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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Item Item Effect of harvest time on N-fertiliser requirements in the Wet Tropics : ASSCT extended-abstract paper(ASSCT, 2019) Skocaj, DM; Schroeder, BL; Park, G; Salter, BItem Is magnesium deficiency a causal agent of sugarcane Yellow Canopy Syndrome? : ASSCT peer-reviewed paper(ASSCT, 2019) Tippett, O; Olsen, DJ; Ostatek-Boczynski, ZYellow Canopy Syndrome (YCS) is a disorder affecting sugarcane in the Australian industry, the cause of which is unknown. This paper reviews YCS research focusing on magnesium imbalance as a possible cause of the condition. Four studies were undertaken to evaluate the role of Mg in YCS incidence and severity. In Trial 1 sugarcane leaves were collected at multiple locations in the Burdekin and Herbert with samples taken from sugarcane blocks with both YCS symptomatic and asymptomatic plants. Despite adequate soil-Mg, leaf-Mg concentrations were significantly lower (p?0.05) in leaves 2, 3, 4, 5 and 6 of YCS symptomatic plants in both regions suggesting an imbalance of this critical nutrient. Trial 2 measured Mg concentrations in sugarcane leaves before, during, and after YCS symptom expression. Symptomatic cane showed decreased leaf-Mg concentrations, but this returned to normal levels once the cane recovered. Trial 3 treated YCS symptomatic cane with foliar and soil applications of Mg in an attempt to mitigate the condition. Neither treatment resulted in alleviation of the YCS symptoms. Trial 4 treated sugarcane with foliar-Mg and soil-Mg prior to onset of symptoms. Despite elevating the Mg concentration in leaves, these pre-symptomatic treatments did not prevent YCS expression and plants exhibited YCS symptoms similar to that of the untreated control. We conclude that YCS affected cane is associated with reduced leaf Mg concentrations, but it is unlikely that this is the cause of YCS per se, as concentrations were well above critical thresholds for plant health. YCS occurs independently of Mg and low Mg is an indirect effect rather than a cause. Given that disruption to plant nutrient balance has been described as a symptom of some plant diseases, we speculate that these findings suggest a biotic causal agent.Item Nitrogen accumulation in biomass and its partitioning in sugar cane grown in the Burdekin : ASSCT peer-reviewed paper(ASSCT, 2016) Connellan, JF; DeutschenbaurNitrogen is a key component of metabolic processes in plants and due to its mobile nature in soils is often a limiting factor in achieving maximum yield in commercial sugarcane crops grown in Australia. Demand for N depends upon a crop’s yield potential which is determined by climate, crop age and class and management practices (Muchow and Robertson, 1994). Determining the correct amount of nitrogen required to achieve maximum cane yield while minimising losses to the environment is a difficult task; however developing a basic understanding of nitrogen accumulation in biomass and the rate at which it accumulates will provide useful insights for agronomists, industry advisors and farmers. There have been few studies into the accumulation of nitrogen in the above-ground biomass of sugarcane in Australia. Wood et al. (1996) investigated the accumulation of N in the above ground biomass of two cultivars (Q117, Q138) and confirmed earlier findings from work in South Africa conducted by Thompson (1988), that most of the N was taken up in the first six months following planting/ratooning. In a recent review, Bell et al. (2014) reported that greater than 90% of the total above-ground N uptake occurs in the 200 day period after planting/ratooning. Few studies have been conducted into the accumulation of nitrogen in below ground biomass (roots and stool) of sugarcane in Australia. Bell et al. (2014), summarised the limited data collected to date and suggested that N in stool and root accumulates at about 20 kg N/ha/year while a further 10 kg N/ha/year accumulates in root material down to 60 cm. The objective of this study was to gain an insight into nitrogen accumulation in the above and below ground biomass of sugarcane and its partitioning in crops grown under irrigation in the Lower Burdekin region of Australia.Item Does ratoon age impact on N-fertiliser requirements in the Wet Tropics? : ASSCT poster paper(ASSCT, 2019) Skocaj, DM; Schroeder, BL; Park, G; Hurney, APItem Aspects of temporal N management in sugarcane in sub-tropical Queensland : ASSCT peer-reviewed paper(ASSCT, 2019) Panitz, JH; Schroeder, BL; Skocaj, DM; Salter, BThe proximity of the Australian sugar industry to the Great Barrier Reef (GBR) has resulted in ongoing concerns about elevated concentrations of the dissolved inorganic nitrogen (DIN) in the near-reef environments due to sugarcane production practices on-farm. Although the nitrogen (N) guidelines within the SIX EASY STEPS nutrient-management program are generally appropriate, scope exists for fine-tuning of N application rates for specific circumstances. In particular, enhanced-efficiency fertilisers (EEFs), such as urea coated with 3,4-dimethylpyrazole phosphate (DMPP-urea) and polymer-coated urea (PC-urea), offer promise potentially to improve nitrogen-use efficiency (NUE) in sugarcane production and reducing DIN losses to the GBR. Temporal N-management strategies using these EEFs were assessed within a randomised complete-block field trial conducted in a sub-tropical environment on a well-drained soil supported by a concurrently run shorter-term pot experiment. There were no significant yield responses to applied N, split applications or use of EEFs in the trial in either the plant or first-ratoon crops. Rainfall measured during these seasons would not have resulted in excessively wet conditions at the trial site and may have contributed to the lack of responses to EEFs. Increased N-uptake by the crop, due to the use of N strategies away from the standard practice (i.e. by using EEFs or split applications of urea), improved NUE values based on crop N, but this did not always translate into any improvements in yield. The highest partial net returns in the plant and first-ratoon crop corresponded to the control treatments. Urea applied at 120 kg N/ha in a single application resulted in the next best partial net returns in both crops. This appeared to be the most appropriate strategy to minimise risk to growers. The cost of EEF fertilisers negatively affected the partial net returns, with DMPP-coated urea being more affordable than the poly-coated urea. The results of the pot experiment that included two sugarcane cultivars supported these outcomes. Further work, across seasons (dry, wet and 'normal'), is needed to evaluate more fully the potential of EEFs for use in specific circumstances.Item Nitrogen availability from legume and past fertiliser history : ASSCT peer-reviewed paper(ASSCT, 2019) Salter, B; Kok, E; Skocaj, DM; Schroeder, BLIt is likely that land-based activities within the Australian sugar industry have a negative effect on the quality of water in the Great Barrier Reef lagoon. Improvements to nitrogen use efficiency (NUE) are likely to require a greater understanding of processes affecting N availability, crop-N demand and uptake in sugarcane farming systems. Two issues associated with improving N management were investigated. Firstly, should fertiliser-N recommendations for ratoon crops be altered following a good legume fallow? Secondly, what contribution do past fertiliser-N management practices have on N uptake? Field experiments were established at Mackay. The first- and second-ratoon crops were fertilised at either 0 or 150 kg N/ha (0N; 150N). This followed a fallow period where a bare or soybean fallow were established and a plant crop that received 138 kg N/ha (bare fallow) or 18 kg N/ha (legume fallow). In the third and fourth-ratoon crops, due to a lack of any significant response to fallow management, the trial was altered to investigate the influence of previous N management on crop-N response. Plots either received 0N or 150N following a history of 0N or received 0N or 150N following a history of 150N. Crop-N uptake, leaf-N, soil mineral-N, crop yield and NUE data were collected. Results showed that the soybean fallow had no lasting N contribution through the crop cycle when N rates in the plant-cane crop were reduced as recommended in the SIX EASY STEPS. Based on this, fertilising ratoons at 'normal' N rates following legume fallows should be maintained. In the third-ratoon crop, where there was a history of 150N application, crop-N uptake was greater than where there was a history of 0N application. Cane yield at 0N was higher where there was history of 150N than 0N. These effects were not present in the fourth-ratoon crop. The results either showed a small fertiliser-history effect or were associated with greater N uptake by a crop in better condition.Item Effect of long-term application of potassium on sugarcane and soil properties in the Herbert River district : ASSCT peer-reviewed paper(ASSCT, 2019) Park, G; Schroeder, BL; Wood, AW; Skocaj, DMExcess potassium (K) fertiliser use can have a significant effect on sugar quality and refining costs but offers no benefit to sugarcane crop yield. Potassium fertiliser guidelines are based on soil texture and two measures of soil potassium: readily available or exchangeable K and reserve K. The maximum recommended K rate for the Herbert is 120 kg/ha. A long-term K trial was established on a sandy loam soil at Macknade. High K application rates increased soil exchangeable K levels and resulted in luxury K consumption by the sugarcane plant. This significantly increased juice conductivity and third-leaf K levels. It also resulted in significant reductions in third-leaf values for Ca and Mg.Item Spatial distribution of potential soil constraints affecting nitrogen management in the Wet Tropics : ASSCT peer-reviewed paper(ASSCT, 2019) Skocaj, DM; Schroeder, BL; Hurney, AP; Rigby, A; Telford, DPosition in the landscape and climatic conditions experienced during the growing season, especially following the application of nitrogen (N) fertiliser, has important implications for crop growth, N uptake and N losses. Understanding the spatial distribution of soils where crop growth and responsiveness to applied N may be constrained in wet or dry years will allow growers and advisors to refine N-management strategies. To identify soils where crop growth and responsiveness to applied N may be restricted, a system of grouping soils that better reflected agronomic performance under different climatic conditions was required. The categorisation system considered position in the landscape, N-mineralisation potential, soil water-holding capacity in both wet and dry years, propensity to waterlog in wet years and presence of a water table in wet years. In dry years, waterlogging and the presence of a water table do not impact crop growth to the same extent as moisture availability, and, hence, in dry years, it is more important to categorise soils based on water-holding capacity. The major sugarcane-growing soils in the Tully and South Johnstone mill areas were categorised using this system. This resulted in five soil groups to describe the impact on crop growth and N responsiveness in wet and dry years. Given the application of N fertiliser to ratoon crops predominately occurs around spring, wet years were defined as receiving high spring-summer rainfall, whereas dry years were defined as receiving low spring-summer rainfall. Classifying wet and dry years according to spring-summer rainfall also allows growers and advisors to refer to seasonal climate forecasting indices for guidance on the likelihood of experiencing a wet or dry year. In wet years, the impact on crop growth, responsiveness to applied N and potential for lower N uptake is greatest for soil group five. These soils tend to occur in the lowest positions in the landscape, experience severe waterlogging and a persistent water table. They are also subject to frequent water inundation following extreme rainfall events. The spatial identification of soil constraints will complement the development of whole-of-farm nutrient-management plans in the Wet Tropics region. Knowledge of soil constraints influencing sugarcane growth and responsiveness to N will allow growers and advisors to better identify areas where nutrient-management strategies may require further fine-tuning. This information may also be of value in improving other management decisions including varietal selection and harvest scheduling