Traditional soil structure descriptions are static and qualitative. However
, measurement of basic physical and chemical characteristics of a given soi
l structure followed by simulation modeling of crop yields and water and nu
trient regimes results in a dynamic and quantitative soil structure charact
erization. Within any given soil series, different types of structure may o
ccur as a result of different manage ment practices, and each structure typ
e can thus be characterized. This, however, is a reactive approach in which
soil structures are presented as given fact. This paper explores a proacti
ve approach in which measurement of basic soil characteristics on a series
of standardized structure samples and exploratory simulation modeling are u
sed to define an "ideal" structure, using plant growth and nutrient-use eff
iciency as indicators. Management practices to realize such an "ideal" stru
cture remain to be designed by others. Quantitative indica tors for the "id
eal" structure in the 0- to 30-cm surface soil of a loamy, mixed, mesic Typ
ic Fluvaquent (a prime agricultural soil in the Netherlands) were based on
simulated yields and associated nitrate leaching. Simulations considered wa
ter supply capacity, occurrence of bypass flow and internal catchment, leac
hing of nitrates as a function of fertilization scenarios, accessibility of
water to roots, and trafficability in spring. Exploratory simulations, usi
ng a validated model for a period of 30 yr to express temporal variability
for a complete soil profile with varying topsoil structures, showed a struc
ture consisting of 0.5-cm aggregates and a bulk density of 1.6 g cm(-3) to
be "ideal" for the agricultural land use being considered.