Response Of Four Robusta Coffee (Coffea Canephora) Varieties To Nitrogen, Phosphorus And Potassium

ABSTRACT

The study aimed at identifying the best varieties among the four Robusta coffee varieties in terms of N, P and K nutrients use efficiency, absorption efficiency and translocation efficiency. First, a survey was conducted to determine the fertility status of the coffee-growing areas in eight villages namely Igomba, Kiilima, Katangalala, Mishozi, Katale, Bugabo, Bulinda and Bugaruka. Then, a screen house pot experiment was conducted in a Completely Randomized Design in a 3x4 factorial scheme with three rates of N, P and K; Urea (0, 150, 300 kg N/ha equivalent to 0, 75, 150 mg N/kg of soil), TSP (0, 75, 150 kg P/ha equivalent to 0, 37.5, 75 mg P/kg of soil) and KCl (0, 150, 300 kg K/ha equivalent to 0, 75, 150 mg K/kg of soil) and four Robusta coffee varieties (MR 10, BK 27, ML 2 and 13/61). After 6 months, the whole plants were uprooted, washed and roots separated from the aerial parts for determination of shoot dry matter and root dry matter, and N, P and K contents in the whole coffee plants. Nutrient use efficiency, nutrient absorption efficiency and nutrient translocation efficiency for N, P and K were calculated. Results indicated that the overall soil fertility status of the surveyed areas were generally low, with low pH ranged from 4.12 to 5.53, organic carbon ranged from 0.09% to 2.25%, total nitrogen range from 0.056 to 0.192 %, available P ranged from 20.21 to 68.29 mg/kg and potassium ranged from 0.11 to 1.81 cmol (+) kg-1 . The varieties MR 10, BK 27 and 13/61 are most efficient in low nitrogen. Varieties BK 27 and 13/61 are most efficient in low soil P and K. Varieties which are more responsive and efficient to absorb translocation and use the added nutrients' elements and hence can adapt to low soil fertility areas are BK 27, 13/61 and MR 10. In order to improve the production level of coffee in Kagera, distribution of the most responsive varieties should be the first priority