Dr. Y. Raghuramulu

Coffee in India is grown primarily in the Western Ghats spread over three southern states of Karnataka, Kerala and Tamil Nadu and to some extent in the Eastern Ghats of Andhra Pradesh and Orissa and also in the North East region. Owing to peculiar agro-climatic conditions prevailing in India, such as wide range of fluctuations in day temperatures and monsoon driven rainfall pattern with a drought period of 3-5 months, there is a compulsion to grow coffee under shade so as to maintain ideal microclimate for coffee bushes. While cultivation under shade offers distinct advantages it also inhibits overall productivity, when compared to coffee grown under open conditions as in some countries like Brazil, Vietnam etc. Shaded plantations are also not amenable for mechanization of field operations. Thus to a large extent, coffee cultivation in India remained a traditional agriculture activity.

When the prices of coffee ruled high in the international market during mid 1990s, many growers have attempted to intensify coffee cultivation to increase production & productivity of their plantations. One of the first steps in this direction was intensification of cultivation through reduction in shade. In case of Arabica estates, the lower canopy temporary shade trees like dadap were totally eliminated and the permanent shade was thinned out. In case of irrigated robusta the reduction in shade was more drastic with many plantations almost completely opening their shade. Growers observed an increase in response of coffee bushes to manuring and irrigation after reducing shade which led to more growers following the suit.

Subsequently, when the prices started declining the growers tended to neglect many operations especially manuring and plant protection and also extracted timber from their plantations to sustain their incomes. Neglect of certain vital operations, removal of shade and long drought for three consecutive years (2002-04) resulted in severe outbreak of dreaded pest white stem borer and leaf rust disease in Arabica coffee. In case of robusta, the impact was limited only to reduction in yield due to lack of adequate water resources for blossom/ backing irrigation. Today, the flare up of white stem borer in Arabica is threatening the survival of Arabica coffee plantations in India. Unless something drastic is done it would be difficult to sustain the production of Indian coffee in the long run especially due to increased recurrence of price crashes and drought conditions.

It is in this context that we need to reassert the significance of shade for coffee in India, so that the goal of long term sustainability of coffee plantations is achieved by compromising short-term benefits.

What are the benefits of shade?

a) Contribution to micro-climate: Shade confers many beneficial effects to coffee plantations in particular and ecology of coffee tracts in general. Primarily, the shade reduces the diurnal range of ambient air temperatures (difference between day and night temperatures) thus providing ideal micro-climate for growth and production of coffee bushes. Shade also protects coffee bushes from damage by hailstorms and winds by acting as a physical barrier. These benefits are achievable only under mixed shade canopy conditions.

b) Contribution to soil fertility: It is estimated through scientific studies that under mixed shaded conditions, the shade trees contribute nearly 10 MT of biomass (leaf litter, small twigs etc) per annum per ha, which is vital for maintaining the organic matter content of soil. Soils rich in organic matter support activity of many beneficial microorganisms like nitrogen fixers, phosphorus solubilizers etc. Nitrogen fixing bacteria help in fixation of atmospheric nitrogen into the soil thereby enriching soil nitrogen while the `P' solubilizing microbes like phosphobacter and Vesicular and Arbuscular Mycorrhiza (VAM) help in release of fixed phosphates for plant growth. Soils rich in organic matter have also have better retention of nutrients through binding effect, which otherwise would have lost by leaching during heavy rains. Besides, the manurial value of the biomass contributed by shade trees is reported to be around 100kg nitrogen, 35kg phosphorus and about 45kg potassium per ha per year (Krishnamurthy Rao, 1989). Shade trees with their deep root system absorb nutrients from deeper layers of soils which otherwise are unavailable to coffee plants due to their relatively shallow root system and recycle them to top layers in the form of biomass, thus recycling the nutrients from deeper layers. In the absence of natural shade system, it would be very difficult as well as uneconomical to provide the same amounts of organic matter through organic manures/ composts so as to match with the contributions of well defined mixed shade canopy.

c) Soil and moisture conservation: Soils in coffee areas of India are not very deep, rarely exceeding 75 cm, when compared to the deep volcanic soils in many producing countries. Thus, protecting the top fertile soil from the erosion losses is very important for sustained growth of coffee bushes. But most of the coffee in India is cultivated on sloping terrain where soil erosion is a serious problem due to heavy rainfall during monsoon season. Certain soil conservation measures like terracing and contour planting are advocated in medium to steep slopes to minimize soil erosion. But even when such conservation measures are adopted, there will be some amount of soil erosion during heavy downpours. This can be arrested by providing good shade canopy. Shade trees act in two ways to minimize soil erosion. Firstly, they act as physical barrier and reduce the intensity of rain. Secondly, with their deep root system, help in percolation of rain water into deeper layers of soil thus minimizing run off of rain water and at the same time contributing to recharging of ground water.

Shaded plantations are also well protected against drought effects. The cool temperature above the coffee bushes due to shade, ensure that the loss of soil moisture through evaporation and transpiration is minimised. Besides, the shaded plantations being rich in soil organic matter retain moisture for longer periods during dry months when compared to open conditions.

d) Shade as a tool for pest/ disease management: Shade offers a very effective management tool for the control of major pests and diseases Iike coffee white stem borer and leaf rust in Arabica coffee. It is well documented that White stem borer is active in open patches within the estate and these open patches provide ideal conditions for spread of the pest to neighbouring bushes. The activity of borer beetles is suppressed at cooler temperatures. Thus providing uniform shade becomes one of the major components in the effective management of the white stem borer. Besides providing unfavorable conditions for white stem borer, the shade trees are also reported to harbour a variety of predatory birds and natural enemies of white stem borer thus contributing towards natural control of the pest.

As mentioned elsewhere in this article, shade suppresses the productivity of coffee bushes to certain extent. This in fact helps in prevention of over bearing and exhaustion of coffee bushes, which is a predisposing factor for coffee leaf rust attack in arabica. Thus, an optimum shaded condition ensures the vigour of coffee bushes thereby reducing leaf rust incidence.

e) Reducing the biennial bearing in coffee: Shade is reported help not only in the long term maintenance of coffee yields but also to even out erratic yields caused by periodic over bearing and subsequent die back (Huxley, 1970). This is due to the fact that shade reduces the amount of light reaching the coffee bushes which reduces the potential yields (Willey, 1975).

f) Shade trees as source of income An estate with mixed shade canopy would have about 80-100 permanent shade trees and about 275-300 temporary/ intermediate shade trees. Under judicious management system, shade trees provide substantial revenue to the coffee growers in the form of timber, firewood and edible fruits etc. However, excess opening of shade beyond the recommended level or felling of trees for timber purpose for short term benefits can become counter productive in the long run, as discussed already in this article.

Scientific evidences suggest that shade grown coffees have better quality than coffees grown under open conditions at least in tropical countries like India. Recently, shade grown coffee is being encouraged as speciality coffees in the world market due to its contribution towards preservation of ecosystem in coffee areas and also conservation of certain endangered bird species. There are well laid out certification systems for shade grown coffee by institutions like Smithsonian Migratory Bird Centre and Rainforest Alliance. The coffees certified under these standards will fetch attractive premiums in the international market.

What type of shade is desirable for coffee in India?

A two-tier mixed shade canopy providing uniform, filter shade is considered as ideal for coffee in India. Arabica prefers high degree of shade (about 60%) while robusta performs well at 30-40% shade provided irrigation facility is available. In case of rainfed (unirrigated) robusta, about 50% shade would be highly desirable so as to protect the crop yields from delayed blossom & backing showers. The intensity of shade in a plantation shall vary depending on the elevation and aspect. At lower elevations and in southern/ western exposed areas, a thick shade should be provided than the recommended level while at higher elevations the intensity of shade can be reduced marginally.

An ideal shade tree should belong to leguminous family (as they can fix atmospheric nitrogen into soil) and have a tall spreading growth habit, small leaves and should be resistant to wind damage. Considering the above parameters, the trees identified as suitable for coffee plantations are Plerocarpus marsupium (Honne); Albizzia lebbeck (Kalbage); Ficus sp., (atti, bilibasari, mittlee, goni, neeru basari, kari basari); Cedrella toona (Red cedar/gandhagarige); Artocarpus integrifolia (Jack) Artocarpus hirsute (hebbalasu); Bischofia javanica (nerale) and Terminalia bellarica. It is desirable to have a mixture of all these trees in a given plantation for providing top canopy shade. Dadap (Erythirna lithosperma) has been the most popular lower canopy shade tree in coffee plantations due to its fast growing nature and amenability for frequent loppings (trimming) (Anon.2003). Silver Oak (Grevileia robusta) has been recommended only as an intermediate shade because of its certain desirable features like fast growth with tall main trunk which is ideal for providing support to the pepper vines and amenability for extraction of timber (at right age) without causing much damage to coffee bushes. In non-traditional areas like Andhra Pradesh and Orissa coffee plantations are mainly shaded with Silver oaks. In these areas, Silver oak is usually planted 3-4 years in advance, to quickly establish shade in barren `podu' lands, before taking up coffee planting. But even in traditional areas, especially in Yercaud and Pulneys regions in Tamil Nadu, Silver oak has become popular among the growers over a period of time, which resulted in almost mono-shaded condition in many plantations. Mono-shade of silver oak is now being realized as a major constraint for arabica coffee production, especially when combined with erratic monsoons and neglected management as evidenced in recent years.

Why silver oak mono shade is not good for coffee?

It is well known that Silver oak mono-shade will not provide required cool, equitable microclimate for Arabica coffee. Silver oak trees also do not contribute much towards the fertility of coffee soils unlike other permanent shade trees. This is due to the fact that the leaf litter from Silver oaks will not decompose easily under estate conditions and will remain as mulch on soil. The leaves (of silver oak) persist on coffee bushes affecting ventilation to the bushes there by encouraging black rot disease in certain endemic areas during monsoon season. In terms of nutrient contribution, it is reported that silver oak leaves are rich in aluminium content. Thus if Silver oak leaves are incorporated as compost in coffee soils, there will be accumulation of aluminium content in soil which not only leads to fixation of phosphorus in the form of aluminium phosphate and also may lead to toxicity to coffee bushes.

Thus, seen from any angle monoshade of silver oak is not ideal for coffee under Indian conditions and it is most essential to have a mixed shade pattern in which the population of silver oak should not exceed 100 per ha. at any given point of time. In already existing Silver oak mono-shaded coffee plantations, there is an urgent need to plant assorted shade trees to develop mixed shade pattern, for the long term sustainability of coffee plantations in India.

Conclusion:

Shade grown coffee plantations could be considered as one of the most effective carbon sinks available in the country. The cumulative benefits of natural shaded canopy in coffee tracts of India are much beyond calculation by human effort. Without shade, coffee plantations in India would become unviable and this can have an adverse impact on the environment in the Western Ghats where close to 90% of coffee is produced towards country's total production. Also, there are very few profitable alternate crops that could replace coffee in the Western Ghats. Thus, shade is indispensable not only for sustenance of coffee plantations in India but also for preserving the environment in the ecologically sensitive Western and Eastern Ghat regions.

Selected References

Anonymous. 2003. Coffee Guide. Published by Central Coffee Research Institute, Coffee Board, India, 2003. 200p.

Huxley, P.A.1970. Some aspects of physiology of Arabica coffee. In `Physiology of Tree crops'. (Ed. by Luckwill, L.C. and Cutting, C.U.), Academic Press. London and New York. pp.25-67.

Krishnamurthy Rao, W. 1989. Nutrition management in plantation crops. iPlantation crops. 16 (Suppl), 403-411.

Willey, R.W. 1975. The use of shade in coffee, cocoa and tea. !lort. Abstracts. 45: 791-797.