根据国际热带农业中心的木薯土壤营养指标，海南省的木薯中微肥试验结果表明，当土壤交换性镁处于极低营养水平（12.2 mg/kg）时，施用镁肥的鲜薯产量和淀粉产量分别比不施肥增产14.3%及10.6%；当土壤交换性钙（130.6 mg/kg）、有效锌（0.74 mg/kg）和有效铜（0.11 mg/kg）处于低营养水平时，施用钙、锌和铜肥不起增产作用。根据目前的土壤分析结果，海南和广西木薯主产区的大部分土壤交换性镁含量处于极低营养水平，必须重视施用镁肥，广西和海南的部分木薯土壤的钙、锌、锰、铜和硼含量处于极低或低营养水平，应注意施用相应中微肥。

According to the soil nutritional requirements of cassava which was from International Center of Tropical Agriculture (CIAT), the results of Secondary-micro nutrient fertilizer trial where had been continuous cropping 15 yeas cassava in Danzhou City, Hainan Province, P.R China showed that Mg fertilizer increased 14.3% fresh root yield and 10.6% starch yield compared to without fertilizer (CK) when the soil exchangeable Mg (12.2 mg/kg) was very low nutrition; but Ca, Zn and Cu fertilizer could not increased fresh root yield and starch yield compared to CK when the soil exchangeable Ca (130.6 mg/kg), available Zn (0.74 mg/kg) and Cu (0.11 mg/kg) were low nutrition. According to the soil survey, the soil exchangeable Mg were very low nutrition in many traditional cassava production area in Guangxi Province and Hainan Province, so it need seriously pay attention to apply Mg fertilizer; moreover, the soil exchangeable Ca, available Zn, Mn, Cu and B were very low or low nutrition on some cassava area in Guangxi Province or Hainan Province, it also needed to pay attention to apply above secondary-micro fertilizer.