CULTIVATION OF XARAÉS GRASS IRRIGATED WITH IRON MINING TAILINGS

ABSTRACT The collapse of the Fundão dam in Brazil caused one of the biggest environmental disasters. One of the challenges was how to manage the tailings so that affected areas could be reused. This study aimed to verify whether applying different irrigation depths to Xaraés grass grown with iron mining tailings would affect grass shoot and root dry masses. The experiment was set up in a randomized design with five irrigation depths (40%, 60%, 80%, 100%, and 120% of crop evapotranspiration) and two additional treatments (grass grown in tailings with soil conditioner, and grass grown in natural soil), each with three repetitions. The grass was cut four times, and the shoot dry mass was evaluated after each cut, while the root dry mass was evaluated at the end of the experiment. Our results showed that irrigation depths had a positive linear effect on shoot dry mass and an exponentially increasing effect on root dry mass, with the highest averages in the treatment applying 120% of crop evapotranspiration. This study showed that even in adverse conditions, Xaraés grass was able to grow and develop well.

摘要 巴西丰当大坝（Fundão Dam）溃坝事件系全球范围内最严重的环境灾难之一。当时面临的核心挑战之一，是如何对铁矿尾矿进行科学处置，以使受影响区域得以复垦再利用。本研究旨在验证：以铁矿尾矿为栽培基质培育Xaraés草（Xaraés grass）时，施加不同梯度的灌溉水量，是否会对该牧草的地上部与地下部干物质重量产生影响。本实验采用完全随机设计，设置5个灌溉处理组（灌溉水量分别为作物蒸发蒸腾量（crop evapotranspiration）的40%、60%、80%、100%及120%），另设2个对照处理组：施加土壤调理剂（soil conditioner）的尾矿基质组、天然土壤栽培组，每组均设置3次生物学重复。试验期间共对牧草进行4次刈割，每次刈割后均测定其地上部干物质重量；于整个实验结束后测定地下部干物质重量。研究结果显示，灌溉深度对牧草地上部干物质重量呈正向线性影响，对地下部干物质重量则呈指数递增效应，其中以灌溉水量为120%作物蒸发蒸腾量的处理组获得最高平均干物质重量。本研究证实，即便处于不利的环境条件下，Xaraés草仍可实现良好的生长与发育。