Fachhochschule Wiesbaden Standort Geisenheim
Fachbereich Geisenheim Studiengang Gartenbau-Management
Bachelorarbeit
Musa in Shaded Perennial Crops - Response to Light Interception
Referent: Prof. Dr. Joachim Heller Korreferent: Prof. Dr. Jürgen Jaki
Vorgelegt von:
Christian Dold Geisenheim, den 24.01.2007 Eidesstattliche Erklärung:
Ich erkläre hiermit wahrheitsgemäß, daß ich
- die eingereichte Arbeit selbständig und ohne unerlaubte Hilfsmittel angefertigt habe,
- nur die im Literaturverzeichnis aufgeführten Hilfsmittel benutzt und fremdes Gedankengut als solches kenntlich gemacht habe,
- alle Personen und Institutionen, die mich bei der Vorbereitung und Anfertigung der Abhandlung unterstützt haben, genannt habe und
- die Arbeit noch keiner anderen Stelle zur Prüfung vorgelegt habe
Ort, Datum
Unterschrift (Vor- und Zuname) Acknowledgement
I would like to thank Dr. Charles Staver, Bioversity International, and Dr. Luis Pocasangre, Centro Agronómico de Investigación y Enseñanza (CATIE) and Bioversity International, for their supervision, for the opportunity of an internship at CATIE, and for their support.
Furthermore, I would like to thank the BEAF-Group of Deutsche Gesellschaft für Technische Zusammenarbeit, namely Dr. Marlene Diekmann and Dr. Kasten, for the financial and administrative support; without it would have not have been possible to do my internship.
Also, I would like to thank Inwent gGmbH, namely Iris Lenzen, for their financial and administrative support.
Besides, it is a great pleasure to thank Prof. Dr. Joachim Heller for his supervision, not only during my internship and my bachelor thesis, but also during my studies at the University of Geisenheim. Furthermore, Prof. Dr. Jürgen Jaki, for his supervision and support during my bachelor thesis, as well as Prof. Dr. Kai Velten; without him there would be not much of statistical data.
At last, I would like to thank Pablo Siles – Are you already a PhD?
Contents
1 Introduction ...... 1
1.1 Formulation of the Problem ...... 1
1.2 Aim of the Work...... 1
1.3 Structure of the Work...... 1
2 Light Interception in Tropical Agroforestry Systems...... 2
3 Musa in Agroforestry Systems ...... 11
3.1 Importance of Musa on Farm Level in Central America...... 11
3.2 Research Review on Musa in Shade...... 13
4 Musa in Shaded Coffee - A Case Study of Costa Rica ...... 21
4.1 Description ...... 21
4.1.1 Botanic garden – Musa ‘Gros Michel’ in Sun and Shade.. 21
4.1.2 Six Varieties in Four Different Light Levels ...... 23
4.1.3 Light measurements in Agroforestry Systems ...... 24
4.1.4 Interviews ...... 24
4.2 Material and Methods...... 25
4.2.1 Light Measurements ...... 26
4.2.2 Number of Functional Leaves...... 28
4.2.3 Length of the Petiole...... 28
4.2.4 Non-destructive Measurements of Leaf Area ...... 29
4.2.5 Destructive Measurements of Leaf Area...... 29
4.2.6 Leaf Emission Rate (LER) ...... 32
4.2.7 Circumference and Height ...... 32
4.2.8 Black Sigatoka Leaf Spot...... 33
Seite I
4.2.9 Leaf Tearing ...... 33
4.2.10 Leaf Angle ...... 34
4.2.11 Leaf Folding...... 35
4.3 Results ...... 36
4.3.1 Light Measurement in the Botanic Garden ...... 36
4.3.2 Results Pseudostems III ...... 38
4.3.3 Results Pseudostem II...... 44
4.3.4 Results Six Varieties...... 48
4.3.5 Light Measurements in Coffee Agroforestry Systems...... 52
4.3.6 Interviews ...... 60
5 Discussion...... 60
6 Conclusion ...... 67
7 References...... 69
Seite II
List of Figures
Fig. 1: Solar radiation at different latitudes with respect to seasonal variation
Fig. 2: Instanenous Photon Flux Density (PFD) at two points of the same gap, Costa Rica
Fig. 3: The exponential attenuation of solar radiation in a plant stand
Fig. 4: Using Beer’s law requires a random structure of the canopy
Fig. 5: Amount of solar energy in four Central American banana production areas
Fig. 6: Comparison of the results of MURRAY (1961), and ISRAELI et al. (1995)
Fig. 7: Summary of different research about cultivar light response curves
Fig. 8: Banana ‘Gros Michel’ mainly asociatied with cacao at CATIE
Fig. 9: The shaded banana suckers in the shade of coffee, Poró and Cedro
Fig. 10: Example for counting the total number of leaves
Fig. 12: Measurement of the angle between leaf sheath and leaf angle
Fig. 13: Measuring the leaf blade angle using a template
Fig. 14: Radiation environment in week 18 in the two treatments above the Pseudostem III
Fig. 15: Radiation environment in week 18 in the two treatments above the Pseudostem II
Fig. 16: Weekly number of leaves of Pseudostems III
Fig. 17: Weekly measurements of Leaf Emission Rate (LER) of Pseudostems III
Fig. 18: Two-week measurements of height (cm) of Pseudostems III averaged data
Fig. 19: Measurements of circumference (cm) of Pseudosems III
Fig. 20: Weekly leaf area of pseudostems II from week 13 to week 27
Fig. 21: Weekly measurements of Leaf Emission Rate (LER) of Pseudostems II
Fig. 22: Measurements of height (cm) from week 13 to week 34 of Pseudostems II
Fig. 23: Total transmitted light (%) in the most shaded plot; above coffee and above banana
Seite III
Fig. 24: Raditation regime of the four plots above and in height of the banana plants
Fig. 25: Average growth of height of six banana varieties in different light regimes
Fig. 26: Average growth of leaf area of six banana varieties in different light regimes
Fig. 27: Average total transmitted light of the all coffee agroforestry systems
Fig. 28: Light dispersal map of Coffee – Cashá agroforestrial system
Fig. 29: Light dispersal map of Coffee – Roble Coral agroforestry system
Fig. 30: Light dispersal map of Coffee – Poró agroforestry system
Fig. 31: Light dispersal map of Coffee – Roble Coral - Cashá agroforestry system
Fig. 32: Light dispersal map of Coffee – Poró - Cashá agroforestry system
Fig. 33: Light dispersal map of Coffee – Poró – Roble Coral agroforestry system
Fig. 34: Musa AAA Cavendish subgroup; light response curve
Fig. 35: Stations of leaf development
Fig. 36: Gauhl’s modification of Stover’s severity scoring system
Seite IV
List of Tables
Tab. 1: Summary of different research about impacts on photosynthesis rate
Tab. 2: Method of growth measurement and frequency
Tab. 3: Impact of Black Sigatoka on Pseudostems III in two different light conditions
Tab. 4: Leaf Tearing of twenty plants comparable in height of Pseudostems III in week 18
Tab. 5: Estimated average leaf area of Pseudostems III from week 18 to week 35
Tab. 6: Impact of Black Sigatoka on Pseudostems II in two different light
Tab. 7: Leaf area of week 26 and estimated total increase of leaf area
Tab. 8: Folding of the leaf blades; measurements at the 2nd leaf of Pseudostems
Tab. 9: Leaf Angle of Pseudostem II; week 20; Leaf 1 to 5
Tab.10: Growth of Height, Circumference, Length of Petiole and Leaf Area of six varieties
Tab. 11: Explanation of the five stages of leaf development
Tab. 12: Soil samples of the botanic garden, ten of each; 0 – 30 cm
Tab. 13: Soil samples of the site with the six varieties; 0 – 10 cm
Tab. 14: Soil samples of the site with the six varieties; 0 – 30 cm
Tab. 15: Amount of dry matter of organic fertilizer in the plots with the six varieties
Seite V
List of Abbreviations
AN Leaf area of the youngest leaf (equation 10)
Ai Leaf area of the oldest green leaf (in equation 10)
Ai, N integration of the leaf areas between leaf i and leaf N (in equation 10)
AR Rate of increasing leaf area
CATIE Tropical Agriculture Research and Higher Education Centre dm Percentage of dry matter in the fruit tissue
DDT Disease development time
GLA Gap Light Analyzer (software)
GPS Global Positioning System
H Radiation on any point on earth at the ground per time unit
H0 Extraterrestical radiation per time unit
Hb Direct solar radiation
Hi Harvest index i oldest leaf in equation 10
I Incident radiation below the canopy (in PFD)
Io Radiation above the canopy (in PFD)
Ia PFD absorbed by the canopy
Ir PFD reflected by the canopy
Irs PFD reflected by the soil
It PFD transmitted through the canopy k Extinction coefficient
Kt Cloudiness Index
Seite VI
L Leaf Area Index
LER Leaf Emission Rate
N youngest leaf in equation 10 (its number represents total number of leaves)
P first crop cycle of banana
PAR Photosynthetic Active Radiation
PFD Photosynthetically active photon flux density (µmol photons m-2s-1)
Rp visible waveband between 400nm and 700 nm
Rs total shortwave (broadband) radiation (all wavelengths 0.25 m to 25 m)
R1 first ratoon cycle of banana
Tc Temperature coefficient
Y Yield of banana
YLS Youngest leaf spotted
γ Radiation use efficiency
Seite VII Christian Dold Introduction
1 Introduction
1.1 Formulation of the Problem
Throughout the tropics banana and plantain (Musa spp.) is a very common crop in agroforestry systems, characteristically cultivated by small scale farmers. The production is extensive with low financial imputs and labour. Typically, it is associated with perennial crops like coffee (Coffea sp.) and cacao (Theobroma sp.) and an upper story of timber trees. Thus, Musa spp. is cultivated in highly shaded conditions. Light interception is one significant limiting factor (NORGROVE 1998, STOVER and SIMMONDS 1987 204-205, 228-231)
While research is mainly focused on all other production units, the improvement of shaded banana and plantain yield is widly neglected. The few research which are available are discriminated; banana yield was increased as well as decreased due to shade. Therefore, the question stays remain if banana production in agroforestry systems could be improved in relation to light interception (TURNER 1998).
1.2 Aim of the Work
Aim of this work is to ask and find possible answers on the widely unknown topic how the production of shaded Musa spp. in agroforestry systems can be improved.
1.3 Structure of the Work
At first, some facts about light interception are necessary to understand light as a main limiting factor in agroforestry systems. Then, a brief description of the importance of banana and plantain in agroforestry systems will be shown. Then, the state of art concerning the research on banana in shade will help to understand the theoretical backround. Besides, a recent study on banana in shade in the tropical region of Costa Rica can give some results on the topic. A general discussion will concern with the advantages and disadvantages of banana production in agroforestry systems, and can give an outlook on further research. In the end, the conclusion will summarize the main ideas of this work.
Seite 1 Christian Dold Light Interception in Tropical Agroforestry Systems
2 Light Interception in Tropical Agroforestry Systems
The tropics are defined as the belt around the earth between the Tropic of Cancer (23° 30’ latitude N) and the Tropic of Capricorn (23° 30’ latitude S). As the axis of the earth being inclined by around 23° 30’, at some time of the year sun rays are perpendincular in the tropics. Also variation of day length is very little. At the equator day length is always about 12 hours. The difference between the longest and the shortest day is increasing by about 7 minutes per degree in the tropics (NAKASONE and PAULL 1998 3 – 6).
The energy that reaches earth on a perpendicular surface at the mean distance from the sun is called solar constant. The solar constant is 1.37 kJ m-² s-1.
The amount of solar radiation which reaches earth is depending on latitude and season (see Fig. 1). In the tropical belt there is a smaller variation of annual solar radiation compared to higher latitudes. The ratio between the solar energy flux on any latitude on earth to the solar constant is called geometrical ratio.
Fig. 1: Solar radiation at different latitudes with respect to seasonal variation
Reference: AZAM-ALI and SQUIRE (2001)
Seite 2 Christian Dold Light Interception in Tropical Agroforestry Systems
In addition, the amount of solar radiation reaching earth is depending on gases, clouds and aerosols in the atmosphere which are capable of absorbing and scattering radiation
(NAKASONE and PAULL 1998 3 – 6, AZAM-ALI and SQUIRE 2001 29). Overcast conditions ocurre especially in the humid tropics where in average only three to five sunshine hours per day are available (ROBINSON 1996 89).
The cloudiness index gives the severity of scattering and absorbing components in the atmosphere and can be computed (FRAZER et al. 1999):
Kt = H/H0 (1)
Where Kt is the cloudiness index, H is the incident global radiation on any point on earth at the ground per time unit, and H0 is the extraterrestical radiation per time unit
The radiation going through the atmosphere can be divided in a direct beam fraction and a diffuse fraction. “Direct (beam) radiation is the energy that streams from the solar disk and is neither absorbed nor scattered by the earth’s atmosphere. Diffuse radiation is the portion that is scattered towards the earth’s surface from all regions of the sky.” (FRAZER et al. 1999).
The more clouds, gases and aerosols in the atmosphere, the higher is the amount of diffuse raditation. Hence, beam fraction is depending on the cloudiness index:
Hb/H = [1-exp(-3.044Kt2.436)] (2)
Where Hb is the direct radiation, H is the incident global radiation per time unit, Hb/H is the proportion of direct solar radiation and Kt is the cloudiness Index (FRAZER et al. 1999).
After considering latitude as well as direct beam and diffuse radtiation, the amount of Photosynthetic Active Radiation (PAR; 0.4 to 0.7 µm waveband) reaching earth is of importance. It is the radiation which is necessary for photosynthesis and thus, is responsible
Seite 3 Christian Dold Light Interception in Tropical Agroforestry Systems for plant growth. The proportion of PAR to the total incoming shortwave radiation is called the spectral fraction. In general, in the tropics about 50% of incoming radiation is considered to be PAR. But with increasing cloud cover (Kt < 0.5) the amount of PAR increases. Thus, the flux of PAR is also depending on the cloudiness index (R2=0.73) and can be computed
(FRAZER et al. 1999, AZAM-ALI and SQUIRE 2001 29-30).
-0.219 Rp/Rs=1-exp(-0.499Kt ) (3)
Where Rs is the total shortwave (broadband) radiation contributed by all wavelengths (0.25