The Role of Soil Organic Matter and Manures in Sustainable Nutrient Cycling - Sustainable Management of Soil Organic Matter - page 273

Estimation of N Fluxes for Hypothetical Households
Pilbeam et al . (2000) synthesize literature values to define the characteris-
tics of a hypothetical household in the mid-hills of Nepal. This household
owns 1 ha of land divided in a 2 : 1 ratio between rain-fed bench terraces
( bari land) and irrigated lowland ( khet land). Characteristically, two crops
are grown per year on each land type; maize-millet is the dominant rotation
on bari land, while rice-wheat rotations dominate khet land. All households
own a number of both large and small ruminants, and some poultry. An
indeterminate number of trees are grown on the land owned by a house-
hold. These together with crop residues and grasses growing on terrace
risers and wasteland provide fodder for the livestock. The proportion of
animal feed coming from within the household boundary relative to that
from outside is not known.
Figure 4.7.1 presents the size of N pools and the fluxes of N across the
boundary of the household (which in the figure is indicated by the box) in a
single year. Some fluxes have not been quantified, either because they are
not known currently (e.g. gaseous N losses from soil), or because the
relevant data were not readily available (e.g. losses of N in wool, milk and
meat). Of the quantified annual fluxes, the more significant inputs of N
Fig. 4.7.1. Magnitude of N fluxes over a year for a hypothetical household owning 1 ha of land in
the mid-hills of Nepal. Arrows represent fluxes. ?represent unknown quantities.