measurement-greenhouse-gas-flux-from-agricultural-soils-using-static

Measurement of Greenhouse Gas Flux from Agricultural Soils Using Static Chambers

Measurement of greenhouse gas (GHG) fluxes between the soil and the atmosphere, in both managed and unmanaged ecosystems, is critical to understanding the ...

University of Wisconsin-Madison

Artificial subsurface drainage is commonly used in midwestern agriculture and drainage losses of dissolved organic carbon (DOC) from such systems are an under-quantified portion of the terrestrial carbon (C) cycle. The objectives of this study were to determine the effect of common agricultural management practices on DOC losses from subsurface tile drains and to assess patterns of loss as a function of year, time of year, and drainflow. Daily drainflow was collected across six water years (1999-2004) from a restored prairie grass system and cropping systems which include continuous corn (Zea mays L.) and corn-soybean [Glycine max (L.) Merr.] rotations fertilized with urea-ammonium-nitrate (UAN) or swine (Sus scrofa) manure lagoon effluent. The DOC concentrations in tile drainflow were low, typically <2 mg L(-1). Yearly DOC losses, which ranged from 1.78 to 8.61 kg ha(-1), were not affected by management practices and were small compared to organic C inputs. Spring application of lagoon effluent increased yearly flow-weighted (FW)-DOC concentrations relative to other cropping systems in three of the years and increased monthly FW-DOC concentrations when drainflow occurred within 1 mo of application. Drainflow was significantly and positively correlated with DOC loss. Drainflow also affected DOC concentrations as greater 6-yr cumulative drainflow was associated with lower 6-yr FW-DOC concentrations and greater daily drainflow was associated with higher daily DOC concentrations. Our results indicate that lagoon effluent application and fertilizer N rates do not affect long-term losses of DOC from tile drains and that drainflow is the main driver of DOC losses.

Dissolved organic carbon losses from tile drained agroecosystems.

Water quality concerns have arisen related to rice (Oryza sativa L.) field drain water, which has the potential to contribute large amounts of dissolved organic carbon (DOC) and total dissolved solids (TDS) to the Sacramento River. Field-scale losses of DOC or TDS have yet to be quantified. The objectives of this study were to evaluate the seasonal concentrations of DOC and TDS in rice field drain water and irrigation canals, quantify seasonal fluxes and flow-weighted (FW) concentrations of DOC and TDS, and determine the main drivers of DOC and TDS fluxes. Two rice fields with different straw management practices (incorporation vs. burning) were monitored at each of four locations in the Sacramento Valley. Fluxes of DOC ranged from 3.7 to 34.6 kg ha(-1) during the growing season (GS) and from 0 to 202 kg ha(-1) during the winter season (WS). Straw management had a significant interaction effect with season, as the greatest DOC concentrations were observed during winter flooding of straw incorporated fields. Fluxes and concentrations of TDS were not significantly affected by either straw management or season. Total seasonal water flux accounted for 90 and 88% of the variability in DOC flux during the GS and WS, respectively. Peak DOC concentrations occurred at the onset of drainflow; therefore, changes in irrigation management may reduce peak DOC concentrations and thereby DOC losses. However, the timing of peak DOC concentrations from rice fields suggest that rice field drainage water is not the cause of peak DOC concentrations in the Sacramento River.

Seasonal losses of dissolved organic carbon and total dissolved solids from rice production systems in northern California.

Artificial subsurface drainage in cropland creates pathways for nutrient movement into surface water; quantification of the relative impacts of common and theoretically improved management systems on these nutrient losses remains incomplete. This study was conducted to assess diverse management effects on long-term patterns (1998-2006) of NO, NH, and PO loads (). We monitored water flow and nutrient concentrations at subsurface drains in lysimeter plots planted to continuous corn ( L.) (CC), both phases of corn-soybean [ (L.) Merr.] rotations (corn, CS; soybean, SC), and restored prairie grass (PG). Corn plots were fertilized with preplant or sidedress urea-NHNO (UAN) or liquid swine manure injected in the fall (FM) or spring (SM). Restored PG reduced NO eightfold compared with fields receiving UAN (2.5 vs. 19.9 kg N ha yr; < 0.001), yet varying UAN application rates and timings did not affect NO across all CCUANs and CSUANs. The NO from CCFM (33.3 kg N ha yr) were substantially higher than for all other cropped fields including CCSM (average 19.8 kg N ha yr, < 0.001). With respect to NH and PO, only manured soils recorded high but episodic losses in certain years. Compared with the average of all other treatments, CCSM increased NH in the spring of 1999 (217 vs. 680 g N ha yr), while CCFM raised PO in the winter of 2005 (23 vs. 441 g P ha yr). Our results demonstrate that fall manuring increased nutrient losses in subsurface-drained cropland, and hence this practice should be redesigned for improvement or discouraged.

Article	Year
Dissolved organic carbon losses from tile drained agroecosystems. Journal of environmental quality\| PubMed ID: 19398518	2009
Seasonal losses of dissolved organic carbon and total dissolved solids from rice production systems in northern California. Journal of environmental quality\| PubMed ID: 20048318	2010
Nitrate, phosphate, and ammonium loads at subsurface drains: agroecosystems and nitrogen management. Journal of environmental quality\| PubMed ID: 21712592	2011

Matthew D. Ruark

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