Abstract
High fertilizer application and over-irrigation in sugarcane systems can cause considerable N2O emissions. Optimized water-fertilization management which reduces N2O emissions, while maintaining sugarcane biomass, is crucial, but may affect nitrogen fixation by sugarcane. This study evaluated the combined effect of water-fertilization on sugarcane biomass and nitrogen fixation in field trials in southern China. Treatments included drip and spray irrigation, with three levels (0% (low), 50% (medium), 100% (high)) of irrigation and of fertilizer. A rain-fed crop (no irrigation or fertilizer) was included as the control. The results showed that (1) spray irrigation with medium water and high fertilization increased biomass. The optimum combination in sugarcane elongation stage was drip irrigation with medium water and high fertilization, while drip irrigation with high water and high fertilization was the best choice for maturity stage. (2) For sugarcane nitrogen (δ15N) content, spray irrigation with medium water and high fertilization was the best combination in seedling and tillering stages. The optimum combination in the elongation stage was drip irrigation with medium water and high fertilization, and in maturity stage was drip irrigation with high water and high fertilization. (3) For soil (δ15N content), drip irrigation with high water and high fertilization proved optimal for seedling, tillering, and maturity stages. (4) In seedling stage, sugarcane (δ15N content) was found to be strongly correlated with leaf area index, soil water, soil temperature, and soil electrical conductivity. Soil (δ15N content) was correlated with photosynthesis and soil temperature. In conclusion, drip irrigation appears most suitable for field planting, while the best treatment in seedling and tillering stages is medium water-high fertilization, and that the best in elongation stage is high water-medium fertilization. The optimum water-fertilizer combinations identified here can provide a scientific basis for optimization and management of irrigation and fertilization in China and other regions with similar environments.
Highlights
Licensee MDPI, Basel, Switzerland.Methane (CH4 ), carbon dioxide (CO2 ), and nitrous oxide (N2 O) are important greenhouse gases (GHG) emitted in agriculture [1,2,3]
Irrigation type had a significant effect on root biomass (p < 0.05) in the elongation stage, and on stem and leaf biomass (p < 0.05) in the maturity stage
The interaction between water and fertilizer was significant for stem biomass in the seeding, tillering, and maturity stages, and highly significant for root and leaf biomass (p < 0.001) in the elongation stage (Figure 2)
Summary
Methane (CH4 ), carbon dioxide (CO2 ), and nitrous oxide (N2 O) are important greenhouse gases (GHG) emitted in agriculture [1,2,3]. Well-drained soils in agricultural regions are usually sinks of CH4 [4,5,6]. Since CO2 is both emitted and taken up by plants in photosynthesis, it has little influence on the GHG emissions balance, making N2 O the most important GHG emitted from agricultural soils [7]. N2 O emissions from agrarian soils have increased due to its partial denitrification [3].
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