Improvement in soil structure resulting from sown pastures on degraded areas in the dry savanna woodlands of northern Australia

Soil Research ◽  
1983 ◽  
Vol 21 (1) ◽  
pp. 83 ◽  
Author(s):  
BJ Bridge ◽  
JJ Mott ◽  
WH Winter ◽  
RJ Hartigan
Keyword(s):  
Soil Structure ◽  
Surface Soil ◽  
Northern Australia ◽  
Wet Season ◽  
Stylosanthes Hamata ◽  
Native Grassland ◽  
Townsville Stylo ◽  
Stocking Rates ◽  
High Infiltration

The structure of the surface soil under pastures sown on a former Themada australis native grassland and on degraded areas in the red earths of northern Australia was examined micromorphologically. Heavily grazed pastures containing the legumes Stylosanthes hamata cv. Verano and Alysicarpus vaginalis had more macropore space in the surface soil than arlightly grazed native grassland, while pastures containing S. humilis (Townsville stylo) had as little macropore space as degraded areas. Macropore space in a S. hamata pasture increased between the third and fourth wet seasons after establishment. Where macropore space was high, infiltration measurements showed that sorptivities were as high as those in the native grassland. Where macropore space was low, sorptivities were as low as those in degraded areas. However, all sown pastures showed low hydraulic conductivities equivalent to those in the degraded areas, and this was attributed to trampling during the wet season under the higher stocking rates involved. The improvement and maintenance of soil structure in the S. hamata and A. vaginalis pastures, together with their high sorptivities, indicates that they are stable in the long term.

scholarly journals Valuing Seasonal Climate Forecasts in the Northern Australia Beef Industry

2020 ◽  
Vol 12 (1) ◽  
pp. 3-14 ◽  
Author(s):  
D. H. Cobon ◽  
R. Darbyshire ◽  
J. Crean ◽  
S. Kodur ◽  
M. Simpson ◽  
...  
Keyword(s):  
Economic Value ◽  
Climatic Conditions ◽  
Environmental Drivers ◽  
Stocking Rate ◽  
Northern Australia ◽  
Wet Season ◽  
Seasonal Climate ◽  
Climate Forecasts ◽  
Stocking Rates ◽  
Seasonal Climate Forecasts

AbstractSeasonal climate forecasts (SCFs) provide opportunities for pastoralists to align production decisions to climatic conditions, as SCFs offer economic value by increasing certainty about future climatic states at decision-making time. Insufficient evidence about the economic value of SCFs was identified as a major factor limiting adoption of SCFs in Australia and abroad. This study examines the value of SCFs to beef production system management in northern Australia by adopting a theoretical probabilistic climate forecast system. Stocking rate decisions in October, before the onset of the wet season, were identified by industry as a key climate sensitive decision. The analysis considered SCF value across economic drivers (steer price in October) and environmental drivers (October pasture availability). A range in forecast value was found ($0–$14 per head) dependent on pasture availability, beef price, and SCF skill. Skillful forecasts of future climate conditions offered little value with medium or high pasture availability, as in these circumstances pastures were rarely overutilized. In contrast, low pasture availability provided conditions for alternative optimal stocking rates and for SCFs to be valuable. Optimal stocking rates under low pasture availability varied the most with climate state (i.e., wet or dry), indicating that producers have more to gain from a skillful SCF at these times. Although the level of pasture availability in October was the major determinant of stocking rate decisions, beef price settings were also found to be important. This analysis provides insights into the potential value of SCFs to extensive beef enterprises and can be used by pastoralists to evaluate the cost benefit of using a SCF in annual management.

The formation of degraded areas in the dry savanna woodlands of northern Australia

Soil Research ◽  
1983 ◽  
Vol 21 (1) ◽  
pp. 91 ◽  
Author(s):  
NK Bridge ◽  
JJ Mott ◽  
RJ Hartigan
Keyword(s):  
Hydraulic Conductivity ◽  
Organic Carbon ◽  
Surface Soil ◽  
Structural Rearrangement ◽  
Northern Australia ◽  
Wet Season ◽  
Structural Collapse ◽  
Tall Grass ◽  
Eucalypt Woodland ◽  
Almost All

The perennial tall grass understory of a eucalypt woodland on a commonly occurring red earth (Northcote Principal Profile Form Gn2.11) in northern Australia was burnt during the dry season and subjected to weekly clipping during the following two wet seasons to simulate overgrazing. Clipping killed many plants during the first wet season and almost all of them during the second. Infiltration measurements showed that sorptivity and hydraulic conductivity were greatly reduced after the first wet season following burning only, and micromorphological examination showed surface sealing and structural collapse. There was recovery of sorptivity after the second wet season, but not of hydraulic conductivity, and this was accompanied by an increase in the macropore space of the upper 5 mm of surface soil. With burning plus clipping, structural rearrangement formed a vesicular porous layer during the second wet season and infiltration rates remained low. Since no organic carbon was lost from the surface soil following burning only, the structural collapse was attributed to raindrop impact rather than loss of structural bonds in the oil. In the burn+clip treatment, organic carbon was lost only during the second wet season when most of the grass tussocks had died. Respiration measurements showed that there was little difference in biological activity between the burnt and unburnt grassland during the first wet season and that an estimated 600 g m-2 year-1 of carbon was respired. Overgrazing pastures on these soils results in complete degradation within two set seasons and the formation of bare areas with surface seals.

scholarly journals Sustainable grazing management for temporal and spatial variability in north Australian rangelands – a synthesis of the latest evidence and recommendations

2014 ◽  
Vol 36 (3) ◽  
pp. 223 ◽  
Author(s):  
Peter O'Reagain ◽  
Joe Scanlan ◽  
Leigh Hunt ◽  
Robyn Cowley ◽  
Dionne Walsh
Keyword(s):  
Key Management ◽  
Rainfall Variability ◽  
Grazing Management ◽  
Economic Modelling ◽  
Infrastructure Development ◽  
Northern Australia ◽  
Wet Season ◽  
Sustainable Grazing ◽  
Patch Burning

Rainfall variability is a major challenge to sustainable grazing management in northern Australia, with management often complicated further by large, spatially-heterogeneous paddocks. This paper presents the latest grazing research and associated bio-economic modelling from northern Australia and assesses the extent to which current recommendations to manage for these issues are supported. Overall, stocking around the safe long-term carrying capacity will maintain land condition and maximise long-term profitability. However, stocking rates should be varied in a risk-averse manner as pasture availability varies between years. Periodic wet-season spelling is also essential to maintain pasture condition and allow recovery of overgrazed areas. Uneven grazing distributions can be partially managed through fencing, providing additional water-points and in some cases patch-burning, although the economics of infrastructure development are extremely context-dependent. Overall, complex multi-paddock grazing systems do not appear justified in northern Australia. Provided the key management principles outlined above are applied in an active, adaptive manner, acceptable economic and environmental outcomes will be achieved irrespective of the grazing system applied.

Herbage and animal production from native pastures and pastures oversown with Stylosanthes hamata. 2. Modelling studies

1993 ◽  
Vol 33 (5) ◽  
pp. 571 ◽  
Author(s):  
MR McCaskill ◽  
JG McIvor
Keyword(s):  
Strong Relationship ◽  
Animal Production ◽  
Wet Season ◽  
Stylosanthes Hamata ◽  
Native Pasture ◽  
Utilisation Rate ◽  
Modelling Studies ◽  
Native Pastures ◽  
The Times ◽  
Stocking Rates

Data from a long-term grazing experiment were used to develop relationships suitable for modelling between-year variation in pasture and animal production. The experiment was conducted near Townsville in North Queensland and consisted of a factorial combination of 2 stocking rates (0.6, 1.2 steers/ha) x 2 pasture types (native pasture, native pasture plus Stylosanthes hamata cv. Verano) x 2 superphosphate rates (nil, 300 kg/ha.year). Cattle were weighed monthly, and the herbage presentation yield and stylo content estimated annually. Relationships between annual liveweight gain (LWG) and a range of climate-derived parameters including the number of 'green days' were calculated from a water balance and pasture growth model. When a different intercept was allowed for each pasture and stocking rate combination, there was a strong relationship between annual LWG and the number of 'green days' (R2 = 0.78). In a more general relationship, LWG was related to green days, stylo content, and utilisation rate (R2 = 0.58). No relationships was found that would enable reliable prediction of between-year variation in the pasture attributes of stylo content and the water use efficiency of herbage growth. The times of the year when daily rates of LWG changed could be predicted satisfactorily, but rate of gain within each phase varied considerably from year to year. Differences in LWG between stocking rates occurred when there would have been restricted amounts of new green feed, or of stylo in the late wet season.

Wet season grazing of Townsville stylo pasture at Katherine, N.T

1970 ◽  
Vol 10 (47) ◽  
pp. 710 ◽  
Author(s):  
MJT Norman ◽  
LJ Phillips
Keyword(s):  
Dry Matter ◽  
Correlation Coefficients ◽  
Dry Matter Yield ◽  
Stocking Rate ◽  
Wet Season ◽  
Nitrogen Yield ◽  
Stylosanthes Humilis ◽  
Townsville Stylo ◽  
Using Data ◽  
Stocking Rates

At Katherine, N.T., stocking rates of 1.33, 1.00, and 0.67 Shorthorn steers an acre for a period of 18 weeks in the wet season beginning January were imposed on established pastures sown to Townsville sty10 (Stylosanthes humilis) alone but subsequently invaded to varying degrees by annual grasses. The experiment was repeated over three years. There were no significant differences in mean liveweight gain per head over three years ; hence liveweight gain per acre at the heaviest stocking rate was approximately twice that at the lightest rate. The mean dry matter yield of grass increased significantly with decreasing stocking rate, but there were no significant differences between stocking rates in Townsville stylo dry matter yield, nitrogen yield, or phosphorus yield. Correlation coefficients were calculated using data from individual paddocks and years. There was a highly significant positive correlation between liveweight gain per head and pasture nitrogen yield, and between liveweight gain per head and pasture phosphorus yield.

Establishment of introduced grasses at different stages of pasture development: effects of seedbed

1981 ◽  
Vol 21 (111) ◽  
pp. 417 ◽  
Author(s):  
JG McIvor ◽  
CJ Gardener
Keyword(s):  
Plant Competition ◽  
Thick Layer ◽  
Soil Surface ◽  
Perennial Grasses ◽  
Wet Season ◽  
Stylosanthes Hamata ◽  
Native Grassland ◽  
Successful Establishment ◽  
Chloris Gayana ◽  
Seedbed Preparation

The seedbed preparation necessary for the successful establishment of five promising perennial grasses for the dry tropics was studied on two pastures - native grassland and a pasture dominated by Stylosanthes hamata cv. Verano - near Townsville, in northern Queensland. Seed of Cenchrus ciliaris cv. Biloela, Chloris gayana cv. Callide, Chrysopogon sp. CPI 5221 3, Digitaria milanjiana CPI 5981 4 and Urochloa mosambicensis CPI 46876 was sown into the two pastures, which had been left untreated, sprayed with herbicide, burnt, or burnt and cultivated. S. hamata cv. Verano was also sown on the native grassland plots. Sowings were made at the start of the growing season in successive years. Germination of all lines was adequate except where a thick layer of green and dead herbage physically separated the seed from the soil surface; this happened on the native pasture plots that were untreated or herbicide treated. However, there was high plant mortality in the first month after sowing except where plant competition had been reduced or removed by cultivation or spraying. After this period, most plants survived to the end of the wet season in both pasture types. This pattern of change in plant numbers resulted in good establishment on the cultivated seedbeds, some establishment on the herbicide-treated plots and little or no establishment on the control and burnt plots. Of the five grasses, U. mosambicensis had the best establishment and Chrysopogon sp. and D. milanjiana the worst. None seem likely to survive when sown into living grassland. We therefore conclude that the use of these introduced species will be largely restricted to completely cleared and cultivated land.

Comparing fixed and flexible stocking as adaptations to inter-annual rainfall variability in the extensive beef industry of northern Australia

2016 ◽  
Vol 38 (1) ◽  
pp. 85 ◽  
Author(s):  
Lester Pahl ◽  
Joe Scanlan ◽  
Giselle Whish ◽  
Robyn Cowley ◽  
Neil MacLeod
Keyword(s):  
Carrying Capacity ◽  
Rainfall Variability ◽  
Full Range ◽  
Herd Size ◽  
Annual Rainfall ◽  
Northern Australia ◽  
Beef Industry ◽  
Growing Seasons ◽  
Stocking Rates

Many beef producers within the extensive cattle industry of northern Australia attempt to maintain a constant herd size from year-to-year (fixed stocking), whereas others adjust stock numbers to varying degrees annually in response to changes in forage supply. The effects of these strategies on pasture condition and cattle productivity cannot easily be assessed by grazing trials. Simulation studies, which include feedbacks of changes to pasture condition on cattle liveweight gain, can extend the results of grazing trials both spatially and temporally. They can compare a large number of strategies, over long periods of time, for a range of climate periods, at locations which differ markedly in climate. This simulation study compared the pasture condition and cattle productivity achieved by fixed stocking at the long-term carrying capacity with that of 55 flexible stocking strategies at 28 locations across Queensland and the Northern Territory. Flexible stocking strategies differed markedly in the degree they increased or decreased cattle stocking rates after good and poor pasture growing seasons, respectively. The 28 locations covered the full range in average annual rainfall and inter-annual rainfall variability experienced across northern Australia. Constrained flexibility, which limited increases in stocking rates after good growing seasons to 10% but decreased them by up to 20% after poor growing seasons, provides sustainable productivity gains for cattle producers in northern Australia. This strategy can improve pasture condition and increase cattle productivity relative to fixed stocking at the long-term carrying capacity, and its capacity to do this was greatest in the semiarid rangeland regions that contain the majority of beef cattle in northern Australia. More flexible stocking strategies, which also increased stocking rates after good growing seasons by only half as much as they decreased them after poor growing seasons, were equally sustainable and more productive than constrained flexibility, but are often impractical at property and industry scales. Strategies with the highest limits (e.g. 70%) for both annual increases and decreases in stocking rates could achieve higher cattle productivity, but this was at the expense of pasture condition and was not sustainable. Constrained flexible stocking, with a 10% limit for increases and a 20% limit for decreases in stocking rates annually, is a risk-averse adaptation to high and unpredictable rainfall variability for the extensive beef industry of northern Australia.

scholarly journals Managing for rainfall variability: effect of grazing strategy on cattle production in a dry tropical savanna

2009 ◽  
Vol 49 (2) ◽  
pp. 85 ◽  
Author(s):  
Peter O'Reagain ◽  
John Bushell ◽  
Chris Holloway ◽  
Angela Reid
Keyword(s):  
Southern Oscillation ◽  
Rainfall Variability ◽  
Cattle Production ◽  
Long Term Effects ◽  
Seasonal Forecasts ◽  
Wet Season ◽  
Variable Environment ◽  
Condition Score ◽  
Stocking Rates

Rainfall variability is a challenge to sustainable and profitable cattle production in northern Australia. Strategies recommended to manage for rainfall variability, like light or variable stocking, are not widely adopted. This is due partly to the perception that sustainability and profitability are incompatible. A large, long-term grazing trial was initiated in 1997 in north Queensland, Australia, to test the effect of different grazing strategies on cattle production. These strategies are: (i) constant light stocking (LSR) at long-term carrying capacity (LTCC); (ii) constant heavy stocking (HSR) at twice LTCC; (iii) rotational wet-season spelling (R/Spell) at 1.5 LTCC; (iv) variable stocking (VAR), with stocking rates adjusted in May based on available pasture; and (v) a Southern Oscillation Index (SOI) variable strategy, with stocking rates adjusted in November, based on available pasture and SOI seasonal forecasts. Animal performance varied markedly over the 10 years for which data is presented, due to pronounced differences in rainfall and pasture availability. Nonetheless, lighter stocking at or about LTCC consistently gave the best individual liveweight gain (LWG), condition score and skeletal growth; mean LWG per annum was thus highest in the LSR (113 kg), intermediate in the R/Spell (104 kg) and lowest in the HSR (86 kg). Mean LWG was 106 kg in the VAR and 103 kg in the SOI but, in all years, the relative performance of these strategies was dependent upon the stocking rate applied. After 2 years on the trial, steers from lightly stocked strategies were 60–100 kg heavier and received appreciable carcass price premiums at the meatworks compared to those under heavy stocking. In contrast, LWG per unit area was greatest at stocking rates of about twice LTCC; mean LWG/ha was thus greatest in the HSR (21 kg/ha), but this strategy required drought feeding in four of the 10 years and was unsustainable. Although LWG/ha was lower in the LSR (mean 14 kg/ha), or in strategies that reduced stocking rates in dry years like the VAR (mean 18 kg/ha) and SOI (mean 17 kg/ha), these strategies did not require drought feeding and appeared sustainable. The R/Spell strategy (mean 104 kg/ha) was compromised by an ill-timed fire, but also performed satisfactorily. The present results provide important evidence challenging the assumption that sustainable management in a variable environment is unprofitable. Further research is required to fully quantify the long-term effects of these strategies on land condition and profitability and to extrapolate the results to breeder performance at the property level.

scholarly journals Resting Subtropical Grasslands from Grazing in the Wet Season Boosts Biocrust Hotspots to Improve Soil Health

Agronomy ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 62
Author(s):  
Wendy J. Williams ◽  
Susanne Schmidt ◽  
Eli Zaady ◽  
Bruce Alchin ◽  
Than Myint Swe ◽  
...  
Keyword(s):  
Best Practice ◽  
Rainfall Variability ◽  
Soil Health ◽  
Extreme Rainfall ◽  
Wet Season ◽  
Ecosystem Integrity ◽  
Landscape Function ◽  
Eastern Australia ◽  
Stocking Rates

Effective grazing management in Australia’s semi-arid rangelands requires monitoring landscape conditions and identifying sustainable and productive practice through understanding the interactions of environmental factors and management of soil health. Challenges include extreme rainfall variability, intensifying drought, and inherently nutrient-poor soils. We investigated the impacts of grazing strategies on landscape function—specifically soil health—as the foundation for productive pastures, integrating the heterogenous nature of grass tussocks and the interspaces that naturally exist in between them. At Wambiana—a long-term research site in north-eastern Australia—we studied two soil types, two stocking rates (high, moderate), and resting land from grazing during wet seasons (rotational spelling). Rotational spelling had the highest biocrust (living soil cover), in interspaces and under grass tussocks. Biocrusts were dominated by cyanobacteria that binds soil particles, reduces erosion, sequesters carbon, fixes nitrogen, and improves soil fertility. Rotational spelling with a moderate stocking rate emerged as best practice at these sites, with adjustment of stocking rates in line with rainfall and soil type recommended. In drought-prone environments, monitoring the presence and integrity of biocrusts connects landscape function and soil health. Biocrusts that protect and enrich the soil will support long-term ecosystem integrity and economic profitability of cattle production in rangelands.

Evaluation of management options for increasing the productivity of tropical savanna pastures. 2. Legume species

1989 ◽  
Vol 29 (5) ◽  
pp. 623 ◽  
Author(s):  
WH Winter ◽  
JJ Mott ◽  
RW McLean
Keyword(s):  
Perennial Grasses ◽  
Legume Species ◽  
Forage Production ◽  
Wet Season ◽  
Management Options ◽  
Stylosanthes Humilis ◽  
Northwestern Australia ◽  
Animal Growth ◽  
Townsville Stylo ◽  
Stocking Rates

The effect of legume species, used for augmentation of native perennial grasses, upon forage production and quality and animal production was studied over 4 vears in the semi-arid troPics of northwestern Australia. The legumes were Stylosanthes humilis cv. Paterson (Townsville stylo), S. hamata cv. Verano (Caribbean stylo) and a mixture of perennial species S. scabra cvv. Fitzroy and Seca and S. viscosa (perennial stylo). They were compared at 2 levels of fertility, unfertilised (UF) and with small inputs of superphosphate (F); and at stocking rates of 0.45,0.6 and 0.75 steers/ha for UF and 0.6, 0.8 and 1.0 steers/ha for F. By 1980 only half of the 3 x 12 treatments persisted, 3 Townsville stylo, 9 Caribbean stylo and 6 perennial stylo. Without fertiliser the perennial stylos had the highest wet season yields of 1-2 t/ha which constituted 4040% of pasture yield, compared with 2-20% for the other legumes. Caribbean stylo yields were highest with fertiliser, yielding 2-4 t/ha and 50-90% of the pasture at the end of the wet season, compared with 60-70% for perennial stylo and 5-30% for Townsville stylo. Anthracnose devastated Townsville stylo, and also reduced the productivity of Fitzroy. The perennial stylos had the highest concentrations of nitrogen (N), phosphorus (P), and sulfur (S) during the dry season while Caribbean stylo and its associated grasses had the lowest P and S concentrations during the wet season. When annual liveweight gains for each legume were compared at the same stocking rate-fertiliser level, differences were less than 15 kg, but there were considerable differences in the patterns of growth within the year; these differences were related to the seasonal availability and relative palatability of grass and legume. The overall mediocre animal growth of 30-110 kg/steer.year was attributed to the inadequate supply of nutrients for most of the year, with the possible exception of N.

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