Submitted at the IAS, December 18 2018

ABSTRACT

Coffee, black pepper, tea and fruit trees have been grown in the red soils (Rhodic Ferralsols – FRr). The study objectives aim at (1) assessing the organic fertilizer, N and P fertilizer application to soil fertility in case of coffee plantation in Di Linh, Lâm Đồng; (2) analyzing the fertilizer application to robusta coffee (Coffea canephora Pierre); (3) proposing a sustainable development of coffee farm under red soil condition.

1. At the bean coffee yield of 3.6 t/ha; there were 77.0%, 97.0%, 36.0% and 48.0% farmers applying N overuse, P overuse, K deficit and K overuse, respectively. Farmer annually applied 1.0-5.3 t/ha organic fertilizer (av. 2.8 t/ha); 8.5-35.0 t/ha compost (av. 16.8 t/ha) with two-three years/ once. Of them, 55% farmers misused organic fertilizer without fermentation.
2. If organic fertilizers were continuously applied for three years, soil density and helpful organisms  increased 7.5% and 7.2%; the CEC, OM, available P₂O₅, available K₂O, Ca²⁺ and Mg²⁺ increased 21.8%, 36.5%, 12.9%, 64.0%, 48.3% and 31.5%, respectively. Otherwise, Al³⁺ decreased 2.4 folds; earth worm increased 2.5, 2.6 and 7.6 folds for population rate, size and biomass, respectively.
3. N fertilizer application of 320 kg/ha/year remained pH H₂O as 5.7-6.0, increased CEC, OM, total N, available K₂O, Ca⁺⁺, Mg⁺⁺; reduced Al⁺⁺⁺.
4. P fertilizer application was recommended as 100 kg P₂O₅ /ha /year. The treatment of 100, 200 kg P₂O₅ /ha /year only improved pH, Ca⁺⁺, Mg⁺⁺ not affecting to soil microorganism situation.

<>5.The final recommendation is to apply 10 t/ha organic fertilizer plus 320-100-350 kg N, P₂O₅, K₂O / ha / year to increase coffee bean more 1.07 t/ha.