基于磷肥施用深度的夏玉米根層調(diào)控提高土壤氮素吸收利用

陳曉影 劉 鵬 程 乙 董樹亭 張吉旺 趙 斌 任佰朝 韓 坤

基于磷肥施用深度的夏玉米根層調(diào)控提高土壤氮素吸收利用

陳曉影 劉 鵬*程 乙 董樹亭 張吉旺 趙 斌 任佰朝 韓 坤

作物生物學(xué)國家重點(diǎn)實(shí)驗(yàn)室 / 山東農(nóng)業(yè)大學(xué)農(nóng)學(xué)院, 山東泰安 271018

良好的根系構(gòu)型能夠促進(jìn)作物高效獲取土壤養(yǎng)分。基于磷肥施用深度的根層調(diào)控技術(shù)可以優(yōu)化夏玉米根系的時空分布并促進(jìn)其與土壤水分、養(yǎng)分供應(yīng)的空間匹配性, 為通過玉米根系挖潛實(shí)現(xiàn)節(jié)肥增效提供理論與技術(shù)支撐。本試驗(yàn)以不施磷肥處理為對照(CK), 設(shè)置距離地表?5 cm (P5)、?10 cm (P10)、?15 cm (P15)和?20 cm (P20)深度施用磷肥處理, 分析各處理對夏玉米根系分布、植株生長及產(chǎn)量形成、氮素吸收、積累與轉(zhuǎn)運(yùn)的影響。結(jié)果表明, 磷肥適當(dāng)深施顯著促進(jìn)夏玉米根系生長, 根干重、根長密度、根系表面積和根體積均顯著增加, 整體表現(xiàn)為P15>P10>P20>P5>CK。隨著磷肥施用深度的增加, 深層玉米根系顯著增加。P15和P20處理根干重所占比重, 在20~40 cm土層分別為12.3%和12.1%; 在40~60 cm土層分別為6.7%和6.9%。根系分布深度的增加促進(jìn)了對土壤氮素的吸收, 深施磷肥處理各土層中尤其是20 cm以下土層土壤氮素含量顯著降低。根系分布的優(yōu)化同時促進(jìn)了植株氮素積累與轉(zhuǎn)運(yùn), P15處理較P5處理氮素吸收效率、氮積累量、轉(zhuǎn)運(yùn)量及氮肥偏生產(chǎn)力2年平均分別提高14.5 kg kg–1、19.2%、48.9%和6.4 kg kg–1, 籽粒產(chǎn)量2年平均增產(chǎn)16.4%。在本試驗(yàn)條件下, 磷肥集中施用在?15 cm處理, 能顯著促進(jìn)夏玉米深層土壤根系的生長, 擴(kuò)大根系養(yǎng)分利用空間, 增加根系對深層土壤氮素的吸收, 促進(jìn)植株氮素積累及轉(zhuǎn)運(yùn), 提高其生產(chǎn)力, 最終提高產(chǎn)量。

夏玉米; 施磷深度; 根系; 產(chǎn)量; 氮素吸收利用

作物生產(chǎn)既要滿足全球不斷增長的人口對糧食生產(chǎn)日益增長的需求, 還要盡量高效利用資源、避免環(huán)境污染。優(yōu)化肥料施用方式是實(shí)現(xiàn)作物高產(chǎn)高效的有效途徑之一[1-2]。肥料用量及施用方式對根系具有較強(qiáng)的調(diào)控作用[3-4]。根層調(diào)控技術(shù)是挖掘根系生物學(xué)潛力、提高肥料的利用效率的有效途徑[5-6]。根系對作物水分、養(yǎng)分獲取有重要作用, 在發(fā)育過程中具有高度的可塑性[7-9]。良好的根系構(gòu)型能夠促進(jìn)作物高效獲取土壤養(yǎng)分。磷在土壤中的擴(kuò)散能力較差, 其擴(kuò)散系數(shù)僅為10–12~10–15m2s–1[10], 土壤有效磷主要分布在土壤表層[11], 因此作物高效獲取土壤“磷”資源的理想根系構(gòu)型為“表層覓食型”[12-13]。而土壤中的硝態(tài)氮在作物生長季節(jié)隨降水淋洗或水位下降而移動到深土層, 氮高效的理想根系構(gòu)型為“Steep, cheap, deep型”[14-15], 該理想根構(gòu)型通過增加深層土壤中的根系、提高硝態(tài)氮的吸收, 從而降低氮的淋洗并提高氮利用效率[16-17]。

土壤中氮、磷空間分布的異質(zhì)性, 使高效利用二者的根系構(gòu)型存在一定的矛盾, 如何協(xié)調(diào)這種矛盾, 實(shí)現(xiàn)土壤氮磷養(yǎng)分協(xié)調(diào)吸收成為促進(jìn)作物增產(chǎn)增效的重要問題[18]。磷肥用量及施用方式對根系分布有重要調(diào)控作用, 可以促進(jìn)合理根系構(gòu)型的建成, 改變土壤中根系的時空分布[19-21], 可將根際養(yǎng)分供應(yīng)強(qiáng)度與根系生長分布的平衡調(diào)整到最佳狀態(tài), 在時間和空間上充分發(fā)揮根系生物學(xué)潛力, 提高肥料的利用效率[22-23]。前人已就肥料施用方式對作物生產(chǎn)能力、養(yǎng)分利用效率和損失進(jìn)行了廣泛研究[24-26]。但基于磷肥施用深度的夏玉米根層調(diào)控對挖掘作物根系生物學(xué)潛力, 提高深層土壤氮素利用效率的機(jī)理研究相對較少。該研究對夏玉米根系時空分布及其與氮素供應(yīng)空間匹配性的優(yōu)化效應(yīng), 為建立有效的作物高產(chǎn)根系調(diào)控技術(shù)、實(shí)現(xiàn)以根系挖潛節(jié)肥增效為核心的玉米高產(chǎn)高效栽培提供理論與技術(shù)支撐。

1 材料與方法

1.1 試驗(yàn)時間地點(diǎn)

2017—2018年在泰安市岱岳區(qū)馬莊鎮(zhèn)(35°58′N, 116°58′E)進(jìn)行試驗(yàn), 試驗(yàn)點(diǎn)地處溫帶大陸性季風(fēng)氣候區(qū), 作物種植體系為冬小麥/夏玉米一年兩熟。試驗(yàn)田為壤土, 試驗(yàn)前0~20 cm、20~40 cm、40~60 cm土壤樣品理化性質(zhì)見表1。試驗(yàn)田夏玉米全生育期平均溫度與日降水量見圖1。

表1 試驗(yàn)田養(yǎng)分含量

圖1 試驗(yàn)田夏玉米生育期平均溫度與降水量

1.2 試驗(yàn)設(shè)計

供試夏玉米品種為登海605 (DH605)。試驗(yàn)以不施磷肥處理為對照(CK), 磷肥用量為P2O5105 kg hm–2, 共設(shè)置4個施肥深度, 分別為距離地表?5 cm (P5)、?10 cm (P10)、?15 cm (P15)和?20 cm (P20)深度處施肥。于小麥?zhǔn)斋@后表層撒施純氮315 kg hm–2和K2O 270 kg hm–2, 然后結(jié)合小麥滅茬旋耕5 cm。利用經(jīng)改造后的深松條帶式施肥機(jī)深松20 cm, 同時將磷肥施用在設(shè)計深度。試驗(yàn)采用隨機(jī)區(qū)組設(shè)計, 3次重復(fù), 種植密度為67,500株 hm–2, 行距60 cm, 株距25 cm。小區(qū)面積180 m2(長30 m、寬6 m)。試驗(yàn)所用肥料為緩控尿素(含純N 42%)、過磷酸鈣(含P2O511%)、硫酸鉀(含K2O 50%), 均一次性施入。玉米生育期給予良好的管理并保證水分供應(yīng)。

1.3 測定項(xiàng)目與方法

1.3.1 植株干物質(zhì) 于抽雄期(VT)、灌漿期(R2)、完熟期(R6), 從每小區(qū)選取有代表性的植株5株。將其分成葉片、莖(莖稈、葉鞘、雄穗)、苞葉、穗軸和籽粒, 105℃殺青30 min后80℃烘至恒重, 測定干物質(zhì)積累量。

1.3.2 根系取樣與測定 于抽雄期(VT)對根系取樣, 選擇連續(xù)且生長均勻一致的植株5株, 以植株為中心, 行距方向半徑取30 cm, 株距方向半徑取10 cm, 每10 cm為一土層, 取樣深度為60 cm。將每一土層挖出的根土混合物裝入40目網(wǎng)袋, 在低水壓下沖洗干凈并挑出全部根系, 放入密封袋中1℃下保存。將根系樣品用Epson Perfection V700 Photo掃描儀掃描, 然后使用WinRhizo 2016根系分析軟件測定根系相關(guān)指標(biāo), 計算根長密度。將掃描完成的根系放在烘箱中烘至恒重并稱干重。

1.3.3 產(chǎn)量及產(chǎn)量構(gòu)成因素 于完熟期(R6)選取每小區(qū)18 m2(10.0 m×1.8 m)有代表性的玉米帶, 將其全部果穗收獲后曬干, 測定產(chǎn)量及產(chǎn)量構(gòu)成因素。

1.3.4 植株與土壤全氮含量 將玉米植株與土壤樣品研磨過篩后用H2SO4-H2O2聯(lián)合消煮, 用BRAN＋LUEBBE III型(德國)連續(xù)流動分析儀測定氮素含量。

1.4 數(shù)據(jù)處理與分析

植株氮素積累量(kg hm–2)=單株重×單株含氮量×公頃株數(shù);

營養(yǎng)器官氮素轉(zhuǎn)運(yùn)量(kg hm–2)=灌漿期營養(yǎng)器官氮素積累量?完熟期營養(yǎng)器官氮素積累量;

氮素轉(zhuǎn)運(yùn)效率(%)=營養(yǎng)器官氮素轉(zhuǎn)運(yùn)量/灌漿期營養(yǎng)器官氮素積累量×100;

氮素吸收效率(NAE, kg kg–1)=植株氮素積累量/施氮量;

氮素偏生產(chǎn)力(NPFP, kg kg–1)=籽粒產(chǎn)量/施氮量;

采用Microsoft Excel 2017和DPS 15.10統(tǒng)計軟件LSD法進(jìn)行方差分析, 用SigmaPlot l0.0作圖。

2 結(jié)果與分析

2.1 磷肥深施對土壤根系分布的影響

磷肥適當(dāng)深施顯著促進(jìn)夏玉米根系生長, 根干重(RDW)、根長密度(RLD)、根系表面積(RSA)以及根體積(RV)均顯著增加, 整體表現(xiàn)為P15>P10>P20> P5>CK (圖2)。與CK處理相比, P5、P10、P15和P20處理2年的平均RDW分別提高31.6%、41.6%、44.2%和36.7%, RLD分別提高42.9%、62.3%、72.9%和52.1%, RSA分別提高27.5%、46.6%、48.8%和33.5%, 而RV提高33.7%、44.8%、48.9%和42.3%。2年試驗(yàn)趨勢一致, 年度間差異較大的原因是年際間降水量的差異。

圖2 磷肥施用深度對夏玉米植株根系性狀的影響

標(biāo)以不同字母的柱值間差異達(dá)0.05顯著水平。CK: 不施磷肥; P5: 距離地表?5 cm處施磷; P10: 距離地表?10 cm處施磷; P15: 距離地表?15 cm處施磷; P20: 距離地表?20 cm處施磷。

Bars superscripted by different letters are significantly different among treatments at the 0.05 probability level. CK: no P applied; P5: phosphorus application depth was ?5 cm; P10: phosphorus application depth was ?10 cm; P15: phosphorus application depth was ?15 cm; P20: phosphorus application depth was ?20 cm. RDW: root dry weight; RLD: root length density; RSA: root surface area; RV: root volume.

磷肥施用位置可以調(diào)控夏玉米根系在土層中的分布, 隨著磷肥施用深度的增加, 深層玉米根系生長顯著增加, 其所占整體根系的比例也增大(圖3和圖4)。以2018年為例, 在0~10 cm土層, 以P5處理的RDW所占比例最大。10~20 cm土層, P10處理所占比例最大, 為20.1%; 20~40 cm土層, P15和P20處理RDW所占比重分別為12.3%和12.1%; 40~60 cm土層, P15和P20處理RDW所占比重分別為6.7%和6.9%。與P5處理相比, P10、P15和P20處理在20~40 cm土層內(nèi), RLD分別增加20.2%、27.7%和14.0%, RSA分別增加24.4%、28.3%和10.2%, 而RV則增加27.8%、41.2%和33.0%; 在40~60 cm土層, RLD增加12.4%、26.6%和17.7%, RSA增加21.8%、24.9%和30.5%, 而RV則增加28.0%、53.2%和55.3%。

圖3 不同深度土層中根系干重占整體根干重的比例

P5: 距離地表?5 cm處施磷; P10: 距離地表?10 cm處施磷; P15: 距離地表?15 cm處施磷; P20: 距離地表?20 cm處施磷。

P5: phosphorus application depth was ?5 cm; P10: phosphorus application depth was ?10 cm; P15: phosphorus application depth was ?15 cm; P20: phosphorus application depth was ?20 cm.

圖4 不同深度土層中的根系分布(2018)

CK: 不施磷肥; P5: 距離地表?5 cm處施磷; P10: 距離地表?10 cm處施磷; P15: 距離地表?15 cm處施磷; P20: 距離地表?20 cm處施磷。

CK: no P applied; P5: phosphorus application depth was ?5 cm; P10: Phosphorus application depth was ?10 cm; P15: phosphorus application depth was ?15 cm; P20: phosphorus application depth was ?20 cm. RDW: root dry weight; RLD: root length density; RSA: root surface area; RV: root volume.

2.2 磷肥深施對植株干物質(zhì)積累及籽粒產(chǎn)量的影響

與傳統(tǒng)施磷相比, 深施磷肥處理顯著增加了植株干物質(zhì)積累, 趨勢為P15>P10>P20>P5>CK (圖5)。VT期單株干物質(zhì)積累量P10、P15和P20處理較P5處理2年平均增加9.1%、13.6%和7.3%; R6期2年平均提高6.6%、14.5%和8.2%。磷肥適當(dāng)深施增加了夏玉米籽粒產(chǎn)量, 各處理產(chǎn)量表現(xiàn)為P15>P10>P20>P5>CK, P10、P15、P20較P5兩年平均增產(chǎn)8.2%、16.4%、9.0%。

植株生物量、籽粒重與根干重、根長密度均呈現(xiàn)顯著線性正相關(guān)(<0.001), 且相關(guān)系數(shù)較大, 說明玉米根系增殖有利于植株的干物質(zhì)積累及產(chǎn)量形成(圖6)。

2.3 磷肥深施對植株氮素吸收、積累及利用的影響

與傳統(tǒng)施磷處理相比, 深施磷肥處理在各土層中尤其是20 cm以下土層中氮素含量顯著降低(圖7)。磷肥適當(dāng)深施促進(jìn)了土壤中根系的增殖, 增大了根系與土壤的接觸面積, 提高了根系對氮素的吸收, 阻止氮素向深層土壤中運(yùn)移。同時, 深層土壤根系的增加增大了根系對水分和養(yǎng)分的吸收利用空間, 促進(jìn)了對深層土壤中氮素的吸收。

圖5 磷肥施用深度對夏玉米植株生物量與籽粒理論產(chǎn)量的影響

標(biāo)以不同字母的柱值間差異達(dá)0.05顯著水平。CK: 不施磷肥; P5: 距離地表?5 cm處施磷; P10: 距離地表?10 cm處施磷; P15: 距離地表?15 cm處施磷; P20: 距離地表?20 cm處施磷。

Bars superscripted by different letters are significantly different among treatments at the 0.05 probability level. CK: no P applied; P5: phosphorus application depth was ?5 cm; P10: phosphorus application depth was ?10 cm; P15: phosphorus application depth was ?15 cm; P20: phosphorus application depth was ?20 cm.

圖6 單株生物量、籽粒重與根干重、根長密度的關(guān)系

RDW: root dry weight; RLD: root length density;***< 0.001.

圖7 不同土層氮素的分布

CK: 不施磷肥; P5: 距離地表?5 cm處施磷; P10: 距離地表?10 cm處施磷; P15: 距離地表?15 cm處施磷; P20: 距離地表?20 cm處施磷。

CK: no P applied; P5: phosphorus application depth was ?5 cm; P10: phosphorus application depth was ?10 cm; P15: phosphorus application depth was ?15 cm; P20: phosphorus application depth was ?20 cm; VT: tasseling; R6: physiological maturity.

適當(dāng)深施磷肥有利于玉米植株氮素積累。2017年R6期P10、P15、P20處理與P5處理相比整株氮積累量分別提高了12.5%、25.8%、14.4%, 2018年相應(yīng)提高了1.7%、12.7%、5.9% (表2)。

磷肥適當(dāng)深施也促進(jìn)營養(yǎng)器官中氮素向籽粒的轉(zhuǎn)運(yùn), 2017年各處理的轉(zhuǎn)運(yùn)量為34.7~64.2 kg hm–2, 2018年為46.9~67.4kg hm–2, 其中P15處理轉(zhuǎn)運(yùn)量及轉(zhuǎn)運(yùn)率顯著高于其他處理(表2)。適當(dāng)深施磷肥提高了夏玉米的氮素吸收效率及偏生產(chǎn)力。與P5處理相比, P10、P15、P20處理2年平均氮素吸收效率提高4.1、14.5 和8.9 kg kg–1; 氮肥偏生產(chǎn)力分別增加3.4、6.4和2.8 kg kg–1(表2)。籽粒氮積累量、氮素吸收效率、氮肥偏生產(chǎn)力與根干重、根長密度均呈現(xiàn)顯著線性正相關(guān)(<0.001), 且相關(guān)系數(shù)較大, 說明玉米根系的增殖有利于氮素吸收、積累與利用(圖8)。

表2 磷肥施用深度對植株中氮積累量、轉(zhuǎn)運(yùn)及吸收利用的影響

(續(xù)表2)

同列標(biāo)以不同字母的值在處理間差異達(dá)0.05顯著水平。CK: 不施磷肥; P5: 距離地表–5 cm處施磷; P10: 距離地表–10 cm處施磷; P15: 距離地表–15 cm處施磷; P20: 距離地表–20 cm處施磷。

Values followed by different letters within a column are significantly different among treatments at the 0.05 probability level. CK: no P applied; P5: phosphorus application depth was –5 cm; P10: phosphorus application depth was –10 cm; P15: phosphorus application depth was –15 cm; P20: phosphorus application depth was –20 cm. NAE: nitrogen fertilizer absorption efficiency; NPFP: nitrogen partial factor productivity; R2: grain filling; R6: physiological maturity.

圖8 籽粒氮積累量(GNAA)、氮素吸收效率(NAE)、氮肥偏生產(chǎn)力(NPFP)與根干重(RDW)、根長密度(RLD)的關(guān)系

3 討論

農(nóng)田耕作方式、施肥及灌溉等田間管理措施的差異造成土壤中養(yǎng)分、水分分布的高度異質(zhì)性。根系對土壤中養(yǎng)分資源的異質(zhì)性在生理和形態(tài)上存在的一系列可塑性反應(yīng)[22,27], 對養(yǎng)分斑塊的響應(yīng)一般包括根系的伸長, 總根長及側(cè)根分支密度增大等一系列變化[12,28]。通過改變養(yǎng)分供應(yīng)位置及強(qiáng)度, 可以有效刺激根系生長或增殖, 顯著提高對土壤養(yǎng)分的吸收面積[19,29]。張福鎖等[6]研究表明通過根層養(yǎng)分調(diào)控可以優(yōu)化植物-土壤系統(tǒng)中的根區(qū)養(yǎng)分輸入, 調(diào)節(jié)根系生長發(fā)育, 最大限度地提高根系養(yǎng)分獲取效率, 以實(shí)現(xiàn)作物高產(chǎn)高效可持續(xù)生產(chǎn)。在本研究中, 通過調(diào)整磷肥施用深度對夏玉米進(jìn)行根層調(diào)控, 改變磷素在土壤中的分布斑塊, 對夏玉米根系生長與分布有顯著的誘導(dǎo)效應(yīng)。磷肥適當(dāng)深施顯著促進(jìn)了土壤中根系的增殖, 增加了夏玉米根干重、根長密度和根系表面積(圖2), 促進(jìn)深層土壤根系的生長, 根系與土壤的接觸面積顯著增大。

肥料運(yùn)籌對土壤中肥力及養(yǎng)分分布影響顯著[24,30-31]。肥料施用位置可以改變根系在土壤中的分布, 影響肥料養(yǎng)分在土壤中的運(yùn)移、轉(zhuǎn)化以及在作物體內(nèi)的積累和分配[4,32-33], 提高作物產(chǎn)量和肥料利用效率。適度下移磷肥施用深度能夠誘導(dǎo)玉米根系向下生長,有利于提高磷素吸收效率、磷肥利用效率和籽粒產(chǎn)量; 隨著磷肥施用深度的增加, 玉米收獲期氮素吸收量呈現(xiàn)顯著增加趨勢[21,34]。在本試驗(yàn)中, 隨著磷肥施用深度的增加, 玉米根系呈現(xiàn)向深層分布的趨勢, 深層土壤中玉米根系比例顯著增加, 提高了根系對土壤氮素的吸收, 阻止氮素向深層土壤遷移, 同時擴(kuò)大根系的養(yǎng)分利用空間, 促進(jìn)根系對深層土壤氮素的吸收(圖7)。磷肥適當(dāng)深施有利于生育后期氮素從營養(yǎng)器官向籽粒的轉(zhuǎn)運(yùn), 增大氮素的轉(zhuǎn)運(yùn)率, 其中以P15處理轉(zhuǎn)運(yùn)量最大。磷肥深施促進(jìn)植株氮素吸收的原因主要是促進(jìn)根系的生長發(fā)育, 增強(qiáng)了根層土壤氮素與根系時空分布的匹配性, 尤其增加下層土壤中根系的比重, 擴(kuò)大根系對氮素的吸收利用空間, 增強(qiáng)氮素吸收能力。

合理根系構(gòu)型能夠提高植株對水分與養(yǎng)分等資源的獲取及利用效率[8-9], 促進(jìn)植株生長及產(chǎn)量形成。Jing等[35-36]的研究表明局部施磷和銨態(tài)氮的養(yǎng)分調(diào)控能夠促進(jìn)根系的大量增生并強(qiáng)化根際過程, 促進(jìn)玉米生育前期的生長及養(yǎng)分吸收。氮肥適量深施為根系向深層擴(kuò)展提供了良好條件, 促使根系下移, 保證超高產(chǎn)春玉米較高的有效穗數(shù)、千粒重和穗粒數(shù), 從而提高產(chǎn)量[29]。本試驗(yàn)結(jié)果表明, 磷肥適當(dāng)深施同樣促進(jìn)了夏玉米植株的生長, 其生物量與籽粒產(chǎn)量顯著增加(圖5)。磷肥適當(dāng)深施, 在增大根系與土壤磷肥接觸面積的同時, 誘導(dǎo)根系下扎, 增加了根系對土壤氮素吸收利用的空間, 協(xié)調(diào)了氮磷高效利用根系構(gòu)型之間的矛盾, 實(shí)現(xiàn)了根系對土壤氮磷養(yǎng)分的協(xié)調(diào)吸收利用, 最終促進(jìn)植株生長及籽粒產(chǎn)量形成。

綜上所述, 磷肥深施的根層調(diào)控技術(shù)可以有效挖掘作物根系生物學(xué)潛力, 在調(diào)節(jié)根系分布, 保證根系與磷肥較大接觸面積的同時, 誘導(dǎo)夏玉米根系分布加深, 增加水分和氮素的吸收利用空間, 促進(jìn)氮素的高效吸收與轉(zhuǎn)運(yùn), 提高了對土壤氮素的利用效率和籽粒產(chǎn)量。

4 結(jié)論

磷肥適度深施能夠顯著促進(jìn)夏玉米根系的生長, 改變根系在土壤中的分布。磷肥集中施用在?15 cm增加了20~60 cm土層中的根系干重比重及根長密度, 促進(jìn)了根系對深層土壤氮素的吸收, 顯著增加了植株氮素的積累及轉(zhuǎn)運(yùn), 提高其物質(zhì)生產(chǎn)能力, 最終籽粒產(chǎn)量比傳統(tǒng)的磷肥撒施顯著增產(chǎn)16.4%。

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The root-layer regulation based on the depth of phosphate fertilizer application of summer maize improves soil nitrogen absorption and utilization

CHEN Xiao-Ying, LIU Peng*, CHENG Yi, DONG Shu-Ting, ZHANG Ji-Wang, ZHAO Bin, REN Bai-Zhao, and HAN Kun

State Key Laboratory of Crop Biology / College of Agronomy, Shandong Agricultural University, Tai’an 271018, Shandong, China

Favorable root phenotypes can promote crops to obtain soil nutrients efficiently. The root-layer regulation technology based on the depth of phosphate fertilizer application can optimize the spatial and temporal distribution of summer maize root system and promote its spatial matching with soil water and nutrients to supply, providing a theoretical and technical support for realizing fertilizer saving and efficiency improvement by tapping potential of maize root system. In the present study, there were five treatments including CK (no P applied), P5 (phosphorus placement depth of 5 cm), P10 (phosphorus placement depth of 10 cm), P15 (phosphorus placement depth of 15 cm), and P20 (phosphorus placement depth of 20 cm). The effect of phosphorus application depth on root distribution, plant growth and yield formation, as well as nitrogen uptake, accumulation and transport in summer maize was analyzed. The suitable application depths of phosphate fertilizer promoted the growth of summer maize roots and increased root dry weight, root length density, root surface area and root volume significantly totally showing a trend of P15 > P10 > P20 > P5 > CK. With the increase of phosphate fertilizer application depth, the deep corn roots increased significantly. The proportion of root dry weight in P15 and P20 treatments was 12.3% and 12.1% in the 20–40 cm soil layer, and 6.7% and 6.9% in the 40–60 cm soil layer, respectively. The increase of root distribution depth promoted the absorption of nitrogen in the soil, and the nitrogen content in each soil layer, especially below 20 cm, was reduced significantly by the deep application of phosphate fertilizer. The optimization of root distribution promoted the accumulation and transportation of nitrogen in plants. Compared with P5 treatment, the averaged nitrogen fertilizer absorption efficiency, accumulation amount, accumulation rate, partial factor productivity and the grain yield in two years of P15 treatment increased by 14.5 kg kg–1, 19.2%, 48.9%, 6.4 kg kg–1, and 16.4% respectively, showing that under the conditions of the present study, concentrated application of phosphate fertilizer in ?15 cm treatment can significantly promote the growth of deep soil roots, expand the space of nutrient utilization for root system, increase the absorption of nitrogen in deep soil, promote the accumulation and transportation of plant nitrogen, improve the productivity and ultimately yield in summer maize.

summer maize; phosphorus placement depth; root; yield; nitrogen absorption and utilization

本研究由國家重點(diǎn)研發(fā)計劃項(xiàng)目(2016YFD0300106, 2018YFD0300603), 國家自然科學(xué)基金項(xiàng)目(31771713, 31371576)和山東省現(xiàn)代農(nóng)業(yè)產(chǎn)業(yè)技術(shù)體系項(xiàng)目(SDAIT-02-08)資助。

This study was supported by the National Basic Research Program of China (2016YFD0300106, 2018YFD0300603), the National Natural Science Foundation of China (31771713, 31371576), and the Shandong Province Key Agricultural Project for Application Technology Innovation (SDAIT-02-08).

10.3724/SP.J.1006.2020.93029

劉鵬, E-mail: liupengsdau@126.com, Tel: 0538-8241485

E-mail: 15621567129@163.com

***< 0.001.

2019-05-01;

2019-09-26;

2019-10-09.

URL:http://kns.cnki.net/kcms/detail/11.1809.S.20191009.1500.003.html