轮作模式与周期对黄土高原旱地小麦产量、养分吸收和土壤肥力的影响

蔡 艳, 郝明德

(1四川农业大学资源环境学院，四川成都 611130； 2 西北农林科技大学资源环境学院，陕西杨凌 712100；3 西北农林科技大学水土保持研究所，陕西杨凌 712100)

轮作模式与周期对黄土高原旱地小麦产量、养分吸收和土壤肥力的影响

蔡 艳1, 2, 郝明德2, 3*

(1四川农业大学资源环境学院，四川成都 611130； 2 西北农林科技大学资源环境学院，陕西杨凌 712100；3 西北农林科技大学水土保持研究所，陕西杨凌 712100)

轮作； 黄土高原； 小麦； 养分吸收； 矿质营养； 土壤肥力

粮草轮作和粮豆轮作是黄土高原旱地区常见种植方式。黄土高原旱地区实行粮草轮作或粮豆轮作可提高土壤剖面供氮能力[3-4]，增加有效磷和有效铁、锰含量[5-6]，蔗糖酶、脲酶、碱性磷酸酶和蛋白酶活性也有不同程度的提高[7]。本研究在黄土高原旱地长期定位试验基础上，研究粮草长周期轮作、粮草短周期轮作、粮豆轮作对小麦产量、养分吸收和土壤肥力的影响，以期为该地区优化种植制度提高粮食产量，增加粮食作物矿质养分含量，实现土壤养分资源平衡管理及可持续利用提供依据。

1 材料与方法

1.1 试验地概况

1.2 试验材料

试验土壤为粘化黑垆土，母质是深厚的中壤质马兰黄土，全剖面土质均匀疏松，通透性好，肥力中等。试验开始时耕层土壤有机质10.5 g/kg，全氮0.800 g/kg，碱解氮37.0 mg/kg，全磷0.659 g/kg，有效磷3.00 mg/kg，速效钾129 mg/kg，pH(H2O) 8.24。供试小麦品种为长武134，田间管理同大田。

1.3 试验设计

长期定位试验于1984年布置，设粮草长周期轮作、粮草短周期轮作和粮豆轮作3种轮作制度，以小麦连作处理(CK)作为对照，共8个处理。为保证同一年度取到不同茬口年限小麦及土壤样品，粮草长周期轮作设以下3组种植方式：小麦→小麦→苜蓿→苜蓿→苜蓿→苜蓿→马铃薯→小麦(WAT1)； 小麦→苜蓿→苜蓿→苜蓿→苜蓿→马铃薯→小麦→小麦(WAT2)； 苜蓿→苜蓿→苜蓿→苜蓿→马铃薯→ 小麦→小麦→小麦(WAT3)。粮草短周期轮作设以下2组种植方式：小麦+红豆草→红豆草→小麦(WST1)； 红豆草→小麦→小麦+红豆草(WST2)。粮豆轮作设以下2组种植方式：小麦+糜子→豌豆→小麦(WPT1)； 豌豆→小麦→小麦+糜子(WPT2)。

小区长10.26 m、 宽6.5 m，面积66.69 m2。每个处理3次重复，随机区组排列。各处理年施肥量为N 120 kg/hm2，P2O560 kg/hm2，所施氮肥为尿素，磷肥为过磷酸钙，皆于作物播前将肥料撒施地表后耕翻入土。

1.4 样品采集与分析

植物样品养分含量用H2SO4-H2O2消煮后，凯氏定氮法测氮，钼蓝比色法测磷，火焰光度法测钾，原子吸收法测铁、锰、铜、锌[8]。土壤样品测定方法：有机质采用重铬酸钾外加热法，全氮采用凯氏定氮法，全磷采用酸融—钼锑抗比色法，碱解氮采用碱解扩散法，有效磷采用Olsen法，速效钾采用火焰光度法测定[8]。

1.5 数据处理方法

数据采用软件Excel和DPS 6.55进行处理和统计分析。方差分析采用单因素方差分析(ANOVA)，最小差数法(LSD法)进行多重比较。

养分收获指数(%)= 籽粒养分吸收量 × 100/植株养分吸收总量

2 结果与分析

2.1 长期轮作对黄土高原旱地小麦产量的影响

表1 长期轮作下黄土高原旱地的小麦产量Table 1 Wheat yield in the long-term rotation in Loess Plateau

注(Note): 同列数据后不同字母表示处理间差异达到5%显著水平 Values followed by different letters in the same column are significantly different at the 5% level.

2.2 长期轮作对黄土高原旱地小麦养分吸收的影响

2.2.1 长期轮作对小麦大量元素吸收的影响 轮作可促进旱地小麦对氮磷钾养分的吸收，且对氮钾吸收的影响程度高于磷。粮草长周期轮作小麦吸氮量最高，平均值为142.6 kg/hm2，比连作小麦高29.28%。粮豆轮作小麦吸钾量最高，平均值为94.9 kg/hm2，比连作小麦高29.47%(表2)。

苜蓿茬后种植小麦，促进了小麦对土壤氮钾的吸收，且第三年小麦 > 第二年 >第一年(表2)，但苜蓿茬后第一年小麦吸磷量低于连作小麦，生产上应注意合理施用磷肥。红豆草茬后小麦对氮钾的吸收量均高于连作小麦，WST1小麦吸氮量稍高于WST2，WST2小麦吸磷量和吸钾量稍高于WST1，但处理之间差异均不显著。豌豆茬后小麦各部位对氮磷钾的吸收量均表现为WPT2 > WPT1，且种植豌豆后第二年小麦籽粒和植株吸氮量，及秸秆和植株吸钾量均显著高于连作小麦。

表2 长期轮作对黄土高原旱地小麦大量元素吸收的影响Table 2 Effect of the long-term rotation on wheat uptakes of macronutrients in dryland fields in the Loess Plateau

注(Note): 同列数据后不同字母表示处理间差异达到5%显著水平 Values followed by different letters in the same column are significantly different at the 5% level.

2.2.2 长期轮作对小麦微量元素吸收的影响 轮作系统和茬口年限对旱地小麦籽粒吸铁量无显著影响，对小麦秸秆吸铁量和植株吸铁量有显著影响(图1A)。粮草长周期轮作中，小麦各部位吸铁量表现为WAT3 > WAT2 > WAT1，且WAT3显著高于CK和WAT1。粮草短周期轮作中，小麦各部位吸铁量表现为WST1 > WST2，WST1小麦秸秆和植物吸铁量分别比CK高54.74%和50.82%，差异显著。粮豆轮作中，WPT2小麦秸秆吸铁量显著高于WPT1和CK。

粮草轮作对旱地小麦各部位吸锰量影响程度较小，粮草长周期轮作、粮草短周期轮作中各茬小麦籽粒、秸秆和植物吸锰量与连作小麦均无显著差异(图1B)。粮豆轮作对旱地小麦吸锰量影响较大，WPT2小麦籽粒、秸秆和植株吸锰量分别比CK高27.56%、53.21%和44.26%，显著高于CK，且其秸秆和植株吸锰量显著高于粮草轮作系统中各茬小麦。

粮草长周期轮作及茬口年限对旱地小麦吸铜量影响较大，其他两种轮作系统影响较小(图1C)。采取粮草长周期轮作后，WAT1小麦吸铜量与CK相近，WAT2小麦吸铜量大幅增加，显著高于CK，WAT3小麦籽粒吸铜量仍显著高于CK。采取粮草短周期轮作后，WST2秸秆和植株吸铜量比WAT1高约10%，但均与CK差异不显著。粮豆轮作与连作相比，小麦吸铜量无显著差异。

从图1D可以看出，种植制度和茬口年限对旱地小麦吸锌量的影响与铜相似。苜蓿茬后年限越长，小麦对锌的吸收量越高，WAT3籽粒、植株吸锌量均显著高于CK。红豆草茬后小麦吸锌规律与此相反，WST2小麦籽粒、秸秆、植株吸锌量均低于WST1，但两者差异不显著。豌豆茬后年限越长，小麦各部位对锌的吸收量稍有增加，但两者差异不显著。

图1 长期轮作对黄土高原旱地小麦微量元素吸收的影响Fig.1 Effect of the long-term rotation on wheat uptake of micronutrients in dryland fields in the Loess Plateau[注(Note)： 同一部位柱状图上不同字母表示处理间差异达到5%显著水平 Different letters above the bar in the same parts mean significant difference at the 5% level.]

表3 长期轮作对黄土高原旱地小麦养分收获指数的影响(%)Table 3 Effect of the long-term rotation on wheat harvest indexes of nutrients in dryland fields in the Loess Plateau

注(Note): 同列数据后不同字母表示处理间差异达到5%显著水平 Values followed by different letters in the same column are significantly different at the 5% level.

各种植体系中，茬口年限对小麦微量元素收获指数影响方向和程度均不相同，种植系统间也有一定差异。粮草长周期轮作中，3年间小麦铁收获指数差异不显著，但WAT3显著低于CK；WAT3小麦锰、铜、锌收获指数显著高于CK，且铜收获指数显著高于WAT1和WAT2。粮草短周期轮作中，WST1铁收获指数显著低于CK，其它与之相当；WST2铁、锰收获指数显著高于WST1，但铜收获指数显著低于WST1。粮豆轮作中，WPT1铁、锰收获指数显著高于WPT2，两者铜收获指数均显著高于CK；WPT2锌收获指数显著高于CK。

2.3 长期轮作对黄土高原小麦地耕层土壤肥力性质的影响

表4 长期轮作黄土高原旱地区小麦地耕层土壤肥力性质Table 4 Effect of the long-term rotation on soil fertility of wheat topsoil in dryland fields in the Loess Plateau

3 讨论

3.1 轮作对土壤肥力和小麦产量的影响

3.2 轮作对小麦养分吸收的影响

小麦是中国和全球大多数人主要的食物和矿质元素来源，其矿质养分含量和分布对小麦植株生长发育和人体健康的影响已受到广泛关注[23-24]。小麦矿质养分含量和分布状况受遗传基因[25-26]和土壤管理[1,14,27-28]共同影响。

黄土高原旱地区实行粮草轮作后，由于豆科植物需磷量高[23]，土壤供磷强度减少约30%，导致种植苜蓿和红豆草后1年小麦吸磷量低于连作小麦。同时由于豆科植物对土壤氮素的富集作用[15-16]和钾素的活化作用[29]，轮作条件下小麦氮钾吸收量高于连作小麦。杨宁等[28]认为，旱地小麦和豆科作物轮作增产的重要原因是减少茎叶钾素在花后的转移，本研究也发现，小麦与苜蓿、红豆草及豌豆轮作后，钾素收获指数普遍下降，产量却不同程度增加。

许多医学专家认为当今人类疾病90%以上与微量元素有关，而粮食作物籽粒中微量元素，特别是锌、铁含量较低，生物有效性差是全世界普遍存在的问题[30]。黄土高原旱地小麦籽粒铁、锰、铜、锌含量比全国平均水平分别低7.7%、9.2%、42.9%和6.3%[14]，通过一定措施提高小麦籽粒对微量元素的吸收显得尤为迫切。本研究表明，轮作使旱地小麦对微量元素的吸收量增加或差异不显著，各种植系统及小麦茬口年限对4种微量元素影响不一，这与豆科植物对土壤微量元素形态和有效性的影响不尽相同有很大关系[6,31]。总的来说，黄土高原旱地区实行粮草长周期轮作有利于促进小麦籽粒对铁、铜、锌的吸收，且苜蓿茬后3年小麦 > 2年小麦 > 1年小麦。粮豆轮作可促进小麦籽粒对锰的吸收，且豌豆茬后2年小麦 > 1年小麦。粮草短周期轮作对小麦籽粒微量元素累积作用不明显。因此，在黄土高原旱地促进小麦对微量元素吸收的较优种植制度为粮草长周期轮作或粮豆轮作。

4 结论

1)轮作可不同程度增加旱地小麦产量。粮草短周期轮作有利于提高小麦籽粒产量，粮草长周期轮作有利于提高小麦秸秆产量和生物产量。种植豆科牧草后2年小麦产量高于1年小麦，至苜蓿茬后3年小麦产量逐渐降低，轮作优势逐渐减弱。粮豆轮作小麦产量有增加趋势，但不显著。

2)轮作可提高旱地小麦对氮钾的吸收，粮豆轮作效果最明显；轮作对旱地小麦吸磷无显著影响。轮作及茬口年限对小麦大量元素收获指数影响较小。

3)粮草长周期轮作可促进旱地小麦对铁、铜、锌的吸收，且苜蓿茬后3年小麦 > 2年小麦 > 1年小麦。粮草短周期轮作可促进小麦对铁的吸收，且红豆草茬后1年小麦 > 2年小麦。粮豆轮作可促进小麦对铁、锰的吸收，且豌豆茬后2年小麦 > 1年小麦。粮草轮作铁收获指数低于连作小麦，粮豆轮作则有利铜向籽粒转移。

4)轮作可提高土壤氮素供应潜力和供应强度，且粮草短周期作用最明显。粮草轮作减少了土壤磷的累积和有效磷的供应强度，粮豆轮作则刚好相反。

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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 网络出版日期： 2015-05-08

国家科技支撑计划重大项目(2011BAD31B01)；宁夏农业综合开发科技推广项目(NTKJ-2013-03-1)资助。

蔡艳(1976—)，女，四川达县人，博士研究生，主要从事土壤与植物营养的研究。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