Raphaël Marichal

Temporal variability in soil quality after organic residue application in mature oil palm plantations

Despite the dramatic changes in land-use arising from expansion of the palm oil industry, soil biodiversity in oil palm plantations has been little investigated. The present study aims to assess the effect of organic waste recycling (empty fruit bunches, EFB) on soil biodiversity in a mature plantation in Sumatra, Indonesia. A chronosequence was delineated taking into account the time between the applications of EFB and soil sampling; intervals of 1, 3, 6, 12, 18 and 24 months were compared with control plots without EFB application. Soil physical and chemical characteristics and macrofauna and nematofauna populations were analysed. The findings highlighted three distinct periods: a first disturbance period (0–6 months) showing a marked increase in pH, potassium content, base saturation and macrofauna abundance, especially ants, whereas earthworm, millipede and nematode populations were substantially reduced; a resilience period (6–18 months); and a final period (18–24 months) showing an improvement in most soil fertility parameters and a high density of earthworms, millipedes and nematodes. The impact of EFB application on soil quality changed as a function of time, and the present results explain the apparent discrepancy of some previous published results. This research is the first stage towards developing new strategies for enhancing soil biodiversity and related services for sustainable oil palm cultivation.

Impact of different land management on soil spiders (Arachnida: Araneae) in two Amazonian areas of Brazil and Colombia

Abstract The global demand for different land-use practice commodities in the Amazonia is growing, and this region is increasingly affected by the impacts of land management. The aim of this study was to evaluate the influence of land-use intensification on soil spider assemblages from six different land-use systems in Colombia and Brazil. The systems were fallows after crops and pastures, forest, crops, pastures and plantations. Spider species richness and density decreased with increasing farming management intensity. A principal component analysis (PCA) showed forests and fallows were separated from systems with stronger anthropogenic soil disturbance. The relationships of ten spider guilds differed significantly between land-uses, suggesting that they can be a reliable parameter for studies of ecological indicators.

Linking the transformation of production structures to a multidimensional sustainability assessment grid of smallholders’ oil palm plantations

Oil palm cultivation has become emblematic of the trade-off between development and conservation that growers have to face in the context of global changes. This challenge between economic growth and environmental issues and the growing public debate regarding palm oil development and use require improving data availability to avoid ideological positions. The paper is a contribution towards the establishment of a multidimensional analysis grid to assess the sustainability of palm oil production based on an empirical survey with two levels: (i) holding and (ii) plot. We first aimed to present our approach based on World Agricultural Watch methodological framework. The empirical data were collected in Kampar District, Riau province, at holding level including one to two oil palm plots showing contrasted levels of management (semi-managed and independent). Our first objective was to capture the global rationale of the holdings, to define a typology that would go beyond the usual size-based classification. After assessing the place and role of palm oil production within the household economy, we then tested a set of three-dimensional indicators (i.e. social, economic and environmental) to assess globally the impacts of oil palm development through smallholder development. In a region where oil palm cultivation tends to standardise the landscape, overwhelm the local economy and polarise the households’ activity systems, we could identify a significant heterogeneity at holding and household levels. However, the strengthening of our methodology would require a larger sample.

Forms of soil organic phosphorus at black earth sites in the Eastern Amazon

Soils containing archaeological black earth (ABE) are formed by the continuous deposition of organic residue, and maintain their high fertility even after years of cultivation. The aim of this study was to characterise and quantify the forms of organic phosphorus in areas of archaeological black earth (ABE), with a view to understanding the dynamics of the element and contributing to the development of sustainable practices of land use. Samples of 10 profiles were used from Latosols, Argisols and Gleysols located in the eastern Amazon with an anthropogenic A-horizon (ABE), using adjacent, non-anthropogenic soils as reference. The samples relative to the A, transitional and B-horizons, were subjected to sequential fractionation of P in an acid base extraction, and to further physicochemical characterisation. The acid-extracted P fraction in the A1 and B-horizons predominated over the basic-extractant labile and soluble fractions in all areas, displaying the highest percentages for the inorganic form. An increase in the labile organic phosphorus content (Pol) was found in the A1-horizon, with a reduction between the A and B-horizons of 97.6%. The amount of total phosphorus (TP) was significantly higher (6,778 mg dm-3) in the A-horizons of the ABE in comparison with the soil in the reference area (168 mg dm-3). The predominance of inorganic phosphorus over organic phosphorus was found for the total fraction, while the opposite occurred with the labile fractions. Most of the total labile P is therefore accumulated in the organic fractions of the soil, and represents an active means of supplying the nutrient to plants as it mineralises.