Ps. Bindraban et al., Land quality indicators for sustainable land management: proposed method for yield gap and soil nutrient balance, AGR ECO ENV, 81(2), 2000, pp. 103-112
The required increase in agricultural production to meet future food demand
will further increase pressure on land resources. Integrative indicators o
f the current status of the agricultural production capacity of land and th
eir change over time are needed for promoting land management practices to
maintain or improve land productivity and a sustainable use of natural reso
urces. It is argued that such land quality indicators should be obtained wi
th a holistic systems-oriented approach. Two land quality indicators are el
aborated that deal with (1) yield gaps, i.e. the difference of actual yield
and yield obtained under optimum management practices, or yields determine
d by the land-based natural resources, and (2) a soil nutrient balance, i.e
. the rate with which soil fertility is changing. The yield gap is based on
the calculation of land-based cereal productivity at three different level
s in terms of potential, water limited, and nutrient limited production, co
nsidering weather, soil and crop characteristics. These modelled production
levels do not incorporate socio-economic aspects, which may impede agricul
tural management in its effort to release stress because of inadequate soil
fertility, water availability and/or occurrence of pests and diseases. The
refore, location specific actual yield levels are also considered. Besides
an evaluation of the actual status of the land, it is important to consider
the rate of change. The quantification of changes in soil nutrient stocks
is crucial to identify problematic land use systems. The soil nutrient bala
nce, i.e. the net difference between gross inputs and outputs of nutrients
to the system, is used as measure for the changes. The indicator for the so
il nutrient balance combines this rate of soil nutrient change and the soil
nutrient stock. Indicators for yield gaps and soil nutrient balances are d
efined, procedures for their quantification are described and their general
applicability is discussed. (C) 2000 Elsevier Science B.V. All rights rese
rved.