Geoderma 197–198 (2013) 177–185

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Geoderma

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Soil carbon fluxes and balances and soil properties of organically amended no-tillcorn production systems

Raj K. Shrestha ⁎, Rattan Lal, Basant RimalCarbon Management and Sequestration Center, School of Environment and Natural Resources, The Ohio State University, Columbus, OH 43210, USA

⁎ Corresponding author. Tel.: +1 614 688 4937; fax:E-mail address: rajs@vt.edu (R.K. Shrestha).

0016-7061/$ – see front matter. Published by Elsevier Bhttp://dx.doi.org/10.1016/j.geoderma.2013.01.005

a b s t r a c t

a r t i c l e i n f o

Article history:Received 28 March 2011Received in revised form 18 December 2012Accepted 15 January 2013Available online 28 February 2013

Keywords:Soil amendmentsSoil qualityCompostGreenhouse gas emissionManure

The addition of organic amendments is essential for sustainable soil fertility management and crop production, butcan also increase greenhouse gas (GHG) emissions. Thus, understanding the impacts of organic soil amendments ongaseous emissions is pertinent to minimizing agricultural impacts on the net emissions of GHGs. A long-term fieldexperiment was conducted to assess the impacts of continuous application of organic amendments (i.e. compostand farmyard manure) and cover crop [mixture of rye (Secale cereal), red fescue (Festuca rubra), and blue grass(Poa pratensis L.)] on selected soil properties, apparent carbon (C) budget (calculated from the difference of sumof all sources of C inputs and outputs), gaseous flux (i.e. carbon dioxide, CO2, andmethane, CH4), and relationshipwith weather parameters under no-till (NT) corn (Zea mays L.) cultivation in an Alfisol of central Ohio, USA. Soilproperties and gaseous fluxes were measured continuously for 2 years. Ten years of continuous application ofsoil amendments increased soil pH and electrical conductivity, enhanced soil C pool, and decreased bulk densityespecially in 0–5 cm depth than that with cover crop and control plots. Two years average, cattle manure, com-post, fallow, and cover crop emitted 14.1, 10.2, 7.5, and 7.2 MgCO2–C ha−1 yr−1, respectively.Methane emissionwas 10.7 kg CH4–C ha−1 yr−1 from cattle manure and 4.0 kg CH4–C ha−1 yr−1 from compost. However, fallowconsumed 3.3 and cover crop 5.0 kg CH4–C ha−1 yr−1. These data suggest that long-term application of compostin NT corn decreased emissions of CO2 by 38% and of CH4 by 167% compared to application of manuring. Ingeneral, soil temperature, air temperature, and precipitation were positively correlated with CO2 emissions.Estimation of C budget indicated that amended soil under NT is a C-sink while a non-amended system is aC-source. The application of composted soil amendments in NT corn enhances soil quality and reduces netGHG emissions.

Published by Elsevier B.V.

1. Introduction

Soil management practices that increase carbon (C) sequestrationinclude the application of organic amendments, conversion to conser-vation agriculture (CA), cover cropping, and residue retention. Organicamendments (i.e., compost, manure, cover crops) are a source of plantnutrients in addition to improving soil quality. Organic amendmentsimprove soil quality by improving physical (increasing aggregate stabil-ity and reducing bulk density), chemical (increasing soil pH, electricalconductivity, and soil organic carbon — the main source of energy forsoil microorganisms), and biological activity of soils (Diacono andMontemurro, 2011; Duong et al., 2012; Eghball et al, 2004). Improve-ment in soil quality increases crop yield in addition to playing a positiverole in climate change mitigation by sequestering C. Accumulation ofSOC in cropping systems occurs when C additions into soil (from cropresidue and organic amendments) exceed C losses through decomposi-tion, erosion, and leaching. However, depending on their compositionand application methods, these amendments can also contribute to

+1 614 292 7432.

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greenhouse gas (GHG) emissions (Abbas et al., 2012; Andraski et al.,2000; Ding et al., 2007; Heller et al., 2010; N'Dayegamiye and Angers,1990).

Agricultural emissions account for 13.5% of the total anthropogenicgaseous (i.e., CO2, CH4, and N2O) emissions (IPCC, 2007). USEPA (2010)estimated that U.S. agriculture contributes about 427.5 teragrams ofCO2 equivalent (Tg CO2Eq.) or 6% of total U.S. GHG emissions. Agriculturalemissions of CO2 include microbial respiration in bulk soil and rhizo-sphere (Rochette et al., 1999), dissolution of carbonates in calcareoussoils (Bertrand et al., 2007), burning of fossil fuels for agricultural pur-poses, and erosion induced emissions (Lal, 2003). Whereas CH4 is pro-duced in agricultural soils mainly from manure management and rice(Oryza sativa L.) cultivation. The magnitude of GHG emission also de-pends on soil moisture and temperature regimes, soil type, land use,cropping pattern, and type and quantity of organic residues added(Chianese et al., 2009; Johnson et al., 2007; Shrestha et al., 2009). Animalmanure provides readily available C for microbial activities, which canenhance CO2 emissions (Granli and Bockman, 1994; Rochette et al.,2004). The Rothamsted C turnover model indicated an increase inCO2 emissions with an increase in application rate of SOM in a highlyweathered tropical soil in Hawaii (Abbas and Fares, 2009).

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In the U.S., CH4 emissions from manure management increased by54% between 1990 and 2008, from 29.3 Tg CO2Eq. to 45.0 Tg CO2Eq.(USEPA, 2010). A majority of this increase was from swine and dairycow manure. There is a growing trend of using liquid manures, whichproduce greater CH4 emissions. Considerable CH4 efflux occurs in soilswhere methanogenesis is accentuated by anaerobic conditions causedby heavy precipitation and periodic flooding (Yang and Chang, 2001).A study conducted in a silty clay loam soil in West Lafayette, IN undercontinuous corn (Zea mays L.) showed that liquid swine manure,injected at a rate of 255±24 kg Nha−1 yr−1 in the spring or the fall,was the net CH4 emitter (Hernandez-Ramirez et al., 2009). In anotherstudy, application of 42–45 Mg ha−1 yr−1 of beef cattle feedlotmanureand composted dairy manure in a corn–soybean (Glycine max L.) rota-tion with complete corn-stover removal increased SOC concentration(Thelen et al., 2010). The net global warming potential (GWP) for themanure and compost amended cropping systems was −934 and−784 g m−2 yr−1 compared to 52 g m−2 yr−1 for the non-manureamended synthetic fertilizer control (Thelen et al., 2010). In a sandyloam soil in East Lansing, MI, application of compost (16.3 Mg C ha−1)and manure (21.6 Mg C ha−1) resulted in a net GWP of −1811 and−1060 g equivalent CO2m−2 yr−1, respectively (Fronning et al.,2008). However, four years after termination of applying organicamendments in Nebraska, residual effects of manure and compost onCO2, N2O, and CH4 emissions were minimal (Ginting et al., 2003).

Composting and the use of composted products indirectly reduceGHG emissions by reducing demand for and application of mineral fer-tilizers and pesticides (Favoino and Hogg, 2008). Reduction in agricul-tural emissions is possible by adopting recommended managementpractices (RMPs) through enhancing C sequestration, increasing CH4

consumption, and reducing N2O emissions.Data from most field studies are based on measurements of GHG

emissions after years of using organic amendments in NT systems.Limited studies have reported GHG emissions following long-termcontinuous application of amendments under NT systems. Thus, thisstudy is based on the hypothesis that the application of compost toNT corn production systems can increase SOC pool and also reducethe net C loss compared to manuring. The objectives of this studywere to: (1) quantify the effects of long-term continuous applicationof cow manure and compost on CO2 and CH4 emissions, (2) computeannual soil C budget, and (3) identify determinants of CO2 and CH4

under NT corn production systems.

2. Material and methods

2.1. Site description and experimental detail

A long-term field experiment was established in 1997 at the Wa-terman Farm of the Ohio State University, Columbus, Ohio (Elevation241 m.a.s.l., latitude 40°01′N, and longitude 83°02′W). The dominantsoil series at this site is Crosby silt loam (Soil Taxonomy: fine, mixed,mesic Aeric Ochraqualf), a somewhat poorly-drained soil developedfrom glacial till. Located in the humid continental zone, Columbus,Ohio is characterized by a temperate climate. The climate is warmduring the summer, when the average maximum temperature is22 °C, and cold during winter when the average minimum tempera-ture is −1 °C (Fig. 1A). The warmest month is July with an averagemaximum temperature of 29.5 °C, and the coldest is January withan average minimum temperature of −6.5 °C. The annual averageprecipitation is 81 cm. Rainfall is fairly evenly distributed throughoutthe year. The driest month is February with 5.6 cm of rainfall, and thewettest is July with 11.7 cm of rainfall. There were four treatments:compost (mixture hardwood mulch, straw, and horse manure), ma-nure (cow manure), cover crop (no amendments, grasses including50% perennial rye, 30% annual rye, 10% red fescue and 10% bluegrass), and fallow (no amendments, weedy fallow). Compost and ma-nure were applied every year. Cover crops were permanent and no

fertilizer or soil amendments were applied. Weed growth in theweedy fallow plot was similar to cover crop. The experimental designwas a randomized complete block (RCBD) with four replications. Plotsize was 6.1×6.1 m.

Compost was applied manually at the rate of 44 Mg ha−1 in earlyApril. Cow manure was applied in December at the rate of 29 Mg ha−1

using a manure spreader (Kuhn Knight ProTwin Slinger). Carbon con-centrations in manure and compost were 408 and 395 g kg−1, andnitrogen concentrations were 8.8 and 6.7 g kg−1 soil, respectively. Nochemical fertilizers (N, P, K) were applied to the amended plots.Amended plots were planted to NT corn (variety Steyer 1104 RR). Cornwas seeded during the last week of April to early May at the rate of76,000 seeds ha−1 using a NT drill (model 900, CASE IH), and row torow spacing of 75 cm. Urea-N fertilizer was broadcasted manually inthe fallow and the cover crop plots at the rate of 148 kg N ha−1 at thetime of corn emergence in amended plots. Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) was sprayed before plantingcorn at the rate of 4.68 l per ha. Glycophosate [N-(phosphonomethyl)glycine] was applied at the rate of 2.34 l per ha when corn plants were20 cm high. A tractor-mounted sprayer (Huskee 200 gal) was used toapply pesticides. Corn was harvested in early October by using a 6-rowgrain harvester (International 1440 Combine). Residues (i.e., stover,cobs, and husks) were left in the field.

2.2. Soil sampling, processing, and analyses

Soil and core samples were obtained from the plots at 0–5, 5–15,and 15–30 cm depths in December, 2006. Three soil samples,obtained from each plot, were bulked depth-wise, to make compositesamples for each replication. The composite soil samples wereair-dried under shade. Large clods were gently crushed, stones re-moved, and soil sieved through a 2-mm sieve. The sieved soil wasused to measure pH in 1:1 soil/water extract using a thermo ScientificOrion StarTM Series Meter (Thermo Fisher Scientific Inc., Beverly,MA), and electrical conductivity in 1:5 soil/water extracts (Rhoades,1996). Soil texture was determined by the hydrometer method (Geeand Or, 2002). About 10 g of a composite subsample (b2 mm) wasfurther ground using a ball mill and sieved through a 250-μm sievefor the determination of total C and N concentrations by the dry com-bustion method using a vario MAX CN analyzer (Elementar, Hanau,Germany). The carbonate test with 1 M HCl was negative. Therefore,total C was assumed to be equal to the SOC. Soil bulk density (ρb) wasdetermined on intact soil cores from all three depths at the same loca-tion from where the composite samples were collected (Grossmanand Reinsch, 2002). Cores with the dimension of 5.3 cm in diameterand 3 cm in length were used for 0 to 5 cm depth, and 5.3 cm in diam-eter and 6 cm in length for 5 to 15, and 15 to 30 cm depths. Core sam-ples were collected from the middle of each depth increment torepresent ρb for the depth, and soil moisture content was measuredby drying at 105 °C for 48 h. Soil sample inside the core was recoveredand passed through a 2-mm sieve to determine the gravel content. Soilρb data was reported in Mg m−3 after making correction for the gravelcontent >2 mm (Page-Dumroese et al., 1999). Soil samples were col-lected again in December 2008 at 0–5, 5–15, and 15–30 cm depthsand analyzed for C concentration to compute C budget. Carbon concen-trations in the experimental site ranged from 31 to 53 mg g−1, claycontent 167 to 219 g kg−1, and bulk density 0.82 to 1.26 Mg m−3

(Table 1).

2.3. Gas flux measurements and calculations

The GHG fluxes were measured using the manual closed staticchamber technique. The details about the size and shape of chambersand lids are discussed by Shrestha et al. (2009). Chambers, made ofpolyvinyl chloride (PVC), were installed one month before the fluxmeasurement to avoid the effects of soil disturbances and potential

Fig. 1. Daily (A) average air-temperature and precipitation, (B) carbon dioxide (CO2), and (C) methane (CH4) fluxes during March, 2007 to February, 2009. Vertical bars representLSD (0.05) values for treatment comparison within given sampling date at Pb0.05.

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changes in CO2 and CH4 fluxes. Chambers were inserted 10 cm into theground, leaving 15 cm above ground. Two gas chambers were installedin each plot, giving a total of 6 replications (three replications×twochambers per replication). Fluxes of CO2 and CH4 were measured bycollecting soil–air samples about bi-weekly from March 20, 2007 toFebruary 26, 2009. Less frequent measurements were made duringthe dormant winter season. Chambers were left open in the field forthe entire two year sampling period to mimic the natural environment,except during the farm operations. Chambers were kept free of anyplants for the entire two year period, and therefore, CO2fluxes representsoil respiration. A lid, also made of PVC material, was used to close thechamber at the time of soil–air sampling. Immediately after coveringwith the lid, soil–air sampleswerewithdrawn fromeach chamber head-space with a 20 ml syringe and were labeled as zero-minute samples.Subsequent soil-air samples were collected 30- and 60-minutes afterreplacing the lid. They were then transferred to the crimp-sealedpre-evacuated (b0.05 kPa) 10 ml vials. Soil–air samples were also col-lected from outside of the chamber, immediately after zero minutesampling from the chamber, to correct the impact of the chamber, ifany. They were obtained between 11:00 and 15:00 h, when the diurnaltemperature variation is minimal (Bajracharya et al., 2000; Benasher etal., 1994). The sequence of the gas samplingwas randomized every timeto avoid bias caused by changes in air temperature during the samplingperiod. Samples were analyzed for CO2 and CH4 concentration using aShimadzu GC-14A gas chromatograph equipped with a thermal con-ductivity detector (TCD, at 100 °C for CO2 detection) and a flame ioniza-tion detector (FID, at 150 °C for CH4 detection). Heliumwas used as the

carrier gas at theflow rate of 20 mL min−1. The gas chromatographwascalibrated using standard gas obtained from Alltech (Deerfield, IL).

Daily fluxes of CO2 (F, g CO2–C m−2d−1) and CH4 (F, mgCH4–C m−2d−1) were computed using the Eq. (1):

F ¼ ΔgΔt

� �VA

� �k ð1Þ

where, Δg/Δt is the linear change in soil–air concentration inside thechamber (i.e. g CO2–C m−3 min−1 or mg CH4–C m−3 min−1), V is thechamber volume (m3), A is the surface area covered by the chamber(m2), and k is the time conversion factor (1440 min day−1).

Changes in headspace gas concentration with time were tested fornonlinearity as suggested by Rochette and Eriksen-Hamel (2008) andKroon et al. (2008). Cumulative soil fluxes were calculated by sum-ming the averaged product of the two neighboring fluxes, multipliedby number of days of sampling interval. Annual fluxes were calculat-ed by summing the weighted daily fluxes over a year. The negativefluxes of GHG indicate the uptake of a given gas by soil and positivefluxes indicate the net emissions from soil.

2.4. Collection of weather data and measurement of soil moisture andtemperature

Soil temperatures at 10 and 20 cm soil depths were monitorednear each chamber simultaneously with gas sampling using a ther-mocouple Thermometer (YO-91210-45, Cole-Parmer ®). Gravimetric

Table 1Effects of cover crop, compost and manure on soil pH, electrical conductivity (EC), bulkdensity (BD), sand and silt content, Nov. 2006.

Soil properties Treatment Soil depth (cm) LSD 0.05

0–5 5–15 15–30

pH Fallow 6.4 6.3 6.6 0.4Cover crop 5.6 5.7 6.1 0.4Compost 6.9 6.2 6.5 0.6Manure 6.8 6.4 6.4 0.4LSD 0.05 0.6 0.9 0.7

EC (μS cm−2) Fallow 89 64 53 34Cover crop 57 33 33 13Compost 185 55 40 66Manure 166 70 49 14LSD 0.05 54 50 36

Carbon concentration (mg g−1) Fallow 28.9 24.6 22.1 2.9Cover crop 35.1 26.7 24.8 5.4Compost 53.0 28.7 23.6 11.4Manure 46.9 29.4 24.8 5.6LSD (0.05) 5.9 5.5 6.5

Carbon pool (Mg ha−1) Fallow 18.0 34.0 46.3 7.8Cover crop 21.0 35.5 48.3 12.1Compost 22.2 39.5 50.5 12.2Manure 24.5 40.6 51.4 14.4LSD (0.05) 3.8 7.4 11.7

C/N Fallow 11.3 11.5 11.8 1.7Cover crop 11.6 11.1 11.0 0.6Compost 13.4 11.4 11.0 0.9Manure 10.9 10.9 11.0 2.8LSD (0.05) 0.5 0.9 1.7

BD (Mg m−3) Fallow 1.26 1.40 1.41 0.13Cover crop 1.21 1.34 1.35 0.12Compost 0.82 1.40 1.48 0.19Manure 1.05 1.40 1.42 0.16LSD 0.05 0.21 0.08 0.08

Sand (g kg−1) Fallow 418 426 397 114Cover crop 430 376 426 29Compost 462 409 416 101Manure 457 437 403 24LSD 0.05 132 166 29

Clay (g kg−1) Fallow 197 212 253 15Cover crop 219 253 259 18Compost 167 231 239 43Manure 217 257 247 65LSD 0.05 80 107 110

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soil moisture content was also determined by collecting soil samplesclose to the chambers at 0–10 cm depth. Soil samples for moisturecontent and air and soil temperature measurements were made bi-weekly for two years in conjunction with soil–air sampling. The weath-er data on daily rainfall and daily average temperaturewere recorded ata nearby weather station at the Waterman farm (~400 m), which wascompiled by the Ohio Agricultural Research and Development Center(OARDC). Rainfall and temperature data from 9/12/2007 to 3/5/2009were obtained from OARDC Weather System (2011). Missing datafrom 3/1/2007 to 9/11/2007, not available in OARDC Weather System,were obtained from the National Climatic Data Center (2011).

2.5. Apparent carbon budget

Apparent carbon budget was calculated from the difference in sumof all sources of C inputs and outputs (Eq. (2)). Inputs included Cadded from compost, manure, cover crops, and weeds in fallow plotand the antecedent soil C pool. Outputs included C loss as CO2–C, Charvested in grains, and any change in the final soil C pool. Carbongain or loss as CH4–C was insignificant and therefore not included inthe budget calculations. Initial and final soil C pools were estimatedto a depth of 30 cm. Carbon sequestration rates were calculated bysubtracting initial soil C pool from final and dividing by number of

years between initial and final soil C pool measurement. Carbonbudget was calculated using the following Eq. (2).

C budget ¼X

Cinputs−X

Coutputs: ð2Þ

Amount of the amendment applied was estimated using a0.5 m×0.5 m metal frame. The samples were collected from threeframes within each plot and weighed to determine the total freshweight. Six random sub-samples were collected for moisture determi-nation after drying them in an oven at 50 °C to a constant weight inorder to compute the dryweight of the amendment applied. Dried com-post and manure samples were ground and sieved through a 250-μmsieve for the determination of the C and N concentrations using avario MAX C-N analyzer. Three random weed and cover crop biomasssamples were also collected from each plot using a 0.5×0.5 m metalframe. These samples were dried in an oven at 50 °C to calculate thedry biomass weight of weeds and cover crops. The gaseous loss of Cfrom different treatments was estimated by monitoring CO2 and CH4

fluxes throughout the two year period, as discussed earlier, and cumu-lative annual C loss as CO2 and CH4, assumed to be respiratory C losswasestimated. Corn residues were returned back to soil. Therefore, onlycorn grains were considered as an output. Ground grain samples wereused for the determination of C concentrations using a vario MAX CNanalyzer (Nelson and Sommers, 1973).

2.6. Statistical analysis

The daily, annual, and cumulative CO2 and CH4 fluxes and soilmoisture and temperature regimes for each sampling date were ana-lyzed using the GLM procedure available in SAS 9.2 for Windows(2002–2008 by SAS Institute Inc., Cary, NC, USA.) to detect the effectsof the amendment applications. Similarly, C balance and selectedphysical and chemical properties of soil were also analyzed usingthe PROC GLM test at 95% confidence level. Means were separatedusing the least square significance test. Soil temperature andmoistureregimes in each treatment were correlated with CO2 and CH4 fluxesfor each treatment. Precipitation and air-temperature were also cor-related with CO2 and CH4 fluxes for each individual treatment.

3. Results and discussion

3.1. Effects of soil amendment application

3.1.1. Changes in soil properties after ten yearsContinuous application of soil amendments (compost and ma-

nure) for ten years to NT corn significantly affected soil properties(Table 1). Application of compost and manure significantly increasedsoil pH towards neutral compared to cover crop. However, increase inpH was significant only in the 0–5 cm depth. Soil EC was two to threetimes higher in compost (185 μS cm−2) and manure (166 μS cm−2)applied corn treatments than in fallow (89 μS cm−2) and cover crop(57 μS cm−2). Other studies (Ouédraogo et al., 2001) have alsoreported similar increase in soil pH and electrical conductivity withcompost application. At 0–5 cm depth, the SOC concentration in com-post increased by 58–71% compared to fallow and cover crop. Similar-ly at 0–5 cm depth, bulk density decreased by 35% because ofcompost application than without compost. Similar observation of adecrease in bulk density with compost application was also madeby D'Hose et al. (2012). Manuring increased SOC pool in the 0–30 cm depth by 29% compared with weedy fallow. However, a signif-icant increase in SOC pool at all depths was observed only with ma-nure application. Although C concentration was high in 0–5 cmdepth of compost applied soil, the SOC pool did not differ fromthose under fallow and cover crop because of a drastic decrease inρb. The SOC pool in 30 cm depth of manure (119 Mg ha−1) applied

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corn was 30% higher than that under fallow (92 Mg ha−1) and 16%higher than that under compost (103 Mg ha−1). Application of com-post increased SOC pool by 12% compared to that under fallow. Im-provement in SOC sequestration and decrease in ρb with compostapplication was also observed in a gravelly-clay soil in Hawaii(Abbas and Fares, 2009) and silty clay loam soil of China (Li et al.,2012).

3.1.2. Carbon dioxide fluxSoil CO2 flux differed among seasons, increasing gradually from early

spring, reachingmaxima during late spring to early summer at the peakof corn growth, gradually declining in the fall, and reachingminima dur-ing winter (Figs. 1B). Two sources of CO2 flux are decomposition of SOMand root respiration. Averaging the two year's worth of data from alltreatments, 49% of the total annual CO2 emission occurred during spring,32% during summer, 11% duringwinter, and 9% during fall. Fluxes of CO2

increased with increase in soil- and air-temperatures during spring(Figs. 1B and 2) and with corn growth. Flux of CO2 was low from latefall through early spring when the ground was mostly frozen. Althoughfluxes were generally low during frozen conditions in winter, fluxesfrom amendment applied soils in 2007–2008 were significantly higherthan those from non-amended soil. Soil microorganisms maintain bothcatabolic (CO2 production) and anabolic processes (biomass synthesis)under frozen conditions (Drotz et al., 2010). Thus, gaseous exchange be-tween the atmosphere and soil does not stop even under frozen soil,resulting in the accumulation of CO2 during winter and its release into

Fig. 2. Effects of compost, cover crop and manure on (A) soil temperature at 10 cm depth (resent LSD values at 0.05 confidence level for each sampling date.

the atmosphere during spring thaw events (Burton and Beauchamp,1994). The amount of amendment-induced CO2 flux varied amongyears, with themost notably large fluxmeasured in 2007–2008. Contin-uous application of soil amendments increased soil CO2 flux comparedto un-amended because of the readily decomposable C substrate fromorganic amendments (Rochette et al., 2006). For most of the samplingthroughout a 2-yr study period, daily soil CO2 fluxes were significantlyhigh with manure application. The average daily CO2 flux was thehighest in manure (3.81 g CO2–C m−2d−1), followed by that in com-post (2.79 g CO2–C m−2d−1), cover crop (2.16 g CO2–C m−2d−1),and fallow (2.07 g CO2–C m−2d−1) treatment. A possible explanationfor the higher CO2 flux observed in manure plot compared to compostplot may be due to a higher carbon concentrations in the former(408 g kg−1 soil) than in the latter (395 g kg−1 soil).

The largest CO2flux recorded during themonitoring period occurredin manure (16.7 g CO2–C m−2d−1) applied plot followed by the com-post (10.5 g CO2–C m−2d−1) treatment on June 4, 2007. This fluxrate is similar to the largest CO2 flux (17.9 g CO2–C m−2d−1) reportedby Adviento-Borbe et al. (2010). In both years, cumulative soil CO2

fluxes were higher for cattle manure followed by compost, fallow, andcover crop treatments (Fig. 3). Cumulative CO2 fluxes from compost ap-plication were significantly lower than those from manure treatment.The cumulative CO2 flux in 2007–2008 was higher than in 2008–2009,which was due to a large peak of 16.7 g CO2–C m−2d−1 from manureapplied soil and 10.5 g CO2–C m−2d−1 from compost treatment onJune 4, 2007. Long-term applications of soil amendments significantly

B) 20 cm depth, and (C) soil gravimetric moisture content at 0–10 cm depth. Bars rep-

Fig. 3. Cumulative carbon dioxide and methane fluxes affected by compost, cattle manure, cover crops, and fallow in no-till corn from 2007 to 2009.

182 R.K. Shrestha et al. / Geoderma 197–198 (2013) 177–185

and consistently increased CO2 emissions during both 2007–2008 and2008–2009 compared to un-amended treatments (Fig. 3). Higher CO2

flux from organically amended versus non-amended treatment maybe attributed to the combined effects of available C substrate (Aduand Oades, 1978), soil temperature and moisture regimes (Howardand Howard, 1993; Smith et al., 2003), aeration and gas diffusivity(Fang andMoncrieff, 1999; Gregorich et al., 2006), and increasedmicro-bial activity (Rochette et al., 2000). The data from the present study in-dicate that application of soil amendments increased soil moisturecontent (annual average 340–370 g kg−1) and decreased soil tempera-ture (annual average 12.7–14.6 °C) compared to un-amendment treat-ments (240–260 g kg−1, 14.8–15.2 °C) (Fig. 2). Annual CO2 emissionin 2007–2008 was significantly higher (46.8%) from manure-appliedsoil than that from the compost treatments. High SOC pool in manure(119 Mg ha−1) applied soil compared to compost (103 Mg ha−1) treat-ment may be one of the factors leading to high CO2 emissions. Mean an-nual CO2 emissions were 14.1, 10.2, 7.5, and 7.2 Mg ha−1 yr−1, andmean seasonal (corn growing season: the last week of April to thefirst week of October) CO2 emissions were 10.8, 8.3, 6.4, and6.0 Mg ha−1 season−1 from cattle manure, compost, fallow, and covercrop treatment, respectively. Adviento-Borbe et al. (2010) reportedCO2 emission of 9.4 MgC ha−1 growing season−1 for corn that receivedliquid dairy manure in silt loam soil. Annual CO2 emission of 9.7 MgCO2–C ha−1 yr−1 was reported from corn treated with pasteurizedchicken manure at the rate of 10 Mg ha−1 yr−1 in sandy loam soil(Heller et al., 2010), and 13.3–15.3 Mg CO2–C ha−1 yr−1 that receivedcattle manure at the rate of 20 Mg ha−1 (fresh weight) in sandy soil(Matsumoto et al., 2008). However, Ding et al. (2007) reported amuch lower annual emission of 4.01 Mg CO2–C ha−1 yr−1 forcorn and wheat cropping systems that received composted manurein a sandy loam soil. High annual emissions in the present studymay be due to a higher C input from compost (17 Mg ha−1) andmanure (12 Mg ha−1) than that applied by Ding et al. (2007)(2.8 Mg ha−1).

3.1.3. Methane fluxBoth CH4 production and consumption were observed during the

2-yr measurement period. This (Fig. 1C) and other studies (Hernandez-Ramirez et al., 2009; Jarecki andLal, 2006; Shrestha et al., 2009; Yao et al.,2009) show that CH4 fluxes are characterized by a high temporal vari-ability. Therefore, there are no clear trends in cropland soils in CH4 fluxes(non-waterlogged). Because of the high variability in CH4 flux, differ-ences between treatments are mostly insignificant. A positive CH4 flux(emissions) dominated in the amended soils and negative (consump-tion) in the un-amended treatment. Of the 30 sampling dates, CH4 emis-sions were recorded for 20 sampling dates in manure and 16 incompost-amended soils. Similar trends were reported by Jarecki et al.(2008). Long-term application of manure inhibits CH4 consumptionand increases its production. Inhibition of CH4 oxidation is due to thepresence of NH4 that is toxic to CH4-oxidizing bacteria (Hutsch, 2001).Additionally, increase in CH4 production in amended soils is also dueto the availability of substrate (acetate) from fermentation of organicmatter (Meixner and Eugster, 1999). Of 30 sampling dates, CH4 con-sumption in un-amended soils was recorded for 19 sampling dates incover crop and 21 in the fallow treatment. The rate of CH4 oxidation insoil is influenced by diffusion of the gas to the microorganisms. Dailymethane fluxes ranged from −3.57 to 6.91 mg CH4–C m−2d−1 in ma-nure, −2.44 to 4.63 mg CH4–C m−2d−1 in compost,−4.48 to 2.49 mgCH4–C m−2d−1 in cover crop, and −6.90 to 2.32 mg CH4–C m−2d−1

in the fallow treatment. Cumulative CH4 emissions were observed untilthe fall of 2007–2008 and during all of the 2008–2009 year in manuredtreatment (Fig. 3), but consumption was observed only during 2007–2008 in compost-amended plots. Also during 2008–2009, CH4 emissionswere observed in compost-applied field but insignificantly less quanti-ties than those from the manured treatment. In non-amended covercrop and fallow soils, cumulative CH4 consumptions were observedthroughout the 2-year study period.

The data of annual net flux for both years showed that amendedsoils have net CH4 emissions and non-amended soils have net

183R.K. Shrestha et al. / Geoderma 197–198 (2013) 177–185

consumption (Fig. 3). Net annual CH4 fluxes did not differ amongtreatments in 2007–2008, but did in 2008–2009. Net annual emis-sions were 10.7 kg CH4–C ha−1 yr−1 from manure-amended and4.0 kg CH4–C ha−1 yr−1 from compost-amended treatments. Netannual consumptions were 3.3 kg CH4–C ha−1 yr−1 in cover cropand 5.0 kg CH4–C ha−1 yr−1 in the fallow treatment. Similarly,Hernandez-Ramirez et al. (2009) also reported emissions (0.16 to0.33 kg ha−1 yr−1) from a soil amended with liquid swine manure,andCH4 consumption (−0.13 to−0.18 kg ha−1 yr−1) in non-amendedsilt loam soils. When soil under CA system (consisting of non-inversionin-row sub-soiling andwinter cover crops)was amendedwith dairyma-nure (at a rate of 10 Mg ha−1), it emitted 2.7 kg CH4–C ha−1 yr−1

(Gacengo et al., 2009).

3.1.4. Carbon budgetAfter ten years of continuous soil amendment application, SOC

pools in 0–15 cm soil depth were 65, 62, 56, and 52 Mg C ha−1 inmanure, compost, cover crop, and fallow treatments, respectively.We also calculated SOC pools for the same 0–15 cm depths basedon equivalent soil mass approach (Ellert and Bettany, 1995) andwhich were 80, 78, 69 and 61 Mg ha−1. Trend was similar with bothapproach but the amount was higher with equivalent soil mass ap-proach by 17 to 22%. C sequestration rates for manure, compost, covercrop and fallow plots were 1.2, 1.0, 0.9 and 0.8 Mg C ha−1 yr−1, respec-tively (Table 2). Although treatment comparison of relative CO2 fluxmeasurement using the static chamber method is valid and frequentlyused (Adviento-Borbe et al., 2010; Bender and Wood, 2007; Gao et al.,2001; Thornton and Valente, 1996), there is some degree of uncertaintyin the absolute valuesmeasured. Themagnitude of the calculated annualCO2 flux in this study (7.3 to 14.1 Mg ha−1 yr−1) is within the range ofthe published annual flux (2.0 to 18.5 Mg ha−1 yr−1) (Adviento-Borbeet al., 2010; Gacengo et al., 2009; Hernandez-Ramirez et al., 2009). An-nual C loss as CO2 was 3.8, 2.8, 2.0, and 2.1 Mg C ha−1 (average of twoyears) in manure, compost, cover crop, and fallow plots, respectively.Annual soil C gain or loss as CH4 was insignificant, and therefore not in-cluded in the C budget calculations. The C budget estimations indicatedthat there was a positive balance in amended soils, indicating a net gainof C, and a negative balance in non-amended soils, indicating a net loss.However, Duiker and Lal (2000) reported negative C budget even for thecrop residue-C applied plot (6.61 Mg ha−1). The positive budget ob-served in the present study may be due to high amendment-C appliedas compost (17 Mg C ha−1 yr−1) and manure (12 Mg C ha−1 yr−1).These results also show that, even after accounting for the grain harvest,amended NT corn ecosystem is a net C-sink of 10.5 Mg C ha−1 yr−1 forcompost and 3.7 Mg C ha−1 yr−1 for manured treatments. The largeinput of compost-C and smaller loss through respiration (as CO2) con-tribute to the large C sink in compost-amended systems (Table 2). How-ever, non-amended systems are a C-source of 1.3 Mg C ha−1 yr−1 forcover crop and 1.5 Mg C ha−1 yr−1 for fallow, which does not corre-spond with the measured SOC content with a C sequestration rate of0.9 Mg C ha−1 yr−1 for the cover crop and 0.8 Mg C ha−1 yr−1 for

Table 2Apparent carbon budget affected by soil management.

Treatment Input Output

Initial soil Ca C from treatment Final soil Ca Annual C loss

2006 2007/2008 2008/2009 2008 2007/2008

(Mg ha−1) (Mg ha−1) (Mg ha−1) (Mg ha−1) (Mg ha−1)

Fallow 98.3 1.5 1.4 99.9 2.37Cover crops 104.8 1.6 1.7 106.7 2.13Compost 112.2 17.0 17.0 114.2 3.41Manure 116.5 12.0 12.0 119.0 4.99

a Soil C pool is for 0–30 cm depths.

the fallow treatment. Bono et al. (2008) reported a C balance at equilib-rium for un-amendedNT loamy soil in semiarid region in Argentina. Theapproach in the present study of estimating C budget does not accountfor any effects of earthworm feeding and burrowing activities, anddepths of soil sampled for estimating the SOC pool. It is assumed thatthe gain or loss of C through earthworm activities may not have any sig-nificant impact, and a soil depth of 30 cm is appropriate to estimatingthe C pool in amended soils. Hollinger et al. (2005) reported that, ac-counting for 100% grain harvest, NT corn ecosystem was a net sink of1.84 Mg C ha−1 yr−1 while soybean crop was a net source of 0.94 MgC ha−1 yr−1. A lower C-sink in corn and a C-source in soybean inHollinger et al. (2005)'s report in comparison with the present studymay be due to the absence of C input from amendments in the formerexperiment.

3.2. Effects of soil temperature, soil moisture, precipitation, and airtemperature on CO2 and CH4 fluxes

In general, soil temperatures at 10 and 20 cm depths were posi-tively correlated with CO2 fluxes (Table 3; P=b0.01, n=120). A sim-ilar positive relationship between CO2 fluxes and soil temperatureswas also observed in earlier studies in central Ohio (Duiker and Lal,2000; Jarecki and Lal, 2006; Shrestha et al., 2009) and elsewhere(Adviento-Borbe et al., 2010; Ding et al., 2007; Fortin et al., 1996;Hernandez-Ramirez et al., 2009; Rochette and Gregorich, 1998).However, Alluvione et al. (2010) did not observe a significant impactof soil temperature on CO2 fluxes at Turin, Italy, probably due to anarrow range of soil temperatures (between 20 and 30 °C). In thepresent study, the relationship between soil temperatures and CO2

fluxes was strong in compost-amended treatments (P=b0.01, n=30, R2=0.317), weak in cover crop (P=b0.05, n=30, R2=0.128)and fallow (P=b0.05, n=30, R2=0.165) treatments, and non-existent in manure-amended treatments. Increase in CO2 flux with in-crease in soil temperature in compost-amended treatment may bedue to increase in root growth and enhanced decomposition ofSOM. In contrast to CO2 flux, soil temperatures have no impact onCH4 fluxes, possibly because of a large variability in CH4 fluxes. Fur-thermore, CO2 and CH4 fluxes were not related to seasonal variationin soil moisture at 0–10 cm depth. In general, soil moisture contentinfluenced CO2 flux during the corn growing season (April to October)(Pb0.01, R=0.303, n=76), but not in the dormant season (NovembertoMarch). In contrast,Matsumoto et al. (2008) observed that CO2 emis-sions were correlated with soil moisture content during the dormantseason but not during the corn-growing season. The present studyalso shows that precipitation and air temperatures, averaging datafrom three days before flux measurement, are positively correlatedwith the CO2flux. Borken et al. (2003) also observed the effect of rainfallevents on gaseous emissions because increasing soil temperature andrainfall stimulates microbial activities (Kirschbaum, 1995). However,CH4 fluxes from manure-amended soil were positively correlated withprecipitation (Pb0.05).

C budget (input–output) (Mg ha−1 yr−1)

as CO2 C in harvested grain

2008/2009 2007 2008

(Mg ha−1) (Mg ha−1) (Mg ha−1)

1.72 0.00 0.00 −1.51.88 0.00 0.00 −1.32.15 3.12 2.28 10.52.69 3.44 2.94 3.7

Table 3Correlation coefficient (R2) of precipitation, air temperature, soil temperature and moisture with carbon dioxide and methane fluxes for different treatments.

C flux in different treatments Soil temperature Soil moisture Precipitationa Air temperaturea

Compost Manure Cover crop Fallow Compost Manure Cover crop Fallow

CO2 Compost 0.317** −0.107 0.142* 0.361**Manure 0.098 0.276** 0.141*Cover crop 0.128* 0.190** 0.159*Fallow 0.165* −0.012 0.440** 0.198**

CH4 Compost 0.023 0.001 0.068 0.005Manure 0.003 0.005 0.161* 0.010Cover crop 0.018 0.026 −0.008 0.006Fallow 0 −0.095 0.002

a Precipitation and air-temperature values averaged for flux sampling days plus three days early * and ** significant at P=b0.05 and P=b0.01, respectively.

184 R.K. Shrestha et al. / Geoderma 197–198 (2013) 177–185

4. Conclusions

Application of soil amendments under no-till systems significantlyimpacted the soil carbon budget and gaseous emissions. Long-termapplication of soil amendments improved soil quality by increasingpH, raising electrical conductivity, enhancing soil carbon concentra-tion, and decreasing bulk density. It also accentuated CO2 and CH4

emissions. Increase in CO2 and CH4 emissions was large in manuredtreatments compared to those receiving compost. Soils receivingcompost and manure were C-sinks, and others were C-sources.Compost-amended soils had a large net C balance in no-till corn dueto less gaseous loss of C as CO2 and CH4 compared to that ofmanure-amended systems. The data suggests that manuring ano-till corn field may accentuate gaseous emissions.

Acknowledgments

This project was partly funded by the US Department of Energythrough the Midwest Regional Carbon Sequestration Partnership pro-ject led by Battelle Columbus, OH. The authors would like to thankNicholas Johnson, Research Assistant and ColinWaldman, Student As-sistant for field and laboratory assistance.

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