Introduction

1. *Contact: Ma. Arlene Adviento-Borbe Dept. of Plant Sciences University of California-Davis aaadvientoborbe@ucdavis.edu Phone: 1-530-754-5338 Crop rotation and fertilizer type affect ammonia and greenhouse gas emissions in a long-term maize-based agroecosystems Odor Assessment Laboratory Maria Arlene Adviento-Borbe1, Jason P. Kaye2, Mary Ann Bruns2, Marshall D. McDaniel2, Matthew McCoy2 and Scott Harkcom2 11210 PES Bldg., Dept. of Plant Sciences, University of California-Davis, CA; 2116 ASI Bldg., Dept. of Crop and Soil Sciences, The Pennsylvania State University, University Park, PA. Introduction Increases in maize yield to meet future demand will require N fertilizer, yet 40 to 70% of available soil N may not be used within a growing season. Various studies report that between 0.2 and 47% of the N in fertilizers and animal manure applied to crop fields is lost to the atmosphere depending on fertilizer chemistry, manure source, environmental conditions, water management, and soil properties. Gaseous N losses from soils are driven by the processes of volatilization, microbial denitrification, and nitrification. While N2O emissions are generally increase with increased fertilizer N rate, the impacts of fertilizer type on gaseous N losses are not clear. Also, it is difficult to predict gaseous emissions from manure-treated soils because labile C added with organic N may have multiple direct and indirect effects on soil and microbial communities. Crop rotation with legumes and application of animal manure can reduce the use of synthetic N fertilizer and inevitably, reduced emissions of greenhouse gases (GHG). Long-term multiple legume rotations and manure inputs as an alternative sources of N in maize cultivation can illustrate the effects of decades of legume rotation and manure additions on emissions of ammonia and GHG. Gas flux measurements:Vented cylindrical surface chamber, with 0.248 cm diameter and chamber height of 0.09 m was placed within each treatment plot for gas measurements (Fig. 1). A model 1412 Photoacoustic Multi-gas monitor, PAS (Innova AirTech Inc.) with optical filters was used to measure N2O, NH3, and CO2 fluxes. A 2-min interval within a 14 min sampling period was used to calculate gas efflux rates. Additional measurements;Soil temperature, soil water content, bulk density, pH, electrical conductivity at 5 and 15 cm soil depths; exchangeable NH4-N and NO3-N at 10 cm soil depths; grain yield, yield components, N and C contents in aboveground biomass. Table 1. Cumulative soil surface fluxes of N2O, CO2 and NH3, grain yield and global warming potentials of greenhouse gases in the four cropping systems during growing seasons of 2006 and 2007. Values are means (n = 8 and when followed by the same letter are not significantly different at P <0.05. Results • Soil fluxes of CO2 in all crop rotations followed the growth of maize with the highest flux measured around tasseling stage. Soil CO2 flux rates ranged from 11 to 1015 mg CO2-C m-2 hr-1 for both years (Fig.1). Total growing season CO2 efflux was significantly high in MNCC due to greater maize residue input and soil labile C from manure application (Table 1). For legume rotations (FNCA and MNCA) cumulative soil CO2 growing season fluxes were similar regardless of N sources (Table 1). • Large soil N2O efflux increases were measured following fertilizer N addition, warm weather and consistently wet soil condition with hourly flux rates ranged from 163 to 201 µg N2O-N m-2 hr-1 (Fig. 1). Cumulative growing N2O emissions were significantly lowest in the high N rate rotation (FNCC) while all other rotations had comparable total N2O emissions (Table 1). The lack of direct impact of high synthetic N fertilizer rate to N2O emissions suggests interaction between fertilizer sources and crop rotations; with synthetic N fertilization, N2O emissions were higher in CA than in CC rotations while with manure applications, N2O emissions were similar in both CA and CC rotations. • Ammonia fluxes were highest within 3 hr of manure spreading followed by a rapid decline for both rotations (MNCC and MNCA) (Fig 1). Typical NH3 emissions were <107 µg NH3-N m-2 hr-1. Growing season NH3 emissions suggest that the soil may have acted as sink of NH3. However, background NH3 emissions were ≤ detection limit of PAS gas analyzer, thus our efflux measurements may not quantify actual NH3 emissions. • Mean grain yield was similar for both N sources but between crop rotations, CA had higher yield than CC rotation (Table 1). Alfalfa rotation may enhance soil N available and plant N uptake which translate to higher agronomic yield. • Global warming potential (GWP) of N2O and CO2 fluxes was highest in MNCC due to large CO2 emitted from this field. Also, MNCC systems had the highest GWP in all crop rotations (Table 1) while CA rotations fertilized either with synthetic N or dairy manure produced the highest grain yield and emitted the lowest GWP to the environment. a b Objectives • To assess changes of GHG; nitrous oxide (N2O), ammonia (NH3), and carbon dioxide (CO2) gas fluxes in response to long-term maize rotation with legumes and fertilizer N additions, • To determine yield-scaled global warming potential of N2O and CO2 emissions in maize rotations with legumes fertilized with inorganic N or animal manure. c d Fig. 1. Chamber set up (a) , 1412 PAS gas analyzer (b) and gas sampling in the field (c). The HRE long-term field experiment (d). Material and Methods Field experiment: Hunter Rotation Experiment (HRE) located at the R.E. Larson Agricultural Research Center The Pennsylvania State University, Rock Springs, PA (Fig.1). Soil GHG and NH3 fluxes were measured weekly in non-irrigated maize grown in 2006 and 2006, respectively. Four cropping systems were sampled: FNCC:Synthetic N (NH4NO3) fertilizer – continuous maize rotation for a 12.6 Mg/ha yield goal: 6-7 plants m-2; 224 kg N/ha, 29 kg P/ha and 15 kg K/ha applied. FNCA:Synthetic N (NH4NO3) fertilizer – maize following alfalfa rotation for a 12.6 Mg/ha yield goal: 6 to 7 plants m-2 (maize), 1.5 to 2.2 seeds m-2 (alfalfa) ; 90 kg N/ha, no P and K applied. MNCC:Dairy manure - continuous maize rotation for a 12.6 Mg/ha yield goal: 6-7 plants m-2; 225 kg N/ha, 13 kg P/ha and 66 kg K/ha applied; 3.37 Mg ha-1 cumulative manure N since 1990; 112.7 Mg ha-1 cumulative manure solids since 1990. MNCA:Dairy manure - maize following alfalfa rotation for a 12.6 Mg/ha yield goal: 6-7 plants m-2; 120 kg N/ha, 15 kg P/ha and 74 kg K/ha applied; 1.61 Mg ha-1 cumulative manure N since 1990; 53.8 Mg ha-1 cumulative manure solids since 1990. Conclusions • The effects of legume rotation and manure management are interactive. In CC rotations, manure additions increased GWP relative to synthetic N application while in CA rotations, synthetic N and manure had similar GWP. • Long-term use of alfalfa rotations regardless of N sources increased grain yield and reduced global warming potential of soil gas fluxes during the maize growing season. • Continuous manure fertilization and maize monocropping showed the least desirable combination of lower yield and higher GWP in a maize-based crop sequences. Fig. 2. Field dynamics of soil surface fluxes of carbon dioxide, (CO2), nitrous oxide (N2O) and ammonia (NH3) in the four crop rotations during 2006 and 2007. VE, V6, VT and PM correspond to emergence, sixth leaf stage, tasseling and physiological maturity of maize, respectively.