耕作方式對(duì)土壤水分入滲、有機(jī)碳含量及土壤結(jié)構(gòu)的影響*

楊永輝,武繼承,張潔梅,潘曉瑩,王 越,何 方

(1.河南省農(nóng)業(yè)科學(xué)院植物營(yíng)養(yǎng)與資源環(huán)境研究所 鄭州 450002; 2.農(nóng)業(yè)部作物高效用水科學(xué)觀測(cè)實(shí)驗(yàn)站 原陽(yáng) 453514)

耕作方式對(duì)土壤水分入滲、有機(jī)碳含量及土壤結(jié)構(gòu)的影響*

楊永輝1,2,武繼承1,2,張潔梅1,2,潘曉瑩1,2,王 越1,2,何 方1,2

(1.河南省農(nóng)業(yè)科學(xué)院植物營(yíng)養(yǎng)與資源環(huán)境研究所 鄭州 450002; 2.農(nóng)業(yè)部作物高效用水科學(xué)觀測(cè)實(shí)驗(yàn)站 原陽(yáng) 453514)

為探明不同耕作方式對(duì)土壤剖面結(jié)構(gòu)、水分入滲過(guò)程等的作用機(jī)理,采集田間長(zhǎng)期定位耕作措施(常規(guī)耕作、免耕、深松)試驗(yàn)中的原狀土柱(0～100 cm)及0～10 cm、10～20 cm、…、90～100 cm環(huán)刀樣、原狀土及混合土樣,通過(guò)室內(nèi)模擬試驗(yàn)進(jìn)行了0～100 cm土層土壤入滲過(guò)程和飽和導(dǎo)水率的測(cè)定,分析了不同土層的土壤有機(jī)碳含量、土壤結(jié)構(gòu)特征及相互關(guān)系。結(jié)果表明: 從土柱頂部開(kāi)始供水(恒定水頭)到水分全部入滲到土柱底部的時(shí)間為: 常規(guī)耕作＞免耕＞深松; 土柱土壤入滲速率和累積入滲量為: 深松＞免耕＞常規(guī)耕作; 土柱累積蒸發(fā)量為: 常規(guī)耕作＞免耕＞深松。土壤的飽和導(dǎo)水率表現(xiàn)為: 0～10 cm和50～60 cm土層,免耕＞深松＞常規(guī)耕作; 20～50 cm和60～100 cm土層,深松＞免耕＞常規(guī)耕作。隨土層的加深,＞0.25 mm水穩(wěn)性團(tuán)聚體含量和土壤有機(jī)碳含量均表現(xiàn)為先增加(10～20 cm)再降低的趨勢(shì)。在0～40 cm土層和80～100 cm土層,均以深松處理＞0.25 mm水穩(wěn)性團(tuán)聚體含量最高。在60 cm以上土層,土壤有機(jī)碳含量表現(xiàn)為: 免耕＞深松＞常規(guī)耕作,而60 cm土層以下土壤有機(jī)碳顯著降低,均低于4 g·kg-1,且在70 cm以下土層,常規(guī)耕作＞免耕＞深松。綜上,耕作措施能夠改變土壤有機(jī)碳含量,改善土壤結(jié)構(gòu),促進(jìn)土壤蓄水保墑; 深松更利于水分就地入滲,而免耕則更利于有機(jī)碳的提升和水分的儲(chǔ)存,其作用深度在0～60 cm土層。

常規(guī)耕作; 深松; 免耕; 水分入滲; 土壤有機(jī)碳; 土壤結(jié)構(gòu)

免耕、深松與表土作業(yè)等土壤耕作措施可改善土壤結(jié)構(gòu)[1-2],降低坡耕旱地水土流失,增強(qiáng)土壤微生物活性,降低作物干旱脅迫的傷害[3]。同時(shí),可提高土壤肥力[4]和土壤孔隙度,降低土壤容重,促進(jìn)作物生長(zhǎng)[5]。秸稈還田+免耕可增加表層土壤的通氣孔隙,降低其無(wú)效孔隙,改善土壤結(jié)構(gòu),提高土壤持水性能,增加土壤水分庫(kù)容[6]。少耕或免耕有利于接納降雨和水分儲(chǔ)存,促進(jìn)作物產(chǎn)量與水分利用率的提高[7-9]。免耕+秸稈覆蓋能有效保持土壤剖面水分含量,減少土壤蒸發(fā)量[10],提高土壤的飽和導(dǎo)水率[11]。于同艷等[12]研究表明,免耕雖不利于水分入滲,但可有效保持土壤中的水分。楊永輝等[13]研究表明,連續(xù)2年免耕可改善土壤結(jié)構(gòu),降低土壤容重,改善土壤孔隙狀況。深松能夠打破土壤犁底層,改善土壤孔隙,促進(jìn)土壤蓄水保墑,有利于作物根系利用深層土壤水[14],且深松能夠顯著提高＞0.25 mm水穩(wěn)性團(tuán)聚體含量,有效提高土壤的儲(chǔ)水量[15]。深松+地面覆蓋可改善土壤團(tuán)粒結(jié)構(gòu),提高土壤剖面的水分狀況[16]。免耕與深松輪作能顯著提高土體的蓄水量[17-18]。以往的研究多偏重于免耕覆蓋或深松覆蓋或二者輪作,且研究深度為犁底層以上的土壤,對(duì)于深層土壤的影響,以及長(zhǎng)期單獨(dú)深松或免耕對(duì)土壤剖面物理特征、入滲過(guò)程及有機(jī)碳分布特征及其作用深度等影響如何目前尚鮮見(jiàn)報(bào)道,需要深入研究,以闡明長(zhǎng)期深松和免耕對(duì)土壤的作用機(jī)理。

筆者對(duì)長(zhǎng)期深松和免耕條件下 0～100 cm土層的土壤結(jié)構(gòu)、水分入滲過(guò)程與蒸發(fā)特征、有機(jī)碳分布及相互關(guān)系進(jìn)行了研究,為闡明在小麥(Triticum aestivum)、玉米(Zea mays)輪作過(guò)程中,長(zhǎng)期進(jìn)行深松和免耕對(duì)土壤剖面物理特征的改善及其作用機(jī)理提供科學(xué)依據(jù)。

1 材料與方法

1.1 研究區(qū)概況

試驗(yàn)設(shè)置在河南省禹州試驗(yàn)基地(113°03′～113°39′E,33°59′～34°24′N(xiāo),海拔116.1 m)進(jìn)行,多年平均降水量674.9 mm,其中60%以上降雨集中在夏季; 土壤類(lèi)型為褐土。研究區(qū)地勢(shì)平坦,耕層土壤有機(jī)質(zhì)含量12.3 g·kg-1、全氮含量0.80 g·kg-1、水解氮含量47.82 mg·kg-1、速效磷含量6.66 mg·kg-1、速效鉀含量114.8 mg·kg-1。研究區(qū)為小麥-玉米輪作區(qū)。2014年度小麥品種為‘周麥22’,玉米品種為‘鄭單958’。土壤機(jī)械組成為: 砂粒(2～0.02 mm)占59.1%,粉粒(0.02～0.002 mm)占22.5%,黏粒(＜0.002 mm)占18.4%。

1.2 試驗(yàn)設(shè)計(jì)

長(zhǎng)期定位試驗(yàn)于2006年10月中旬小麥播種時(shí)開(kāi)始,耕作措施在每年小麥播種時(shí)實(shí)施,玉米均為免耕播種。試驗(yàn)共設(shè)置3個(gè)處理: 常規(guī)耕作(耕作深度為15 cm)、免耕、深松(深度30 cm),試驗(yàn)小區(qū)未進(jìn)行秸稈還田。肥料采用N25P15K15復(fù)合型肥料,在小麥播種時(shí)一次性底施。在小麥播種前將肥料均勻撒于小區(qū)內(nèi),然后進(jìn)行常規(guī)耕作和深松; 免耕的施肥方式為小麥、玉米播種后點(diǎn)施。

于2014年玉米收獲后(10月12日)從定位試驗(yàn)每個(gè)處理的 3個(gè)重復(fù)小區(qū)中間位置采用原狀土柱采集器采集0～100 cm原狀土柱,測(cè)定土壤入滲過(guò)程。即將有機(jī)玻璃管放入采集器中,用鐵錘于采集器上方進(jìn)行豎直敲擊,待采集器進(jìn)入土中深度110 cm時(shí),將采集器拔出,并從采集器的下方取出采集器內(nèi)的有機(jī)玻璃管。同時(shí)在采集原狀土柱的旁邊挖剖面,并分層采集(0～10 cm、10～20 cm、…、90～100 cm)環(huán)刀樣(測(cè)定飽和導(dǎo)水率)、原狀土(測(cè)定團(tuán)粒結(jié)構(gòu))及混合土壤樣品(測(cè)定土壤有機(jī)碳含量)。每個(gè)處理取3個(gè)重復(fù)帶回室內(nèi)進(jìn)行分析。

1.3 測(cè)定項(xiàng)目與方法

1)土壤飽和導(dǎo)水率采用恒定水頭法[19]測(cè)定,水穩(wěn)性團(tuán)聚體采用維諾夫法[20](濕篩法)分級(jí)測(cè)定,土壤有機(jī)碳采用改進(jìn)的外加熱重鉻酸鉀氧化法[21]測(cè)定。

2)土壤入滲過(guò)程測(cè)定。將田間采集的原狀土柱(土柱長(zhǎng)110 cm,直徑20 cm,壁厚1 cm)帶到室內(nèi),放置,待土柱含水量為 8%～10%左右(表 1),進(jìn)行土柱水分入滲過(guò)程的觀測(cè)。觀測(cè)前,對(duì)土柱進(jìn)行稱(chēng)重并記錄其初始重量。在土柱(透明有機(jī)玻璃)側(cè)面,平行于土柱方向粘貼帶有刻度的坐標(biāo)紙,從上至下標(biāo)注土柱的深度,精確度為1 mm。采用馬氏瓶在土柱上方(土柱上方留有 10 cm高度空間,以接納供水)進(jìn)行恒定水頭的供水。調(diào)節(jié)馬氏瓶高度,土柱上方的水層厚度控制在5 cm左右。從土柱供水時(shí)開(kāi)始計(jì)時(shí),并觀測(cè)土柱剖面的水分入滲距離,每個(gè)土柱上觀測(cè)3組數(shù)據(jù)(土柱側(cè)面等間距豎直粘貼3條坐標(biāo)紙,以獲得 3組數(shù)據(jù),計(jì)算其平均值作為觀測(cè)值,最小刻度為mm),每個(gè)處理3個(gè)土柱共9組數(shù)據(jù)計(jì)算平均值。開(kāi)始觀測(cè)時(shí)每分鐘觀測(cè) 1次土柱水分入滲距離,同時(shí)觀測(cè)馬氏瓶中水層下降高度。待入滲距離推進(jìn)緩慢時(shí),延長(zhǎng)觀測(cè)記錄數(shù)據(jù)時(shí)間。待水分入滲至土柱底層時(shí),測(cè)量滲流出來(lái)的水分,當(dāng)滲流水量恒定時(shí)(土柱含水量達(dá)到飽和,見(jiàn)表 1),停止對(duì)土柱進(jìn)行供水,并用膠帶封住土柱底部,防止水分從土柱底部流出。觀測(cè)結(jié)束后計(jì)算土柱累積入滲量、入滲速率。并采用精確度為1 g的電子天平對(duì)土柱進(jìn)行稱(chēng)重,獲得土柱飽和后的總重量。每隔1 d對(duì)土柱稱(chēng)重 1次,觀測(cè)其累計(jì)蒸發(fā)量,觀測(cè)前后土柱含水量見(jiàn)表1。

表1 不同土柱初始含水量、飽和含水量及蒸發(fā)試驗(yàn)結(jié)束后的含水量Table 1 Initial water content,saturated water content and water content after the end of evaporation experiment %

土柱入滲速率計(jì)算方法如下:

式中:V為滲透速率,mm·min-1;Qn為n次馬氏瓶中進(jìn)入土柱的水量,mL,即cm3;tn為每次滲透所間隔時(shí)間,min;S為土柱橫截面積,cm2; 10為由cm換算成mm所乘倍數(shù); 60為將滲透速率(V)單位 mm·min-1轉(zhuǎn)換為mm·h-1。

1.4 數(shù)據(jù)處理

不同結(jié)果數(shù)值均為3次重復(fù)的算術(shù)平均值,且所得數(shù)據(jù)采用Microsoft Excel及SPSS軟件進(jìn)行處理。

2 結(jié)果與分析

2.1 長(zhǎng)期不同耕作措施下水分入滲規(guī)律分析

2.1.1 水分運(yùn)移規(guī)律分析

圖1 長(zhǎng)期不同耕作措施對(duì)土壤入滲特征的影響Fig.1 Soil water infiltration characteristics under different long-term tillage measures

不同耕作措施對(duì)水分在土壤剖面中的運(yùn)移規(guī)律各異(圖1)。由于3個(gè)處理的土柱初始含水量較低(表1),水分入滲較為迅速,3種耕作方式下,在很短時(shí)間內(nèi)到達(dá)35 cm處,其中以深松處理最快。之后土壤水分在土壤剖面上的入滲濕潤(rùn)峰行進(jìn)減緩,且各土柱之間差異顯著(P＜0.01),常規(guī)耕作處理到達(dá)相同距離的時(shí)間明顯增加。而深松處理的水分運(yùn)移仍較快,在不到3 h入滲到土柱底部; 免耕處理水分運(yùn)移到底部的時(shí)間是深松處理的2倍,常規(guī)耕作則超過(guò)24 h。說(shuō)明深松打破了犁底層,使得土壤上下層更加通透(運(yùn)移曲線上下平直),更利于水分就地入滲; 而常規(guī)耕作因?yàn)槔绲讓拥淖韪?入滲能力明顯降低; 免耕雖也受到犁底層的影響,但由于其改善了表層土壤結(jié)構(gòu),進(jìn)而入滲能力大于常規(guī)耕作。

2.1.2 累計(jì)入滲量分析

不同耕作措施土壤的初始入滲量基本相當(dāng),但隨時(shí)間的推移,差異逐漸增大(圖2),且達(dá)極顯著水平(P＜0.01)。在土壤水分進(jìn)入土壤3 h后,深松處理的土柱土壤到達(dá)飽和。常規(guī)耕作處理達(dá)到土壤飽和含水量的時(shí)間遠(yuǎn)大于其他處理,且其累計(jì)入滲量均小于其他處理。在相同時(shí)間內(nèi),累計(jì)入滲量大小為: 深松＞免耕＞常規(guī)耕作(P＜0.01)。說(shuō)明深松后土壤蓄水容量顯著提高,免耕的擴(kuò)蓄增容效果也十分明顯,分別較常規(guī)耕作提高27.3%和22.8%。

2.1.3 入滲速率分析

隨時(shí)間的推移,土壤入滲速率逐漸降低。在整個(gè)入滲過(guò)程中,以深松處理的入滲速率最高,其次為免耕處理,常規(guī)耕作處理最低(P＜0.05),尤其在0～2.0 h間差異較大(P＜0.01)(圖3)。隨時(shí)間的推移,各處理的入滲速率降低幅度逐漸減小,最終趨于恒定值,且深松與免耕仍高于常規(guī)耕作(P＜0.05)。

圖2 長(zhǎng)期不同耕作措施對(duì)土壤累計(jì)入滲量的影響Fig.2 Soil cumulative infiltrations under different long-term tillage measures

圖3 長(zhǎng)期不同耕作措施對(duì)土壤入滲速率的影響Fig.3 Soil infiltration rates under different long-term tillage measures

2.2 累計(jì)蒸發(fā)量分析

隨時(shí)間的推移,不同耕作處理的土壤累計(jì)蒸發(fā)量逐漸增大,且差異顯著(圖4)(P＜0.01)。雖然常規(guī)耕作處理飽和時(shí)的含水率低于其他處理(表1),但其初始及隨后的蒸發(fā)量仍明顯高于其他處理(P＜0.01)。而免耕處理的蒸發(fā)量均顯著低于其他處理(P＜0.01),其次為深松處理。說(shuō)明實(shí)施深松和免耕耕作能夠有效減少土壤的無(wú)效蒸發(fā)量。

2.3 不同土壤剖面飽和導(dǎo)水率差異分析

從圖5中可知,20～30 cm土層的土壤飽和導(dǎo)水率最低,而10～20 cm土層最高(免耕處理除外),隨土層的加深,土壤飽和導(dǎo)水率趨于平緩。在0～10 cm土層,土壤飽和導(dǎo)水率表現(xiàn)為: 免耕＞深松＞常規(guī)耕作(P＜0.05); 在10～20 cm土層,深松處理明顯高于其他處理(P＜0.05),這可能是深松后作物根系和蚯蚓活動(dòng)頻繁所致; 在20～30 cm土層,各處理之間差異較小(P＞0.05),但仍以深松處理的飽和導(dǎo)水率最高; 30～40 cm土層,各處理的土壤飽和導(dǎo)水率均增大,其中仍以深松處理最高,其次為免耕處理,常規(guī)耕作最低(P＜0.05)。隨土層的進(jìn)一步加深,各處理的土壤飽和導(dǎo)水率趨于穩(wěn)定,但整體來(lái)看,60 cm以下土層,免耕和常規(guī)耕作處理土壤飽和導(dǎo)水率較低,而深松處理土壤飽和導(dǎo)水率較高(P＜0.05)。說(shuō)明經(jīng)過(guò)長(zhǎng)期免耕和深松措施后,土壤剖面導(dǎo)水性能提高,尤其是20～30 cm以上土層效果更為顯著,深松處理效果最佳。

圖4 長(zhǎng)期不同耕作措施對(duì)土壤蒸發(fā)過(guò)程的影響Fig.4 Soil evaporations under different long-term tillage measures

圖5 長(zhǎng)期不同耕作措施對(duì)剖面土壤飽和導(dǎo)水率的影響Fig.5 Soil saturated hydraulic conductivities under different long-term tillage measures

2.4 不同耕作措施0～100 cm土層土壤有機(jī)碳分布特征

圖6顯示,不同耕作處理土壤有機(jī)碳含量在40 cm以上土層含量豐富,特別是20 cm以上的表層,40～70 cm為含量過(guò)渡層,70 cm以下為穩(wěn)定層,總體隨深度增加而衰減。在 60 cm以上土層,均以免耕處理的土壤有機(jī)碳含量最高,其次為深松處理,常規(guī)耕作最低。而70～100 cm土層土壤有機(jī)碳變化較平緩,其有機(jī)碳含量為2～4 g·kg-1。在80～100 cm土層,常規(guī)耕作處理的土壤有機(jī)碳均高于免耕和深松處理。說(shuō)明經(jīng)過(guò)長(zhǎng)期免耕和深松促進(jìn)了根系的生長(zhǎng)和土壤生物的活動(dòng),土體有機(jī)碳得到改善的作用深度達(dá)60 cm以上。

圖6 長(zhǎng)期不同耕作措施對(duì)0～100 cm土層有機(jī)碳含量的影響Fig.6 Distribution characteristics of soil organic carbon in 0-100 cm soil layer under different long-term tillage measures

2.5 不同耕作措施0～100 cm土層＞0.25 mm水穩(wěn)性團(tuán)聚體含量分析

＞0.25 mm水穩(wěn)性團(tuán)聚體含量表征了土壤結(jié)構(gòu)的穩(wěn)定性。從圖7可知,隨土層的加深,＞0.25 mm水穩(wěn)性團(tuán)聚體含量表現(xiàn)為先增加再顯著降低的趨勢(shì)。在0～10 cm和10～20 cm土層,＞0.25 mm水穩(wěn)性團(tuán)聚體含量表現(xiàn)為: 深松＞免耕＞常規(guī)耕作(P＜0.05)。在0～40 cm和80～100 cm土層,均以深松處理＞0.25 mm水穩(wěn)性團(tuán)聚體含量最高(P＜0.05)。常規(guī)耕作處理除70～90 cm土層＞0.25 mm水穩(wěn)性團(tuán)聚體含量較高外,其他土層均最低。說(shuō)明不同耕作措施改善了土壤剖面的團(tuán)粒結(jié)構(gòu),提高了土壤結(jié)構(gòu)的穩(wěn)定性,尤其是 60 cm以上土層。

圖7 長(zhǎng)期不同耕作措施對(duì)0～100 cm土層＞0.25 mm團(tuán)聚體含量分布特征的影響Fig.7 Distribution characteristics of ＞ 0.25 mm aggregate content in 0-100 cm soil layer under different long-term tillage measures

2.6 ＞0.25 mm 水穩(wěn)性團(tuán)聚體含量、有機(jī)碳含量及飽和導(dǎo)水率相關(guān)性分析

＞0.25 mm水穩(wěn)性團(tuán)聚體含量與土壤有機(jī)碳含量及土壤飽和導(dǎo)水率、土壤有機(jī)碳含量與土壤飽和導(dǎo)水率均表現(xiàn)為二次曲線關(guān)系(圖8),且相關(guān)性均為極顯著水平(P＜0.01)。隨土壤有機(jī)碳含量的增加,＞0.25 mm水穩(wěn)性團(tuán)聚體含量增加,土壤飽和導(dǎo)水率則表現(xiàn)為先降低再增加的趨勢(shì); 隨著＞0.25 mm水穩(wěn)性團(tuán)聚體含量增加到一定閥值(占總團(tuán)聚體 30%)后繼續(xù)增加,飽和導(dǎo)水率呈逐漸增加趨勢(shì)。說(shuō)明合理的耕作措施能夠提高土壤中的有機(jī)碳,從而改善土壤結(jié)構(gòu),促進(jìn)了土壤滲透能力的提高。

圖8 ＞0.25 mm團(tuán)聚體含量、飽和導(dǎo)水率及土壤有機(jī)碳相關(guān)性分析Fig.8 Correlation analysis between ＞0.25 mm soil aggregate content,saturated hydraulic conductivity and soil organic carbon content

3 結(jié)論與討論

深松、免耕可促進(jìn)土壤有機(jī)質(zhì)含量提高,改善土壤結(jié)構(gòu)[22,24-25],提高土壤結(jié)構(gòu)的穩(wěn)定性,改善土壤的水分環(huán)境[26]。進(jìn)行長(zhǎng)期深松和免耕會(huì)對(duì)剖面土壤的物理性質(zhì)產(chǎn)生重要影響。本研究發(fā)現(xiàn),在35 cm以上土層,水分運(yùn)移較快,而以深松處理最快。但在35 cm以下,常規(guī)耕作處理水分運(yùn)移速度明顯減緩,深松處理水分運(yùn)移較快。最終水分從土柱頂部入滲到底層的時(shí)間為: 常規(guī)耕作＞免耕＞深松。在0～2.0 h時(shí)間段各處理的入滲速率差異較大,且以深松處理最大,其次為免耕處理,常規(guī)耕作處理最低。隨時(shí)間的推移,各處理的入滲速率逐漸降低,并趨于恒定,且仍以深松處理最高,其次為免耕處理。土壤飽和導(dǎo)水率反映了不同土層之間土壤結(jié)構(gòu)的差異,而水分在土壤中的蓄存能力反映了不同措施對(duì)土壤結(jié)構(gòu)的改善能力。以往的研究多偏重于耕層,對(duì)于土壤剖面不同土層而言,本研究發(fā)現(xiàn),在0～10 cm和50～60 cm 土層,免耕處理更利于土壤飽和導(dǎo)水率的提高,其次為深松處理,常規(guī)耕作處理最低; 而在10～50 cm和60～100 cm土層,深松處理最高。說(shuō)明深松打破了犁底層,改善了土壤孔隙狀況[14],增加了土壤的通透性[27],促進(jìn)了水分就地入滲,并向更深土層的運(yùn)移[28],提高土體的含水量[16]。而免耕條件下形成的良好土體結(jié)構(gòu),使其有效毛細(xì)管增多,且孔管連續(xù)不間斷,從而有利于水分的快速移動(dòng)[29],改善土體的入滲能力。這與高建華等[30]和于同艷等[12]研究結(jié)果相反,而與 Dao[31]和 Hati等[32]研究結(jié)果一致,這可能與免耕時(shí)間[33]、土壤類(lèi)型、種植制度等有關(guān),需要進(jìn)一步研究。此外,實(shí)施免耕和深松能夠提高土壤的累積入滲量,增加土壤水分庫(kù)容量,且降低了土壤的無(wú)效蒸發(fā),各處理中,深松更利于水分入滲,而免耕更利于水分的保持。而有研究表明[18],深松1年后進(jìn)行免耕也能促進(jìn)土壤蓄水保墑,而在長(zhǎng)期深松后進(jìn)行免耕的結(jié)果如何,需要進(jìn)一步研究。

土壤入滲過(guò)程及蓄水能力與土壤結(jié)構(gòu)[34]和有機(jī)質(zhì)含量[35]緊密相關(guān),可通過(guò)提高土壤有機(jī)質(zhì)來(lái)改善土壤結(jié)構(gòu),進(jìn)而調(diào)節(jié)水分在土壤中的轉(zhuǎn)化、保持與供應(yīng),從而提高土壤的生產(chǎn)與生態(tài)功能。本研究發(fā)現(xiàn),土壤有機(jī)碳含量隨土層的加深而先增加(10～20 cm)再降低,到 70 cm以下土層土壤有機(jī)碳趨于穩(wěn)定。在 60 cm土層以上,均以免耕處理的土壤有機(jī)碳含量最高,其次為深松處理,常規(guī)耕作處理最低。說(shuō)明長(zhǎng)期免耕和深松有利于水分的保持,促進(jìn)了作物根系的生長(zhǎng)和土壤生物的活動(dòng),而作物根系殘留物或根系分泌物和土壤生物糞便又促進(jìn)了土壤有機(jī)碳含量提高,改善了土壤結(jié)構(gòu)。因此,＞0.25 mm水穩(wěn)性團(tuán)聚體含量隨土層的加深也表現(xiàn)為先增加(10～20 cm)再降低的趨勢(shì)。除60～80 cm土層外,均以深松處理＞0.25 mm水穩(wěn)性團(tuán)聚體含量最高,其次為免耕處理,特別在60 cm以上土層,效果更為顯著。陳強(qiáng)等[36]的研究也得到了相同結(jié)論,而高建華等[30]研究表明免耕對(duì)土壤結(jié)構(gòu)的改良并不明顯,這可能與耕作時(shí)間或土壤類(lèi)型有關(guān),需要進(jìn)一步研究。此外,相關(guān)研究?jī)H基于表層土壤,而對(duì)于深層土壤的影響研究涉及較少。

綜上,合理的長(zhǎng)期耕作措施能夠提高土壤剖面中的有機(jī)碳含量,從而改善土體土壤結(jié)構(gòu),促進(jìn)土體土壤滲透能力和蓄水保墑能力的提高。而深松更利于水分就地入滲,免耕更利于有機(jī)碳的提升和水分的儲(chǔ)存。但本研究為實(shí)行長(zhǎng)期定位試驗(yàn) 8年后的結(jié)果,而對(duì)于更長(zhǎng)年限的免耕、深松或持續(xù)免耕后進(jìn)行深松及持續(xù)深松后進(jìn)行免耕等對(duì)土壤剖面物理特性的影響差異及程度如何,有待下一步研究。

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Effect of tillage method on soil water infiltration,organic carbon content and structure*

YANG Yonghui1,2,WU Jicheng1,2,ZHANG Jiemei1,2,PAN Xiaoying1,2,WANG Yue1,2,HE Fang1,2
(1.Institute of Plant Nutrition & Resource Environment,Henan Academy of Agricultural Sciences,Zhengzhou 450002,China; 2.Yuanyang Experimental Station of Crop Water Use,Ministry of Agriculture,Yuanyang 453514,China)

Long-term tillage can greatly influence the physical properties of soil profile.For example,subsoiling and no-tillage can increase soil organic matter content,improve soil structure,increase the stability of soil structure and thereby improve soil moisture environment.In addition,no-tillage and subsoiling rotation can significantly improve soil water storage.Mostreported studies were on no-tillage with mulching or subsoiling with mulching or no-tillage and subsoiling rotation.And the investigated soil profiles were usually focused on the ploughed layer.However,the effect of long-term subsoiling or no-tillage without mulching on the physical properties,infiltration processes,organic carbon distribution and structure of soil,especially for the deep soil has been rarely reported.Thus the objective of the study was to explore the effects of long-term no-tillage,subsoiling and conventional tillage,all without mulching,on the structure and water infiltration processes of the soil profile.An undisturbed 0-100 cm soil column,and the ring-cut samples of undisturbed soil and mixed soil samples of the 0-10 cm,10-20 cm,···,90-100 cm layers were collected in a long-term field experiment to determine the soil infiltration processes,saturated hydraulic conductivity,soil organic carbon content and soil structure.The results showed that the time for water infiltrating from the surface to the bottom of soil column under conventional tillage was longest among all treatments.The orders of permeability rate and cumulative infiltration of soil column were as follow: subsoiling ＞ no-tillage ＞ tillage.Then time for cumulative evaporation of the soil column arranged from max to min was from conventional tillage to no-tillage and then to subsoiling.Also the order of saturated hydraulic conductivity in the 0-10 cm and 50-60 cm soil layers was no-tillage ＞subsoiling ＞ conventional tillage,and that in 20-50 cm and 60-100 cm soil layers was subsoiling ＞ no-tillage ＞ conventional tillage.With the increasing depth of soil,the content of ＞ 0.25 mm water-stable aggregates and soil organic carbon initially increased (10-20 cm layer) and then gradually decreased.In the 0-40 cm and 80-100 cm soil layer,the content of ＞ 0.25 mm water-stable aggregates under subsoiling was highest.The order of soil organic carbon content in the 0-60 cm soil layer was no-tillage ＞ subsoiling ＞ conventional tillage.While soil organic carbon below the 60 cm layer of all the treatments was lower than 4.0 g·kg-1,and followed the order of conventional tillage ＞ no-tillage ＞ subsoiling below the 70 cm soil layer.It was therefore concluded that reasonable tillage improved soil organic carbon content and soil structure,and then promoted soil water conservation.Subsoiling was more favorable to soil water infiltration and no-tillage more conducive for organic carbon and water storage,especially in the 0-60 cm soil layer.

Conventional tillage; Subsoiling; No-tillage; Soil water infiltration; Soil organic carbon; Soil structure

,YANG Yonghui,E-mail: yangyongh@mails.gucas.ac.cn

S152

: A

: 1671-3990(2017)02-0258-09

10.13930/j.cnki.cjea.160720

楊永輝,武繼承,張潔梅,潘曉瑩,王越,何方.耕作方式對(duì)土壤水分入滲、有機(jī)碳含量及土壤結(jié)構(gòu)的影響[J].中國(guó)生態(tài)農(nóng)業(yè)學(xué)報(bào),2017,25(2): 258-266

Yang Y H,Wu J C,Zhang J M,Pan X Y,Wang Y,He F.Effect of tillage method on soil water infiltration,organic carbon content and structure[J].Chinese Journal of Eco-Agriculture,2017,25(2): 258-266

* 國(guó)家自然科學(xué)基金項(xiàng)目(U1404404)、河南省農(nóng)業(yè)科學(xué)院優(yōu)秀青年科技基金(2016YQ12)和國(guó)家高技術(shù)研究發(fā)展計(jì)劃(863計(jì)劃)課題(2013AA102904)資助

楊永輝,主要研究方向?yàn)橥寥郎鷳B(tài)與節(jié)水農(nóng)業(yè)。E-mail: yangyongh@mails.gucas.ac.cn

2016-08-15 接受日期: 2016-10-14

* This study was supported by the National Natural Science Foundation of China (U1404404),the Excellent Youth Science and Technology Fund of Henan Academy of Agricultural Sciences (2016YQ12) and the National High-tech R&D Program of China (863 Program) (2013AA102904).

Received Aug.15,2016; accepted Oct.14,2016