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C.J.Pilbeamet al.
Nitrogen Fluxes Through Sustainable Farming Systems
4.7
Nitrogen Fluxes Through
Sustainable Farming Systems
in the Mid-hills of Nepal
C.J. P
ILBEAM
1
, P.J. G
REGORY
1
, B.P. T
RIPATHI
2
AND
R.C. M
UNANKARMY
3
1
Department of Soil Science, The University of Reading,
Whiteknights, Reading RG6 6DW, UK;
2
ARS-Lumle, PO Box 1,
Pokhara; and
3
ARS-Pakhribas,Dhankuta, Nepal
Introduction
Traditional subsistence farming systems in the mid-hills of Nepal derive
their sustainability from the close integration of forestry, livestock hus-
bandry and crop production, in which nutrients, particularly N, are cycled
within an apparently closed system (Jodha, 1990). With intensification of
crop production to feed a burgeoning population and exposure to external
market pressures, the linkages between elements of the traditional
system weaken, potentially causing the system to become increasingly
unsustainable, with deleterious consequences for the environment as
the system becomes increasingly leaky with respect to N (Jodha, 1990).
Creating a nitrogen budget for a hypothetical household in the mid-hills
of Nepal provides a tool for analysing these two very different scenarios,
their implications for sustainability and their possible impact on soil
organic matter levels.
This chapter first uses data gathered from the literature to identify
the fluxes of N within a hypothetical household, and by quantifying them
to indicate their relative importance. It then uses experimental data from
the field to validate two pathways for the flow of N within the household.
The first considers the flow of N into cropped land in manure and fertilizer
and out of cropped land in grains. This is a major flux pathway. The second
provides estimates of the losses of N through leaching, which are
anticipated to be large in a monsoon climate, and yet are poorly quantified.
This may reflect the rate of mineralization of soil organic matter and so the
sustainability of the system.
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