Using soil surface temperature to assess soil evaporation in a drip irrigated vineyard
Evaporation from the soil is an important part of the water balance of a crop, when considering water use efficiency. In this paper, a non-intensive method is tested to estimate relative soil evaporation, which is based upon a linear function of soil surface temperature change between a saturated and drying soil. The relative evaporation (RE) method of Ben-Asher et al. (1983) was calibrated using microlysimeters and thermal imaging. Soil surface temperature in a drip irrigated vineyard was then collected using infrared temperature sensors mounted on a quad bike, on several days of the 2009-2010 season. Soil surface temperature in the vineyard ranged from 4.6 °C to 65.5 °C undervine and 6.8 °C to 75.6 °C in the middle of the row. The difference between daily minima and maxima of soil surface temperature ranged from 20.2 °C to 59.7 °C in the inter-row and 13.6 °C to 36.4 °C undervine. Relative evaporation averaged 54% of evaporation from a saturated soil in the inter-row and 97% undervine. Based upon the calculation of RE, the average daily amount of soil evaporation undervine was between 0.64 mm and 1.83 mm, and between 0.69 mm and 2.52 mm inter-row. The soil evaporation undervine and inter-row both exhibited spatial variability across the vineyard, however the undervine area had less spatial variability compared to the inter-row area.
Recent advances in Australian broiler litter utilisation
The global poultry industry is undergoing many changes, one being the need for efficient disposal of its broiler litter (BL) due to a reduction in the land available for cost effective disposal. To date, Australian BL disposal has been achieved by selling the litter as a fertiliser to agricultural sectors. Research indicates BL and other poultry industry waste streams could be used as a food source for vermiculture systems, allowing the sale of vermi-cast as a biologically enhanced fertiliser and worms for protein. If this approach is economically viable then the poultry industry could reduce its environmental impact and operate more like a closed loop system. Integrated bio-systems using vermiculture, composting and waste-to-energy technologies have developed significantly overseas and have shown potential to solve many of the issues associated with poultry waste disposal.
Broiler litter disposal: a summary of advances
The global poultry industry is undergoing many changes, one being the disposal of its broiler litter (BL) due to reduction in land available for cost effective disposal. To date, Australian BL disposal has been achieved by selling the litter as a fertiliser to agricultural sectors. Land availability has decreased due to encroaching urban development, legislative change, decreasing social acceptance, environmental quality issues, and increasing pathogen concerns. Alternative disposal options have developed significantly overseas and have shown potential to solve many of the issues facing BL disposal in Australia. Commercialisation of cornposting, vermiculture, anaerobic digestion and direct combustion for large scale BL disposal is still in its infancy for Australian conditions but has already been achieved overseas.
Use of SIRMOD as a Quasi Real Time Surface Irrigation Decision Support System
Surface irrigation currently accounts for 70-80%of irrigation water use in Australia and surfaceapplication is by far the dominant irrigationmethod applied throughout the world. However,water use efficiencies with surface irrigationmethods tend to be low. In recent years a numberof surface irrigation simulation models forassessing surface irrigation system performancehave been developed. One of the most commonlyused models SIRMOD, developed by Utah StateUniversity, has seen wide use and evaluationthroughout the world particularly by researchersand has been shown to offer potential forincreasing surface irrigation water useefficiencies.Considerable efforts are now being undertaken tomove use of the model from the realm of aresearch domain to the farmer domain. Maximumbenefit from the use of such models will onlyoccur when farmers have the ability to useDecision Support Systems (DSS) such asSIRMOD in a near real time environment i.e. forindividual irrigations.
Long-term management impacts on soil C, N and physical fertility, Part I: Broadbalk experiment
For many centuries manure application to the soil has been common practice. Organic amendments and fertiliser applications can increase crop yields and soil organic matter (SOM). However, the long-term impacts on soil physical fertility are often neglected. This study was carried out on the Broadbalk Wheat Experiment at Rothamsted, UK, established in 1843 on an Aquic/Typic Paleudalf soil. Application of farmyard manure (FYM), N fertiliser and wheat straw on total organic C (CT), labile C (CL) and non-labile C (CNL), total N (NT), mean weight diameter (MWD) and unsaturated hydraulic conductivity (Kunsat) were studied on wheat ('Triticum aestivum') and adjacent woodland and pasture areas. Manure additions, N fertiliser and straw incorporation increased all C fractions, particularly the CL fraction. The addition of 35 t ha⁻1 year⁻¹ of FYM increased CT to 2.5 times that of the control (no fertiliser) treatment and CL to 5 times that of the control. With highest N application and straw returned, CT increased by 1.3 times and CL by 1.5 times that of the control treatment. There were linear relationships between rate of N fertiliser applied and all C fractions, with the rate of increase almost double with straw than straw removed. Manure application improved MWD, as did high N fertiliser additions with straw returned. Application of N fertiliser only increased MWD and Kunsat (at 10 mm tension) if straw was returned, while the addition of manure resulted in decreased Kunsat. The highest Kunsat rate was on the high N fertiliser, straw returned treatments. The uncropped areas all had high soil structural stability. Similar relationships occurred between all C fractions and NT and MWD for the high C soils, but relationships were much stronger with CL than the other C fractions in the low C soils. These results showed that soils with low C concentration are more reliant on CL for structural stability.
Improving Subsurface Drainage Design: Minimising the Environmental Impacts
This paper addresses how the design of subsurface drainage systems impacts on the drainage volume and salinity of drainage water generated. The effects of drain depth and spacing are reviewed and discussed. The conceptualization of a subsurface drainage system which incorporates drainage water quality into the design is presented. This system, known as a Multi-Level Drainage System, aims to minimize offside impacts associated with subsurface drainage while still providing adequate protection from water logging and salinity of the plant root zone. This is achieved through the use of a shallow closely spaced drainage system (0.7m deep at 3.3m) underlain by a deeper, widely spaced drainage system (1.8m deep at 20m). Field investigations show that the shallow drains had approximately five times lower salinity than deep drains, with median values being 5.5 dS/m and 28 dS/m respectively. The results indicate that, by re-thinking subsurface drainage design to incorporate water quality aspects, alternative designs can be formulated which go some way to meet the present day environmental constraints placed on subsurface drainage systems.
Long-term management impacts on soil C, N and physical fertility, Part III: Tamworth crop rotation experiment
Degradation of soil structure can lead to increased risk of run-off and soil erosion, and therefore, it is necessary to implement management practices that are more sustainable and will enhance and rehabilitate soils while increasing food production. The impact of small-grain rotations grown with legumes, fallow and continuously on total C (CT), labile C (CL), non-labile C (CNL), total N (NT), aggregation expressed as mean weight diameter (MWD) and infiltration determined as unsaturated hydraulic conductivity (Kunsat) were examined in a long-term rotation trial established in 1966 on a Black Earth ('Pellic Vertisol') and a Red Clay ('Chromic Vertisol') soil near Tamworth, in New South Wales, Australia. The results were compared with an adjacent uncropped pasture on each soil type. Cropping reduced all C fractions, NT, MWD and Kunsat on both soils, which were further degraded when long fallowing was included in the rotation. CL decreased by 70% with long fallow in the Red Clay and by 78% in the Black Earth compared with the adjacent pasture, whileMWDdecreased by 61% in the Red Clay and 91% in the Black Earth. Rotation of cereals with legumes resulted in smaller decreases in C fractions, NT, MWD and Kunsat when compared with pasture. Rotation with lucerne ('Medicago sativa') resulted in 41% higher CL, 45% higherMWDand 87% higher Kunsat (10 mmtension) than long fallow on the Red Clay soil and 65, 126 and 43% higher on the Black Earth soil. There were strong positive correlations of soil C fractions and NT with MWD for both soil types. Similar significant relationships were found for all C fractions and NT with Kunsat (10mm tension) for the Red Clay soil, but not for the Black Earth. Rotations with forage legumes can limit declines in C fractions, NT, MWD and Kunsat when cropping these soils and has potential to increase soil sustainability.
Soil Spatial Variability Effects on Irrigation Efficiency
Higher evapotranspiration rates, reduced rainfall and increased water scarcity have led to a need for improved irrigation water use efficiency. Evaporation is a significant component of the total evapotranspiration (ET) and high evaporation losses reduce the amount of available water for transpiration, resulting in reduced plant water availability and hence increased irrigation. Values for soil evaporation vary widely in the literature, from 27-65% of total ET. In order to increase transpiration relative to evaporation, a reduction in evaporative losses is needed. Spatial variability of evaporation is an important factor that needs to be taken into consideration when improving water use efficiency. Soil physical properties control evaporation by influencing both the transport of water toward the soil or root surface and soil water storage. The effect of variability in soil properties on evaporation is likely to be larger in cases with water deficiency. Cultural practices such as use of narrow row spacing, mulch and minimum tillage can reduce evaporation however, they are not always effective. The potential for major savings of water depends on the length of drying interval following irrigation or rain. There is the potential for reductions in evaporation losses of up to 60% through the use of improved management techniques, enabling more water to be used by the plant for transpiration. In order to improve water use, more research in quantifying evaporation variability at the field scale needs to be completed.
The role of broiler nutrition in environmental management
As intensive animal industries expand in Australia, so too will the volume of manure that requires disposal in an environmentally responsible way. Broiler nutrition has traditionally been focused on maximising growth and improving feed nutrient utilisation. However consideration is now being given to environmental concerns. The extensive use of organic fertilisers (manures) on Australian soils has contributed to eutrophication of aquatic systems (Nash et al. 2003). Since land application of broiler litter is the primary disposal mechanism, it is in the industries best interest to become more accountable for the nutrients contained in their wastes. Therefore by improving the utilisation of nutrients and reducing their concentrations in the manure, the environmental burden of such wastes will be reduced.
Chemical free disinfection using the fluid disinfection system (FDS)™
This paper describes trials carried out with a disinfection system developed by Packaged Environmental Solutions (F'ES). The trials were carried out at the Woolgoolga Sewage Treatment Plant, which is operated by the Coffs Harbour City Council, in New South Wales. The system uses a heat disinfection system with heat exchange and recovery to minimise operating costs. The disinfection system can handle from 200 L/h to 20,000 L/h, and the current tests were conducted at a rate of about 300 L/h at a temperature of 85 –90°C with a retention time of about two and a half minutes. The unit was positioned after secondary treatment (activated sludge) and filtering (disc filters) and results were also obtained following the standard disinfection by chlorine for comparison. Both faecal coliforms and total coliforms were measured, before and after disinfection. Results indicate that FDS is a viable alternative to conventional disinfection methods for reuse of treated effluent.