长期施氮条件下小麦铁锰累积及其与土壤养分的关系

The Accumulation of Iron and Manganese in Wheat and Its Relationship with Soil Nutrients Under Long-Term Application of Nitrogen Fertilizer

【目的】研究长期施用氮肥条件下小麦铁锰吸收累积规律及其与土壤养分之间的关系,进一步探讨基于产量及小麦铁锰营养的氮肥调控策略,为合理优化氮肥施用和改善小麦营养品质提供科学依据。【方法】基于旱地冬小麦的氮肥长期定位试验,设置5个施氮水平0、80、160、240、320 kg·hm^(-2),研究不同氮水平条件下小麦籽粒铁锰含量及其与产量、铁锰吸收分配规律、土壤养分及各形态铁锰的关系。【结果】施氮显著提高了冬小麦产量、地上部铁含量、籽粒铁含量,降低了地上部和籽粒的锰含量。与对照相比,氮肥供应超过160 kg·hm^(-2)时,小麦产量及籽粒铁含量不再继续增加,分别保持在5857—6598 kg·hm^(-2)和40.2—42.2 mg·kg^(-1),而籽粒锰含量保持较低水平,为30.4—35.3 mg·kg^(-1)。氮肥施用显著降低了土壤pH,提高了土壤中铁、锰元素的松结有机态及铁元素的锰氧化物结合态比例,增加了土壤中铁、锰的生物有效性。相关分析结果表明,小麦籽粒铁含量与产量、生物量、收获指数、穗数、穗粒数、铁收获指数显著正相关,与籽粒锰含量显著负相关;与土壤锰氧化物结合态铁显著正相关;与残渣态铁显著负相关。小麦籽粒锰含量与产量、生物量、收获指数、穗数、穗粒数、籽粒吸铁量、铁收获指数显著负相关,与地上部吸锰量显著正相关;与土壤各种形态锰不相关。【结论】西北旱区石灰性土壤中长期施氮可提高土壤铁的有效性、促进小麦对铁的吸收及铁向籽粒的分配,进而提高籽粒铁含量;施氮虽然提高了土壤锰的有效性,但显著抑制了小麦对锰的吸收,最终导致小麦籽粒锰含量降低。此外,当供磷水平一致时,土壤长期缺乏氮素供应可能导致小麦籽粒铁含量较低,而锰含量过高。综合考虑产量、籽粒铁锰元素营养品质及环境经济效益,西北旱区石灰性土壤小麦氮肥施用量建议控制在160 kg·hm^(-2),过量施用氮肥无助于继续提高产量及品质。

【Objective】The objective of the study was to explore the uptake and distribution of iron(Fe)and manganese(Mn)under long-term application of nitrogen fertilizer and its relationship with soil nutrients,to seek the nitrogen fertilizer regulation strategy based on yield and wheat Fe and Mn nutrition,and to provide a new perspective for the optimization of nitrogen fertilizer application and improvement of wheat quality.【Method】Based on the long-term nitrogen fertilizer experiment of winter wheat in dryland,the concentration of Fe and Mn in wheat grains,and their relationship with wheat grain yield,the uptake and distribution of Fe and Mn in wheat and soil nutrients were analyzed under nitrogen application rates of 0,80,160,240,and 320 kg·hm^(-2),respectively.【Result】Compared with the control,the application of nitrogen improved wheat grain yield,shoot Fe concentration,nutrient Fe and Fe concentration in grains,but decreased Mn concentration in wheat shoot and grains.When the nitrogen application was higher than 160 kg·hm^(-2),no differences among treatments were found in the grain yield(5857-6598 kg·hm^(-2))and grain Fe concentration(40.2-42.2 mg·kg^(-1)),and the Mn concentration in grains remained at a lower level(30.4-35.3 mg·kg^(-1)).N application significantly decreased soil pH and increased the proportion of weekly bound organic Fe and Mn and Mn oxide-bonded Fe in the soil,further enriching soil DTPA-Fe and DTPA-Mn content.Meanwhile,the correlation analysis showed that the concentration of Fe in grains had a significantly positive correlation with the yield,biomass,harvest index,spike number,grain number per panicle,grain Fe uptake and Fe harvest index,and soil Mn-oxide-bonded Fe,but it has a significantly negative correlation with the grain Mn concentration and soil residual Fe.However,the grain Mn concentration was significantly negatively correlated with grain yield,biomass,harvest index,spike number,grain number per panicle,grain Fe uptake and Fe harvest index,and was significantly positively correlated with the shoot Mn uptake,but there was no significant association found with various forms of Mn in soil.【Conclusion】In the northwest arid area,the long-term nitrogen application on calcareous soil could improve the availability of soil Fe,promote the absorption and localization of Fe in grains,and increase the Fe concentration in grains.Nitrogen application increased the soil Mn availability,but significantly inhibited the uptake of Mn by wheat,and resulted in a significant decrease of Mn concentration in grains.In addition,when the phosphorus supply level is consistent,a long-term lack of soil nitrogen supply may lead to low Fe concentration and high Mn concentration in wheat grains.Considering the yield,the bioavailability of Fe and Mn in grains and the environmentally-economic benefits,it was recommended that nitrogen application rate should be controlled at 160 kg N·hm^(-2)on calcareous soil,since excessive nitrogen application fertilizer would not be conducive to further increase grain yield and improve its nutritional quality.