劉曉冰,周克琴,苗淑杰,隋躍宇,張興義
(中國(guó)科學(xué)院東北地理與農(nóng)業(yè)生態(tài)研究所黑土區(qū)農(nóng)業(yè)生態(tài)重點(diǎn)實(shí)驗(yàn)室,黑龍江哈爾濱 150081)
土壤侵蝕是指土壤及其母質(zhì)在水力、風(fēng)力、凍融、重力等外營(yíng)力作用下,被破壞、剝蝕、搬運(yùn)和沉積的過(guò)程。對(duì)于農(nóng)業(yè)土壤而言,土壤侵蝕導(dǎo)致同一田塊土壤的重新分配、土壤結(jié)構(gòu)破壞、有機(jī)質(zhì)和養(yǎng)分含量減少,水分有效性降低,形成對(duì)干旱更敏感的條件,耕層變薄,肥力下降,限制已有作物的種植,增加化肥投入的成本,生產(chǎn)力降低[1-3]。而且,基于糧食生產(chǎn)和食品安全的原因,土壤侵蝕引起的肥力損失最終導(dǎo)致土地的廢棄,引起土地價(jià)值的實(shí)質(zhì)性降低[4-5]。從環(huán)境角度出發(fā),控制土壤侵蝕就是降低土壤有機(jī)碳向大氣中的釋放、減少N 的移動(dòng)和溶解態(tài)P 以及顆粒態(tài)P 的遷移,即控制土壤侵蝕具有固碳、恢復(fù)退化土壤及改善水質(zhì)的潛力。世界范圍內(nèi),土壤侵蝕每年都導(dǎo)致巨大經(jīng)濟(jì)損失。據(jù)報(bào)道美國(guó)每年損失3 000 億美元~4 400 億美元[6],我國(guó)東北農(nóng)民經(jīng)濟(jì)損失55 億人民幣[7]。因此,控制土壤侵蝕幾乎對(duì)世界任何一個(gè)國(guó)家都十分必要[8-9]。結(jié)合所在的科研團(tuán)隊(duì)近年來(lái)在黑土土壤侵蝕與作物生產(chǎn)力領(lǐng)域的研究工作,分析了國(guó)內(nèi)外土壤侵蝕研究的相關(guān)動(dòng)態(tài),強(qiáng)調(diào)適當(dāng)?shù)霓r(nóng)藝措施,尤其是有機(jī)肥的施用對(duì)增肥保水,恢復(fù)侵蝕土壤生產(chǎn)力的重要性。
土壤侵蝕引起不同土壤和生態(tài)區(qū)作物減產(chǎn)已被廣泛證實(shí)[10-13]。據(jù)觀測(cè),同一坡耕地小麥最高產(chǎn)量與最低產(chǎn)量差異高達(dá)5 倍以上[14],侵蝕坡地玉米和大豆的產(chǎn)量均顯著低于附近平地或坡地坡腳的產(chǎn)量[15-16]。普遍接受的結(jié)論是作物因土壤侵蝕減產(chǎn)10%以上,嚴(yán)重侵蝕地塊作物減產(chǎn)50%[17],表土層消失玉米減產(chǎn)高達(dá)90%以上[18-19]。
多數(shù)研究表明,表層土壤變薄是導(dǎo)致坡耕地作物產(chǎn)量降低的最主要也是最直接的原因[12,20-22]。肥沃的表層土壤對(duì)作物產(chǎn)量的形成至關(guān)重要,表層土壤的有機(jī)碳含量和厚度與作物產(chǎn)量呈正相關(guān)[11]。Monreal等[23]報(bào)道,每損失1 cm 土壤,淋溶土和黑土種植的小麥分別減產(chǎn)6.4%,黑土減產(chǎn)6.7%。Larney 等[18]在加拿大對(duì)5 塊旱地和1 塊水澆地分別進(jìn)行表土剝離0、5 cm、10 cm、15 cm、20 cm,模擬研究不同侵蝕程度對(duì)作物產(chǎn)量的影響,得出作物產(chǎn)量與表土層厚度有顯著相關(guān)性,表土剝離0~5 cm,作物減產(chǎn)20%~41%;表土剝離20 cm,作物減產(chǎn)高達(dá)63%~95%。綜合分析表明,每損失1 cm 老成土,小麥產(chǎn)量減少75 kg·hm-2,其他土壤都低于40 kg·hm-2;玉米產(chǎn)量老成土減少153 kg·hm-2,淋溶土減少92 kg·hm-2,而黑土減少40 kg·hm-2[12,24]。Larney 等[25]研究表明小麥產(chǎn)量5 cm 土壤剝離減產(chǎn)8%,10 cm 減產(chǎn)28%,15 cm 減產(chǎn)39%,20 cm 減產(chǎn)53%。
我們?cè)谝缓谕翆涌偤穸葹?0 cm 的坡耕地上的研究表明,5 cm 和10 cm 表土被剝離后,大豆的產(chǎn)量分別降低3.1%和3.2%,玉米產(chǎn)量只降低1.9%和4.7%;當(dāng)20 cm 表層黑土被剝離時(shí),大豆玉米產(chǎn)量分別降低34.2%和34.6%;而當(dāng)30 cm 耕層剝離即黑土層消失時(shí),大豆產(chǎn)量降低59.2%,而玉米產(chǎn)量降低高達(dá)95.4%[19,26-27],可見(jiàn)黑土層的存在對(duì)黑土農(nóng)田作物產(chǎn)量的維持至關(guān)重要。此外,土壤侵蝕對(duì)產(chǎn)量的影響年際間也有差異。干旱年份侵蝕土壤造成植物有效持水量或入滲速率低,產(chǎn)量明顯低于非侵蝕土壤,而在正常年份或降雨高于平均水平的年份產(chǎn)量基本相當(dāng)[10,28]。
土壤侵蝕對(duì)作物產(chǎn)量的不利影響可歸納為以下幾個(gè)方面:①表土層變薄,有機(jī)碳含量降低[27,29];②土壤氮磷儲(chǔ)量減少[8],有效水容量降低[11,30];③土壤水穩(wěn)性團(tuán)聚體減少,密度增加[20];④土壤黏粒含量改變[29,31],土壤的NO-3-N、有效磷、Zn、Fe、Mn、CEC 降低[5]。盡管不同區(qū)域土壤侵蝕對(duì)作物產(chǎn)量的影響不同,但影響程度與侵蝕強(qiáng)度顯著相關(guān)[17],其影響總體可歸納為水肥兩個(gè)方面,一是因地形以及地表覆蓋的改變導(dǎo)致降水在地表空間上分配失調(diào),致使坡面作物生長(zhǎng)發(fā)生水分脅迫;二是由于地表徑流導(dǎo)致表層土壤及其部分養(yǎng)分流失,土壤質(zhì)量下降[16,22]。坡耕地土壤含水量坡腳最高,坡降最大的坡肩位置最低,水分脅迫是造成作物局部減產(chǎn)的主要原因[14,19]。然而,同等坡位條件下,水分脅迫顯然不是引起產(chǎn)量降低的直接原因。即坡耕地侵蝕影響作物的產(chǎn)量涉及到坡度、坡長(zhǎng)、土壤性狀、表土層厚度等諸因子[32-33]。隨著表土不斷被剝離,勢(shì)必導(dǎo)致土壤有機(jī)質(zhì)含量的降低[27]。顯然,耕層變薄是土壤侵蝕影響產(chǎn)量的表面現(xiàn)象,而實(shí)質(zhì)是侵蝕引起土壤物理化學(xué)生物因素,尤其是土壤養(yǎng)分、pH 和微生物活性等改變,限制了作物根際效應(yīng),導(dǎo)致根系生長(zhǎng)發(fā)育不良而引起的。
土壤侵蝕嚴(yán)重影響根系分泌物和微生物的種類和活性。根系分泌物和微生物活性影響著土壤養(yǎng)分循環(huán)、根系生長(zhǎng)并促進(jìn)植物發(fā)育[34-36]。根際效應(yīng)在根際沉積物最多的完整根部表現(xiàn)最明顯。然而,死根是地下微生物基本的能量來(lái)源,同時(shí)死根提供了另外一個(gè)焦點(diǎn)即所謂的次生根際效應(yīng)。研究者們發(fā)現(xiàn),豆科植物分泌物的黃酮類物質(zhì)能夠誘導(dǎo)根瘤菌結(jié)瘤基因的表達(dá),促進(jìn)結(jié)瘤[37]。禾本科作物的根分泌物有較多的含碳有機(jī)化合物,如糖類和有機(jī)酸等,而有些植物根系的分泌物還具有嚴(yán)格的專一性,如燕麥根能分泌7-羥基-6-甲氧基香豆素,蘋果根能分泌根皮苷,苜蓿根能分泌皂角苷,玉米的根分泌物卻為含氮和不含氮的有機(jī)化合物。這些物質(zhì)釋放到土壤中,可以起到養(yǎng)分活化、促進(jìn)有益微生物繁殖、提高土壤生物化學(xué)活性和土壤有機(jī)質(zhì)含量的作用[13,38]。
研究表明不同作物對(duì)土壤磷素利用效率的明顯差異與低磷脅迫誘導(dǎo)作物根系分泌物、根形態(tài)、根構(gòu)型等變化有關(guān)[39-40]。白羽扇豆在低磷條件下,形成排根,并在排根處分泌大量的有機(jī)酸,通過(guò)有機(jī)酸的絡(luò)合溶解、酸溶解等途徑活化土壤中的難溶性磷[41]。大豆磷營(yíng)養(yǎng)脅迫時(shí),促進(jìn)根系分泌有機(jī)酸,但是總量并不高[42]。苗淑杰[43]比較水培條件下固氮和供給硝態(tài)氮大豆根系分泌有機(jī)酸時(shí),發(fā)現(xiàn)固氮大豆根系分泌的有機(jī)酸總量較高,尤其以丙二酸的含量最大。
根系分泌物對(duì)土壤微生物的影響既有促進(jìn)作用,也有抑制作用[44-45]。小麥根分泌物及其提取液刺激球形節(jié)桿菌的繁殖,水稻根分泌的有機(jī)酸和氨基酸可能成為糞產(chǎn)堿菌良好的碳源和氮源,有利于糞產(chǎn)堿菌的生長(zhǎng),支持其在根際的繁殖,大麥的根系分泌物有利于細(xì)菌的富集,棉花根系分泌物能促進(jìn)苜蓿根瘤菌發(fā)育,而玉米、亞麻的分泌物阻礙根瘤菌的發(fā)育[46-48]。
Germida 和Siciliano[49]證實(shí)不同植物根際土壤微生物群落結(jié)構(gòu)存在較大的差異,同一植物不同的發(fā)育階段或不同根區(qū)根際土壤微生物群落結(jié)構(gòu)也存在較大的差異。Seldin 等[50]指出在幼根和未成熟的根系上,r-型菌(快生型)為優(yōu)勢(shì)種群,而在成熟的根系上,k-型菌(慢生型)為優(yōu)勢(shì)種群。Duineveld 等[51]也觀察到幼齡菊花植株根際土壤的細(xì)菌群落不同于其它生長(zhǎng)階段,根尖樣品與幼齡植株之間的微生物群落結(jié)構(gòu)有著高度相似的DGGE 圖譜,而與成熟根際土壤微生物群落結(jié)構(gòu)差異較大。Marschner 等[52]研究表明白羽扇豆排根與非排根之間、新形成的排根與成熟的排根之間根際微生物群落結(jié)構(gòu)存在差異性,在白羽扇豆生長(zhǎng)35 d 和51 d 比21 d 體現(xiàn)的更顯著,主要與不同區(qū)域根系產(chǎn)生的分泌物有關(guān),成熟的排根分泌檸檬酸,新形成的排根分泌蘋果酸,而老化的排根具有高的磷酸酶活性。Marschner 等[53]進(jìn)一步指出,微生物的生長(zhǎng)及其代謝加快固定化的無(wú)機(jī)P、K 礦物質(zhì)及有機(jī)P、K 的分解和釋放,促進(jìn)植物營(yíng)養(yǎng)元素的有效化和對(duì)植物的可供性。
根際分泌物強(qiáng)烈的影響根際有機(jī)碳的轉(zhuǎn)化[54],表現(xiàn)為能夠顯著激發(fā)或抑制土壤有機(jī)碳的礦化。根際分泌物對(duì)土壤有機(jī)碳分解的這種促進(jìn)或抑制作用,稱為激發(fā)效應(yīng)。研究表明,植物光合作用能夠顯著影響根際分泌物的釋放,從而影響土壤有機(jī)質(zhì)分解的激發(fā)強(qiáng)度[55-56]。當(dāng)光合作用增強(qiáng)時(shí),根際分泌物增多,激發(fā)作用增強(qiáng),反之則隨之減弱。根際分泌物產(chǎn)生正激發(fā)效應(yīng)的機(jī)制在于分泌物釋放進(jìn)入土壤后,根際微生物迅速利用這些低糖類物質(zhì),微生物活性大大增強(qiáng),從而加快土壤有機(jī)碳的分解;此外,根系生長(zhǎng)能夠破碎土壤團(tuán)聚體,也加快了土壤有機(jī)碳的礦化[57]。根際微系統(tǒng)中,土壤有機(jī)質(zhì)分解的激發(fā)效應(yīng)不僅僅是土壤微生物的單一過(guò)程,而是土壤微生物-土壤動(dòng)物-植物根系共同作用的相互過(guò)程,這些過(guò)程的相互關(guān)聯(lián)決定了根際微系統(tǒng)的復(fù)雜性。
恢復(fù)侵蝕土壤的生產(chǎn)力,有兩種選擇。最普通的選擇就是額外增加化學(xué)肥料降低由侵蝕而引起的養(yǎng)分損失。有機(jī)肥施用是恢復(fù)生產(chǎn)力的另一種選擇[58]。早在1948 年,Hays 等就指出養(yǎng)分虧缺是侵蝕土壤生產(chǎn)力降低的主要原因,在蒙大拿州單施N 肥不足以恢復(fù)侵蝕土壤的生產(chǎn)力[59]。Mbagwu 等[60]研究發(fā)現(xiàn)土壤剝離后,亞耕層土壤中的N、P、K 和Mg 含量有限,限制玉米養(yǎng)分的吸收。Izaurralde 等[24]研究了表層土壤剝離后,化肥施用對(duì)小麥產(chǎn)量的影響,結(jié)果表明,N、P 化肥的施用對(duì)侵蝕地塊的小麥,不僅表現(xiàn)出產(chǎn)量的增加,同時(shí)也表現(xiàn)為N、P 養(yǎng)分吸收含量的增加,然而,增加的產(chǎn)量并未達(dá)到非侵蝕土壤相同化肥施用量的產(chǎn)量。但是,土壤剝離和化肥施用均不影響印度尼西亞花生地上部的K 營(yíng)養(yǎng)水平。
研究表明,在正常化肥施用量基礎(chǔ)上,增施15 t·hm-2腐熟的牛糞,能夠彌補(bǔ)5 cm (大豆)和10 cm(玉米)耕層土壤流失的產(chǎn)量損失[13,19,26]。增施牛糞顯著增加玉米、大豆地上部干物質(zhì)積累,促進(jìn)作物的根系生長(zhǎng),耕層水穩(wěn)性團(tuán)聚體(>0.25 mm)及其團(tuán)聚體結(jié)合的有機(jī)碳含量明顯增加,并發(fā)現(xiàn)水穩(wěn)性大團(tuán)聚體(>1 mm)的多少與有機(jī)碳含量呈正相關(guān),三葉期玉米根系表面積和地上部NPK 養(yǎng)分積累顯著增加,尤其是K 素含量[61-62]。而且驚奇地發(fā)現(xiàn),嚴(yán)重侵蝕土壤 (30 cm 耕層剝離)在連續(xù)施用牛糞15 t·hm-27 a 之后,其大豆的生產(chǎn)力與未侵蝕僅施用化肥的產(chǎn)量相當(dāng)。有機(jī)肥30 t·hm-2配合150 kg·hm-2N 和150 kg·hm-2P 具有較好的恢復(fù)效果,而且在干旱年份,有機(jī)肥的施用產(chǎn)量更高。其他研究同樣發(fā)現(xiàn)大量的化肥施用并不能使得產(chǎn)量恢復(fù)到非侵蝕土壤的水平[63-64]。這表明單純?cè)黾羽B(yǎng)分不足以恢復(fù)侵蝕土壤的生產(chǎn)力。Malhi 等[65]將厚度為34 cm 的表土層分別移出0、18%、35%、53%,建立田間裂區(qū)試驗(yàn),并加設(shè)施N 和P 肥小區(qū),得出作物產(chǎn)量隨土壤流失深度的增加而降低,施N 和P 肥可增加侵蝕區(qū)作物產(chǎn)量,但達(dá)不到未侵蝕區(qū)產(chǎn)量水平。有機(jī)肥或廄肥在侵蝕土壤上的應(yīng)用只是近20 年的事情[66-67]。與家禽糞便相比,作物殘茬、單施豌豆和苜蓿干草或NP 化肥與大麥秸稈混施,增加水穩(wěn)性團(tuán)聚體穩(wěn)定性,而家禽糞便處理比單施化肥也提高了土壤水穩(wěn)性團(tuán)聚體的穩(wěn)定性。Larney 和Janzen[68]研究了表層15 cm 土壤剝離后,家禽糞便、作物殘茬、秸稈與化肥結(jié)合、單施化肥對(duì)小麥產(chǎn)量的恢復(fù),結(jié)果表明,豬糞、雞糞和苜蓿干草恢復(fù)效果最好。3 年的產(chǎn)量結(jié)果均與對(duì)照產(chǎn)量沒(méi)有差異。他們的研究結(jié)果提出,土壤剖面0~60 cm硝態(tài)氮的濃度可以解釋施肥處理恢復(fù)能力的71%,而0~15 cm 土層提取的P 濃度可以解釋16%,剩余的13%可能與土壤結(jié)構(gòu)的改善有關(guān)。證明有機(jī)肥和作物殘?bào)w能夠替代損失的表層土壤,恢復(fù)侵蝕土壤的生產(chǎn)力。
Larney 等[25,69]進(jìn)一步研究表明,在表層剝離10 cm 后,有機(jī)肥施用增產(chǎn)73%,化肥增產(chǎn)28%;表層20 cm 土壤剝離后,有機(jī)肥施用可以增加產(chǎn)量158%,而化肥僅增加40%。然而,他們同時(shí)發(fā)現(xiàn),對(duì)未侵蝕土壤而言,化肥的增產(chǎn)作用效果高于有機(jī)肥。研究也注意到,有機(jī)肥恢復(fù)產(chǎn)量的作用,隨著侵蝕深度的增加效果越加明顯,對(duì)于非侵蝕土壤,在化肥基礎(chǔ)上增施有機(jī)肥大豆產(chǎn)量提高8.5%,玉米提高15%;而在30 cm 土層剝離后,增施有機(jī)肥增加大豆產(chǎn)量77%,增加玉米產(chǎn)量145%[27]。對(duì)亞耕層增施有機(jī)肥提高了玉米PK 的吸收,并明顯減少M(fèi)n 從表層土壤的淋溶[70]。Robbins 等[71]發(fā)現(xiàn)增施牛糞44 t·hm-2配合鋅肥施用能夠增加30 cm 剝離菜豆產(chǎn)量,與未剝離土壤產(chǎn)量相當(dāng)。以上研究說(shuō)明有機(jī)肥對(duì)侵蝕土壤的改良作用更為明顯,其明顯的增產(chǎn)效果可能與補(bǔ)償表層剝離后養(yǎng)分缺失密切相關(guān),也就是有機(jī)肥施用到侵蝕黑土后,向耕層中釋放養(yǎng)分的能力增強(qiáng)了。鑒于有機(jī)肥養(yǎng)分的釋放轉(zhuǎn)化更多地受到土壤的生物化學(xué)活性和根際環(huán)境變化的影響,明確有機(jī)肥施用改善根際土壤環(huán)境,恢復(fù)土壤微生物原有的代謝活性、增強(qiáng)根系分泌物和關(guān)鍵土壤酶活性、提高土壤養(yǎng)分有效性、促進(jìn)養(yǎng)分吸收轉(zhuǎn)化對(duì)恢復(fù)侵蝕黑土生產(chǎn)力的關(guān)鍵生物學(xué)效應(yīng),將為侵蝕黑土農(nóng)田生產(chǎn)力的恢復(fù)提供系統(tǒng)科學(xué)數(shù)據(jù)和理論支撐。
[1]Cihacek L J,Swan H B. Effects of erosion on soil chemical properties in the north central region of the United States [J]. Journal of Soil and Water Conservation,1994,49 (3):259-265.
[2]Robins C W,Mackay B E,F(xiàn)reeborn L L. Improving exposed subsoils with fertilizers and crop rotations [J]. Soil Science Society of America Journal,1997,61 (4):1221-1225.
[3]Fenton T E.The impact of erosion on the classification and productivity of Mollisols in Iowa [M].In:Liu X B,Song C Y,Richard R M,et al.New advances in research and management of World Mollisols. Northeast Forestry University Press,Harbin,2010:68-70.
[4]Morgan R P C. Soil Erosion and Conservation [M]. USA:Blackwell Science Ltd,2005.
[5]Izaurralde R C,Malhi S S,Nyborg M,et al. Crop performance and soil properties in two artificially eroded soils in North-Central Alberta [J].Agronomy Journal,2006,98 (5):1298-1311.
[6]Uri N D,Lewis J A. The dynamics of soil erosion in US agriculture [J]. Science of the Total Environment,1998,218 (1):45-58.
[7]劉興土,閻百興. 東北黑土區(qū)水土流失與糧食安全[J]. 中國(guó)水土保持,2009,1:17-19.
[8]Bakker M M,Govers G,Rounsevell M D A. The crop productivity-erosion relationship:an analysis based on experimental work [J]. Catena,2004,57 (1):55-76.
[9]劉寶元,閻百興,沈 波,等. 東北黑土區(qū)農(nóng)地水土流失現(xiàn)狀與綜合治理對(duì)策[J]. 中國(guó)水土保持科學(xué),2008,6 (1):1-8.
[10]Shaffer M J,Schumacher T E,Ego C L. Simulating the effects of erosion on corn productivity [J]. Soil Science Society of America Journal,1995,59 (3):672-679.
[11]Lal R. Soil erosion impact on agronomic productivity and environmental quality [J]. Critical Reviews in Plant Sciences,1998,17 (4):319-464.
[12]Den Biggelaar C,Lal R,Wiebe K,et al. Impact of soil erosion on crop yields in North America [J]. Advances in Agronomy,2001,72,1-52.
[13]Liu X B,Zhang X Y,Wang Y,et al. Soil degradation:A problem threatening the sustainable development of agriculture in Northeast China[J]. Plant Soil and Environment,2010,56 (2):87-97.
[14]Reyniers M,Maertens K,Vrindts E. Yield variability related to landscape properties of a loamy soil in central Belgium [J]. Soil and Tillage Research,2006,88 (1-2):262-273.
[15]Khakural B R,Robert P C,Huggins D R. Variability of corn/soybean yield and soil/landscape properties across a southwestern Minnesota landscape [M]. In:Robert P C (ed. ). Proceedings of the Fourth International Conference on Precision Agriculture. American Society of Agronomy,Minneapolis,MN. ASA,CSSA,SSA,Madison,WI,1999:573-579.
[16]Marquesda Silva J R,Silva L L. Evaluation of the relationship between maize yield spatial and temporal variability and different topographic attributes [J]. Biosystems engineering,2008,101 (2):183-190.
[17]La Rosa D,Moreno J A,Mayol F,et al. Assessment of soil erosion vulnerability in western Europe and potential impact on crop productivity due to loss of soil depth using the ImpelERO model [J]. Agriculture,Ecosystems and Environment,2000,81 (3):179-190.
[18]Larney F J,Izaurralde R C,Jansen H H ,et al. Soil erosion-crop productivity relationships for six Alberta soils [J]. Journal of Soil and Water Conservation,1995,50 (1):87-91.
[19]張興義,孟令欽,劉曉冰,等. 黑土區(qū)水土流失對(duì)玉米干物質(zhì)積累及產(chǎn)量的影響[J]. 中國(guó)水利,2007,22:47-49.
[20]Gollany H T,Schumacher T E,Evenson P D,et al. Topsoil depth and desurfacing effects on properties and productivity of a Typic Argiustoll[J]. Soil Science Society of America Journal,1992,56 (1):220-225.
[21]Lal R. Erosion-crop productivity relationships for soils of Africa [J]. Soil Science Society of America Journal,1995,59 (3):661-667.
[22]Rose C W,Dalal R C. Erosion and runoff of nitrogen:Proceedings of the Symposium on Advances in Nitrogen Cycling in Agricultural Ecosystems. Brisbane,Australia,11-15,May 1987. CAB International,Wallingford:1988,212-235.
[23]Monreal C M,Zentner R P,Robertson J A. The influence of management on soil loss and yield of wheat in chernozemic and luvisolic soils [J].Canadian Journal of Soil Science,1995,75:567-574.
[24]Izaurralde R C,Solberg E D,Nyborg M,et al. Immediate effects of topsoil removal on crop productivity loss and its restoration with commercial fertilizers [J]. Soil and Tillage Research,1998,46 (3-4):251-259.
[25]Larney F J,Olson B M,Janzen H H,et al. Early impact of topsoil removal and soil amendments on crop productivity [J]. Agronomy Journal,2000,92 (5):948-956.
[26]張興義,劉曉冰,隋躍宇,等. 人為剝離黑土層對(duì)大豆生育和產(chǎn)量的影響[J]. 大豆科學(xué),2006,25 (2):123-126.
[27]Sui Y Y,Liu X B,Jin J,et al. Zhang. Differentiating the early impact of topsoil removal and soil amendments on crop performance/productivity of corn and soybean in eroded farmland of Chinese Mollisols [J]. Field Crops Research,2009,111 (3):276-283.
[28]Swan J B,Shaffer M J,Paulson W H,et al. Simulating the effects of soil depth and climatic factors on corn yield [J]. Soil Science Society of America Journal,1987,51 (4):1025-1032.
[29]Kreznor W R,Olson K R,Banwart W L,et al. Soil,landscape,and erosion relationships in a Northwest Illinois watershed [J]. Soil Science Society of America Journal,1989,53 (6):1763-1771.
[30]Jones A J,Lal R,Huggins D R. Soil erosion and productivity research:a regional approach [J]. American Journal of Alternative Agriculture,1997,12 (4):185-192.
[31]Tengberg A,Stocking M A,Da Virga M. The impact of erosion on the productivity of a Ferralsol and a Cambisol in Santa Catanina,southern Brazil [J]. Soil Use and Management,1997,13 (2):90-96.
[32]Cotching W E,Hawkins K,Sparrow L A,et al. Crop yields and soil properties on eroded slopes of red ferrosols in northwest Tasmania [J].Australian Journal of Soil Research,2002,40 (4):625-642.
[33]孟 凱,張興義,隋躍宇,等. 黑土農(nóng)田水肥條件對(duì)作物產(chǎn)量及水分利用效率的影響[J]. 中國(guó)生態(tài)農(nóng)業(yè)學(xué)報(bào),2005,13 (2):119-121.
[34]張福鎖,李曉林,王敬國(guó),等. 環(huán)境脅迫與植物根際營(yíng)養(yǎng)[M]. 北京:中國(guó)農(nóng)業(yè)出版社,1998.
[35]Sylvia D M,Chellemi D O. Interactions among root-inhabiting fungi and their implications for biological control of root pathogens [J]. Advance in Agronomy,2001,73:1-33.
[36]吳金水,林啟美,黃巧云,等. 土壤微生物生物量測(cè)定方法及其應(yīng)用[M]. 北京:氣象出版社,2006.
[37]Redmond J W,Batley M,Djordjevic M A,et al. Flavones induce expression of nodulation genes in Rhizobium [J]. Nature,1986,323:632-635.
[38]王振宇,呂金印,李鳳明,等. 根際沉積及其在植物-土壤碳循環(huán)中的作用[J]. 應(yīng)用生態(tài)學(xué)報(bào),2006,17 (10):1963-1968.
[39]王美麗,嚴(yán)小龍. 大豆根形態(tài)和根系分泌物特征與磷效率[J]. 華南農(nóng)業(yè)大學(xué)學(xué)報(bào),2001,22 (3):1-4.
[40]廖 紅,戈振揚(yáng),嚴(yán)小龍. 水磷耦合脅迫下植物磷吸收的理想根構(gòu)型:模擬與應(yīng)用適應(yīng)[J]. 科學(xué)通報(bào),2001,46 (8):641-647.
[41]Hoffland E,F(xiàn)inderegg G R,Nelmans J A. Solubilization of rock phosphate by rape. I. Evaluation of the role of the nutrient uptake pattern [J].Plant and Soil,1989,113 (2):155-160.
[42]Tang C,Han X Z,Qiao Y F,et al.Phosphorus deficiency does not enhance proton release by roots of soybean [Glycine max (L.)Merr.][J].Environmental and Experimental Botany,2009,67 (1):228-234.
[43]苗淑杰. 缺磷脅迫對(duì)大豆結(jié)瘤固氮和根系分泌物的影響[D]. 哈爾濱:中國(guó)科學(xué)院東北地理與農(nóng)業(yè)生態(tài)研究所,2007.
[44]陸雅海,張福鎖. 根際微生物研究進(jìn)展[J]. 土壤.2006,38 (2):113-121.
[45]Huerta E,Vidal O,Jarquin A,et al. Effect of Vermicompost on the growth and production of Amashito pepper,interactions with earthworms and rhizobacteria [J]. Compost Science and Utilization,2010,18 (4):282-288.
[46]Liljeroth E,Van Veen J A,Miller H J. Assimilate translocation to the rhizosphere of two wheat lines and subsequent utilization by rhizosphere microorganisms at two soil nitrogen concentrations [J]. Soil Biology and Biochemistry,1990,22 (8):1015-1021.
[47]林 敏,尤崇杓. 水稻根分泌物及其與類產(chǎn)堿菌的相互作用[J]. 中國(guó)農(nóng)業(yè)科學(xué),1989,22 (6):6-12.
[48]朱麗霞,章家恩,劉文高. 根系分泌物與根際微生物相互作用研究綜述[J]. 生態(tài)環(huán)境,2003,12 (1):102-105.
[49]Germida J J,Siciliano S D,F(xiàn)reitas J R,et al. Diversity of root-associated bacteria associated with field-grown canola (Brassica napus L. )and wheat (Triticum aestivum L.)[J]. FEMS Microbioogy Ecology,1998,26 (1):43-50.
[50]Seldin L,Rosado A S,Da Cruz D W,et al. ,Comparison of Paenibacillus azotofixans strains isolated from rhizoplane,rhizosphere,and non-root-associated soil from maize planted in two different Brazilian soils [J]. Applied and Environment Microbiology,1998,64 (10):3860-3868.
[51]Duineveld B M,Kowalchuk G A,Keijzer A. Analysis of bacterial communities in the rhizosphere of chrysanthemum via denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA as well as DNA fragments coding for 16S Rrna [J]. Applied and Environment Microbiology,2001,67 (1):172-178.
[52]Marschner P. ,Neumann G. ,Kania A. ,et al. Spatial and temporal dynamics of the microbial community structure in the rhizosphere of cluster roots of white lupin (Lupinus albus L.)[J]. Plant and Soil,2002,246 (2):167-174.
[53]Marschner P,Crowley D E,Yang C H. Development of specific rhizosphere bacterial communities in relation to plant species,nutrition and soil type [J]. Plant and Soil,2004,261 (1-2):199-208.
[54]王智平,陳全勝. 植物近期光合碳分配及轉(zhuǎn)化[J]. 植物生態(tài)學(xué)報(bào),2005,29 (5):845-850.
[55]Kuzyakova Y,Cheng W. Photosynthesis controls of soil CO2efflux from maize rhizosphere [J]. Plant and Soil,2004,263 (1):85-99.
[56]Trumbore S. Carbon respired by terrestrial ecosystems:Recent progress and challenges [J]. Global Change Biology,2006,12 (2):141-153.
[57]Cheng W X,Coleman D C.The effect of living roots on soil organic matter decomposition [J].Soil Biology and Biochemistry,1990,22 (6):781-787.
[58]Dormaar J F,Lindwall C W,Kozub G C. Effectiveness of manure and commercial fertilizer in restoring productivity of an artificially eroded Dark Brown Chernozemic soil under dryland conditions [J]. Canadian Journal of Soil Science,1988,68:669-679.
[59]Reuss J O,Campbell R E. Restoring productivity to leveled land [J]. Soil Science Society of America Journal,1961,25 (4):302-304.
[60]Mbagwu J S C. Subsoil productivity of an Ultisol in Nigeria as affected by organic wastes and inorganic fertilizer amendments [J]. Soil Science,1985,140 (6):436-441.
[61]Zhou K Q,Liu X B,Zhang X Y,et al. Corn root growth and nutrient accumulation improved by five years of repeated cattle manure addition to eroded Chinese Mollisols [J]. Canadian Journal of Soil Science,2012,92 (3):521-527.
[62]Sui Y Y,Jiao X G,Liu X B,et al. Water-stable aggregates and their organic carbon distribution after five years of chemical fertilizer and manure treatments on eroded farmland of Chinese Mollisols [J]. Canadian Journal of Soil Science,2012,92 (3):551-557.
[63]Olsen S R. The role of organic matter and ammonium in producing high corn yields [J]. In Chen Y and Avnimelech Y (eds. ),The Role of Organic Matter in Modern Agriculture. Martinus Nijhoff. Dordrecht,1986.
[64]Massee T W. Simulated erosion and fertilizer effects on winter wheat cropping intermountain dryland area [J]. Soil Science Society of America Journal,1990,54 (6):1720-1725.
[65]Malhi S S,Izauralde R C,Nyborg M,et al. Influence of topsoil removal on soil fertility and barley growth [J]. Journal of Soil and Water Conservation,1994,49 (1):96-101.
[66]Eghball B,Power J F. Composted and non-composted beef feedlot manure effects on corn production and soil properties under conventional and no-till systems.1995,P.557-563. In C. C. Ross (ed. )Proc. Int. Symp. Agric. and Food Processing Wastes,7th,Chicago,IL.18-20 June 1995. ASAE,St. Joseph,MI
[67]Schlegel A J. Effect of composted manure on soil chemical properties and nitrogen use by grain sorghum [J]. Journal of Production Agriculture,1992,5 (1):153-157.
[68]Larney F J,Janzen H J. Restoration of productivity to a desurfaced soil with livestock manure,crop residue,and fertilizer amendments [J].Agronomy Journal,1996,88 (6):921-927.
[69]Larney F J,Akinremi O O,Lemke R L ,et al. Crop response to topsoil replacement depth and organic amendment on abandoned natural gas wellsites [J]. Canadian Journal of Soil Science,2003,83:415-423.
[70]Sharma B M,Yadav J S P. Leaching Losses of Iron and Manganese During Reclamation of Alkali [J]. Soil Science,1986,142 (3):149-152.
[71]Robbins C W,Mackey B E,F(xiàn)reeborn L L. Improving Exposed Subsoils with Fertilizers and Crop Rotations [J]. Soil Science Society of America Journal,1997,61 (4):1221-1225.