渭北旱塬豆科绿肥提高冬小麦籽粒锌的效应与影响因素研究

The Increasing Effect and Influencing Factors of Leguminous Green Manure on Wheat Grain Zn in Weibei Highland

【目的】针对渭北旱塬石灰性土壤有效锌含量低,小麦籽粒锌含量不高的问题,研究不同豆科绿肥轮作对小麦籽粒锌的作用,揭示其提高小麦籽粒锌含量的影响因素,为改善居民锌摄入水平提供思路及实践依据。【方法】2016—2017年在永寿和长武两地开展田间试验,完全随机区组设计。永寿试验地处理为休闲-小麦、黑麦豆-小麦和绿豆-小麦3种处理;长武试验地为休闲-小麦、怀豆-小麦和绿豆-小麦3种处理。采集永寿、长武两地的绿肥、小麦和土壤样品进行分析。【结果】与休闲相比,永寿各豆科绿肥—小麦轮作的小麦各器官生物量显著降低了19.2%—38.3%;长武各豆科绿肥—小麦轮作显著减少了小麦茎叶、颖壳生物量,降幅为19.9%—33.2%。永寿黑麦豆—小麦和长武怀豆—小麦轮作较休闲显著提高了小麦籽粒锌含量,分别增加了14.2%和18.6%。黑麦豆—小麦、怀豆—小麦轮作对小麦的增锌作用一定程度上补偿了减产对小麦锌累积量的影响,长武怀豆—小麦轮作的小麦各器官及地上部锌累积量与休闲无显著差异。小麦籽粒锌含量与豆科绿肥的锌吸收量呈显著正相关关系,豆科绿肥锌吸收量每增加1.0 g·hm-2,小麦籽粒锌含量增加0.23 mg·kg-1。黑麦豆、怀豆的锌、氮吸收量相对较高,C/N较绿豆分别低了18.6%和20.4%。黑麦豆—小麦、怀豆—小麦轮作较休闲在小麦收获期显著提高了土壤硝态氮含量,增幅分别为36.7%和69.1%。豆科绿肥—小麦轮作在小麦生长过程中对土壤DTPA-Zn含量基本无显著影响。【结论】黑麦豆、怀豆两种豆科绿肥因自身比较高的锌、氮吸收量以及较低的C/N,可显著提高后茬小麦籽粒锌含量。同时绿肥自身富集锌的能力可作为筛选小麦适宜增锌绿肥品种的依据。总之,豆科绿肥—小麦轮作模式是提高小麦籽粒锌含量,改善居民膳食锌摄入的有效生物强化手段。

【Objective】Weibei Highland is one of important winter wheat production areas in northwest China, where Zn concentration in wheat grain are generally low due to soil bioavailable Zn deficiency. So we decided to study leguminous green manure-wheat rotations whether could improve wheat Zn concentration in different regions of Weibei Highland, and to explore the factors affecting wheat Zn biofortification by leguminous green manure-wheat rotations.【Method】Two field experiments were carried out during 2016-2017 cropping seasons in Yongshou and Changwu with a completely randomized block design. There were three main treatments： Summer fallow-wheat（FW） as CK, black kidney bean-wheat（KW） and mung bean-wheat（MW） in Yongshou; Summer fallow-wheat（FW） as CK, huai bean-wheat（HW） and mung bean-wheat（MW） in Changwu. Plant samples of legumes, wheat and 0-20 cm soil samples at different wheat growing stages were collected for chemical analysis. 【Result】 In Yongshou, compare with FW, wheat grain yield and biomass were decreased by 19.2%-38.3% under leguminous green manure-wheat rotations,. In Changwu, leguminous green manure-wheat rotations did not significantly reduce wheat grain yield, but reduced wheat glumes and straw biomass by 19.9%-33.2%. KW rotation in Yongshou and HW rotation in Changwu significantly increased grain Zn concentration by 14.2% and 18.6%, respectively, which partially compensated the potential reduction of wheat grain Zn export and aboveground shoot Zn uptake by increasing Zn concentrations of wheat grain and straw Zn concentration due to the shrink of wheat yield and biomass. There was no significant difference of wheat Zn uptake between HW and FW treatments in Changwu. Wheat grain Zn concentration was positively correlated with leguminous manure shoot Zn uptake. Wheat grain Zn concentration increases 0.23 mg·kg^-1 when green manure shoot Zn uptake increases 1.0 g·hm^-2, correspondingly. Besides, the Zn, N content of black kidney bean and huai bean were both higher than that of mung bean. Moreover, compared with mung bean, C/N of black kidney bean and huai bean were lower by 18.6% and 20.4%, respectively. At wheat maturity stage, soil nitrate of KW and HW rotations were both higher than that of FW by 36.7% and 69.1%, respectively. Leguminous green manure-wheat rotations had rarely significant effect on soil DTPA-Zn concentration during the growth of wheat.【Conclusion】Relatively higher Zn and N content and lower in C/N of black kidney bean and huai bean made them more readily improved subsequently wheat Zn uptake and accumulation than that of mung bean. The positive correlation between wheat grain Zn concentration and leguminous green manure shoot Zn uptake could be the guidance for screening and optimizing green manure varieties for wheat Zn biofortification. Therefore, leguminous green manure-wheat rotations could be an effective biofortification method to enhance wheat Zn nutrition for residents which suffered from Zn deficiency.