Browsing by Author "Keating, BA"

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Evaluating the leaf chlorophyll meter as a tool for nitrogen management in sugarcane
(1995) Keating, BA; Smith, K
Nitrogen is an important constituent of chlorophyll, the compound that gives plants their green colour and the compound that absorbs radiation energy as the basis of plant growth. When nitrogen is in short supply, the chlorophyll content of leaves is reduced and in extreme cases, the leaves take on a yellow (or chlorotic) colour. There is an upper limit to leaf "greenness" and leaf nitrogen can continue to rise even when chlorophyll has reached a "plateau". These simple concepts are illustrated in the figure below. This project was aimed at evaluating a portable leaf chlorophyll meter as a tool in nitrogen management of sugarcane. As chlorophyll is a critical component of the photosynthetic system, reductions in leaf chlorophyll may result in lower sugarcane growth rates and this may impact on final sugar yields. In addition, leaf nitrogen is expensive and time consuming to determine on an extensive basis. The notion was that the chlorophyll meter could provide a far simpler alternative to leaf analysis for the monitoring of nitrogen status of sugarcane crops. The project consisted of measurements of leaf nitrogen and chlorophyll on sugarcane crops grown under a range of nitrogen regimes at locations in the Herbert, Bundaberg and northern NSW regions. Leaves at various levels in the canopy were measured and in the majority of instances samples of the bulk canopy were taken. Samples of the sap from the leaf mid-ribs were collected at the same time and analysed for nitrate using a rapid field test. In all 450 leaf N - chlorophyll meter comparisons were collected at various occasions over the November 1993 to June 1994 period.
Final report to the Sugar Research and Development Corporation CTA007 A modelling framework to integrate research on nitrogen management of sugarcane
(1996) Keating, BA
This project used a measurement and modelling approach to explore the processes controlling nitrogen supply and losses in the crop and soil elements of sugarcane production systems. Measurements took place both in the field and laboratory. These measurements, together with data coUected from other sugarcane research projects in Australia and overseas, lead to the development of the APSIM-Sugarcane simulation model. This model captures the main elements of our understanding of sugarcane growth, yield, N uptake and utilisation and water use. APSIM is a modular modelling system, and the Sugarcane module is compatible with other APSIM modules of soil processes and crop management. Within the life of this project, APSIM-Sugarcane was used to investigate N management strategies in sugarcane production systems. A major outcome of these modelling studies was the recognition of the potential for substantial N losses via leaching in situations where N fertiliser inputs exceeded crop demands. This project drew together different threads in nitrogen research on sugarcane for the first time. Prior to this, the focus was on either empirical "rates and dates" experiments, which while underpinning current N fertiliser recommendations, were not advancing our understanding of N in the crop-soil system, and on studies of particular N processes(eg volatilisation or mineralisation), which were not integrated with one another or with the broader system performance.
Improving CCS in the wet tropics via block-specific monitoring of nitrogen in cane delivered to the mill : final report CTA045
(SRDC, 2003) Keating, BA; Webster, AJ; Biggs, M
This project seeks to implement a scheme for monitoring the nitrogen status of all cane crops in a wet tropics mill district and aims to work with growers in the use of this information to improve CCS and reduce the risks associated with the overuse of nitrogen fertiliser.
Monitoring cane at the mill to improve nitrogen management on the farm : final report CTA029
(SRDC, 2002) Keating, BA; Biggs, IM; Webster, AJ
The project originally had a third objective, namely to “Develop promising leads in rapid and cost effective analyses of N compounds in the mill juice stream to a “proof-of-concept” stage.” Instrumentation issues and industry developments with respect to installation on on-line NIR infrastructure meant that this third objective was transferred to the project CTA045, which is on going. Objective 1 was addressed via laboratory analyses of cane sourced from a wide range of experimental studies in different seasons at a range of sites, involving variation in N fertiliser inputs, sugarcane varieties, irrigation inputs, and other agronomic variables. Objective 2 was addressed via a series of grower-managed on-farm trials in which N fertiliser inputs were varied above and below the grower’s “normal” management and the results were interpreted in relation to additional information obtained from soil analyses and amino-N analyses of the cane at harvest time.