Soil Protection, Institute of Terrestrial Ecosystems, Department of Environmental Systems Science, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland.
Plant Nutrition, Institute of Agricultural Sciences, Department of Environmental Systems Science, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland.
Sci Total Environ. 2019 Jun 15;669:608-620. doi: 10.1016/j.scitotenv.2019.03.112. Epub 2019 Mar 9.
Wheat is a staple food crop and a major source of both the essential micronutrient zinc (Zn) and the toxic heavy metal cadmium (Cd) for humans. Since Zn and Cd are chemically similar, increasing Zn concentrations in wheat grains (biofortification), while preventing Cd accumulation, is an agronomic challenge. We used two Swiss agricultural long-term field trials, the "Dynamic-Organic-Conventional System Comparison Trial" (DOK) and the "Zurich Organic Fertilization Experiment" (ZOFE), to investigate the impact of long-term organic, mineral and combined fertilizer inputs on total and phytoavailable concentrations of soil Zn and Cd and their accumulation in winter wheat (Triticum aestivum L.). "Diffusive gradients in thin films" (DGT) and diethylene-triamine-pentaacetic acid (DTPA) extraction were used as proxies for plant available soil metals. Compared to unfertilized controls, long-term organic fertilization with composted manure or green waste compost led to higher soil organic carbon, cation exchange capacity and pH, while DGT-available Zn and Cd concentrations were reduced. The DGT method was a strong predictor of shoot and grain Cd, but not Zn concentrations. Shoot and grain Zn concentrations correlated with DTPA-extractable and total soil Zn concentrations in the ZOFE, but not the DOK trial. Long-term compost fertilization led to lower accumulation of Cd in wheat grains, but did not affect grain Zn. Therefore, Zn/Cd ratios in the grains increased. High Zn and Cd inputs with organic fertilizers and high Cd inputs with phosphate fertilizers led to positive Zn and Cd mass balances when taking into account atmospheric deposition and fertilizer inputs. On the other hand, mineral fertilization led to the depletion of soil Zn due to higher yields and thus higher Zn exports than under organic management. The study supports the use of organic fertilizers for reducing Cd concentrations of wheat grains in the long-term, given that the quality of the fertilizers is guaranteed.
小麦是一种主要的粮食作物，也是人体必需微量元素锌（Zn）和有毒重金属镉（Cd）的主要来源。由于 Zn 和 Cd 在化学性质上相似，因此增加小麦籽粒中的 Zn 浓度（生物强化），同时防止 Cd 积累，是一个农业挑战。我们使用两个瑞士农业长期田间试验，即“动态有机常规系统比较试验”（DOK）和“苏黎世有机施肥试验”（ZOFE），研究了长期有机、矿物和复合肥料输入对土壤 Zn 和 Cd 的总量和植物有效浓度及其在冬小麦（Triticum aestivum L.）中的积累的影响。“薄膜扩散梯度”（DGT）和二乙三胺五乙酸（DTPA）提取被用作植物可用土壤金属的替代物。与未施肥对照相比，堆肥或绿肥堆肥的长期有机施肥导致土壤有机碳、阳离子交换量和 pH 值升高，而 DGT 有效 Zn 和 Cd 浓度降低。DGT 方法是预测地上部和籽粒 Cd 的有力指标，但不是 Zn 浓度。在 ZOFE 中，地上部和籽粒 Zn 浓度与 DTPA 可提取和总土壤 Zn 浓度相关，但在 DOK 试验中则不然。长期堆肥施肥导致小麦籽粒中 Cd 积累减少，但不影响籽粒 Zn。因此，籽粒中 Zn/Cd 比值增加。考虑到大气沉降和肥料投入，有机肥中高 Zn 和 Cd 输入以及磷肥中高 Cd 输入导致 Zn 和 Cd 质量平衡为正。另一方面，由于产量较高，因此与有机管理相比，矿物施肥导致土壤 Zn 耗尽，从而导致更高的 Zn 出口量。该研究支持在长期内使用有机肥来降低小麦籽粒中的 Cd 浓度，前提是肥料的质量得到保证。
