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Overcoming constraints that poorly structured lowland rice-growing soils of the Lower Mekong River Basin present for growing non-rice crops during the dry season would have a significant positive impact on the livelihood of smallholder farmers. This study investigated whether the use of soil organic amendments, bed architecture (conventional, flat and narrow) and water application methods (sprinkler, furrow and over-bed irrigation) could improve plant water availability in typical rice-growing soils of Cambodia and Laos by either improving the movement of water into beds or the growth of the root system. Five experiments were conducted over two dry seasons on peanut and maize grown in a bed/furrow system. Organic amendments assessed were rice straw, cow/goat manure, biochar, manure plus rice straw and biochar plus manure. Results showed that compared with conventional bed/furrow design, narrowing beds increased soil moisture availability for peanut, whilst higher grain yield and water productivity were achieved with sprinkler irrigation than furrow irrigation. Placing a layer of sub-surface straw within beds did not consistently enhance soil moisture or improve root development. The study showed that maize grown on soil amended with biochar plus cow manure under a furrow irrigation system and on rice straw under sprinkler irrigation produced yields above the average yield that models have simulated for maize grown on these soils. These findings present opportunities to enhance maize production on lowland soils across Cambodia and Laos. The contrary was observed for peanut production, which indicates that factors other than water might be detrimentally affecting crop yields.

Incorporation of dry-season crops in the lowland production systems of the Lower Mekong Basin (LMB) may provide local smallholder farmers the opportunity to increase household cash income through diversification. However, water availability and lowland rice-growing soil characteristics often limit the yield potential of dry-season crops in rotation with wet-season rice. This work studied the effects of three frequencies of irrigation on the crop performance of dry-season furrow-irrigated maize (Zea mays Linnaeus) and peanut (Arachis hypogaea Linnaeus) grown on lowland rice-growing soils in terms of biomass, yield and water productivity (WP). In addition, the response of maize to two fertiliser rates was evaluated. The study was carried out in sites with typical lowland rice-growing soils located in Cambodia and Laos. Soil matric potential (&Psi, m) was monitored during the season at the centre of the beds and percentage of canopy cover, aboveground biomass (AGB), yield and WP were determined. The results showed that within the first weeks of furrow irrigation (~two weeks after emergence), &Psi, m dropped considerably (&lt, &minus, 200 kPa) after all treatments at both sites, suggesting that water movement from the furrows to the centre of the beds was limited. Shorter frequency of irrigation led to significantly (p &lt, 0.05) higher AGB and yield in maize but not in peanut. Fertiliser rates did not have a significant effect on maize. WP ranged from 0.84 kg m&minus, 3 to 1.42 kg m&minus, 3 for maize and from 0.27 kg m&minus, 3 to 0.49 kg m&minus, 3 for peanut with no significant differences among treatments. This work provides evidence of a lateral water movement limitation that is not well documented for the establishment of furrow-irrigated dry-season crop production in the lowlands of the LMB. Further research on methodologies that could help to overcome this limitation in these soils, such as the application of soil amendments or implementation of alternative irrigation systems, would be of great value.

Agricultural soils are a major source of nitrous oxide (N2O) emissions and an understanding of factors regulating such emissions across contrasting soil types is critical for improved estimation through modelling and mitigation of N2O. In this study we investigated the role of soil texture and its interaction with plants in regulating the N2O fluxes in agricultural systems. A measurement system that combined weighing lysimeters with automated chambers was used to directly compare continuously measured surface N2O fluxes, leaching losses of water and nitrogen and evapotranspiration in three contrasting soils types of the Riverine Plain, NSW, Australia. The soils comprised a deep sand, a loam and a clay loam with and without the presence of wheat plants. All soils were under the same fertilizer management and irrigation was applied according to plant water requirements. In fallow soils, texture significantly affected N2O emissions in the order clay loam > loam > sand. However, when planted, the difference in N2O emissions among the three soils types became less pronounced. Nitrous oxide emissions were 6.2 and 2.4 times higher from fallow clay loam and loam cores, respectively, compared with cores planted with wheat. This is considered to be due to plant uptake of water and nitrogen which resulted in reduced amounts of soil water and available nitrogen, and therefore less favourable soil conditions for denitrification. The effect of plants on N2O emissions was not apparent in the coarse textured sandy soil probably because of aerobic soil conditions, likely caused by low water holding capacity and rapid drainage irrespective of plant presence resulting in reduced denitrification activity. More than 90% of N2O emissions were derived from denitrification in the fine-textured clay loam-determined for a two week period using K15NO3 fertilizer. The proportion of N2O that was not derived from K15NO3 was higher in the coarse-textured sand and loam, which may have been derived from soil N through nitrification or denitrification of mineralized N. Water filled pore space was a poorer predictor of N2O emissions compared with volumetric water content because of variable bulk density among soil types. The data may better inform the calibration of greenhouse gas prediction models as soil texture is one of the primary factors that explain spatial variation in N2O emissions by regulating soil oxygen. Defining the significance of N2O emissions between planted and fallow soils may enable improved yield scaled N2O emission assessment, water and nitrogen scheduling in the pre-watering phase during early crop establishment and within rotations of irrigated arable cropping systems.

Practical solutions to optimise nitrogen use efficiency within modern surface irrigated cotton systems in Australia may be possible by regulating the frequency of water and reducing the N applied, compared with typical current practises. A two-year study examined the effect of irrigating at three different water deficits that applied a similar total irrigation volume: >−60 kPa (HF), between −80 and −100 kPa (IF) and between −100 and −120 kPa (LF) for a period from initial flowering throughout boll development, in combination with different nitrogen fertiliser rates on the growth, yield, nitrogen use efficiency and lint quality of cotton. It was hypothesised that shorter deficits would increase N uptake, and nitrogen use efficiency compared with longer deficits caused by consistently higher soil water potentials in the root zone. The major effects of irrigation treatment on growth was to increase plant height and number of bolls, delay crop maturity and decrease micronaire. The irrigation strategy according to yield was most consistently optimised over both seasons when soil matric potential was maintained between −80 and −100 kPa (IF treatment). Lint yield was reduced by 9–13% when the irrigation deficit was

Irrigated agriculture may contribute as much as two-thirds to future global food demand because of the high intensity of production that it offers. However, it also has relatively high fertilizer and water inputs and therefore, N 2 O emissions. This study examined how varying the volume of individual irrigation events could mitigate N 2 O emissions from irrigated grain sorghum in Australia. To maintain productivity, the applied water amount was kept constant over an entire growing season. Treatments included irrigation water applications of 120 mm (3 applications), 90 mm (4 applications), 60 mm (6 applications) and 30 mm (12 applications). A custom-designed automated chamber-weighing lysimeter system was used to measure soil N 2 O fluxes, leaching losses and evapotranspiration simultaneously. The cumulative seasonal N 2 O emissions (kg N 2 O-N ha −1 season −1 ) were greatest in the 120 mm (1.71 ± 0.70) and 90 mm (1.81 ± 0.39) treatments and least in the 30 mm (0.88 ± 0.21) treatment. Irrigation management had a significant ( p ≤ 0.001) effect on reducing N 2 O emissions by avoiding the high magnitude N 2 O pulses that are measured following larger irrigation applications. The losses of water through leaching decreased from 41 ± 1% in the 120 mm treatment to 12 ± 4% in the 30 mm treatment while mineral-N losses decreased from 20% in the 120 mm to 3% in the 30 mm treatment. Plant N uptake in the 30 mm and the 60 mm treatments was significantly ( p ≤ 0.05) higher than for the 120 mm treatment. The increase in plant N-uptake and decrease in leaching losses of N in frequent irrigations of ≤90 mm compared with 120 mm irrigations suggests improvements in crop nitrogen use efficiency and potential for productivity gains.

A new agricultural sensor data logging platform (WiField) is described, based on IEEE 802.11 WiFi technology. It is low-cost, low-power, and achieves long (>2km) range communication to on-farm WiFi access points. WiFi is an attractive choice for this application because of the wide range of other devices that increasingly need internet access in farming systems. The WiField devices include interfaces for many sensor types; weather, infrastructure (tank and irrigation water levels), and soil status sensing. The interfaces and example corresponding sensors include SDI-12 (capacitive soil moisture probes), soil tension (matric potential), analog voltage and current, UART (water depth sensing using ultrasonic transducers with a digital interface), RS-422 (integrated weather stations), one-wire (DS18B20 temperature sensors) and pulse (flow meters, wind and rain sensors). It integrates solar charging of rechargeable batteries, or can be run off disposable batteries for at least an entire growing season due to design choices that minimize power consumption. It is designed to upload data to cloud services in real-time. The data is then processed in the cloud and interactive graphs are produced, so multiple users can access up-to-date information in order to make optimized, timely farming decisions. The use of the WiField devices in a cotton farming operation is described, for scheduling irrigations and determining crop water use through the soil profile.

The present work assessed the usefulness of a set of spectral indices obtained from an unmanned aerial system (UAS) for tracking spatial and temporal variability of nitrogen (N) status as well as for predicting lint yield in a commercial cotton (Gossypium hirsutum L.) farm. Organic, inorganic and a combination of both types of fertilizers were used to provide a range of eight N rates from 0 to 340 kg N ha−1. Multi-spectral images (reflectance in the blue, green, red, red edge and near infrared bands) were acquired on seven days throughout the season, from 62 to 169 days after sowing (DAS), and data were used to compute structure- and chlorophyll-sensitive vegetation indices (VIs). Above-ground plant biomass was sampled at first flower, first cracked boll and maturity and total plant N concentration (N%) and N uptake determined. Lint yield was determined at harvest and the relationships with the VIs explored. Results showed that differences in plant N% and N uptake between treatments increased as the season progressed. Early in the season, when fertilizer applications can still have an effect on lint yield, the simplified canopy chlorophyll content index (SCCCI) was the index that best explained the variation in N uptake and plant N% between treatments. Around first cracked boll and maturity, the linear regression obtained for the relationships between the VIs and both plant N% and N uptake was statistically significant, with the highest r2 values obtained at maturity. The normalized difference red edge (NDRE) index, and SCCCI were generally the indices that best distinguished the treatments according to the N uptake and total plant N%. Treatments with the highest N rates (from 307 to 340 kg N ha−1) had lower normalized difference vegetation index (NDVI) than treatments with 0 and 130 kg N ha−1 at the first measurement day (62 DAS), suggesting that factors other than fertilization N rate affected plant growth at this early stage of the crop. This fact affected the earliest date at which the structure-sensitive indices NDVI and the visible atmospherically resistant index (VARI) enabled yield prediction (97 DAS). A statistically significant linear regression was obtained for the relationships between SCCCI and NDRE with lint yield at 83 DAS. Overall, this study shows the practicality of using an UAS to monitor the spatial and temporal variability of cotton N status in commercial farms. It also illustrates the challenges of using multi-spectral information for fertilization recommendation in cotton at early stages of the crop.

The 5-day biological oxygen demand (BOD5) remains a key indicator for proof of compliance with environmental regulators in the monitoring and management of winery effluent. Inter-conversion factors from alternative tests that are more rapid, accurate and simpler to perform have been determined that allow prediction of BOD5 in winery wastewaters, generally, and at different stages of production and treatment. Mean values obtained from this dataset offer rule of thumb inter-conversion factors: BOD5 = 0.7 Chemical Oxygen Demand (COD), BOD5 = 2.3 Total Organic Carbon (TOC) and BOD5 = 2.7 Dissolved Organic Carbon (DOC). Specific predictive linear relationships are also provided. Out of the relationships between BOD5vs COD, TOC and DOC, in winery wastewater, irrespective of vintage or non-vintage production periods and stage of treatment, TOC offered the most reliable prediction of BOD5. Ethanol, glucose and fructose were evaluated in untreated wastewater as predictors of BOD5 due to their high specificity in winery effluent. A significant relationship was determined between BOD5 and (ethanol + glucose + fructose; R2 = 0.64, n = 19; p < 0.05), but relationships between BOD5 and ethanol and BOD5vs (glucose + fructose) were weak (R2 = 0.45 and 0.34; n = 19; p < 0.05 respectively,). There was a very strong linear correlation (y = 0.9767x + 52.8; R2 = 0.97; n = 23; p < 0.05) in COD data in winery effluents when using a commercially available mercury free test kit compared with using a traditional COD test kit that contained mercury. This suggests that mercury free COD test kits could be used by the wine industry for organic pollution assessment with associated reductions to user and environmental risk, as well as reducing the costs of kit waste disposal.

The relative effects of Na + and K + on soil structural stability are not clearly defined by the existing literature. This is an important issue for the application of winery wastewater on soils as it contains high levels of K + and varying levels of Na + . To evaluate the relative effects of Na + and K + on soil structural stability both surface and subsoil from a land application site for winery wastewater were used to assess changes in soil hydraulic conductivity in repacked soil columns. The soil was rich of smectite, 51–56%, with minor presence of illite, 5–8%, and kaolinite 10% clays. Solutions with sodium adsorption ratio (SAR) and potassium adsorption ratio (PAR) of 5–40, where the monovalent cation was Na + or K + and the divalent cation was Ca 2 + or Mg 2 + were used to leach the soil columns, at electrolyte concentrations ranging from 2.5 to 640 meq L − 1 . In both surface and subsoil, percolating solutions with PAR or SAR, comprising all cation combinations, of 20 and 40 caused a decrease in hydraulic conductivity as electrolyte concentrations reduced. However, in PAR solutions the decreases in hydraulic conductivity were significantly smaller than the corresponding SAR solutions. These results indicated greater soil stability in the presence of K + relative to Na + .

Rapid and inexpensive phytotoxicity bioassays for winery wastewater (WW) are important when designing winery wastewater treatment systems involving constructed wetlands. Three macrophyte wetland species (Phragmites australis, Schoenoplectus validus and Juncus ingens) were tested using a pot experiment simulating a wetland microcosm. The winery wastewater concentration was varied (0.5%, 5%, 10%, 25%, 50%, 75% and 100%) and pH was corrected for some concentrations using lime as an amendment. The tolerance of the three aquatic macrophytes species to winery wastewater was studied through biomass production, total chlorophyll and nitrogen, phosphorous and potassium tissue concentrations. The results showed that at greater than 25% wastewater concentration all the macrophytes died and that Phragmites was the least hardy species. At less than 25% wastewater concentration the wetland microcosms were effective in reducing chemical oxygen demand, phenols and total soluble solids. We also evaluated the performance of two laboratory phytotoxicity assays; (1) Garden Cress (Lepidium sativum), and (2) Onion (Allium coepa). The results of these tests revealed that the effluent was highly toxic with effective concentration, EC(50), inhibition values, as low as 0.25%. Liming the WW increased the EC(50) by 10 fold. Comparing the cress and onion bioassays with the wetland microcosm results indicated that the thresholds for toxicity were of the same order of magnitude. As such we suggest that the onion and cress bioassays could be effectively used in the wine industry for rapid wastewater toxicity assessment.

The fate of benzofenap [2-[4-(2,4-dicholoro-m-toluoyl)-1,3-dimethylpyrazol-5-yloxy]-4'-methylacetophenone] applied to flooded rice was studied at two locations in New South Wales (Australia). Solid-phase extraction (SPE) was compared with liquid-liquid extraction (LLE) for the determination of the commercial chemical in water samples. SPE performed well as compared to LLE (84 vs 80%) in irrigation waters. However, at the lower end of the concentration range (3 microg/L), LLE achieved higher recoveries than SPE (72 vs 59%). Rates of dissipation (DT50) from floodwaters and soils were measured. Dissipation of the herbicide from water and soil occurred fairly erratically in both mediums and can be best explained by a first-order decay process. The DT50 value for benzofenap was

The contamination of drainage channels and creeks with pesticides used in the production of rice is of concern in south eastern Australia. Of major concern is the molinate that at times has been detected in over 25% of water samples from surface drains and creeks. The objective of this study was to evaluate the rice pesticide model RICEWQ version 1.7.2 for its applicability in simulating the fate of the pesticide molinate in paddy rice floodwater in south eastern Australia. The model was successfully calibrated using water depths and molinate concentrations obtained from a rice bay. By using the calibrated model, the effects of the different application methods and the rates of molinate on water quality were investigated. The molinate, which was applied directly onto ponded water, led to higher maximum concentrations in the ponded water than for application onto a dry bay, which was subsequently filled. However, the concentrations in water declined more rapidly for the application onto a ponded bay than those for the application onto a dry bay. The simulation results suggest that water and chemical management has great effects on chemical concentration in the runoff water. Overall, the RICEWQ model accurately predicted the molinate concentrations in floodwater and this model can be used to develop best management practices in rice farming.

The fates of clomazone [2-(2-chlorophenyl)methyl-4,4-dimethyl-3-isoxazolidinone], molinate (S-ethyl hexahydro-1-H-azepine-1-carbothioate), and thiobencarb {S-[(4-chlorophenyl)methyl]diethylcarbamothioate} applied to rice were studied at two locations in New South Wales (Australia). Rates of dissipation (DT50) from floodwaters and soils were measured. Dissipation of the three herbicides from water and soil can be best explained by a first-order decay process. DT(50) values for clomazone, molinate, and thiobencarb were 7.2, 5.1, and 3.5 days, respectively, in water and 14.6, 23.9, and46 days, respectively, in surface soil. Maximum measured concentrations of clomazone, molinate, and thiobencarb in floodwaters were 202, 1042, and 148 microg/L, respectively, taking 18.4, 26.4, and 21.4 days to dissipate to concentrations set to protect aquatic ecosystems. A hazard assessment identified clomazone as presenting a low environmental hazard while molinate and thiobencarb presented a medium environmental hazard when used at registered field rates.

The molecular weight distributions and hydrolysable neutral sugar composition of dissolved organic carbon (DOC) was investigated in four maritime Antarctic lakes on Signy Island of different trophic status; Heywood Lake (eutrophic), Light Lake (oligo-mesotrophic), Sombre Lake and Moss Lake (both oligotrophic). Tangential flow ultra-filtration (TFU) was used to separate DOC into high molecular weight (HMW; >1000 Da) and low molecular weight (LMW; 1000 Da total organic carbon and had extremely high concentrations of total hydrolysable neutral sugars (11 μM) corresponding to 43% of total DOC. However, no clear pattern was apparent with regard to lake trophic status and potential sources of DOC, and the measured variations in individual aldose concentration, composition and their various molecular weight fractions.

SUMMARY 1. Bacterioplankton production was measured in the water columns of two ultraoligotrophic, freshwater Antarctic lakes (Crooked Lake and Lake Druzhby) during an annual cycle. In both lakes bacterial production, measured by the incorporation of [ 3 H] thymidine, continued in winter and showed a cycle over the year. The range of production was between 0 and 479 ng C L )1 h )1 in Crooked Lake and 0–354 ng L )1 h )1 in Lake Druzhby. 2. Abundance and mean cell volume both varied, producing marked changes in biomass during the year, with highest biomass occurring in the winter and early spring. Biomass showed similar seasonal trends in both lakes. 3. For most of the year inorganic forms of nitrogen and phosphorus were detectable in the water columns of the lakes and were unlikely to have limited bacterial production. Dissolved organic carbon (DOC) was below 3000 l gL )1 . Dissolved amino acids and carbohydrates contributed 5–25% of the DOC pool in Crooked Lake and 5–64% in Lake Druzhby. Dissolved carbohydrates were consistently low, suggesting that this may have been the preferred carbon substrate for bacterioplankton. 4. Aggregate associated bacteria had higher mean cell volume, abundances and production than freely suspended bacteria in Lake Druzhby, while in Crooked Lake aggregate associated bacteria consistently had higher mean cell volumes than free bacteria, but abundance and production were on occasion higher in free bacteria compared with aggregate associated communities. 5. The data indicated that production is limited by continuous low temperatures and the limited availability of suitable DOC substrate. However, the bacterioplankton functions year round, responding to factors other than temperature.

Five brackish to hypersaline lakes (Highway, Ace, Pendent, Williams and Rookery) in the Vestfold Hills, eastern Antarctica were investigated during the austral summer of 1999/2000. The aims were to characterise the functional dynamics of the plankton and gain an understanding of how the different environments in the lakes have led to the evolution of different communities. The plankton was dominated by microorganisms and differed across the salinity spectrum in relation to trophy, age and the presence of meromixis. However, some elements of the plankton were common to all of the lakes, e.g. the mixtrophic ciliate, Mesodinium rubrum, which reached abundances of 2.7×105 l–1 and spanned a salinity gradient of 4–63‰. Marine dinoflagellate species also occurred in all of the lakes, often at high abundances in Highway Lake, Pendent Lake and Lake Williams. During December (mid-summer), primary production showed an increase along the salinity gradient from Highway Lake to Lake Williams; however, it was low in hyper-nutrified Rookery Lake because of the turbidity of the waters. Bacterial production followed the same trend and was extremely high in Rookery Lake (327 µg l–1 h–1 in January). The lakes possessed a marine microbial plankton that has become very simplified through time, and now contains a small number of highly successful species, which were pre-adapted to surviving in extreme Antarctic lakes.

1. Beaver Lake, a large epishelf lake in eastern Antarctica was sampled on two occasions during the austral summer of 2000. Two sites, one 1 km offshore and another 6 km offshore were sampled at intervals to depths of 40 and 110 m, respectively. 2. The lake is an end member of ultra-oligotrophic lake systems with a very low carbon pool. Dissolved organic carbon concentrations ranged between 95 and 652 lg L±1. Nutrient levels were generally low with soluble reactive phosphorus ranging from undetectable to 8.4 lg L±1, ammonium ranged between 1.8 and 5.0 lg L±1, nitrate from undetectable to 161 lg L±1 and nitrite 1.1±5.3 lg L±1. 3. Chlorophyll a concentrations (0.39±4.38 lg L±1) showed an unusual distribution with the highest levels close to the lake bottom at the offshore site (110 m) where the phototrophic nano¯agellates (PNAN) displayed strong auto¯uorescence. 4. Bacterial concentrations were low, with a maximum of 7.60 ´ 107 L±1, as were the concentrations of heterotrophic nano¯agellates that exploit them. 5. Primary production ranged between 19.7 and 25.49 lg C L±1 day±1 and bacterial production from 0.32 to 1.15 lg C L±1 day±1. 6. In common with other continental Antarctic lakes, the system was dominated by a microbial plankton. However, a dwarf variety of the calanoid copepod, Boeckella poppei, occurred below 25 m at concentrations of 3±5 L±1. 7. The data suggest that primary production and bacterial production were not limited by nutrient availability, but by other factors, e.g. in the case of bacterial production by organic carbon concentrations and primary production by low temperatures.

A method is described for the simultaneous determination of sixteen organochlorine pesticides in drinking water using automated solid-phase extraction followed by high-volume (80 μl) injection capillary column gas chromatography using electron capture detection. The fully automated extraction method followed by high-volume injection permits rapid sample analysis compared to previously described procedures since no further pre-concentration of the analytes is necessary after they have been eluted from the octadecyl solid-phase extraction cartridge. The lowest detectable concentrations of the pesticides are between 1–5 ng l −1 , relative recoveries range from 92–105% in tap water spiked at 100 ng l −1 and the relative standard deviations are in the range 5–12%.

Polar lakes act as key early detectors of global change effects. Duration and thickness of snow and ice cover determines albedo, underwater light availability, thermal and chemical regimes and mixing properties. However, quantitative data on responses by aquatic systems to regional-scale change remain scant. Here, by utilizing 48 year (1947-1995) air temperature and 33 year (1963-1996) lake environmental datasets obtained at Signy Island, South Orkney Islands, we report one of the fastest responses to regional climate change so far documented in the southern hemisphere. Between 1980-1995 lake water temperatures increased by 2-3 times the local air temperature rise. Autumn freeze and spring break up dates of lake ice have changed, extending the open water period by up to 4 weeks. Winter total extractable phytopigments, alkalinity and orthophosphate show 2- to 10-fold increases, all linked with an areal reduction of the island's ice cover of similar to 45% in total in the last 50 years. These results indicate that its geographical position allows Signy Island to be a sensitive indicator of rapid ecological change in Antarctic freshwater environments. Such rapid change will be widespread in polar regions if current global change predictions are correct.

Effects of soil solution cation concentrations and ratios on hydraulic properties must be understood in order to model soil water flow in reactive soils or develop guidelines for sustainable land application of wastewater. We examined effects of different ratios and concentrations of the cations Ca2+, Mg2+, Na+, and K+, using hydraulic conductivity measurements in repacked soil cores, as an indicator of soil structural stability. We examined widely used indices—sodium, potassium, and monovalent cation absorption ratios (SAR, PAR, MCAR)—which assume that the flocculating effects of Ca2+ and Mg2+ are the same, and the dispersive effects of Na+ and K+ are the same. Our laboratory measurements indicate that at any given values of MCAR, the reductions in soil hydraulic conductivity with decrease in electrolyte concentration are not identical for different cation combinations in solution. The hydraulic conductivity curves showed a marked lateral shifting for both the surface and subsurface soils from a winery wastewater application site. This indicates that MCAR is inadequate as a soil stability parameter in soil solutions containing a mixture of Na+, K+, Ca2+, and Mg2+. We employed an unpublished equation that was proposed by P. Rengasamy as a modified index of soil stability for mixed cation combinations, using calculated relative flocculating powers of different cations (‘CROSS’, cation ratio of structural stability). Our observation of lateral shift in hydraulic conductivity measurements at any value of MCAR appears to relate to changes in CROSS values for all cation combinations tested, except for K–Mg solutions, for which a more generalised CROSS equation with modified parameters seems more suitable for calculating the CROSS value. Appropriate modified parameters for use in this generalised CROSS equation were determined empirically, using the experimental data. We derived a combination of threshold electrolyte concentration and CROSS values required to maintain high hydraulic conductivity for the soils at a winery wastewater application site. The potential use of this relationship in developing management practices for sustainable wastewater management at the site is discussed. Further research on the applicability of CROSS and generalised CROSS equations for other soils in the presence of different mixed cation combinations is needed.

This study outlines a new approach to the treatment of winery wastewater by application to a land FILTER (Filtration and Irrigated cropping for Land Treatment and Effluent Reuse) system. The land FILTER system was tested at a medium size rural winery crushing approximately 20,000 tonnes of grapes. The approach consisted of a preliminary treatment through a coarse screening and settling in treatment ponds, followed by application to the land FILTER planted to pasture. The land FILTER system efficiently dealt with variable volumes and nutrient loads in the wastewater. It was operated to minimize pollutant loads in the treated water (subsurface drainage) and provide adequate leaching to manage salt in the soil profile. The land FILTER system was effective in neutralizing the pH of the wastewater and removing nutrient pollutants to meet EPA discharge limits. However, suspended solids (SS) and biological oxygen demand (BOD) levels in the subsurface drainage waters slightly exceeded EPA limits for discharge. The high organic content in the wastewater initially caused some soil blockage and impeded drainage in the land FILTER site. This was addressed by reducing the hydraulic loading rate to allow increased soil drying between wastewater irrigations. The analysis of soil characteristics after the application of wastewater found that there was some potassium accumulation in the profile but sodium and nutrients decreased after wastewater application. Thus, the wastewater application and provision of subsurface drainage ensured adequate leaching, and so was adequate to avoid the risk of soil salinisation.

Irrigation with wastewaters from agri-industry processes such as milk factories, piggeries, wineries and abattoirs is commonplace. These wastewaters all have high levels of potassium (K). Potassium concentration in effluents from domestic wastewater sources are relatively low, reported to vary between 10 and 30 mg L(-1). Higher levels of potassium are reported for effluents from olive oil mills, 10,000-20,000 mg KL(-1), wool scouring, 4200-13,000 mg KL(-1), cheese and lactic whey and potato processing, approximately 1800 mg KL(-1), piggery effluent, 500-1000 mg KL(-1) and winery wastewaters, up to 1000 mg KL(-1). Application of wastewaters with these high potassium levels has been found to increase the overall level of soil fertility, with the exception of alkaline effluents which can dissolve soil organic carbon. Long-term application of such wastewater may cause the build-up of soil potassium and decrease the hydraulic conductivity of the receiving soils. These potential impacts are uncertain and have been inadequately researched. Regulatory limits for potassium in drinking water have been set only by the European Union with no toxicological or physiological justification. The literature shows that grasses and legume herbages accumulate high levels of potassium, up to 5% dry weight, and some grasses, such as turfgrass are particularly tolerant to high levels of potassium, even under saline conditions. This adaptation is considered useful for increasing potassium immobilization and sustainable practices of land wastewater disposal. Potassium availability is significantly affected by the cation ratios of the wastewater, the existing soil water solution and of soil exchange sites.

Soils under irrigated agriculture are a significant source of nitrous oxide (N2O) owing to high inputs of nitrogen (N) fertiliser and water. This study investigated the potential for N2O mitigation by manipulating the soil moisture deficit through irrigation scheduling in combination with, and in comparison to, using the nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP). Lysimeter cores planted with wheat were fitted with automated chambers for continuous measurements of N2O fluxes. Treatments included conventional irrigation (CONV), reduced deficit irrigation (RED), CONV-DMPP and RED-DMPP. The total seasonal volume of irrigation water applied was constant for all treatments but the timing and quantity in individual irrigation applications varied among treatments. 15N-labelled urea was used to track the source of N2O emissions and plant N uptake. The majority of N2O emissions occurred immediately after irrigations began on 1 September 2014. Applying RED and DMPP individually slightly decreased N2O emissions but when applied in combination (RED-DMPP) the greatest reductions in N2O emissions were observed. There was no effect of treatments on plant N uptake, 15N recovery or yield possibly because the system was not N limited. Half of the plant N and 53% to 87% of N2O was derived from non-fertiliser sources in soil, highlighting the opportunity to further exploit this valuable N pool.