張翔宇 胡鑫慧 谷淑波 林 祥 殷復(fù)偉 王 東,*

減氮條件下分期施鉀對冬小麥籽粒產(chǎn)量和氮素利用效率的影響

張翔宇1胡鑫慧1谷淑波1林 祥2殷復(fù)偉3王 東2,*

1山東農(nóng)業(yè)大學(xué)/ 作物生物學(xué)國家重點(diǎn)實(shí)驗(yàn)室, 山東泰安 271018;2西北農(nóng)林科技大學(xué)農(nóng)學(xué)院, 陜西楊凌 712100;3泰安市農(nóng)業(yè)技術(shù)推廣中心, 山東泰安 271000

為探究鉀肥分期施用對冬小麥產(chǎn)量和氮素利用效率的影響, 確定減氮條件下冬小麥高產(chǎn)高效的鉀肥運(yùn)籌方案, 本試驗(yàn)選用高產(chǎn)強(qiáng)筋冬小麥品種藁優(yōu)5766作為試驗(yàn)材料, 于2018—2020年度冬小麥生長季, 采用二因素隨機(jī)區(qū)組設(shè)計(jì), 設(shè)置3個施氮水平: 常規(guī)施氮水平(240 kg hm–2, N1)、減氮20% (192 kg hm–2, N2)、減氮40% (144 kg hm–2, N3), 兩種鉀肥運(yùn)籌方案: 鉀肥全部底施(K1)和分期施鉀(底施50%、拔節(jié)期追施50%, K2)。結(jié)果表明, 相同鉀肥運(yùn)籌方案下, N2處理的籽粒產(chǎn)量與N1處理無顯著差異, N3處理的籽粒產(chǎn)量比N1處理顯著降低, 降幅達(dá)9.0%～11.6%。在相同施氮水平下, 分期施鉀可顯著提高冬小麥籽粒產(chǎn)量和氮素利用效率。與K1處理相比, K2處理顯著抑制硝態(tài)氮向深層土壤的淋溶, 增加冬小麥植株氮素積累量, 提高旗葉光合速率和硝酸還原酶活性、籽粒灌漿速率、穗粒數(shù)和千粒重; 籽粒產(chǎn)量和氮素利用效率在常規(guī)施氮水平下兩年度分別提高21.7%和20.2%, 在減氮20%水平下兩年度分別提高26.9%和26.2%, 在減氮40%水平下兩年度分別提高25.2%和21.1%。N3K2處理的籽粒產(chǎn)量、氮素吸收效率、氮素利用效率和氮肥偏生產(chǎn)力均顯著高于N1K1處理。以上結(jié)果說明分期施鉀在不同施氮水平下均能大幅度提高冬小麥籽粒產(chǎn)量和氮素利用效率, 即使減氮40%, 其籽粒產(chǎn)量仍顯著高于常規(guī)施氮且鉀肥全部底施的處理; 采用192 kg hm–2施氮量并配合分期施鉀, 冬小麥籽粒產(chǎn)量和氮素吸收效率最高, 氮素利用效率和氮肥偏生產(chǎn)力亦到達(dá)較高水平, 是高產(chǎn)高效的氮鉀肥運(yùn)籌方案。

冬小麥; 減氮; 分期施鉀; 籽粒產(chǎn)量; 氮素利用效率

小麥作為世界上重要的作物之一[1], 為人類提供約21%的食物[2]; 氮肥作為小麥生長季必不可少的肥料, 對小麥的產(chǎn)量有重要影響[3-5]。然而, 過度追求通過提高施氮量增產(chǎn)導(dǎo)致氮素利用效率降低、生產(chǎn)成本增加; 同時(shí), 多余的氮肥還會增加溫室氣體的排放[6]、污染地下水等[7]。近年來對氮肥的管理逐漸重視, 2012年到2020年, 氮肥用量降低23.6%。大量研究表明, 黃淮海麥區(qū)常規(guī)施氮量為240 kg hm–2, 將施氮量由240 kg hm–2降低到180 kg hm–2時(shí), 籽粒產(chǎn)量下降幅度不明顯, 氮素利用效率卻顯著提高[8], 繼續(xù)降低到120 kg hm–2時(shí), 籽粒產(chǎn)量大幅度下降[9]。有研究表明, 施鉀可以促進(jìn)作物對氮素的吸收, 也能提高氮素利用效率[10]。分期施鉀能夠增加植株氮素和鉀素的積累量, 提高開花后旗葉的凈光合速率和淀粉合成酶的活性, 增加冬小麥的籽粒產(chǎn)量[11-14]。在不改變施鉀量的情況下, 分期施鉀與鉀肥一次性底施相比, 冬小麥的籽粒產(chǎn)量顯著提高[15]。可以看出, 分期施鉀無需增加鉀素的投入即可達(dá)到增產(chǎn)效果。那么, 分期施鉀能否與減量施氮相配合在減氮條件下實(shí)現(xiàn)增加籽粒產(chǎn)量、提高氮素利用效率的效果呢？目前還鮮有相關(guān)的研究報(bào)道。因此, 本文在3個施氮水平(常規(guī)施氮、減氮20%和減氮40%)下, 設(shè)置鉀肥一次性底施和分期施鉀兩種施鉀方式處理, 探索減氮條件下分期施鉀對冬小麥籽粒產(chǎn)量和氮素利用效率的影響, 以期為冬小麥綠色高產(chǎn)高效栽培提供理論依據(jù)。

1 材料與方法

1.1 試驗(yàn)地概況

試驗(yàn)于2018—2019年和2019—2020年冬小麥生長季在山東省泰安市道朗鎮(zhèn)玄莊村(36°12′N, 116°54′E)大田進(jìn)行, 試驗(yàn)地前茬作物為玉米。該地區(qū)屬溫帶大陸性季風(fēng)氣候, 年均氣溫為13.0～13.6℃, 年均降雨量為621.2～688.0 mm。試驗(yàn)地土壤類型為沙壤土。小麥播種前0～20 cm土層土壤含有機(jī)質(zhì)9.4 g kg–1、全氮1.79 g kg–1、堿解氮78.82 mg kg–1、速效磷22.85 mg kg–1、速效鉀97.06 mg kg–1。

1.2 試驗(yàn)設(shè)計(jì)

試驗(yàn)材料選用高產(chǎn)強(qiáng)筋冬小麥品種藁優(yōu)5766, 采用二因素隨機(jī)區(qū)組設(shè)計(jì), 設(shè)置3個施氮水平: 常規(guī)施氮水平(240 kg hm–2, N1)、減氮20% (192 kg hm–2, N2)、減氮40% (144 kg hm–2, N3), 2種鉀肥運(yùn)籌方案: 鉀肥全部底施(K1)和分期施鉀(底施50%、拔節(jié)期追施50%, K2)。每個處理3次重復(fù), 小區(qū)面積為2 m×9 m=18 m2。試驗(yàn)各處理磷肥和鉀肥的施用量一致, 分別為120 kg P2O5hm–2和120 kg K2O hm–2。所用氮肥為尿素(含N 46%), 磷肥為重過磷酸鈣(含P2O546%), 鉀肥為氯化鉀(含K2O 60%)。磷肥全部底施, 氮肥50%于播種期底施, 50%于拔節(jié)期溶解成肥液后隨灌溉水追施。冬小麥三葉一心期定苗, 留苗密度為每公頃185萬株。2018—2019年度試驗(yàn)于10月3日播種, 6月4日收獲; 2019—2020年度試驗(yàn)于10月9日播種, 6月4日收獲, 其他管理措施同一般高產(chǎn)田。

1.3 測定項(xiàng)目與方法

1.3.1 產(chǎn)量及其構(gòu)成因素 成熟期每小區(qū)隨機(jī)選取0.5 m2調(diào)查單位面積穗數(shù), 隨機(jī)選取50個麥穗, 調(diào)查穗粒數(shù); 每小區(qū)收獲2 m2脫粒, 風(fēng)干至籽粒含水率達(dá)到12.5%左右時(shí)稱重, 計(jì)算單位面積籽粒產(chǎn)量, 同時(shí)調(diào)查千粒重。每個處理3次重復(fù)。

1.3.2 冬小麥氮素利用效率

氮素利用效率(NUE, kg kg–1)=籽粒產(chǎn)量(kg hm–2)/地上部植株氮素積累量(kg hm–2)

氮素吸收效率(NUpE, kg kg–1)=地上部植株氮素積累量(kg hm–2)/施氮量(kg hm–2)

氮肥偏生產(chǎn)力(PFPn, kg kg–1)=籽粒產(chǎn)量(kg hm–2)/施氮量(kg hm–2)

1.3.3 土壤硝態(tài)氮含量 于冬小麥拔節(jié)期、開花期和成熟期, 使用土鉆, 每10 cm一層采集0～40 cm土層土壤樣品, 每20 cm一層采集40～200 cm土層土壤樣品, 并于–20℃條件下保存, 之后用AA3流動分析儀測定土壤硝態(tài)氮含量。

1.3.4 植株氮素含量 于越冬期、返青期、拔節(jié)期、開花期和成熟期采集冬小麥地上部植株樣品。采用濃硫酸消煮, 用國標(biāo)GB2905-1982半微量凱氏定氮法測定植株地上部全氮含量。

1.3.5 植株氮素積累與分配

各器官氮素積累量(kg hm–2)=各器官干重×各器官氮素含量

花后同化氮素輸入籽粒量(kg hm–2)=成熟期籽粒氮素積累量-花前營養(yǎng)器官貯藏氮素轉(zhuǎn)運(yùn)量

花后同化氮素對籽粒的貢獻(xiàn)率(%)=花后同化氮素在籽粒中的分配量/成熟期籽粒氮素積累量×100

1.3.6 旗葉硝酸還原酶活性(NR) 于開花后0、10、20和30 d隨機(jī)采集冬小麥旗葉, 每小區(qū)30片。參照鄒琦等(2000)主編《植物生理學(xué)實(shí)驗(yàn)指導(dǎo)》中的方法測定冬小麥旗葉硝酸還原酶活性。

1.3.7 旗葉葉綠素相對含量(SPAD值)及凈光合速率(n) 于開花后0、10、20和30 d (晴天)的上午09:00—11:00, 每處理隨機(jī)選取5片旗葉, 采用日本產(chǎn)SPAD-502葉綠素測量儀測量葉綠素相對含量(SPAD值), 采用美國產(chǎn)Li-6400型便攜式光合儀, 在固定光源1400 μmol m–2s–1光強(qiáng)下測量凈光合速率。

1.3.8 籽粒灌漿速率 于開花期選取各處理小區(qū)內(nèi)長相基本一致且同一天開花的穗掛牌標(biāo)記, 并于開花后7、14、21、28和35 d每小區(qū)隨機(jī)采集15個麥穗, 置烘箱內(nèi)于105℃條件下殺青30 min, 再于75℃條件下烘干至恒重, 脫粒測定平均單粒重。籽粒灌漿速率計(jì)算公式如下:

籽粒灌漿速率(mg kernel–1d–1) = (后1次取樣單粒干重–前1次取樣單粒干重)/2次取樣間隔天數(shù)。

2 結(jié)果與分析

2.1 不同處理對冬小麥籽粒產(chǎn)量和氮素利用效率的影響

從表1可以看出, 在同一施氮水平下, 分期施鉀與鉀肥全部底施相比, 顯著提高冬小麥籽粒產(chǎn)量、氮素利用效率和氮肥偏生產(chǎn)力。與K1處理相比, K2處理2018—2019年籽粒產(chǎn)量在N1、N2和N3水平下分別提高24.6%、26.6%和27.5%; 2019—2020年籽粒產(chǎn)量分別提高18.7%、27.08%和22.9%。兩年度, N2K2處理與N1K2處理的籽粒產(chǎn)量無顯著差異, 但顯著高于其余處理。N3K2處理的籽粒產(chǎn)量、氮素吸收效率、氮素利用效率和氮肥偏生產(chǎn)力均顯著高于N1K1處理。說明分期施鉀能大幅度提高冬小麥籽粒產(chǎn)量和氮素利用效率, 即使減氮40%, 其籽粒產(chǎn)量仍顯著高于常規(guī)施氮且鉀肥全部底施的處理。

表1 不同處理對冬小麥籽粒產(chǎn)量和氮素利用效率的影響

N1: 常規(guī)施氮(240 kg hm–2); N2: 減氮20% (192 kg hm–2); N3: 減氮40% (144 kg hm–2); K1: 鉀肥全部底施; K2: 分期施鉀(底施50%, 拔節(jié)期追施50%)。NUE: 氮素利用效率; NUpE: 氮素吸收效率; PEPn: 氮肥偏生產(chǎn)力。數(shù)據(jù)后不用字母表示同一年度的不同處理之間差異顯著(< 0.05)。

N1: conventional nitrogen application rate (240 kg hm–2); N2: nitrogen application rate was reduced by 20% (192 kg hm–2); N3: nitrogen application rate was reduced by 40% (144 kg hm–2); K1: all potassium fertilizers were applied at the sowing stage; K2: potassium fertilizer application in stages (50% was applied at the sowing stage, 50% was applied at the jointing stage). NUE: nitrogen use efficiency; NUpE: nitrogen uptake efficiency; PEPn: nitrogen partial productivity. Different letters after date indicate significant difference among treatments in each growing season (< 0.05).

2.2 不同處理對土壤硝態(tài)氮時(shí)空變化的影響

在同一施氮水平下, 拔節(jié)期追肥前, K1處理0～40 cm土層土壤硝態(tài)氮含量顯著大于K2處理, 40～200 cm土層土壤硝態(tài)氮含量顯著小于K2處理(圖1); 開花期和成熟期, K1處理0～40 cm土層土壤硝態(tài)氮含量顯著小于K2處理, 40～200 cm土層土壤硝態(tài)氮含量顯著大于K2處理(圖2和圖3)。表明拔節(jié)期追施鉀肥可以顯著提高拔節(jié)后0～40 cm土層土壤的硝態(tài)氮含量, 減少硝態(tài)氮向深層土壤淋溶。

圖1 不同處理對拔節(jié)期0～200 cm土層土壤硝態(tài)氮含量的影響

N1: 常規(guī)施氮(240 kg hm–2); N2: 減氮20% (192 kg hm–2); N3: 減氮40% (144 kg hm–2); K1: 鉀肥全部底施; K2: 分期施鉀(底施50%, 拔節(jié)期追施50%)。

N1: conventional nitrogen application rate (240 kg hm–2); N2: nitrogen application rate was reduced by 20% (192 kg hm–2); N3: nitrogen application rate was reduced by 40% (144 kg hm–2); K1: all potassium fertilizers were applied at the sowing stage; K2: potassium fertilizer application in stages (50% was applied at sowing stage, 50% was applied at jointing stage).

圖2 不同處理對開花期0～200 cm土層土壤硝態(tài)氮含量的影響

處理同圖1。Treatments are the same as those given in Fig. 1.

(圖3)

處理同圖1。Treatments are the same as those given in Fig. 1.

2.3 不同處理對冬小麥植株氮素積累動態(tài)的影響

如圖4所示, 在N1水平下, K2處理植株氮素積累量與K1處理的無顯著差異; 在N2和N3水平下, K2處理成熟期的植株氮素積累量顯著高于K1處理的, 其余時(shí)期二者無顯著差異。相同施鉀方式下, N3處理的植株氮素積累量顯著低于N1和N2處理; 且N1K1的植株氮素積累量顯著高于N2K1的, 但N1K2的植株氮素積累量與N2K2的無顯著差異。表明冬小麥植株氮素積累量隨著施氮量的降低而顯著降低; 分期施鉀可顯著提高植株氮素積累量, 從而在一定程度上彌補(bǔ)減氮對冬小麥氮素積累的負(fù)面影響。

2.4 不同處理對冬小麥植株氮素積累與分配的影響

從表2可以看出, 在同一施氮水平下, 分期施鉀與鉀肥全部底施相比, 顯著提高成熟期籽粒氮素積累量和花后氮素同化量, 降低成熟期營養(yǎng)器官氮素積累量; 在N2和N3水平下, 還顯著提高了花后同化氮素量及其對籽粒的貢獻(xiàn)率。表明在減氮條件下, 分期施鉀不僅可以促進(jìn)開花后營養(yǎng)器官氮素向籽粒轉(zhuǎn)運(yùn), 而且顯著提高花后同化氮素量及其對籽粒的貢獻(xiàn)率。

圖4 不同處理植株氮素積累量變化動態(tài)

處理同圖1。Treatments are the same as those given in Fig. 1.

表2 不同處理對冬小麥植株氮素積累與分配的影響

處理同圖1。Treatments are the same as those given in Fig. 1.

2.5 不同處理對冬小麥開花后旗葉硝酸還原酶活性(NR)的影響

如圖5所示, 在N1水平下, K2處理開花后10 d的旗葉硝酸還原酶活性顯著大于K1處理的, 其余時(shí)期與K1處理的無顯著差異; 在N2和N3水平下, K2處理開花后10～20 d的旗葉硝酸還原酶活性顯著大于K1處理的, 其余時(shí)期與K1處理的無顯著差異。表明分期施鉀可顯著提高籽粒灌漿中期的旗葉硝酸還原酶活性, 對氮素同化有利。

2.6 不同處理對冬小麥開花后旗葉葉綠素相對含量(SPAD)的影響

如圖6所示, 同一施氮水平下, K2處理開花后旗葉葉綠素相對含量顯著高于K1處理的; 其中在N1條件下兩年度分別提高7.8%和6.4%, 在N2條件下兩年度分別提高24.1%和32.1%, 在N3條件下兩年度分別提高14.7%和18.1%。表明分期施鉀在各施氮水平下均可顯著提高冬小麥開花后旗葉葉綠素的相對含量, 以在N2條件下的提高幅度最大。

2.7 不同處理對冬小麥開花后旗葉凈光合速率(Pn)的影響

如圖7所示, 在相同施氮水平下, K2處理開花后旗葉凈光合速率總體上大于K1處理。在N1、N2和N3水平下, 兩年度平均增幅分別為20.1%、23.0%和17.3%。表明分期施鉀在各施氮水平下均能顯著提高冬小麥開花后旗葉的凈光合速率, 以在減氮20%的條件下提高的幅度最大。

圖5 2018–2019年度不同處理對冬小麥開花后旗葉硝酸還原酶活性(NR)影響

處理同圖1。Treatments are the same as those given in Fig. 1.

圖6 冬小麥開花后旗葉葉綠素相對含量(SPAD)

處理同圖1。Treatments are the same as those given in Fig. 1.

圖7 不同處理冬小麥開花后旗葉凈光合速率(Pn)

處理同圖1。Treatments are the same as those given in Fig. 1.

2.8 不同處理對冬小麥籽粒灌漿速率的影響

如圖8所示, 同一施氮水平下, K1處理在開花后0～20 d的籽粒灌漿速率高于K2處理的, 在開花后20～35 d的籽粒灌漿速率則顯著低于K2處理的。表明分期施鉀對冬小麥開花20 d后的籽粒灌漿速率有明顯促進(jìn)作用。

3 討論

3.1 氮鉀施用對土壤硝態(tài)氮時(shí)空變化的影響

硝態(tài)氮作為土壤中無機(jī)氮的主要存在形式, 易被小麥吸收利用, 但其在土壤中不易被膠體吸附、移動性強(qiáng), 是土壤氮素淋溶的主要部分[16]。土壤中的鉀素與氮素存在一定程度的交互作用。K+的增多有利于NH4+在土壤溶液中保留, 進(jìn)而在硝化細(xì)菌的作用下轉(zhuǎn)換成NO3– [17]。土壤中的NO3–與K+存在耦合遷移現(xiàn)象, 施氮量提高引起的NO3–大量淋失會間接導(dǎo)致K+的大量淋失[18]。本試驗(yàn)改鉀肥一次性底施為底追結(jié)合分期施用, 拔節(jié)期追施鉀肥顯著提高拔節(jié)后0～40 cm土層土壤硝態(tài)氮的含量, 降低40～200 cm土層土壤的硝態(tài)氮含量。說明在144～240 kg hm–2施氮量范圍內(nèi), 將50%的鉀肥由播種期移至拔節(jié)期施用, 不僅提高冬小麥主要根層土壤硝態(tài)氮含量, 而且減少硝態(tài)氮向深層土壤的運(yùn)移。這可能與土壤中鉀素和氮素在一定濃度范圍內(nèi)的互作有關(guān), 其機(jī)制尚待進(jìn)一步探討。

圖8 不同處理對籽粒灌漿速率的影響

處理同圖1。Treatments are the same as those given in Fig. 1.

3.2 氮鉀施用對冬小麥氮素吸收、積累與分配的影響

適宜的施氮量有利于小麥對氮素的吸收和積累[19]。在土壤堿解氮含量為88.2 mg kg–1的土壤條件下, 施氮量由135 kg hm–2增至180 kg hm–2時(shí), 小麥植株氮素積累量顯著提高, 繼續(xù)增加施氮量, 植株氮素積累量無顯著增加, 甚至降低[20]。在土壤堿解氮含量為53.5 mg kg–1的條件下, 施氮量由300 kg hm–2降至225 kg hm–2, 植株氮素積累量反而呈增加趨勢[21]。以上結(jié)果說明過多的氮素投入并不能增加小麥植株氮素的積累。K+可以充當(dāng)NO3–的電化學(xué)平衡, 促進(jìn)植株對NO3–的吸收[22]。適宜的施鉀量可以提高硝酸還原酶的活性[23], 增加植株氮素積累量[24],同時(shí)還能提高花后同化氮素對籽粒的貢獻(xiàn)率[25]。本試驗(yàn)結(jié)果表明, 分期施鉀可以提高籽粒灌漿中期旗葉硝酸還原酶的活性, 提高氮素同化能力。在常規(guī)施氮量條件下, 分期施鉀對植株成熟期氮素積累和花后同化氮素量及其對籽粒的貢獻(xiàn)率并無顯著影響,在減氮20%和40%的條件下則可以顯著增加植株成熟期氮素積累量, 提高花后同化氮素量及其對籽粒的貢獻(xiàn)率。說明鉀素對小麥氮素吸收、積累與分配的調(diào)節(jié)效應(yīng)受氮素供給水平的影響, 在減氮條件下, 可以通過分期施鉀, 增強(qiáng)小麥旗葉硝酸還原酶活性, 促進(jìn)氮素同化和積累, 提高花后同化氮素量及其對籽粒的貢獻(xiàn)率, 從而保持較高的植株氮素積累量和籽粒產(chǎn)量。

3.3 氮鉀施用對冬小麥光合同化的影響

適宜的施氮量能夠提高旗葉葉綠素相對含量, 延緩旗葉衰老[26]。有研究表明, 在土壤全氮含量為0.88 g kg–1的條件下, 施氮量由90 kg hm–2增至180 kg hm–2, 冬小麥旗葉SPAD值和凈光合速率顯著提高, 繼續(xù)增加施氮量至270 kg hm–2, 旗葉SPAD值和凈光合速率無顯著變化[27]。還有研究表明, 在土壤全氮含量為1.6 g kg–1的條件下, 施氮量由225 kg hm–2增至300 kg hm–2時(shí), 小麥開花后旗葉SPAD值顯著降低[28]。通過分期施鉀, 提高生育中后期供鉀水平也能提高開花后旗葉SPAD值和凈光合速率, 延長光合高值和灌漿持續(xù)時(shí)間[29-32]。本研究結(jié)果進(jìn)一步證明, 在不同施氮水平下, 分期施鉀均能顯著提高旗葉SPAD值、凈光合速率和灌漿持續(xù)時(shí)間, 但是以在施氮量為192 kg hm–2條件下的增幅最大, 相比常規(guī)施氮(施氮量為240 kg hm–2)和減氮40% (施氮量為144 kg hm–2)的處理, 旗葉凈光合速率分別提高2.9%和5.6%。說明適宜的供氮水平有利于發(fā)揮鉀素對小麥光合同化的正向調(diào)節(jié)作用。

3.4 氮鉀施用對冬小麥籽粒產(chǎn)量和氮素利用效率的影響

有研究表明, 在土壤堿解氮含量為53.54 mg kg–1的條件下, 施氮量由300 kg hm–2降低至240 kg hm–2, 小麥產(chǎn)量無顯著差異, 氮素利用效率顯著提高; 繼續(xù)降低至225 kg hm–2, 氮素利用效率顯著降低[21]。在土壤堿解氮含量為112.4 mg kg–1的條件下, 施氮量由240 kg hm–2降低至180 kg hm–2, 小麥產(chǎn)量無顯著差異, 氮素利用效率顯著提高[8]。說明土壤含氮量不同, 施氮量對小麥氮素利用效率的調(diào)控效果存在明顯的差異, 過高的氮素供給水平無益于作物產(chǎn)量和氮素利用效率的提高。本試驗(yàn)田土壤堿解氮含量為78.82 mg kg–1, 相同施鉀方式下將施氮量由240 kg hm–2降低至192 kg hm–2, 產(chǎn)量無顯著變化, 氮素利用效率顯著提高; 繼續(xù)降至144 kg hm–2后, 產(chǎn)量大幅度下降。說明在土壤堿解氮含量為78.82 mg kg–1的條件下, 短期內(nèi)(連續(xù)2年)將施氮量由240 kg hm–2降低至192 kg hm–2, 可以在保持產(chǎn)量的前提下提高冬小麥氮素利用效率, 長期減氮效應(yīng)還有待進(jìn)一步探討。另有研究表明, 在土壤速效鉀含量為74.1 mg kg–1的條件下, 施鉀量由0 kg hm–2增至100 kg hm–2, 水稻產(chǎn)量提高23.9%[33]。在土壤速效鉀含量為88.7 mg kg–1的條件下, 施鉀量由180 kg hm–2增至360 kg hm–2, 甘薯產(chǎn)量僅提高1.4%, 而氮素利用效率降低15.6%[34]。在土壤速效鉀含量為202 mg kg–1的條件下, 施鉀量由50 kg hm–2增至100 kg hm–2, 冬小麥的產(chǎn)量和氮素利用效率分別降低4.2%和8.0%[27]。說明土壤含鉀量不同, 施鉀量對作物產(chǎn)量和氮素利用效率的調(diào)控效果存在明顯的差異, 過高的鉀素供給水平無益于作物產(chǎn)量和氮素利用效率的提高。在施氮量為270 kg hm–2和施鉀量為135 kg hm–2的條件下, 分期施鉀相較于一次性底施鉀, 產(chǎn)量和氮素利用效率分別提高4.7%和7.6%[13]。本試驗(yàn)中分期施鉀與鉀肥一次性底施相比, 在施氮量分別為240、192、144 kg hm–2的條件下, 冬小麥產(chǎn)量分別提高21.7%、26.9%和25.2%, 氮素利用效率分別提高20.2%、26.2%和21.1%。在施氮量為192 kg hm–2的條件下, 分期施鉀對產(chǎn)量和氮素利用效率的提高幅度最大。說明適宜的施氮量配合分期施鉀有利于實(shí)現(xiàn)冬小麥產(chǎn)量和氮素利用效率的同步提高。

4 結(jié)論

在土壤堿解氮和速效鉀含量分別為78.82 mg kg–1和97.06 mg kg–1的條件下, 分期施鉀與鉀肥全部底施相比, 顯著抑制土壤硝態(tài)氮向深層土壤的淋溶, 提高冬小麥拔節(jié)后0～40 cm土層土壤硝態(tài)氮含量, 增加植株氮素積累量、花后同化氮素對籽粒的貢獻(xiàn)率和穗粒數(shù), 提高旗葉硝酸還原酶活性和凈光合速率, 促進(jìn)籽粒灌漿, 提高千粒重。在144～240 kg hm–2施氮量范圍內(nèi), 分期施鉀均能大幅度提高冬小麥籽粒產(chǎn)量和氮素利用效率; 即使減氮40% (施氮量為144 kg hm–2), 籽粒產(chǎn)量仍顯著高于常規(guī)施氮且鉀肥全部底施的處理。采用192 kg hm–2施氮量并配合分期施鉀, 冬小麥籽粒產(chǎn)量和氮素吸收效率最高, 氮素利用效率和氮肥偏生產(chǎn)力亦到達(dá)較高水平, 是高產(chǎn)高效的氮鉀肥運(yùn)籌方案。

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Effects of staged potassium application on grain yield and nitrogen use efficiency of winter wheat under reduced nitrogen conditions

ZHANG Xiang-Yu1, HU Xin-Hui1, GU Shu-Bo1, Lin Xiang2, YIN Fu-Wei3, and WANG Dong2,*

1Shandong Agricultural University / State Key Laboratory of Crop Biology, Tai’an 271018, Shandong, China;2College of Agronomy, Northwest A&F University, Yangling 712100, Shaanxi, China;3Tai’an City Agricultural Technology Extension Center, Tai’an 271000, Shandong, China

In order to explore the effect of potassium fertilizer application on the yield and nitrogen use efficiency of winter wheat in different stages, and to determine the high-yield and efficient potassium fertilizer operation plan for winter wheat under the condition of nitrogen reduction, the high-yield and strong-gluten winter wheat variety Gaoyou 5766 was selected as the test materials in this experiment. During the growing season, a two-factor randomized block design was used to set three nitrogen application levels [conventional nitrogen application rate (240 kg hm–2, N1), nitrogen application rate reduced by 20% (192 kg hm–2, N2), and nitrogen application rate reduced by 40% (144 kg hm–2, N3)] and two potassium fertilizer application schemes [all potassium fertilizers applied at the sowing stage (K1) and potassium fertilizer applied in stages (50% was applied at the sowing stage and 50% was applied at the jointing stage, K2)]. The results showed that under the same potassium fertilizer application scheme, the grain yield of N2 treatment was not significantly different from that of N1 treatment, and the grain yield of N3 treatment was significantly lower than that of N1 treatment, with a decrease of 9.0%–11.6%. Under the same nitrogen application rate, potassium application by stages could significantly improve grain yield and nitrogen use efficiency of winter wheat. Compared with K1 treatment, K2 treatment significantly inhibited the leaching of nitrate nitrogen into deep soil layers, increased nitrogen accumulation in winter wheat plants, and increased flag leaf photosynthetic rate and nitrate reductase activity, grain filling rate, the number of grains per spike, and 1000-grain weight. Grain yield and nitrogen use efficiency increased by 21.7% and 20.2% under the conventional nitrogen application rate, by 26.9% and 26.2% under the N2 level, and by 25.2% and 21.1% under the N3 level, respectively. The grain yield, nitrogen uptake efficiency, nitrogen use efficiency, and nitrogen partial productivity of N3K2 treatment were significantly higher than those of N1K1 treatment. The above results showed that potassium application in stages could greatly improve the grain yield and nitrogen use efficiency of winter wheat under different nitrogen application rates. Using the nitrogen application rate of 192 kg hm–2combined with potassium application in stages, the grain yield and nitrogen uptake efficiency of winter wheat were the highest, and the nitrogen use efficiency and nitrogen partial productivity also reached a high level. It is a high-yield and efficient nitrogen-potassium fertilizer application scheme.

winter wheat; nitrogen reduction; potassium application by stages; grain yield; nitrogen use efficiency

10.3724/SP.J.1006.2023.21013

本研究由山東省重點(diǎn)研發(fā)計(jì)劃項(xiàng)目(LJNY202010)和陜西省重點(diǎn)研發(fā)計(jì)劃項(xiàng)目(2021ZDLNY01-05)資助。

This study was supported by the Key Research and Development Program Project of Shandong Province (LJNY202010) and the Key Research and Development Program Project of Shaanxi Province (2021ZDLNY01-05).

王東, E-mail: wangd@nwafu.edu.cn

E-mail: 492754758@qq.com

2022-02-18;

2022-06-07;

2022-07-11.

URL: https://kns.cnki.net/kcms/detail/11.1809.S.20220708.1753.005.html

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).