Management zone‐based estimation of positive and negative nitrous oxide flux in organic corn fields

Accurate estimation of field-scale nitrous oxide (N2O) fluxes is hindered by their considerable variability and the fact that soils can be both sources sinks for N2O. This particularly challenging organic systems have complex rotations inputs. study used digital soil mapping survey datasets to explore spatial controls N2O “hot moments” induced precipitation with strategic sampling designed identify covariates influence emission patterns. Soil after rain events were measured within three management zones (MZs, “High,” “Medium,” “Low”) delineated crop productivity, fertility, hydrological features in eight fields during 2018 2019 corn (Zea mays L.) growing seasons. Hot moments typically occurring 1 d included positive negative fluxes. The MZ-based design identified regions different patterns flux, hotspots being co-located areas poorer drainage higher fertility. Covariates best explained hot growth stage, moisture, slope, texture, matter. Negative large enough offset so averaged net only significantly between “High” “Low” MZs. Had been omitted, would increased estimates 37%. Processes lead consumptions must better quantified improve management-associated flux. Use efficiently capture needed information, but temporal weighting scale up results. We our ability reduce from agricultural because they are largest anthropogenic source this potent greenhouse gas (Dalal et al., 2003; Fowler 2009). Efforts efficiency N use require identification reward practices emissions (Akiyama 2010; Halvorson 2014). Quantifying flux at field crucial identifying effective vary widely space time (Desjardins Hénault 2012; Mathieu 2006). Instead gathering numbers samples estimate field-averaged (Folorunso & Rolston, 1984; Li 2013; Röver 1999; Turner 2016), a plan captured “hotspots” (Groffman 2009; Hall 2018) might more cost-effective alternative approach dense sampling. approaches precision agriculture increase productivity varying rates fertilizer based on tests yield (Fleming 2000; Khosla 2002; Peng et, Rogovska 2019). While just few studies shown monitor loss (Ferguson Ping 2008), could work if chosen maximize yields also correlated processes contributing environmental loss. An adapted differences among MZs pre-determined known control emissions. Key factors (e.g., moisture or water-filled pore [WFPS], temperature, inorganic content, pH, carbon [SOC] labile C, texture) then (Duncan 2019; Heinen, 2006; Lark Milne, 2016; Schmidt 2000). cost substantially reduced data describing these already available public through national remote sensing sufficiently detailed resolve scales. very fine time-step hourly) due fluctuations substrate availability, solubility (Blackmer 1982; Laville 2011). Accordingly, fixed-time interval schemes weekly bi-weekly) commonly cause underestimation overestimation cumulative depending relationship those events, rainfall, C cycling tillage, fertilization, irrigation) (Cui Davis 2017; Parkin, 2008). sought strategically heavy record main contributors (Krichels Kusa Molodovskaya Smith Tiedje, 1979). Abrupt pulses associated rewetting promote rapid microbial consumes accumulated lysed cells dry period release physically protected matter caused aggregate slaking (Kim Ruser Moreover, quickly reduces oxygen levels when level high diffusion slowed (Davidson, 1992; Reeves Wang, 2015; Schjønning 2003). A multi-day scheme complete pulse following conditions favorable denitrification fluctuate availability levels. Rain event-based need repeated over seasonality dynamics as occurrence magnitude expected change inputs growth. actually shift late season consumption (i.e., conversion N2) increases favored abundances nitrate low (Davidsson Leonardson, 1997; van Groenigen Vanitchung Both soil-produced before it reaches atmosphere, atmospheric N2O, which diffuses into lower concentrations (Clough 2005; Wu 2013), result even Even though model estimated usually scaled down under condition where WFPS than 90% (Rabot 1998; Van Der Weerden 2012), denitrification-induced general, fluxes, often omitted modeling (Parton 2001) treated noise measures (Billings, 2008; Schlesinger, 2013). More accurate requires consider realistic range favoring Portable Fourier Transform Infrared (FTIR), offers detection limits (≈ 0.02 mg L−1 N2O) compared (≈0.3 L−1) (IPCC, detect sensitivity capacity in-field make FTIR suitable chromatography (GC) storage evacuated vials transported back lab (Esler Rochette Eriksen-Hamel, Hensen Warlo 2018). goal was using required limited resources. Specific objectives to: (a) rain-induced information about (b) survey-based field- lab-based measurements explain account Sampling carried out amended manure Illinois contents notably course (Basche 2014; Muhammad Skinner 2014, Zhou 2017). Fields located Piatt County, Illinois, sampled phase 2018–2019. All had incorporated red clover (Trifolium pratense prior chicken litter application (≈27 g m−2) planting. Because impractical sample all once considering transportation collection, we adjacent (Supplemental Figure S1) similar history types paired them four blocks. Samples same block collected day comparison bias amount received (Table 1). each fields. Within MZs, subsamples taken within-zone variability. consecutive days event (>15 mm) preceded (>4 d). assumed 4-d effectively resulting previous (Beare Garcia-Montiel Sexstone 1985). two pair targeting planting tasseling stages, respectively. pairs 24 h preceding 1) extracted NOAA (Diamond 2013) station closest sites. followed Greenhouse Reduction Agricultural Carbon Enhancement network (GRACEnet) protocol (Timothy Venterea, 2010) static chamber-based 9 a.m. 3 p.m. Chamber bases (15 cm diam.) installed depth 10 inter-row least Rates concentration capped chambers monitored Gasmet DX4040 analyzer (Gasmet Technologies Inc.) forming closed-loop system an in-line desiccator chamber top analyzer. closed 8 min measurement changes recorded min. calculated fitting linear regression R outliers excluded Cook's distance detected insignificant (P > .05). For quality control, calibrated N2 purged air point temperature 0-to-5-cm simultaneously correct effects successfully < .05) failed differed production (Figure 2a). As expected, greater High Low surprisingly, varied manner. occurred flux) 4 rain. average sites points 0.79 m−2 day−1. number, annual (0.29 m−2), fall end meta-database developed al. (2017) application. Of course, event-induced exceed (Li Dobbie Smith, 2006) most cases winter except freeze thaw (Risk Ussiri Ignoring (37%) occur wide conditions, models do not <90% likely overestimate (Hallin 2018; presence larger S2A) produced observed Although labels did predict contribute understanding Field stage exerted much Table S2). .001, 2b) greatest (1.63 day−1) S3), appear poorly matched significant daily These show how important site peaks noticeably managed farmer extremely fertilization rotation practices. Averaged (1.22 ± 3.78 times (0.34 0.67 2c) depletion substrates stage. Greater S2B) consistent other observations (Abbasi 2007; Gale Probert 2005). On average, declined significant. frequency finding frequent late-season (Adviento-Borbe Kumar Lehman 2017) amendments (Davis Dittmer 2020). Day 2 .05, 2d) decline further Days 4. many (or models) assume exponential decay rates, neither nor found consistently time. Spatial revealed interactions Supplemental S2) Net Medium decrease 3b). It may largely (Congreves 2019) 60% (Barton Del Prado Gu 2016) and, later resulted nitrification decreased (Bateman Baggs, Senbayram Another explanation variable delayed water ponding temporally inhibits gaseous efflux (Mulvaney Kurtz, 1984) 1. reduction enhanced drains field, causing 2. further, consumption. Studies manure-amended (Coyne 1995; Parker Sänger produce maximum rainfall (0.06 h−1 0.2 h−1) double rate single (0.45 3a). Peak mostly immediately studies, why magnitudes highest work. multi-temporal automated address deficiencies Scheer Waldo Yao 2009), highly instrumented too costly deploy widely. Future determining anticipated deployment measurements. direction correlations 2), drainage, clay contents, level. However, should noted generally weak according data. Validation coverage therefore allow confident mechanisms suggested possible approximate (Nan Toma 2011; Yang Silver, 2016). legitimacy assumption depends balance consumption, limitation (Florio relative (Donoso 1993; Gagnon Meijide Thomas Positive nonmonotonic WFPS, 70–80% 4a) others (Ciarlo Huang results suggest L–1 S1). Other observing relationships (Ball 2003) probably non-limiting negligible (Ruser In contrast, values (linear fit R2 = .005, P suggests played role moisture. Understanding occurs critical. elevation, silt PR, 2). Surprisingly, there correlation NDWI associates leaf content (Tucker, 1980b) chance supported direct influenced (Gao, 1996) flooding reliable indicator (R2 .16, .001) 4b). 2c). abundance differ reflected DOC majority (34%) (44%) 22% occurrences locations elevation slope positively SOM .05), aligned pathways (Del Grosso Gillam pooled together Our agreed Guo (2020), denitrification. see some evidence supporting research (Miller 2012) promotes S1), ratio predictive either covariates, PR .01), NDVI related changing indicate rapidly warm compaction. (r .22) .16) stress coincided focuses efficient trends add create situations availability. rainfall-induced conventional additional survey- sensing-based indicators (drainage class, NDWI). such complicated time, meaning utility depend characteristics strategy moments. Elevation, emissions, whereas smaller finer TN co-occurring degree. considered scrutinized inform management. accounted avoid overestimating N, contents. Inherent dynamic disentangle methods including acetylene (C2H2) suppress (Yoshinari 1977), isotopes trace (Well Flessa, Winther 2018), functional gene markers (narG, nirK, nirS nosZ) relate refine mechanistic one described herein, simpler rely statistical analysis support MZ delineation monitoring area-based weighing specific upscale obtain rainfall. method extended resolution baseline inherent properties. thank Allen Williams generously allowing helping us carry experiments his farms. like acknowledge help interns visiting students Ana Laura Silva de Sousa, AnnaMae Dziallo, Autumn Homles, Jenny Gray, Josh Lim, Junyu Lao, Jeff Roche, Kelly Aves, Mario Nunez, Qianchen Zhou, Qianqian Chen, Shumin Wenyu Liu. Yushu Xia: Conceptualization; Data curation; Formal analysis; Investigation; Methodology; Software; Validation; Visualization; Writing – original draft. Michelle Wander: Funding acquisition; Project administration; Resources; Supervision; review editing. authors declare no conflict interest. S1. NAIP satellite image area experimental emphasized boxes. S2. Boxplots grouped (A) zone (B) S3. Temporal separated location properties (MZs) event. net, positive, Please note: publisher responsible functionality any supplied authors. Any queries (other missing content) directed corresponding author article.