikania micrantha Kunth (Asteraceae) (Mile-a-Minute): Its Distribution and Physical and Socioeconomic Impacts in Papua New Guinea

Mikania micrantha or mile-a-minute is regarded as a major invasive weed in Papua New Guinea (PNG) and is now the target of a biological control program. As part of the program, distribution and physical and socioeconomic impacts of M. micrantha were studied to obtain baseline data and to assist with field release of biological control agents. Through public awareness campaigns and dedicated surveys, M. micrantha has been reported in all 15 lowland provinces. It is particularly widespread in East New Britain, as well as in West New Britain and New Ireland. A CLIMEX model suggests that M. micrantha has the potential to continue to spread throughout all lowland areas in PNG. The weed was found in a wide range of land uses, impacting on plantations and food gardens and smothering papaya, young cocoa, banana, taro, young oil palms, and ornamental plants. In socioeconomic surveys, M. micrantha was found to have severe impacts on crop production and income generated through reduced yields and high weeding costs, particularly in subsistence mixed cropping systems. About 89% of all respondents had M. micrantha on their land, and 71% of respondents had to weed monthly. Approximately 96% of respondents in subsistence mixed cropping systems used only physical means of control compared with 68% of respondents in other farming systems. About 45% of all respondents estimated that M. micrantha causes yield losses in excess of 30%. These studies suggest that there would be substantial benefits to landholders if biological control of M. micrantha were to be successful.

Estimates of genetic parameters for growth and wood properties in Eucalyptus pellita F. Muell. to support tree breeding in Vietnam

Key message Eucalyptus pellita demonstrated good growth and wood quality traits in this study, with young plantation grown timber being suitable for both solid and pulp wood products. All traits examined were under moderate levels of genetic control with little genotype by environment interaction when grown on two contrasting sites in Vietnam. Context Eucalyptus pellita currently has a significant role in reforestation in the tropics. Research to support expanded of use of this species is needed: particularly, research to better understand the genetic control of key traits will facilitate the development of genetically improved planting stock. Aims This study aimed to provide estimates of the heritability of diameter at breast height over bark, wood basic density, Kraft pulp yield, modulus of elasticity and microfibril angle, and the genetic correlations among these traits, and understand the importance of genotype by environment interactions in Vietnam. Methods Data for diameter and wood properties were collected from two 10-year-old, open-pollinated progeny trials of E. pellita in Vietnam that evaluated 104 families from six native range and three orchard sources. Wood properties were estimated from wood samples using near-infrared (NIR) spectroscopy. Data were analysed using mixed linear models to estimate genetic parameters (heritability, proportion of variance between seed sources and genetic correlations). Results Variation among the nine sources was small compared to additive variance. Narrow-sense heritability and genetic correlation estimates indicated that simultaneous improvements in most traits could be achieved from selection among and within families as the genetic correlations among traits were either favourable or close to zero. Type B genetic correlations approached one for all traits suggesting that genotype by environment interactions were of little importance. These results support a breeding strategy utilizing a single breeding population advanced by selecting the best individuals across all seed sources. Conclusion Both growth and wood properties have been evaluated. Multi-trait selection for growth and wood property traits will lead to more productive populations of E. pellita both with improved productivity and improved timber and pulp properties.