Biochar amendments have been considered to increase the competitive abilities of legumes in mixed cultures. However, little is known about how biochar affects the nutrient and Cd allocation within legume-grass mixtures. Therefore, we conducted a pot experiment to explore the effects of biochar addition rate (0, 1, 2.5, and 5%) on four monocultures, the legume Trifolium repens (Tr), Lolium perenne (Lp), Dactylis glomerata (Dg) and Festuca arundinacea (Fa), and three mixed cultures, i.e., Tr + Lp, Tr + Lp + Dg, and Tr + Lp + Dg + Fa. Regardless of biochar addition, Tr plants showed the lowest aboveground Cd concentration among the monoculture treatments. Compared with non-biochar addition treatment, the 1% biochar addition significantly promoted aboveground biomass accumulation and P, K, Ca, and Mg uptake in the aboveground parts of the Tr monoculture treatments by 39.32, 39.88, 88.27, 69.68, and 51.96%, respectively. Nevertheless, the aboveground biomass and P, K, Ca, and Mg uptake as well as the proportion of these parameters in Tr plants in all plant species mixture treatments decreased after biochar application. Maximum aboveground P and Mg uptake occurred in the four-species mixture treatments without biochar addition, whereas maximum values of these parameters occurred in the three-species mixture treatments with 5% biochar addition. Shoot Cd uptake was not decreased by biochar addition at all plant species treatments. Based on the results, it was suggested that biochar could not reduce Cd uptake by increasing the proportion of legumes in the legume-grass mixtures. The complementarity effects on nutrient uptake in the plant species mixtures depended on the amount of biochar added.

中文翻译：

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生物炭改变了Cd污染土壤中豆类草混合物的生物量和元素分配。

人们已经考虑过对生物炭的改良，以提高豆类在混合文化中的竞争能力。然而，关于生物炭如何影响豆类-草混合物中养分和镉分配的知之甚少。因此，我们进行了盆栽实验，探讨了生物炭添加量（0、1、2.5和5％）对四种单一培养物的影响，豆科植物三叶草（Tr），黑麦草（Lp），小球藻（Dg）和Festuca arundinacea（Fa）和三种混合培养物，即Tr + Lp，Tr + Lp + Dg和Tr + Lp + Dg + Fa。不管添加生物炭如何，Tr植物在单培养处理中的地上部Cd浓度最低。与非生物炭添加处理相比，添加1％的生物炭显着促进了地上生物量的积累以及P，K，Ca，Tr单培养处理地上部分的Mg和Mg吸收分别为39.32、39.88、88.27、69.68和51.96％。然而，在施用生物炭后，所有植物物种混合处理中地上生物量和磷，钾，钙和镁的吸收以及这些参数在Tr植物中的比例均下降。在没有添加生物炭的四种混合处理中，最大的地上磷和镁吸收发生，而在添加了5％生物炭的三种混合处理中，这些参数的最大值出现在三种混合处理中。在所有植物物种处理中，添加生物炭都不会降低芽中镉的吸收。根据结果​​，有人提出生物炭不能通过增加豆科植物和豆类混合物中豆类的比例来减少镉的吸收。