林洪羽, 周明華, 張博文, 李子陽(yáng), 朱 波
生物炭及秸稈長(zhǎng)期施用對(duì)紫色土坡耕地土壤團(tuán)聚體有機(jī)碳的影響*
林洪羽1,2, 周明華1 **, 張博文1,2, 李子陽(yáng)1,2, 朱 波1
(1. 中國(guó)科學(xué)院水利部成都山地災(zāi)害與環(huán)境研究所 成都 610041; 2. 中國(guó)科學(xué)院大學(xué) 北京 100049)
依托紫色土坡耕地長(zhǎng)期施肥試驗(yàn)觀測(cè)平臺(tái), 研究生物炭、秸稈對(duì)紫色土坡耕地團(tuán)聚體有機(jī)碳分布的影響。長(zhǎng)期施肥試驗(yàn)處理包括不施肥(CK)、無(wú)機(jī)氮磷鉀肥(NPK)、秸稈還田(RSD)、生物炭與無(wú)機(jī)氮磷鉀配施(BCNPK)、秸稈與無(wú)機(jī)氮磷鉀配施(RSDNPK)。利用濕篩法, 進(jìn)行土壤團(tuán)聚體粒徑分組, 隨后測(cè)定各粒徑團(tuán)聚體含量及其有機(jī)碳含量, 并計(jì)算團(tuán)聚體平均質(zhì)量直徑(MWD)和幾何平均直徑(GMD)。結(jié)果表明, RSD、RSDNPK和BCNPK處理的表層SOC含量比CK處理增加43.1%~90.5%, SOC儲(chǔ)量提高65.1%~74.3%, 其中RSDNPK處理、BCNPK處理較NPK處理SOC顯著增加25.2%~33.1%(<0.05), SOC儲(chǔ)量顯著提高23.2%~30.0% (<0.05)。團(tuán)聚體MWD和GMD均為RSD處理>RSDNPK處理>BCNPK處理>NPK處理>CK處理; RSD處理0.25~2 mm的團(tuán)聚體含量高達(dá)45.5%, 較CK處理提高57.7%; 秸稈和生物炭配施處理(RSDNPK處理和BCNPK處理)0.25~2 mm的團(tuán)聚體含量為41.3%~45.7%, 而<0.053 mm粒徑團(tuán)聚體含量卻降低54.1%~55.4%。NPK處理、RSD處理與CK處理的增長(zhǎng)趨勢(shì)相似, 呈隨團(tuán)聚體粒徑減小, 團(tuán)聚體有機(jī)碳含量先增大后減小, 繼而再增大的趨勢(shì); 而RSDNPK、BCNPK處理則呈隨粒徑減小團(tuán)聚體有機(jī)碳含量增加的趨勢(shì)。生物炭和秸稈的施用能顯著提升土壤有機(jī)碳含量, 增強(qiáng)土壤結(jié)構(gòu)穩(wěn)定性, 但生物碳的施用對(duì)提升土壤有機(jī)碳含量效果優(yōu)于秸稈的施用, 秸稈的施用對(duì)穩(wěn)定土壤結(jié)構(gòu)效果更優(yōu), 因此生物炭和秸稈的施用可作為紫色土耕地土壤肥力維持和提升的有效管理措施。
土壤團(tuán)聚體; 生物炭; 秸稈; 土壤有機(jī)碳; 紫色土
農(nóng)田土壤有機(jī)碳是陸地生態(tài)系統(tǒng)最為重要的碳庫(kù)之一, 對(duì)維持土壤肥力、保障農(nóng)田生產(chǎn)力有重要作用[1]。紫色土坡耕地是長(zhǎng)江上游山地丘陵區(qū)最主要的耕地資源, 占其耕地總面積的78%, 但由于山地丘陵地區(qū)人多地少, 耕作活動(dòng)強(qiáng)烈, 導(dǎo)致紫色土坡耕地土壤質(zhì)量嚴(yán)重退化, 土壤有機(jī)碳損失量大, 土壤有機(jī)碳庫(kù)減小。因此, 增加紫色土坡耕地土壤有機(jī)碳庫(kù)、增強(qiáng)土壤有機(jī)碳穩(wěn)定性對(duì)防治土壤退化、提升紫色土耕地土壤肥力和保障區(qū)域糧食安全具有重要意義。
不同粒級(jí)土壤團(tuán)聚體不僅能調(diào)控土壤養(yǎng)分供應(yīng)[2]、改善土壤結(jié)構(gòu)與組成[3], 還能影響土壤水力學(xué)性質(zhì)和生物學(xué)性質(zhì)[4]。另外, 土壤團(tuán)聚體一方面能包裹土壤有機(jī)碳, 從而對(duì)土壤有機(jī)碳起到物理保護(hù), 另一方面土壤有機(jī)碳又可促進(jìn)團(tuán)聚體自身的形成[5-7]。因此, 土壤團(tuán)聚體的結(jié)構(gòu)特征已被認(rèn)為是土壤有機(jī)碳貯存潛力的主控因子之一[8], 其穩(wěn)定性已成為表征土壤有機(jī)碳穩(wěn)定性的重要指標(biāo)。當(dāng)前, 土壤團(tuán)聚體平均質(zhì)量直徑(MWD)和幾何平均直徑(GMD)是評(píng)價(jià)土壤團(tuán)聚體穩(wěn)定性的兩個(gè)重要指標(biāo), MWD和GMD值越大則表示團(tuán)聚體越穩(wěn)定[9]。
土壤碳庫(kù)的改變需要較長(zhǎng)時(shí)間, 長(zhǎng)期施肥對(duì)土壤團(tuán)聚體的形成及穩(wěn)定有一定影響。生物炭作為一種能改善土壤物理結(jié)構(gòu)的新型肥料, 不僅能促進(jìn)土壤團(tuán)聚體的形成, 還能增加土壤有機(jī)碳含量[10], 而秸稈中含有農(nóng)作物生長(zhǎng)需要的氮、磷、鉀、硫等多種營(yíng)養(yǎng)元素, 兩者皆可以作為農(nóng)業(yè)生產(chǎn)中重要的肥料資源, 但兩者的長(zhǎng)期施用對(duì)土壤團(tuán)聚體和團(tuán)聚體有機(jī)碳的影響尚不明確。所以, 研究生物炭及秸稈的長(zhǎng)期施用對(duì)土壤團(tuán)聚體及其有機(jī)碳含量和分布的影響已成為熱點(diǎn)。孫天聰?shù)萚11]通過(guò)25年的長(zhǎng)期定位試驗(yàn)發(fā)現(xiàn), 秸稈配施量的不同對(duì)提高褐土不同粒級(jí)團(tuán)聚體有機(jī)碳含量效果不一。向艷文等[12]對(duì)紅壤水稻土研究表明, 化肥和稻草長(zhǎng)期配合施用能顯著助提高團(tuán)聚體有機(jī)碳含量, 提升土壤肥力。侯曉娜等[9]采集砂姜黑土進(jìn)行室內(nèi)培養(yǎng)試驗(yàn), 發(fā)現(xiàn)秸稈單施對(duì)提高團(tuán)聚體穩(wěn)定性優(yōu)于單施生物炭, 而生物炭施用反而降低了大團(tuán)聚體有機(jī)碳貢獻(xiàn)率。紫色土坡耕地土壤有機(jī)質(zhì)含量較少, 土質(zhì)疏松, 易發(fā)生水土流失[13], 選取合理施肥措施對(duì)穩(wěn)定土壤結(jié)構(gòu), 提升土壤有機(jī)質(zhì), 維持紫色土地區(qū)農(nóng)業(yè)可持續(xù)發(fā)展十分重要。雖然已有研究表明生物炭及秸稈可增加農(nóng)田土壤有機(jī)碳含量和土壤結(jié)構(gòu)穩(wěn)定性, 然而關(guān)于生物炭及秸稈對(duì)紫色土團(tuán)聚體組成及團(tuán)聚體有機(jī)碳分布的影響尚不十分清楚。
本研究通過(guò)對(duì)紫色土團(tuán)聚體組成、穩(wěn)定性以及各粒級(jí)團(tuán)聚體有機(jī)碳分布的變化進(jìn)行研究, 明確生物炭及秸稈對(duì)紫色土團(tuán)聚體組成及有機(jī)碳分布的影響, 旨在為紫色土農(nóng)業(yè)區(qū)建立合理的施肥制度提供科學(xué)依據(jù)。
試驗(yàn)依托中國(guó)科學(xué)院鹽亭紫色土農(nóng)業(yè)生態(tài)試驗(yàn)站長(zhǎng)期施肥試驗(yàn)觀測(cè)平臺(tái)(105°27′E, 31°16′N)。該站位于四川盆地中北部, 地形以中深丘為主, 屬于典型亞熱帶濕潤(rùn)季風(fēng)氣候, 年均氣溫17.3 ℃, 降水集中在夏季, 平均降雨量為826 mm, 年無(wú)霜期290 d。土壤為蓬萊鎮(zhèn)組石灰性紫色土, 土壤母質(zhì)為泥巖, 土層厚度為20~60 cm, pH為8.1, 田間持水率0.28~0.37 cm3?cm-3, 凋萎含水率為0.07~0.10 cm3?cm-3。
試驗(yàn)小區(qū)建于2002年6月, 海拔420 m, 坡向?yàn)槲鞅?東南走向, 坡度6.5°, 坡長(zhǎng)8 m, 寬度4 m, 面積為32 m2, 土層厚度約為60 cm, 種植制度為冬小麥()-夏玉米()。設(shè)置不施肥(對(duì)照, CK)、氮磷鉀無(wú)機(jī)肥配施(NPK)、秸稈還田(RSD)、秸稈還田與氮磷鉀配施(RSDNPK)、生物炭與氮磷鉀配施(BCNPK)5種處理, 每個(gè)處理設(shè)置3個(gè)重復(fù), 共15個(gè)小區(qū)。BCNPK處理小麥季、玉米季分別施加生物炭0.29 kg?m-2(生物炭由河南商丘三利公司生產(chǎn), pH為10.22, 含碳量83.4%, 全氮量1.5%)[14]。NPK處理冬小麥季施加氮肥130 kg(N)?hm-2(NH4HCO3)、磷肥[Ca(H2PO4)2]90 kg?hm-2(以P2O5計(jì))、鉀肥(KCl)36 kg?hm-2(以K2O計(jì));夏玉米季施加氮肥150 kg?hm-2, 其余施肥量與冬小麥季相同。小麥和玉米季肥料均以基肥一次性施入, 后期不追肥, 無(wú)灌溉, 大田管理與當(dāng)?shù)剞r(nóng)民習(xí)慣一致。每年測(cè)定當(dāng)季秸稈中全氮含量(冬小麥季施用玉米秸稈, 夏玉米季施用小麥秸稈), 隨后將秸稈用鍘刀切成約15 cm短段還田后翻耕施入耕作層表土。RSD處理秸稈夏季施用量為10 t?hm-2, 冬季施用量為7 t?hm-2。RSDNPK處理需氮量無(wú)機(jī)氮肥占60%、秸稈占40%。BCNPK處理和RSDNPK處理磷肥和鉀肥含量同NPK處理。
樣品采集于2017年8月, 每個(gè)小區(qū)按S型重復(fù)采集耕層(0~20 cm)土樣7次并混合為1個(gè)樣品, 裝入自封袋帶回實(shí)驗(yàn)室風(fēng)干。在風(fēng)干過(guò)程中, 沿裂隙掰為1 cm3左右的小土塊, 待土樣風(fēng)干、混勻后, 用4分法取樣200 g進(jìn)行團(tuán)聚體分級(jí), 另取一部分研磨過(guò)100目尼龍篩, 備用。用環(huán)刀法進(jìn)行土壤容重測(cè)定[15]。
濕篩法是進(jìn)行土壤團(tuán)聚體分級(jí)的常用方法, 該方法將土壤團(tuán)聚體分為大團(tuán)聚體(>2 mm, macroaggregates)和微團(tuán)聚體(<0.25 mm, microaggregates)[16], 0.25~2 mm土壤顆粒為中團(tuán)聚體(small macroaggregates)[17]。本研究采用土壤團(tuán)聚體濕篩法[18]進(jìn)行團(tuán)聚體粒徑分級(jí), 即: 稱取過(guò)8 mm篩的風(fēng)干土樣200 g, 用純水將土樣浸沒(méi)在5 mm篩上5 min, 再通過(guò)一套篩子(2 mm、0.25 mm、0.053 mm), 在純水環(huán)境中進(jìn)行濕篩(振幅3 cm, 頻率50次?2min-1), 得到>2 mm、0.25~2 mm、0.053~0.25 mm的水穩(wěn)定團(tuán)聚體, <0.053 mm的水穩(wěn)定團(tuán)聚體含量用差減法獲得, 將各級(jí)篩上團(tuán)聚體用純水沖洗入燒杯中, 在60 ℃下干燥24 h后稱量, 并計(jì)算各粒級(jí)水穩(wěn)性團(tuán)聚體的含量, 計(jì)算方法如下:
團(tuán)聚體含量(%)=各級(jí)團(tuán)聚體烘干重(g)/測(cè)定團(tuán)聚體的風(fēng)干土重(g)′100% (1)
將烘干后的各級(jí)團(tuán)聚體研磨過(guò)100目篩后用濃度為0.1 mol?L-1稀鹽酸去除土中碳酸鹽, 隨后烘干, 研磨過(guò)100目篩, 最后用全自動(dòng)元素分析儀(vario TOC cube, Elementar, 德國(guó))測(cè)定各粒級(jí)團(tuán)聚體有機(jī)碳(SOC)和全氮(TN)含量。
采用平均重量直徑(MWD)和幾何平均直徑(GMD)評(píng)價(jià)團(tuán)聚體穩(wěn)定性, 對(duì)于>0.25 mm的團(tuán)聚體用0.25指標(biāo)進(jìn)行評(píng)價(jià)[19-20], 分別按以下公式計(jì)算:
采用Excel 2016進(jìn)行數(shù)據(jù)整理, R語(yǔ)言進(jìn)行LSD多重比較, 分析不同施肥處理措施土壤有機(jī)碳含量的差異特征, 顯著性水平為0.05, Origin 9.0繪圖。所有結(jié)果均為3次測(cè)定結(jié)果的平均值。
長(zhǎng)期施肥處理下表層土壤(0~20 cm)理化性質(zhì)如表1所示。施肥可顯著提高土壤有機(jī)碳(SOC)和土壤全氮含量(TN,<0.05), 降低土壤容重。與CK處理相比, NPK、RSD、RSDNPK和BCNPK處理SOC含量分別增加43.13%、82.93%、79.15%和90.52%, 其中RSDNPK和BCNPK處理的SOC含量分別比NPK處理高25.17%、33.11%; 生物炭的添加顯著提高表層(0~20 cm)土壤有機(jī)碳儲(chǔ)量(SOCS), BCNPK處理相比CK增加90.52%, 相比NPK處理增加33.1%, RSD處理與RSDNPK處理均能顯著增加表層土壤有機(jī)碳儲(chǔ)量, 但兩者差異不大。RSDNPK處理土壤全氮含量相比RSD和NPK處理分別顯著增加62.00%和44.64%, RSD與NPK處理無(wú)顯著差異; RSDNPK處理表層土壤全氮儲(chǔ)量比BCNPK處理顯著增加29.55%。
表1 長(zhǎng)期不同施肥處理下表層(0~20 cm)土壤基本理化性質(zhì)
CK: 不施肥對(duì)照; NPK: 氮磷鉀無(wú)機(jī)肥配施; RSD: 秸稈還田; RSDNPK: 秸稈還田與氮磷鉀配施; BCNPK: 生物炭與氮磷鉀配施。同列不同小寫字母表示不同處理間差異顯著(<0.05)。CK: no fertilization; NPK: inorganic nitrogen, phosphorus and potassium fertilization; RSD: straw returning; RSDNPK: straw returning combined with NPK; BCNPK: biochar application combined with NPK. Different lowercase letters in the same column indicate significant differences among treatments at 0.05 level.
運(yùn)用濕篩法將CK處理及4種不同施肥方式下的土壤團(tuán)聚體進(jìn)行分級(jí), 分別得到>2 mm、0.25~2 mm、0.053~0.25 mm及<0.053 mm共4個(gè)粒級(jí)的土壤團(tuán)聚體, 其含量分布如圖1所示。隨著各級(jí)團(tuán)聚體粒徑的減小, 其含量呈現(xiàn)先增加后減小的趨勢(shì), 各處理7.4%~77.9%的土壤團(tuán)聚體集中在0.053~2 mm粒徑范圍。BCNPK處理和RSDNPK處理0.053~2 mm粒徑的團(tuán)聚體含量分別為76.4%和77.9%, 與CK處理相比, 分別增加6.9%和9.1%。RSD處理0.25~2 mm粒徑的團(tuán)聚體含量高達(dá)45.5%, 與CK處理相比, 顯著增加57.7%, 與NPK處理相比顯著增加27.1%。BCNPK處理和RSDNPK處理對(duì)土壤團(tuán)聚體影響效果相似, 兩個(gè)處理降低了>2 mm、<0.053 mm團(tuán)聚體含量。
圖1 長(zhǎng)期不同施肥處理不同粒徑土壤團(tuán)聚體含量
CK: 不施肥對(duì)照; NPK: 氮磷鉀無(wú)機(jī)肥配施; RSD: 秸稈還田; RSDNPK: 秸稈還田與氮磷鉀配施; BCNPK: 生物炭與氮磷鉀配施。不同小寫字母表示不同處理間差異顯著(<0.05)。CK: no fertilization; NPK: inorganic nitrogen, phosphorus and potassium fertilization; RSD: straw returning; RSDNPK: straw returning combined with NPK; BCNPK: biochar application combined with NPK. Different lowercase letters indicate significant differences among treatments at 0.05 level.
不同施肥處理土壤團(tuán)聚體MWD、GMD及0.25結(jié)果如表2所示。施肥能顯著提高土壤團(tuán)聚體MWD、GMD及0.25。團(tuán)聚體MWD大小依次為RSD處理>RSDNPK處理>BCNPK處理>NPK處理>CK處理, RSDNP比RSD處理團(tuán)聚體MWD顯著減小10.9%, BCNPK與NPK處理差異不顯著, 而RSDNPK處理比NPK處理顯著增加12.3%。團(tuán)聚體GMD大小順序與MWD一致, NPK、BCNPK和RSDNPK處理團(tuán)聚體GMD無(wú)顯著差異, RSDNPK處理比RSD處理減小15.38%。RSD處理團(tuán)聚體0.25最大, 比CK和RSDNPK處理分別增加55.9%、20.5%。RSDNPK與BCNPK處理0.25沒(méi)有顯著差異, BCNPK處理比NPK處理提高19.5%。
表2 長(zhǎng)期不同施肥處理土壤團(tuán)聚體穩(wěn)定性
WMD: 團(tuán)聚體平均重量直徑; GMD: 團(tuán)聚體平均幾何直徑;0.25: >0.25 mm團(tuán)聚體含量。CK: 不施肥對(duì)照; NPK: 氮磷鉀無(wú)機(jī)肥配施; RSD: 秸稈還田; RSDNPK: 秸稈還田與氮磷鉀配施; BCNPK: 生物炭與氮磷鉀配施。同列不同小寫字母表示不同處理間差異顯著(<0.05)。WMD: mean weight diameter of aggregates; GMD: mean geometric diameter of aggregates;0.25: content of aggregates > 0.25 mm. CK: no fertilization; NPK: inorganic nitrogen, phosphorus and potassium fertilization; RSD: straw returning; RSDNPK: straw returning combined with NPK; BCNPK: biochar application combined with NPK. Different lowercase letters in the same column indicate significant differences among treatments at 0.05 level.
4種施肥處理均能提高各粒級(jí)土壤團(tuán)聚體有機(jī)碳含量, 但效果確不盡相同。如表3所示, NPK、RSD處理各粒級(jí)土壤團(tuán)聚體有機(jī)碳含量增長(zhǎng)趨勢(shì)與CK處理相似: 隨著團(tuán)聚體粒徑的減小, 團(tuán)聚體有機(jī)碳含量呈增加—減小—增加的趨勢(shì); 而RSDNPK、BCNPK處理呈現(xiàn)隨土壤團(tuán)聚體粒徑減小, 團(tuán)聚體有機(jī)碳含量增加的趨勢(shì)。說(shuō)明生物炭及秸稈配施有助于提高土壤團(tuán)聚體有機(jī)碳含量, 從而穩(wěn)定土壤結(jié)構(gòu), 增加肥力。RSDNPK處理<0.053 mm的土壤團(tuán)聚體有機(jī)碳含量最高, 相比同粒級(jí)的CK處理顯著增加101.41%, 比NPK處理顯著增加36.85%; BCNPK處理0.053~0.25 mm土壤團(tuán)聚體有機(jī)碳含量相比CK處理顯著提高133.97%, 比NPK處理顯著增加47.97%; RSD處理>2 mm、<0.053 mm團(tuán)聚體有機(jī)碳含量相比CK處理分別顯著增加102.89%、89.07%。結(jié)果表明RSD處理能顯著增加土壤團(tuán)聚體有機(jī)碳的含量, BCNPK處理有助于提高土壤微團(tuán)聚體有機(jī)碳含量, RSDNPK處理土壤團(tuán)聚體有機(jī)碳含量, 除0.053~0.25 mm粒徑團(tuán)聚體外, 其余粒徑團(tuán)聚體沒(méi)有顯著提升。
大量研究表明, 除沙漠耕作土壤外, 耕作可降低土壤團(tuán)聚體的穩(wěn)定性, 改變土壤團(tuán)聚體的分布[21-22], 因此可通過(guò)生物炭和秸稈等有機(jī)物料添加保持農(nóng)田土壤團(tuán)聚體穩(wěn)定性, 保持和提升土壤肥力。侯曉娜等[9]對(duì)姜砂黑土的研究發(fā)現(xiàn), 生物炭、秸稈還田有利于大、中土壤團(tuán)聚體的形成, 但秸稈還田減小了<0.25 mm粒級(jí)土壤團(tuán)聚體含量, 而生物炭施用除對(duì)0.25~0.5 mm土壤團(tuán)聚體減少外, 在其余粒級(jí)土壤團(tuán)聚體都表現(xiàn)出顯著性增加。在黑壚土旱地農(nóng)田研究也表明, 生物炭的施用能促進(jìn)0.053~2 mm土壤團(tuán)聚體的形成, 團(tuán)聚體隨粒徑的減小而增多[23]。但本研究表明, 生物炭配施NPK(BCNPK)處理下土壤團(tuán)聚體含量呈現(xiàn)隨粒徑減小先增多后減小的趨勢(shì), 且70%的土壤團(tuán)聚粒徑集中在0.053~2 mm; 雖然施肥有助于形成粒徑為0.25~2 mm的中團(tuán)聚體, 但BCNPK處理中團(tuán)聚體含量較NPK處理沒(méi)有顯著性差異, 這可能因?yàn)樯锾勘旧碓诜纸膺^(guò)程并中并不能產(chǎn)生黏液促進(jìn)團(tuán)聚體的形成[24], 無(wú)法很好地團(tuán)聚粒徑較小的微團(tuán)聚體。由于秸稈分解物能膠結(jié)團(tuán)聚體[25], 本研究中秸稈添加(RSD和RSDNPK)處理較單施無(wú)機(jī)肥(NPK處理)顯著增大MWD和0.2,增強(qiáng)土壤團(tuán)聚體穩(wěn)定性, 這與田慎重等[26]在華北地區(qū)研究結(jié)果一致。本結(jié)果表明秸稈還田是改善紫色土坡耕地土壤結(jié)構(gòu)的有效措施。
土壤團(tuán)聚體是土壤保持肥力的重要結(jié)構(gòu), 有機(jī)碳又是土壤團(tuán)聚體重要的膠結(jié)劑[27], 長(zhǎng)期施肥能增加紫色土農(nóng)田土壤團(tuán)聚體有機(jī)碳含量[28]。生物炭與無(wú)機(jī)氮磷鉀長(zhǎng)期配施能增加紫色土坡耕地土壤有機(jī)質(zhì)含量。添加生物炭能減小土壤團(tuán)聚體粒徑, 增加土壤惰性碳含量, 減緩?fù)寥烙袡C(jī)質(zhì)流失[29], 因此長(zhǎng)期施用會(huì)穩(wěn)定土壤碳庫(kù)并可能增加土壤潛在碳庫(kù)?,F(xiàn)今對(duì)施用生物炭研究較多, 但對(duì)其長(zhǎng)期施用后期效果研究較少。本研究表明BCNPK處理有助于提高土壤微團(tuán)聚體有機(jī)碳含量, 除0.053~0.25 mm粒徑團(tuán)聚體外, 其余粒徑團(tuán)聚體有機(jī)碳有顯著提升, 與NPK處理相比, BCNPK處理對(duì)提高SOC及土壤有機(jī)碳儲(chǔ)量效果則最為顯著, 這可能是由于無(wú)機(jī)氮磷鉀的長(zhǎng)期施用會(huì)降低土壤微團(tuán)聚體有機(jī)碳儲(chǔ)量所致[30]。所以長(zhǎng)期合理配施生物炭與無(wú)機(jī)氮磷鉀是維持和提高紫色土坡耕土壤肥力的有效管理措施。
秸稈還田主要通過(guò)增加腐殖質(zhì)含量來(lái)增加土壤有機(jī)質(zhì), 提高土壤肥力[31], 長(zhǎng)期秸稈還田能顯著提高農(nóng)田土壤有機(jī)碳含量和作物產(chǎn)量[32]。例如韓瑋等[33]發(fā)現(xiàn)秸稈施用能顯著提高水稻土土壤有機(jī)質(zhì)含量; 趙士誠(chéng)等[34]對(duì)潮土研究發(fā)現(xiàn), 秸稈還田與無(wú)機(jī)肥配施能顯著提高土壤有機(jī)碳含量。本試驗(yàn)中, RSDNPK處理產(chǎn)量最高, 比CK處理增加高達(dá)262%, 比NPK 處理增加13.8%, 說(shuō)明紫色土坡耕地長(zhǎng)期施用秸稈還田對(duì)于提高作物產(chǎn)量效果顯著。不同還田年限對(duì)農(nóng)田土壤團(tuán)聚體及有機(jī)碳影響效果不一。張聰?shù)萚35]依托甘肅農(nóng)業(yè)大學(xué)平?jīng)鲈囼?yàn)站長(zhǎng)期玉米全量秸稈還田定位試驗(yàn), 研究不同秸稈還田年限對(duì)土壤有機(jī)碳的影響, 發(fā)現(xiàn)隨著秸稈還田年限的增加土壤有機(jī)碳增加減緩, 這可能是因?yàn)殚L(zhǎng)期添加秸稈, 土壤碳庫(kù)不斷增大, 使得碳庫(kù)增加速度減緩; 竇莉洋[36]進(jìn)行不同土壤類型長(zhǎng)期秸稈還田試驗(yàn)發(fā)現(xiàn), 連續(xù)秸稈還田能提高不同粒級(jí)土壤團(tuán)聚體穩(wěn)定性。以往研究表明, 秸稈還田能激發(fā)土壤原有的有機(jī)碳的分解[35], 不同母質(zhì)條件下發(fā)育的同類土壤也有較大差異, 這可能與土壤性質(zhì)和有機(jī)碳含量有關(guān)。以紅壤為例, 長(zhǎng)期施肥處理下紅砂巖風(fēng)化物、紅黏土、紫色砂巖風(fēng)化物、花崗巖風(fēng)化物4種成土母質(zhì)發(fā)育下的紅壤團(tuán)聚體有機(jī)碳分布均不相同。不同母質(zhì)紫色土有機(jī)碳和水穩(wěn)定性團(tuán)聚體穩(wěn)定性差異較大[37], 且長(zhǎng)期秸稈還田有可能使得不同母質(zhì)土壤團(tuán)聚體有機(jī)碳含量和分布發(fā)生變化。
表3 長(zhǎng)期不同施肥處理各粒級(jí)團(tuán)聚體有機(jī)碳(SOC)含量
CK: 不施肥對(duì)照; NPK: 氮磷鉀無(wú)機(jī)肥配施; RSD: 秸稈還田; RSDNPK: 秸稈還田與氮磷鉀配施; BCNPK: 生物炭與氮磷鉀配施。同列不同小寫字母表示同一團(tuán)聚體粒級(jí)下不同處理間差異顯著(<0.05), 同行不同大寫字母表示同一處理下不同團(tuán)聚體粒級(jí)之間差異顯著。CK: no fertilization; NPK: inorganic nitrogen, phosphorus and potassium fertilization; RSD: straw returning; RSDNPK: straw returning combined with NPK; BCNPK: biochar application combined with NPK. Different lowercase letters in the same column indicate significant differences among treatments at 0.05 level. Different capital letters in the same row indicate significant differences among aggregates with different sizes at 0.05 level.
1)與CK處理相比, 施肥均能顯著提高土壤有機(jī)碳、全氮含量及儲(chǔ)量, 其中BCNPK處理對(duì)提高有機(jī)碳儲(chǔ)量最顯著, 而RSDNPK處理對(duì)提高土壤全氮儲(chǔ)量最為顯著。
2)所有試驗(yàn)處理下土壤團(tuán)聚體主要集中在0.053~2 mm, 其中RSD處理土壤團(tuán)聚體又主要集中在 0.25~2 mm, 且該處理MWD、GMD及0.25均為最大, 說(shuō)明該處理土壤團(tuán)聚體結(jié)構(gòu)最為穩(wěn)定; 相比CK處理, BCNPK處理和RSDNPK處理能降低大團(tuán)聚體(>2 mm)和微團(tuán)聚體(<0.053 mm)含量, 且顯著提高M(jìn)WD、GMD及0.25, 表明BCNPK和RSDNPK處理對(duì)穩(wěn)定土壤團(tuán)聚體結(jié)構(gòu)效果顯著。
3)與NPK處理相比, RSDNPK和BCNPK處理均顯著增加不同粒級(jí)土壤團(tuán)聚體有機(jī)碳含量, 并且其團(tuán)聚體有機(jī)碳含量隨土壤團(tuán)聚粒徑減小而增加。因此, 長(zhǎng)期施用生物炭及秸稈是改善紫色土旱地土壤結(jié)構(gòu), 提升土壤肥力的有效措施。
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Effect of long-term application of biochar and straw on soil organic carbon in purple soil aggregates of sloping uplands*
LIN Hongyu1,2, ZHOU Minghua1**, ZHANG Bowen1,2, LI Ziyang1,2, ZHU Bo1
(1. Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China)
The effects of biochar and straw application on the distribution of soil organic carbon (SOC) in purple soil aggregations of sloping uplands were explored from a long-term perspective. Five long-term fertilization treatments were included: no fertilizer (control, CK), mineral fertilizer application (NPK), crop straw residue application (RSD), a combined application of biochar and mineral fertilizer (BCNPK), and a combined application of crop straw residue and mineral fertilizer (RSDNPK).Soil samples were separated into >2 mm large macroaggregates, 0.25-2 mm small macroaggregates, 0.053-0.25 mm microaggregates, and <0.053 mm slit-clay microaggregatesby sieving. The mass fraction of soil aggregations, organic carbon content, mean weight diameter, and geometric mean diameter of aggregations were measured. The results showed that the application of biochar and straw increased SOC content and stabilized the structure of aggregations compared with both CK and NPK treatments. In comparison with CK, SOC contents significantly increased by 43.1% under NPK treatment, 82.9% under RSD treatment, 79.1% under RSDNPK treatment, and 90.5% under BCNPK treatment. SOC stocks of topsoil increased significantly by 34.0% under NPK treatment, 68.2% under RSD treatment, 65.2% under RSDNPK treatment, and 74.3% under BCNPK treatment compared with CK treatment. In addition, the content of 0.25-2 mm aggregates of RSD treatment reached 45.5%, which was 57.7% higher than that of CK; more soil aggregations were concentrated on 0.25-2 mm aggregates. As compared with CK, the SOC content of 0.053-0.25 mm aggregates was reduced by straw and biochar treatments. The trends for NPK and RSDtreatments were similar to those for CK, but RSDNPK and BCNPK treatmentshowedan increasing trend in organic carbon content in aggregates with decreased particle size. RSDNPK and BCNPK treatments significantly increased the SOC content and enhanced the stability of soil structure, but BCNPK treatment was superior to RSDNPK treatment in increasing SOC content, and RSDNPK treatment was more effective in stabilizing soil structure. BCNPK treatment and RSDNPK treatment are therefore effective management measures that can maintain and improve soil fertility of purple-soil-cultivated land.
Soil aggregates; Biochar; Crop straw; Soil organic carbon; Purple soil
S153.6
* 水體污染控制與治理科技重大專項(xiàng)(2017ZX07101001)、國(guó)家自然科學(xué)基金項(xiàng)目(41573079)和中國(guó)科學(xué)院率先行動(dòng)百人計(jì)劃擇優(yōu)項(xiàng)目資助
周明華, 主要研究方向?yàn)樘嫉锏厍蚧瘜W(xué)循環(huán)與全球變化。E-mail: mhuazhou@imde.ac.cn
林洪羽, 主要研究方向?yàn)橥寥捞嫉h(huán)。E-mail: linhongyu17@mails.ucas.ac.cn
2019-08-19
2019-09-30
* This study was supported by the National Science and Technology Major Project for Water Pollution Control and Treatment of China (2017ZX07101001), the National Natural Science Foundation of China (41573079) and the Pioneer Hundred Talent Program of Chinese Academy of Sciences.
, E-mail: mhuazhou@imde.ac.cn
Aug. 19, 2019;
Sep. 30, 2019
10.13930/j.cnki.cjea.190614
林洪羽, 周明華, 張博文, 李子陽(yáng), 朱波. 生物炭及秸稈長(zhǎng)期施用對(duì)紫色土坡耕地土壤團(tuán)聚體有機(jī)碳的影響[J]. 中國(guó)生態(tài)農(nóng)業(yè)學(xué)報(bào)(中英文), 2020, 28(1): 96-103
LIN H Y, ZHOU M H, ZHANG B W, LI Z Y, ZHU B. Effect of long-term application of biochar and straw on soil organic carbon in purple soil aggregates of sloping uplands[J]. Chinese Journal of Eco-Agriculture, 2020, 28(1): 96-103
中國(guó)生態(tài)農(nóng)業(yè)學(xué)報(bào)(中英文)2020年1期