The Water Relations and Irrigation Requirements of Coffee

Abstract

The role of water in the development and yield of the coee crop (Coea arabica L.) is reviewed. A period of water stress, induced either by dry soil or dry air, is needed to prepare¯ower buds for blossoming that is then stimulated by rain or irrigation. Although attempts have been made to quantify the intensity and duration of stress required, these have not yet been speci®ed in ways that are commercially useful. Water must be freely available during the period of rapid fruit expansion to ensure large, high-quality seed yields. Depending on the time and uniformity of¯owering this can occur at times when rainfall is unreliable, particularly in equatorial areas.Although there are dierences in their responses to drought, commercial cultivars have retained many of the characteristics adapted to the shady environment of the forests in the Ethiopian highlands in which C. arabica is believed to have originated. These include partial closure of the stomata when evaporation rates are high as a result of large leaf-to-air saturation de®cits (41.6 kPa), even if the soil is at ®eld capacity. This is thought to be an adaptive mechanism that minimizes transpiration at high irradiances when the leaves are light-saturated.Our understanding of the actual water use of coee crops grown in diverse ways is imperfect. For mature crops, well supplied with water, the crop coecient (Kc) appears to have a value in the range equivalent to 0.7±0.8 times the evaporation from a US Weather Bureau Class A pan. There is some evidence that Kc values are less than this on days when evaporation rates are high (47 mm d 71 ). For immature crops allowance has to be made for the proportion of the ground area shaded by the leaf canopy, but this alone may underestimate rates of water use. Present methods of calculating crop water requirements for the purposes of irrigation scheme design and management are imprecise and, probably, subject to large errors depending on local circumstances.The need for irrigation, and its role in controlling the timing of¯owering, varies depending on the rainfall distribution, the severity of the dry season, and soil type and depth. Two geographic areas need to be distinguished in particular; those close to the equator with a bi-modal rainfall pattern and those at higher latitudes with a single rainy season and an extended dry season. Despite the international importance of irrigation in coee crop production, the bene®ts to be derived from irrigation, in yield and in ®nancial terms, have not been adequately quanti®ed in either location. Allowable soil-water de®cits have been speci®ed for deep-rooting crops (2±3 m) on water retentive soils, usually linked to conventional over-tree sprinkler irrigation systems. Other, potentially more ecient, methods of irrigation are now available for coee grower use, in particular, micro-jet-and drip-irrigation systems. However, there appears to be little advice, based on sound experimental work, on how to design and operate these to best advantage.There is a need to interpret and apply the s...

Coffee crop coefficient for precision irrigation based on leaf area index

“…An approach used in Zimbabwe allows Kc to vary with age/size/planting arrangement of trees as it is defined as the ratio of the canopy area to the planted area (Carr, 2001). Camargo and Pereira (1994) recommend that Kc be estimated as 1.2 times the fraction of ground shaded by coffee trees around noontime to allow for values above 1.0, the limit for completely shaded ground area, and for seasonal leaf area changes.…”

Ecophysiology of coffee growth and production

“…Earlier arabica coffee plantations were established at fewer than 2000 trees ha -1 (Carr, 2001), or even below 1000 trees ha -1 as for the multi-stemmed conilon coffee in Brazil. However, several reports have indicated that coffee may be more suited for high-density plantings; indeed the productivity of dense plantings is generally much greater than that of traditional plantings (DaMatta, 2004a, and references therein).…”

“…Several aspects of coffee (eco)physiology have recently been reviewed, including water relations and drought tolerance (Carr, 2001;Rena, 2001, 2002a;DaMatta, 2004c;DaMatta and Ramalho, 2006), photosynthetic acclimation to light availability (DaMatta, 2004a), nitrogen metabolism (Carelli et al, 2006), seed physiology (Eira et al, 2006), caffeine (Baumann, 2006), and impacts of extreme temperatures and drought on coffee physiology and production (DaMatta and Ramalho, 2006). Therefore, these aspects will not be examined here in detail.…”

Evapotranspiração e coeficientes de cultivo de cafeeiros em fase de formação

“…Em geral, esses trabalhos se baseiam em estimativas indiretas, o que limita a aplicação dos resultados em situações diferentes das que foram desenvolvidos (CARR, 2001). Assim, CLOWES (1984) considerou Kc médio igual a 0,6 para todas as fases fenológicas do cafeeiro irrigado por gotejamento.…”