Steven R. Raine

Mapping and analysis of changes in the riparian landscape structure of the Lockyer Valley catchment, Queensland, Australia

[Abstract]: A case study of the Lockyer Valley catchment in Queensland, Australia, was conducted to develop appropriate mapping and assessment techniques to quantify the nature and magnitude of riparian landscape structural changes within a catchment. The study employed digital image processing techniques to produce land cover maps from the 1973 and 1997 Landsat imagery. Fixed and variable width buffering of streams were implemented using a geographic information system (GIS) to estimate the riparian zone and to subsequently calculate the landscape patterns using the Patch Analyst (Grid) program (a FRAGSTATS interface). The nature of vegetation clearing was characterised based on land tenure, slope and stream order. Using the Pearson chi-square test and Cramer’s V statistic, the relationships between the vegetation clearing and land tenure were further assessed. The results show the significant decrease in woody vegetation areas mainly due to conversion to pasture. Riparian vegetation corridors have become more fragmented, isolated and of much smaller patches. Land tenure was found to be significantly associated with the vegetation clearing, although the strength of association was weak. The large proportion of deforested riparian zones within steep slopes or first-order streams raises serious questions about the catchment health and the longer term potential for land degradation by upland clearing. This study highlights the use of satellite imagery and geographic information systems in mapping and analysis of landscape structural change, as well as the identification of key issues related to sensor spatial resolution, stream buffering widths, and the quantification of land transformation processes.

Applied machine vision of plants: a review with implications for field deployment in automated farming operations

Automated visual assessment of plant condition, specifically foliage wilting, reflectance and growth parameters, using machine vision has potential use as input for real-time variable-rate irrigation and fertigation systems in precision agriculture. This paper reviews the research literature for both outdoor and indoor applications of machine vision of plants, which reveals that different environments necessitate varying levels of complexity in both apparatus and nature of plant measurement which can be achieved. Deployment of systems to the field environment in precision agriculture applications presents the challenge of overcoming image variation caused by the diurnal and seasonal variation of sunlight. From the literature reviewed, it is argued that augmenting a monocular RGB vision system with additional sensing techniques potentially reduces image analysis complexity while enhancing system robustness to environmental variables. Therefore, machine vision systems with a foundation in optical and lighting design may potentially expedite the transition from laboratory and research prototype to robust field tool.

Soil–water and solute movement under precision irrigation: knowledge gaps for managing sustainable root zones

Precision irrigation involves the accurate and precise application of water to meet the specific requirements of individual plants or management units and minimize adverse environmental impact. Under precision irrigation applications, water and associated solute movement will vary spatially within the root zone and excess water application will not necessarily result in deep drainage and leaching of salt below the root zone. This paper estimates that 10% of the irrigated land area (producing as much as 40% of the total annual revenue from irrigated land) could be adversely affected by root zone salinity resulting from the adoption of precision irrigation within Australia. The cost of increases in root zone salinisation due to inappropriate irrigation management in the Murray and Murrumbidgee irrigation areas was estimated at AUD 245 million (in 2000/01) or 13.5% of the revenue from these cropping systems. A review of soil–water and solute movement under precision irrigation systems highlights the gaps in current knowledge including the mismatch between the data required by complex, process-based soil–water or solute simulation models and the data that is easily available from soil survey and routine soil analyses. Other major knowledge gaps identified include: (a) effect of root distribution, surface evaporation and plant transpiration on soil wetted patterns, (b) accuracy and adequacy of using simple mean values of root zone soil salinity levels to estimate the effect of salt on the plant, (c) fate of solutes during a single irrigation and during multiple irrigation cycles, and (d) effect of soil heterogeneity on the distribution of water and solutes in relation to placement of water. Opportunities for research investment are identified across a broad range of areas including: (a) requirements for soil characterisation, (b) irrigation management effects, (c) agronomic responses to variable water and salt distributions in the root zone, (d) potential to scale or evaluate impacts at various scales, (e) requirements for simplified soil–water and solute modelling tools, and (f) the need to build skills and capacity in soil–water and solute modelling.

Effect of polyacrylamide additions on infiltration and erosion of disturbed lands

The removal of vegetation and disturbance of the soil surface due to a range of human activities results in the potential for soil structure degradation and sediment movement. Polyacrylamides have been used to improve infiltration and reduce erosion on agricultural lands. However, they are not commonly used as part of management and rehabilitation programs on land disturbed by construction or mining activities in Australia. A study was undertaken to investigate the potential for polyacrylamides to improve infiltration and reduce erosion of soil material from 3 Australian mine sites. The polyacrylamides were found to significantly (P < 0.05) increase total infiltration under rainfall, reduce surface hardness, and reduce sediment entrainment and erosion by both rainfall and overland flows. The effectiveness of the polyacrylamide was found to be related to clay content of the soil as well as the molecular weight and charge density of the polyacrylamide. The implications of these results for the management and rehabilitation of disturbed lands are discussed.

Accounting for temporal inflow variation in the inverse solution for infiltration in surface irrigation

A simple modification of the volume balance equation of the IPARM model is presented to facilitate the use of variable inflow. Traditional approaches for estimating infiltration from advance and/or runoff have merely considered the constant or step inflow case. Whenever this assumption is violated, significant uncertainty is introduced into the estimated infiltration parameters. Evaluation of the procedure with a number of data sets has demonstrated significant improvements in the estimates of infiltration parameters. Furthermore, the technique has shown that a portion of the apparent variability in estimated soil intake rates between furrows in the same field is a consequence of the constant inflow assumption. Accounting for the variable inflow to estimate infiltration functions, both standardised the shape of the infiltration curve and reduced the magnitude of the variation between curves. The proposed technique remains restricted by limitations similar to that of other volume balance models but offers greater performance under typical inflow variations often experienced in practice.

Advanced process control of irrigation: the current state and an analysis to aid future development

Control engineering approaches may be applied to irrigation management to make better use of available irrigation water. These methods of irrigation decision-making are being developed to deal with spatial and temporal variability in field properties, data availability and hardware constraints. One type of control system is advanced process control which, in an irrigation context, refers to the incorporation of multiple aspects of optimisation and control. Hence, advanced process control is particularly suited to the management of site-specific irrigation. This paper reviews applications of advanced process control in irrigation: mathematical programming, linear quadratic control, artificial intelligence, iterative learning control and model predictive control. From the literature review, it is argued that model-based control strategies are more realistic in the soil–plant–atmosphere system using process simulation models rather than using ‘black-box’ crop production models. It is also argued that model-based control strategies can aim for specific end of season characteristics and hence may achieve optimality. Three control systems are identified that are robust to data gaps and deficiencies and account for spatial and temporal variability in field characteristics, namely iterative learning control, iterative hill climbing control and model predictive control: from consideration of these three systems it is concluded that the most appropriate control strategy depends on factors including sensor data availability and grower’s specific performance requirements. It is further argued that control strategy development will be driven by the available sensor technology and irrigation hardware, but also that control strategy options should also drive future plant and soil moisture sensor development.

Managing Spatial and Temporal Variability in Irrigated Agriculture through Adaptive Control

Abstract Spatial variability in crop production occurs as a result of spatial and temporal variations in soil structure and fertility; soil physical, chemical and hydraulic properties; irrigation applications; pests and diseases; plant genetics; and local microclimate. This review paper argues that infield variability can be managed and the efficiency of irrigation water use increased by spatially variable application of irrigation water to meet the specific needs of individual management zones (areas of crop whose properties are relatively homogenous). Key areas identified requiring interdisciplinary research are the prescription of irrigated crop water requirements, strategies for quantifying and managing spatial variability, and the development of adaptive systems for control of water application at appropriate temporal intervals and spatial scales. Example strategies for the implementation of adaptive control for furrow irrigation and large mobile irrigation machines are described.

Automated Internode Length Measurement of Cotton Plants under Field Conditions

An in-field vision system has been developed that automatically and non-destructively measures internode length (i.e., the distance between successive main stem branches) of plants in a growing cotton crop for the purpose of inferring plant growth performance and informing crop irrigation management. The system uses monocular video acquisition behind a plant-contacting transparent panel that moves through the crop. Line features are extracted from acquired imagery to estimate candidate nodes on the plants main stem via a two-stage process that may be implemented in real-time. Firstly, candidate nodes are identified in each individual image; secondly, the comparison of sequential images permits the removal of erroneously identified nodes (false positives) and compensation for missed nodes (due to occlusion by a leaf, commonly). Ninety-five internode length measurements were automatically detected from 168 video sequences of 14 plants. Algorithm run-time calculations and the rate of internode measurement acquisition were shown to be adequate for real-time input to spatially varied irrigation control. For this data set, the median absolute error was 5.3 mm in comparison with physical plant measurements, and the standard error in measurement ranged from 1.1 to 5.7 mm, with an average of 3.0 mm.

Spatial prioritization of revegetation sites for dryland salinity management: an analytical framework using GIS

To address the limited application of analytical and modelling techniques in prioritizing revegetation sites for dryland salinity (saline land) management, a case study of the Hodgson Creek catchment in Queensland, Australia, was conducted. An analytical framework was developed, incorporating the use of spatial datasets (Landsat 7 image, DEM, soil map, and salinity map), which were processed using digital image processing techniques and a geographic information system (GIS). Revegetation sites were mapped and their priority determined based on recharge area, land use/cover and sub‐catchment salinity. The analytical framework presented here enhances the systematic use of land information, widens the scope for scenario testing, and improves the testing of alternative revegetation options. The spatial patterns of revegetation sites could provide an additional set of information relevant in the design of revegetation strategies.

Water: advanced irrigation technologies

Limited opportunities to expand the volume of global freshwaters allocated to irrigation means that advanced irrigation technologies, aiming to improve efficiency of existing systems are needed, timely, and are of paramount importance. There is little scope for greater use of allocated global freshwaters for irrigation, due to unprecedented expansion since the 1950s, plus other multiple demands on that resource to meet higher living standards: projected as +400% (manufacturing), +140% (thermal electricity generation), and +130% (domestic use) by 2050 (OECD, 2012). Providing for a further 2 billion people by 2050 will challenge our ability to manage and restore natural assets, including freshwaters, on which life depends (OECD, 2012). Irrigation will need to support a projected 50% increase in global food supply to feed the additional 2 billion people (Jury and Vaux, 2007).