Soil health and nutrient management

Permanent URI for this collectionhttp://elibrary2.sugarresearch.com.au/handle/11079/13842

Research outcomes: Soil health is improved with a resulting positive impact on the environment and yield growth. Improved reputation and relationship between industry and environmental groups.

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Start date: 2000Subject: search.filters.subject.Best Management Practice

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    Improved environmental outcomes and profitability through innovative management of nitrogen SRDC research project CSE011 final report
    (2008) Thorburn, P; Webster, T; Biggs, J; Biggs. I; Park, S
    Nitrogen (N) fertiliser additions are an important contributor to productivity and profitability in intensive farming systems, including sugarcane production. However, applying N increases losses of N to the environment, and so all intensive agricultural industries face the challenge of maintaining productivity while minimising environmental impacts of N fertiliser use. This challenge has become particularly important for sugarcane production in Australia because community concern grows over the impact of N on the health of the Great Barrier Reef and sugarcane production has the largest use of N fertiliser in the region. It has been suggested that replacing the N lost from a crop through harvested cane and environmental losses will better align N fertiliser applications to the actual needs of sugarcane crops and the other potential sources of N available to the crop, and so improve the financial and environmental sustainability of the Australian sugarcane industry. In this project we tested and further developed an innovative N fertiliser management system, the N Replacement (NR) system.
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    Review of nitrogen fertiliser research in the Australian sugar industry
    (2004) Thorburn, P
    The management of nitrogen (N) fertiliser is important to the Australian sugar industry, as it is an important nutrient for sugarcane production. However, over application results in reduced profitability and sugar quality, and results in high concentrations of N in soils and water of sugarcane growing areas. An extensive review of current and past research on N fertiliser management in the Australian sugar industry was undertaken to identify possible improvements in N fertiliser management and establish priorities for future research into sustainable management of N fertiliser. The Australian sugar industry has a history of high N fertiliser usage, with applications increasing from the 1960s to the late 1990s. However, industry average sugarcane production has not kept pace with N fertiliser applications, resulting in a steady increase in N fertiliser applied per ton of sugarcane harvested. Historical and recently developed N management strategies rely on matching N applications to the predicted/expected yield of the forthcoming crop. Over-application of N fertiliser is a rational reaction by growers to uncertainty about the size of the coming crop and the long-term impact of N fertiliser on profitability – significant over-fertilisation reduces profits much less than significant under fertilisation. We suggest that past and current N fertiliser management strategies have not adequately accounted for these attitudes, and the resultant longer-term implications for soil and water quality and environmental impacts in sugarcane catchments. While long-term under application of N fertiliser undoubtedly reduces profitability, there is considerable evidence to show that greatly reducing N fertiliser applications for a single crop will not significantly reduce sugarcane production. Thus, the short-term risk of crop yields limited by N deficits is possibly much lower than generally appreciated. If this is so, a new philosophy of N fertiliser management can be developed that remove the uncertainties that drive growers to over-apply N, and so allow closer matching of N inputs to N outputs from a sugarcane system. Rather than aiming to fertilise the coming crop, it may only necessary to replace the N lost from the previous crop, the majority of which is in harvested cane and therefore be easily estimated. Over the past decade, there have been significant advances in our ability to simulate N (and carbon) dynamics in sugarcane production systems. We drew upon these advances to undertake a ‘desktop’ examination of this new ‘replacement’ N management strategy. Three N management scenarios were simulated: (1) the ‘replacement’ strategy, (2) the current recommended strategy and (3) the average amounts of N applied in the industry (i.e., 30 % greater than those recommended). The replacement strategy had similar productivity, greater profitability and lower environmental N losses, whether we simulated potential crop production or a more realistic level of production (resulting from the impact of pests, diseases, lodging, stool damage, etc.). Moreover, these advantages were greater in the simulations of realistic yields. The ‘replacement’ strategy is an evidence based, transparent and defensible N management strategy, all attributes that are important for the sugar industry to maintain self-regulation of N fertiliser management. We suggest that this strategy warrants further testing, through both simulation and field experiments.
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    Overcoming on-farm constraints to productivity and profitability in a wet tropical area
    (2003) Goodson, M; Thorburn, P
    The CCS in the wet tropics has been declining steadily for over three decades, a period in which green cane harvesting-trash blanketing (GCTB) has become standard practice among growers throughout the wet tropics. In the Babinda Mill region, where this situation is most acute, it has been hypothesised that a part of the low CCS problem is due to the effect of GCTB in increasing soil moisture and soil fertility, which aggravates lodging and suckering in the crop and restricts the opportunity for drying crops out. During the 1990’s Babinda growers were assessing alternative management systems to overcome some of these perceived problems associated with trash blanketing. This project aimed to implement best-bet initiatives to overcome problems associated with trash blanketing, and so improve productivity and profitability in a wet tropics environment. The project was directed by stakeholders and conducted using a participative approach. There were four interrelated ‘strands’ of activity undertaken in this project: 1. Liaison and interaction with Babinda growers and the wider industry, achieved through establishment of a Grower Management Group, conducting all trials on farms (as opposed to research stations), distributing regular newsletters and holding regular bus tours and shed meetings to view demonstration sites and discuss trial results. 2. Demonstration of ‘best-bet’ trash management practices (for improved profitability). Trials were established on four farms comparing the impact of raking trash from the stool and/or incorporating it into the soil. 3. Exploration of improved nitrogen fertiliser placement (for improved profitability). Trials were established on two farms comparing different placement of N fertiliser (in the ground or on the trash blanket) and different N carriers (urea and Nitram). 4. Determination of soil and plant nitrogen status in response to different soils and/or management practices. Soil and crop N status were determined in all trials and a survey of amino-N in juice from sugarcane (a good indicator deficiency and over-supply of N to the crop) from all blocks on eight farms in the region. The trash management trial sites consistently failed to demonstrate any advantage of either raking trash from the stool, incorporating trash into the soil, or doing both. Thus the extra cost of purchasing and operating a trash rake is not justified. At one site, in a flood prone area where trash blanketing is impractical, trash burning consistently gave higher yields than trash raking and incorporation. This result suggests that raking and incorporation of trash is economically disadvantageous, in the short term, in these areas. However, damage to the stool during raking caused the lower yields in the raked incorporated treatments at this site and improved methods of raking trash may overcome this problem.
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    A stocktake of the levels and sources of nitrate in groundwaters associated with sugarcane areas
    (2000) Thorburn, PJ; Weier, KL; Biggs, JS
    Water containing high concentrations of nitrate is unfit for human consumption and, if discharging to freshwater or marine habitats, can contribute to algal blooms and eutrophication. Previous studies have found elevated nitrate concentrations in groundwaters underlying sugar-growing areas, particularly the Bundaberg and Burdekin areas, and that in Bundaberg the problem was escalating. Nitrate pollution of groundwaters of the sugar industry is of particular concern because of the proximity of the industry to environmentally sensitive areas and the large number of people (in cities and rural areas) relying on groundwaters for drinking water. However, apart from recent studies in Bundaberg, data on nitrate in groundwater has generally come from inconsistent studies. These studies examining either a limited number of groundwater bores, or large databases of groundwater chemistry where sampling and analytical methods have been variable and, in some cases, inappropriate. So a reliable, consistent, industry-wide definition of the problem does not exist. This project determined the extent of nitrate contamination in groundwater underneath sugargrowing regions of eastern Australia, and examined the likely source of the nitrate. In bores where nitrate concentrations were elevated, and therefore likely to be a result of human activities, concentrations were monitored to provide an assessment of trends in nitrate concentrations. This information was used to promote “best management practices” through relevant extension, industry and regulatory groups, to restrict leaching of nitrate to groundwater.
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    Risk assessment of phosphorus (P) loss and guidelines for P use in lower Herbert soils Final report on SRDC Project No CLW010
    (2000) Bramley, RGV; Wood, AW
    In project CSS3S (Bramley et aI., 1998), a field and laboratory-based survey of the behaviour of phosphorus (P) was carried out on the soils of the lower Herbert River catchment, and sediments derived from them. The aim was to explore the factors governing P sorption or desorption in Herbert soils, and in suspended sediments in associated riverine and estuarine waters, so that the extent of any problem associated with sugarcane and soil-derived inputs to strearnwaters could be defined and advice on the development of best management practices for P fertilizer could be provided. Accordingly, an assessment of the risk of P loss from selected lower Herbert soils was made based on their P sorption characteristics and an assessment of the susceptibility of the lower Herbert soils to runoff following rainfall events. One of the recommendations made at the conclusion of CSS3S was that "spatial analysis of the assessment of P desorption risk based on digital maps of the CSR soil survey would enable more precise guidelines for better P management to be derived.". Following the recent availability of the CSR 1:5,000 soil survey in geo-referenced digital form, this report details the results of the suggested spatial analysis. Nine hundred and thirty four soils for which detailed soil property data are available in the database accompanying the 1:5,000 CSR survey of lower Herbert sugarcane soils were classified according to a range of indices of P sorption and the results mapped using either a geostatistical interpolation routine (kriging) or the mean values for each soil type identified in field survey. The results were coupled with an analysis of the susceptibility of these soils to runoff to produce maps of the potential for P loss.
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    Researching soil health and economics of two farming systems in the Herbert River district : SRDC Grower Group Innovation Project final report
    (2009) Waring, M
    The New Farming Initiative Group (NFIG) consists of six members and has approximately 600ha of sugarcane farming land in the Herbert region. Comparison of soil health of the two farming systems is the primary objective. This project will increase the uptake of several best management practices which are considered to reduce the loss of sediment, chemicals and nutrients from cane lands as well as significantly improve soil fertility due to a healthier soil in terms of its physical, chemical and biological components. The primary aim of the New Farming Initiative Group includes: • Comparison of soil health of the two farming systems. These soil tests have not previously been undertaken in the Herbert and will provide a benchmark of current soil health. The test includes physical, biological and chemical components: • Demonstrate the economics of two farming systems (regional standard and 1.9m dual row/break crop fallow) • Development of group skills through shared knowledge, utilizing the expertise of consultants, building organisation skills and through first hand participation. The trial site consists of three replications, two treatments and one variety. The trial was marked out with GPS to include 9 rows of pre-formed mounds at 1.9m and 11 rows of conventional at 1.55m spacing. The key outcome of this project was the similar average gross margins for the conventional and new farming system treatments. Potentially higher future input costs will favour the new farming system economically, with greater average gross margins expected compared to a conventional farming system. The new farming system produced an average 0.5 unit CCS less sugar than conventional farming. The cause of this statistically significant difference is unclear and warrants further investigation. Essentially, no significant difference was observed in soil health parameters (biological, physical and chemical) between treatments over the 14 month testing interval. Of interest, the new farming system displayed positive trends of increasing pH, increasing organic carbon and higher cation exchange capacity. The project had a relatively short testing interval and longer term soil testing would likely create more meaningful soil health results. Continued soil heath testing and economic analysis is needed to achieve the full benefit from this project. It would be inappropriate to draw any firm conclusions on the comparison of these two farming systems from this study of only two years.