Eagle et al. Fertilizer management and N Losses S1 Supplemental Materials for: Fertilizer management and environmental factors drive N 2 O and NO 3 losses in corn: A meta-analysis Alison J. Eagle, James B. Heffernan, Lydia P. Olander, Katie L. Locklier, and Emily S. Bernhardt 16 pages Supplemental Materials A. Data Collection .........................................................................................S2 Supplemental Materials B. Peer-reviewed Studies with N Loss Data ...................................................S3 Table S1. Studies used in the nitrous oxide (N 2 O) meta-analysis models ............................................ S3 Table S2. Studies used in the nitrate (NO 3 ) meta-analysis models ...................................................... S6 References ............................................................................................................................................ S8 Supplemental Materials C. Yield and Loss Curves ..............................................................................S12 Figure S1. Corn grain yield response to fertilizer N rate in different site-years ................................. S13 Figure S2. Nitrous oxide (N 2 O) emission response to fertilizer N rate in six example site-years ....... S13 Figure S3. Nitrate (NO 3 ) leaching response to fertilizer N rate in five example site-years ................ S14 Supplemental Materials D. Multi-level (Hierarchical) Models ............................................................S15 Supplemental Materials E. Interpretation of Regression Coefficients ................................................S16
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Eagle et al. Fertilizer management and N Losses S1
Supplemental Materials for:
Fertilizer management and environmental factors drive N2O and NO3 losses in corn: A meta-analysis
Alison J. Eagle, James B. Heffernan, Lydia P. Olander, Katie L. Locklier, and Emily S. Bernhardt
16 pages
Supplemental Materials A. Data Collection .........................................................................................S2
Supplemental Materials B. Peer-reviewed Studies with N Loss Data ...................................................S3
Table S1. Studies used in the nitrous oxide (N2O) meta-analysis models ............................................ S3 Table S2. Studies used in the nitrate (NO3) meta-analysis models ...................................................... S6 References ............................................................................................................................................ S8
Supplemental Materials C. Yield and Loss Curves .............................................................................. S12
Figure S1. Corn grain yield response to fertilizer N rate in different site-years ................................. S13 Figure S2. Nitrous oxide (N2O) emission response to fertilizer N rate in six example site-years ....... S13 Figure S3. Nitrate (NO3) leaching response to fertilizer N rate in five example site-years ................ S14
Supplemental Materials D. Multi-level (Hierarchical) Models ............................................................ S15
Supplemental Materials E. Interpretation of Regression Coefficients ................................................ S16
Eagle et al. Fertilizer management and N Losses S2
Supplemental Materials A. Data Collection
If crop yield, N losses, soil water NO3, and soil extractable N values were only presented in graphical form without directly reporting in the literature, numerical values were requested from and provided by individual data owners for research published post-2004. Full-factorial data from combined treatments were also received from individual data owners when available. Any remaining data in graphical form were quantified using DataThief III (B. Tummers, http://datathief.org).
All corn yield values were reported at (or corrected to) 15.5% moisture. In the small number (7%) of cases where yield was reported as total plant biomass, it was converted to grain yield using a harvest index of 0.53. This harvest index is based on a literature review of typical ratios of corn grain as a fraction of total above-ground biomass. A small number of observations were removed from further analysis because of severe drought.
When possible, we included fertilizer rate and crop type from the previous year, as well as variability measures for yield and N losses. Methods for N loss measurements were also documented, including equipment, relevant time-frame, measurement frequency, and peak N loss rates. Nitrous oxide emissions were measured solely with in-field chamber methods. Leaching losses in the database were calculated from NO3
- concentrations measured in porous-cup-collected soil water in combination with hydrological modeling (14%), by measuring tile water drainage volume and NO3
- concentrations (61%), or by using lysimeters (25%).
Where not provided within the published studies, climate data were retrieved from the nearest weather station with complete precipitation and temperature records. Also when not directly provided, best estimates for soil organic matter content were obtained from the SSURGO database and matched to the nearest available location.
Eagle et al. Fertilizer management and N Losses S3
Supplemental Materials B. Peer-reviewed Studies with N Loss Data
Table S3. Studies used in the nitrous oxide (N2O) meta-analysis and hierarchical models, with summary of study and management details. Records listed below the solid heavy line report loss data, but not crop yield, so while they are not incorporated into models they are included here as references.
Ref. No of obs. Location Year(s) Soil texture Tillage Water
mgmt Fert N source and Inhibitors
Fert N rates (kg N/ha)
Fertilizer timing
Fertilizer placement
N2O losses (kg N/ha)
Msrmt time frame
Plant N uptake
Adviento-Borbe et al. (2007) 10 NE/USA 2003–05 Silty clay
loam CP IRR AN, Combo 0–310 Sp, Sp (PP+SD) Brd/Inc 1.4–9.2 GS N
Almaraz et al. (2009) 4 QC/Canada 2002–03 Clay loam MB, NT None AN 0–180 Sp Bnd 2.3–5.5 Unk N
Dell et al. (2014) 32 PA/USA 2009–12 Silt loam NT None ESN, PiNT, SupU, UAN+AP, UAN, Urea
0–154 SD+St Bnd, Brd 0.1–2.9 GS N
Drury et al. (2006) 18 ON/Canada 2000–02 Clay loam NT, CsT, MB None AN 182 SD+St KI(d), KI(s) 1.3–9.0 GS N
Drury et al. (2012) 36 ON/Canada 2004–06 Fine sandy loam
Measurement Timeframe: ST - Short-term, <90days; GS - Growing Season; GS+ - Growing season plus, when ground not frozen; YR - Year-round
Abbreviations
Eagle et al. Fertilizer management and N Losses S6
Table S4. Studies used in the NO3 meta-analysis and hierarchical models, with summary of study and management details. Records listed below the solid heavy line report loss data, but not crop yield, so while they are not incorporated into models they are included here as references.
Ref. No of obs. Location Year(s) Soil texture Tillage Water
mgmt
Fert N source and Inhibitors
Fert N rates (kg N/ha)
Fertilizer timing
Fertilizer placement
NO3 losses (kg N/ha)
Msrmt time frame
Plant N uptake
Bakhsh et al. (2002) 24 IA/USA 1993–98 Silty clay loam CP, NT TD UAN 93–195 PP, SD KI 3–46 GS+ N
Bakhsh et al. (2007) 3 IA/USA 1999–2000 Loam CP, NT TD UAN 140–177 PP KI 9–20 GS+ N
Bakhsh et al. (2010) 10 IA/USA 2001–05 Silty clay loam CP TD UAN 168 AP, PP KI, LCD 0.4–28 GS N
Basso and Ritchie (2005) 12 MI/USA 1994–99 Loam MB None Urea 0–120 Sp Brd 11–89 GS N
Drury et al. (2009) 12 ON/Canada 1996, 1998 Clay loam NT TD, SIRR Urea 150–175 Sp Bnd 4.0–33 YR N
Guillard et al. (1999) 6 CN/USA 1995–96 Fine sandy loam MB None AN 34–196 PP, SD,
Sp Unk 4–61 GS N
Helmers et al. (2012) 20 IA/USA 1990–93 Clay loam CP TD UAN 0–224 AP KI 4–76 GS N
Jayasundara et al. (2007) 2 ON/Canada 2003 Silt loam MB, NT None UAN, Urea 60–150 AP, SD Brd/Inc, KI 1.9–2.1 GS Y
Jaynes (2013) 6 IA/USA 2006, 2008 Clay loam CP TD UAN 134–157 SD, Sp KI 22–46 GS N
Jaynes and Colvin (2006) 8 IA/USA 2002, 2004 Clay loam CP TD UAN 69–199 SD, Sp KI 11–37 GS N
Jaynes et al. (2001) 6 IA/USA 1996, 1998 Loam CP, MB TD AA, UAN 57–202 PP, SD KI 37–61 YR Y
Jemison and Fox (1994) 9 PA/USA 1988–90 Silt loam CP IRR AN 0–200 AP Brd 24–133 Unk N
Kanwar et al. (1997) 24 IA/USA 1990–92 Silty clay loam CP, CsT, NT TD AA 168–202 PP KI 4.5–108 Unk N
Kucharik and Brye (2003) 12 WI/USA 1996–2000 Silt loam CP, NT None AN 0–180 PP Brd 3.2–102 GS Y
Lawlor et al. (2008) 42 IA/USA 1990–2000 Clay loam CP TD UAN 0–252 AP KI 0–109 GS N
Lawlor et al. (2011) 16 IA/USA 2001–04 Clay loam CP None AqA 168–252 F, AP KI 25–86 GS+ N
Kalita et al. (2006) 16 IL/USA 1992–00 Silty clay loam CsT TD Unknown 0–254 PP Brd 3.3–73 YR N
Kaluli et al. (1999) 5 QC/Canada 1994 Sandy loam CP TD, SIRR AN 0–270 SD + St Brd 2.6–22 YR Y
Toth and Fox (1998) 9 PA/USA 1991, 1994 Silt loam CP IRR AN 13–213 PP+St Brd 4.5–92 YR N
Zhu and Fox (2003) 6 PA/USA 1997, 1999 Silt loam CP, NT None AN 0–200 PP+St Unk 8–135 YR N a Yield data reported in Randall et al. (2003a) b Yield data reported in Randall and Vetsch (2005a) c Yield data reported in Walters and Malzer (1990a)
N source, as well as co-applied nitrification and urease inhibitors: AA - Anhydrous ammonia; AN - Ammonium nitrate; AS - Ammonium sulfate; AqA - Aqueous ammonia; ESN - ESN®, Environmental Smart Nitrogen, a polymer-coated urea; NP - Nitrapyrin; SupU - SUPERU™; UAN - Urea ammonium nitrate
Fertilizer timing: AP - At planting; F - Fall; PP - Preplant; SD - Side dress; Sp – Split; St - Starter
Fertilizer placement: Brd - Broadcast; Brd/Inc - Broadcast and incorporated; Bnd - Banded; Bnd SS - Banded subsurface; KI - Knife injected; LCD - Localized compaction and doming; Unk – Unknown
Measurement Timeframe: ST - Short-term, <90days; GS - Growing Season; GS+ - Growing season plus, when ground not frozen; YR - Year-round
Eagle et al. Fertilizer management and N Losses S15
References. Nitrogen fertilizer management studies reporting N2O and/or NO3 measurements in North American corn systems (as summarized in Tables S1 and S2)
Adviento-Borbe, M.A.A., M.L. Haddix, D.L. Binder, D.T. Walters, and A. Dobermann. 2007. Soil greenhouse gas fluxes and global warming potential in four high-yielding maize systems. Global Change Bio. 13:1972–1988. doi:10.1111/j.1365-2486.2007.01421.x
Almaraz, J.J., F. Mabood, X. Zhou, C. Madramootoo, P. Rochette, B.-L. Ma, et al. 2009. Carbon dioxide and nitrous oxide fluxes in corn grown under two tillage systems in southwestern Quebec. Soil Sci. Soc. Am. J. 73:113–119. doi:10.2136/sssaj2006.0371
Bakhsh, A., R.S. Kanwar, T.B. Bailey, C.A. Cambardella, D.L. Karlen, and T.S. Colvin. 2002. Cropping system effects on NO3-N loss with subsurface drainage water. Trans. ASAE 45:1789–1797.
Bakhsh, A., R.S. Kanwar, and J.L. Baker. 2010. N-application methods and precipitation pattern effects on subsurface drainage nitrate losses and crop yields. Water Air Soil Poll. 212:65–76. doi:10.1007/s11270-010-0322-3
Bakhsh, A., R.S. Kanwar, C. Pederson, and T.B. Bailey. 2007. N-source effects on temporal distribution of NO3-N leaching losses to subsurface drainage water. Water Air Soil Poll. 181:35-50. doi:10.1007/s11270-006-9274-z
Basso, B., and J.T. Ritchie. 2005. Impact of compost, manure and inorganic fertilizer on nitrate leaching and yield for a 6-year maize-alfalfa rotation in Michigan. Agric. Ecosyst. Environ. 108:329–341. doi:10.1016/j.agee.2005.01.011
Bronson, K.F., A.R. Mosier, and S.R. Bishnoi. 1992. Nitrous-oxide emissions in irrigated corn as affected by nitrification inhibitors. Soil Sci. Soc. Am. J. 56:161–165.
Dell, C.J., K. Han, R.B. Bryant, and J.P. Schmidt. 2014. Nitrous oxide emissions with enhanced efficiency nitrogen fertilizers in a rainfed system. Agron. J. 106:723–731. doi:10.2134/agronj2013.0108
Drury, C.F., W.D. Reynolds, C.S. Tan, T.W. Welacky, W. Calder, and N.B. McLaughlin. 2006. Emissions of nitrous oxide and carbon dioxide: Influence of tillage type and nitrogen placement depth. Soil Sci. Soc. Am. J. 70:570–581. doi:10.2136/sssaj2005.0042
Drury, C.F., W.D. Reynolds, X.M. Yang, N.B. McLaughlin, T.W. Welacky, W. Calder, et al. 2012. Nitrogen source, application time, and tillage effects on soil nitrous oxide emissions and corn grain yields. Soil Sci. Soc. Am. J. 76:1268–1279. doi:10.2136/sssaj2011.0249
Drury, C.F., C.S. Tan, W.D. Reynolds, T.W. Welacky, T.O. Oloya, and J.D. Gaynor. 2009. Managing Tile Drainage, Subirrigation, and Nitrogen Fertilization to Enhance Crop Yields and Reduce Nitrate Loss. J. Environ. Qual. 38:1193-1204. doi:10.2134/jeq2008.0036.
Duxbury, J.M., and P.K. McConnaughey. 1986. Effect of fertilizer source on denitrification and nitrous-oxide emissions in a maize-field. Soil Sci. Soc. Am. J. 50:644–648.
Fujinuma, R., R.T. Venterea, and C. Rosen. 2011. Broadcast urea reduces N2O but increases NO emissions compared with conventional and shallow-applied anhydrous ammonia in a coarse-textured soil. J. Environ. Qual. 40:1806–1815. doi:10.2134/jeq2011.0240
Guillard, K., T.F. Morris, and K.L. Kopp. 1999. The pre-sidedress soil nitrate test and nitrate leaching from corn. J. Environ. Qual. 28:1845–1852.
Halvorson, A.D., and S.J. Del Grosso. 2012. Nitrogen source and placement effects on soil nitrous oxide emissions from no-till corn. J. Environ. Qual. 41:1349–1360. doi:10.2134/jeq2012.0129
Halvorson, A.D., and S.J. Del Grosso. 2013. Nitrogen placement and source effects on nitrous oxide emissions and yields of irrigated corn. J. Environ. Qual. 42:312–322. doi:10.2134/jeq2012.0315
Halvorson, A.D., S.J. Del Grosso, and F. Alluvione. 2010a. Nitrogen source effects on nitrous oxide emissions from irrigated no-till corn. J. Environ. Qual. 39:1554–1562. doi:10.2134/jeq2010.0041
Eagle et al. Fertilizer management and N Losses S9
Halvorson, A.D., S.J. Del Grosso, and F. Alluvione. 2010b. Tillage and inorganic nitrogen source effects on nitrous oxide emissions from irrigated cropping systems. Soil Sci. Soc. Am. J. 74:436–445. doi:10.2136/sssaj2009.0072
Halvorson, A.D., S.J. Del Grosso, and C.P. Jantalia. 2011. Nitrogen source effects on soil nitrous oxide emissions from strip-till corn. J. Environ. Qual. 40:1775–1786. doi:10.2134/jeq2011.0194
Halvorson, A.D., S.J. Del Grosso, and C.A. Reule. 2008. Nitrogen, tillage, and crop rotation effects on nitrous oxide emissions from irrigated cropping systems. J. Environ. Qual. 37:1337–1344. doi:10.2134/jeq2007.0268
Helmers, M.J., X. Zhou, J.L. Baker, S.W. Melvin, and D.W. Lemke. 2012. Nitrogen loss on tile-drained Mollisols as affected by nitrogen application rate under continuous corn and corn-soybean rotation systems. Can. J. Soil Sci. 92:493–499. doi:10.4141/cjss2010-043
Hernandez-Ramirez, G., S.M. Brouder, D.R. Smith, and G.E. Van Scoyoc. 2009. Greenhouse gas fluxes in an eastern corn belt soil: Weather, nitrogen source, and rotation. J. Environ. Qual. 38:841–854. doi:10.2134/jeq2007.0565
Hoben, J.P., R.J. Gehl, N. Millar, P.R. Grace, and G.P. Robertson. 2011. Non-linear nitrous oxide (N2O) response to nitrogen fertilizer in on-farm corn crops of the U.S. Midwest. Global Change Bio. 17:1140–1152.
Jayasundara, S., C. Wagner-Riddle, G. Parkin, P. von Bertoldi, J. Warland, B. Kay, et al. 2007. Minimizing nitrogen losses from a corn-soybean-winter wheat rotation with best management practices. Nutr. Cycl. Agroecosys. 79:141–159. doi:10.1007/s10705-007-9103-9
Jaynes, D.B. 2013. Nitrate loss in subsurface drainage and corn yield as affected by timing of sidedress nitrogen. Agric. Water Manage. 130:52–60. doi:DOI 10.1016/j.agwat.2013.08.010
Jaynes, D.B., and I.S. Colvin. 2006. Corn yield and nitrate loss in subsurface drainage from midseason nitrogen fertilizer application. Agron. J. 98:1479–1487. doi:10.2134/agronj2006.0046
Jaynes, D.B., T.S. Colvin, D.L. Karlen, C.A. Cambardella, and D.W. Meek. 2001. Nitrate loss in subsurface drainage as affected by nitrogen fertilizer rate. J. Environ. Qual. 30:1305–1314.
Jemison, J.M., and R.H. Fox. 1994. Nitrate leaching from nitrogen-fertilized and manured corn measured with zero-tension pan lysimeters. J. Environ. Qual. 23:337–343.
Johnson, J.M.F., D. Archer, and N. Barbour. 2010. Greenhouse gas emission from contrasting management scenarios in the Northern Corn Belt. Soil Sci. Soc. Am. J. 74:396–406. doi:10.2136/sssaj2009.0008
Kalita, P.K., A.S. Algoazany, J.K. Mitchell, R.A.C. Cooke, and M.C. Hirschi. 2006. Subsurface water quality from a flat tile-drained watershed in Illinois, USA. Agric. Ecosyst. Environ. 115:183–193. doi:10.1016/j.agee.2006.01.006
Kaluli, J.W., C.A. Madramootoo, X.M. Zhou, A.F. MacKenzie, and D.L. Smith. 1999. Subirrigation systems to minimize nitrate leaching. J. Irrig. Drain. Eng. 125:52–58. doi:10.1061/(asce)0733-9437(1999)125:2(52)
Kanwar, R.S., T.S. Colvin, and D.L. Karlen. 1997. Ridge, moldboard, chisel, and no-till effects on tile water quality beneath two cropping systems. Journal of Production Agriculture 10:227-234.
Kucharik, C.J., and K.R. Brye. 2003. Integrated BIosphere Simulator (IBIS) yield and nitrate loss predictions for Wisconsin maize receiving varied amounts of nitrogen fertilizer. J. Environ. Qual. 32:247–268.
Lawlor, P.A., M.J. Helmers, J.L. Baker, S.W. Melvin, and D.W. Lemke. 2008. Nitrogen application rate effect on nitrate-nitrogen concentration and loss in subsurface drainage for a corn-soybean rotation. Trans. ASABE 51:83–94.
Lawlor, P.A., M.J. Helmers, J.L. Baker, S.W. Melvin, and D.W. Lemke. 2011. Comparison of liquid swine manure and aqua-ammonia nitrogen application timing on subsurface drainage water quality in Iowa. Trans. ASABE 54:973–981.
Eagle et al. Fertilizer management and N Losses S10
Maharjan, B., and R.T. Venterea. 2013. Nitrite intensity explains N management effects on N2O emissions in maize. Soil Biol. Biochem. 66:229–238. doi:10.1016/j.soilbio.2013.07.015
Maharjan, B., R.T. Venterea, and C. Rosen. 2014. Fertilizer and irrigation management effects on nitrous oxide emissions and nitrate leaching. Agron. J. 106:703–714. doi:10.2134/agronj2013.0179
McSwiney, C.P., and G.P. Robertson. 2005. Nonlinear response of N2O flux to incremental fertilizer addition in a continuous maize (Zea mays L.) cropping system. Global Change Bio. 11:1712–1719.
Mitchell, D.C., M.J. Castellano, J.E. Sawyer, and J. Pantoja. 2013. Cover crop effects on nitrous oxide emissions: Role of mineralizable carbon. Soil Sci. Soc. Am. J. 77:1765–1773. doi:10.2136/sssaj2013.02.0074
Mosier, A.R., A.D. Halvorson, C.A. Reule, and X.J. Liu. 2006. Net global warming potential and greenhouse gas intensity in irrigated cropping systems in northeastern Colorado. J. Environ. Qual. 35:1584–1598. doi:10.2134/jeq2005.0232
Nash, P.R., P.P. Motavalli, and K.A. Nelson. 2012. Nitrous oxide emissions from claypan soils due to nitrogen fertilizer source and tillage/fertilizer placement practices. Soil Sci. Soc. Am. J. 76:983–993. doi:10.2136/sssaj2011.0296
Omonode, R.A., and T.J. Vyn. 2013. Nitrification kinetics and nitrous oxide emissions when nitrapyrin is coapplied with urea-ammonium nitrate. Agron. J. 105:1475–1486. doi:10.2134/agronj2013.0184
Parkin, T.B., and J.L. Hatfield. 2010. Influence of nitrapyrin on N2O losses from soil receiving fall-applied anhydrous ammonia. Agric. Ecosyst. Environ. 136:81–86.
Pelster, D.E., F. Larouche, P. Rochette, M.H. Chantigny, S. Allaire, and D.A. Angers. 2011. Nitrogen fertilization but not soil tillage affects nitrous oxide emissions from a clay loam soil under a maize-soybean rotation. Soil Till. Res. 115:16–26. doi:10.1016/j.still.2011.06.001
Phillips, R.L., D.L. Tanaka, D.W. Archer, and J.D. Hanson. 2009. Fertilizer application timing influences greenhouse gas fluxes over a growing season. J. Environ. Qual. 38:1569–1579. doi:10.2134/jeq2008.0483
Porter, L.K. 1995. Depleted 15N carryover, leaching and uptake for three years of irrigated corn. J. Contam. Hydrol. 20:209–226. doi:10.1016/0169-7722(95)00069-0
Prunty, L., and R. Greenland. 1997. Nitrate leaching using two potato-corn N-fertilizer plans on sandy soil. Agric. Ecosyst. Environ. 65:1–13.
Randall, G.W., and J.A. Vetsch. 2005a. Corn production on a subsurface-drained mollisol as affected by fall versus spring application of nitrogen and nitrapyrin. Agron. J. 97:472–478.
Randall, G.W., and J.A. Vetsch. 2005b. Nitrate losses in subsurface drainage from a corn-soybean rotation as affected by fall and spring application of nitrogen and nitrapyrin. J. Environ. Qual. 34:590–597.
Randall, G.W., J.A. Vetsch, and J.R. Huffman. 2003a. Corn production on a subsurface-drained mollisol as affected by time of nitrogen application and nitrapyrin. Agron. J. 95:1213-1219.
Randall, G.W., J.A. Vetsch, and J.R. Huffman. 2003b. Nitrate losses in subsurface drainage from a corn-soybean rotation as affected by time of nitrogen application and use of nitrapyrin. J. Environ. Qual. 32:1764–1772.
Sexton, B., J. Moncrief, C. Rosen, S. Gupta, and H. Cheng. 1996. Optimizing nitrogen and irrigation inputs for corn based on nitrate leaching and yield on a coarse-textured soil. J. Environ. Qual. 25:982–992.
Sistani, K.R., M. Jn-Baptiste, N. Lovanh, and K.L. Cook. 2011. Atmospheric emissions of nitrous oxide, methane, and carbon dioxide from different nitrogen fertilizers. J. Environ. Qual. 40:1797–1805. doi:10.2134/jeq2011.0197
Eagle et al. Fertilizer management and N Losses S11
Smith, D.R., G. Hernandez-Ramirez, S.D. Armstrong, D.L. Bucholtz, and D.E. Stott. 2011. Fertilizer and tillage management impacts on non-carbon-dioxide greenhouse gas emissions. Soil Sci. Soc. Am. J. 75:1070–1082. doi:10.2136/sssaj2009.0354
Sogbedji, J.M., H.M. van Es, C.L. Yang, L.D. Geohring, and F.R. Magdoff. 2000. Nitrate leaching and nitrogen budget as affected by maize nitrogen rate and soil type. J. Environ. Qual. 29:1813–1820.
Tan, C.S., C.F. Drury, W.D. Reynolds, P.H. Groenevelt, and H. Dadfar. 2002. Water and nitrate loss through tiles under a clay loam soil in Ontario after 42 years of consistent fertilization and crop rotation. Agric. Ecosyst. Environ. 93:121–130. doi:10.1016/s0167-8809(01)00359-0
Thornton, F.C., B.R. Bock, and D.D. Tyler. 1996. Soil emissions of nitric oxide and nitrous oxide from injected andydrous ammonium and urea. J. Environ. Qual. 25:1378–1384. doi:10.2134/jeq1996.00472425002500060030x
Thornton, F.C., and R.J. Valente. 1996. Soil emissions of nitric oxide and nitrous oxide from no-till corn. Soil Sci. Soc. Am. J. 60:1127–1133.
Toth, J.D., and R.H. Fox. 1998. Nitrate losses from a corn-alfalfa rotation: Lysimeter measurement of nitrate leaching. J. Environ. Qual. 27:1027–1033.
Venterea, R.T., M. Burger, and K.A. Spokas. 2005. Nitrogen oxide and methane emissions under varying tillage and fertilizer management. J. Environ. Qual. 34:1467–1477. doi:10.2134/jeq2005.0018
Venterea, R.T., M.S. Dolan, and T.E. Ochsner. 2010. Urea decreases nitrous oxide emissions compared with anhydrous ammonia in a Minnesota corn cropping system. Soil Sci. Soc. Am. J. 74:407–418. doi:10.2136/sssaj2009.0078
Venterea, R.T., B. Maharjan, and M.S. Dolan. 2011. Fertilizer source and tillage effects on yield-scaled N2O emissions in a corn-cropping system. J. Environ. Qual. 40:1521–1531.
Walters, D.T., and G.L. Malzer. 1990a. Nitrogen Management and Nitrification Inhibitor Effects on Nitrogen-15 Urea: I. Yield and Fertilizer Use Efficiency. Soil Sci. Soc. Am. J. 54:115-122. doi:10.2136/sssaj1990.03615995005400010018x
Walters, D.T., and G.L. Malzer. 1990b. Nitrogen management and nitrification inhibitor effects on nitrogen-15 urea: II. Nitrogen leaching and balance. Soil Sci. Soc. Am. J. 54:122–130. doi:10.2136/sssaj1990.03615995005400010019x
Zebarth, B.J., P. Rochette, D.L. Burton, and M. Price. 2008. Effect of fertilizer nitrogen management on N2O emissions in commercial corn fields. Can. J. Soil Sci. 88:189–195.
Zhu, Y., and R.H. Fox. 2003. Corn-soybean rotation effects on nitrate leaching. Agron. J. 95:1028–1033.
Eagle et al. Fertilizer management and N Losses S15
Supplemental Materials C. Yield and Loss Curves
Using observations from experiments that included at least three different fertilizer N rates for NO3 and five different fertilizer N rates for N2O, models were generated by site-year to look at the rate responses of corn grain yield, N2O emission, and NO3 leaching. Figure 1 shows an example of corn grain yield response of eight different site-years. Yield response for each site-year generally followed a Michaelis-Menten type saturation curve, but with an added y-intercept (instead of starting at zero). The equation is
(3) 𝑌𝑌𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 = 𝑌𝑌0 + 𝑌𝑌𝑖𝑖𝑖𝑖𝑖𝑖[𝑁𝑁𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓]𝐾𝐾𝑚𝑚
where 𝑌𝑌𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 is yield at a given fertilizer rate, 𝑌𝑌0 is yield without fertilizer N, 𝑌𝑌𝑖𝑖𝑖𝑖𝑖𝑖 is the maximum yield increase possible, 𝑁𝑁𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 is N fertilizer rate, and 𝐾𝐾𝑚𝑚 is a saturation constant equal to the fertilizer rate at which half of the maximum yield increase has been achieved. There were some significant differences between locations and some variation between years at the same location. The yield in plots without fertilizer N varied (i.e., different y-intercepts), and so did the yield response to fertilizer N additions (affecting the shape of the curve).
Nitrous oxide emissions responded differently to fertilizer N rate than corn grain yield. Figure 2 illustrates examples from the data. In some locations, N2O emissions even at high fertilizer rates remained much lower than emissions at low fertilizer rates in other locations. As with yield, the baseline emissions (at zero N fertilizer) varied by location and from year-to-year within some locations, demonstrating that available N for the crop and for losses is variable. Nitrate, exhibited even greater variability than N2O, and while NO3 losses did increase with rate, there was not always a clear relationship. The best fit for the relationship of fertilizer N rate to was linear (Figure 3).
Eagle et al. Fertilizer management and N Losses S13
Figure S4. Corn grain yield response to fertilizer N rate in different site-years. Curves with the same color are the same experimental site, but a different year.
Figure S5. Nitrous oxide (N2O) emission response to fertilizer N rate in six example site-years
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Figure S6. Nitrate (NO3) leaching response to fertilizer N rate in five example site-years
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Supplemental Materials D. Multi-level (Hierarchical) Models
The multi-level model initially looks like your typical regression,
where 𝑦𝑦𝑖𝑖𝑖𝑖 is nitrogen loss of observation i at location j, 𝛽𝛽1 is the constant or intercept, and 𝑥𝑥2 and following are covariates with coefficients of 𝛽𝛽2 and following. The residual error term is 𝜉𝜉𝑖𝑖𝑖𝑖. Since we expect the losses at a certain location to be correlated with each other in this model, the error term, 𝜉𝜉, can be split into two components – 𝜎𝜎𝑖𝑖, the error shared by all observations at the same location; and 𝜖𝜖𝑖𝑖𝑖𝑖, the remaining residual unique for each observation. This error term at the group level (𝜎𝜎𝑖𝑖) represents the combined effects of omitted characteristics or unobserved heterogeneity for each location.
A likelihood ratio test examines the total variance at the group level (i.e., between groups) and the total variance at the individual level (i.e., within groups). This test determines whether group level variance is sufficient to favor the multi-level regression over an ordinary regression model.
In addition to correcting for unknown or un-quantified differences between groups, the multi-level model addresses unbalanced observations, so that the overall effect of an independent variable (or �̂�𝛽 ) is a weighted mean of the cluster means. Therefore,
(2) �̂�𝛽 =∑ w𝑗𝑗𝑦𝑦�.𝑗𝑗𝐽𝐽𝑗𝑗=1
∑ w𝑗𝑗𝐽𝐽𝑗𝑗=1
, where w𝑖𝑖 = 1𝜑𝜑�+𝜃𝜃�/𝑖𝑖𝑗𝑗
and 𝑦𝑦�.𝑖𝑖 is the average for each cluster, now weighted by the weighting factor w𝑖𝑖. The weighting factor, or the contribution of a specific group to the overall mean, increases with increasing group size (i.e., 𝑛𝑛𝑖𝑖 is greater. Similarly, as the variance increases, both within groups (𝜃𝜃� ) and between groups (𝜑𝜑�), the weighting factor decreases and the contribution of that group is reduced.
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Supplemental Materials E. Interpretation of Regression Coefficients
When the dependent variable in a regression model is log-transformed (with the natural log), the co-efficient can be approximated as the percent change in the non-transformed value (since adding 0.05 to ln(X) is almost equivalent to increasing X by 5%). However, this is not exact, and for coefficients above 0.05 (a change of more than 5%), the approximation starts to become less accurate, and the % change trends higher than the coefficient in the model. To be precise, we calculated the change in emissions from the model coefficients as follows:
Y1 = Y0 * (exp((X1-X0)*coeff)). Where the change in fertilizer rate X is 1 unit, and the coefficient is small, the % change in Y (i.e., (Y1 – Y0)/Y0) is nearly the same as the coefficient (e.g., for N2O Model 1, exp(0.0064) = 1.00646, so the change is 0.65%). In the case of a 10 unit increase in N fertilizer rate, the % change in Y is somewhat higher (e.g., exp(10*0.0064) = 1.066518, giving a 6.7% increase). Also, in the case of a switch from standard fertilizer to using nitrification inhibitors, the % change also differs from the coefficient (e.g., exp (1*-0.357) = 0.700, which is a 30.0% decrease; (1 - 0.700)/1 = 0.300). Thus, while the coefficients are often seen as the % change, it is only an approximation.