Sluggett, Adam, 2010 Solute Dynamics in Advanced Fertigated Horticulture, Flinders University, School of the Environment
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Increasing demand for rapid crop establishment, high yields and better fruit quality has warranted a change in how irrigated horticultural crops are managed. An emerging trend in the industry is intensive fertigation to meet current crop requirements without the need to store water or nutrients in the soil for a substantial amount of time. This type of practice has been coined Advanced Fertigation (AF), where the fundamental principals include reducing the wetted zone and applying nutrients in smaller, and more frequent doses. There is little scientific literature regarding solute dynamics as affected by AF, which forms the premise of this thesis. The research was conducted at three differently managed citrus orchards within the Sunraysia fruit growing regions of Victoria and New South Wales, Australia. The research begins with a numerical modelling study to investigate soil water movement as affected by suction cup soil water samplers. The suction cup actively samples water from the unsaturated zone by means of an applied vacuum and has been chosen as the main tool in this study to monitor solute dynamics within the soil. The model is the first to comprehensively investigate the suction cup influence under a wide range of soil types and soil moisture conditions while using a decreasing vacuum extraction process. The decreasing vacuum process is used by many suction cup practitioners, making this information vital. The second stage of this research attempts to quantify deep drainage and nitrate leaching below the root zone of AF managed citrus orchards using in situ monitoring tools. No study has investigated deep drainage and nitrate leaching under AF management for Australian conditions, making the study important in determining the possible environmental and economic issues related to this type of management system. The method also critically assesses the influence of soil heterogeneity and measurement error on the estimate of deep drainage and nitrate leaching. In the final stage of the research a comprehensive data set from three contrasting AF citrus orchards has been analysed. This data provides information regarding the transport of solutes and possible strategies to enhance AF management. The interaction between the ceramic of the suction cup and two solutes (nitrate and phosphate) has also been investigated to determine the reliability of suction cups to represent the true soil solution. This research assists in understanding the complexity of solute dynamics in the root zone of AF crops. It provides important information regarding the water extraction process, possible environmental issues and ways to use solute data to effectively manage AF.
Keywords: soil solution, horticulture, fertigation
Subject: Environmental Science thesis
Thesis type: Masters
School: School of the Environment