The impact of close spacing on yield of arabica coffee under contrasting agro-ecologies of Ethiopia

摘要

In an attempt to investigate the efficiency of close spacing and determine the optimum density for the approved coffee berry disease (CBD) resistant selections, field experiments were conducted at Tepi, Wenago, and Gera Research Centers for eleven consecutive years (1988/89-1998/99). A randomised complete block design was used to assign seven population densities that ranged between 4,006 and 10,000 trees ha~(-1) Coffee yield results of seven years revealed significant yield responses to close spacing in different crop seasons at each site, specifically when the trees bore heavy crops. Subsequently, coffee yield increased with increasing population densities, though the magnitude varied across crop years and locations. The combined analysis of variance at Wenago and Tepi showed non-significant yield difference, but differences were highly significant at Gera. The interactions of crop season and spacing were also significant at Tepi and Gera, but this was not the case at Wenago. At Tepi, yield initially increased with increasing tree populations up to the fifth crop but, thereafter, tended to decrease above the population densities of 7,062 trees ha~(-1), at hot and humid agroecology indicating early mutual shading effects. In contrast, in medium(Wenago) and high altitude (Gera) areas, yield increased from 13.22 to 21.84 and 17.05 to 25.84 Q ha~(-1), respectively, with increasing population density from 4,006 to 9,066 tress ha~(-1). Such impacts of close spacing on coffee yield performances were largely associated with the prevailing climatic factors that determined the rate of vegetative growth and subsequent adverse mutual shading effects.