Modelling phosphorus exports from rain-fed and irrigated pastures in southern Australia

Soil Research ◽  
2005 ◽  
Vol 43 (6) ◽  
pp. 745 ◽  
Author(s):  
D. Nash ◽  
L. Clemow ◽  
M. Hannah ◽  
K. Barlow ◽  
P. Gangaiya
Keyword(s):  
Component Model ◽  
Year Effect ◽  
Storm Flow ◽  
Additive Component ◽  
Eastern Australia ◽  
Grazing Systems ◽  
Fertiliser Application ◽  
Excessive Nutrients ◽  
Major Factors ◽  
Land Manager

Pasture-based grazing systems contribute to the excessive nutrients found in some streams in south-eastern Australia. This study investigated phosphorus (P) exported in runoff from a rain-fed dairy pasture (Darnum) and 4 bays of irrigated dairy pasture (MRF). Runoff was monitored for 7 years at Darnum and 2 years at the MRF to identify factors associated with the variation in total P (TP) concentrations between events. The flow-weighted mean annual P concentrations in runoff varied between 3.3 and 28.2 mg TP/L for Darnum and 6.2 and 31.5 mg TP/L for the MRF. The relationships between TP concentrations in runoff and days between fertiliser application and runoff, days between grazing and runoff, and total storm flow were examined using an additive component model that explained 61% and 70% of the variation in log-transformed TP for Darnum and the MRF, respectively. The interval between application of fertiliser and runoff and the effect of year were highly significant and explained most of the variation in TP. Grazing and fertiliser application were identified as the major factors that may affect TP concentrations that the land manager can control (preventable). The estimates of year effect (i.e. the component of TP not explained by the other variables and over which the land manager had no apparent means of control) ranged from 1.60 mg (s.e. 1.99) to 7.14 mg (s.e. 1.90) TP/L in non-drought years (>45 kL/ha runoff annually). The year effect averaged 5.7 and 6.9 mg TP/L for Darnum and the MRF, respectively. It is shown that an additive component model provides a useful structure for investigating similar, field-scale data.

Optimal management of fertiliser and stocking rate in temperate grazing systems

2010 ◽  
Vol 50 (1) ◽  
pp. 6 ◽  
Author(s):  
Karel Mokany ◽  
Andrew D. Moore ◽  
Phillip Graham ◽  
Richard J. Simpson
Keyword(s):  
Cash Flow ◽  
Application Rate ◽  
Optimal Management ◽  
Stocking Rate ◽  
Eastern Australia ◽  
Grazing Systems ◽  
Fertiliser Application ◽  
Gross Margins ◽  
Stocking Rates

Phosphorus (P) fertilisers are one of the key tools available for increasing pasture production and the profitability of grazing enterprises. However, recent rapid changes in fertiliser price have increased the importance of developing optimal management strategies for applying P fertiliser and setting stocking rates. We applied a novel combination of process-based grazing systems modelling and randomised cash flow analyses to examine how changes in fertiliser price affect optimal fertiliser application rates and stocking rates for sheep grazing systems in south-eastern Australia, simultaneously taking into account long-term economic viability and environmental sustainability. We used ‘GrassGro’, a grazing systems decision support tool, to simulate three sheep enterprise types (Merino wethers, Merino ewes, crossbred ewes) at two locations (Hamilton, Victoria; Bookham, New South Wales). Gross margins from each year simulated in GrassGro (1966–2007) were randomised 500 times and input to a cash flow analysis that identified the financially optimal stocking rate for a range of fertiliser applications and the financial risk frontiers (combinations of stocking rate and fertiliser input for which the enterprise becomes financially unviable). For all enterprises examined at both locations, the optimal combinations of stocking rate and fertiliser application rate did not vary markedly as fertiliser price changed. Regardless of enterprise type or location, the fertiliser application rate at which the highest gross margins were achieved provided the greatest range of stocking rates that were both financially viable and environmentally sustainable. Increases in fertiliser price reduced the combinations of stocking rate and fertiliser application rate that were viable in the long term, emphasising the importance of well informed grazing management decisions.

Grenadiers of the World Oceans: Biology, Stock Assessment, and Fisheries

2008 ◽  
Keyword(s):  
Continental Slope ◽  
Ross Sea ◽  
Stock Assessment ◽  
Trawl Survey ◽  
Factors Affecting ◽  
Year Effect ◽  
Macrourus Whitsoni ◽  
Catch Rates ◽  
Potential Methods ◽  
Major Factors

<em>Abstract</em>.—An exploratory longline fishery for toothfish (<em>Dissostichus </em>spp.) in the Ross Sea, Antarctica has been carried out since 1997. The main bycatch species in this fishery is the grenadier, <em>Macrourus whitsoni. </em>No assessments have been carried out of the impact of the fishery on grenadiers, although they have life history characteristics that make them vulnerable to overexploitation. The aims of this research were two-fold; firstly, to characterize the bycatch fishery and to determine factors affecting bycatch rates; and secondly to examine potential methods of monitoring its abundance. A standardized CPUE analysis was used to determine factors affecting bycatch rates of grenadiers in the fishery. The analysis was based on fine-scale haul-by-haul data from all vessels in the fishery from 1999 to 2005. The major factors influencing grenadier bycatch were vessel, area, and depth. Catch rates of grenadiers were highest along the continental slope of the Ross Sea in depths from 600 to 1000 m, and there was an order of magnitude difference in grenadier catch rates between different vessels. Examination of vessel characteristics showed that catch rates of grenadiers were significantly lower with the Spanish line system than with the autoline system. There are several plausible reasons for this difference, including hook location with respect to the seabed, bait type, and differences in levels of reporting of bycatch between vessels. Various approaches to monitoring and assessing grenadiers in the Ross Sea fishery were explored. We conclude that the year effect from the standardized CPUE analysis is unlikely to be monitoring abundance but instead probably reflect changes in gear characteristics, fisher behavior, and targeting of effort. Trends in the length composition of the catch are confounded with depth, and are also of limited value at present. We consider that the best approach to obtaining abundance estimates for grenadiers in the Ross Sea would be to carry out a random bottom trawl survey of the continental slope.

The effect of perennial ryegrass ploidy and white clover inclusion on milk production of dairy cows

2020 ◽  
Vol 60 (1) ◽  
pp. 143 ◽  
Author(s):  
Bríd McClearn ◽  
Trevor Gilliland ◽  
Clare Guy ◽  
Michael Dineen ◽  
Fergal Coughlan ◽  
...  
Keyword(s):  
Dairy Cows ◽  
Milk Production ◽  
Perennial Ryegrass ◽  
White Clover ◽  
Application Rate ◽  
Dairy Farmers ◽  
Increase Milk Production ◽  
Grazing Systems ◽  
Fertiliser Application ◽  
Grazing Dairy Cows

Grazed grass is considered the cheapest feed available for dairy cows in temperate regions, and to maximise profits, dairy farmers must utilise this high-quality feed where possible. Recent research has reported that including white clover (Trifolium repens L.) in grass swards can have a positive effect on milk production. The aim of the present study was to quantify the effect of tetraploid and diploid perennial ryegrass (Lolium perenne L.; PRG) swards sown with and without white clover on the milk production of grazing dairy cows. Four grazing treatments were used for the study; tetraploid-only PRG swards, diploid-only PRG swards, tetraploid PRG with white clover swards and diploid PRG with white clover swards. Thirty cows were assigned to each treatment and swards were rotationally grazed at a stocking rate of 2.75 cows/ha and a nitrogen-fertiliser application rate of 250 kg/ha annually. There was no significant effect of ploidy on milk production. Over the present 4-year study, cows grazing the PRG–white clover treatments had greater milk yields (+597 kg/cow.year) and milk-solid yield (+48 kg/cow.year) than cows grazing the PRG-only treatments. This significant increase in milk production suggests that the inclusion of white clover in grazing systems can be effectively used to increase milk production of grazing dairy cows.

Response of field-grown cotton (Gossypium hirsutum L.) to phosphorus fertilisation on alkaline soils in eastern Australia

Soil Research ◽  
2004 ◽  
Vol 42 (8) ◽  
pp. 913 ◽  
Author(s):  
C. G. Dorahy ◽  
I. J. Rochester ◽  
G. J. Blair
Keyword(s):  
Field Experiments ◽  
P Uptake ◽  
Lint Yield ◽  
Alkaline Soils ◽  
Critical Limit ◽  
Soil P ◽  
Application Rates ◽  
Eastern Australia ◽  
P Application ◽  
Fertiliser Application

Abstract. Seventeen field experiments were conducted on alkaline soils in eastern Australia between 1997 and 2000 to evaluate irrigated cotton response to phosphorus (P) fertilisation. Only 3 experiments demonstrated significant (P < 0.05) increases in crop P uptake or lint yield with P application. Comparison of several soil P tests revealed that Colwell (bicarbonate) P provided the best correlation with P uptake at early flowering and lint yield. Soil P may limit cotton growth where Colwell-P concentrations are <6 mg/kg. Soil P concentrations at most of the sites were well above this critical limit, so P fertiliser application was not required. Average P uptake at physiological cut-out and P removal in seed cotton was 21 and 15 kg P/ha, respectively. Apparent P fertiliser recovery was variable (0–67%) and may have contributed to the lack of response that was observed in 14 out of the 17 experiments. It is recommended that at least 40 kg P/ha be applied to soils with Colwell-P concentrations <6 mg/kg to increase soil P reserves. Application rates of at least 20 kg P/ha are recommended where Colwell-P falls between 6 and 12 mg/kg to maintain soil P fertility.

Decrease in phosphorus concentrations when P fertiliser application is reduced or omitted from grazed pasture soils

Soil Research ◽  
2014 ◽  
Vol 52 (3) ◽  
pp. 282 ◽  
Author(s):  
Jessica Coad ◽  
Lucy Burkitt ◽  
Warwick Dougherty ◽  
Leigh Sparrow
Keyword(s):  
Environmental Sustainability ◽  
Soil P ◽  
Grazed Pasture ◽  
Extractable P ◽  
Grazing Systems ◽  
Intensively Managed ◽  
Fertiliser Application ◽  
Changes Over Time ◽  
Proportional Decrease ◽  
Extractable Soil

Many intensively managed soils contain phosphorus (P) concentrations greater than required for optimum production. Soils with P concentrations in excess of the agronomic optimum can have unnecessary losses of P that can adversely affect water bodies. Reducing excessive soil-P concentrations is important for the economic and environmental sustainability of intensive agriculture, such as the Australian dairy industry. However, little is known of decreases in extractable soil-P concentrations when P fertiliser applications are reduced or omitted from soils with P concentrations and properties representative of intensive pasture grazing systems. Decreases in extractable P (calcium chloride (CaCl2), Olsen and Colwell) were monitored for up to 4.5 years for six Australian grazed pasture soils (Red Ferrosol, Brown Kurosol, Grey Dermosol, Brown Dermosol, Podosol and Hydrosol) with contrasting textures and P-buffering indices (PBI). Sixteen treatments consisting of four initial extractable-P concentrations (Pinit) paired with four ongoing P fertiliser rates (Pfert) were established for each of the six soils, except on an extremely low-PBI Podosol, where a range of Pinit concentrations could not be established. The resultant decreases in P were larger with higher Pinit concentration and lower rate of ongoing Pfert, except in the extremely low PBI Podosol where decreases in initially high CaCl2-P concentrations were large irrespective of ongoing Pfert. There was a greater proportional decrease in the environmentally extractable P compared with agronomically extractable P, with mean decreases in CaCl2-P of 57%, Olsen-P of 25%, and Colwell-P of 12%. The Pinit concentrations, which were well above agronomic optimum, remained above this target. This study advances scientific knowledge of extractable soil-P concentrations when P fertiliser inputs are withheld or reduced from grazed pasture soils, and aids land and catchment managers in estimating likely changes over time.

Study on Downburst Wind Field Characteristics under Mountainous Terrain

2014 ◽  
Vol 580-583 ◽  
pp. 2954-2957
Author(s):  
Hai Tao Shi ◽  
Yuan Ze Wu ◽  
Sun Yi ◽  
Bai Feng Ji
Keyword(s):  
Wind Field ◽  
Wind Profile ◽  
Point Of View ◽  
Mountainous Terrain ◽  
Two Dimensional ◽  
Terrain Model ◽  
The Core ◽  
Storm Flow ◽  
Mountain Terrain ◽  
Major Factors

Downburst is a strong downdraft thunderstorm in the ground formed after the violent impact and spread along the ground very sudden and destructive winds near the ground short. From an engineering point of view for the structure of wind-resistant design, researching downburst wind field characteristics and ultimately determining a reasonable downburst wind profile is one of the core objectives of the study. Terrain conditions are the major factors of downburst wind field characteristics based on the typical mountain terrain on the wind storm flow condition, this paper established typical 2D slope mountain terrain model, using the method of computational fluid dynamics to calculate the velocity contours and pressure cloud in different locations of the mountain. Finally we get the two-dimensional slope typical mountain terrain wind field distribution.

Fertiliser N and P applications on two Vertosols in north-eastern Australia. 2. Grain P concentration and P removal in grain from two long-term experiments

2009 ◽  
Vol 60 (3) ◽  
pp. 218 ◽  
Author(s):  
David W. Lester ◽  
Colin J. Birch ◽  
Chris W. Dowling
Keyword(s):  
Grain Yield ◽  
Grain Production ◽  
Winter Cereal ◽  
P Concentration ◽  
Eastern Australia ◽  
North Eastern ◽  
Legume Crops ◽  
Fertiliser Application ◽  
P Removal

Within north-eastern Australia’s grain-production region there are few reports outlining nitrogen (N) and phosphorus (P) fertiliser effects on grain P concentration and P removal in grain. Two long-term N × P fertiliser experiments with different cultivation durations were conducted, one at ‘Colonsay’ on the Darling Downs in southern Queensland (commencing 1985 after 40 years of cultivation), and the other at ‘Myling’ on the north-west plains of New South Wales (commencing 1996 after 9 years of cultivation). Applications of N and P fertiliser independently influenced both grain P concentration and P removal for a range of summer and winter cereal and legume crops. Generally, if N fertiliser application increased grain yield, the grain P concentration decreased as grain yield increased; however, if grain yield did not respond to N fertiliser, grain P concentration was unaffected. P fertiliser applications typically increased grain P concentration. Wheat and barley grain P concentrations were generally higher in this subtropical region than reported values from temperate regions in Australia. Grain sorghum values were similar to those from subtropical areas overseas, but were greater than reported values from more tropical production zones. Mungbean and chickpea grain P concentrations were consistent with other reported values. Experimental results indicated grain P concentrations for estimating grain P removal in the northern grains region of 3400 mg/kg for sorghum, 3500 mg/kg for wheat and barley, and 4000–4500 mg/kg for mungbean. At both sites, grain P removal was greater with summer and winter cereals than with legume crops. Larger grain yields with N fertiliser application had the largest influence on grain P removal at the Colonsay site, with an additional 23.3 kg P/ha removed from plots with 80 kg N/ha applied compared with nil N over 5 analysed crops from 1998 to 2003. Grain P removal was 20.9, 17.1, and 19.7 kg P/ha in the 3 sorghum crops at this site in this period. Thus, application of P at 10 kg P/ha.crop for this 5-crop study period did not replace P removed. In the predominantly winter-cropped Myling experiment with a shorter duration of cultivation and smaller N fertiliser response, cumulative removal was more influenced by P fertiliser, with 10 kg fertiliser P/ha.crop generally sufficient to provide replacement P. These results support findings of negative P balances recently reported for grain production in this region and suggest a need for further investigation into the implications of a continuing negative P balance on the sustainability of grain production.

Persistence and productivity of Medicago sativa subspecies sativa, caerulea, falcata and varia accessions at three intermittently dry sites in south-eastern Australia

2010 ◽  
Vol 61 (8) ◽  
pp. 645 ◽  
Author(s):  
G. D. Li ◽  
Z. N. Nie ◽  
S. P. Boschma ◽  
B. S. Dear ◽  
G. M. Lodge ◽  
...  
Keyword(s):  
Medicago Sativa ◽  
Total Yield ◽  
Diverse Range ◽  
South Eastern ◽  
The North ◽  
Drought Tolerant ◽  
Eastern Australia ◽  
Grazing Systems ◽  
Perennial Legume ◽  
South Eastern Australia

The persistence and productivity of a diverse range of Medicago sativa germplasm including representatives of subspecies sativa, caerulea, falcata and varia were examined at 3 field sites in south-eastern Australia over 4 years. Sites were located at Tamworth, Barmedman and Hamilton, forming a 1200 km north–south transect with rainfall distribution varying from predominantly summer dominant in the north to winter dominant at the most southerly site. Several entries of subspecies varia and caerulea had herbage yields and persistence equivalent to that of M. sativa subspecies sativa cultivar Sceptre, a highly winter-active type that was used as a standard. The cultivar Cancreep, a cross of M. falcata and M. sativa, had a total yield over 3 years equivalent to 84–91% of Sceptre at the 2 sites where it was sown. Individual lines of subspecies varia demonstrated good persistence under grazing and were ranked 2nd and 6th out of 35 accessions for frequency in year 4 at Barmedman, the driest site, and 5th, 7th and 9th out of 33 accessions at Tamworth, the more summer-dominant rainfall site. Entries of subspecies falcata were among the least productive and persistent. The study indicated that germplasm from subspecies caerulea and varia offered hitherto unexploited potential for selection as persistent and drought-tolerant perennial legume alternatives to M. sativa for extensive low management grazing systems of south-eastern Australia.

Runoff losses from irrigated dairy pastures treated with phosphorus fertilisers of differing solubility in south-eastern Australia

Soil Research ◽  
2011 ◽  
Vol 49 (7) ◽  
pp. 633 ◽  
Author(s):  
A. J. Weatherley ◽  
B. F. Quin ◽  
K. B. Dassanayake ◽  
J. S. Rowarth
Keyword(s):  
Water Soluble ◽  
Current Recommendation ◽  
Single Superphosphate ◽  
North Central ◽  
Quality Guidelines ◽  
Eastern Australia ◽  
Quality Water ◽  
Runoff Losses ◽  
Fertiliser Application ◽  
Irrigation Runoff

In response to increasing concern about environmental quality, water authorities in many countries are imposing legislation limiting phosphorus (P) concentrations in water, which is having an impact on farming practice. This experiment investigated the agronomic effects and runoff losses associated with different forms of P fertiliser applied to an irrigated dairy pasture (soils were Vertic Calcic Red Chromosols; average Olsen P, 50 mg P/kg) in north-central Victoria, Australia. Single superphosphate (SSP), a sulfurised diammonium phosphate, or partially acidulated phosphate rock was surface-applied at 50 kg P/ha in March 2005 to a border-check, flood-irrigated dairy pasture (ryegrass–white clover) ten days before a scheduled irrigation. Dissolved reactive P (DRP) and total P (TP) were measured in runoff from whole bays on one replicate and from microplots on all three replicates for a period of 9 weeks. In all runoff events and all treatments, concentrations of DRP and TP in runoff greatly exceeded water quality guidelines for acceptable limits (0.045 mg P/L). The SSP resulted in significantly higher concentrations of P in runoff than the less water-soluble fertilisers. Even after the fifth irrigation, runoff from all fertilisers still exceeded the control. These results suggest that: (i) P fertilisers should not be applied in high-risk situations as insurance against yield loss; (ii) the current recommendation of withholding irrigation for 3 days after fertiliser application is insufficient to prevent potentially significant losses occurring; and (iii) runoff losses were dependent on the type of fertiliser applied, with a smaller proportion of P applied as sulfurised DAP lost in runoff.

Integrating dual-purpose wheat and canola into high-rainfall livestock systems in south-eastern Australia. 2. Pasture and livestock production

2015 ◽  
Vol 66 (4) ◽  
pp. 377 ◽  
Author(s):  
H. Dove ◽  
J. A. Kirkegaard ◽  
W. M. Kelman ◽  
S. J. Sprague ◽  
S. E. McDonald ◽  
...  
Keyword(s):  
Sheep Grazing ◽  
Dual Purpose ◽  
Winter Canola ◽  
High Rainfall ◽  
South Eastern ◽  
Eastern Australia ◽  
Winter Temperatures ◽  
Grazing Systems ◽  
Livestock Systems ◽  
South Eastern Australia

In south-eastern Australia, low winter temperatures often reduce pasture growth and thus winter herbage supply relative to livestock requirements. Grazing of vegetative grain crops in winter is one strategy that might overcome this feed gap. In a study with young sheep over two seasons near Canberra, ACT, we compared pasture-only grazing with three separate crop–livestock systems in which the sheep grazed long-season wheat, winter canola or a combination of these, for intervals over the period May–August. We measured forage biomass, sheep grazing days (SGD) and liveweight accumulated per ha. Crop-grazing treatments resulted in much more winter forage for grazing sheep (t DM ha–1): in 2010, one crop 2.5–3.0, two crops 3.5 v. pasture only 1; in 2011, one crop 2, two crops 3 v. pasture only 1.4. In the first season, grazing one crop resulted in ~2000 extra SGD ha–1 and the accumulation of more liveweight per ha than in the pasture-only treatment; grazing of two crops resulted in >3500 extra SGD ha–1. Equivalent values in the second, drier season were: one crop, ~1000 extra SGD ha–1; two crops, 2600 extra SGD ha–1. Spelling of pastures during crop grazing led to extra pasture growth, such that in each of the two seasons, 40% of the total benefit in extra SGD per ha came from the extra pasture. The results indicate that, like grazed wheat, grazed canola can provide valuable winter forage, especially when used together with wheat. The data also provide the first quantification of the effect of crop grazing on pasture spelling and subsequent pasture supply, and suggest value in the incorporation of grazing wheat and canola into grazing systems in the high-rainfall zone.

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