Shade effects on yield across different Coffea arabica cultivars — how much is too much? A meta-analysis

Abstract

The coffee research community has maintained a long ongoing debate regarding the implications of shade trees in coffee production. Historically, there has been contrasting results and opinions on this matter, thus recommendations for the use of shade (namely in coffee agroforestry systems) are often deemed controversial, particularly due to potential yield declines and farmers’ income. This study is one of the first demonstrating how several Coffea arabica cultivars respond differently to shade with respect to yield. By standardising more than 200 coffee yield data from various in-field trials, we assembled the so-called “Ristretto” data pool, a one of a kind, open-source dataset, consolidating decades of coffee yield data under shaded systems. With this standardised dataset, our meta-analysis demonstrated significant genotypic heterogeneity in response to shade, showing neutral, inverted U-shaped and decreasing trends between yield and shade cover amongst 18 different cultivars. These findings encourage the examination of C. arabica at the cultivar level when assessing suitability for agroforestry systems. Comparison of productivity is also encouraged across a range of low to moderate shade levels (10–40%), in order to help elucidate potential unknown optimal shade levels for coffee production.

Alternative plant protection strategies for tomorrow's coffee

“…The often full‐sun cultivated Coffea canephora showed significant intraspecies differences in yield when grown under moderate to high shade environments (41%–65%) (Piato et al, 2020). The possibility of a maintenance of, or improvement in, coffee yield under AFS‐like conditions, at shade lower than 40% (Figure 2) has also been revealed by standardization and analyses of historical C. arabica yield data (Koutouleas, Sarzynski, Bertrand, et al,2022). However, many coffee yield data related to high shade environments (above 40%) present a need to explore low to moderate shade levels more extensively.…”

“…The use of shade should be tailored to the on‐farm needs and pressures of the coffee plantation (Avelino et al, 2007; Koutouleas, Sarzynski, Bertrand et al, 2022; Koutouleas, Sarzynski, Bordeaux, et al, 2022; Vaast et al, 2006, 2010). The diversity and abundance of biota within a coffee‐AFS can provide protective services against some pests and diseases for the coffee farmer (Moreaux et al, 2022; Perfecto et al, 1996; Schelhas et al, 1997; Solano & Cruz, 2017).…”

“…Shade is a contentious issue surrounding the use of AFS for coffee due to its implications on coffee productivity (Koutouleas, Sarzynski, Bertrand, et al, 2022 ; Koutouleas, Sarzynski, Bordeaux, et al, 2022; Perfecto et al, 2005; Sebuliba et al, 2021). Shaded environments reduce the amount of light intercepted by the coffee canopy, thus limiting photosynthetic assimilates, fruit set and final yields (Vaast et al, 2006).…”

“…Artificial shade nets have been widely used in field coffee experiments as a way to mimic an AFS microenvironment (Figure 1a). Studies using such designs have led the coffee community to a common perception that shade equates to lower yields and thus caution remains around recommendations for the use of shade as an on‐farm practice (Koutouleas, Sarzynski, Bertrand, et al, 2022). However, the artificial shade net does not simulate all field dynamics that are inherent to AFS, thus more contemporary studies are making use of natural shaded coffee systems to resemble AFS, such as fast‐growing banana plants as a shade source (Figure 1b).…”

“…However, the artificial shade net does not simulate all field dynamics that are inherent to AFS, thus more contemporary studies are making use of natural shaded coffee systems to resemble AFS, such as fast‐growing banana plants as a shade source (Figure 1b). Recent studies and meta‐analyses are also showing gene × environment (G × E) interactions, which indicate that some coffee cultivars are higher yielding compared to others under shade (Bertrand et al, 2021; Koutouleas, Sarzynski, Bertrand, et al, 2022; Piato et al, 2020). The often full‐sun cultivated Coffea canephora showed significant intraspecies differences in yield when grown under moderate to high shade environments (41%–65%) (Piato et al, 2020).…”