Adapting coffee (Coffea Arabica, L.) production to climate change through types of seedlings and soil fertility management practices in Tanzania
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Date
2024-05
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Publisher
Sokoine University of Agriculture
Abstract
In Tanzania, coffee is the second largest traditional export commodity
after tobacco, accounting for 24 % of the country‘s total foreign
exchange earnings. Average annual production has stagnated at
about 50,000 metric tons over the past 35 years. One of the widely
held reasons is climate change, manifested by high rainfall variability
and decline as well as increase in temperature. Elsewhere different
adaptation strategies like use of shade trees, drought tolerant coffee
varieties and organic fertilizer have been proposed to deal with the
effect of climate change on coffee production. However, climate
change adaptation studies for coffee production in Tanzania are
largely missing. An overall objective of this work was to develop
agronomic techniques for adapting Coffea arabica, L. production to
climate change. Specifically, the study aimed to: 1) asses coffee
growers‘ perceptions on climate change; 2) asses the relationship
between scientific climate change record and production records; 3)
evaluate field performance of compact coffee variety under selected
propagation methods and soil fertility amendment practices and 4)
determine the role of type of seedling and fertilizer management
practices in increasing resilient of coffee species to the changing
climate.
The study was undertaken in the Northern Highland zone (Kilimanjaro
and Arusha regions) and Southern Highland zone (Songwe, Mbeya
and Ruvuma regions), purposively selected based on the level of
Arabica coffee production. First a survey was conducted to examine
smallholder farmers‘ perceptions of climate change. The findings
indicate that, 163 (67 %) farmers perceived climate change has been
taking place in their areas (increase in temperature and decrease in
rainfall); the most influential factors in their perception being level of
education, farming experience and access to climatic information.
Farmers‘ perceptions were also consistent with meteorological data
both pointing to significant decline in rainfall and increase in
temperature. Smallholder farmers have been responding to climate
change through planting shade trees, use of disease-tolerant
varieties, soil fertility management, and irrigation practices. A follow-
up study was conducted to assess the impact of current climate change on Tanzania‘s Arabica coffee production. The findings reveal
minimum temperature has been increasing at a higher rate than the
maximum temperature in both zones. Increase in minimum
temperature by 1°C during short rains and annual mean temperature
resulted in a significant coffee production decrease in Kilimanjaro and
Arusha regions by -6,041 and -4,450 tons respectively. Field
experiments were also established to evaluate performance of
cutting, grafting and seed propagules when combined with 75 g N. P.
K tree-1, 37.5 g N. P. K +10 Kg Farmyard manure (FYM) tree-1 and
37.5 g N. P. K +20 Kg FYM tree-1. Two split plot experiments laid out
in a Randomized Complete Block Design with three replications were
established at the two locations (Lyamungu-Hai district and Burka -
Arusha district) based on the existing climatic gradient; cutting-
propagated plants resulted into highest yield ranging between 1800-
3600 Kg green coffee ha-1 while grafted-propagated plants had the
lowest green coffee yield (600-1700 Kg ha-1.). The fourth study
utilized climatic data from Coordinated Regional Climate Downscaling
Experiment under Representative Concentration Pathway 4.5 to
evaluate the potential of cutting, seed and grafted seedlings in
attenuating the effects of climatic conditions using Dynamic
Agroforestry Coffee model.
During the Near-term period (2026-2056) rainfall will increase in
Kilimanjaro region at the range of 0.2-13 % while in Arusha region the
increase will be 6.05-13 %. Minimum temperature is expected to
increase at higher rate than maximum temperature at the range of
1.4-1.48 °C in Kilimanjaro region and in Arusha region at the range of
1.36-1.64 oC. The use of cutting, seed and grafted propagated coffee
plants when combined with FYM will result into 40% 35 % and 10%
yield reduction respectively. Specific Leaf Area (SLA) among the
three types of seedlings also varied; 28 (cutting), 19 (Seed) and 9
(grafted). Higher SLA observed in cutting-propagated plants may
affect coffee production since it is linked to high loss of water in
plants. Future higher yield loss was observed with the use of
inorganic fertilizer (38%) than FYM (18%) in all the three types of
seedlings. Based on the above results, it can be concluded that during the last
40 years, coffee farmers from the Northern and Southern Highlands
zone of Tanzania have experienced increase in temperature and
decrease in rainfall. Rise in minimum temperature and decline in long
rains has significantly affected coffee production in the Northern
Highlands zone. Similar to the historical period, minimum temperature
is expected to increase at the higher rate than maximum temperature
in the Northern Highlands zone during the Near-term period.
Integrated nutrients sources are able to provide sufficient nutrients to
the three types of seedlings as the recommended rates of inorganic
fertilizer. Yield of cutting propagated plants under the age of four
years if established at the same time with seeds and grafted
propagated plants is significantly higher than that of its counterpart.
However, grafted propagated plants are more resilient to climate
change. It is therefore recommended that, integrated soil fertility
management (37.5 g N.P.K +10 Kg FYM) tree-1 to be used as one of
the adaptation strategies because apart from providing nutrients to
the coffee plants the package also helps in improving water retention
properties of the soil. In addition, seedling distribution should be
location specific, with cuttings-propagated plants being distributed in
areas with rainfall above 1200 mm year-1.
The findings hold significant policy implications for enhancing coffee
production in regions affected by climate change. Policymakers
should enhance timely and accurate weather information delivery
along with developing institutions responsible for education and
extension services provision. Multiplication and adoption of improved
coffee varieties has to be enhanced and promoted by the
policymaker. By promoting adoption of improved coffee varieties
policymakers can enhance farmers' adaptive capacity and reduce the
vulnerability of coffee production to climate-related risks. Future
studies will focus on monitoring the response of three types of
seedlings above the age of four years assuming that at a later age
coffee tree will have reached its maximum production and so more
nutrients and water will be required.
Description
PhD Thesis
Keywords
Adapting Coffee, Coffea Arabica L., Climate Change, Seedlings, Soil Fertility Management Practices, Coffee production, Tanzania