Academic literature on the topic 'Soil salinization – New South Wales – Coleambally'

Irrigation farmers in the Murray–Darling Basin of Australia are under considerable pressure to reduce the amount of water they use for irrigation, while sustaining production and profitability. Changing from surface to pressurised irrigation systems may provide some or all of these outcomes; however, little is known about the performance of alternative irrigation methods for broadacre annual crops in this region. Therefore, a demonstration site for comparing furrow, subsurface drip and sprinkler irrigation was established on a representative clay soil in the Coleambally Irrigation Area, NSW. The performance of maize (Zea mays L.) under the three irrigation systems was compared during the 2004–05 season. Subsurface drip irrigated maize out-performed sprinkler and furrow irrigated maize in terms of grain yield (drip 11.8 t/ha, sprinkler 10.5 t/ha, furrow 10.1 t/ha at 14% moisture), net irrigation water application (drip 5.1 ML/ha, sprinkler 6.2 ML/ha, furrow 5.3 ML/ha), net irrigation water productivity (drip 2.3 t/ML, sprinkler 1.7 t/ML, furrow 1.9 t/ML) and total water productivity (drip 1.7 t/ML, sprinkler 1.4 t/ML, furrow 1.3 t/ML). Thus, subsurface drip irrigation saved ~30% of the total amount of water (irrigation, rain, soil water) needed to produce the same quantity of grain using furrow irrigation, while sprinkler irrigation saved ~8% of the water used. The higher net irrigation with sprinkler irrigation was largely due to the lower soil water content in the sprinkler block at the time of sowing. An EM31 survey indicated considerable spatial soil variability within each irrigation block, and all irrigation systems had spatially variable water distribution. Yield variability was very high within all irrigation systems, and appeared to be more strongly associated with irrigation variability than soil variability. All irrigation blocks had large patches of early senescence and poor cob fill, which appeared to be due to nitrogen and/or water deficit stress. We expect that crop performance under all irrigation systems can be improved by improving irrigation, soil and N management.

Soils affected by secondary salinization were studied in six areas on the Southern Tablelands of New South Wales. All the salt-affected areas are underlain by, or occur in close proximity to, deeply weathered volcanic, granitic and sedimentary rocks which commonly contain stores of soluble salts, dominantly sodium chloride. The chemical composition of shallow groundwaters in the areas was monitored by piezometers for periods of up to two years. Water levels in the piezometers responded rapidly to rainfall, but the ionic composition of the waters generally remained fairly uniform. All waters are dominated by sodium chloride; those with the highest contents occurred in volcanic and granitic rocks, followed by Ordovician sediments and the lowest contents were in Silurian sediments. The chlorine contents in samples of weathered rocks follow a similar sequence. Electron microprobe analyses indicate that the chlorine-bearing minerals in the unaltered rocks are principally biotite, hornblende and potassium, sodium and calcium feldspars. No salt-affected soils were found in areas underlain by unweathered rocks.

Presowing nitrogen (N) fertiliser management for aerial-sown rice was investigated for 2 soil cultivation methods, conventional cultivation and puddling, in the Coleambally Irrigation Area of New South Wales. Two N sources, urea and anhydrous ammonia (NH3, ColdFlo), were used. Urea was applied at 3 depths (0,7, 17 cm) and NH3 at 2 depths (7, 17 cm). These 5 treatments were compared with an unfertilised control and with a novel method of applying NH3 in the same operation as puddling. Urea was applied at 60 kg N/ha; the application rate of NH3 appeared to be higher than the intended rate of 60 kg N/ha. The site was responsive to N: agronomic efficiency of the urea-fertilised treatments averaged 39 kg grain yield increase/kg applied N. Dry matter yield, N uptake, and grain yield were similar on conventionally cultivated and puddled soil. There were no significant interactions between cultivation and N treatments in their effects on crop growth or N uptake. Application depth of fertiliser also had no significant effect on crop performance. Applying NH3 in the same operation as puddling was as effective as other methods of applying N, with the advantage of allowing soil preparation and fertiliser application to be completed in 1 pass. Urea labelled with 15N was applied at depths of 0, 5, and 15 cm to microplots at a rate of 60 kg N/ha. Recoveries of 15N in plants and soil were similar for both methods of soil cultivation and for different N application depths, consistent with results from the large plots described above. There was no interaction between soil cultivation and urea application depth treatments. Recovery of applied 14N averaged 32% in the plant shoots and 24% in the top 30 cm of the soil. Recoveries of 15N from presowing urea application have not previously been reported for aerial-sown rice in New South Wales. The results suggest that puddling can be readily integrated into the rice management system without changing current fertiliser practices. However, soil N uptake was very high, accounting for around 90% of the plant N uptake in the urea-fertilised treatments. Therefore, extrapolation of the results of the treatment comparisons to other sites with lower available N should only be done with caution.

Using an environmentally adjusted performance measurement the study evaluates the tradeoffs between the benefits derived from irrigated cotton enterprises and its associated environmental damages. Deep drainage, which adds to the aquifer recharge and thereby contributes to salinization, is treated as an environmentally detrimental output. The analysis includes data collected from a sample of 53 observations in the Mooki Catchment located in northern New South Wales, Australia. Environmentally adjusted efficiency of cotton enterprises is estimated using the environmental performance index (EPI) and relative efficiency rankings are determined for each of the considered cotton areas in the catchment. The findings reveal that environmentally adjusted efficiency of irrigated cotton is within an acceptable range (more than 60% of observations have an EPI efficiency score of greater than 5). The efficiency variation among the observations based on hydrological response units (HRUs) can be attributed to a number of reasons including physical factors (i.e., soil quality, topography), type of irrigation technology used, and other environmental factors. For instance, the overall efficiencies of downstream HRUs are higher than that of upstream HRUs. Therefore, biophysical characteristics of an area need to be incorporated in the efficiency model. With the identification of the most and least efficient cotton irrigation areas in the region, policymakers can construct a relative ranking to best determine policy directions in order to take a more targeted approach towards salinity mitigation.

To remain economically and environmentally sustainable, Australian rice growers need to be able to readily respond to market opportunities and increase cropping system productivity and water productivity. Water availability is decreasing whereas its price is increasing. Alternative irrigation layouts and water management approaches could contribute to reduced water use and increased irrigation efficiency. This paper reports results for the first crop (rice) in a cropping system experiment to compare permanent raised bed and conventional layouts on a transitional red-brown earth at Coleambally, New South Wales. The performance of conventional ponded rice grown on a flat layout was compared with rice grown on 1.84-m wide, raised beds with furrow and subsurface drip irrigation. In addition, deep and shallow ponded water depth treatments (15 and 5 cm water depth over the beds) were imposed on the rice on beds during the reproductive period. A range of nitrogen (N) fertiliser rates (0–180 kg N/ha) was applied to all treatments. The traditional flat flooded treatment (Flat) achieved the highest grain yield of 12.7 t/ha, followed by the deep (Bed 15) and shallow (Bed 5) ponded beds (10.2 and 10.1 t/ha, respectively). The furrow (Furrow) irrigated bed treatment yielded 9.4 t/ha and the furrow/drip (Furr/Drip) treatment yielded the lowest grain yield (8.3 t/ha). Grain yield from all bed treatments was reduced owing to the wide furrows (0.8 m between edge rows on adjacent beds), which were not planted to rice. Rice crop water use was significantly different between the layout–irrigation treatments. The Flat, Bed 5 and Bed 15 treatments had similar input (irrigation + rainfall – surface drainage) water use (mean of 18.3 ML/ha). The water use for the Furrow treatment was 17.2 ML/ha and for the Furr/Drip treatment, 15.1 ML/ha. Input WP of the Flat treatment (0.68 t/ML) was higher than the raised bed treatments, which were all similar (mean 0.55 t/ML). This single season experiment shows that high yielding rice crops can be successfully grown on raised beds, but when beds are ponded after panicle initiation, there is no water saving compared with rice grown on a conventional flat layout. Preliminary recommendations for the growing of rice on raised beds are that the crop be grown as a flooded crop in a bankless channel layout. This assists with weed control and allows flooding for cold temperature protection, which is necessary with current varieties. Until we find effective herbicides and other methods of weed control and N application that do not require ponding, there is little scope for saving water while maintaining yield on suitable rice soil through the use of beds.

Spicers Creek catchment is located approximately 400 km west of Sydney in the Central West region of New South Wales, Australia. Dryland salinity has been recognised as a major environmental issue impacting soil and water resources in the Central West region of NSW for over 70 years. Due to the geological complexity of the catchment and the presence of high salt loads contained within the soils, groundwater and surface waters, the Spicers Creek catchment was identified as a large contributor of salinity to the Macquarie River catchment. Over fifty-two dryland salinity occurrences have been identified in the Spicers Creek catchment and it appears that dryland salinity is controlled by the presence of geological structures and permeability contrasts in the shallow aquifer system. Combinations of climatic, geological and agricultural factors are escalating salinity problems in the catchment. The main aim of this thesis was to identify the factors affecting salinisation processes in the Spicers Creek catchment. These include the role of geological structures, the source(s) of salts to the groundwater system and the geochemical processes influencing seepage zone development. To achieve these aims a multidisciplinary approach was untaken to understand the soils, geology, hydrogeology and hydrogeochemistry of the catchment. Investigative techniques employed in this project include the use of geophysics, soil chemistry, soil spectroscopy, hydrogeochemistry and environmental isotopes. Evaluation of high-resolution airborne magnetics data showed a major north-east to south-west trending shear zone. This structure dissects the catchment and several other minor faults were observed to be splays off this major structure. These structures were found to be conducive to groundwater flow and are influencing the groundwater chemistry in the fractured aquifer system. Two distinctive groundwater chemical types were identified in the catchment; the saline Na(Mg)-Cl-rich groundwaters associated with the fractured Oakdale Formation and the Na-HCO3-rich groundwaters associated with the intermediate groundwater system. The groundwater chemistry of other deep groundwaters in the catchment appears to be due to mixing between these end-member groundwaters within the fractured bedrock system. The spatial distribution of electrical conductivity, Cl-, Sr2+ and 87Sr/86Sr isotopic ratios showed the correlation between saline groundwaters and the location of faults. Elevated salinities were associated with the location of two crosscutting fault zones. The spatial distribution of HCO3-, K+, Li+ and ?????3CDIC highlighted the extent of Na-HCO3-rich groundwaters in the catchment and showed that these groundwaters are mixing further east than previously envisaged. These findings show that Na(Mg)-Cl-rich groundwaters are geochemically distinctive and have evolved due to extensive water-rock interaction processes within the fracture zones of the Oakdale Formation. These saline groundwaters contain elevated concentrations of trace elements such as As, V and Se, which pose a potential risk for water resources in the area. 87Sr/86Sr isotopic ratios indicated that the source of salinity to the Na(Mg)-Cl-rich groundwaters was not purely from marine or aerosol input. Salt is most likely contributed from various allochthonous and autochthonous sources. This research found that the main mechanism controlling the formation of dryland salinity seepage zones in the Spicers Creek catchment is due to the presence of geological structures. These groundwater seepage zones act as mixing zones for rainfall recharge and deeper groundwaters. The main sources of salt to the seepage zones are from deeper Na(Mg)-Cl-rich groundwaters and rainfall accession. The major importance of this research highlights the need for an integrated approach for the use of various geoscientific techniques in dryland salinity research within geologically complex environments.

Salinisation of the shallow groundwater system has occurred coincident with the development of irrigation in the Coleambally Irrigation Area. Salinisation in irrigation areas has previously been attributed to the evaporative concentration of the water table; however, there are other sources of salt such as the accumulation of rainfall by vegetation and the dry deposition of salt-laden dusts. A significant store of crystalline gypsum, together with high concentrations of Na, Mg and Confidence limit, was found within the previously unsaturated zone of the Upper Shepparton Formation. The salt store was identified both within and outside of the groundwater mound; therefore evaporative concentration of the water table cannot be the source of salt. The transition from regional groundwater quality, as applied as irrigation to the ground surface, to shallow groundwater quality is simply explained by solubilisation of this salt store in the presence of soil CO2. Dating of basal palaeochannel sands indicates that the identified salt store, a profile of only 20 m, was accumulated during the last glacial cycle. Radiocarbon dating indicates that the peak in eluate salinity, at approximately 2 m below ground surface, is between 15,000 and 25,000 years old, coincident with the Last Glacial Maximum. The Last Glacial Maximum was a period of significantly enhanced aridity on the Australian continent. It was also found that the peak in eluate salinity coincided with a bi-modal particle size distribution. The bi-modal signature implies that these sediments were subject to the aeolian accession of dusts. It was found that the contribution of salt from dry deposition of dusts exceeded the contribution from rainfall by at least 1.9 to 11 times during the last glacial cycle. The results of this study imply that salt-laden dusts have, and continue to play an important role in the salinity and sodicity of soils in the Coleambally Irrigation Area and beyond.