Abstract. The Intergovernmental Technical Panel on Soils has completed the first State of the World's Soil Resources Report. Globally soil erosion was identified as the gravest threat, leading to deteriorating water quality in developed regions and to lowering of crop yields in many developing regions. We need to increase nitrogen and phosphorus fertilizer use in infertile tropical and semi-tropical soils – the regions where the most food insecurity among us are found – while reducing global use of these products overall. Stores of soil organic carbon are critical in the global carbon balance, and national governments must set specific targets to stabilize or ideally increase soil organic carbon stores. Finally the quality of soil information available for policy formulation must be improved – the regional assessments in the State of the World's Soil Resources Report frequently base their evaluations on studies from the 1990s based on observations made in the 1980s or earlier.

No abstract

Growing cacao (Theobroma cacao L.) in an agroforestry system generates a productive use of the land, preserves the best conditions for physical, chemical and biological properties of tropical soils, and plays an important role in improving cacao production and fertility of degraded tropical soils. The aim of this study was to evaluate the impact of two long term agroforestry systems of cacao management on soil physical and chemical properties in an area originally inhabited by 30 years old native secondary forest (SF). The two agroforestry systems adapted were: improved natural agroforestry system (INAS) where trees without economic value were selectively removed to provide 50% shade and improved traditional agroforestry system (ITAS) where all native trees were cut and burnt in the location. For evaluation of the changes of soil physical and chemical properties with time due to the imposed cacao management systems, plots of 10 cacao genotypes (ICS95, UF613, CCN51, ICT1112, ICT1026, ICT2162, ICT2171, ICT2142, H35, U30) and one plot with a spontaneous hybrid were selected. Soil samples were taken at 0-20, 20-40 and 40-60 cm depths before the installation of the management systems (2004), and then followed at two years intervals. Bulk density, porosity, field capacity and wilting point varied significantly during the years of assessment in the different soil depths and under the systems assessed. Soil pH, CEC, exchangeable Mg and sum of the bases were higher in the INAS than the ITAS. In both systems, SOM, Ext. P, K and Fe, exch. K, Mg and Al+H decreased with years of cultivation; these changes were more evident in the 0-20 cm soil depth. Overall improvement of SOM and soil nutrient status was much higher in the ITAS than INAS. The levels of physical and chemical properties of soil under cacao genotypes showed a marked difference in both systems.

No abstract

No abstract

No abstract

The combined use of earthworm inoculation and organic inputs is considered an efficient way to improve traditional slash-and-burn agriculture in the humid tropics. This study tests the hypothesis that the resistant macroaggregate structure that results from earthworm activities is likely to promote sustainability by favoring water infiltration and soil aeration. Six successive crops (maize [Zea mays L.1-rice [Orym sativa L.1-cowpea [Vigna unguiculata (L.) Walp.1-rice-ricerice) were grown from March 1990 to January 1993 on a fine-sandy, siliceous, isohyperthermic Typic Paleudult previously covered by forest at Yurimaguas (Peruvian Amazonia). The experimental design included a combination of three organic residue treatments (without residues, with crop residues, and with crop residues plus green manure), with or without earthworm (Pontoscolex corefhrurus) inoculation (36 g fresh weight m-2). Soil physical properties (bulk density, total porosity, infiltration, sorptivity, soil water tension, and aggregate-size distribution) were measured before clearing and after harvesting each crop. The proportion of macroaggregates (>1 cm) increased from 25.1 to 32.7% in inoculated treatments, whereas the proportion of small aggregates (<2 cm) decreased from 33.2 to 26.1%, and no, change was observed in the intermediate (2-10 mm) category. In the control treatment, no significant changes were observed. Earthworm activities significantly increased bulk density (from 1.12 to 1.23 Mg and decreased porosity (from 58 to 53%) and sorptivity (from 0.45 to 0.15 cm s-"~). Soil water tension was also affected by the presence of earthworms through increased water uptake by larger plants and changes in soil structure. Longer term experiments are necessary to confirm that the activity of the earthworm may not eventually have detrimental effects. ARMERS of the Amazon region of Peru practice shift-F ing agriculture as the principal land use system. They slash and bum a piece of land and grow crops for 1 to 2 yr and the area is then abandoned for 5 to 10 yr with a natural regrowth fallow. In the last few years, due to land pressure, fallows have become shorter. There is insufficient time to recycle soil nutrients and, as a result, crop yields have declined. Any practice that could increase sustainability beyond the short period of cropping woulp help to decrease the need to clear primary forest and lpence contribute to reduced deforestation. Part of the problem can be solved through the use of fertilizers (Sanchez et al., 1983), but suitable soil physical proper

No abstract