Soil health and nutrient management
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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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Item Improving the efficiency of nitrogen fertilisation of sugarcane under minimum till and trash conservation cultural conditions (Final report SRDC Project BS37S)(1992) Chapman, LS; Freney, R; Denmead, OT; Wood, AW; Saffigna, PGObjectives of the experiments were (1) Determine the extent of NH3 volatilisation when urea and ammonium sulfate are applied to the surface of a trash blanket in four cane-growing regions. Evaluate the effect of various placements of urea in a trash blanket under wet and dry moisture regimes by quantifying the amount of N recovered in the soil-plant system.Item Assessing clonal and nitrogen interaction on ccs in sugarcane in the wet tropis ; SRDC project BSS180 final report(2003) Hurney, AP; Berding, N; Grace, DThere has been a negative trend in CCS in the Tully-Mossman region since the mid-1960s that has been linked to increased extraneous matter and suckers in the cane supply. The situation had become particularly bad during 1990-1996, with most mill districts within the region experiencing problems with low CCS. An increase in the frequency of lodging and incidence of suckers was possibly contributing to this problem and there was a perception that this was related to inappropriate use of nitrogen fertiliser for the locally grown cultivars. There were also concerns that current cultivars were not suited to the local environmental conditions. Growers choosing to grow inappropriate cultivars for particular locations were thought to be exacerbating the problem.Decisions on what cultivar to grow and how much fertiliser to apply are management options that could be modified if they were contributing to the low CCS problem. These issues were addressed in this project by studying the effects of four rates of nitrogen (0, 70, 140, 210 kg N/ha) on lodging, suckering, CCS and cane yield of the three cultivars Q117, Q120 and Q138. These experiments were conducted on three different soil types at three locations within the Tully mill district. The objectives of this project were to provide a better understanding of the role of nitrogen and cultivars in the low CCS issue to facilitate the development of improved management options.In the plant crops, which were planted after a fallow, nitrogen had no influence on cane yield, CCS, lodging or suckering under the environmental conditions in which these crops were grown. However, it did increase both cane yield and lodging in first- and second-ratoon crops. Responses were limited by adverse interactions with the wet conditions and nitrogen losses due to leaching and/or volatilisation. Nitrogen had no direct influence on CCS in the ratoon crops, but it did have an indirect negative effect, because it increased the incidence of lodging. Rates of N application could be reduced in both plant and ratoon crops, which would reduce production costs. It would also be beneficial environmentally.There was no evidence of nitrogen accumulation in the soil from high nitrogen fertiliser application even following a low-yielding crop. This is of concern from an environmental viewpoint if inappropriate nitrogen rates are applied, as any excess nitrogen will be lost from the soil due to leaching or denitrification. The data suggested that the critical leaf nitrogen concentration might vary between cultivars. This provides an opportunity to reduce nitrogen rates for cultivars with lower nitrogen requirements.Current cultivars do have high potential CCS, but this cannot be realised, partially because of their susceptibility to lodging and suckering. All three cultivars tested, Q117, Q120 and Q138, are susceptible to lodging in well-grown crops. It appears that the susceptibility of Q120 and Q138 is high in crops yielding more than 70-80 t/ha under the wet conditions of the wet tropics.The potential reduction in CCS from total lodging was estimated at about 10% across all cultivars in these trials. The actual loss in CCS is governed by the actual proportion of lodging in the crop and was estimated at 0.4 units in crops that had 25% lodging. This is a hidden cost of which growers are generally not aware. There are no management options that can be implemented to minimise this loss. Severe and multiple lodging events had a negative impact on CCS and cane yield in Q120 and Q138, reducing profitability. In these circumstances, the negative effects of lodging can be reduced if the time between harvesting and occurrence of lodging is reduced. Increased returns to the grower of $200 $300/ha are possible using this strategy.Lodging was less extensive in Q117 and lower-vigour cultivars, such as Q117, may offer a more appropriate ideotype for the wet tropics, because of their lower susceptibility to lodging. Economic impact was estimated at a loss of $7.5 million to growers within the region from a moderate lodging event affecting 25% of the crop. Adoption of agronomic practices to improve physical support of the crop is only partially successful in reducing the intensity of lodging. This can only be achieved by the implementation of a research program to select cultivars with a low incidence of lodging, while maintaining or improving productivity.The cultivars Q117, Q120 and Q138 are representative of those being grown in the wet tropics and demonstrated a high propensity to sucker. Lodging is not a pre-requisite for sucker initiation, as the emergence of suckers was generally first noted under a closed canopy. Suckers have a negative effect on CCS, because they dilute the cane juice through their high moisture and low sucrose composition. In these experiments, 10% by weight of suckers in the cane supply reduced CCS by a little over 1 unit. The increased cane yield from suckers is inflating productivity estimates but not improving profitability; the level of suckering experienced in these experiments would reduce regional grower-income by approximately $6 million. It is possible to select against suckering propensity and this has already been introduced into the crop improvement program. However, research into the relationship between suckers and longevity of ratoons is required because of the potential impact on productivity.An appropriate extension program needs to be developed to disseminate the findings of this research to growers. The results from this project have been extended to the industry. There have also been extension programs for BMP of cultivars. However, there is still a large gap between extension and adoption, which is why additional extension programs are recommended. Adoption of findings on nitrogen will reduce production costs, as well as have a positive environmental impact. Management strategies are available to partially alleviate the negative impacts of lodging and suckering. However, further research is required to fully overcome the effects of these phenomena.Item Final report SRDC project BSS197 : Products and mechanisms for the amelioration of sodic soils(2005) Ham, GJThis project set out to examine a number of issues associated with sodic soils. These included: 1) the impact of soil sodicity on crop production; 2) the reduction of adverse impacts of soil sodicity through irrigation management and/or the use of soil ameliorants; 3) the properties and potential efficacy of a range of products being marketed as 'soil ameliorants' throughout the northern part of Queensland; 4) the means by which a selection of these ameliorants effected beneficial changes to sodic soils; and 5) to establish a close linkage between these investigations and a method for the field identification and measurement of sodicity being developed in a closely associated Sugar CRC project.Item 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, SNitrogen (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.Item Final report SRDC Project CG013 Growers working together to improve water quality in the Herbert Sugar Industry(2008) Wood, A; Wrigley, T; Phillips, K; Sheedy, PThe sugarcane area of the Herbert River district is located adjacent to the Great Barrier Reef (GBR). The quality of water entering the GBR lagoon from the Herbert district is one of the most important environmental issues facing the Herbert sugar industry. However, little data on water quality are available from catchments consisting entirely of sugarcane. This project was conducted to establish a number of water quality monitoring sites in relatively small catchments where the land use is solely sugarcane and where individual growers or groups of growers could measure the quality of water in farm drains using simple tools and relate it to their farming practices. Eleven growers volunteered to participate in the programme. They were keen to participate because they felt that sugarcane growers’ reputation of being good custodians of the land had been tarnished by various external studies of water quality and they were eager to demonstrate that their activities were not polluting drainage water. A series of suitable sites for taking and testing water samples were established and V notch weirs were inserted in the drains for the purpose of measuring rates of water flow. A series of simple tools were developed for measuring sediment and nutrients drainage water leaving the farms. An experienced water engineer who had worked in the district for many years agreed to coordinate the project and proceeded to train the growers involved. He also set up and equipped a water analysis laboratory so that the measurements taken by the growers could be validated. Occasional samples were also sent to a NATA accredited laboratory for further validation of the nutrient determinations but also for measurements of pesticide residues. The growers involved in the project have recorded water quality measurements for three years and have also maintained records of on-farm practices that may impact on water quality such as tillage, fertilising, land levelling and herbicide applications and other activities that may impact on water quality. The growers were provided with information on desirable water quality levels. If their measurements exceeded these levels, growers reacted quickly to seek possible explanations for the elevated readings. The project was evaluated at the commencement, mid-term and just before its conclusion. The growers involved developed a list of the critical factors that needed to be achieved in order for the project to be successful. The mid-term evaluation was conducted with members of the Project Consultative Group and the final evaluation was again conducted with the growers involved in the project. Feedback was generally positive but there were a few areas where things could have been improved. The project outcomes consisted largely of improved knowledge, particularly amongst the growers, of what simple techniques are available for measuring nutrients, pH, dissolved oxygen and turbidity of farm drainage water. Growers learnt what constituted high, medium and low levels for the different water quality parameters and developed a better understanding of the relationship between rainfall and discharge characteristics of drains on their farms. They improved their understanding 4 of the relationship between on-farm management practices and water quality and of the accuracy and reliability of the different tools used to measure water quality. An important outcome has been the continued engagement and support of growers involved with the project, and the engagement and support of regulatory and other government support agencies through the project consultative group. This is important for the next phase of the project which aims to expand from 11 growers to around 100 growers conducting water quality monitoring. The existence of a committed nucleus of growers will be essential for helping to inspire others to participate. Likely economic benefits of the project will be increased farm profitability arising from improved farm practices associated with better management of farm inputs such as fertilisers and herbicides. Reduced input costs arising from reductions in soil tillage and more targeted applications of nutrients and herbicides will also contribute. Environmental benefits will arise from improved water quality on farm and in the downstream ecosystem, and improved soil health arising from changes in farming practices. Social benefits will include the empowerment of growers, who are now armed with better information about their farm practices and the likely impacts on water quality; greater confidence amongst growers when interacting with government and environmental groups; and improved attitudes and engagement by growers in sustainable land management.Item Review of nitrogen fertiliser research in the Australian sugar industry(2004) Thorburn, PThe 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.Item Evaluating the potential for improved sugar yields by assessing the climatic and soil constraints to production in southern cane-growing districts(1999) Muchow, RC; Hughes, RM; Horan, HLThis project conducted strategic research to better understand the processes of yield accumulation in low temperature NSW environments and to identify limits to yield. The fundamental knowledge gained in this project can be used to assess yield limitations and the scope for yield improvement. In addition, the findings are a pre-requisite to the design of management and genetic improvement strategies to boost production in southern sugarcane growing environments. An additional spin-off of this project is a better functional basis of the processes of yield accumulation encapsulated in the APSIM Sugarcane systems model to allow extrapolation of the findings more broadly across the sugar industry. An analysis framework was used to express sucrose yield in terms of biomass accumulation and the proportion on biomass present as sucrose. Crop biomass was analysed in terms of radiation capture and utilisation. Partitioning was examined in terms of the proportion of crop biomass present as stalk and the stalk sucrose concentration on a dry matter basis. Crops growing under "potential yield" conditions were analysed and compared to those growing under "commercial yield conditions".Item Evaluating the leaf chlorophyll meter as a tool for nitrogen management in sugarcane(1995) Keating, BA; Smith, KNitrogen 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.Item Overcoming on-farm constraints to productivity and profitability in a wet tropical area(2003) Goodson, M; Thorburn, PThe 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.Item A reference booklet for canegrowers on the nutrition and fertilizing of sugarcane for different soil types(2003) Wood, AW; Schroeder, BL; Stewart, RL; Roth, CHA wide range of different soils are used for sugarcane production in the Herbert River district. An understanding of these differences both at district and farm levels will ensure that nutrient management reflects this diversity and enables profitable and sustainable sugarcane production. The Australian sugar industry has used a generalised, industry-wide set of fertiliser recommendations with no specific guidelines for different regions, climatic conditions or soil types. This booklet is a first attempt to produce specific management guidelines for all of the different soil types used for sugarcane production in a cane area. Twenty four different soil types have been identified in the sugarcane production area of the Herbert and have been mapped at a scale of 1:5000, which is appropriate for soil-specific management recommendations to be delivered at block level. Growers can currently access soil maps of their farms through Herbert Cane productivity Services Ltd. and plans are in place to provide all growers with the capability of printing their own soil maps. In the booklet each soil type is described in terms of its appearance, where it occurs in the landscape, and its chemical and physical properties. Guidelines for the management of nutrients, tillage, drainage and irrigation and the minimisation of environmental risks are provided for each soil type. These guidelines have been developed using research results from a companion SRDC funded project, BSS232 “Improved nutrient management in the Australian Sugar Industry”. The soil booklet produced in this project is likely to be the first of a number of regional soil management publications that are likely to be produced for the Australian Sugar Industry. The booklet is intended for use by cane growers and their advisers, and where possible the information is presented in as non-technical way as possible. This approach is particularly appropriate for the current situation of the sugar industry with continuing low sugar prices, the need to reduce production costs together with mounting environmental pressures which demand demonstration of responsible soil and nutrient management. The guidelines in this booklet are aimed at providing best practice soil and nutrient management for Herbert growers that will not only maintain or improve crop yields and soil fertility but will also provide opportunities for cost reduction whilst enhancing sustainability and delivering better environmental outcomes.