Identification of opportunities for improved nitrogen management in sugarcane cropping systems using the newly developed Canegro-N model

Abstract

Sugarcane (Saccharum spp. L.) cropping systems require the application of substantial amounts of fertiliser nitrogen (N), especially under irrigated conditions and in areas where rainfall is sufficient for high dry matter production. Inadequate N applications can reduce yields, while excess N or inappropriately timed applications can result in the export of significant quantities of N to the environment as a pollutant. An N subroutine has now been included into the Canegro crop model which is based in the DSSAT (Decision Support System for Agrotechnology Transfer) framework. Data from a field and lysimeter trial conducted in Pongola, South Africa were used to calibrate and evaluate the model, following which the model was used to investigate two potential approaches to improve fertiliser N management. Findings were, firstly, that measured and simulated results show on-farm monitoring of soil inorganic N levels and adjusting fertiliser applications accordingly has considerable potential for reducing fertiliser requirements and N losses. Secondly, during the periods between active crop growth cycles, significant amounts of inorganic N can accumulate in a soil as a result of mineralisation. Accounting for this N enables fertiliser N application to be delayed to some time after planting or commencement of ratoon growth, thereby significantly reducing the risky period during which applied N may be leached. For the system modelled in this study, inorganic N made available through organic matter mineralisation was sufficient to match initial crop demand for *55 days following ratooning. When ammonium-based fertilisers are used, lower volatilisation losses can also be expected with this strategy. These findings now need to be confirmed in field trials. Modelling, combined with adequate measured data for calibration purposes, can be a powerful tool to identify improved N management practices for a particular cropping system. In its current form, Canegro-N can be used to improve our understanding of N dynamics in sugarcane production systems and to guide management practices and future research.

Integrated Nutrient Management in Sugarcane

“…Similar attempts have also been made in Brazil (Palma Lopez et al 2002) to derive fertilizer recommendations for different soil types based on expected yields in each soil type, dry matter production, nutrient accumulation and nutrients supplied by soil as well as fertilizer efficiency. Van Der Laan et al (2011) suggested that Canegro-N can be used to improve our understanding of N dynamics in sugarcane production systems and to guide management practices and future research.…”

Environmental Benefits of Improved Water and Nitrogen Management in Irrigated Sugar Cane: A Combined Crop Modelling and Life Cycle Assessment Approach

“…The goal of this assessment is to develop a suitable LCA framework for sugar cane production and to apply it to quantify the environmental benefits of improved irrigation water and N fertilizer management. The analysis is based on data acquired during a combined lysimeter and field trial conducted in Pongola, South Africa (27°24' S, 31°35' E, 308 m asl; mean annual temperature = 21°C, mean annual rainfall = 690 mm) from 1986 to 1989 (Thompson, 1991;Van der Laan et al, 2011). The system under investigation ( Figure 1) is a virtual farm representing the mainstream features and practices in the Pongola area (farm size, cropping system, equipment and practices).…”

“…The system under investigation ( Figure 1) is a virtual farm representing the mainstream features and practices in the Pongola area (farm size, cropping system, equipment and practices). Following calibration and validation, the DSSAT-Canegro model (Jones et al, 2003;Van der Laan et al, 2011) was used to simulate water use, crop yield and extractable sucrose content, and soil carbon and N dynamics over 16 seasons between 1986 and 2001 (two cycles of one plant crop followed by seven ratoon crops). The 1.8 m deep sandy clay soil classified as a high-yield potential Hutton soil form (Soil Classification Working Group, 1991) [Ferric Luvisol (FAO)/Alfisol (USDA)] and is representative of around 23% of soils in the irrigated regions of the South African sugar industry (South African Sugar Association Experiment Station (SASEX) (1999)).…”

Nitrogen Management Guidelines for Sugarcane Production in Australia: Can These Be Modified for Wet Tropical Conditions Using Seasonal Climate Forecasting?

“…Even with the adoption of environmentally sustainable sugarcane production practices, there is a risk that 'environmental pollutants', including N, could be lost from the sugarcane production system due to external influences. As N is the nutrient most susceptible to environmental loss and applied in the greatest quantity to optimise yield, greater emphasis needs to be placed on the development of environmentally sustainability yet profitable N management strategies [125,147,148,157].…”

“…Although sugarcane requires large inputs of N for successful crop growth [157], it is relatively inefficient in the recovery of N fertiliser [156]. Recovery studies of applied N fertiliser in the crop and surrounding soil in Australia indicate maximum recoveries are just over 60 % of N applied [36,104,156].…”