Yield performance of Coffea arabica cultivars under different shade trees at Jimma Research Center, southwest Ethiopia

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1 Yield performance of Coffea arabica cultivars under different shade trees at Jimma Research Center, southwest Ethiopia Taye Kufa, Alemseged Yilma, Tesfaye Shimber, Anteneh Nestere and Endale Taye Ethiopian Institute of Agricultural Research, Jimma Agricultural Research Center, P. O. Box 192, Jimma, Ethiopia Corresponding author: Abstract Coffea arabica is originated in the montane rainforests of southwest Ethiopia and thus it is a shade-loving plant, but thrives best in moderate shading. The original forest habitat is being disturbed largely due to deforestation practice in parallel with an increasing population pressure. Therefore there is an urgent need to identify prominent coffee shade trees and this study was conducted with the primary objective to evaluate the yield response of known Coffea arabica cultivars sub-planted under different shade trees at the Jimma Research Center, southwest Ethiopia. Shade tree arboreta consisting of eight coffee shade trees were established to sub-plant with coffee berry disease resistant Coffea arabica cultivars in split-plot design with three replications. The shade trees and coffee cultivars were assigned as main and sub-plot factor, respectively. All the routine cultural practices were uniformly applied to the experimental field throughout the study period. All agronomic variables were considered at the different growth stages of coffee trees, though yield response is focused in this paper. The findings depict that the highest and most stable coffee yield performances were obtained under Albizia schimperiana, Acacia abyssinica and Cordia africana. This could be attributed to the contributions of such leguminous trees to enrich soil fertility status and provide moderate light intensity through their feathery leaves. The slight yield differences among the Coffea arabica cultivars can also provide information the genetic diversity among the immense germplasms in the country. The absence of significant interaction effects between shade and coffee cultivars throughout the study period could reflect the adaptation of Coffea arabica to a more heterogeneous shade environment in its natural habitat. Generally, it can be concluded that the aforementioned leguminous trees are among the prominent coffee shade trees that can be advocated for sustainable production of high quality organic coffee in the southwest Ethiopia. Introduction In its center of origin and genetic diversity in Ethiopia, Coffea arabica grows wild in the montane rainforests of southwestern as an under-story shrub in the deeply shaded forest canopy cover (Coste, 1992). Although, the crop is said to be a shade loving plant with greater quantum utilization efficiency for photosynthesis, excessive shading by upper two to three canopy strata of various tree species under forest environment would decrease growth and productivity of coffee trees because the plant spent much of their photosynthetic activities for maintenance purpose (Tesfaye et al., 2002). Heavy shading due to light penetration by the upper canopy strata can result in increased competition for light for photosynthesis. Subsequently, undesirable growth of single stemmed coffee trees

2 with thin leaves and reduced reproductive efficiency are evident. Again, dark respiration can result in death of heavily shaded productive middle and bottom primary branches and thus productivity of the coffee tree considerably decreased (Tesfaye et al., 2002). On the other hand, in full sun conditions there will be inadequate reaction centers to accommodate the light energy and convert into biochemical energy and the coffee plant photorespires excessively and eventually most of the stored carbohydrates get depleted, which ultimate problem of shoot and root die-backs. Besides, excessive evapotransparation and sever water stress, death of actively growing shoot parts, such as branch tips, seasonal crinkling of leaves, frost damages hot and cold disorder and subsequent yield reduction are common problems in unshaded coffee stands (Cambrony, 1992). The findings of Kumar (1979) indicated that coffee is a C 3 or an intermediate between C 3 and C 4, flourishing best under moderate shade regimes. In line with this, Yacob et al. (1996) also demonstrated that coffee shade trees can create more favorable environments than full sun exposed conditions. Hence, Coffea arabica is a shade-adapted plant (Coste, 1992; Wintgens, 2004), but thrives best in moderate shading (Yacob et al., 1996). Despite this, the forest habitat of Coffea arabica gene pools is being disturbed largely due to deforestation practice in parallel with the increasing population pressure. Moreover, the indigenous shade trees are being drying because of age and other biotic stresses. Coffee cultivars of the same species are different in crown habits and could differently respond to varying irradiances that reaches through the upper canopies. Hence, investigation on the establishment of shade tree arboreta to simulate the original forest habitat of Coffea arabica is crucial for sustainable coffee production. Despite its decisive role in the national economy, coffee has remained small-holders crop in Ethiopia and thus predominantly produced under heterogeneous shade conditions. Taye and Tesfaye (2002) reported that this traditional farmers production system can maintain environmentally friendly environments while producing high quality and fully organic coffees in the country. This study was, therefore, conducted with the main objective to evaluate the yield response of known Coffea arabica cultivars sub-planted under different shade trees at the Jimma Research Center, southwest Ethiopia. Material and Methods Study area The experiment was undertaken at the Jimma Agricultural Research Center, southwest Ethiopia (7 46 N, 36 E, 1973 m.a.s.l). The area receives high amount of rainfall with a long-term mean total of 1557 mm per annum, a mono-modal rainfall pattern. The average maximum and minimum temperatures are 26.7 and 12.8 C, respectively. The dominant coffee soils at JARC are classified as Nitosols, which are highly weathered and originated from volcanic rocks. These soils are deep and well drained and have medium to high contents of most of the essential elements, except nitrogen and phosphors (Paulos, 1994; Mesfin, 1998). Treatments and design Shade tree arboreta consisting of eight coffee shade trees were established to sub-plant with coffee berry disease resistant Coffea arabica cultivars in split-plot design with three replications. The shade trees and coffee cultivars were assigned as main and sub-plot factor, respectively. In this case, the shade trees were planted at a spacing of 5 x 5 m,

3 while the coffee cultivars were planted at 2 x 2 m. The routine cultural practices were uniformly applied and all agronomic parameters of coffee trees were considered at different growth stages, though yield is the focus of this paper. Statistical analysis Coffee yields were recorded for nine consecutive years (1993/ /02) and statistically analyzed in split-plot design with three replicates. The analysis of variances (ANOVA) was computed for each crop year and combined years using the standard procedures. Moreover, treatment means were separated using LSD at 0.05 probability level whenever the F-test declares significant differences. Results and discussion Coffea arabica cultivars planted under the various shade trees did not show significant yield response in most of the crop seasons, except at the very early crop years in 1993/94 and 1995/96 (Table 1). In additions, the effects of coffee shade trees on coffee yield performances were inconsistent over crop season. The overall average results depict that coffee trees planted under Acacia abyssinica resulted in the significantly highest clean coffee yield followed by Albizia schimperiana, Cordia africana, Croton macrostachyus, Calpurina subdecondra, Milletia ferruginea and Erythrina abyssinica (Table 1). This was in contrast to the highly significantly least value beneath Spathodia nelotica (Figure 1), indicating that it is not amongst the suitable coffee shade trees, but rather can be used as an ornamental tree. Nonetheless, the most unstable yields were noted from Cordia africana and Erythrina abyssinica sub-planted coffee trees, possibly due to their deciduous nature and thus adverse effects of maximum light in the dry season. The autumn/winter defoliating shade trees (Albizia schimperiana) and spring/summer defoliant ones (Milletia ferruginea, Acacia abyssinica, Erythrina abyssinica and Calpurinea subdecondra) and broad leaved deciduous tree (Cordia africana) seem to be the most suitable coffee shade trees for coffee production. Their contributions could be largely associated to modification of the microclimate, particularly in reducing the diurnal temperature fluctuations in wet and dry seasons. Beside the other multiple agroforestry advantages, the decomposition from the litter fall can buildup soil fertility status and their canopy intercept almost half of the incoming sun light intensity and ultimately improve the growth and development of coffee trees (Tesfaye et al., 2002, Wintgens, 2004). Taye and Tesfaye (2002) also underlined that Ethiopian coffee is de facto organic as it is predominantly produced by the small-holdings in garden coffee production system, though ecophysiological studies remain for further work. Similarly, the Coffea arabica cultivars did not show significant yield differences in all crop season, except the highly significant during the initial crop year. Moreover, the yield performances were inconsistent over crop years, largely due to the biennial bearing nature of coffee plant. The overall average result depicts that cultivar 7440 gave slightly higher yield than cultivars 7487 and 754 in that order (Table 1). Unlike the other cultivars, the highest coefficient of variation was also computed for the cultivar 7487 that showed the least yield level. According to Yacob et al. (1996), the former two cultivars have an intermediate canopy size, while the later has an open canopy spreading nature. There were no significant interaction effects between shade tree and coffee cultivar over

4 the study periods, indicating the adaptation of the coffee species to the multi-strata and heterogeneous shadings in its original habitat. Conclusions The findings depict that the highest and stable coffee yield performances were obtained under Albizia schimperiana, Acacia abyssinica and Cordia africana. Generally, it can be concluded that these leguminous trees are among the most prominent coffee shade trees for sustainable coffee production under Jimma and other similar areas where they can adapt well. The slight yield differences among the Coffea arabica cultivars could also demonstrate the existence of genetic diversity among the coffee germplasms in the country. Coffee is a shade adapted plant and establishments of model coffee agroforestry systems, which takes into account the indigenous farmers practice, soil-moisture dynamics and carbon sequestration is critically important. Hence, comprehensive studies, inter alias, on nursery and field management practices, multiplication and distribution systems, extent of litter fall and mineralization processes, microclimatic variables and quality attributes of Coffea arabica cultivars are among the top priority areas that remained for further research under different agro-ecological zones of the country. References Cambrony H. R Coffee growing. CTA/The Macmillan Press LTD, New York, Tokyo. Coste R Coffee: The plant and the product. Macmillan, London. Kumar D Some aspects of the physiology of Coffea arabica L. A review. Kenya Coffee 44(519): Mesfin Abebe Nature and management of Ethiopian soils. Alemaya University of Agriculture/ILRI, Addis Ababa, Ethiopia. Taye Kufa and Tesfaye Shimber Organic coffee production: hope for small-scale farmer in Ethiopia. Proceedings of the 19 th International Conference on Coffee Science (ASIC), May 14 th -18 th, 2001, Trieste, Italy. Tesfaye Shimber, Taye Kufa and Alemseged Yilma The effect of established shade trees on the growth and yield of arabica coffee in two planting patterns. Proceedings of the International Conference on Coffee Science (ASIC), May 14 th - 18 th, 2001, Trieste, Italy. Tesfaye Shimber, Yacob Edjamo, Alemseged Yilma and Taye Kufa Research achievement and transferable technologies in coffee agronomy. Pp Proceedings of the 3 rd technology generation, transfer and gap analysis workshop, November 1996, Nekemte, Ethiopia. Wintgens J. N. (ed.) Coffee: Growing, Processing, Sustainable Production. A guide for growers, traders and researchers. WILEY-VCH Verlag GmbH and Co.KGaA, Weinheim, Germany. Yacob Edjamo, Tesfaye Shimber, Taye Kufa, Anteneh Netsere, Takele Negewo and Alemseged Yilma Advances in Coffee Agronomy Research in Ethiopia. Pp In: J. S. Tenywa, Adipala Ekwamu and M. W. Ogengu-Latigo (eds.). Proceedings of Inter-Africa Coffee Organization (IACO) Workshop, 4-6 September 1995, Kampala, Uganda.

5 Figure 1. Mean clean coffee yield of Coffea arabica under different shade trees at Jimma Research Center, southwest Ethiopia Coffee yield (kg/ha Albizia schemperiana Acacia abyssinica Cordia africana Croton macrostachyus Calpurina subdecondra Erythrina abyssinica Spathodia nelotica Milletia ferruginea

6 Table 1. Mean clean coffee yields (kg ha -1 ) of Coffea arabica cultivars sub-planted with various shade trees Jimma Research Center, southwest Ethiopia Treatment 1993/ / / / / / / / /02 Mean CV (%) Shade tree ** Ns ** Ns Ns Ns Ns Ns Ns ** Albizia schimperiana 1612a abc ab 36 Acacia abyssinica 1722a a a 48 Cordia africana 1031a bcd abc 56 Croton macrostachyus 869ab abc bc 49 Calpurina subdecondra 1605a ab abc 48 Erythrina abyssinica 1119a d c 56 Spathodia nelotica 181b d d 40 Milletia ferruginea 1108a cd c 51 SE (±) CV (%) Coffee cultivar ** Ns Ns Ns Ns Ns Ns Ns Ns Ns a b ab SE (±) CV (%) Ns and ** = Non-significant and significant at 0.01 probability, respectively. Figures within a column followed by the same letter(s) are not significantly different at the 0.05 probability level.