Ca, Mg, Zn, Cu Nutrient Fertilizer:

● Some secondary-micro Nutrient Fertilizer trial was not good yield effect . 

● Ca, Mg, Zn, Cu fertilizer trial on continuous cropping 15 yeas cassava in CATAS: Compare to without fertilizer (CK) , Mg fertilizer increased 14.3% FRY and 10.6% SY when soil exchangeable Mg (12.2 mg/kg) was very low nutrition; but Ca, Zn and Cu fertilizer could not increased FRY and SC when 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, soil exchangeable Mg were very low nutrition in many traditional cassava production area in Guangxi and Hainan Province, it need to apply Mg fertilizer. Soil exchangeable Ca, available Zn, Mn, Cu and B were very low or low nutrition on some cassava area in Guangxi or Hainan Province, it needed to pay attention.

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