Abstract Total phosphorus ( TP ) build‐up in agricultural soils represents both a threat to aquatic ecosystems and a valuable resource for future crop production, given the context of increasing food demand combined with the rapid depletion of the world's phosphate reserves. Therefore, it is crucially important (i) to identify the main factors controlling topsoil TP and (ii) to develop methods for mapping its spatial distribution. Multiple linear regression models were used with two distinct approaches to calculate TP and covariates linked to the P cycle. Firstly, covariates were selected from the Réseau de Mesures de la Qualité des Sols database, the French soil monitoring network, which consists of soil samples collected from 2158 sites on a 16‐km regular grid. Secondly, covariates were selected to map TP from spatially exhaustive datasets in France. The first approach explains 80% of variability in topsoil TP . The variables selected are linked to the autochthonous origin of P (parent material), to allochthonous origin (organic carbon and nitrogen contents) and to the retention capacity of soil (Al, Fe, Ca and clay contents). The predicted map obtained from the second approach provides a mean TP of 0.76 g/kg. This study demonstrates that creating national scale maps of TP , based on detailed soil sampling and many variables, is feasible and can be used to model the P cycle and P transfer processes. Such maps can be used in P erosion and transfer models over river basins, and therefore to predict P exports to surface waters.
The need for soil data has largely increased worldwide given the growing general concern about the maintenance and recovery of ecosystem resources and services. The development of digital soil mapping (DSM) is often seen as a means for answering this demand. In France, the national soil mapping strategy has been defined in the early 1990s within the Soil Inventory, Management and Conservation Programme (IGCS) and based on conventional soil mapping approaches. Now, small-scale soil map coverage of France has been almost achieved, soil data needs have evolved and DSM approaches have matured. The question therefore arises of what should be the future soil mapping strategy in France so as to foster soil mapping, better answer end-users needs and raise societal concern about soils. To answer this issue, we present in this paper a prospective analysis of the French national soil mapping strategy, which included i) a survey of the needs and difficulties expressed by producers, managers and users of soil data and ii) a foresight study of potential future scenarios for the development of soil mapping that takes advantage of DSM approaches. The survey indicated that soil information needs are high in terms of soil attributes, spatial resolution and accuracy and go beyond the data and maps presently available for France. The survey also showed that DSM methods remain little known outside the academic sector. The foresight study led to two main outputs. The first is to propose two complementary spatial sampling strategies for new data acquisition: i) upgrading the density of observed soil profiles to homogenize the accuracy of 1:250,000 soil maps for France and ii) improving the knowledge of local soil distribution patterns in the French regions by developing detailed mapping of reference areas, representative of the local soil patterns. The second output is a set of four possible scenarios for the development of soil mapping that differ according to the expected level of concern about soils that may exist in France in the future. The comparison of the scenarios led to several recommendations for favouring soil mapping, acquisition of new soil data and dissemination of soil knowledge. The recommendations include awareness raising about soil mapping and its potential for answering many environmental challenges, capacity building of soil surveyors and soil data users for DSM approaches, and improved quality assessment of soil maps to guide users and stimulate new investments of map producers. This certainly involves renewed public support before market development of soil mapping activities can take place and become the main support for soil mapping in France.
Abstract This paper reports spatial and temporal changes at the regional level in soil organic carbon (SOC) using a soil‐test database. A total of 23 329 SOC test values recorded between 1990 and 2004 by certified commercial laboratories and collected in a mountainous French region (Franche‐Comté) were integrated in a database. Results show a strong trend in organic carbon content, mainly related to elevation. A large loss in SOC was observed over the survey period. This loss correlated with baseline SOC content with greater loss from soils with higher carbon content. This loss is likely to be due to both changes in land use from permanent grassland to cultivation and to an increase in temperature during the survey period. Our study demonstrates that past soil‐test results which were not originally intended for monitoring can provide an alternative method for detecting changes in SOC.
The 1:250,000 soil mapping program of France is nearly complete. Although mapping has been conducted using conventional methods, there is a discernible need to obtain more precise soil data using other methods, and this is attracting considerable attention. However, it is currently not possible to implement a conventional and systematic program throughout the French territory, as the cost of acquiring new data on a finer scale is too high. In light of this, the Ministry of Agriculture commissioned a national survey to determine the needs of soil mapping in France, which asked questions to soil data producers and end-users. The results presented here summarize the main needs expressed by end-users. The main topics covered by soil mapping applications are identified in addition to the main mismatches between topics currently covered using available soil maps and the needs of end-users. Certain priorities for producing new soil information are identified in relation to geographical environments and settings, soil attributes, the spatial resolution of maps and the use of uncertainty estimates. Digital Soil Mapping is identified as a method that can bridge economic, scientific and practical considerations, but it requires dedicated efforts in order to build capacity. Finally, there is discussion of how the consideration of user needs can be employed to enhance the contribution of a new Digital Soil Mapping era, and to launch an operational soil security paradigm in France.
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