Sheath and mating ability measurements and their interrelationships in Santa Gertrudis bulls

Santa Gertrudis bulls were asessed for sheath characteristics which may influence their performance in a serving capacity test. There was a poor relationship between sheath depth and width and the number of mounts and serves that a bull achieves. Of the traits recorded the 'rosette score' ( conformation of the umbilicus) was negatively correlated with serving ability. The mean number of effective serves was 0.9, 1.5 and 1.4 for 2yr and 3 yr old bulls respectively

Nitrogen and environmental factors influencing macadamia quality

Applications of nitrogen fertiliser in macadamia orchards remain high, despite indications that optimum yields and quality are obtained at a lower rate. This 6-year study examined the effect on quality of 230, 690 and 1150 g nitrogen/tree . year, applied in April (floral initiation), in April and June (inflorescence development), in April, June and November (rapid nut growth and premature nut drop), in April, June, November and January (nut maturation/oil accumulation) or monthly. Higher rates of nitrogen increased kernel recovery by 1% in 5 years out of 6. In 1 year only, 4 or more split applications of the medium and high rates of nitrogen increased kernel recovery by up to 1.6%. These increases were insufficient to compensate for depressed yields (17% lower) at high nitrogen. In good years, when yields were above average, kernel recovery tended to be high and in years with poor yields, kernel recovery tended to be low except when nuts were small. Moderate summer—early autumn rainfall of about 100 mm/month was associated with high kernel recovery whereas very heavy rainfall (>200 mm/month) during this period was detrimental. The percentage of first grade kernels was influenced most by season but was negatively correlated with the rate of nitrogen. Impurities, including immature, deformed, mouldy and insect-damaged kernels, were lowest at low rates of nitrogen and highest during wet harvest seasons. Time of nitrogen application had no significant effect on yield, kernel recovery, the percentage of first-grade kernels or impurities. For sustained high yield and quality, 355 g nitrogen, or 0.8 kg urea/tree.year, applied in April—June is indicated. Agronomic and economic advantages of reducing rates of nitrogen applied to macadamia orchards are enhanced by increasingly important environmental considerations. Multiple regression analyses indicated that the rate, strategy and timing of nitrogen application, rainfall, temperature, flushing and litterfall were correlated with kernel recovery and first-grade kernels but more work is needed to elucidate the significance of these factors

Changing sink strengths influence translocation of phosphonate in avocado (Persea americana Mill.) trees

Translocation of phosphonic acid (H3PO3) in cv. Hass avocado trees was studied after trunk injection with 20% H3PO3, formulated as potassium phosphonate, at three stages of tree phenology during the growing season. Initially, translocation was solely acropetal in the xylem, and H3PO3was detected in the leaves 24 h after treatment. Several days after injection, H3PO3 concentration in the bark of trunks and in roots increased, indicating basipetal phloem transport of H3PO3 from leaves. The rate of accumulation and the final concentration of H3PO3in the roots were directly related to the sink strength of the shoot at the time of injection. For example, trunk injection at the beginning of spring growth flush, when renewal shoots were strong sinks, resulted in low H3PO3 root concentrations (25 8g gfw-1 by 30 days after treatment. These results suggest that strategic timing of injections according to phenological events may greatly improve fungicide efficacy when targeting specific organs for protection

Insulin-Like Growth Factor Levels During Pregnancy in the Cow are Affected by Protein Supplementation in the Maternal Diet

To determine if dietary protein supplementation in early pregnancy alters total circulating insulinlike growth factor (IGF) levels, genetically similar heifers were fed diets containing different levels of protein in the first and second trimesters of gestation. The groups were: low/low (L/L), fed a diet containing 7% crude protein (CP) per kg/DM (low protein) in the first and second trimesters; high/high (H/H), fed a diet containing 14% CP per kg/DM (high protein) in the first and second trimesters; low/high (L/H), fed low protein in the first trimester and high in the second trimester and vice versa for the high/low (H/L) group. At day 62 of gestation, there was a significant difference (

Comparison of growth rates of relocated and local steers

Beef producers have expressed concern that cattle moved from one location to another do not always perform as well as comparable local cattle. Research station records and field trial data were examined to determine the effect of relocation on growth rate using data sets for animals of different age and liveweight at relocation and of different genotypes. 21st Biennial Conference. 8-12 July University of Queensland, Brisbane

Leaf nitrogen as a guide for fertilising macadamia

Despite the lack of evidence for a critical level of leaf nitrogen in macadamia, fertiliser management has been largely based on tentative standards for high yielding trees. Trees on a lower plane of nitrogen nutrition, however, produced higher yields of good quality nuts. This study was therefore carried out to establish the relationship between yield and nitrogen status of trees. Three rates of nitrogen fertiliser (0.5, 1.5 and 2.5 kg urea/tree . year; 230, 690 and 1150 g nitrogen respectively) were applied to macadamia trees in 1 of 5 application strategies: 1 application in April (floral initiation); 2 applications, one in April and one in June (inflorescence development); 3 applications, April, June and November (rapid nut growth and premature nut drop); 4 applications, April, June, November and January (oil accumulation); and 12 monthly split applications. Multiple applications were all equal in size. The association between high yields and low nitrogen status was confirmed. In some, but not all, years, yield was negatively correlated with leaf nitrogen, accounting for 47 and 59% of the variation in yield of commercially acceptable nuts (>19 mm diameter) in 1991 and 1993, respectively. It is therefore recommended that the standard for leaf nitrogen in macadamia be lowered from 1.4–1.5 to 1.3% under Australian conditions. These results raise concerns at the current trend for leaf nitrogen to be as high as 1.8%. It would be prudent to cease nitrogen applications on at least a small experimental block until leaf nitrogen declined to 1.3% and then maintain this level for at least 3 years and monitor yields

Macadamia responses to mild water stress at different phenological stages

Mild water stress was imposed on bearing macadamia trees in through-draining lysimeters at various phenological stages. Water was withheld until a xylem water potential (Ψx) of –1.5 to 2.0 MPa was reached, this being maintained by partial water replenishment at 2-day intervals. Flowering, nut set, nut development, yield, and quality responses were assessed to identify critical, stress-sensitive stages. Stress during nut maturation was particularly detrimental to both yield and quality, although stress during floral development and the premature nut drop also had adverse effects. Low yields were due to reduced nut number and smaller nuts. Lower photosynthesis (c. 2 μmol CO2/m2.s) at –1.5 MPa would account for reduced yield and poorer quality during nut maturation when energy demands of active oil accumulation are high. Stress at floral initiation was generally not detrimental. Overall, stress restricted growth. The rate of girth growth was significantly lower when stress was applied during the dormant floral initiation stage. When stress coincided with normal periods of vegetative growth, flushing was delayed until after re-watering when greater foliage production was stimulated. Judiciously imposing mild stress may be used to manipulate macadamia phenology, although it may not necessarily conserve water. Further refinement would be needed to develop stress manipulation as a practical and reliable management tool to achieve higher yields. Water should be applied to alleviate stress during critical stages of nut development and maturation. Mild stress after the current crop is mature, however, is unlikely to be detrimental to macadamia yield or quality. It may, in fact, be beneficial through manipulation of flushing patterns that influence yield

Macadamia responses to mild water stress at different phenological stages

Mild water stress was imposed on bearing macadamia trees in through-draining lysimeters at various phenological stages. Water was withheld until a xylem water potential (Ψx) of –1.5 to 2.0 MPa was reached, this being maintained by partial water replenishment at 2-day intervals. Flowering, nut set, nut development, yield, and quality responses were assessed to identify critical, stress-sensitive stages. Stress during nut maturation was particularly detrimental to both yield and quality, although stress during floral development and the premature nut drop also had adverse effects. Low yields were due to reduced nut number and smaller nuts. Lower photosynthesis (c. 2 μmol CO2/m2.s) at –1.5 MPa would account for reduced yield and poorer quality during nut maturation when energy demands of active oil accumulation are high. Stress at floral initiation was generally not detrimental. Overall, stress restricted growth. The rate of girth growth was significantly lower when stress was applied during the dormant floral initiation stage. When stress coincided with normal periods of vegetative growth, flushing was delayed until after re-watering when greater foliage production was stimulated. Judiciously imposing mild stress may be used to manipulate macadamia phenology, although it may not necessarily conserve water. Further refinement would be needed to develop stress manipulation as a practical and reliable management tool to achieve higher yields. Water should be applied to alleviate stress during critical stages of nut development and maturation. Mild stress after the current crop is mature, however, is unlikely to be detrimental to macadamia yield or quality. It may, in fact, be beneficial through manipulation of flushing patterns that influence yield

A survey of dairy farmers' practices and attitudes towards some aspects of arable-land management in the Darling Downs and South Burnett regions of Queensland

The Darling Downs and Southern Inland Burnett are important geographical subregions of the Queensland dairy industry. The system of dairy farming in these subregions is unique in Australia in that it is based on grazed annual forage crops rather than pastures. When these soils were first cultivated up to 110 years ago they were inherently fertile. However, erosion and fertility decline has reduced their productive capacity and there is a need for the adoption of farming practices that are less exploitative. In February 1997, a survey was conducted to determine dairy farmers' practices and attitudes toward management strategies that were being recommended to grain farmers in the subtropical cereal belt for sustaining the soil resource base. These strategies included greater use of ley pastures, opportunistic double-cropping, zero-till planting and higher fertiliser inputs. We found that dairy farmers were generally familiar with and understanding of the potential benefits of these approaches to their farming enterprises. However, farmers raised a number of issues that need consideration in the transfer of these practices to dairy forage production. These included concerns that an increased emphasis on pastures would result in lower and less-reliable forage production; that double-cropping is practiced more out of necessity than in the belief it is a better way to farm; that zero tillage may not be suitable on clay soils that have been trampled by cattle and that farmers rely primarily on their own observations of crop performance to determine fertiliser use. These findings have particular implications for research and extension activities conducted with dairy farmers and are also relevant to work conducted with other cropping enterprises that incorporate grazing animals in their farming program

A survey of dairy farmers' practices and attitudes towards some aspects of arable-land management in the Darling Downs and South Burnett regions of Queensland

The Darling Downs and Southern Inland Burnett are important geographical subregions of the Queensland dairy industry. The system of dairy farming in these subregions is unique in Australia in that it is based on grazed annual forage crops rather than pastures. When these soils were first cultivated up to 110 years ago they were inherently fertile. However, erosion and fertility decline has reduced their productive capacity and there is a need for the adoption of farming practices that are less exploitative. In February 1997, a survey was conducted to determine dairy farmers' practices and attitudes toward management strategies that were being recommended to grain farmers in the subtropical cereal belt for sustaining the soil resource base. These strategies included greater use of ley pastures, opportunistic double-cropping, zero-till planting and higher fertiliser inputs. We found that dairy farmers were generally familiar with and understanding of the potential benefits of these approaches to their farming enterprises. However, farmers raised a number of issues that need consideration in the transfer of these practices to dairy forage production. These included concerns that an increased emphasis on pastures would result in lower and less-reliable forage production; that double-cropping is practiced more out of necessity than in the belief it is a better way to farm; that zero tillage may not be suitable on clay soils that have been trampled by cattle and that farmers rely primarily on their own observations of crop performance to determine fertiliser use. These findings have particular implications for research and extension activities conducted with dairy farmers and are also relevant to work conducted with other cropping enterprises that incorporate grazing animals in their farming program