Coffee agroecosystem performance under full sun, shade, conventional and organic management regimes in Central America

Changes in coffee economics are leading producers to reduce agrochemical use and increase the use of shade. Research is needed on how to balance the competition from shade trees with the provision of ecological services to the coffee. In 2000, long-term coffee experiments were established in Costa Rica and Nicaragua to compare coffee agroecosystem performance under full sun, legume and non-legume shade types, and intensive and moderate conventional and organic inputs. Coffee yield from intensive organic production was not significantly different from intensive conventional in Nicaragua, but in Costa Rica it was lower during three of the six harvests. Full sun coffee production over 6 years was greater than shaded coffee in Costa Rica (61.8 vs. 44.7 t ha^?1, P = 0.0002). In Nicaragua, full sun coffee production over 5 years (32.1 t ha^?1) was equal to coffee with shade that included Tabebuia rosea (Bertol.) DC., (27?C30 t ha^?1) and both were more productive (P = 0.03) than coffee shaded with Inga laurina (Sw.) Willd. (21.6 t ha^?1). Moderate input organic production was significantly lower than other managements under all shade types, except in the presence of Erythrina poepiggina (Walp.) O.F. Cook. Inga and Erythrina had greater basal area and nutrient recycling from prunings than other shade species. Intensive organic production increased soil pH and P, and had higher K compared to moderate conventional. Although legume shade trees potentially provide ecological services to associated coffee, this depends on management of the competition from those same trees.     

Assessment of small mammal diversity in coffee agroforestry in the Western Ghats,India

Coffee agroforestry is a conservation strategy that has shown promise to support the diversity of bird, bat, and insect communities, but few studies have focused on non-volant mammals in coffee farms. We assessed mammal diversity within coffee agroforestry systems in Kodagu, India and investigated the impacts of the non-native shade tree species, Grevillea robusta, on mammal diversity. Twenty farms, with varying amounts of G. robusta planted within the coffee farm, were sampled throughout three rainfall zones during the 4-month study period. We captured six species of small mammals, with indirect methods yielding an additional five species, totaling 11 mammal species. Contrary to current ecological thought, we found that increased amounts of G. robusta did not have a negative impact on either abundance or richness of mammals. Small mammal abundances were higher at farms with greater amounts of herbaceous ground cover and larger, mature shade trees, while small mammal species richness was found to increase with an increase in tree species richness as well as greater amounts of herbaceous ground cover. Additionally, small mammal abundance was higher at coffee farms closer to forested areas. Based on these findings, we suggest the maintenance or cultivation of shade tree richness, mature shade trees, and herbaceous ground cover within coffee farms and preservation of forested areas within the landscape to enhance coffee agroforestry habitat for non-volant mammals. We hope that these habitat requirements will be incorporated into conservation strategies for the promotion of biodiversity within coffee agroforestry systems.     

Shade trees: a determinant to the relative success of organic versus conventional coffee production

Greater understanding of the influences on long-term coffee productivity are needed to develop systems that are profitable, while maximizing ecosystem services and lowering negative environmental impacts. We examine a long-term experiment (15 years) established in Costa Rica in 2000 and compare intensive conventional (IC) coffee production under full sun with 19 agroforestry systems combining timber and service tree species with contrasting characteristics, with conventional and organic managements of different intensities. We assessed productivity through coffee yield and coffee morphological characteristics. IC had the highest productivity but had the highest yield bienniality; in the agroforestry systems productivity was similar for moderate conventional (MC) and intensive organic (IO) treatments (yield 5.3 vs. 5.0 t ha^?1 year^?1). Significantly lower yields were observed under shade than full sun, but coffee morphology was similar. Low input organic production (LO) declined to zero under the shade of the non-legume timber tree Terminalia amazonia but when legume tree species were chosen (Erythrina poepiggiana, Chloroleucon eurycyclum) LO coffee yield was not significantly different than for IO. For the first 6 years, coffee yield was higher under the shade of timber trees (Chloroleucon and Terminalia), while in the subsequent 7 years, Erythrina systems were more productive; presumably this is due to lower shade covers. If IC full sun plantations are not affordable or desired in the future, organic production is an interesting alternative with similar productivity to MC management and in LO systems incorporation of legume tree species is shown to be essential.     

Effect of pollarding frequency on biomass of Erythrina poeppigiana as a coffee shade tree

The use of pollarded Erythrina poeppigiana as shade tree in coffee plantations is apparently an old practice in Costa Rica. The tree is not native to this country but was introduced between late 19th and 20th century and was rapidly dispersed in the coffee and cacao areas. Currently, the Erythrina tree is widespread in the Turrialba Valley (elevation 600—1300m) and in the Central Valley (elevation 1200m) where the species is always associated with present or past coffee crops. Pollarding carried out by Costa Rican farmers constitutes a long dated and functional practice, hence the objective of this study was to evaluate the amount of biomass produced by pollarding of Erythrina poeppigiana used as shade in coffee crop planted at a density of 280 trees/hectare under different pollarding frequencies. Results showed that by pollarding once a year, 18,470 kg of dry matter per hectare are produced; with two pollardings per year 11,800 kg/ha are produced and with three pollarding per year 7,850 kg/ha are produced. The total amount of nitrogen removed is very similar for pollarding once and twice a year, but is lower for three times a year. The amount of nitrogen removed was approximately 230 kg/ha/year in the first two cases and 170 kg/ha/year in the last one.The above observations suggest that a considerable supply of nutrients exist in the systems with shade trees, when they are periodically pollarded.Finally some conclusions and follow up activities related to research on the species are suggested, such as higher biomass production techniques, appropriate planting practices, selection of genetic material, nutrient depletion when biomass is harvested, conversion of leaves to marketable feed sources (flour, pellets), alley cropping and green manure production and restoration of degraded areas and improductive savannas by planting large cuttings that would improve the soil by adding biomass and shade out undesirable grasses.This work is part of a Ph.D. Dissertation submitted to the Southeastern University, New Orleans, Lousiana by R.O. Russo.     

Shade management in coffee and cacao plantations

Shade trees reduce the stress of coffee (Coffea spp.) and cacao (Theobroma cacao) by ameliorating adverse climatic conditions and nutritional imbalances, but they may also compete for growth resources. For example, shade trees buffer high and low temperature extremes by as much as 5 °C and can produce up to 14 Mg ha^-1 yr^-1 of litterfall and pruning residues, containing up to 340 kg N ha^-1 yr^-1. However, N₂ fixation by leguminous shade trees grown at a density of 100 to 300 trees ha^-1 may not exceed 60 kg N ha^-1 yr^-1. Shade tree selection and management are potentially important tools for integrated pest management because increased shade may increase the incidence of some commercially important pests and diseases (such as Phythphora palmivora and Mycena citricolor) and decrease the incidence of others (such as Colletotrichum gloeosporioides and Cercospora coffeicola). In Central America, merchantable timber production from commercially important shade tree species, such as Cordia alliodora, is in the range of 4–6m³ ha^-1 yr^-1. The relative importance and overall effect of the different interactions between shade trees and coffee/cacao are dependent upon site conditions (soil/climate), component selection (species/varieties/provenances), belowground and aboveground characteristics of the trees and crops, and management practices. On optimal sites, coffee can be grown without shade using high agrochemical inputs. However, economic evaluations, which include off-site impacts such as ground water contamination, are needed to judge the desirability of this approach. Moreover, standard silvicultural practices for closed plantations need to be adapted for open-grown trees within coffee/cacao plantations. This revised version was published online in June 2006 with corrections to the Cover Date.     

Above- and belowground biomass,nutrient and carbon stocks contrasting an open-grown and a shaded coffee plantation

Coffee (Coffea canephora var robusta) is grown in Southwestern Togo under shade of native Albizia adianthifolia as a low input cropping system. However, there is no information on carbon and nutrient cycling in these shaded coffee systems. Hence, a study was conducted in a mature coffee plantation in Southwestern Togo to determine carbon and nutrient stocks in shaded versus open-grown coffee systems. Biomass of Albizia trees was predicted by allometry, whereas biomass of coffee bushes was estimated through destructive sampling. Above- and belowground biomass estimates were respectively, 140 Mg ha⁻¹ and 32 Mg ha⁻¹ in the coffee–Albizia association, and 29.7 Mg ha⁻¹ and 18.7 Mg ha⁻¹ in the open-grown system. Albizia trees contributed 87% of total aboveground biomass and 55% of total root biomass in the shaded coffee system. Individual coffee bushes consistently had higher biomass in the open-grown than in the shaded coffee system. Total C stock was 81 Mg ha⁻¹ in the shaded coffee system and only 22.9 Mg ha⁻¹ for coffee grown in the open. Apart from P and Mg, considerable amounts of major nutrients were stored in the shade tree biomass in non-easily recyclable fractions. Plant tissues in the shaded coffee system had higher N concentration, suggesting possible N fixation. Given the potential for competition between the shade trees and coffee for nutrients, particularly in low soil fertility conditions, it is suggested that the shade trees be periodically pruned in order to increase organic matter addition and nutrient return to the soil. An erratum to this article can be found at     

Ecosystem services from coffee agroforestry in Central America: estimation using the CAF2021 model

The goal of sustainable coffee production requires multiple functions from agroforestry systems. Many are difficult to quantify and data are lacking, hampering the choice of shade tree species and agronomic management. Process-based modelling may help quantify ecosystem services and disservices. We introduce and apply coffee agroforestry model CAF2021 (https://doi.org/10.5281/zenodo.5862195). The model allows for complex systems with up to three shade tree species. It simulates coffee yield, timber and fruit production by shade trees, soil loss in erosion, C-sequestration, N-fixation, -emission and -leaching. To calibrate the model, we used multivariate data from 32 different treatments applied in two long-term coffee agroforestry experiments in Costa Rica and Nicaragua. Without any further calibration, the model was then applied to agroforestry systems on 89 farms in Costa Rica and 79 in Guatemala where yields had been reported previously in farmer interviews. Despite wide variation in environmental and agronomic conditions, the model explained 36% of yield variation in Costa Rica but only 15% in Guatemala. Model analysis quantified trade-offs between yield and other ecosystem services as a function of fertilisation and shading.

     

Semi-forest coffee cultivation and the conservation of Ethiopian Afromontane rainforest fragments

Coffea arabica shrubs are indigenous to the understorey of the moist evergreen montane rainforest of Ethiopia. Semi-forest coffee is harvested from semi-wild plants in forest fragments where farmers thin the upper canopy and annually slash the undergrowth. This traditional method of coffee cultivation is a driver for preservation of indigenous forest cover, differing from other forms of agriculture and land use which tend to reduce forest cover. Because coffee farmers are primarily interested in optimizing coffee productivity, understanding how coffee yield is maximized is necessary to evaluate how, and to what extent, coffee production can be compatible with forest conservation.Abiotic variables and biotic variables of the canopy were recorded in 26 plots within 20 forest fragments managed as semi-forest coffee systems near Jimma, SW Ethiopia. In each plot, coffee shrub characteristics and coffee yield were recorded for four coffee shrubs. Cluster and indicator species analyses were used to differentiate plant communities of shade trees. A multilevel linear mixed model approach was then used to evaluate the effect of abiotic soil variables, shade tree plant community, canopy and stand variables, coffee density and coffee shrub size variables on coffee yield.Climax species of the rainforest were underrepresented in the canopy. There were three impoverished shade tree communities, which differed in tree species composition but did not exhibit significant differences in abiotic soil variables, and did not directly influence coffee yield. Coffee yield was primarily determined by coffee shrub branchiness and basal diameter. At the stand level a reduced crown closure increased coffee yield. Yield was highest for coffee shrubs in stands with crown closure less than median (49 ± 1%). All stands showed a reduced number of stems and a lower canopy compared to values reported for undisturbed moist evergreen montane rainforests.Traditional coffee cultivation is associated to low tree species diversity and simplified forest structure: few stems, low canopy height and low crown closure. Despite intensive human interference some of the climax species are still present and may escape local extinction if they are tolerated and allowed to regenerate. The restoration of healthy populations of climax species is critical to preserve the biodiversity, regeneration capacity, vitality and ecosystem functions of the Ethiopian coffee forests.     

Coffee Agroforestry Systems for Conservation and Economic Development

Abstract

The agroforestry program of the AMISCONDE Initiative was implemented in 13 buffer zone communities of La Amistad Biosphere Reserve. This program introduced citrus (Citrus spp.) and promoted the widespread inclusion of poró (Erythrina poeppigiana) shade trees, ground story vegetation, and soil conservation techniques to the local cultivation of coffee (Coffea arabica var caturra). This program sought long-term socioeconomic and ecological health in these buffer zone communities through conservation and development projects such as coffee agroforestry systems. This paper examines the ecological and socioeconomic benefits of two introduced coffee agroforestry systems: coffee-poró and coffee-citrus. The project has decreased agrochemical inputs, integrated multi-strata vegetation, and implemented soil conservation techniques such as vetiver grass, cover crops, terraces, water channeling, and shade trees in an effort to sustainably manage coffee production on the steep buffer zone slopes. The agroforestry project of the AMISCONDE Initiative has likely improved the production of coffee ecologically and economically. However, new specialty markets should be explored to increase economic and ecological gains. Organic and fair trade coffee niche markets are suggested as alternatives for meeting the long-term AMISCONDE objectives of community development and conservation.     

Effects of <Emphasis Type="Italic">Inga densiflora</Emphasis> on the microclimate of coffee (<Emphasis Type="Italic">Coffea arabica</Emphasis> L.) and overall biomass under optimal growing conditions in Costa Rica

The advantages of associating shade trees in coffee agroforestry systems (AFS) are generally thought to be restricted mostly to poor soil and sub-optimal ecological conditions for coffee cultivation whereas their role in optimal conditions remains controversial. Thus, the objective of this study was to investigate, under the optimal coffee cultivation conditions of the Central Valley of Costa Rica, the impact of Inga densiflora, a very common shade tree in Central America, on the microclimate, yield and vegetative development of shaded coffee in comparison to coffee monoculture (MC). Maximum temperature of shaded coffee leaves was reduced by up to 5°C relative to coffee leaf temperature in MC. The minimum air temperature at night was 0.5°C higher in AFS than air temperature in MC demonstrating the buffering effects of shade trees. As judged by the lower relative extractable water (REW) in the deep soil layers during the dry season, water use in AFS was higher than in MC. Nevertheless, competition for water between coffee and associated trees was assumed to be limited as REW in the 0–150 cm soil layer was always higher than 0.3 in shaded coffee compared to 0.4 in monoculture. Coffee production was quite similar in both systems during the establishment of shade trees, however a yield decrease of 30% was observed in AFS compared to MC with a decrease in radiation transmittance to less than 40% during the latter years in the absence of an adequate shade tree pruning. As a result of the high contribution (60%) of shade trees to overall biomass, permanent aerial biomass accumulation in AFS amounted to two times the biomass accumulated in MC after 7 years. Thus provided an adequate pruning, Inga-shaded plantations appeared more advantageous than MC in optimal conditions, especially considering the fact that coffee AFS provides high quality coffee, farmers’ revenue diversification and environmental benefits.     

Migratory bird use of shade coffee: the role of structural and floristic features

Shade coffee plantations support high numbers of Neotropical migratory birds, but relatively little is known about the structural and floristic attributes used by individual species. From 2005 to 2007, we studied the relationship between habitat characteristics and Neotropical migratory birds in shade coffee plantations in the Venezuelan Andes. Our results indicate that density of migrants was significantly related to both structural and floristic attributes of coffee farms. Specifically, upper canopy foragers were positively associated with number of large trees (>38?cm dbh), tree canopy height, and understory vegetation density. Low canopy and ground foragers were positively associated with numbers of small (8?C23?cm dbh) and medium (23?C38?cm dbh) trees and increased shade cover. Moreover, certain tree species, especially Inga spp., Erythrina spp. and Acnistus arborescens, were important components of habitat for those species that forage in the canopy. For example, our detailed foraging observations showed that Inga trees were used in greater proportion than available throughout plantations by Cerulean Warblers (Dendroica cerulea), a species of high conservation concern. Overall, our research suggests that suitability of coffee plantations for migratory birds may be improved by managing for particular structural and floristic characteristics of plantations.     

Transpiration of Arabica Coffee and Associated Shade Tree Species in Sub-optimal, Low-altitude Conditions of Costa Rica

Sap flows of coffee (Coffea arabica L. cv ‘Costa Rica 95’) and associated timber trees (Eucalyptus deglupta or Terminalia ivorensis) or leguminous tree (Erythrina poeppigiana) were measured simultaneously during 12 months in 4-year-old coffee agroforestry systems in sub-optimal ecological conditions of Costa Rica. In the wet period, coffee and shade tree transpiration followed the daily patterns of photosynthetic photon flux density (PPFD) and reference evapotranspiration (ETo) while their transpiration was restricted at higher air VPD values (>1.5 kPa) registered during the dry period. Coffee transpired more per unit leaf area in full sun than under shade, an indication of higher environmental coffee stress in non shaded conditions. Nonetheless, coffee daily water consumption per hectare was generally higher under shade than in full sun due higher vegetative growth of shade-grown coffee plants. Minimum and maximum daily transpiration were 0.74 and 4.08 mm for coffee, 0.35 and 1.06 mm for E. deglupta, 0.70 and 2.10 mm for T. ivorensis and 0.13 and 0.79 mm for E. poeppigiana. Estimation of the annual combined water transpiration by coffee and shade trees was 20–250% higher than that of coffee grown in full sun. Nevertheless, there was no evidence that water use by associated trees decreased soil water availability for coffee and hence limited coffee transpiration in the dry season due to its relatively short length (3 months) and the high annual rainfall (over 3100 mm). In the sub-optimal, low altitude conditions of this experiment, E. deglupta was the optimum shade species as it maintained a more constant shade level throughout the year and ensured a better protection to coffee underneath than T. ivorensis and E. poeppigiana which underwent a complete defoliation during the adverse meteorological conditions of the dry period.     

Identifying key factors affecting coffee leaf rust incidence in agroforestry plantations in Peru

Coffee leaf rust (CLR), caused by Hemileia vastarix, is one of the most serious diseases of coffee plantations and cause great losses in coffee production. We aimed to examine coffee varieties, shade, age of coffee plants, coffee plant density and soil properties in relation to CLR infection. To do this, we established a total of 75 plots in three agroforestry coffee plantations in the central Peruvian Amazon. We gathered data there in 2011 (dry season) on the presence/absence of CLR; coffee variety; age and density of coffee plants, and also took hemispherical photographs to determine canopy openness. In 2014 (wet season), we again gathered data on the same variables. In 2012, we collected soil samples from a subset of the plots. At all plantations, coffee variety had a significant effect on CLR incidence, with the Catimor variety infected less frequently than Caturra. Coffee plant age had a significant positive effect on CLR incidence. Increasing coffee density also increased CLR incidence for some of the studied plantations/seasons. Comparing those plots from which data were collected in the dry and wet seasons, we found that CLR presence was significantly higher in the wet season. The effect of shade on CLR incidence was not clear. Catimor and Caturra varieties showed opposite trends of CLR incidence in response to shade quantity in most cases (Caturra variety CLR incidence was decreasing with shading increase and Catimor CLR incidence decreasing with decreasing shading). Finally, the soil properties did not affect CLR incidence.     

Influence of rubber trees on leaf-miner damage to coffee plants in an agroforestry system

The coffee leaf-miner (CLM) (Leucoptera coffeella Guérin-Mèneville; Lepidoptera: Lyonetiidae), the main pest of coffee plants, occurs widely throughout the Neotropics where it has a significant, negative economic and quantitative impact on coffee production. This study was conducted in a rubber tree/coffee plant interface that was influenced by the trees to a varying degrees depending on the location of the coffee plants, i.e. from beneath the rubber trees, extending through a range of distances from the edge of the tree plantation to end in a coffee monocrop field. The most severe damage inflicted on coffee plants by the CLM (number of mined leaves) from April, which marks the start of the water deficit period, until September 2003 was in the zone close to the rubber trees, whereas the damage inflicted on plants in the monocropped field was comparable to that on coffee plants grown directly beneath the rubber trees, which received about 25–40 % of the available irradiance (I_r—available irradiation at a certain position divided by the irradiation received in full sunlight, i.e. in the monocrop). From May until July damage caused by the CLM nearly doubled in each month. In midwinter (July), the damage decreased perceptibly from the tree edge toward the open field. From September onward, with the rising air temperatures CLM damage in the coffee monocrop started to increase. Based on these results, we conclude that coffee plants grown in the full sun incurred the most damage only at the end of winter, with warming air temperatures. Coffee plants grown in shadier locations (25–40 % I_r) were less damaged by the CLM, although a higher proportion of their leaves were mined. The rubber trees probably acted as a shelter during the cold autumn and winter seasons, leading to greater CLM damage over a distance outside the rubber tree plantation that was about equal to the height of the trees. Future studies should attempt to relate leaf hydric potential to pest attack in field conditions. More rigorous measurements of shade conditions could improve our understanding of the relationship of this factor to CLM attack.     

Growth, productivity and quality of Megathyrsus maximus under cover from Gliricidia sepium

The effect of tree canopy on the growth, productivity and forage quality of Megathyrsus maximus and changes in soil properties were evaluated over three seasonal periods. Four adjacent plots (15 m × 17 m each) in a tropical secondary deciduous forest having 12 years of growth and dominated by Gliricidia sepium were randomly assigned to two treatments: removal of trees (SCA) in two of the plots and leaving trees intact (COA) in the other two. In all plots, M. maximus was planted with 50 cm spacing among plants. Tree removal significantly increased the incident photosynthetically active radiation (PAR, P < 0.001) and grass size (12.5 % in height, P < 0.01, and 16.5 % in clump diameter, P < 0.05), but did not significantly affect any other variable. Season significantly affected grass height (P < 0.003), tiller number (P < 0.001), clump diameter (P < 0.001), net CO₂ assimilation rate (P < 0.001), forage biomass production (P < 0.003), and acid detergent fiber content (P = 0.033). Primary soil changes after 1 year of establishment of the grass were the decline by 3 % in organic carbon (P = 0.03), and qualitative changes in soil structure, regardless of tree presence. Results are consistent with the ability of M. maximus to tolerate shade. We conclude that under the conditions of the study there was no evidence for a negative effect of tree canopy on M. maximus mediated by a reduction in PAR.     

Coffee yields and soil nutrients under the shades of Inga sp. vs. multiple species in Chiapas, Mexico

For many decades, simplification of traditionally shaded coffee-production systems has been an idealised model for increasing yields. In Mexico, coffee producers have been interested in replacing diverse natural shade with Inga species monocultures due to this practice having the supposed advantages of producing higher coffee yields than diverse shade. However, the effect of different shade systems on yields is little known. The purpose of this study was to evaluate the effect of two types of shaded-coffee systems on coffee yields and soil nutrient content; the first shade system is mainly dominated by Inga latibracteata Harms and the other composed of species-rich natural vegetation. The investigation took place in producer plots in the Francisco I. Madero Community, Municipality of Jitotol, Chiapas, Mexico. Collected data included species richness, shade-tree density, number of strata, tree diameter, tree height, shade-cover percentage, direct and diffused light, coffee yields, soil-nutrient concentrations (N, P, K, Ca and Mg), soil-organic matter and pH. Evaluated shade type did not have an effect on grain yield or soil nutrients. The perceived advantage of the Inga shade system is reduced weed emergence, saving farmers one annual weed-clearing. There was no significant correlation between total N and organic matter. The presence of fewer products and services in comparison to the multiple shade system was thought to be an additional disadvantage to the Inga dominated system. Organic matter in the multiple shade system correlated positively with total N. Due to its complex structure and diversity, the multiple shade system could be certified as shade or bird-friendly coffee. This revised version was published online in June 2006 with corrections to the Cover Date.     

Changes in limiting resources determine spatio-temporal variability in tree–grass interactions

Changing biotic and abiotic stress mediate in plant–plant interactions resulting in positive to neutral or negative effects, and these effects can change with gradients of stress or through plant dynamics. Here we studied the variability in annual grass production and composition induced by gradients of intercepted light by trees in years of contrasting precipitation in Mediterranean holm oak open woodlands. Although trees reduce the light radiance received by the pasture community, the presence of trees generally had a positive effect on pasture production in average climatic years where soil fertility was low. However, the interaction changed with increasing abiotic water stress. In a dry year, the increase in fertility could not be utilized and the effect of the crown was neutral. The effect of shade turned out to be beneficial for growth, contrary to the situation in an average climatic year. Light insolation was positive for legume biomass. There was high variability in functional components over the course of the growing period and from 1 year to another. Under low levels of other biotic stresses such as livestock grazing or root competition, the limiting factor among light, soil moisture or soil nutrients may determine whether facilitation or competition occurs.     

Geostatistical modeling of the spatial variability of coffee fine roots under Erythrina shade trees and contrasting soil management

Spatial relationships between root length density of Coffea arabica (coffee RLD) and soil nutrient- related factors at plot scale in a coffee- Erythrina poeppigiana system was studied by geostatistics. In a 24 × 29 m area, (organic and conventional management), coffee and Erythrina fine roots and soil chemical properties were sampled on an irregular grid in the topsoil. A factor analysis explained 83 % of the total variation of the soil attributes. Soil factors were identified: Chemical fertility (CF), Micronutrients, Organic matter, and Acidity (Ac). Based on the spherical model, all the attributes presented a strong spatial structure. The scale of spatial correlation for CF was lesser than for Ac, but similar to coffee RLD. Erythrina RLD had a short-range variation. Patchy areas of high spots of coffee RLD were greater in organic plot. Cross-semivariogram analysis estimated a correlation between soil factors and coffee RLD over a scale of 5.50 m; but 4.23 m with Erythrina RLD. Nutrients linked to P, Zn, exchangeable bases and acidity soil affected the scale of spatial aggregation pattern of coffee RLD. The spatial response of coffee RLD suggests a differential nutrient uptake strategy for acquiring soil nutrients induced by the quality of organic and inorganic fertilizer inputs. The fact that coffee RLD had higher scale of spatial variation than Erythrina RLD and a negative spatial correlation indicate that pruned Erythrina trees are not so competitive for acquiring shared nutrients in an agroforestry system.     

Allometric models for estimating aboveground biomass of shade trees and coffee bushes grown together

Allometric models for dominant shade tree species and coffee plants (Coffea arabica) were developed for coffee agroforestry systems in Matagalpa, Nicaragua. The studied shade tree species were Cordia alliodora, Juglans olanchana, Inga tonduzzi and I. punctata. The models predict aboveground biomass based on diameter at breast height (for trees), and the stem diameter at a height of 15 cm and plant height (for coffee plants). In addition, the specific gravity of the studied species was determined.The total aboveground biomass of the shade trees varied between 3.5 and 386 kg per tree, and between 0.005 and 2.8 kg per plant for coffee. The aboveground biomass components (foliage, branch, and stem) are closely related with diameter at breast height (r > 0.75). The best-fit models for aboveground biomass of the shade trees were logarithmic, with adjusted R ² between 0.71 and 0.97. In coffee plants, a high correlation was found (r = 0.84) with the stem diameter at 15 cm height, and the best-fit model was logarithmic, as well. The mean specific gravity was 0.52 (± 0.11) for trees and 0.82 (± 0.06) for coffee plants.     

Shade improves coffee quality in a sub-optimal coffee-zone of Costa Rica

Quality is an important attribute of coffee. Therefore it is important to understand the effect of overstory trees not only on the environment and long-term coffee production, but also on the quality of coffee grown underneath the trees. This study compared coffee quality of Coffea arabica L. vars. Caturra and Catimor 5175 under different levels of shade in a low-elevation, sub-optimal environment for coffee in Costa Rica. Fruit weight and bean size increased significantly when shade intensity was increased from 0% to more than 80% under unpruned Erythrina poeppigiana. While large beans (diameter > 6.7 mm) accounted for 49 and 43% of the coffee from unshaded Caturra and Catimor, respectively, these proportions increased to 69 and 72% under dense permanent shade. This suggested a stronger shade benefit for Catimor than for Caturra. The conversion percentages from fresh-weight coffee fruits to dry-weight green coffee for export were not affected by the treatments. A blind tasting experiment showed consistent shade-induced improvements in appearance of green and roasted coffee as well as in acidity and body of the brew for both varieties. The effect of shade on aroma of the brew was neutral for Caturra and slightly negative for Catimor. It is hypothesized that, in the sub-optimal (low-altitude) coffee-zone studied, shade promotes slower and more balanced filling and uniform ripening of berries, thus yielding a better-quality product than unshaded coffee plants. Shade experiments along environmental gradients should help to validate this conjecture and its relative importance in different coffee-zones.