Prioritizing Crop Management to Increase Nitrogen Use Efficiency in Australian Sugarcane Crops

Abstract

Sugarcane production relies on the application of large amounts of nitrogen (N) fertilizer. However, application of N in excess of crop needs can lead to loss of N to the environment, which can negatively impact ecosystems. This is of particular concern in Australia where the majority of sugarcane is grown within catchments that drain directly into the World Heritage listed Great Barrier Reef Marine Park. Multiple factors that impact crop yield and N inputs of sugarcane production systems can affect N use efficiency (NUE), yet the efficacy many of these factors have not been examined in detail. We undertook an extensive simulation analysis of NUE in Australian sugarcane production systems to investigate (1) the impacts of climate on factors determining NUE, (2) the range and drivers of NUE, and (3) regional variation in sugarcane N requirements. We found that the interactions between climate, soils, and management produced a wide range of simulated NUE, ranging from ∼0.3 Mg cane (kg N)-1, where yields were low (i.e., <50 Mg ha-1) and N inputs were high, to >5 Mg cane (kg N)-1 in plant crops where yields were high and N inputs low. Of the management practices simulated (N fertilizer rate, timing, and splitting; fallow management; tillage intensity; and in-field traffic management), the only practice that significantly influenced NUE in ratoon crops was N fertilizer application rate. N rate also influenced NUE in plant crops together with the management of the preceding fallow. In addition, there is regional variation in N fertilizer requirement that could make N fertilizer recommendations more specific. While our results show that complex interrelationships exist between climate, crop growth, N fertilizer rates and N losses to the environment, they highlight the priority that should be placed on optimizing N application rate and fallow management to improve NUE in Australian sugarcane production systems. New initiatives in seasonal climate forecasting, decisions support systems and enhanced efficiency fertilizers have potential for making N fertilizer management more site specific, an action that should facilitate increased NUE.

Liming Positively Modulates Microbial Community Composition and Function of Sugarcane Fields

“…Fertilization is an essential agricultural practice in terms of improving nutrient storage of plants and causing simultaneous changes in soil properties and microbial communities [5,6]. Sugarcane planting systems that are based on extensive fertilization, especially nitrogen, have been adopted to increase sugarcane production to meet increasing sugar demand over the past few decades [7]. Although inorganic fertilizers have a positive impact on sugarcane yield [8], they may also have indirect adverse effects on the environment and soil quality, such as through soil acidification [9], an increase in soilborne pathogens [10], enhanced nitrification, and nitrate leaching [11].…”

N-Fertilization Adjustment in Sugarcane Crop Cultivated in Intensive Mechanization

“…This fact causes sub or super estimates of the N doses to be applied to the crop. In this scenario, new works [7,16] seek the development of strategies for the management of nitrogen fertilization in sugarcane plantations, aiming to increase nitrogen fertilization efficiency.…”

Developing sugarcane - legume companion cropping systems to minimise nitrous oxide emissions

“…Minimising and managing N inputs to optimise sugarcane yield is a priority for the Australian sugarcane industry. Approaches include the selection of sugarcane cultivars with superior N use efficiency (Robinson et al, 2011) and agronomic strategies that improve N fertiliser use (Thorburn et al, 2017, Bell et al, 2014. A simulation study identified N fertiliser rates more prominently affecting N use efficiency (NUE) (Thorburn et al, 2017) than management practices such as timing of fertiliser application, splitting N application, tillage intensity and in-field traffic management.…”

“…Approaches include the selection of sugarcane cultivars with superior N use efficiency (Robinson et al, 2011) and agronomic strategies that improve N fertiliser use (Thorburn et al, 2017, Bell et al, 2014. A simulation study identified N fertiliser rates more prominently affecting N use efficiency (NUE) (Thorburn et al, 2017) than management practices such as timing of fertiliser application, splitting N application, tillage intensity and in-field traffic management. Agronomic efficiency of fertiliser is an indication of how much additional cane (above the amount produced with zero N fertiliser) is produced per kg of N applied, and these values increased in reduced N treatments.…”

“…Globally, N2O emissions from agricultural soils contribute ~12% of anthropogenic greenhouse gas (GHG) emissions (IPCC, 2014), and the average N2O emissions factor of sugarcane soils is 3.87 % (% of N fertiliser emitted as N2O) (Lisboa et al, 2011), nearly 4-fold the estimated 1% for managed soils globally (IPCC, 2006). Australian sugarcane receives average N fertiliser rates of 160 kg N ha -1 y -1 (Fraser et al, 2017, Thorburn et al, 2017, mostly as a single dose of urea during early crop establishment. Whole-season studies of N2O emissions from Australian sugarcane soils show that typical N fertiliser rates (100-200 kg N ha -1 ) generate 2.0 to 72.1 kg N2O-N ha -1 , which translates to N2O emissions factors of 0.3 to 21% (Table 1).…”