Surface soil water dynamics in pastures in northern New South Wales. 3. Evapotranspiration

2004 ◽  
Vol 44 (6) ◽  
pp. 571 ◽  
Author(s):  
S. R. Murphy ◽  
G. M. Lodge ◽  
S. Harden
Keyword(s):  
Soil Water ◽  
New South ◽  
New South Wales ◽  
Ground Cover ◽  
Bare Soil ◽  
Soil Evaporation ◽  
Grazing Management ◽  
South Wales ◽  
Bare Soil Evaporation ◽  
Daily Evapotranspiration

Evapotranspiration is the major component of the hydrological balance of grazed pastures on the North-West Slopes of New South Wales, representing up to 93% of annual rainfall. Nearly 80% of evapotranspiration may occur as bare soil evaporation, however, representing water not available for plant growth. Few studies have reported daily values of actual evapotranspiration for pastures, particularly in northern New South Wales. The studies reported here were conducted to measure actual evapotranspiration using an evaporation dome technique, for plots with a range of pasture, litter and ground cover. Measurements were taken in each season between autumn 2000 and autumn 2001, with both wet and dry soil surface conditions, to document the range of values that might be expected. Similar measurements were conducted in areas of natural pasture, to quantify values under grazed conditions. A range of other variables were also quantified in association with each evapotranspiration measurement; these included components of net radiant energy, atmospheric conditions, pasture physical characteristics, ground cover and soil water content. These data were used to identify the most important variables, which may be influenced by or interact with grazing management, that account for variation in daily evapotranspiration values.Hourly evapotranspiration ranged from 0.02 to 0.82 mm/h and daily values ranged from 0.2 to 7.6 mm/day, in winter to summer, respectively. Linear regression models that included variables of solar radiation, herbage mass, vapour pressure deficit and soil water content accounted for up to 93% of the variation in daily evapotranspiration values. These models predicted that high litter mass (3000 kg DM/ha) may reduce evaporation by up to 1 mm/day for wet soils, making a substantial contribution to the annual hydrological balance. A simulation study of a grazed pasture, using the Sustainable Grazing Systems Pasture Model, indicated that grazing management may influence the partitioning of transpiration and evaporation from canopy, litter and bare soil. With rotational grazing, predicted soil evaporation was lower and transpiration and canopy evaporation were higher than with continuous grazing. Hence, pastures may require different management between summer and winter, so that bare soil evaporation and canopy interception losses are minimised, to maximise stored soil water available for pasture use. Pastures with lower evaporative losses are likely to have higher productivity and sustainability.

Sustainable grazing systems for the Central Tablelands of New South Wales. 4. Soil water dynamics and runoff events for differently-managed pasture types

2006 ◽  
Vol 46 (4) ◽  
pp. 483 ◽  
Author(s):  
J. D. Hughes ◽  
I. J. Packer ◽  
D. L. Michalk ◽  
P. M. Dowling ◽  
W. McG. King ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Soil Water ◽  
New South ◽  
New South Wales ◽  
Ground Cover ◽  
Environmental Data ◽  
Quality Data ◽  
Water Runoff ◽  
South Wales ◽  
Management Factors

Soil water, runoff amount and quality, pasture production and environmental data were measured for a pastoral prime lamb enterprise in the Central Tablelands of New South Wales from 1998 to 2002. There were 4 pasture treatments: fertilised and sown chicory (CH), fertilised and sown introduced pastures (SP), fertilised naturalised pastures (FN) and unfertilised naturalised pastures (UN). Two grazing management regimes, tactically grazed (TG) and continuously grazed (CG) were imposed on the SP, FN and UN treatments. The CH treatment was rotationally grazed. To compare pasture and grazing system water use, maximum soil water deficit values (SWDMax) were calculated from neutron moisture meter data. SWDMax was influenced by both environmental and management factors. Management factors that influenced SWDMax were herbage mass of perennials, degree of perenniality, and the perennial species present. Environmental factors accounted for >50% of the variation in SWDMax. Inclusion of management factors (perennial herbage mass of C3 and C4 species and percentage perennial herbage mass), accounted for an additional 16% of variation. While the influence of pasture management appears to be relatively small, importantly, management is the only avenue available to land managers for influencing SWDMax. The UNTG and all sown treatments, with greater perennial herbage mass or greater C4 herbage mass consistently produced the highest SWDMax. Runoff amount and quality data are presented for ground cover percentages which generally exceeded 80% for the experimental period. Runoff as a proportion of rain received during the experiment was <3%. Environmental factors explained 47% of variation in runoff, while pasture herbage mass and ground cover percentage explained an additional 2% of variation. Water quality was monitored on 3 treatments (SPTG, FNTG and UNCG) for total nitrogen (N), total phosphorus (P) and total suspended solids (TST) over a 6-month period. The mean values for total N and P were below the acceptable contaminant concentration for agricultural irrigation water. An important outcome of this research is the concept of a practical Targeted Water Management Plan (TWMP) which devises a framework for optimum water usage and productivity at a landscape scale.

The impact of rabbits on a grazing system in eastern New South Wales.1. Ground cover and pastures

2002 ◽  
Vol 42 (7) ◽  
pp. 909 ◽  
Author(s):  
J. D. Croft ◽  
P. J. S. Fleming ◽  
R. van de Ven
Keyword(s):  
New South ◽  
New South Wales ◽  
Subterranean Clover ◽  
Ground Cover ◽  
Bare Soil ◽  
South Wales ◽  
Pasture Degradation ◽  
The Impact ◽  
The Relationship ◽  
Density Treatment

Although there have been a number of studies that have examined the effects of rabbits on pasture, the relationship between rabbit density and pasture degradation caused by rabbits has never been quantified. An experiment was conducted at Cowra, New South Wales, from October 1984 to October 1987, to determine the impact various densities of rabbits have on pasture composition, indices of pasture biomass and ground cover. Using plots set stocked with the equivalent of 8 sheep/ha (the district average) and 4 densities of rabbits as treatments, 0,�24, 48 and 72 rabbits/ha, the consequences of rabbit grazing were investigated.Pasture composition changed with season, year and rabbit density. Cumulative effects were also evident. Rabbits severely depleted improved pastures of legumes (subterranean clover particularly), with grass cover increasing proportionate to rabbit density. In the final year of the experiment, the rabbit-free treatment had 31% legumes and 25.2% grasses, whereas the highest rabbit density treatment had 6.2% legumes and 47.4% grasses. Indices of pasture biomass were highest in the zero rabbits/ha treatment and lowest in the 72 rabbits/ha treatment. More bare soil was exposed in the highest rabbit density treatment. Once seasonal and year effects were accounted for, the relationship between rabbit density and percentage damage was positive.

Effects of logging and fire on small mammals in Mumbulla State Forest, near Bega, New South Wales

1987 ◽  
Vol 14 (2) ◽  
pp. 163 ◽  
Author(s):  
D. Lunney ◽  
B. Cullis ◽  
P. Eby
Keyword(s):  
Small Mammals ◽  
New South ◽  
New South Wales ◽  
Canopy Cover ◽  
Ground Cover ◽  
First Year ◽  
Severe Effect ◽  
South Wales ◽  
Antechinus Stuartii ◽  
Rattus Fuscipes

This study of the effects of logging on small mammals in Mumbulla State Forest on the south coast of New South Wales included the effects of a fire in November 1980 and a drought throughout the study period from June 1980 to June 1983. Rattus fuscipes was sensitive to change: logging had a significant impact on its numbers, response to ground cover, and recapture rate; fire had a more severe effect, and drought retarded the post-fire recovery of the population. The three species of dasyurid marsupials differed markedly in their response to ground cover, canopy cover, logging and fire. Antechinus stuartii was distributed evenly through all habitats and was not affected by logging, but fire had an immediate and adverse effect which was sustained by the intense drought. A. swainsonii markedly preferred the regenerating forest, and was not seen again after the fire, the failure of the population being attributed to its dependence on dense ground cover. Sminthopsis leucopus was found in low numbers, appeared to prefer forest with sparse ground cover, and showed no immediate response to logging or fire; its disappearance by the third year post-fire suggests that regenerating forest is inimical to the survival of this species. Mus musculus showed no response to logging. In the first year following the fire its numbers were still very low, but in the next year there was a short-lived plague which coincided with the only respite in the 3-year drought and, importantly, occurred in the intensely burnt parts of the forest. The options for managing this forest for the conservation of small mammals include minimising fire, retaining unlogged forest, extending the time over which alternate coupes are logged and minimising disturbance from heavy machinery.

Surface soil water dynamics in pastures in northern New South Wales. 2. Surface runoff

2004 ◽  
Vol 44 (3) ◽  
pp. 283 ◽  
Author(s):  
S. R. Murphy ◽  
G. M. Lodge ◽  
S. Harden
Keyword(s):  
Soil Water ◽  
Surface Runoff ◽  
New South ◽  
Ground Cover ◽  
Simulation Modelling ◽  
Runoff Generation ◽  
Grazed Pastures ◽  
South Wales ◽  
Runoff Events

Surface runoff can represent a significant part of the hydrological balance of grazed pastures on the north-west slopes of New South Wales, and is influenced by a range of rainfall characteristic, soil property, and pasture conditions. Runoff plots were established on grazed pastures at 3 sites as part of the Sustainable Grazing Systems National Experiment (SGS NE). Pastures were either native (redgrass, wallaby grass and wire grass) or sown species (phalaris, subterranean clover and lucerne) and a range of grazing management treatments were imposed to manipulate pasture herbage mass, litter mass and ground cover. Rainfall and runoff events were recorded using automatic data loggers between January 1998 and September 2001. Stored soil water in the surface layer (0–22.5 cm) was monitored continuously using electrical resistance sensors and automatic loggers. Pasture herbage mass, litter mass and ground cover were estimated regularly to provide information useful in interpreting runoff generation processes.Total runoff ranged from 6.6 mm at Manilla (0.3% of rainfall) to 185 mm at Nundle (5.7% of rainfall) for different grazing treatments, with the largest runoff event being recorded at Nundle (46.7 mm). Combined site linear regression analyses showed that soil depth, rainfall depth and rainfall duration explained up to 30.3% of the variation in runoff depth. For individual sites, these same variables were also important, accounting for 13.3–33.6% of the variation in runoff depth. Continuous monitoring of stored soil water in relation to these runoff events indicated that the majority of these events were generated by saturation excess, with major events in winter contributing substantially to regional flooding. Long-term simulation modelling (1957–2001) using the SGS Pasture Model indicated that most runoff events were generated in summer, which concurred with the number of flood events recorded at Gunnedah, NSW, downstream of the SGS sites. However, floods also occurred frequently in winter, but the simulations generated few runoff events at that time of the year. These results have important implications for sustainability of grazed pastures and long-term simulation modelling of the hydrological balance of such systems, since runoff generation processes are likely to vary both spatially and temporally for different rainfall events.

Response of oats to seeding rate and nitrogen in the southern wheat belt of New South Wales

1974 ◽  
Vol 14 (67) ◽  
pp. 231 ◽  
Author(s):  
OR Southwood ◽  
F Mengersen ◽  
PJ Milham
Keyword(s):  
Nitrate Nitrogen ◽  
New South ◽  
Nitrogen Concentration ◽  
New South Wales ◽  
Fertilizer Application ◽  
Grazing Management ◽  
Grain Production ◽  
Seeding Rate ◽  
South Wales ◽  
Oat Cultivars

The effect of three rates of nitrogen (22.4, 44.8 and 89.6 kgNha-1 as anhydrous ammonia) and three seeding rates (67.3, 100.9, and 134.5 kg ha-1) on forage and grain production of two oat cultivars and on herbage nitrate-nitrogen concentration, was assessed at three sites in the southern New South Wales wheat belt. When oats were sown after two or three consecutive wheat crops nitrogen at 22.4 kg ha-1 was optimal for both forage and grain production. Herbage growth was best at the highest seeding rate (134.5 kg ha-1) but grain production was not influenced by seeding rate. Herbage growth of the oat cultivars Cooba and Coolabah was similar, but grain yields were higher from the latter. Herbage nitrate nitrogen increased linearly with nitrogen fertilizer application, levels that could be toxic to animals occurring in June. Cautious grazing management may be required during this period.

Establishing surface-sown pastures in a Poa labillardieri-Themeda australis association

1986 ◽  
Vol 26 (3) ◽  
pp. 331 ◽  
Author(s):  
MH Campbell ◽  
MJ Keys ◽  
RD Murison ◽  
JJ Dellow
Keyword(s):  
Festuca Arundinacea ◽  
New South ◽  
New South Wales ◽  
Ground Cover ◽  
Cost Effective ◽  
Phalaris Aquatica ◽  
South Wales ◽  
Before And After

The effects of time and rate of application of glyphosate, 2,2-DPA and tetrapion on Poa labillardieri and Themeda australis were measured in seven experiments carried out 55 km south of Braidwood, on the southern tablelands of New South Wales between 1980 and 1982. In an eighth experiment (1981) and in a 35-ha demonstration (1983), at the same site, the effects of applying herbicides (before and after the autumn break) and surface-sowing Phalaris aquatica, Festuca arundinacea and Trifiolium repens with fertiliser on the control of P. labillardieri were ascertained. All three herbicides proved effective in reducing the ground cover of P. labillardieri from applications at any time of the year. For T. australis, tetrapion proved effective when applied at any time of the year, while glyphosate and 2,2-DPA were effective in all seasons except winter. Glyphosate at rates between 0.72 and 1.44 kg/ha a.i. was more cost effective than 2,2-DPA (11.1 kg/ha a.i.) and tetrapion (3.75 kg/ha a.i.). Best establishment and development of sown grasses and legumes was attained by applying herbicides after the autumn break but before heavy frosts, and then surface-sowing 1-3 months later. Control of P. labillardieri was best where P. aquatica and F. arundinacea established most densely.

Fire studies in Mallee (Eucalyptus spp.) communities of western New South Wales: spatial and temporal fluxes in soil chemistry and soil biology following prescribed fire

1995 ◽  
Vol 2 (4) ◽  
pp. 398 ◽  
Author(s):  
J. C. Noble ◽  
D. J. Tongway ◽  
M. M. Roper ◽  
W. G. Whitford
Keyword(s):  
Electrical Conductivity ◽  
Soil Chemistry ◽  
Nitrogenase Activity ◽  
New South ◽  
New South Wales ◽  
Bare Soil ◽  
Soil Samples ◽  
Soil Biology ◽  
South Wales ◽  
Micro Organisms

The effects of prescribed fires on nutrient pools, soil micro-organisms, and vegetation patch dynamics were studied in three semi-arid mallee shrublands in western New South Wales. Repeated sampling of surface soil strata (0–2 and 2–4 cm) was undertaken at strategic times (immediately before and after the fire, after opening autumn rain, mid-season in the winter, and at the end of the spring) in five microsites (inner, middle and outer mallee litter zones, bare soil, and Triodia hummock). These samples were later analysed for pH, electrical conductivity, organic carbon and available nitrogen. The effect of fire on soil micro-organisms in these microsites was also examined by measuring nitrogenase activity and enumerating soil Acari. Carbon and nitrogen levels were consistently higher in the inner mallee microsites whereas bare soil sites provided the lowest values. Significant microsite x soil depth interactions were recorded in two shrubland sites while highly significant (P < 0.001) depth x sampling time interactions were recorded in three sites. The most sensitive soil parameter with respect to microsite was electrical conductivity, particularly in the surface 0–2 cm stratum. Highest values were again recorded from the inner mallee microsites and the lowest from bare soil sites. Nitrogenase activity was highest in soil samples associated with mallee litter and, where litter was removed by fire, activity decreased markedly except in the bare soil samples where activity was higher in the burnt samples. Soil microarthropod populations also declined notably following fire. Mites from the Prostigmata greatly outnumbered those from other suborders, a total of 12 families (15 genera) being enumerated in control sites compared with three families (three genera) only of Cryptostigmata. Nonetheless the most abundant mites were cryptostigmatids (Aphelacarus spp.) found in unburnt hummocks beneath Triodia plants. The ecological and management implications of these spatial and temporal fluxes in soil chemistry and soil biology are discussed in relation to their effects on landscape processes, particularly water and nutrient redistribution.

Sustainable grazing systems for the Central Tablelands of New South Wales. 5. A bioeconomic framework for assessing the long-term economic benefits of grazing management tactics and implications for sustainability

2006 ◽  
Vol 46 (4) ◽  
pp. 495 ◽  
Author(s):  
R. E. Jones ◽  
P. M. Dowling ◽  
D. L. Michalk ◽  
W. McG. King
Keyword(s):  
Programming Model ◽  
New South ◽  
New South Wales ◽  
Economic Benefits ◽  
Grazing Management ◽  
South Wales ◽  
Grazing Systems ◽  
Sustainable Grazing ◽  
Management Tactics

There have been significant declines in the perennial grass (PG) content in native and sown pastures across temperate Australia. Not only has this reduced agricultural productivity, it has contributed to more serious degradation, such as loss of soil and biodiversity, decreasing water quality, and dryland salinity caused by rising watertables. Results from the Sustainable Grazing Systems Key Program (SGS) research undertaken at Carcoar on the Central Tablelands of New South Wales were reported by Michalk et al. (2003). This research indicated that grazing management tactics can be used to manipulate pasture composition, thereby changing animal production and water-use patterns. The main grazing tactic investigated was termed a summer grazing rest, where resting was imposed in late spring if PG composition was <50%. Reported in this present paper is an economic framework for valuing the long-term benefits of grazing management tactics. The framework involves the development of a bioeconomic modelling system that links a dynamic programming model with biophysical models for water and environmental processes, soil fertility, pasture growth, livestock energy requirements and the change in pasture species composition. The study concludes that long-term economic returns are improved by strategies, e.g. a summer rest, that lead to an increase in PG composition over time. The study also determined that environmental factors, such as deep drainage, runoff and soil loss, are reduced as perenniality is increased.

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