Effect of nitrogen and potassium on growth and yield of coffee (Coffea arabica L.) in tropical Queensland

Abstract

The effects of nitrogen (N) and potassium (K) on coffee (Coffea arabica L.) growth and yield in a shallow sandy soil in North Queensland were studied over 5 years following field establishment. High rates of N (416 and 624 kg/ha) applied frequently were necessary for rapid growth and yield of cvv. Kairi Typica (K2), Caturra Rojo (CR33), Catuai Rojo (CR35), and Bourbon Red (B61). Although data were not significant, mean yields with 416 and 624 kg N/ha were greater than with 208 kg/ha by 124 and 145% in 1986, by 12 and 26% in 1987, and by 38 and 31% in 1988. Increasing rates of K (63, 126 and 189 kg K/ha) did not affect growth and did not significantly increase yield in the later stages of the experiment. Neither N nor K had any affect on green bean size or time of berry maturity. CR35 was the highest yielding cultivar (3752 kg/ha of green bean in 4 years of cropping) and B61 the lowest (2067 kg/ha). Height and girth were ranked K2 > CR35 > CR33 > B61. B61 also had significantly fewer and shorter longest primary laterals. CR35 ripened later than other cultivars, while B61 produced the highest percentage of large beans, and K2 the highest percentage of small beans. Preliminary recommendations for coffee growers in this region are 100 kg N/ha in year 1, increasing to 400 kg/ha in year 4; and 80 kg K/ha in year 1, increasing to 320 kg K/ha in year 4. Monthly, rather than quarterly, applications are recommended.