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Intercropping annual fields with perennial plants [Elektronische Ressource] : a strategy to reduce land degradation in semi-arid regions / von Ayman Moh'd Atieh Salah

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Intercropping annual fields with perennial plants - A strategy to reduce land degradation in semi-arid regions von der Fakultät für Architektur und Landschaft Der Gottfried Wilhelm Leibniz Universität Hannover zur Erlangung des Grades Doktor der Ingenieurwissenschaften Dr.- Ing. Genehmigte Dissertation von M.Sc. Ayman Moh’d Atieh Salah Geboren am 3 März 1966 in Kuwait 2008 Referent: Prof. Dr. Rüdiger Prasse, Institut für Umweltplanung. Koreferent: Prof. Dr. Bernd Marschner, Ruhr-Universität Bochum. Tag der mündlichen Prüfung: 5. Mai 2008. ii Acknowledgements !"#$ # !

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Published 01 January 2008
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Intercropping annual fields with perennial
plants - A strategy to reduce land degradation
in semi-arid regions



von der Fakultät für Architektur und Landschaft
Der Gottfried Wilhelm Leibniz Universität Hannover
zur Erlangung des Grades
Doktor der Ingenieurwissenschaften
Dr.- Ing.


Genehmigte Dissertation

von
M.Sc. Ayman Moh’d Atieh Salah
Geboren am 3 März 1966 in Kuwait

2008















Referent: Prof. Dr. Rüdiger Prasse, Institut für Umweltplanung.
Koreferent: Prof. Dr. Bernd Marschner, Ruhr-Universität Bochum.

Tag der mündlichen Prüfung: 5. Mai 2008.

ii Acknowledgements

































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iii Declaration

I hereby declare that this submission is my own work. I designed all the
experiments, applied the field and laboratory work, collected the field data,
performed the statistical analysis of the data and wrote the manuscripts by myself.
Throughout the research, I was advised by Prof. Dr. Ruediger Prasse, who
discussed the results and contributed to advanced drafts and final stages of the
manuscript.
I certify that this thesis has not been submitted as dissertation to any other
university or institute nor any of its parts.



5, 5, 2008

iv Intercropping annual fields with perennial plants - A
strategy to reduce land degradation in semi-arid regions

Abstract

Soil erosion and declining of soil quality seriously threaten agricultural
sustainability worldwide. These processes are especially relevant in semiarid and
arid regions which are usually inhabited by poor populations depending mainly on
rain fed agriculture for their livelihood. It is well-known that a permanent vegetation
cover may reduce the surface runoff and soil erosion and may improve soil quality.
However, the application of permanent cover on annual crop production fields is
not usually an option due to the loss of some productive area.
In this study an agricultural technique was developed on arable annual
production fields, which permits to combine the advantages of a perennial ground
cover with the production needs. The developed system is a multi-species
intercropping in which strips of useful native perennial plants were used as
intercrops. These strips may reduce the surface runoff and erosion as well as the
loss of soil fertility. The native plants intercrops used are usually collected by the
local population as food, spice or medicine. Therefore, this system allows farmers
to apply a meaningful economically conserving technique.
A field experiment from 2004 to 2006 was conducted to test whether it is
possible to control soil and water losses and to conserve soil quality with the help
of the described method without financial losses for the farmers. The experiment
was conducted in semiarid and arid areas in Al-Khalil district, West-bank. Two sites
situated along an aridity gradient of different mean annual precipitation (approx.
425 mm and approx. 595 mm) were selected in order to acquire additional
information on the influence of climate on the effects of the management strategy.
The results show that both the unproductive water loss by runoff and soil
loss by erosion were strongly reduced by intercropping with native perennial plants.
Intercropping reduced runoff by 34% - 89% and reduced soil erosion by 45 % -
v 94%. The positive effects of intercropping were consistent in two consecutive
seasons of investigation and in both investigated areas. The effectivity of
intercropping in controlling runoff and soil loss was more pronounced at the drier
part of the studied rainfall gradient and during the drier season.
The soil parameters tested -soil organic matter content (SOM) and microbial
activity- were also improved by intercropping compared to the mono-species
control. The results show low level of microbial activity and a rapid decline of SOM
in the not intercropped arable fields during the two years of study. By contrast, the
SOM content was maintained, and the level of microbial activity was enhanced in
the intercropped fields. Species specific effects of intercrops were not observed in
conserving water and soil resources.
The developed intercropping system using native perennial plants had
minimal negative effect on the yield of the annual crops. The reduction of crop yield
was less than may be expected as 10% of the field area was used for the native
plants intercrops. The slightly lower annual crop yield in the intercropped fields was
compensated for the farmers by the income gained from marketing the native
plants. The income gained from the intercropping system with native perennial
plants was stable and consistent in the two investigated seasons, while the income
gained from the annual crops was proportional with the amount of rainfall received
in each season with lower yields in the dry season. This means that, in semiarid
regions the income from intercropping system may be more sustainable and
reliable compared with the monoculture system. These observations were
consistent in the two investigated sites.
This study implies that intercropping with useful native perennial plants is a
sustainable economic agriculture management that may help in protection of the
existing soil resources. The study shows that intercropping is a suitable technique
for semi-arid regions, and may be suitable as a mitigation strategy to cope with the
effects of the expected global climatic changes.

Keywords: intercropping, erosion, runoff, organic matter, native perennial plants.
vi Zusammenfassung
Zwischenfruchtanbau mit ausdauernden Pflanzenarten -
Eine Strategie zur Reduzierung von Erosion,
Oberflächenabfluss und Bodenfruchtbarkeit auf Äckern in
semi-ariden Gebieten
Bodenerosion und der Verlust von Bodenfruchtbarkeit sind weltweit auftretende
Phänomene, welche oft die Nachhaltigkeit der landwirtschaftlichen Nutzung gefährden.
Die Gefährdung der langfristigen Nutzbarkeit der Böden ist insbesondere in Regionen
auffällig, deren Umweltbedingungen schon heutzutage kaum noch Landwirtschaft
zulassen und in denen daher eine oft arme Bevölkerung lebt. Es handelt sich z. B. um die
von Viehzucht und Regenfeldbau dominierten semi-ariden Regionen im Übergang zu den
Wüsten dieser Erde.
Es ist bekannt, dass der Aufbau bzw. der Erhalt einer dauerhaften Vegetationsdecke den
Oberflächenabfluss und die Erosion sowie alle damit verbundenen Auswirkungen (Verlust
der Bodenfruchtbarkeit etc.) reduzieren kann. Der Aufbau bzw. der Erhalt einer solchen
mehrjährigen (perennen) Vegetation auf Äckern ist allerdings üblicherweise eine für den
Landwirt nicht umsetzbare Landnutzungsstrategie. Dies insbesondere, da eine
mehrjährige Pflanzendecke die auf dem Acker zur Verfügung stehende Produktionsfläche
reduzieren würde und der Landwirt mit Produktionseinbußen rechnen müsste.
In der vorliegenden Arbeit wird eine landwirtschaftliche Produktionsmethode entwickelt,
welche es erlaubt, die Vorteile einer mehrjährigen Pflanzendecke mit dem
landwirtschaftlichen Produktionsbedürfnis zu verbinden. Zu diesem Zweck wurden in mit
einjährigen Pflanzen bestellten Äckern, Streifen mehrjähriger Pflanzenarten eingezogen.
Diese Streifen sollten den Oberflächenabfluss sowie die damit verbundene Erosion und
den Verlust an Bodenfruchtbarkeit reduzieren. Dieses „Intercropping“ wurde mit
Pflanzenarten vorgenommen, welche von der lokalen Bevölkerung üblicherweise als
Nahrungsmittel, Gewürz oder Medizin gesammelt werden. Dies ermöglicht dem Landwirt,
vii