AMI-AMI alpha fertilizer is a liquid biofertilizer for coffee tree. In this study, the authors screened the effects of AMI-AMI alpha fertilizer on Robusta coffee trees over 20 years old culturing in bazan soil, in Dak Lak province based on fertilizer formula 260 kg N + 95 kg P2O5 + 240 kg K2O/ha, according to Robusta coffee tree replaning process of the Cultivation Deparment, Ministry of Agriculture and Rural Development. The result showed that the AMI-AMI formula with the 120 percent nitrogen equivalent dose (6.930 liters of AMI-AMI alpha + 95 kg P2O5 + 240 kg K2O/year/ha) had the highest contents oftotal nitrogen, available phosphorus, available potassium in soils and leaves. It also had the positive impacts on the growth, development such as: increases chlorophyll a up to 10 percent
photosynthetic intensity 13 percent, increases reserve branches length 8 percent
reduce 7 percent rate of fresh/dry of coffee bean, reaches 3.16 tons of coffee beans/ha which was 10 percent higher in compare with the control formula, gained the profit of 42.76 millions VND/ha/year that was 6.58 millions VND higher the control.