Benyas Ebrahim, Owens Jennifer, Seyedalikhani Salome, Robinson Brett
J Environ Qual. 2018 Sep;47(5):1249-1257. doi: 10.2134/jeq2018.01.0015.
Cadmium accumulates in soils that receive repeated applications of Cd-rich superphosphate fertilizers. There is evidence that adding clovers to a crop solubilizes soil Cd, increasing the bioavailability of Cd. This can lead to high plant Cd concentrations. This research aimed to test whether liming-induced increases in pH in mixed crops of clovers and ryegrasses reduced forage Cd concentrations. A greenhouse pot trial applied lime at three rates (0, 1, and 2% of soil dry weight) to eight different plant treatments-four as monocultures (perennial ryegrass [ L.], Italian ryegrass [ Lam.], white clover [ L.], and red clover [ L.]) and four as ryegrass-clover mixtures (two plant types in each treatment)-in soil (initial soil pH = 5.1, initial soil Cd concentration = 1.31 mg kg) with added Cd (CdSO ∼ 1 mg kg). Adding lime increased soil pH in both mono- and mixed crops and, in most treatments, increased forage yields. However, the relationship between forage Cd and soil pH differed between plant treatments. In mono- and mixed crop treatments containing perennial ryegrass, adding lime increased the forage yield but did not increase the mass of Cd in the plants compared with the no-lime treatment. However, adding lime to treatments that included Italian ryegrass increased both the forage yield and the Cd compared with the no-lime treatment. The results show that a combination of certain plant species composition and lime rates can optimize forage yields without increasing forage Cd concentrations.
镉会在反复施用富镉过磷酸钙肥料的土壤中积累。有证据表明，在作物中添加三叶草可使土壤中的镉溶解，从而增加镉的生物有效性。这可能导致植物中镉含量升高。本研究旨在测试在三叶草和黑麦草混合作物中，石灰诱导的pH值升高是否会降低饲料中的镉浓度。一项温室盆栽试验以三种施用量（土壤干重的0%、1%和2%）向八种不同的植物处理施加石灰，其中四种为单一栽培（多年生黑麦草[L.]、意大利黑麦草[Lam.]、白三叶草[L.]和红三叶草[L.]），四种为黑麦草 - 三叶草混合物（每种处理中有两种植物类型），土壤（初始土壤pH = 5.1，初始土壤镉浓度 = 1.31 mg/kg）添加了镉（CdSO ∼ 1 mg/kg）。添加石灰使单一作物和混合作物的土壤pH值均升高，并且在大多数处理中提高了饲料产量。然而，不同植物处理中饲料镉含量与土壤pH值之间的关系有所不同。在含有多年生黑麦草的单一作物和混合作物处理中，与不添加石灰的处理相比，添加石灰提高了饲料产量，但并未增加植物中的镉含量。然而，与不添加石灰的处理相比，在包含意大利黑麦草的处理中添加石灰既提高了饲料产量又增加了镉含量。结果表明，特定的植物物种组成和石灰施用量的组合可以在不增加饲料镉浓度的情况下优化饲料产量。
