Reducing the risk of herbicide runoff in sugarcane farming through controlled traffic and early-banded application

The off-site transport of agricultural chemicals, such as herbicides, into freshwater and marine ecosystems is a world-wide concern. The adoption of farm management practices that minimise herbicide transport in rainfall-runoff is a priority for the Australian sugarcane industry, particularly in the coastal catchments draining into the World Heritage listed Great Barrier Reef (GBR) lagoon. In this study, residual herbicide runoff and infiltration were measured using a rainfall simulator in a replicated trial on a brown Chromosol with 90–100% cane trash blanket cover in the Mackay Whitsunday region, Queensland. Management treatments included conventional 1.5 m spaced sugarcane beds with a single row of sugarcane (CONV) and 2 m spaced, controlled traffic sugarcane beds with dual sugarcane rows (0.8 m apart) (2mCT). The aim was to simulate the first rainfall event after the application of the photosynthesis inhibiting (PSII) herbicides ametryn, atrazine, diuron and hexazinone, by broadcast (100% coverage, on bed and furrow) and banding (50–60% coverage, on bed only) methods. These events included heavy rainfall 1 day after herbicide application, considered a worst case scenario, or rainfall 21 days after application. The 2mCT rows had significantly (P < 0.05) less runoff (38%) and lower peak runoff rates (43%) than CONV rows for a rainfall average of 93 mm at 100 mm h−1 (1:20 yr Average Return Interval). Additionally, final infiltration rates were higher in 2mCT rows than CONV rows, with 72 and 52 mm h−1 respectively. This resulted in load reductions of 60, 55, 47, and 48% for ametryn, atrazine, diuron and hexazinone from 2mCT rows, respectively. Herbicide losses in runoff were also reduced by 32–42% when applications were banded rather than broadcast. When rainfall was experienced 1 day after application, a large percentage of herbicides were washed off the cane trash. However, by day 21, concentrations of herbicide residues on cane trash were lower and more resistant to washoff, resulting in lower losses in runoff. Consequently, ametryn and atrazine event mean concentrations in runoff were approximately 8 fold lower at day 21 compared with day 1, whilst diuron and hexazinone were only 1.6–1.9 fold lower, suggesting longer persistence of these chemicals. Runoff collected at the end of the paddock in natural rainfall events indicated consistent though smaller treatment differences to the rainfall simulation study. Overall, it was the combination of early application, banding and controlled traffic that was most effective in reducing herbicide losses in runoff. Crown copyright © 2012

A promising and simple method to quantify soil/manure mixing on beef feedlot pens

On beef cattle feed pen surfaces, fresh and decayed manure is mixed with base rock or soil (base). Quantifying this mixing has beneficial applications for aspects including nutrient and greenhouse gas budgeting. However, no practical methods exist to quantify mixing. We investigated if measuring element concentrations in: (A) fresh manure, (B) base material, and (C) pen manure offers a promising method to quantify manure/base mixing on pen surfaces. Using three operational beef feedlots as study sites, we targeted carbon (C), and silicon (Si), which are the two most abundant and easily measurable organic and inorganic elements. Our results revealed that C concentrations were strongly (>15 times) and significantly (P < 0.05) higher whereas Si concentrations strongly (>10 times) and significantly (P < 0.01) lower in fresh manure than base material at all three sites. These relative concentrations were not significantly impacted by manure decay, as determined by an 18-week incubation experiment. This suggested that both of these elements are suitable markers for quantifying base/manure mixing on pens. However, due to the chemical change of manure during decay, C was shown to be an imprecise marker of base/manure mixing. By contrast, using Si to estimate base/manure mixing was largely unaffected by manure decay. These findings were confirmed by measuring C and Si concentrations in stockpiled pen surface manure from one of the sites. Using Si concentrations is a promising approach to quantify base/manure mixing on feed pens given that this element is abundantly concentrated in soils and rocks.

Associations between exposure to viruses and bovine respiratory disease in Australian feedlot cattle

Bovine respiratory disease (BRD) is the most important cause of clinical disease and death in feedlot cattle. Respiratory viral infections are key components in predisposing cattle to the development of this disease. To quantify the contribution of four viruses commonly associated with BRD, a case-control study was conducted nested within the National Bovine Respiratory Disease Initiative project population in Australian feedlot cattle. Effects of exposure to Bovine viral diarrhoea virus 1 (BVDV-1), Bovine herpesvirus 1 (BoHV-1), Bovine respiratory syncytial virus (BRSV) and Bovine parainfluenza virus 3 (BPIV-3), and to combinations of these viruses, were investigated. Based on weighted seroprevalences at induction (when animals were enrolled and initial samples collected), the percentages of the project population estimated to be seropositive were 24% for BoHV-1, 69% for BVDV-1, 89% for BRSV and 91% for BPIV-3. For each of the four viruses, seropositivity at induction was associated with reduced risk of BRD (OR: 0.6–0.9), and seroincrease from induction to second blood sampling (35–60 days after induction) was associated with increased risk of BRD (OR: 1.3–1.5). Compared to animals that were seropositive for all four viruses at induction, animals were at progressively increased risk with increasing number of viruses for which they were seronegative; those seronegative for all four viruses were at greatest risk (OR: 2.4). Animals that seroincreased for one or more viruses from induction to second blood sampling were at increased risk (OR: 1.4–2.1) of BRD compared to animals that did not seroincrease for any viruses. Collectively these results confirm that prior exposure to these viruses is protective while exposure at or after feedlot entry increases the risk of development of BRD in feedlots. However, the modest increases in risk associated with seroincrease for each virus separately, and the progressive increases in risk with multiple viral exposures highlights the importance of concurrent infections in the aetiology of the BRD complex. These findings indicate that, while efficacious vaccines could aid in the control of BRD, vaccination against one of these viruses would not have large effects on population BRD incidence but vaccination against multiple viruses would be expected to result in greater reductions in incidence. The findings also confirm the multifactorial nature of BRD development, and indicate that multifaceted approaches in addition to efficacious vaccines against viruses will be required for substantial reductions in BRD incidence.

Effect of sugarcane cropping systems on herbicide losses in surface runoff

Herbicide runoff from cropping fields has been identified as a threat to the Great Barrier Reef ecosystem. A field investigation was carried out to monitor the changes in runoff water quality resulting from four different sugarcane cropping systems that included different herbicides and contrasting tillage and trash management practices. These include (i) Conventional - Tillage (beds and inter-rows) with residual herbicides used; (ii) Improved - only the beds were tilled (zonal) with reduced residual herbicides used; (iii) Aspirational - minimum tillage (one pass of a single tine ripper before planting) with trash mulch, no residual herbicides and a legume intercrop after cane establishment; and (iv) New Farming System (NFS) - minimum tillage as in Aspirational practice with a grain legume rotation and a combination of residual and knockdown herbicides. Results suggest soil and trash management had a larger effect on the herbicide losses in runoff than the physico-chemical properties of herbicides. Improved practices with 30% lower atrazine application rates than used in conventional systems produced reduced runoff volumes by 40% and atrazine loss by 62%. There were a 2-fold variation in atrazine and >10-fold variation in metribuzin loads in runoff water between reduced tillage systems differing in soil disturbance and surface residue cover from the previous rotation crops, despite the same herbicide application rates. The elevated risk of offsite losses from herbicides was illustrated by the high concentrations of diuron (14mugL-1) recorded in runoff that occurred >2.5months after herbicide application in a 1st ratoon crop. A cropping system employing less persistent non-selective herbicides and an inter-row soybean mulch resulted in no residual herbicide contamination in runoff water, but recorded 12.3% lower yield compared to Conventional practice. These findings reveal a trade-off between achieving good water quality with minimal herbicide contamination and maintaining farm profitability with good weed control.

The tolerance of steers (Bos taurus) to sorghum ergot (Claviceps africana) in a feedlot during the cooler months in sub-tropical Queensland

Two experiments tested the tolerance of steers (Bos taurus) to sorghum ergot (Claviceps africana) during cooler months in south-east Queensland. Sorghum grain containing 2.8% ergot and 28 mg/kg ergot alkaloids (84% dihydroergosine, 10% dihydroelymoclavine, 6% festuclavine) was incorporated into feedlot rations. In a previous study in summer–autumn, ergot (1.1–4.4 mg alkaloids/kg ration) severely reduced performance in steers when the temperature–humidity index (THI; dry bulb temperature °C + 0.36 dew-point temperature °C + 41.2) was ~70, whereas a THI of ~79 was tolerated by steers fed ergot-free rations. Experiment 1 was conducted in winter–spring, with rations containing 0, 2.8, 5.6, 8.2 or 11.2 mg ergot alkaloids/kg ration. All ergot inclusions depressed feed intake (14% average reduction) and growth rate (34% average reduction), even when the weekly average daily THI was less than 65. Rectal temperatures were occasionally elevated in ergot-fed steers (P < 0.05), primarily when the THI exceeded ~65. All ergot inclusions depressed plasma prolactin concentrations in steers. Experiment 2 was predominantly carried out in winter, with weekly average daily THI <65 throughout the experiment. Rations containing 0, 0.28, 0.55 or 1.1 mg ergot alkaloids/kg were fed for 4 weeks but produced no significant effect on feed intakes and growth rates of steers. Alkaloid concentrations were then changed to 0, 2.1, 4.3 and 1.1 mg/kg, respectively. Subsequently, feed intakes declined by 17.5% (P < 0.05), and growth rates by 28% (P > 0.05) in the group receiving 4.3 mg/kg alkaloid, compared with Controls. Plasma prolactin concentrations were depressed, relative to the Controls, by dietary alkaloid inclusion greater than 1.1 mg/kg, with alkaloid intake of 4.3 mg/kg causing the greatest reduction (P < 0.05). Cattle performance in these studies shows steers can tolerate up to ~2 mg ergot alkaloid/kg (0.2% ergot) in feedlot rations under low THI conditions (< ~60–65), but previous findings indicate a much lower threshold will apply at higher THI (>65).

The tolerance of steers (Bos taurus) to sorghum ergot (Claviceps africana) in a feedlot during the cooler months in sub-tropical Queensland

Two experiments tested the tolerance of steers (Bos taurus) to sorghum ergot (Claviceps africana) during cooler months in south-east Queensland. Sorghum grain containing 2.8% ergot and 28 mg/kg ergot alkaloids (84% dihydroergosine, 10% dihydroelymoclavine, 6% festuclavine) was incorporated into feedlot rations. In a previous study in summer–autumn, ergot (1.1–4.4 mg alkaloids/kg ration) severely reduced performance in steers when the temperature–humidity index (THI; dry bulb temperature °C + 0.36 dew-point temperature °C + 41.2) was ~70, whereas a THI of ~79 was tolerated by steers fed ergot-free rations. Experiment 1 was conducted in winter–spring, with rations containing 0, 2.8, 5.6, 8.2 or 11.2 mg ergot alkaloids/kg ration. All ergot inclusions depressed feed intake (14% average reduction) and growth rate (34% average reduction), even when the weekly average daily THI was less than 65. Rectal temperatures were occasionally elevated in ergot-fed steers (P < 0.05), primarily when the THI exceeded ~65. All ergot inclusions depressed plasma prolactin concentrations in steers. Experiment 2 was predominantly carried out in winter, with weekly average daily THI <65 throughout the experiment. Rations containing 0, 0.28, 0.55 or 1.1 mg ergot alkaloids/kg were fed for 4 weeks but produced no significant effect on feed intakes and growth rates of steers. Alkaloid concentrations were then changed to 0, 2.1, 4.3 and 1.1 mg/kg, respectively. Subsequently, feed intakes declined by 17.5% (P < 0.05), and growth rates by 28% (P > 0.05) in the group receiving 4.3 mg/kg alkaloid, compared with Controls. Plasma prolactin concentrations were depressed, relative to the Controls, by dietary alkaloid inclusion greater than 1.1 mg/kg, with alkaloid intake of 4.3 mg/kg causing the greatest reduction (P < 0.05). Cattle performance in these studies shows steers can tolerate up to ~2 mg ergot alkaloid/kg (0.2% ergot) in feedlot rations under low THI conditions (< ~60–65), but previous findings indicate a much lower threshold will apply at higher THI (>65).

Effects of exposure to Bovine viral diarrhoea virus 1 on risk of bovine respiratory disease in Australian feedlot cattle

Viruses play a key role in the complex aetiology of bovine respiratory disease (BRD). Bovine viral diarrhoea virus 1 (BVDV-1) is widespread in Australia and has been shown to contribute to BRD occurrence. As part of a prospective longitudinal study on BRD, effects of exposure to BVDV-1 on risk of BRD in Australian feedlot cattle were investigated. A total of 35,160 animals were enrolled at induction (when animals were identified and characteristics recorded), held in feedlot pens with other cattle (cohorts) and monitored for occurrence of BRD over the first 50 days following induction. Biological samples collected from all animals were tested to determine which animals were persistently infected (PI) with BVDV-1. Data obtained from the Australian National Livestock Identification System database were used to determine which groups of animals that were together at the farm of origin and at 28 days prior to induction (and were enrolled in the study) contained a PI animal and hence to identify animals that had probably been exposed to a PI animal prior to induction. Multi-level Bayesian logistic regression models were fitted to estimate the effects of exposure to BVDV-1 on the risk of occurrence of BRD.Although only a total of 85 study animals (0.24%) were identified as being PI with BVDV-1, BVDV-1 was detected on quantitative polymerase chain reaction in 59% of cohorts. The PI animals were at moderately increased risk of BRD (OR 1.9; 95% credible interval 1.0-3.2). Exposure to BVDV-1 in the cohort was also associated with a moderately increased risk of BRD (OR 1.7; 95% credible interval 1.1-2.5) regardless of whether or not a PI animal was identified within the cohort. Additional analyses indicated that a single quantitative real-time PCR test is useful for distinguishing PI animals from transiently infected animals.The results of the study suggest that removal of PI animals and/or vaccination, both before feedlot entry, would reduce the impact of BVDV-1 on BRD risk in cattle in Australian feedlots. Economic assessment of these strategies under Australian conditions is required. © 2016 Elsevier B.V.

Toxoplasmosis in Indo-Pacific humpbacked dolphins (Sousa chinensis) from Queensland

Objective: To describe the clinical signs, gross pathology, serology, bacteriology, histopathology, electron microscopy and immunohistochemistry findings associated with toxoplasmosis in four Indo-Pacific humpbacked dolphins (Sousa chinensis) that stranded in Queensland in 2000 and 2001. Design: Clinical assessment, gross necropsy, and laboratory examinations. Procedure: Necropsies were performed on four S chinensis to determine cause of death. Laboratory tests including serology, bacteriology, histopathology and transmission electron microscopy were done on the four dolphins. lmmunohistochemistry was done on the brain, heart, liver, lung, spleen and adrenal gland from various dolphins to detect Toxoplasma gondii antigens. Results: Necropsies showed all of four S chinensis that stranded in Queensland in 2000 and 2001 had evidence of predatory shark attack and three were extremely emaciated. Histopathological examinations showed all four dolphins had toxoplasmosis with tissue cysts resembling T gondii in the brain. Tachyzoite stages of T gondii were detected in the lungs, heart, liver, spleen and adrenal gland, variously of all four dolphins. Electron microscopy studies and immunohistochemistry confirmed the tissues cysts were those of Tgondii. All four dolphins also had intercurrent disease including pneumonia, three had peritonitis and one had pancreatitis. Conclusion: Four S chinensis necropsied in Queensland in 2000 and 2001 were found to be infected with toxoplasmosis. It is uncertain how these dolphins became infected and further studies are needed to determine how S chinensis acquire toxoplasmosis. All four dolphins stranded after periods of heavy rainfall, and coastal freshwater runoff may be a risk factor for T gondii infection in S chinensis. This disease should be of concern to wildlife managers since S chinensis is a rare species and its numbers appear to be declining.

Stretching water - Queensland’s water use efficiency cotton and grains adoption program

The Cotton and Grain Adoption Program of the Queensland Rural Water Use Efficiency Initiative is targeting five major irrigation regions in the state with the objective to develop better irrigation water use efficiency (WUE) through the adoption of best management practices in irrigation. The major beneficiaries of the program will be industries, irrigators and local communities. The benefits will flow via two avenues: increased production and profit resulting from improved WUE and improved environmental health as a consequence of greatly reduced runoff of irrigation tailwater into rivers and streams. This in turn will reduce the risk of nutrient and pesticide contamination of waterways. As a side effect, the work is likely to contribute to an improved public image of the cotton and grain industries. In each of the five regions, WUE officers have established grower groups to assist in providing local input into the specific objectives of extension and demonstration activities. The groups also assist in developing growers' perceptions of ownership of the work. Activities are based around four on-farm demonstration sites in each region where irrigation management techniques and hardware are showcased. A key theme of the program is monitoring water use. This is applied both to on-farm storage and distribution as well as to application methods and in-field management. This paper describes the project, its activities and successes.

Plasma Biochemical and Haematological Changes in Steers of Different Temperament during Feedlotting

Correlations between liveweight gains and temperament during feedlotting (Voisinet et al., 1997) may be an indication that cattle of different temperament suffer different degrees of stress. This paper describes the effect of grouping into feedlot pens, cattle of good, poor and mixed (some good and some poor) temperament on blood parameters that are indicators of stress (Bennett et al., 1989). Animal production for a consuming world : proceedings of 9th Congress of the Asian-Australasian Association of Animal Production Societies [AAAP] and 23rd Biennial Conference of the Australian Society of Animal Production [ASAP] and 17th Annual Symposium of the University of Sydney, Dairy Research Foundation, [DRF]. 2-7 July 2000, Sydney, Australia.

Sediment and nutrient losses from exotic Pinus plantation management operations under simulated rainfall

Rainfall simulation experiments were carried out to measure runoff and soil water fluxes of suspended solids, total nitrogen, total phosphorus, dissolved organic carbon and total iron from sites in Pinus plantations on the coastal lowlands of south-eastern Queensland subjected to various operations (treatments). The operations investigated were cultivated and nil-cultivated site preparation, fertilised site preparation, clearfall harvesting and prescribed burning; these treatments were compared with an 8-y-old established plantation. Flow-weighted mean concentrations of total nitrogen and total phosphorus in surface runoff from the cultivated and nil-cultivated site-preparation, clearfall harvest, prescribed burning and 8-y-old established plantation treatments were very similar. However, both the soil water and the runoff from the fertilised site preparation treatment contained more nitrogen (N) and phosphorus (P) than the other treatments - with 3.10 mg N L-1 and 4.32 mg P L-1 (4 and 20 times more) in the runoff. Dissolved organic carbon concentrations in runoff from the nil-cultivated site-preparation and prescribed burn treatments were elevated. Iron concentrations were highest in runoff from the nil-cultivated site-preparation and 8-y-old established plantation treatments. Concentrations of suspended solids in runoff were higher from cultivated site preparation and prescribed burn treatments, and reflect the great disturbance of surface soil at these sites. The concentrations of all analytes were highest in initial runoff from plots, and generally decreased with time. Total nitrogen (mean 7.28, range 0.11-13.27 mg L-1) and total phosphorus (mean 11.60, range 0.06-83.99 mg L-1) concentrations in soil water were between 2 and 10 times greater than in surface runoff, which highlights the potential for nutrient fluxes in interflow (i.e. in the soil above the water table) through the general plantation area. Implications in regard to forest management are discussed, along with results of larger catchment-scale studies.

The efficacy of a vitamin D3 metabolite for improving the myofibrillar tenderness of meat from Bos indicus cattle

The influence of a once only administration of a metabolite of vitamin D3 (HY [middle dot] D(R)-25-hydroxy vitamin D3) on myofibrillar meat tenderness in Australian Brahman cattle was studied. Ninety-six Brahman steers of three phenotypes (Indo-Brazil, US and US/European) and with two previous hormonal growth promotant (HGP) histories (implanted or not implanted with Compudose(R)) were fed a standard feedlot ration for 70 d. Treatment groups of 24 steers were offered daily 10 g/head HY [middle dot] D(R) (125 mg 25-hydroxyvitamin D3) for 6, 4, or 2 d before slaughter. One other group of 24 steers was given the basal diet without HY [middle dot] D(R). Feed lot performance, blood and muscle samples and carcass quality data were collected at slaughter. Calcium, magnesium, potassium, sodium, iron and Vitamin D3 metabolites were measured in plasma and longissimus dorsi muscle. Warner-Bratzler (WB) shear force (peak force, initial yield) and other objective meat quality measurements were made on the longissimus dorsi muscle of each steer after ageing for 1, 7 and 14 d post-mortem at 0-2 [deg]C.There were no significant effects of HY [middle dot] D(R) supplements on average daily gain (ADG, 1.28-1.45 kg/d) over the experimental period. HY [middle dot] D(R) supplements given 6 d prior to slaughter resulted in significantly higher (P (R)) by phenotype/HGP interaction for peak force (P = 0.028), in which Indo-Brazil steers without previous HGP treatment responded positively (increased tenderness) to HY [middle dot] D(R) supplements at 2 d when compared with Indo-Brazil steers previously given HGP. There were no significant effects of treatment on other phenotypes. HY [middle dot] D(R) supplements did not affect muscle or plasma concentrations of calcium, potassium or sodium, but did significantly decrease plasma magnesium and iron concentrations when given 2 d before slaughter. There were no detectable amounts of 25-hydroxyvitamin D3 in the blood or muscle of any cattle at slaughter.

Tillage and the environment in sub-tropical Australia-Tradeoffs and challenges

Tillage is defined here in a broad sense, including disturbance of the soil and crop residues, wheel traffic and sowing opportunities. In sub-tropical, semi-arid cropping areas in Australia, tillage systems have evolved from intensively tilled bare fallow systems, with high soil losses, to reduced and no tillage systems. In recent years, the use of controlled traffic has also increased. These conservation tillage systems are successful in reducing water erosion of soil and sediment-bound chemicals. Control of runoff of dissolved nutrients and weakly sorbed chemicals is less certain. Adoption of new practices appears to have been related to practical and economic considerations, and proved to be more profitable after a considerable period of research and development. However there are still challenges. One challenge is to ensure that systems that reduce soil erosion, which may involve greater use of chemicals, do not degrade water quality in streams. Another challenge is to ensure that systems that improve water entry do not increase drainage below the crop root zone, which would increase the risk of salinity. Better understanding of how tillage practices influence soil hydrology, runoff and erosion processes should lead to better tillage systems and enable better management of risks to water quality and soil health. Finally, the need to determine the effectiveness of in-field management practices in achieving stream water quality targets in large, multi-land use catchments will challenge our current knowledge base and the tools available.

The environmental fate of diuron under a conventional production regime in a sugarcane farm during the plant cane phase

BACKGROUND: Field studies of diuron and its metabolites 3-(3,4-dichlorophenyl)-1-methylurea (DCPMU), 3,4-dichlorophenylurea (DCPU) and 3,4-dichloroaniline (DCA) were conducted in a farm soil and in stream sediments in coastal Queensland, Australia. RESULTS: During a 38 week period after a 1.6 kg ha^-1 diuron application, 70-100% of detected compounds were within 0-15 cm of the farm soil, and 3-10% reached the 30-45 cm depth. First-order t1/2 degradation averaged 49 ± 0.9 days for the 0-15, 0-30 and 0-45 cm soil depths. Farm runoff was collected in the first 13-50 min of episodes lasting 55-90 min. Average concentrations of diuron, DCPU and DCPMU in runoff were 93, 30 and 83-825 µg L^-1 respectively. Their total loading in all runoff was >0.6% of applied diuron. Diuron and DCPMU concentrations in stream sediments were between 3-22 and 4-31 µg kg^-1 soil respectively. The DCPMU/diuron sediment ratio was >1. CONCLUSION: Retention of diuron and its metabolites in farm topsoil indicated their negligible potential for groundwater contamination. Minimal amounts of diuron and DCMPU escaped in farm runoff. This may entail a significant loading into the wider environment at annual amounts of application. The concentrations and ratio of diuron and DCPMU in stream sediments indicated that they had prolonged residence times and potential for accumulation in sediments. The higher ecotoxicity of DCPMU compared with diuron and the combined presence of both compounds in stream sediments suggest that together they would have a greater impact on sensitive aquatic species than as currently apportioned by assessments that are based upon diuron alone.