Quantifying And Modeling Soil Strucure Dynamics PDF Download

Methodology for defining sustainable land management practices is increasingly needed to overcome environmental problems and to maintain production potentials. From the large amount of definitions for sustainable management the following was used here: "Sustainable land management combines technologies, policies and activities aimed at integrating socio- economic principles with enviromnental concerns so as to simultaneously: (i) maintain or enhance production and services; (ii) reduce the level of production risk; (iii) protect the potential of natural resources and prevent degradation of soil and water quality; (iv) be economically viable and (v) socially acceptable". Indicators to quantify sustainability are used to analyse the effects of different management types on the soil structure within one soil series in the Netherlands, a loamy, mixed, mesic, Typic Fluvaquent. It is logical to concentrate on soil structure when evaluating and comparing the effects of different management practices as they reflect management practices at an integrated level. Comparison was focused on three soil structure types, formed by different management practices. (i) A biodynamic system (Bio) where no chemical crop protection or commercial fertiliser has been applied since 1924. Animal manure and a crop rotation system with clover are intended to supply the required nutrients. (ii) A conventional system (Conv) representing a management system that is most common in the region. (iii) A system which has been permanently meadow since 1947 (Perm). The biodynamic and conventional system were compared by converting "static" soil parameters, like organic matter content, bulk density, hydraulic characteristics, into a "dynamic" assessment by using a simulation model to calculate water-limlited productivity. A thorough soil characterisation was made, including morphological and physical characterisation as well as monitoring of soil water contents and groundwater levels. Results of the comparison between simulated and measured moisture contents were such that the model was considered to be adequately validated. The simulated water-limited productivity for potatoes was significantly higher for the biodynamic system, indicating a favourable effect of the higher organic matter content. Modern mechanised agricultural practices require soils to be able to be subjected to tillage and traffic, without adverse effects on soil structure. Threshold values for workability and trafficability were obtained for the three management types. Workability by the Atterberg test, trafficability by penetrometer measurements and an additional field-traffic experiment. Threshold values for Conv were most favourable, i.e. during relatively wet conditions Conv could still be tilled and trafficked. Periods of workability and trafficability were obtained by combining measured threshold values with simulated moisture contents. Conv had the longest workable and trafficable period in a year followed by Perm and Bio, respectively. Soil survey could focus in future on defining sustainable forms of landuse, considering that soils within one soil series are not similar. Farm management information combined with quantifying the associated soil structure types by simulation models, can form the basis for defining sustainable management systems for the soil series being studied. As many soil surveys are completed all over the world, the proposed procedure appears to be a worthwhile continuation of the rich tradition of soil survey research.