輪作模式與周期對黃土高原旱地小麥產量、養分吸收和土壤肥力的影響

蔡 艷, 郝明德

(1四川農業大學資源環境學院，四川成都 611130； 2 西北農林科技大學資源環境學院，陜西楊凌 712100；3 西北農林科技大學水土保持研究所，陜西楊凌 712100)

輪作模式與周期對黃土高原旱地小麥產量、養分吸收和土壤肥力的影響

蔡 艷1, 2, 郝明德2, 3*

(1四川農業大學資源環境學院，四川成都 611130； 2 西北農林科技大學資源環境學院，陜西楊凌 712100；3 西北農林科技大學水土保持研究所，陜西楊凌 712100)

輪作； 黃土高原； 小麥； 養分吸收； 礦質營養； 土壤肥力

糧草輪作和糧豆輪作是黃土高原旱地區常見種植方式。黃土高原旱地區實行糧草輪作或糧豆輪作可提高土壤剖面供氮能力[3-4]，增加有效磷和有效鐵、錳含量[5-6]，蔗糖酶、脲酶、堿性磷酸酶和蛋白酶活性也有不同程度的提高[7]。本研究在黃土高原旱地長期定位試驗基礎上，研究糧草長周期輪作、糧草短周期輪作、糧豆輪作對小麥產量、養分吸收和土壤肥力的影響，以期為該地區優化種植制度提高糧食產量，增加糧食作物礦質養分含量，實現土壤養分資源平衡管理及可持續利用提供依據。

1 材料與方法

1.1 試驗地概況

1.2 試驗材料

試驗土壤為粘化黑壚土，母質是深厚的中壤質馬蘭黃土，全剖面土質均勻疏松，通透性好，肥力中等。試驗開始時耕層土壤有機質10.5 g/kg，全氮0.800 g/kg，堿解氮37.0 mg/kg，全磷0.659 g/kg，有效磷3.00 mg/kg，速效鉀129 mg/kg，pH(H2O) 8.24。供試小麥品種為長武134，田間管理同大田。

1.3 試驗設計

長期定位試驗于1984年布置，設糧草長周期輪作、糧草短周期輪作和糧豆輪作3種輪作制度，以小麥連作處理(CK)作為對照，共8個處理。為保證同一年度取到不同茬口年限小麥及土壤樣品，糧草長周期輪作設以下3組種植方式：小麥→小麥→苜?！俎！俎！俎！R鈴薯→小麥(WAT1)； 小麥→苜?！俎！俎！俎！R鈴薯→小麥→小麥(WAT2)； 苜?！俎！俎！俎！R鈴薯→ 小麥→小麥→小麥(WAT3)。糧草短周期輪作設以下2組種植方式：小麥+紅豆草→紅豆草→小麥(WST1)； 紅豆草→小麥→小麥+紅豆草(WST2)。糧豆輪作設以下2組種植方式：小麥+糜子→豌豆→小麥(WPT1)； 豌豆→小麥→小麥+糜子(WPT2)。

小區長10.26 m、 寬6.5 m，面積66.69 m2。每個處理3次重復，隨機區組排列。各處理年施肥量為N 120 kg/hm2，P2O560 kg/hm2，所施氮肥為尿素，磷肥為過磷酸鈣，皆于作物播前將肥料撒施地表后耕翻入土。

1.4 樣品采集與分析

植物樣品養分含量用H2SO4-H2O2消煮后，凱氏定氮法測氮，鉬藍比色法測磷，火焰光度法測鉀，原子吸收法測鐵、錳、銅、鋅[8]。土壤樣品測定方法：有機質采用重鉻酸鉀外加熱法，全氮采用凱氏定氮法，全磷采用酸融—鉬銻抗比色法，堿解氮采用堿解擴散法，有效磷采用Olsen法，速效鉀采用火焰光度法測定[8]。

1.5 數據處理方法

數據采用軟件Excel和DPS 6.55進行處理和統計分析。方差分析采用單因素方差分析(ANOVA)，最小差數法(LSD法)進行多重比較。

養分收獲指數(%)= 籽粒養分吸收量 × 100/植株養分吸收總量

2 結果與分析

2.1 長期輪作對黃土高原旱地小麥產量的影響

表1 長期輪作下黃土高原旱地的小麥產量Table 1 Wheat yield in the long-term rotation in Loess Plateau

注(Note): 同列數據后不同字母表示處理間差異達到5%顯著水平 Values followed by different letters in the same column are significantly different at the 5% level.

2.2 長期輪作對黃土高原旱地小麥養分吸收的影響

2.2.1 長期輪作對小麥大量元素吸收的影響 輪作可促進旱地小麥對氮磷鉀養分的吸收，且對氮鉀吸收的影響程度高于磷。糧草長周期輪作小麥吸氮量最高，平均值為142.6 kg/hm2，比連作小麥高29.28%。糧豆輪作小麥吸鉀量最高，平均值為94.9 kg/hm2，比連作小麥高29.47%(表2)。

苜蓿茬后種植小麥，促進了小麥對土壤氮鉀的吸收，且第三年小麥 > 第二年 >第一年(表2)，但苜蓿茬后第一年小麥吸磷量低于連作小麥，生產上應注意合理施用磷肥。紅豆草茬后小麥對氮鉀的吸收量均高于連作小麥，WST1小麥吸氮量稍高于WST2，WST2小麥吸磷量和吸鉀量稍高于WST1，但處理之間差異均不顯著。豌豆茬后小麥各部位對氮磷鉀的吸收量均表現為WPT2 > WPT1，且種植豌豆后第二年小麥籽粒和植株吸氮量，及秸稈和植株吸鉀量均顯著高于連作小麥。

表2 長期輪作對黃土高原旱地小麥大量元素吸收的影響Table 2 Effect of the long-term rotation on wheat uptakes of macronutrients in dryland fields in the Loess Plateau

注(Note): 同列數據后不同字母表示處理間差異達到5%顯著水平 Values followed by different letters in the same column are significantly different at the 5% level.

2.2.2 長期輪作對小麥微量元素吸收的影響 輪作系統和茬口年限對旱地小麥籽粒吸鐵量無顯著影響，對小麥秸稈吸鐵量和植株吸鐵量有顯著影響(圖1A)。糧草長周期輪作中，小麥各部位吸鐵量表現為WAT3 > WAT2 > WAT1，且WAT3顯著高于CK和WAT1。糧草短周期輪作中，小麥各部位吸鐵量表現為WST1 > WST2，WST1小麥秸稈和植物吸鐵量分別比CK高54.74%和50.82%，差異顯著。糧豆輪作中，WPT2小麥秸稈吸鐵量顯著高于WPT1和CK。

糧草輪作對旱地小麥各部位吸錳量影響程度較小，糧草長周期輪作、糧草短周期輪作中各茬小麥籽粒、秸稈和植物吸錳量與連作小麥均無顯著差異(圖1B)。糧豆輪作對旱地小麥吸錳量影響較大，WPT2小麥籽粒、秸稈和植株吸錳量分別比CK高27.56%、53.21%和44.26%，顯著高于CK，且其秸稈和植株吸錳量顯著高于糧草輪作系統中各茬小麥。

糧草長周期輪作及茬口年限對旱地小麥吸銅量影響較大，其他兩種輪作系統影響較小(圖1C)。采取糧草長周期輪作后，WAT1小麥吸銅量與CK相近，WAT2小麥吸銅量大幅增加，顯著高于CK，WAT3小麥籽粒吸銅量仍顯著高于CK。采取糧草短周期輪作后，WST2秸稈和植株吸銅量比WAT1高約10%，但均與CK差異不顯著。糧豆輪作與連作相比，小麥吸銅量無顯著差異。

從圖1D可以看出，種植制度和茬口年限對旱地小麥吸鋅量的影響與銅相似。苜蓿茬后年限越長，小麥對鋅的吸收量越高，WAT3籽粒、植株吸鋅量均顯著高于CK。紅豆草茬后小麥吸鋅規律與此相反，WST2小麥籽粒、秸稈、植株吸鋅量均低于WST1，但兩者差異不顯著。豌豆茬后年限越長，小麥各部位對鋅的吸收量稍有增加，但兩者差異不顯著。

圖1 長期輪作對黃土高原旱地小麥微量元素吸收的影響Fig.1 Effect of the long-term rotation on wheat uptake of micronutrients in dryland fields in the Loess Plateau[注(Note)： 同一部位柱狀圖上不同字母表示處理間差異達到5%顯著水平 Different letters above the bar in the same parts mean significant difference at the 5% level.]

表3 長期輪作對黃土高原旱地小麥養分收獲指數的影響(%)Table 3 Effect of the long-term rotation on wheat harvest indexes of nutrients in dryland fields in the Loess Plateau

注(Note): 同列數據后不同字母表示處理間差異達到5%顯著水平 Values followed by different letters in the same column are significantly different at the 5% level.

各種植體系中，茬口年限對小麥微量元素收獲指數影響方向和程度均不相同，種植系統間也有一定差異。糧草長周期輪作中，3年間小麥鐵收獲指數差異不顯著，但WAT3顯著低于CK；WAT3小麥錳、銅、鋅收獲指數顯著高于CK，且銅收獲指數顯著高于WAT1和WAT2。糧草短周期輪作中，WST1鐵收獲指數顯著低于CK，其它與之相當；WST2鐵、錳收獲指數顯著高于WST1，但銅收獲指數顯著低于WST1。糧豆輪作中，WPT1鐵、錳收獲指數顯著高于WPT2，兩者銅收獲指數均顯著高于CK；WPT2鋅收獲指數顯著高于CK。

2.3 長期輪作對黃土高原小麥地耕層土壤肥力性質的影響

表4 長期輪作黃土高原旱地區小麥地耕層土壤肥力性質Table 4 Effect of the long-term rotation on soil fertility of wheat topsoil in dryland fields in the Loess Plateau

3 討論

3.1 輪作對土壤肥力和小麥產量的影響

3.2 輪作對小麥養分吸收的影響

小麥是中國和全球大多數人主要的食物和礦質元素來源，其礦質養分含量和分布對小麥植株生長發育和人體健康的影響已受到廣泛關注[23-24]。小麥礦質養分含量和分布狀況受遺傳基因[25-26]和土壤管理[1,14,27-28]共同影響。

黃土高原旱地區實行糧草輪作后，由于豆科植物需磷量高[23]，土壤供磷強度減少約30%，導致種植苜蓿和紅豆草后1年小麥吸磷量低于連作小麥。同時由于豆科植物對土壤氮素的富集作用[15-16]和鉀素的活化作用[29]，輪作條件下小麥氮鉀吸收量高于連作小麥。楊寧等[28]認為，旱地小麥和豆科作物輪作增產的重要原因是減少莖葉鉀素在花后的轉移，本研究也發現，小麥與苜蓿、紅豆草及豌豆輪作后，鉀素收獲指數普遍下降，產量卻不同程度增加。

許多醫學專家認為當今人類疾病90%以上與微量元素有關，而糧食作物籽粒中微量元素，特別是鋅、鐵含量較低，生物有效性差是全世界普遍存在的問題[30]。黃土高原旱地小麥籽粒鐵、錳、銅、鋅含量比全國平均水平分別低7.7%、9.2%、42.9%和6.3%[14]，通過一定措施提高小麥籽粒對微量元素的吸收顯得尤為迫切。本研究表明，輪作使旱地小麥對微量元素的吸收量增加或差異不顯著，各種植系統及小麥茬口年限對4種微量元素影響不一，這與豆科植物對土壤微量元素形態和有效性的影響不盡相同有很大關系[6,31]。總的來說，黃土高原旱地區實行糧草長周期輪作有利于促進小麥籽粒對鐵、銅、鋅的吸收，且苜蓿茬后3年小麥 > 2年小麥 > 1年小麥。糧豆輪作可促進小麥籽粒對錳的吸收，且豌豆茬后2年小麥 > 1年小麥。糧草短周期輪作對小麥籽粒微量元素累積作用不明顯。因此，在黃土高原旱地促進小麥對微量元素吸收的較優種植制度為糧草長周期輪作或糧豆輪作。

4 結論

1)輪作可不同程度增加旱地小麥產量。糧草短周期輪作有利于提高小麥籽粒產量，糧草長周期輪作有利于提高小麥秸稈產量和生物產量。種植豆科牧草后2年小麥產量高于1年小麥，至苜蓿茬后3年小麥產量逐漸降低，輪作優勢逐漸減弱。糧豆輪作小麥產量有增加趨勢，但不顯著。

2)輪作可提高旱地小麥對氮鉀的吸收，糧豆輪作效果最明顯；輪作對旱地小麥吸磷無顯著影響。輪作及茬口年限對小麥大量元素收獲指數影響較小。

3)糧草長周期輪作可促進旱地小麥對鐵、銅、鋅的吸收，且苜蓿茬后3年小麥 > 2年小麥 > 1年小麥。糧草短周期輪作可促進小麥對鐵的吸收，且紅豆草茬后1年小麥 > 2年小麥。糧豆輪作可促進小麥對鐵、錳的吸收，且豌豆茬后2年小麥 > 1年小麥。糧草輪作鐵收獲指數低于連作小麥，糧豆輪作則有利銅向籽粒轉移。

4)輪作可提高土壤氮素供應潛力和供應強度，且糧草短周期作用最明顯。糧草輪作減少了土壤磷的累積和有效磷的供應強度，糧豆輪作則剛好相反。

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Effects of rotation model and period on wheat yield,nutrient uptake and soil fertility in the Loess Plateau

CAI Yan1, 2, HAO Ming-de2, 3*

(1CollegeofResourcesandEnvironment,SichuanAgriculturalUniversity,Chengdu611130,China;2CollegeofNaturalResourcesandEnvironment,NorthwestA&FUniversity,Yangling,Shaanxi712100,China;3InstituteofSoilandWaterConservation,NorthwestA&FUniversity,Yangling,Shaanxi712100,China)

【Objectives】Rotations of wheat-alfalfa, wheat-sainfoin and wheat-pea are common cropping systems in the Loess Plateau, northwest China. In this paper, the impacts of different cropping systems on the wheat yields, nutrient uptake and soil fertility were studied using a long-term experiment, in order to compare and recommend the optimum cropping system in this area.【Methods】 The long-term experiment was established in 1984. Eight treatments with triplicates were designed: continuous cropping of wheat(CK), three long-period rotations of wheat-alfalfa treatments: wheat→wheat→alfalfa→alfalfa→alfalfa→ alfalfa→potato→wheat (WAT1), wheat→alfalfa→alfalfa→alfalfa→alfalfa→potato→wheat→wheat (WAT2), and alfalfa→ alfalfa→alfalfa→alfalfa→potato→wheat→wheat→wheat (WAT3); two short-period rotations of wheat-sainfoin: wheat and sainfoin→sainfoin→wheat (WST1), sainfoin→wheat→wheat and sainfoin (WST2); two wheat-pea rotations: wheat and millet →pea→wheat (WPT1), pea→wheat→wheat and millet (WPT2). Plant and soil samples were collected after wheat harvest in June, 2004. Wheat yields, grain and straw nutrient contents and soil fertility were determined. 【Results】 The wheat grain yields in the rotation were 1.47% to 29.66% higher than the control, and the straw biomass were 2.17% to 29.77% higher. The increases were more obvious in wheat-alfalfa rotation and wheat-sainfoin rotation systems. The second year wheat cropping yields after alfalfa or sainfoin were higher than those in the first year, the rotation advantage became weaken in the third year. The long-period rotation of wheat-alfalfa favored absorption of N, K, Fe, Cu and Zn in wheat, and the order was WAT3 > WAT2 > WAT1. The short-period rotation of wheat-sainfoin favored absorption of N, K and Fe in wheat, and WST1 was slightly higher than WST2. The wheat-pea rotation favored absorption of N, K, Fe and Mn in wheat, and WPT2 > WPT1. The rotation model and year after rotated crops affected more on the harvest indexes of microelements than on those of macro-nutrients. The wheat-pea rotation was conducive to the transfer of N, P and Cu to wheat grain. The wheat K harvest indexes of the three rotation systems were lower than those of the continuous cropping of wheat, and the Fe harvest indexes of the wheat-alfalfa rotation and wheat-sainfoin rotation were lower than those of the continuous cropping of wheat. Through rotation, soil total N was increased by 11.54%-20.51%, alkali-hydrolysable N increased by 9.66%-21.56%. The wheat-sainfoin rotation had obvious positive effect on soil organic matter, total N and available K, but negative on soil available P (decreased by 23.97%). The wheat-pea rotation showed obvious positive effect on soil P accumulation with a increase of 45.52% compared to control.【Conclusions】 The rotation mode of 2 to 4 years successive sainfoin→two years continuing wheat is proven to be the optimum rotation mode in the Loess Plateau, in case of attention be paid on increasing phosphate fertilizer application.

crop rotation; Loess Plateau; wheat; nutrient uptake; mineral nutrition; soil fertility

2014-03-17 接受日期： 2014-12-03 網絡出版日期： 2015-05-08

國家科技支撐計劃重大項目(2011BAD31B01)；寧夏農業綜合開發科技推廣項目(NTKJ-2013-03-1)資助。

蔡艷(1976—)，女，四川達縣人，博士研究生，主要從事土壤與植物營養的研究。E-mail: caiyya@126.com * 通信作者 E-mail：mdhao@ms.iswc.ac.cn

S344.3

A

1008-505X(2015)04-0864-09