University of Pisa
Department of Agricultural, Food and Agro-Environmental Sciences
Master Course Agrifood Production and Agro-Ecosystem Management
Evaluation of different species of cover crops as a sustainable strategy for
weed management and soil fertility preservation in high quality coffee
plantations (Coffea arabica L.) in Costa Rica
First Supervisor
Dr. Daniele Antichi
Second Supervisor
Student
Prof. Paolo Barberi
Jessica Girardi
Opponent
Dr. Robin Gómez Gómez
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History lives in soils as much as in cathedrals or books. In them, the successes and mistakes of our ancestors can be found.
Acknowledgements
This thesis project has been made possible thanks to the financial contribution of the University of Pisa, into the call “Thesis Degree Abroad”, and thanks to the support given to my field work by the University of Costa Rica, through the project titled “Coberturas vivas en plantaciones de café”.
I would like to thank Dr. Daniele Antichi, Dr. Robin Gómez Gómez and Prof. Paolo Bàrberi for their professional cooperation throughout this final work and their comments on the manuscript. I am very grateful for the advice on data analysis from Stefano Carlesi. The following UCR students collaborated in data collection and laboratory work: Paulina, Daniela and Priscilla, and they all friendly support me in learning Spanish. I am especially grateful for the invaluable assistance in the field from Juan Carlos and Mauricio. I would further like to thank all the people I met throughout those two years Master Course.
3 Index
Summary……… 6
1 Introduction………. 8
1.1 History and global importance of coffee……….. 8
1.2 Coffee in Costa Rica.………..… 12
1.2.1 Production systems………. 15
1.2.1.1 Coffee-based agroforestry vs full sun plantation……… 16
1.2.1.2 Organic coffee………. 20
1.2.2 “El beneficiado”………. 22
1.3 The market: Costa Rican coffee excellence……….. 24
2 The crop……… 27
2.1 Environmental requirements………. 31
2.2 Agronomic requirements……….. 32
2.3 Main varieties in Costa Rica………. 33
2.4 Diseases and insect pests……….. 35
3 Weed as accompanying vegetation: when and how to manage it……….. 39
3.1 Mechanical control………. 44
3.2 Chemical control……….. 45
3.3 Cultivation practices: intercrop systems………. 47
3.3.1 Permanent shade-provide intercropping: agroforestry……… 48
3.3.2 Temporary intercropping: cover crops………. 50
3.3.2.1 Best - bet legume cover crops options in Costa Rica………….. 54
4 Problem statement and justification……….. 57
5 Objectives……….. 58
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6.1 Trial 1……….. 59
6.1.1 Experimental site ……… 59
6.1.1.1 Environmental responsibility of the experimental station…. 59 6.1.1.2 Soil analysis ………. 60
6.1.1.3 Rainfall and temperature……… 60
6.1.2 Experimental design……….. 62
6.1.3 Cover crop species……….. 62
6.1.4 Agronomic management... 63
6.1.5 Evaluated variables………... 65
6.1.5.1 Cover crop germination rate……… 65
6.1.5.2 Cover percentage……… 65
6.1.5.3 Cover crop biomass production and growth rate………. 66
6.1.5.4 Cover crops pre-flowering biomass, nitrogen and carbon dioxide foliar accumulation……….. 67
6.1.5.5 Weed density and composition………... 69
6.1.6 Statistical analysis………. 69
6.2 Trial 2……… 71
6.2.1 Experimental site……….. 71
6.2.1.1 Environmental responsibility of the farm………. 71
6.2.1.2 Soil analysis……… 72
6.2.1.3 Rainfall and temperature………. 72
6.2.2 Experimental design……… 74
6.2.3 Cover crop species... 75
6.2.4 Agronomic management... 75
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6.2.5.1 Cover crop germination rate………. 77
6.2.5.2 Cover percentage……….. 77
6.2.5.3 Cover crop biomass production and growth rate……….. 78
6.2.5.4 Cover crops pre-flowering biomass accumulation and coffee plant height………... 79
6.2.5.5 Weed density and composition……….. 79
6.2.6 Statistical analysis……… 79
7 Results and discussion……… 81
7.1 Trial 1……….. 81
7.1.1 Cover crop germination rate……… 81
7.1.2 Cover crop biomass production and growth rate………. 82
7.1.3 Cover crops pre-flowering biomass, nitrogen and carbon dioxide foliar accumulation……….. 86
7.1.4 Weed density and composition………. 89
7.2 Trial 2……… 92
7.2.1 Cover crop germination rate………. 92
7.2.2 Cover crop biomass production and growth rate……….. 94
7.2.3 Cover crops pre-flowering biomass accumulation and coffee plant height ………..……. 97
7.2.4 Weed density and composition……….100
8 Conclusions……… 103
9 References………. 106
6 Summary
Cover crops are used worldwide, mainly for organic matter supply, erosion control and weed management. The use of live coverages in coffee, Coffea arabica (L.), plantations is a practice that was used in Costa Rica during the 1990s and was set aside due to the increased use of herbicides. Nowadays, coffee producers are seriously interested in reducing chemical input use and adopting alternative and more sustainable methods of control.
The objective of this study was to evaluate the establishment of different cover crop species in two sites located at different altitudes: the Fabio Baudrit Moreno Agricultural Experimental Station (EEAFBM, for its acronym in Spanish) in a middle-low area in Alajuela province (840 m a.s.l.) and a coffee plantation in a middle-high area in Heredia province (1,280 m a.s.l.). Both experiments were performed during the rainy season August - December 2019.
In the trial set at the EEAFBM, six legumes were investigated: Crotalaria juncea (L.), C. spectabilis (Roth), Vigna radiata (L.), Mucuna pruriens local cultivar (L.), Mucuna pruriens var. enana (L.) and Canavalia ensiformis (L.). As the plot was homogeneous and no blocks were needed, a completely randomized design was assessed.
The second field experiment was conducted in a 1-year coffee plantation (C. arabica var. caturra,
C. arabica var. catuaí and C. arabica var. obatà) with 2.3 x 1.1 m planting layout. The
experimental design was a random block with four replicates; six treatments were established to evaluate two legume species (Vigna radiata (L.) and Pisum sativum (L.)) and three different grass species (Brachiaria ruziziensis (Germ. & Evrard), Lolium multiflorum (Lam.) and Avena
sativa (L.)), plus the control (free growth of weeds). Results show that C. juncea tested at 840 m
a.s.l. managed to completely cover the soil (100 %) with a reduction in term of weed cover percentage up to 95 % in comparison with the control, 49 days after sowing (DAS). Among the grass species tested in the higher altitude site, A. sativa and B. ruziziensis were found to be the best adapted to that environmental conditions, despite their slow establishment.
In both trials, V. radiata provided complete soil cover (100 %), 35 and 77 DAS in Alajuela and Heredia province, respectively, and the highest difference between its biomass and that of the weeds (dry pre-flowering V. radiata biomass= 498 g m-2 while dry pre-flowering weed biomass= 24 g m-2 in EEAFBM; dry pre-flowering V. radiata biomass= 424 g m-2 while dry pre-flowering weed biomass= 40 g m-2 in Heredia).
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Chemical leaf analysis shows that V. radiata accumulated 156 kg ha-1 of N. Considering that a young coffee plantation needs around 150 kg ha-1 year-1 of N, this cover crop could be of great help to reduce the dose of chemical fertilizer normally used in coffee plantation.
As a conclusion, the use of V. radiata as live mulch species may provide a potential alternative strategy for weed management and soil fertility preservation in different environmental conditions. It is, therefore, an interesting specie to consider for future investigations.
8 1 Introduction
1.1 History and global importance of coffee
Coffee (Coffea spp.) is cultivated for its popular beverage obtained from the dried beans (Wilson, 1999) and is produced in more than sixty tropical countries, providing a livelihood for 25 million farmers around the world (Waller et al., 2007). It is the second most valuable commodity exported by developing countries (Talbot, 2004) with annual revenues of ∼$173 US billion dollars (FAO, 2015; Aristizábal et al., 2016). Approximately 70 % of the world’s coffee is produced on farms smaller than 10 ha (Jha et al., 2011) and over 125 million people rely on the coffee value chain for their livelihoods (TCI, 2016). In only a few centuries coffee has been adopted into worldwide cultures and nowadays the intensely aromatic beverage is both a delight and a daily essential for hundreds of millions of people; more than 2.25 billion cups of coffee are drunk every day (Ponte, 2002).
The two coffee species of commercial value, Coffea arabica L. (Arabica) and Coffea canephora Pierre ex Froehner (Robusta), both originate from Africa; the former has generally preferred taste qualities (linked to the low caffeine percentage and the aromatic volatile aldehydes presence), while the latter exhibits higher yield and pest resistance (Wintgens, 2004; ITC, 2012). Arabica coffee dominates global coffee landscapes, accounting for about 70 % of the world’s coffee production (Figure 1) (TCI, 2016).
Fig. 1 Global distribution of coffee beans producer countries. This map shows areas of coffee cultivation by type of coffee: r: Coffea canephora, a: Coffea arabica and m: both the varieties. Source: https://thatsaromacoffee.com/coffee-beans-producing-countries
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The primary center of origin and genetic diversity of C. arabica is Ethiopia, which is recognized as its oldest exporter in the world (Waller et al., 2007). Coffee begun to be grown in other parts of the world, such as Asia, Europe and India in early 1600s and later in the United States of America (ICO, 2011). By the latter half of the 1800s, coffee plantations of both Arabica and Robusta flourished throughout the American tropics, and by the 1990s coffee cultivation dominated more than 11.1 million hectares of tropical landscapes, with an average yield of 543 kg ha-1 (FAO, 2014).
Although the global area decreased to 10.2 million hectares between 1990 and 2010, production still climbed 36 %, which is evidence of an overall intensification in several key countries (Brazil and Colombia), coffee abandonment in others (Burundi and Kenya), and the rapid expansion of high-yield coffee in new countries (Vietnam and Indonesia) (FAO, 2014). In places where the coffee area has declined, such as Costa Rica and Ecuador, the expansion of high-yield agriculture has caused a decrease in coffee prices, which has, in turn, resulted in the abandonment of marginal agricultural lands (Aide and Grau, 2004; FAO, 2014) in combination with increased land prices due to urbanization.
Currently, the largest coffee producers are Brazil, Vietnam, Colombia, Indonesia, Honduras, Ethiopia and India, in that order, and almost a half of the coffee yield (∼8.5 million tons year-1) comes from just three nations: Brazil (34 %), Vietnam (17 %) and Colombia (9 %) (Figure 2) (ICO, 2018).
Fig. 2 Main coffee producer countries in the world. Source: Internacional Coffee Organization (ICO), 2018
Europe is the most important market for certified coffee in the world (Figure 3). The European market for specialty coffee offers opportunities for suppliers offering high-quality coffee (https://www.cbi.eu/market-information/coffee/trade-statistics/, last view 27/01/2020).
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Fig. 3 Global coffee consumption per region (in 1,000 tonnes). Source: ICO, 2019
On the world market, coffee is characterized by volatile prices (Figure 4) and changes in production levels, which have a direct impact on the incomes and livelihoods of the farmers who grow it (ICO, 2019).
Fig. 4 Coffee price in the New York Stock Exchange (since January 2014 to October 2018) expressed as USD/q (1 q= 45.36 kg). Source: Intercontinental Exchange (ICE), 2018
Coffee is very sensitive to changes in temperature or precipitation patterns (Gay et al., 2006). Climate models project a decrease in climate aptitude at lower altitudes and higher latitudes, with the probability of decreasing the total area suitable for coffee cultivation by up to 30 % by 2050 (Jha et al., 2011; Baca et al., 2014; Bunn et al., 2015; Ovalle-Rivera et al., 2015). Whereas climatic variability has always been the main factor responsible for fluctuations of coffee yields in the world, climate change, as a result of global warming, is expected to result in actual shifts
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on where and how coffee may be produced in future; by 2050 it is expected a total global coffee growing area reduction up to 50 % with an increased deforestation risk, biodiversity lost and spread of pests and diseases in wider areas (Figure 5) (TCI, 2016).
Fig. 5 Coffee farming in a changing climate. Source: The Climate Institute, 2016
Loss of agricultural nitrogen and phosphorus to air and water cause severe environmental and human health problems, including eutrophication of fresh and marine waters, the emission of greenhouse gasses, and the depletion of stratospheric ozone (Tilman et al., 2002, Townsend et
al., 2003, Diaz and Rosenberg, 2008). Some agroecological methods (intercropping, manuring,
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source of recycled phosphorus to minimize the need for mined phosphorus (Li et al., 2007, Conyers and Moody, 2009).
Short-term adaptation strategies, including improved farming practices and better post-harvest processing, have been put forward in response to the challenges faced by the sector. Longer-term strategies include capacity-building, improved monitoring of climate data, enhancing soil fertility, introducing or preserving different production models, and developing drought and disease-resistant varieties (ICO, 2019).
1.2 Coffee in Costa Rica
According to most of Costa Rican historians research works, the first seed of C. arabica var.
typica arrived in their country from Cuba in 1808 (Figure 6) (Castro, 2013). Coffee deeply
transformed Costa Rica geography and led to the construction of railroads, first to the Atlantic Ocean and then to the Pacific. No other crop has had a similar or equally complex impact on the landscape, except perhaps for bananas grown in the enclaves of transnational companies (ICAFE, 2019).
Fig. 6 Coffee harvest in Costa Rica in the late 1800s. Source: Gamboa et al., 2016
Several factors favoured the establishment of the "golden grain" in Costa Rica. Primarily, the agro-climatic conditions that in many areas of the country are characterized by highly fertile volcanic soils, high altitude, warm temperatures that stay relatively constant throughout the
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year, and distinct wet/dry seasons, which have been very advantageous for coffee cultivation (ICAFE, 2019). Costa Rican coffee is 100 % Arabica, mainly of the varieties Caturra and Catuaí, which produces a grain of higher quality and a cup with better organoleptic characteristics: pleasant, aromatic and fine. Since 1989, the planting of Robusta coffee is prohibited by law because of its inferior quality (ICAFE, 2019).
Coffee landscapes in C. arabica Costa Rican producing zones consist of a variety of micro-areas (Smith, 2018). The advanced technology that the Costa Rican coffee producer has used for more than 200 years has allowed him to adapt the plantations to the characteristics of each area. Today, Costa Rican coffee is grown in 8 production areas: Brunca, Turrialba, Tres Ríos, Orosi, Tarrazú, Valles Central and Occidental and Guanacaste (Figure 7) (ICAFE, 2019).
Fig. 7 Coffee growing regions in Costa Rica. Source: Roblesabana Coffee, 2018
Coffee trade with Europe consolidated in the 1840s; the first European coffee consumers were the English and the Germans (ICAFE, 2019). Nowadays, Costa Rica is the 13th largest producer of coffee in the world, with production around 1.56 million 60 kg bags of coffee in 2017-2018 harvest year (Figure 8) (ICO, 2018).
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Fig. 8 List of the main coffee production countries, considering the thousand 60 kg bags of coffee in ten harvest years, since 2008/09 to 2017/18. Source: ICO, 2018
Coffee processing and sales in Costa Rica are regulated through the “Coffee Law” (Law n. 2762), which was adopted in 1961 (ICAFE, 2017). The law contributed significantly to consolidate a production model, unique in the world, which eliminated intermediaries. The Costa Rican government established a non-governmental agency called “Instituto del Café de Costa Rica” (ICAFE) to implement and enforce the provisions of the Coffee Law. All coffee sales are
registered and must be approved by ICAFE (Dragusanu and Nunn, 2018). In 1977 the Tropical Agricultural Research Center for Research and Training (CATIE, for its
acronym in Spanish) was founded. This is an international institution focused on natural resources management, conservation and sustainable use. It currently houses one of the world’s most important known botanical collections of coffee, with more than 15 species and 600 varieties registered. This collection is a living laboratory of genetic diversity; studies of wild and cultivated genotypes offer enormous potential for the production of coffees with greater resistance to disease and unparalleled flavour (https://www.catie.ac.cr/, last view 20/01/2020). Although coffee is no longer the main agricultural export of the country, it remains a leading agricultural commodity. According to the ICAFE, there are around 41,300 coffee growers, mostly composed of small-scale ones, producing roughly over 2 million coffee bean “fanegas” per year (ICAFE, 2018). “Fanega” is a standard unit of volume used to measure coffee in Central America; it corresponds to 400 liters (~250 kg). These small-scale farmers are traditionally organized in
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agricultural cooperatives, in order to receive better prices for their product and cheaper access to technical assistance, as well as other benefits (Naranjo Barrantes, 2019). Since 1943, when the “Còdigo de trabajo”, the first legal provisions in terms of cooperative associations to regulate relations between producers, processors and exporters, was promulgate, cooperatives in Costa Rica have largely developed with State support, and control much of the coffee export. (Sánchez Boza, 2018). Cooperativism is important in the Costa Rican culture and economy: 37 % of the economically active population is directly or indirectly related to a cooperative. Even today, the beneficiaries of the cooperative are almost the only ones who use an agronomic engineer to assist the associated farmers and 40 % of the national harvest is still processed in a cooperative (Huaylupo Alcázar, 2013; Snider et al., 2017).
1.2.1 Production systems
Costa Rican coffee producers primarily depended on traditional practices in farm management, which were developed over centuries and relied heavily on manual labour (Sick, 1999). The farm was maintained as an agroforestry system consisting of a dense overstory of diverse tree species – with coffee planted in the understory – and other plants carpeting the ground. However, since the 1980s, Green Revolution technologies, such as the use of improved seed varieties, chemical fertilizers, irrigation and pesticides, have become widely embedded in the culture of coffee farming in Latin America, Costa Rica included (Rice and Ward, 1996; Rice, 1999). This was the result of three coinciding factors: the widespread infestation of a fungal rust disease (Hemileia
vastatrix), the introduction of neoliberal economic policies and institutional links to bilateral aid
agencies, such as the US Agency for International Development (USAID), which in 1978 launched a regional Coffee Improvement Project to industrialize coffee production (Hernandez Navarro, 1995; Rice, 1999). These changes in farming practices have been encouraged by public policies, especially between the 1940s and 1960s, that supported the development of large plantations owned by political and economic elites and foreign investors (Italians, Germans, North Americans, Britons, etc.). In only 20 to 30 years, traditional management practices in coffee farms were replaced by modern techniques, which included rows of coffee plants fully exposed to sun without an overstory of trees and bare ground between rows of trees. Since the 1980s, most coffee production has been converted to a high yielding “technified” monocrop in which coffee is grown with minimal shade cover and intensive application of agrochemicals, a system that was pioneered in Costa Rica (Adams and Ghaly, 2007; Rice and Ward, 1996). It should also be considered that mechanization is difficult to implement in Costa Rica because of the topography; coffee plantations are generally located in slope mountainous areas, and manual labour is still mainly used. Conventional, intensively managed coffee plantations are currently
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facing environmental challenges. The use of shade trees and the organic management of coffee crops are welcome alternatives, aiming to reduce synthetic inputs and restore soil biological balance (Sauvadet et al., 2019).
1.2.1.1 Coffee-based agroforestry vs full sun plantation
C. arabica is a shade-adapted species (Da Matta, 2004) that is now cultivated from monoculture
plantations under full sun exposure to a wide range of agroforestry systems (AFSs), including monospecific shade systems, other AFSs with diversified shade trees, and even complex forest-like agroforests (Figure 9) (Avellino et al., 2018).
Fig. 9 Gradient of complexity in coffee-based agroforestry systems. Source: Avellino et al., 2018
Between 2000 and 2009, coffee-growing regions in Costa Rica experienced a 50 % loss of shaded coffee (and shade trees) in the process of conversion to sun coffee, pasture, or other crops (Figure 10) (Bosselmann, 2012). The link between coffee cultivation and deforestation was highlighted by World Wildlife Fund (WWF), which showed that of the 50 countries with the highest rates of deforestation, 37 are coffee producing coffee (Bertrand et al., 2019).
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Fig. 10 Distribution of coffee production and percentage of the cultivated coffee area managed under different shade levels. Diverse shade has a closed canopy > 40 % with 10 or more species of shade trees; scant shade has a canopy cover between 1-40 % and 1 or 2 species of shade trees; sun coffee has no shade in the production area. Source: FAO, 2014
A new modality for agroforestry coffee cultivation, consisting of providing a payment based on the acreage of the agroforestry coffee system, was introduced in 2011 and is now accessible by coffee growers (https://www.fonafifo.go.cr/es/servicios/actividades-y-sub-actividades/, last view 29/12/2019). Coffee cultivated under full-sun conditions relies on chemical inputs: synthetic fertilizers, herbicides, fungicides and insecticides. Farmers are directly exposed to chemicals and the surrounding communities are also affected by residues (Bertrand et al., 2019). Some downsides of coffee full sun monocultures include decrease in the longevity of coffee plants (Chaves et al., 2012) as well as increased soil erosion (Lin, 2010).
According to the topoclimate, a coffee grower has to determine a suitable combination of practices where microclimatic conditions and resource use are optimized to reduce the impact of the injury profile on coffee production (Figure 11) (Allinne et al., 2016).
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Fig. 11 Conceptual flowchart of intercorrelationships between (1) cropping practices and the production system, (2) and (3) the production system and the provision of ecosystem services and (4) cropping practices and the provision ecosystem services. The lower box matches to the detailed upper box. Source: Allinne et al., 2016
The expected rise in temperatures could make Arabica coffee production areas at low altitudes unsuitable for production, considering that her best production is achieved at 18 to 22°C, a dry period of three months is needed in order to flower properly and extreme temperature can cause flowering abortion (Table 1) (Magrach and Ghazoul, 2015; Hameed et al., 2018). Moreover, a consequent decrease of overall land available to cultivate this crop could then increase pressure on protected areas (Jha et al., 2014).
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Tab. 1 Direct and indirect effect of extreme or unusual meteorological events on the coffee Arabica. Source: Hameed et al., 2018
The re-introduction of shade trees in full sun coffee plantations is seen as a way of mitigating these changes by moderating diurnal temperature variations of coffee leaves. Furthermore, has to be consider that on one tree in the rain forest houses up to 200 different plant and animal species, to move a single one of these trees means to disrupt hundreds of species (Smith, 2018). There are several benefits in planting shade trees in coffee, such as regulation or support of various ecosystem functions like pest control or nitrogen cycling (Torquebiau, 2000), reduction of topsoil erosion on steeper slopes, soil organic matter increase (litterfall), weed growth reduction, less competition with the main crop for moisture and nutrients, alkaloids and aromatic compounds formation in the beans, which contribute to the production of a good quality coffee (Wintgens, 2004).
Coffee-based agroforestry systems represent agroecological options of great interest, combining the cultivation of quality coffee with other productions, diversifying in this way not only the producers’ income sources but also the diets of their families. In Costa Rica, Erythrina
poeppigiana (Walp.) O.F. Cook (Fabaceae) is a popular species for providing shade in coffee
plantations (Budowski and Russo, 1997). As a leguminous species, it fixes N by capturing atmospheric N2 in the form of organic compounds in root nodules (Nygren and Ramírez, 1995). To attain the objective of increasing the presence and diversity of trees in plantations, others
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common associated trees are Terminalia Amazonia (J.F. Gmel.) Exell (Combretaceae), a timber species (Rossi et al., 2011) and Inga laurina (Sw.) Willd. (Fabaceae), an excellent shade, as well as fixing atmospheric nitrogen provider (Haggar et al., 2011). Bananas (Musa spp.) is also frequently used as shade in coffee plantations across Central America, due to quickly-established, easy-to-manage, shade for coffee provisions (Staver et al., 2013).
An adequate layout of coffee-growing agroforestry systems with service trees (E. poeppigiana), combined with timber trees (T. Amazonia) (densities not more than 100 trees ha-1 with 10 years) allow a positive balance concerning carbon emission trading, and particularly the quantities sequestrated exceed 100 t CO2 eq ha-1 (De Melo et al., 2013).
However, trees can also inhibit such ecosystem services, for example through competition with the main crop for light, water and nutrients (Van Noordwijk et al., 2015), or provide dis-services, such as creating more favorable conditions for pests or diseases (Zhang et al., 2007). Furthermore, negative effects include costly tree trimming and more difficult field management (Cirad, 2013). The productivity of coffee-based agroforestry systems is lower by 30 % than that of full-sun systems (Vaast et al., 2005). One reason for this situation is that new varieties cultivated in such systems were bred for full-sun intensive systems and are thus not adapted to agroforests (Bertrand et al., 2011; Van der Vossen et al., 2015). The integration of trees in the cropping system, and the modalities of tree management, must therefore be carefully examined in terms of their impact on both farmers economic costs and ecosystem services concerned (Meylan et al., 2017).
1.2.1.2 Organic coffee
Intensive agrichemicals use and dependence on increasing amounts of it pose problems not only for the health of the local environment, farmers and their families, but also for the financial viability of the farm. At the same time that costs for chemical inputs have increased, the coffee selling price offered to farmers has decreased, creating smaller profit margins, and forcing a number of small-scale farmers, the majority of coffee farmers in Costa Rica, to give up their production (Wintgens, 2004). Even if, as a result of using more labor to manually control weeds, scale farmers rely on smaller quantities of herbicide, it has been demonstrated that small-scale farmers mis-use and overuse agrichemicals (Matteson et al., 1993; Palis, 1998; Matteson, 2000; Bernard and David, 2001; Fan, 2001; Pontius et al., 2002; Pretty, 2005). This literature identifies the following reasons: risk-adversity, poor knowledge on proper and effective use of agrichemicals and inefficient equipment.
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Following the crisis of coffee prices that began in the late 1990s, strategies were put in place by the private sector to promote and enhance the environmental and social quality of this product by setting standards for its production and by creating labels to certify compliance with them (Soto and Le Coq, 2011). Consequently, the production of “organic” coffee saw a huge increase starting in the 2000s, partly due to better prices, with the organic price premium helping to offset, in case of low prices, the shortfall resulting from lower productivity. Organic plantation systems use denser and more diverse shading to help control pests, diseases and weeds. Many other practices are also adopted, such as foliar applications of elicitors of natural plant defence mechanisms and microorganism cultures sourced from forests (Wintgens, 2004).
In order to qualify for certification as organic coffee, the withdrawal of agrichemicals alone is not enough: the most important aspect of organic coffee classification is the sustainability of the production cycle for the maintenance and improvement of soil chemical and biological properties and physical structure (Wintgens, 2004). In that logic, eco-certification may help to significantly reduces chemical input use and increases adoption of some environmentally friendly management practices in developing countries, where growing and processing high-value agricultural products, as coffee, often entails deforestation, soil erosion and agrochemical pollution (Blackman and Naranjo, 2012).
In addition to organic one, other labels linked to sustainability have been created for the coffee sector, which often combine environmental and social standards within the production chains: Fairtrade (established in 1988), Rainforest Alliance (the first agricultural certifications in Central America, first for banana, then for coffee in 1995), Smithsonian’s Bird Friendly coffee (established in 1996) and finally UTZ Certified (originally Utz Kapeh, created for coffee in Guatemala in 2002) (Méndez et al. 2010; Fair Trade Foundation, 2012). A new integrative approach, the “Business driven” agroforestry cluster is promoted in Central America and comply with strict specifications concerning: a terroir + agroforestry practices (UTZ and/or Rainforest certified) + fully mastered post-harvest processing + a certification + 100 % traceability (Bertrand et al., 2019).
Often, for the small producers, the contracting and management of these labels is carried out by cooperatives, which maintain registers and communicate with the certifiers, as an intermediary between certification companies and small producers, fulfil a role that producers do not have time to assume. The cooperatives are also in charge of verifying that agricultural and social practices correspond to the labels’ requirements, and, above all, of training producers in these practices (Quispe, 2007).
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Organic, eco-friendly, and fair trade coffees, collectively referred as sustainable coffees, fill a market niche that is not only rewarded with a premium price but can also provide other superior benefits that help producers improve their sustainability, included considerable direct economic impact measurable in millions of dollars (http://www.ico.org/, last view 21/01/2020).
1.2.2 “El beneficiado”
During the coffee harvest season, which generally lasts from December to April, coffee farmers deliver the cherries (Figure 12) to a local mill, the “beneficio”, for processing, within 24 hours from the harvest. Coffee harvest is traditionally done using the “cajuela”, also called “canasta” (Figure 13), which is consider the unit of volume used to pay for the worker. Its dimension is fixed by a law since 1886, and it corresponds to 20 litres (ICAFE, 2018).
Fig. 12 Coffee bean (cherry) structure. Source: Wintgens, 2004
In Costa Rica, wet process (also called “washed”) is the typical method for processing. Exocarp and mesocarp of the coffee cherry are removed from the coffee beans by soaking in water. As it sits in the water, the pulp ferments, improving the flavor and acidity of the final coffee. In dry processing (also called “natural”), the coffee cherry is sun-dried (the process takes 7 days) or mechanically, which reduces the optimum drying point time (12 % humidity) to just 24 hours. Then the beans are separated from the pulp; this increases the fruitiness of the final coffee (ICAFE, 2019). Each method of processing creates different kinds of essence that can be prized in this high-end market, although both kinds of processing can create off flavors if not done with care (Smith, 2018). “Honey” processing combines features of wet and dry ones and the final product has the fruitiness of dry processing and the brightness of the wet one; in it, the wet process begins, but some amount of the pulp is left on the beans. The beans are then dried with
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the pulp on them, as in the dry processing method. If done right, this produces coffee that has the fruitiness of dry processing and the brightness of wet processing (Smith, 2018).
Figure 13 On the top an indigenous woman from Brunca region with traditional “canasta”; on the left, a producer depositing his coffee in the cajuela (20 litres); on the right, the other unit of measurement used in the beneficio: the “fanega” (400 litres). Source: ICAFE, 2016
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The resulting product (“el beneficiado”) is called parchment coffee (green coffee). Foreign bodies and defective beans are rued out from a batch of coffee. The mills then sell the green coffee to exporters and domestic roasters (Castro, 2013; Dragusanu and Nunn, 2019).
Conventionally, pulp that was separated from the bean was repurposed as organic fertilizer. But this practice had a large environmental impact due to high emissions of methane gas. Currently, in many mills, pulp and detached and dehydrated husks are compacted into fuel. This fuel is used as an alternative to firewood in the coffee-drying process (ICAFE, 2016).
1.3 The market: Costa Rican coffee excellence
Costa Rica began producing coffee since the XIX century. Until the 1970s, the country´s economy heavily depended on this product; however, the economic importance of coffee has diminished over time (Mata and Ruiz, 2019). Nowadays, coffee is the third most important agricultural export product in Costa Rica, after bananas and pineapples; it represents 3 % of total exports of the country (Costa Rican Export Promoting Agency PROCOMER, 2017).
In Costa Rica, the marketing of coffee is in the hands of the private sector; however, the State maintains supervision and control through the Coffee Institute of Costa Rica (ICAFE) (Hopfensitz and Miquel-Florensa, 2017). Seven major actors can be identified in the structure of the global value chain (GVC) for the mainstream-coffee market: farmers, processors, export agents, global traders, roasters, retailers, and consumers (Figure 14) (Mata et al., 2016).
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Costa Rican coffee is recognized for its quality worldwide. Quality in coffee is a complicated item, based on lack of defects, how the coffee tastes, and certification systems. Quality in the specialty coffee market strongly depend on the landscape-country of origin, named “geographical regions” within it, and on the altitude at which the coffee was grown. This explains why the high-value coffee market has come to be focused on small-batch coffee with distinctive taste tied to an idea of “terroir”. Coffee labelled with the names of specific farms or farmers carries with its messages about the kind of coffee it is and the experience that they will have in drinking it (Smith, 2018).
In auctions at the Cup of Excellence, a competition held in several countries to reward coffee quality, Costa Rican coffee attracts buyers from the U.S., Japan, Korea, Australia and many other markets. These buyers compete annually to purchase the best lots of Costa Rican coffee, and bids reach two, three or four thousand US dollars per quintal (46 kg bag), an undoubtedly high price considering that a quintal of excellent quality coffee can be bought for 120-200 US dollars (ICAFE, 2019). In the 2018 edition of the Cup of Excellence one of the participating coffee samples in Costa Rica reached the extraordinary price of 300.09 US dollars per pound in the auction held as part of this international competition. This price exceeded the record of 130.20 US dollars per pound, previously obtained in 2017 by Brazil in this same competition (Mata and Ruiz, 2019).
The goal of the coffee sector in Costa Rica is to continue increasing the sale of grain in the markets of fine coffees; to maintain the strategy of “énfasis en calidad y no en cantidad” (emphasis on quality and not on quantity) always provide added value to coffee and increase participation in the local market with quality coffee (Figure 15) (ICAFE, 2019).
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Fig. 15 Evolution of the coffee price on the New York Stock Exchange (ICO). Sources: www.ico.org, www.fairtrade.net, www.icafe.cr
It should however be considered that coffee farmers received only 7 to 10 percent of the price paid by final consumers (ITC, 2012), even though it is widely recognized that the main determinants of coffee quality come from its cultivation and processing (Brown, 1991) that depends from value added by local, and not international, actors (Costa Rican coffee paradox). A handful of Costa Rican farmers have developed e-commerce site to sell their own roasted coffee. For example, the platform “crgourmetcoffee.com” is a web site under construction that has been designed and is going to be developped with the following principle: focus on the foreign market with coffee, a product in which Costa Rica excels. In this way, this platform is aimed at mitigating the coffee paradox, and thus encourage Costa Rican farmers that produce gourmet coffee to continue in the business (Mata and Ruiz, 2019).
27 2 The crop
Coffee is a major crop and an important income source for farmers in Central and South America. The genus Coffea belongs to the family Rubiaceae and covers approximately 70 species. The two main species of coffee tree cultivated worldwide are Coffea arabica (L.) and C. canephora var.
robusta (Pierre ex Froehner). C. arabica is an indigenous plant from the dry forests of the
highlands of the Horn of Africa, which is therefore adapted to certain conditions of altitude and forest shading (Wintgens, 2004).
Coffee is a perennial crop that can grow up to about 10 m tall when mature. The shape of the plant varies depending on the species and variety. All coffee trees consist of an upright main shoot (trunk) with primary, secondary and tertiary lateral branches (FAO, 2015). The development of the aerial parts of the coffee plant entails the lengthening of the vertical (orthotropic) main stem, called suckers at the developing stage and stems at the final stage. The successive growth of pairs of opposite evergreen leaves at each node (plagiotropic branches) are usually called primaries. Each serial bud headed by a “head of series” bud, are located on a primary and can develop into an inflorescence (flower) or into a secondary branch, which has a similar structure to the primary branch with serial buds that develop either into flowers or tertiary branches (Figure 16). If a secondary branch is cut or removed, another secondary on the same axil can replace it, so regeneration of secondaries on primaries is possible (FAO, 2015; Wilson, 1999; Winston et al., 2005). The “head of series” bud is the only one able to generate a primary plagiotropic branch whereas the four to six serial buds can generate either new suckers (orthotropic stems) or flowers (Ramìrez Rojas, 2017). No other bud in the same axil can grow into a lateral branch, which means that if such a branch is cut off, no lateral regeneration can occur on the node of a main vertical stem (FAO, 2015).
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Fig. 16 Coffee phenology: A, plant development; B, plagiotropic branch development of coffee. Source: De Oliveira Aparecido and de Souza Rolim, 2018
The coffee flower consists of a white five-lobed corolla, a calyx, five stamens and the pistil. The ovary is at the base of the corolla and contains two ovules that, if duly fertilized, produce two coffee beans.
The development of a serial bud into a flower bud is largely controlled by plant hormones, which are chiefly activated by photoperiodism and by a drop-in temperature. A normal inflorescence consists of four floral buds; for Arabica, the number of flowers per inflorescence can range from two to nine (Figure 17). Dormancy is usually broken by a sudden relief of water stress (rehydration) in the buds and/or drastic fall in temperature; the more severe dry season, the more intense the flowering (Wintgens, 2004).
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Fig. 17 Arabica coffee flowers. Source: ICAFE, 2016
In C. arabica, 90-95 % of the fertilization is carried out by the pollen of the flowers from the same tree (self-pollination). The time taken from flowering until the maturation of the coffee berries is 6-9 months (Ramìrez Rojas, 2017). As a general rule, with the necessary differences depending on the variety in question, the coffee plant takes approximately 3 years to develop from seed germination to first flowering and fruit production (Ramìrez Rojas, 2017). The fruit of the coffee tree is known as a cherry, and the beans which develop inside the cherry are used as the basic element for producing roast and ground coffee, soluble coffee powders and coffee liquor (Wintgens, 2004).
The root system of mature coffee consists of a central taproot growing to a depth of up to 1 m, axial roots that grow vertically downwards to a depth of 3 m and lateral roots forming a mat structure almost parallel to the soil surface at a distance of 1.2-1.8 m from the trunk (Coste and Cambrony, 1992; Winston et al., 2005) with in the upper 30 cm of soil (Winston et al., 2005; Waller et al. 2007). Moreover, feeder bearers of various length and distribution, and the root hairs are the main providers of mineral nutrition to the coffee plant (Figure 18) (Wintgens, 2004). Under mulch protection, the density of the superficial root system can triplicate, with a consequent increasing in coffee plant mineral nutrition (Wintgens, 2004).
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Fig. 18 Distribution of the roots system in a coffee plant. Source: Mavota, 1986 adapted by Wintgens, 2004 / FAO, 2005 / http://www.fao.org/3/AD219E/AD219E05.htm
To achieve high yields of quality coffee and avoid dieback, good young trees field management practices are essential. There are three key procedures to follow: protect from frost, control weeds and soil moisture and fertility maintenance (FAO, 2015). The use of annual food and cash crops living mulch cover, such as leguminous (Figure 19), interrow in young non-bearing coffee plantation, could partly compensates for the high investment cost of coffee establishment, reduces soil temperature (avoiding frost), smothers weed growth and supplies the soil with additional nitrogen (legumes) and organic matter when crop residues are turned back into the soil (FAO, 2015).
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Fig. 19 Established ground cover of Pinto peanut in coffee plantation. Source: FAO, 2015
2.1 Environmental requirements
The environmental factors of suitability for coffee cultivation are temperature, water availability, sunshine intensity, wind, type of soil and topography of the land (Wintgens, 2004). Natural stands of C. arabica are found on the high plateau of Ethiopia at 1,300-1,800 m of altitude above sea level, with annual rainfall of about 1,500-1,800 mm and average temperature ranging between 15-25°C (Wilson, 1999; Waller et al., 2007). Temperatures higher than 25°C cause reduced photosynthesis, leaf chlorosis, blossom wilting, defective fruit set and favour the development of coffee leaf rust (Hemileia vastatrix) and fruit blight (Cercospora). Low temperature, on the contrary, favour Coffee Berry disease, and cause a white/yellow discoloration of the leaves. With a total annual rainfall less than 1,000 mm, the first year vegetative growth of the plant and therefore the harvest of the following year is limited. On the other hand, excessive rains (more than 3,000 mm year-1) can generate erosion and make it difficult to sun-dry the crop with a consequent more difficult plant health control of the plantation (Castro, 2013). Wind can be harmful, generating physiological drawbacks like excessive evapotranspiration. The use of windbreaks is a basic precaution (Wintgens, 2004). Coffee plants prosper as well in alluvial and colluvial soils with a favourable texture as in volcanic formations. On the other hand, the depth of the soil (2 m) above any obstacle is most important. As the main part of the radicular system of the coffee tree develops in 30 cm of the upper soil layer, the physical properties of the topsoil have more influence than those of the deeper subsoil. Soil which are favourable to the coffee plant have a porosity of 50-60 % (micro and macro porosity), a mineral content of 45 % and the organic content around 2-5 %. As a general
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rule, suitable soils should not contain more than 20-30 % of coarse sand and 70 % of clay in the upper layers of 30-50 cm (Wintgens, 2004).
2.2 Agronomic requirements
A well-managed coffee tree can be productive for up to 80 years or more, but the economic lifespan of a coffee plantation is rarely more than 30 years (Wintgens, 2004). The average yield of a mature Arabica coffee plantation in Costa Rica is 23 fanegas per hectare, corresponding to 2,000-2,500 kg dry beans ha-1 (it should however be considered that green coffee yield strictly depend on the type of coffee variety) (ICAFE, 2019; Rolando Vasquez, Operations Manager at Las Tres Marias, personal communication).
In tropical regions where coffee is grown, soils are often acid and rich in iron and aluminium oxides and characterized by a low cation-exchange capacity (CEC). Then, usually the organic matter represents up to 80 % of the topsoil CEC where most of the feeder roots are growing. Therefore, conserving the quantity of main cations (K, Ca, Mg) is essential to improving plant nutrition and ensuring the sustainability of the coffee production (Wintgens, 2004).
Coffee exhausts the soil in which it is grown through extraction of soil nutrients and removal of harvested coffee beans (Winston et al., 2005). Each mature coffee plant takes around 30 kg of nitrogen (N), 3 kg of phosphorus (P2O5) and 35 kg of potassium (K2O) from the soil to produce 1 ton of green coffee beans (Figure 20) (Elzebroek and Wind, 2008; FAO, 2015).
Fig. 20 Nutrient uptake of a mature (10 years) coffee plant. Source: FAO, 2015
It is therefore necessary to supply additional nutrients to sustain coffee yields over time. Nitrogen is important for vegetative growth, phosphorus for bean production and root development for soil nutrient uptake and potassium for berry development and ripening (Figure 21) (Winston et al., 2005).
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Fig. 21 Essential macronutrients and their role in the coffee plant. Source: FAO, 2015
Two applications (May and August) of complete formula fertilizer (18 N - 2 P - 15 K), equivalent to 715 kg ha-1 (corresponding at 128.7 kg N ha-1, 14.3 kg P2O5 ha-1 and 107.25 kg K2O ha-1, total)
are normally used, supplemented by an application of a nitrogen source (NH4NO3) of 285 kg ha-1 (ICAFE, 2019). The first year after sowing, 140-150 kg N ha-1 are provided, with no
extra nitrogen source supplemented (ICAFE, 2014). 2.3 Main varieties in Costa Rica
The 1960s marked the end of the reign of the first coffee variety arrived in Costa Rica, called Typica, progressively displaced by the Caturra and Catuaí varieties, plus several others recently introduced, including Obatà, a high yielding, rust-resistant Brazilian variety (ICAFE, 2014).
C. arabica var. caturra (Fig. 22 Picture by Jessica Girardi)
Variety found in Minas Gerais, Brazil, possibly originated as a mutation of a dominant Bourbon coffee gene. Caturra (Figure 22) is characterized by low size, short internodes, thick trunk and little ramified, and abundant short lateral branches, with secondary ramification, which gives the plant a vigorous and compact appearance. With respect to Typica, the adaptability of this variety is
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very wide, particularly in terms of altitude, and it produce a denser concentration of fruit (Carvalho, 1993; ICAFE, 2018).
C. arabica var. catuaì (Fig. 23 Picture by Jessica Girardi)
Originally from Brazil, Catuaí (Figure 23) is the result of the crossing of Caturra by Mundo Novo (Mundo Novo is a mutation of Sumatra). It is of small size and short internodes although a little higher and wider than the Caturra. It produces a lot of secondary growth in the bands (palmilla) and therefore it shows a very high production. Although the red Catuaí is the most widely distributed in the country, there is also the yellow one, both maintain similar characteristics and qualities. Fruit does not fall off the branch easily, which is useful in areas with strong winds or rains (Carvalho and Fazuoli, 1993; ICAFE, 2018).
C. arabica var. obatà (Fig. 24 Picture by Jessica Girardi)
Originally from Brazil, Obatà (Figure 24) is the result of the crossing of Timor Hybrid 832/2 and Villa Sarchi CIFC 971/10; pedigree selection made by the Instituto Agronomico (IAC) of Sao Paulo State in Campinas in 2000, and brought to Costa Rica for commercial release in 2014 by ICAFE. It is of dwarf compact stature and large bean size. The optimal altitude is middle-high (700–1,600 m a.s.l.). The first production is expected at the third year after plant assessment; it shows a very high production, considering a plant density of 5,000-6,000 plants/ha (https://varieties.worldcoffeeresearch.org/varieties/obata-rojo, last view 01/02/2020).
35 2.4 Diseases and insect pests
The most common Arabica coffee pests in coffee-producing regions include leaf miners, mealy bugs and stem borers, while the main coffee diseases are caused by fungi, coffee leaf rust and coffee berry disease (Figure 25) (Wilson, 1999; Staver et al., 2001; Waller et al, 2007; Avelino et
al., 2018).
Fig. 25 Main Arabica coffee diseases and pests in coffee-producing regions and main organs affected. Source:Avelino et al., 2018
Coffee leaf rust (CLR), Hemileia vastatrix (Berkeley & Broome) is distributed in most of the coffee-producing countries of the world (Figure 26) and it is considered the main disease of C.
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Fig. 26 Geographic distribution of coffee leaf rust (CLR). Source: EPPO, 2014
While this disease kept a relatively low profile in Central America for decades (Avelino et al., 1999), it resulted in significant yield losses in 2012-2013, and become a driver of changes in the region’s coffee plantation systems. One of the reasons behind this increased damage from the disease may be climate change, since coffee and the coffee leaf rust agent, H. vastatrix, are both very sensitive to temperature (Avelino et al., 2015). Indeed, warmer temperatures affect both, the development of this fungus and the physiological state of the plant under environmental stress (Bertrand et al., 2019). An immediate outcome of the crisis was the development of the coffee genetic bank, with the rapid replacement of susceptible traditional varieties by resistant ones. However, the disease seems to have already started overcoming resistance, indicating that integrated management of coffee leaf rust, based on shading and nutrition, and especially on soil conservation, is needed (Avelino et al., 2006; Toniutti et al., 2017).
Mycena citricolor (Berk. & Curtis) Sacc. is the causal agent of American leaf spot disease (ALSD)
in coffee. This is a new encounter disease of coffee in Latin America. M. citricolor has a broad range of hosts, including shade trees used in coffee plantations as well as weeds (Granados Montero, 2015). When conditions are favourable (rainfall is abundant and homogeneously distributed in the year and temperatures are cool, yield losses in coffee plantations can be almost complete (Tab. 1) (Avelino et al., 2007, 2018).
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The coffee berry borer (CBB), Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae), is the main economic pest in coffee (Tab. 1), negatively impacting crop yields all over the world with losses surpassing more than US $ 500 million annually (Vega et al., 2015).
Disease Topography/Temperature Rainfall/Wetness Shade/Light Other factors
Coffee leaf rust (Hemileae vastatrix) Low-altitude disease: <1,400m a.s.l.; optimum temperature range 21-28°C High incidence when rainy season is humid enough, favoring infection, but interspersed with bright days, reducing uredospore wash-off Higher occurence under shade Higher severity and incidence on high-yielding coffee trees American leaf spot disease (Mycena citricolor) Medium-altitude disease: 1,100-1,550 m a.s.l.; high incidence in western-oriented slopes High incidence when the rainy season has no interruption Higher incidence under shade, particularly when provided by tall trees; raindrops of higher kinetic energy under shade trees may promote the dispersal of the heavy propagules Many hosts within shade trees and weeds of the coffee agroecosystem Coffee berry borer (Hypothenemus hampei)
Temperature and altitude directly affect the CBB life cycle; in agro-ecological zones with high temperatures (optimum temperatures ranging from 23°C to 25°C) and medium-low altitude (optimal range between 800 and 1,000 m a.s.l.) the life cycle is shorter so a greater number of insect generations can occur and therefore greater damage to the harvest
Humidity
generated by sporadic rainfall of the dry season
causes CBB emergence and migration; the maximum fertility was found at 90% and 93.5% relative humidity In dense shade coffee plantations, the populations of CBB are larger compared to full sun coffee areas; the arrangement of shade trees in coffee growing is very important because it influences the presence of the fungus parasite Beauveria bassiana Rivera (2000) recommends maintaining a cover of “noble” weeds that do not compete with coffee and that provide soil protection, in order to facilitate the survival of the beneficial fauna that attacks the CBB
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Tab. 2 Main environmental drivers of Arabica coffee diseases of primary importance on susceptible coffee trees, adapted from “Multiple-Disease System in Coffee: From Crop Loss Assessment to Sustainable Management” by Avelino et al., 2018 and “Efecto de los sistemas agroforestales del café y del contexto del paisaje sobre la broca (Hypothenemus hampei (Ferrari) con diferentes certificaciones en la provincia de Cartago Costa Rica” by Romero Gurdian, 2010.
Pest and disease control is integral part of coffee management and represents a significant part in production costs, especially for small holder farmers who do not benefit from economies of scale compared to large scale owners (Wilson, 1999; Karanja, 2002). Introduction of legume cover crops in coffee may improve pest and disease management in coffee farms especially if the legumes used break disease and pest cycles (Snapp et al., 2005). For example, Canavalia spp. and Mucuna spp. have repellent and insecticidal properties (McIntyre, et al., 2001). Soil management measures such as mulching and planting cover crops may affect crop health by improving soil fertility and by directly acting on pest and disease populations (Table 2) (Schroth
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3 Weed as accompanying vegetation: when and how to manage it
Any plant out of place, according to the anthropocentric point of view, and which negatively affects the productive system is considered weed (Sanderson, 2011). However, this definition may lead to an erroneous consideration of some plants and cause their indiscriminate control (Zimdahl, 2017; 2018). Currently, the term “weed” referred to the spontaneous companion plants of the crops, starts to be taken in consideration also by professionals, particularly in tropical areas (De Melo, 2010). It is clear from the extensive agro-ecological knowledge that in the understory of the coffee plantations and other crops the natural plants are not only harmful and even those commonly referred to “weeds” can perform important ecological functions if properly managed, such as ecological diversity implementation; site condition indicators, in particular aspects related to fertility, degradation and humidity level; developing a good coverage, contributing to improving soil structure allowing better aeration, water infiltration and nutrient recycling; insecticidal, fungicidal and nematocidal activities, as well as insect attractivity and repellence (De Melo, 2010). Last but not least, between the companion vegetation we can find ornamental, honey, medicinal, forage and human consumption species (Table 3).
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Tab. 3 Potential use of weeds for pest and disease management in coffee. Note: CO= Colombia; CR= Costa Rica; HO= Honduras; GU= Guatemala. Source: De Melo, 2010
While in temperate regions nutrients, like nitrogen, are abundant in soil (90-95 %), in tropical ones they are mainly present in plant biomass (75-80 %), otherwise they would be lost by runoff and leaching, because of the high rainfall. To maintain and stimulate fertility, therefore, in temperate areas it is important to maintain/increase the nutrient content in the soil, while in tropical regions to achieve the above objectives, the production of more biomass is needed (professor Adolfo Soto Aguilar (UCR), personal communication). In tropical regions, infiltration rate and hydraulic conductivity are the most important soil physical properties affecting soil water erosion (Araujo-Junior et al., 2015). The weeds between coffee rows play an important role in water dynamics by intercepting raindrops impacting on soil surface, which probably reduces surface crusting and maintains a constant infiltration of water for one hour. On the other hand, along coffee rows, weeds are controlled to provide the maximum growth and
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development of the coffee plants. By indiscriminate exclusion of the weeds there is a direct impact of raindrops on the soil surface, which reduces infiltration sharply due to the formation of surface crusting (Wintgens, 2004). Where innocuous, non-invasive broad-leaf plants, such as
Bidens pilosa L., Commelina diffusa Burm. f. and Hyptis atrorubens Poit. (De Melo, 2010), are
present, they should be retained as a soil protection measure due to the ecological services provided.
Of the known plant species, about 250 are considered competitive for agriculture main crops (Memon et al., 2003). Considering the life cycle, weeds may be classified as annual (herbaceous and grasses), biennial or perennial depending on their origin, habitat, morphology and biological characteristics (Hakansson, 2003). Perennial weeds live for three or more years and produce seeds and extensive root system which may include underground rhizomes, tubers, or bulbs (Hakansson, 2003) which sprout again when not fully uprooted or destroyed making them difficult to control (Coffee Research Foundation, 2003).
Weed richness in coffee plantations is very wide and it is necessary to continue exploring to make the list as complete as possible in each country and coffee growing zone. For the case of Costa Rica, Mata (1993), until 1984 listed a total of 251 species of herbs found in coffee plantations, representing 45% of the total number of plants registered in the country according to Alan et al. (1995). In the case of Colombia, Gómez and Rivera (1995) described about 170 weed species associated with coffee cultivation (Table 4) (De Melo, 2010).
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Tab. 4 Botanical family of common weeds in Centro and South America coffee plantation. Source: De Melo, 2010
In Costa Rican coffee plantations, the most dominant weed families are Commelinaceae,
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“Weed management” is a term used to describe activities and modifications of measures or conditions in the cropping system with an intention of influencing or reducing weed populations (Hakansson, 2003). It is one of the most intensive practices in different production systems in tropical regions, having high impact on agricultural productivity, on the environment and on economic viability of crop production (Araujo-Junior et al, 2015). Uneffective weed control can jeopardize coffee plants growth, which could result in the hand in low yields and low income (Hincapié-Gómezand and Salazar- Gutiérrez, 2007).
One of the major challenges in “weed control” is reducing the number of propagules (seeds and/or vegetative organs) in the soil or their regeneration after weeding (Hakansson, 2003; Kelton et al., 2011). This would reduce the adaptation fitness of weed species, making them less persistent in the fields from year to year (Clay et al., 1990; Kelton et al., 2011). The cropping system, cultural practices and weed control methods adopted can determine this soil “seed bank” (Hakansson, 2003; Kelton et al., 2011). Herbaceous species diversity can be an indicator of the effects of different management practices on plant diversity. The amount of light that reaches the understory, the availability of nutrients in the upper layers of the soil and the physical structure of the soil also affect their growth (Montagnini et al., 2011).
Several weed species can threaten the success of the coffee crop. Perennial grasses and sedges (Cyperaceae) present the most serious problems since they are much more difficult to control and offer much greater competition to the coffee than the dicotyledonous, which grow mostly in the rainy season. Some species, for example Amaranthus spinosus L., Cyperus rotundus L. (Samad et al., 2008), Bidens pilosa L. (Tseng et al., 2003), Ageratum conyzoides L. and Ipomoea spp. (Liu et al., 2015), also secret toxic (allelopathic) substances through their roots, which block the mineral assimilation in the coffee plant (Montagnini et al., 2011).
Weed management in coffee plantation conducted almost exclusively through chemical control has caused negative impacts. Herbicides combined with tillage is inadequate for weed control in tropical conditions because of negative impacts on soil quality directly related to hydric erosion (Carvalho et al., 2007) and soil compaction (Pais et al., 2011). The inappropriate and excessive use of post-emergent herbicides can damage the crop, whilst the soil crusting due to intensive tillage, such as rotary cultivation, contributes to cause surface erosion and lack of vegetation cover, thus promoting also the reduction of organic matter (Alcântara et al., 2007; 2009).
A key to effective and more sustainable weed management is a holistic approach and must include a combination of tactics and practices in order to recognise “hierbas competidoras y
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hierbas buenas” and successfully and economically reduce the potential negative impacts inherent to competitive weeds incidence (Figure 27) (Boydston, 2010; De Melo et al., 2013).
Fig. 27 Weed classification based on competition rate and correlated good management practices. Source: De Melo et al., 2013
Integrated weed management systems and cover crops used as a green manure can be useful in tropical regions, since it may protect also soil against degradation processes, such as compaction and erosion. The purpose of it is to keep weeds below their economic thresholds while minimizing negative impacts on the environment (Coffee Research Foundation, 2003; Araujo-Junior et al, 2015).
Nowadays, weed management in Costa Rican coffee farms includes: manual practices, such as chopping, or mechanical one, like shovelling; herbicides applications; shade trees, cover crops, intercropping and mulching techniques (Sanderson Bellamy, 2010).
45 3.1 Mechanical control
There are several direct mechanical control methods, including mowing, cultivation, hoeing, flaming, mulching, and hand weeding. In particular, mowing, cultivation and hoeing inevitably product various splits of rooting material (rhizomes, stolons, corms) of perennial weeds and their dispersion in the cultivated layer of soil (Wintgens, 2004). In the coffee-growing countries of Central America, the topography does not allow the use of weeds cutting machines; manual instrument are used hanging from the body of the person operating (De Melo et al., 2010).
3.2 Chemical control
Chemical control mainly consists of using pre and post-emergence herbicides and soil fumigants. Herbicides can be classified into several ways, based on their weed control spectrum (selective or non-selective), labelled crop usage, chemical families, mode of action and application method and timing (Lingenfelter and Hartwig, 2007). For example, based on mode and site of action, herbicides are grouped according to contact and systemic ones. Contact herbicides kill only the plant parts contacted by the chemical, whereas systemic herbicides are absorbed by roots or leafs and translocated throughout the plant (Lingenfelter and Hartwig, 2007).
According to Hincapié and Salazar (2004), the use of herbicides for weed control is one of the major global problems affecting sustainable production systems, as the indiscriminate use of chemical herbicides can lead to soil erosion due to the elimination of natural cover that leave the soil totally exposed to atmospheric agents, contamination of water sources and damage the health of people in rural communities (Helander et al., 2012).
In Costa Rica the agrochemicals abuse/inappropriate use is a huge topic. The two dominant herbicides used in coffee production in the country are glyphosate (53 %) and paraquat (28 %) (Figure 28).
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Fig. 28 Agrichemicals, expressed as amount per hectare, used in three Latin American countries (up); herbicides for coffee plantation registered in Costa Rica. Glifos= glyphosate; Metsul= metsulfuron-metil; Paraq= paraquat; Oxyf= oxyfluorfen; Triaz= terbutilamina and Antigr= others (bottom). Sources: http://www.fao.org/in-action/agronoticias/detail/es/c/508248/ (2011); Servicio Fitosanitario del Estado (2017)
The water-soluble, non-selective and post-emergent herbicide paraquat kills plants on contact via chemical reactions (Taiz and Zeiger, 2002; Syngenta, 2005). Its use has been restricted in many countries and regulated in Costa Rica, due to its high toxicity, prolonged persistence in the environment and because it is easily absorbed by the human epidermis (Sanderson, 2011). On the other hand, although glyphosate is more expensive than paraquat, farmers use it because it completely kills the weeds and some formulation have been created in Costa Rica (professor Adolfo Soto Aguilar (UCR), personal communication).
Clearer and additional information about weed-herbicide dynamics and the best way to applicate it, in order to avoid herbicide-crop contact (Figure 29), may play a role in reducing or allaying small-scale farmers’ risk-adverse thinking and behaviour. Furthermore, it is noteworthy that small-scale farmers’ unexpectedly use high level of herbicides as the result of an underlying pressure among farmers to demonstrate a competitive image. More information about alternative management options and research in partnership with farmers with regards to this topic would allow them to make more conscious – informed -responsible decisions regarding production management (professor Adolfo Soto Aguilar (UCR), personal communication).
