ZEF Bonn

lowered by as much as 5°C. As a consequence, the partial pressure of NH3, which is
an indicator of potential N volatilisation, was significantly depressed. The total N
uptake increased by as much as 42 % and the total dry matter yield by as much as
36 % on Azolla-covered plots. The grain yield was likewise improved. Grain yields
from the 16 on-farm trials increased by as much as 40% at lower N rates (40 and
50 kg N ha-1) and still by 19 % at higher N rates (80 and 100 kg N ha-1).
Thus, using Azolla as a surface cover in combination with urea can be an alternative
management practice to reduce N losses and improve N-use efficiency, and is worth
considering.
3.2.3 Management of soil ecology
Within the bilateral German-Brazilian SHIFT Project on the “Management of plant
organic matter and its effects on litter decomposition and soil macrofauna in central
Amazonian agroecosystems", ZEF is studying the effects of the management of
plant debris in agricultural systems on soil fauna and nutrient cycling. As one of the
most important soil fauna groups, termites play a central role in these systems. The
study consists of field experiments, experiments in microcosms, a screening of different
decomposition systems and experiments on ecotoxicology. The field experiments
comprise three experiments on the manipulation of litter quantity and quality
and an experiment on mulching with wood residues.
3.3 Ecosystems in a Development Context
Uncontrolled exploitation of natural resources has led and will continue to lead to
the irreversible loss of valuable and unique natural resources. There is general international
consensus on using natural resources wisely and in a sustainable manner.
However, poverty and market mechanisms still favour unsustainable resource exploitation.
It is rather difficult to calculate economic values for natural resources, especially
for “service functions" and biodiversity. There is an urgent need to design
appropriate policies and to explore incentive mechanisms that would favour sustainable
use of resources.
ZEF pursues projects that provide a better insight into the principles of ecosystem
functioning. Some of these projects are already mentioned in the previous chapter
on sustainable land use systems (Uzbekistan and Uganda Project), as these two research
themes do overlap to a large extent by their very nature. The bilateral German-
Brazilian SHIFT project “Secondary Forests and Fallow Vegetation in the Agricultural
Landscape of the Eastern Amazon Region, Brazil" as well as the associated SHIFT
project “Smallholders in the Amazon: Interaction between Ecosystem and Social
Systems in the Utilization and Protection of Tropical Rainforests" deal with human
impact on ecosystems and are focusing on concepts for using natural resources in a
sustainable manner. Details are given in a previous section of this report.
Research
Uncontrolled exploitation of
natural resources has led to
the irreversible loss of valuable
and unique natural resources.
There is an urgent need to
design appropriate policies and
to explore incentive mechanisms
that would favour
sustainable use of resources.
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