Nitrogen Use Efficiency for Sugarcane-Biofuel Production: What Is Next?

Abstract

Land area devoted to sugarcane (Saccharum spp.) production in Brazil has increased from 2 million to 10 million ha over the past four decades. Studies have shown that, from an environmental perspective, the transformation of nitrogen (N) fertilizers into N 2 O gases can offset the advantages gained by replacing fossil fuels with biofuels. Our objectives here were to review recent developments in N management for sugarcane-biofuel production and assess estimates of N use efficiency (NUE) and N losses based on future scenarios, as well as for life-cycle assessments of bioenergy production. Approximately 60 % of N-based fertilizer applied to sugarcane fields in Brazil is recovered by plants and soils, whereas N losses to leaching and N 2 O emissions can average 5.6 and 1.84 % of the total applied N, respectively. Maintenance of trash, rotation with N-fixing legume species, and optimization of byproducts usage have potential for reducing the N requirements of sugarcane cultivation in Brazil. Moreover, the development of sugarcane genotypes with higher NUEs, along with management systems that consider soil capacity of mineralization, is required for improving the NUE of sugarcane. Strategies to maintain N as NH 4 + in sugarcane-cropped soils also have the potential to reduce N losses and enhance NUE. The development of secondgeneration biofuels is important for increasing biofuel production while simultaneously maintaining N rates and improving NUE, and sugarcane systems in Brazil show potential for sustainable biofuel production with low N rates and limited N 2 O losses. Reducing N rates in sugarcane fields is thus necessary for improving sugarcane-based biofuel production and reducing its environmental impacts.

Field-Based Estimates of Global Warming Potential in Bioenergy Systems of Hawaii: Crop Choice and Deficit Irrigation

“…Multiple recent studies have shown that temperate perennial bioenergy crops only reduce measured GHG emission compared to annuals if they are not fertilized [34,43,44]. In Brazil, maintaining N amendment rates and improving nitrogen use efficiency (NUE) through genetic improvement and better management practices are critical to increasing biofuel production sustainably [45]. In these Brazilian systems, N losses to leaching and N 2 O emission can be as high as 5.6% of added N. In this study, gaseous losses were consistently very low because of efficient fertilizer and irrigation practices in use on the plantation.…”

Agronomic performance of green cane fertilized with ammonium sulfate in a coastal tableland soil

“…This trend was not observed for P, Ca, and Mg (Table 4). The efficiency of N fertilizer uptake by sugarcane was approximately 49% when the equivalent to 100 kg N•ha −1 was applied (Table 5), and this value was well above the range of 5 to 30% reported for the crop in other regions (Meier et al 2006;Trivelin et al 1996;Franco et al 2011;Otto et al 2016). The lowest efficiencies of N acquisition by sugarcane can be a consequence of N source and rainfall, when there is no other apparent limitation for the plant growth.…”

“…Nitrogen is usually a limiting nutrient to crop yield in the weathered tropical soils, and positive yield responses to N fertilization are observed for sugarcane in Brazil (Dourado Neto et al 2010;Fortes et al 2013), although less frequently to plant cane (first cycle) owing to higher contribution from N in soil and residue due to N mineralization, as well as the biological nitrogen fixation (Balasubramanian et al 2004;Urquiaga et al 2012;Otto et al 2016). A review on sugarcane pointed out the relatively low N use efficiency (NUE) by the crop, which averages 26% from a range of 7 to 40% of the N fertilizer applied.…”

“…A review on sugarcane pointed out the relatively low N use efficiency (NUE) by the crop, which averages 26% from a range of 7 to 40% of the N fertilizer applied. Including the fraction of N fertilizer remaining in the soil, less than 60% of the applied N is accounted for in the soil-plant system after harvesting (Otto et al 2016), which indicates high N losses.…”

Biomass Production and Nutrient Removal of Energy Cane Genotypes in Northeastern Brazil

“…3). In comparison, a yield reduction in sugarcane is commonly observed in later crop cycles (Dharmawardene, 2005;Matsuoka and Stolf, 2012;Otto et al, 2016;Castro et al, 2017) than a yield increase, mainly due to the lack of traffic control during mechanized harvesting (Camilotti et al, 2005;Tavares et Magalhães et al, 2012;Cassia et al, 2014) that can cause damage in ratoon cycles, thus reducing plant density. In comparison, a yield reduction in sugarcane is commonly observed in later crop cycles (Dharmawardene, 2005;Matsuoka and Stolf, 2012;Otto et al, 2016;Castro et al, 2017) than a yield increase, mainly due to the lack of traffic control during mechanized harvesting (Camilotti et al, 2005;Tavares et Magalhães et al, 2012;Cassia et al, 2014) that can cause damage in ratoon cycles, thus reducing plant density.…”