Crop residues in corn-wheat rotation in a semi-arid region increase CO2 efflux under conventional tillage but not under no-tillage system

Pedobiologia - Jou nal o Soil Ecology 93–94 (2022) 150819 A ailable online 16 June 2022 0031-4056/© 2022 The Au ho (s). Published by Else ie GmbH. This is an open access a icle unde he CC BY license (h p://c ea i ecommons.o g/licenses/by/4.0/). C op esidues in co n-whea o a ion in a semi-a id egion inc ease CO 2 e lux unde con en ional illage bu no in a no- illage sys em Mo ad Mi zaei a , * , Manoucheh Go ji Ana i a , Ehsan Raza y-Toosi b , Mohammad Zaman c , Ne mina Sa onjic d , Seyed Mo eza Zami e , Sa wan Mohammed , And ´ es Caballe o-Cal o g , * a Depa men o Soil Science and Enginee ing, Facul y o Ag icul u al Enginee ing and Technology, Uni e si y o Teh an, Ka aj, I an b Depa men o Plan , Soil and Mic obial Sciences, Michigan S a e Uni e si y, MI, USA c Soil and Wa e Managemen & C op Nu i ion Sec ion, Join FAO/IAEA Cen e o Nuclea Techniques in Food & Ag icul u e, Depa men o Nuclea Sciences and Applica ions, In e na ional A omic Ene gy Agency, Vienna, Aus ia d Ins i u e o Soil Resea ch, Depa men o Fo es and Soil Sciences, Uni e si y o Na u al Resou ces and Li e Sciences (BOKU), Vienna, Aus ia e Facul y o Chemical Enginee ing, Ta bia Moda es Uni e si y, Teh an, I an Ins i u e o Land U iliza ion, Technology and Regional Planning, Facul y o Ag icul u al and Food Sciences and En i onmen al Managemen , Uni e si y o Deb ecen, Deb ecen, Hunga y g Depa men o Regional Geog aphical Analysis and Physical Geog aphy, Facul y o Philosophy and Le e s, Campus Uni e si a io de Ca uja, Uni e si y o G anada, 18071 G anada, Spain ARTICLE INFO Keywo ds: Ag icul u al managemen G eenhouses gases Soil CO 2 e lux Con en ional illage No- ill ABSTRACT App op ia e managemen o c op esidue plays a key ole in mi iga ing g eenhouse gas emissions. Howe e , i has been inadequa ely implemen ed in gene al ag icul u al managemen p ac ices. In a ield in es iga ion using s a ic chambe s, we e alua ed he e ec s o c op esidue a h ee di e en a es - 100 % (R 100 ), 50 % (R 50 ), and esidue emo al (R 0 ) - on ca bon dioxide (CO 2 ) e lux. The ield s udy was conduc ed in co n-whea o a ion unde con en ional (CT) and no- illage (NT) sys ems in a semi-a id egion. The main esul s showed ha CO 2 e lux was posi i ely co ela ed wi h highe soil empe a u e (0.43–0.79) and mic obial biomass ca bon (0.66–0.89). The c op esidue ea men s a ec ed hese ai s. A s ong posi i e ela ionship be ween CO 2 e lux and he c op esidue (R 2 =0.96, CT and R 2 =0.9 o NT) was obse ed. In he CT sys em, signi ican inc eases we e de ec ed among esidue a es on cumula i e CO 2 e lux, whe e R 100 and R 50 esul ed in 36 % and 25 % highe cumula i e CO 2 e lux, espec i ely, han R 0 . In con as , he e was no signi ican di e ence in cumula i e CO 2 e lux among he c op esidue e en ion (R 100 and R 50 ) and emo al (R 0 ) ea men s unde he NT sys em. Ou s udy e ealed ha c op esidue e en ion led o inc eased CO 2 e lux unde he CT sys em in semi-a id condi ions du ing he i s yea o applica ion, while unde he NT sys em, CO 2 e lux was no impac ed by c op esidue. Ou esul s indica e ha he e is conside able po en ial o imp o ing soil managemen p ac ices in he con ex o soil deg ada ion, clima e change, inc easing c op p oduc i i y, and ca bon (C) seques a ion. 1. In oduc ion The con inuous inc ease in he concen a ion o g eenhouse gases (GHGs) p oduced by human ac i i ies has become a majo conce n due o hei di ec impac on global wa ming and clima e change (Oe el e al., 2016). The concen a ion o CO 2 in he a mosphe e inc eased om 278 ppm in 1750 o 390.5 ppm in 2011 (Ciais e al., 2013), and hen up o 418 ppm in 2021 (Tanhua e al., 2021). CO 2 emission is he p ima y mechanism o soil C loss and con ibu es o he ele a ed CO 2 concen- a ion in he a mosphe e (Pa kin and Kaspa , 2003). Mos o he CO 2 emi ed om he soil is due o he decomposi ion o plan esidue and oo s, due o mic obial me abolism and espi a ion (Sainju e al., 2008; Campbell e al., 2014). I was es ima ed ha 75–120 Pg C pe yea is emi ed om soil o he a mosphe e (Hibba d e al., 2005). The e o e, main enance and build-up o soil C a e essen ial in imp o ing soil unc ions and o se ing a mo- sphe ic CO 2 concen a ion (Smi , 2004; Delgado-Baque izo e al., 2017), which is a key challenge o humankind (Lal, 2004; Scha lemann e al., 2014; Rod igo-Comino e al., 2020a). C op esidue managemen a ec s CO 2 emissions, p ima ily ia al e ing C and ni ogen (N) cycling * Co esponding au ho s. E-mail add esses: [email p o ec ed] (M. Mi zaei), [email p o ec ed] (A. Caballe o-Cal o). Con en s lis s a ailable a ScienceDi ec Pedobiologia - Jou nal o Soil Ecology jou nal homepage: www.else ie .com/loca e/pedobi h ps://doi.o g/10.1016/j.pedobi.2022.150819 Recei ed 16 Decembe 2021; Recei ed in e ised o m 31 May 2022; Accep ed 10 June 2022 Pedobiologia - Jou nal o Soil Ecology 93–94 (2022) 150819 2 (Guzman e al., 2015; Nawaz e al., 2017). Howe e , mul iple ac o s egula e CO 2 emissions om he soil. Changes in soil empe a u e and mois u e le els (Dong e al., 2017), o ganic ma e (OM) inpu s om decomposing esidues- and hei e ec on aunal and mic obial ac i - i ies, all in luence soil espi a ion (Toosi e al., 2012). Due o he complexi y o ac o s go e ning soil espi a ion ollowing he addi ion o c op esidues and hei in e ac ions, con as ing obse - a ions ha e been epo ed in he li e a u e, i.e., inc eases (Badía e al., 2013; Sugas i and Pinz´ on, 2020) o dec eases in soil CO 2 emissions ollowing he applica ion o c op esidue in soil (Bai e al., 2017). Mos c opping lands in I an a e semi-a id egions (i.e., high pH and CaCO 3 , low OM, and supp essed biological s a us) whe e co n-whea o a ion is a common g ain p oduc ion c opping sys em. Despi e i s alue as a sou ce o OM, much o he pos ha es c op esidue is g azed o collec ed as a eed sou ce. Residue emo al and excessi e illage a e he main cause o soil OM deple ion in g ain c ops in he egion (Mi zaei e al., 2021). E o s ha e been made a he na ional le el o encou age a me s o e u n c op esidues o he soil. The e ec o esidue e en ion on CO 2 emission om he soil, ypical o semi-a id condi ions, has no been adequa ely s udied. P e ious s udies ha e shown ha equen d ying-we ing cycles in a id and semi-a id condi ions could lead o subs an ial C losses in soil om newly added OM (Bo ken and Ma zne , 2009). We hypo hesized ha : i) he addi ion o c op esidue o he soil esul s in highe CO 2 e lux compa ed o esidue emo al, independen o he illage e ec ; ii) he cumula i e CO 2 e lux would inc ease wi h an inc easing amoun o c op esidue o he soil. To es he abo e-men ioned hypo heses, we moni o ed CO 2 e lux in a ield s udy, using c op esidue a h ee a es – 100 % (R 100 ), 50 % (R 50 ), and esidue emo al (R 0 ) in co n-whea o a ion unde con en ional (CT) and no- illage (NT) sys ems. As key egula o s o soil espi a ion, mic obial biomass and soil mois u e and empe a u e we e also moni- o ed du ing he expe imen o link hei possible associa ion wi h he soil CO 2 e lux. 2. Ma e ials and me hods 2.1. Si e cha ac e is ics and expe imen al design The s udy was conduc ed in 2018 a he Ag icul u e Resea ch S a ion o he College o Ag icul u e and Na u al Resou ces, Uni e si y o Teh- an, Ka aj, I an (35◦48′32" N, 50◦58′06" E, 1308 m a.s.l.). This a ea has semi-a id clima e condi ions wi h a mean annual empe a u e o 13.7 ◦C and p ecipi a ion o 245 mm (Fig. 1). Two ields unde con as ing illage managemen , con en ional illage (CT) and no- illage (NT), we e selec ed. Bo h sys ems we e unde a whea (T i icum aes i um L.) - co n (Zea mays L.) o a ion o a leas i een yea s be o e he s udy. Each ield o 11 ×16 m was di ided in o nine 3 ×4 m sub-plo s. The expe imen al design was a andomized comple e block wi h h ee ep- lica es pe ea men . Table 1 summa izes he main physical and chemical soil p ope ies. Ten soil samples we e collec ed andomly using an auge sample (8 cm diame e ) om 0 o 10 cm and 10–20 cm dep hs in each ield. Subsequen ly, soil samples we e uni o mly mixed o one composi e sample pe soil dep h. Soil samples we e ai -d ied, sie ed (2 mm), and s o ed un il analyzes we e ca ied ou . Soil ex u e was de e mined by he hyd ome ic me hod (Gee and Baude , 1986). Soil o ganic ca bon (SOC) using he Walkley and Black me hod (Walkley and Black, 1934), pH, and elec ical conduc i i y (EC) we e measu ed in sa u a ed soil ex ac s (Richa des, 1954). A ailable phospho us was de e mined using he NaHCO 3 me hod (Olsen and Somme s, 1982). The ammonium ace a e me hod was used o de e mining a ailable po as- sium (Knudsen e al., 1982). To al ni ogen (TN) was measu ed using he Kjeldahl me hod desc ibed by B emne and Mul aney (1982). Mic o- nu ien s we e measu ed in DTPA ex ac s (Lindsay and No ell, 1978) using a omic abso p ion spec opho ome y. 2.2. T ea men applica ions The whea esidue was applied ollowing whea ha es (Jul 2018) in bo h NT and CT ields. The h ee le els o esidue we e 3.5 ha −1 Fig. 1. Mon hly p ecipi a ion and mean ai empe a u e du ing he pe iod o he expe imen . Table 1 Soil p ope ies o 0–10 and 10–20 cm soil dep hs in he ields in 2019. Soil p ope ies Con en ional illage (CT) No- illage (NT) 0–10 cm 10–20 cm 0–10 cm 10–20 cm pH *7.8 ±0.1 7.7 ±0.1 7.8 ±0.0 7.6 ±0.1 EC (ds m −1 ) 0.9 ±0.0 0.7 ±0.2 1 ±0.0 0.7 ±0.2 OC (mg/g) 0.9 ±0.1 0.8 ±0.2 1.2 ±0.0 1.01 ±0.1 TN (mg/g) 0.09 ±0.01 0.07 ±0.01 0.1 ±0.0 0.08 ±0.0 A ail K (mg kg −1 ) 167 ±4 134 ±3 279 ±5.2 237.4 ±6.0 A ail P (mg kg −1 ) 9 ±0.2 9.5 ±0.6 15 ±1.5 15.3 ±0.7 Bulk densi y (g cm −3 ) 1.52 1.56 1.32 1.38 To al Po osi y (%) 54 ±2 52 ±1.1 48 ±1.9 45 ±1 Sand (%) 57 ±1 53 ±1 28 ±0.3 27 ±0.7 Sil (%) 25 ±1 28 ±1 42 ±0.2 42 ±0.6 Clay (%) Soil ex u e 18 ±1 Sandy Loam 19 ±2 Sandy Loam 30 ±0.4 Clay Loam 31 ±0.7 Clay Loam EC: elec ical conduc i i y, OC: o ganic ca bon, TN: o al ni ogen, A ail K: a ailable po assium, A ail P: a ailable phospho us. * Values a e Mean ±S anda d De ia ion (n =3). M. Mi zaei e al. Pedobiologia - Jou nal o Soil Ecology 93–94 (2022) 150819 3 (100 %, R 100 ), 1.75 ha −1 (50 %, R 50 ), and no esidue ( esidue was comple ely emo ed, R 0 ). The selec ion o esidue le els was based on c op yield, which was almos simila in bo h CT and NT sys ems. The plan esidue was weighed acco ding o he ea men and was hen homogeneously and manually dis ibu ed o e he su ace o each plo . In he CT ield, all he h ee esidue le els we e illed and inco po a ed in o he soil, while in he NT hey we e jus le on he soil su ace. Fo he esidue emo al ea men (R 0 ), unde bo h CT and NT sys ems, he whole esidue om he p e ious c op was emo ed om he plo , and he soil su ace was le unco e ed. A e his, silage co n was plan ed by using a ow c op plan ed a a dose o 35 kg ha −1 wi h a dis ance o 15 cm wi hin he ow and 75 cm be ween he ows. In he NT ield, seed placemen was made using a plan e wi h a single coul e o elimina e esidue and loosen he soil be o e he s anda d plan e uni . In he CT ield, be o e seeding, he soil was plowed o a dep h o 35 cm wi h a moldboa d plow, disked, and le eled. Bo h NT and CT ecei ed equal basal NPK e ilize s equal o 50 kg ha −1 U ea, 70 kg ha −1 Po assium sul a e, and 150 kg ha −1 Supe phospha e. Addi ional N was op-d essed a eigh lea es (80 kg U ea ha −1 ) and en lea es (270 kg U ea ha −1 ) s ages. Plo s we e i iga ed a e cul i a ion and 7–10 days in e als he ea e using he sp inkle i iga ion me hod. A e ha es ing he co n (Oc 2018), h ee le els o esidue we e applied equally o 1.8 (100 %, R 100 ), 0.9 on ha −1 (50 %, R 50 ), and no esidue (0 %, R 0 ). Win e whea was plan ed in No 2018, a a dose o 208 kg ha −1 seed wi h a ow dis ance o 13 cm by a mechanical d illing machine. Basal e iliza ion included he equi alen s o 50 kg ha −1 u ea, 200 kg ha −1 supe phospha e, and 150 kg ha −1 po assium sul a e. Addi ional N e - ilize was supplied du ing la e ille ing (110 kg U ea ha −1 ), s em elonga ion (110 kg U ea ha −1 ), and spiking (50 kg U ea ha −1 ). 2.3. Plan esidue analyses A sub-sample o whea and co n esidues was d ied and inely g ound o chemical analyses (Table 2). O ganic ca bon (OC) was measu ed by we oxida ion (Walkley and Black, 1934), and he Kjeldahl me hod was used o de e mining o al ni ogen (TN) con en . Fo measu emen o o al phospho us (P) and po assium (K), he samples we e combus ed a 500 ◦C, and P and K we e de e mined using spec opho ome ic and lame pho ome ic me hods, espec i ely. 2.4. Soil CO 2 e lux Gas sampling was s a ed in la e July and ea ly Augus 2018 in he Table 2 Elemen al composi ion o whea and co n esidue. Plan esidue N P K C C/N % – Whea *0.84 ±0.12 0.09 ±0.01 1.75 ±0.07 55.4 ±1.80 66 ±2.56 Co n 0.92 ±0.06 0.25 ±0.02 1.08 ±0.01 53.65 ±1.30 58 ±1.63 * Values a e Mean ±s anda d de ia ion (n =3). Fig. 2. The e ec o esidue le els on soil empe a u e a he gas sampling e en s unde he no- illage (NT) (a) and con en ional illage (CT) (b) sys ems. Ba s ep esen s anda d e o (n =3). An as e isk (*) shows a signi ican di e ence be ween esidue le els wi hin a day a P <0.05. M. Mi zaei e al. Pedobiologia - Jou nal o Soil Ecology 93–94 (2022) 150819 4 co n c opping sys em unde he NT and CT sys ems espec i ely and ended in ea ly June 2019 in he whea c opping sys em unde bo h sys ems. Gas sampling was pe o med a 7–10 d in e als gene ally, and e e y wo weeks in win e (Decembe –Feb ua y), based on he GRACEne Chambe -based T ace Gas Flux Measu emen p o ocol (Pa - kin and Ven e ea, 2010). The s a ic closed chambe me hod was used o measu e he amoun o CO 2 e lux om he soil. The me hod has been widely used o he measu emen o soil gas e lux, including ca bon dioxide, me hane, and ni ous oxide (Oe el e al., 2012). Poly inyl chlo ide (PVC) chambe s (15 cm diame e , 12.5 cm heigh ) wi h po s o gas sampling we e g adually hamme ed in o he soil su ace o dep hs o 5 cm du ing he whole moni o ing pe iod. Chambe s we e only emo ed du ing cul i a ion e en s. To enable chambe ope a ion, he c ops we e mowed when hei heigh exceeded he chambe ’s heigh . Gas samples we e collec ed a leas 24 h a e chambe ins al- la ion o a oid dis u bance e ec s. Gas sampling was pe o med om 9 o 10 am a 0, 30, and 60 min ime poin s by inse ing a needle a ached o a 20 mL sy inge in he sampling po and ans e ing in 12 mL p e- acuumed ials sealed wi h bu yl ubbe sep a (Labco Exe aine , UK). The concen a ion o CO 2 in he ials was measu ed using gas ch oma og aphy (Tei Gos a Fa az, TG 2552, I an), equipped wi h a he mal conduc i i y de ec o (TCD). The CO 2 e lux was calcula ed as he changes in linea concen a ion g adien o e ime and om he a io be ween chambe olume and soil su ace a ea (Liebig e al., 2010). The CO 2 e lux was con e ed o i s ca bon equi alen (CO 2 -C) by mul iplying i by he a io o he molecula weigh o ca bon o ha o ca bon dioxide (12/44). Cumula i e amoun s o CO 2 e lux we e calcula ed using linea ly in e pola ing da a poin s and in eg a ing he unde lying a ea (Sainju e al., 2012; Wegne e al., 2018). 2.5. Ancilla y measu emen s To e alua e he ela ionship be ween soil condi ions and CO 2 e lux, soil empe a u e, and mois u e con en s, as well as mic obial biomass C, we e de e mined a each gas sampling e en . Soil empe a u e was measu ed wi h a he mome e a 10 cm dep h nex o he colla s. Th ee soil samples (0–10 cm) we e aken wi h a co e sample (100 cm 3 ol- ume) om each plo ha was hen mixed in o one composi e sample. The soil mois u e con en o he samples was de e mined using o en- d ying a 105 ◦C mul iplied by soil bulk densi y. Soil bulk densi y was measu ed using s ainless s eel cylinde s (100 cm 3 olume). Mic obial biomass ca bon (MBC) was de e mined by he chlo o o m umiga ion ex ac ion me hod (Jenkinson e al., 2004). 2.6. S a is ical analyses The da a we e analyzed using he Analysis o Repea ed Measu es p ocedu e in gene al linea models (GLM) o SAS so wa e e sion 9.4 (SAS Ins i u e, Ca y, NC, USA). Residue a e, illage ype, and sampling ime we e he ixed e ec s. Soil pa ame e s (mois u e, empe a u e, MBC) and CO 2 e lux we e he epea ed measu e a iables. Means o each esidue a e, illage ype, and sampling ime we e compa ed by he Duncan me hod a he 0.05 p obabili y le el. Pea son linea co ela ion Fig. 3. The e ec o esidue le els on soil mois u e a he gas sampling e en s unde he no- illage (NT) (a) and con en ional illage (CT) (b) sys ems. Ba s ep esen s anda d e o (n =3). An as e isk (*) shows a signi ican di e ence be ween esidue le els wi hin a day a P <0.05. M. Mi zaei e al. Pedobiologia - Jou nal o Soil Ecology 93–94 (2022) 150819 5 analysis was used o de e mine he ela ionships be ween soil pa ame- e s (mois u e, empe a u e, MBC) and CO 2 e lux. 3. Resul s and discussion 3.1. Soil empe a u e and soil mois u e In he NT sys em, du ing he co n season (Jul–Oc ), and also in he allow pe iod be ween co n and whea seasons (14/10/2018 and 24/10/ 2018), soil empe a u e was highe in plo s ecei ing esidue a lowe a es, whe e a signi ican inc ease (P <0.05) in soil empe a u e was obse ed in he R 0 compa ed o R 50 and R 100 ea men s (Fig. 2a). On he o he hand, in mos cases, no signi ican di e ences we e obse ed be- ween R 100 and R 50 . F om he beginning o he whea -g owing season in au umn (26/11/2018) un il he end o win e (22/3/2019), he opposi e end was no iced, whe e high esidue a e led o inc eased soil em- pe a u e, and R 100 and R 50 esul ed in a signi ican inc ease (P <0.05) in soil empe a u e compa ed o R 0 . He e, in mos cases, he di e ences be ween R 100 and R 50 we e no signi ican . In addi ion, om he beginning o sp ing un il he end o he expe imen al pe iod, he soil empe a u e in R 0 ea men inc eased compa ed o R 100 and R 50 ea men s. The esul s o his s udy a e consis en wi h p e ious ind- ings (Guzman e al., 2015). The inc easing soil empe a u e in R 0 in summe and R 100 and R 50 in au umn and win e unde he NT sys em can be a ibu ed o he insula ing e ec o plan esidue. The p esence o plan esidue on he soil su ace in he NT sys em p o ec s he soil agains se e e he mal luc ua ions and modula es su ace adia ion ene gy and he mal changes be ween soil and a mosphe e (Ho on e al., 1996). In he summe , plan esidue on he soil su ace p e en s he abso p ion o mo e adia ion, hus p e en ing he soil su ace om wa ming. In au umn and win e , plan esidue on he soil su ace p e- en s hea exchange and, hus causes he soil o wa m up compa ed o ba e soil. Du ing c op o a ion unde he CT sys em, soil empe a u e inc eased wi h inc easing esidue a e a all sampling imes, and, in mos cases, hese inc eases in R 100 and R 50 ea men s we e signi ican (P <0.05) compa ed o R 0 . S ill, in some cases, no signi ican di e ence was obse ed be ween R 100 and R 50 ea men s (Fig. 2b). Resul s ob ained in he CT sys em a e cong uen wi h Zhang e al. (2018) in hei s udy in China. In he CT sys em, c op esidue is inco po a ed in o he soil ins ead o emaining on he soil su ace, lea ing a small amoun o plan esidue on he soil su ace, which educes he e ec o c op esidues and causes he soil o abso b mo e hea , and leads o inc eases in soil empe a u e (Dendoo en e al., 2012). In almos all sampling imes, R 100 and R 50 ea men s caused a sig- ni ican inc ease (P <0.05) in mois u e compa ed o R 0 unde bo h CT and NT sys ems (Fig. 3a,b). Howe e , in se e al cases, no signi ican di e ences we e obse ed be ween R 100 and R 50 . Inc eased soil mois u e in R 100 and R 50 ea men s compa ed o R 0 unde bo h CT and NT sys- ems could be explained by he ac ha c op esidue educes mois u e e apo a ion and inc eases wa e -holding capaci y and soil wa e con- en . P e ious s udies ha e also sugges ed ha c op esidue inc eases Fig. 4. The e ec o esidue le els on soil mic obial biomass ca bon (MBC) in no- illage (NT) (a) and con en ional illage (CT) (b) sys ems a he gas sampling e en s. Ba s ep esen s anda d e o (n =3). The bold black a ows indica e e iliza ion e en s. An as e isk (*) shows a signi ican di e ence be ween esidue le els wi hin a day a P <0.05. M. Mi zaei e al. Pedobiologia - Jou nal o Soil Ecology 93–94 (2022) 150819 6 soil wa e con en (Sainju e al., 2012; Chalise e al., 2019) as well as o he ypes o co e c ops o mulches (Rod igo-Comino e al., 2020b). 3.2. Soil mic obial biomass ca bon The e we e signi ican di e ences o mic obial biomass ca bon (MBC) ac oss all ea men s o esidue a es du ing he o a ion cycle unde bo h illage sys ems (Fig. 4a,b). MBC was he highes in summe du ing he co n season; and declined du ing he cold season and again inc eased wi h ising soil empe a u e. In bo h CT and NT sys ems, MBC was posi i ely co ela ed wi h he le el o c op esidue, i.e., he annual means o 335, 236, and 125 (mg kg −1 ) in R 100 , R 50, and R 0 unde CT, and 590, 500, and 300 (mg kg −1 ) o R 100 , R 50 , and R 0 unde NT (Fig. 5c). The addi ion o N esul ed in mic obial g ow h, as measu ed by MBC, in bo h CT and NT, consis en wi h he li e a u e (S ewa e al., 2018; Mgelwa e al., 2019). The soil mic obial biomass pool is one o he biological p ope ies ha s ongly egula es he dynamics o nu ien s and C in soil (Toosi e al., 2012). I has also been shown ha mic obial biomass esponds mo e apidly o plan esidue managemen compa ed o he o al soil OM pool (Yang e al., 2012). Ou indings a e in line wi h p e ious s udies, indica ing ha inc easing he le el o c op esidues posi i ely a ec s he MBC pool size (Chowdhu y e al., 2015; Li e al., 2017). These could be due o he ele a ed MBC in soils co e ed by c op esidue, namely enhanced soil mois u e con en , and also a supply o soluble C (and o he nu ien s) de i ed om he decomposing esidue (Yang e al., 2012). The lowe a e o MBC du ing he cold season could be a ibu ed o he lowe soil empe a u e du ing his pe iod. A sig- ni ican and posi i e co ela ion be ween soil empe a u e and MBC also con i ms his (Table S1). Low soil empe a u e may limi soil mic obial ac i i y and hei popula ion. Tempe a u e and mois u e a e he mos impo an ac o s in luencing soil mic obial biomass (Babu and Din- da oglu, 2020). 3.3. CO 2 e lux CO 2 e lux o all esidue a es ollowed a simila pa e n o all esidue le els in bo h NT and CT (Fig. 6a,b). Highe soil CO 2 e lux du ing summe and sp ing is a ibu ed o highe soil empe a u e (Fig. 2a,b), and as a esul , enhanced biological (mic obial, aunal, and oo ) ac i i y. Seasonal luc ua ions in soil empe a u e and hei in- luence on CO 2 (and o he GHGs) e lux om he soil a e well docu- men ed (Schau le e al., 2010). The CO 2 -C e lux a e dec eased wi h inc easing esidue e en ion a all sampling da es du ing he co n season in summe (26/7/2018–4/10/ 2018) unde he NT sys em, whe e soil espi a ion was signi ican ly highe (P <0.05) unde R 0 han R 100 and R 50 ea men s (Fig. 6a). A highe in ensi y o soil espi a ion in unco e ed soil has also been e- po ed p e iously (Guzman e al., 2015). A key eason o he signi ican inc ease in soil CO 2 e lux in R 0 compa ed o R 100 and R 50 ea men s du ing he co n season unde he NT sys em appea s o be g ea e luc ua ions in soil empe a u e (Fig. 2a,). A posi i e and signi ican co ela ion be ween soil empe a u e and CO 2 e lux also con i ms his (Table 3). Soil empe a u e is he main ac o in luencing he emission o CO 2 om he soil (Dendoo en e al., 2012). Yin e al. (2016) and Wegne e al. (2018) also epo ed a posi i e co ela ion be ween CO 2 emissions and soil empe a u e. In addi ion, ano he eason o he inc easing CO 2 e lux in R 0 compa ed o R 100 and R 50 can be possibly a ibu ed o he high C/N a io (66) o whea esidues (Table 2) applied be o e he co n Fig. 5. The e ec o c op esidue a es on annual mean soil empe a u e (a) mois u e (b), mic obial biomass ca bon (MBC) (c), and CO 2 -C e lux (d) du ing co n- whea o a ion unde con en ional illage (CT) and no- illage (NT) sys ems. Means wi h he same le e a e no signi ican ly di e en . Ba s ep esen s anda d e o (n =3). M. Mi zaei e al. Pedobiologia - Jou nal o Soil Ecology 93–94 (2022) 150819 7 g owing season, which educes he decomposi ion a e and elease o CO 2 . I has also been epo ed ha he C/N a io o an o ganic esidue applied o he soil mos ly de e mines he a e o i s mine aliza ion (Nguyen and Ma schne , 2016). When esidue was added, he e was no di e ence in soil espi a ion be ween R 100 and R 50 . In con as , om he s a o he whea season un il he end o he expe imen , CO 2 e lux inc eased wi h an inc easing esidue e en ion a e a all sampling e en s compa ed o R 0 . Howe e , he di e ences among he esidue ea men s we e no signi ican om ea ly o la e win e in 2019, which could be ela ed o lowe soil em- pe a u e and limi ed mic obial ac i i y and oo espi a ion du ing his pe iod. In he sp ing o 2019, signi ican inc eases (P <0.05) we e eco ded o R 100 and R 50 compa ed o R 0 on se e al sampling da es, especially a e u ea e iliza ion e en s. A signi ican inc ease in CO 2 e lux a e e iliza ion ac i i ies could be a ibu ed o imp o ed plan g ow h, pho osyn hesis, and espi a ion (Holou, 2010), s imula ing and inc easing he mine aliza ion o c op esidue (Dendoo en e al., 2012; Sainju e al., 2012). In he CT sys em, he CO 2 -C e lux a e inc eased wi h inc easing esidue a e, and hese inc eases we e signi ican (P <0.05) a almos all sampling imes in R 100 and R 50 ea men s compa ed o R 0 , bu he signi ican di e ences (P <0.05) be ween R 100 and R 50 ea men s we e only no iced in a ew sampling da es, mainly a e u ea e iliza ion e en s in sp ing 2019, and o he mos o he da es he di e ences we e no signi ican (Fig. 6b). The signi ican inc ease in CO 2 e lux in he R 100 and R 50 compa ed o he R 0 , which was obse ed in bo h CT and NT du ing he sp ing, can be explained by a subs an ial inpu om decomposing esidue ha se es as a subs a e o soil mic obes (Toosi e al., 2017). Se e al s udies ha e epo ed ha he inco po a ion o plan esidue inc eases soil CO 2 emissions (Badía e al., 2013; Wang e al., 2019). Meanwhile, inc eased plan esidue mine aliza ion, soil o ganic ca bon, mic obial biomass ca bon, and dissol ed o ganic ca bon accoun ed o inc easing CO 2 emissions (Zhao e al., 2014; Ding e al., 2017; Yang e al., 2017). Howe e , o he s udies epo ed educed soil CO 2 emis- sions due o he e en ion o plan esidue in he soil (Bai e al., 2017). 3.4. Cumula i e CO 2 e lux The annual cumula i e e lux o CO 2 -C did no di e signi ican ly be ween esidue a e ea men s unde he NT sys em. S ill, he cumu- la i e e lux o CO 2 -C was highe (p <0.05) in he CT sys em whe e R 100 (4.65 Mg CO 2 -C ha −1 y −1 ) and R 50 (4.26 Mg CO 2 -C ha −1 y −1 ) ep e- sen ed 36.5 % and 25 % g ea e cumula i e CO 2 -C e lux, espec i ely, han R 0 (3.4 Mg CO 2 -C ha −1 y −1 ) (Fig. 7). Simila ly, D u y e al. (2021) epo ed ha co n esidue minimally a ec ed CO 2 e lux in soils unde he NT. S ill, in he CT sys em, ull e en ion o co n esidue inc eased soil espi a ion up o 47 %. Con as ing esul s on he e ec o esidue in soil espi a ion (e.g., Wegne e al., 2018) a e due o he complex in e ac ion o di e en ac o s such as esidue amoun and quali y, as well as soil and en i onmen al condi ions. The s ong posi i e ela ionship be ween cumula i e CO 2 e lux and he c op esidue (R 2 =0.96 o CT and R 2 =0.9 o NT) sugges s he Fig. 6. Residue a e e ec on daily soil CO 2 -C e lux a he ime o g eenhouse gas measu emen in co n-whea o a ion unde no- illage (NT) (a) and con en ional illage (CT) (b) sys ems. Ba s ep esen s anda d e o . The bold black a ows indica e e iliza ion e en s. An as e isk (*) shows a signi ican di e ence be ween esidue le els wi hin a day a P <0.05. M. Mi zaei e al. Pedobiologia - Jou nal o Soil Ecology 93–94 (2022) 150819 8 con ibu ion o he plan esidue o soil espi a ion (Fig. 8). In he CT sys em, when calcula ed, an addi ional 1.25 Mg C ha −1 was espi ed om he R 100 han om he no esidue soil, equi alen o 43 % o he o al (2.9 Mg C ha −1 ) o he added esidue (Table 4). Fo he R 50 , his was equi alen o 59 % o he added esidue (1.44 Mg C ha −1 ). Unde he NT sys em, hese alues we e 5.5 %, and abou 3 % o o al C added om c op esidue in R 100 and R 50 , espec i ely, compa ed o ha espi ed om he no esidue ea men . This indica es ha unde bo h CT and NT sys ems, he e was C accumula ion in he soil ollowing he addi ion o c op esidue. Howe e , i has been well documen ed ha in he long e m, he as majo i y o he added C om esidue will espi e o he a mosphe e and only a small ac ion o esidual C will be inco po a ed in o soil OM (Kuzyako , 2006; Campos e al., 2011). 3.5. The e ec o illage and in e ac ion e ec s o esidue a e and illage sys em on soil p ope ies ( empe a u e, mois u e, MBC), and CO 2 e lux The e ec o illage and he in e ac ion e ec s o esidue a e and illage sys em on soil empe a u e was no signi ican (Table 5 and Fig. 9a). Mo e signi ican inc eases (P <0.05) in mean and cumula i e CO 2 e lux we e obse ed in he CT sys em han in he NT sys em (Table 5). Soil mois u e and mic obial biomass ca bon we e signi ican ly highe in he NT sys em compa ed o he CT sys em. In addi ion, signi ican (P <0.05) in e ac ion e ec s o esidue a e and illage sys em we e obse ed o soil mois u e, soil mic obial biomass ca bon, and mean and cumula i e CO 2 e lux (Fig. 9b–e). NT 100 esul ed in he highes alues o soil mois u e (26 %) and mic obial biomass ca bon (591 mg kg −1 ) among he ea men s, while he lowes alue o soil mois u e (17.5 %)) and mic obial biomass ca bon (124.5 mg kg −1 ) we e ob ained om CT 0 (Fig. 9b,c). The highes alues o mean CO 2 e lux (64.5 mg m −2 h −1 ) and cumula i e CO 2 e lux (4.65 Mg ha −1 y −1 ) we e obse ed in CT 100 (Fig. 9d,e), whe eas he Table 3 Co ela ions o CO 2 wi h selec ed soil p ope ies o di e en a es o plan esidues unde con en ional illage (CT) and no- illage (NT) sys ems. Tillage sys em Residue a e Soil pa ame e s CO 2 emission Pea son co ela ion (R) P- alue CT R100 Tempe a u e 0.61** 0.001 Mois u e 0.13 0.49 Mic obial biomass ca bon 0.68** .000 R50 Tempe a u e 0.49** 0.001 Mois u e 0.11 0.46 Mic obial biomass ca bon 0.69** .000 R0 Tempe a u e 0.60** 0.001 Mois u e 0.00 0.99 Mic obial biomass ca bon 0.78** .000 NT R100 Tempe a u e 0.46* 0.01 Mois u e 0.17 0.36 Mic obial biomass ca bon 0.66** .000 R50 Tempe a u e 0.43** 0.004 Mois u e 0.12 0.44 Mic obial biomass ca bon 0.70** .000 R0 Tempe a u e 0.79** .000 Mois u e 0.06 0.73 Mic obial biomass ca bon 0.89** .000 **. Co ela ion is signi ican a he 0.01 le el. *. Co ela ion is signi ican a he 0.05 le el. Fig. 7. Residue a e e ec on annual cumula i e CO 2 -C (Mg ha -1 y -1 ) e lux unde no- illage (NT) and con en ional illage (CT) sys ems. Means wi h di e en le e s in each illage sys em indica e signi ican di e ences (P <0.05). Ba s ep esen s anda d e o (n =3). Fig. 8. Linea eg ession be ween esidue a es and cumula i e CO 2 -C e lux pe soil managemen sys em. CT: con en ional illage; NT: no- illage. The poin s on each CT and NT line ep esen he annual cumula i e CO 2 -C e lux o di e en a es o esidue (co n and whea ) du ing he whole co n-whea o a- ion cycle. Table 4 C op esidue ca bon applica ion a es (d y weigh basis) in co n-whea o a ion unde each con en ional illage (CT) and no- illage (NT) sys em. C op esidue a e (%) Whea esidue (Mg C ha −1 ) Co n esidue (Mg C ha −1 ) To al (Mg C ha −1 ) 100 *1.93 0.96 2.90 50 0.96 0.48 1.44 0 0 0 0 * C op esidue ca bon applica ion a es (d y weigh basis) we e based on c op yield and almos simila unde bo h CT and NT sys ems. Table 5 The e ec o illage on mean soil CO 2 emissions, soil empe a u e, soil mois u e, mic obial biomass ca bon, and cumula i e CO 2 emissions. Tillage sys em Mean CO 2 emissions (mg m −2 h −1 ) Tempe a u e (◦C) Mois u e (%) Mic obial biomass ca bon (mg kg −1 ) Cumula i e CO 2 emissions (Mg ha −1 y −1 ) CT a 57.15 ±12.36a 15.41 ±3.30a 20.62 ±3.52b 232.05 ±85.80b 4.10 ±0.55a NT 34.86 ±10.71b 15.40 ±3.01a 23.89 ±1.82a 465.96 ±117.93a 2.47 ±0.10b Means wi h he same le e in each column a e no signi ican ly di e en . a Mean ±s anda d de ia ion, n =3. M. Mi zaei e al. Pedobiologia - Jou nal o Soil Ecology 93–94 (2022) 150819 9 lowes alues o mean CO 2 emissions (34 mg m −2 h −1 ) and cumula i e CO2 e lux (2.4 Mg ha −1 y −1 ) we e ound in NT 0 (Fig. 9d,e). Fu he - mo e, no signi ican di e ences we e ound o cumula i e CO 2 e lux among NT 100 , NT 50 , and NT 0 (Fig. 9e). In he NT sys em, du ing he co n c opping season CO 2 e lux was highe in he R 0 compa ed o R 100 and R 50 , while du ing he whea season, a e e se end was obse ed in which he a e o CO 2 e lux inc eased in R 100 and R 50 compa ed o R 0 (Fig. 6a). By conside ing he whole co n-whea o a ion, i is possible ha hese wo di e en ends neu alized he e ec o each o he and led o no signi ican di e ences among he esidue ea men s. Also, unde conse a ion illage sys ems including he NT sys em, c op es- idue is no inco po a ed in o he soil and hey a e no su icien ly ag- men ed and decomposed, which consequen ly educes he eal po en ial o c op esidue managemen on CO 2 e lux. In ag eemen wi h ou indings, D u y e al. (2021) epo ed no signi ican e ec o di e en c op esidue emo al a es on CO 2 emissions unde he NT sys em. Also, Teixei a e al. (2013) ound no la ge di e ences in CO 2 emissions om plo s wi h o wi hou c op esidues unde o a y illage. Fig. 9. The in e ac ion e ec o esidue a e and illage sys em on annual mean soil empe a u e (a), mois u e (b), mic obial biomass ca bon (MBC) (c), CO 2 -C e lux (d), and cumula i e CO 2 -C e lux (e). Means wi h he same le e a e no signi ican ly di e en . Ba s ep esen s anda d e o (n =3). M. Mi zaei e al.