High-yield maize with large net energy yield and small global warming intensity - PubMed (original) (raw)

High-yield maize with large net energy yield and small global warming intensity

Patricio Grassini et al. Proc Natl Acad Sci U S A. 2012.

Erratum in

Proc Natl Acad Sci U S A. 2012 Mar 6;109(10):4021

Abstract

Addressing concerns about future food supply and climate change requires management practices that maximize productivity per unit of arable land while reducing negative environmental impact. On-farm data were evaluated to assess energy balance and greenhouse gas (GHG) emissions of irrigated maize in Nebraska that received large nitrogen (N) fertilizer (183 kg of N · ha(-1)) and irrigation water inputs (272 mm or 2,720 m(3) ha(-1)). Although energy inputs (30 GJ · ha(-1)) were larger than those reported for US maize systems in previous studies, irrigated maize in central Nebraska achieved higher grain and net energy yields (13.2 Mg · ha(-1) and 159 GJ · ha(-1), respectively) and lower GHG-emission intensity (231 kg of CO(2)e · Mg(-1) of grain). Greater input-use efficiencies, especially for N fertilizer, were responsible for better performance of these irrigated systems, compared with much lower-yielding, mostly rainfed maize systems in previous studies. Large variation in energy inputs and GHG emissions across irrigated fields in the present study resulted from differences in applied irrigation water amount and imbalances between applied N inputs and crop N demand, indicating potential to further improve environmental performance through better management of these inputs. Observed variation in N-use efficiency, at any level of applied N inputs, suggests that an N-balance approach may be more appropriate for estimating soil N(2)O emissions than the Intergovernmental Panel on Climate Change approach based on a fixed proportion of applied N. Negative correlation between GHG-emission intensity and net energy yield supports the proposition that achieving high yields, large positive energy balance, and low GHG emissions in intensive cropping systems are not conflicting goals.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.

Soil N2O emissions of irrigated maize plotted against applied nitrogen (N) inputs (A) and N surplus (B). N2O emissions were estimated by following IPCC N-input [□ (23)] or van Groenigen et al. N-surplus approach (VG; •; ref. 24). Average (±SE) N2O emissions, N inputs, and N surplus (medians in parenthesis) are shown. B Inset shows the relationship between N surplus and applied N inputs.

Fig. 2.

Frequency distribution of fossil-fuel energy input (A), net energy yield (B), net energy ratio (C), and global warming potential intensity (GWPi) (D) based on data from 123 irrigated maize fields.

Fig. 3.

Maize grain yield plotted against fossil-fuel energy inputs (A) and GWP (B). Lines indicate average 3-y median (solid line) and fifth and 95th percentiles (dashed lines) for NER and GWPi calculated for irrigated maize in Tri-Basin NRD. Published data for other US maize systems are shown for comparison (open symbols;

Table S1

). (C) Relationship between GWPi and net energy yield for irrigated maize in Tri-Basin NRD.

Fig. 4.

Average (±SE) energy input rate, net energy yield, net energy ratio, and GWPi of irrigated maize under different combinations of: irrigation system (pivot; surface), crop rotation [maize after maize (M-M) or maize after soybean (S-M)], and tillage method [conventional (CT); reduced till (RT)]. Maize grain yields (Mg⋅ha−1) are shown above bars in Middle Upper. All values are 3-y (2005–2007) means. Differences (Δ) and t test significance for selected comparisons between factor levels are shown (n.s., not significant).

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High-yield maize with large net energy yield and small global warming intensity - PubMed (original) (raw)