World Soil Day

  Soil pH (acidity and alkalinity) gives an important indication of plant nutrient availability, and different crops thrive at different pH values. Soil pHmay change in response to management activities such as liming, fertilizeraddition, irrigation that leads to salt accumulation, and some forms of soil pollution. Soil pH may be measured in the field with simple indicators, or with standard laboratory measurements. It is relatively cheap, quick, and easy to determine. Amending a low (acidic) pH can lead to greatly improved crop yields.

  Characterization of the soil biota and methodological approaches  Key Functional Groups  The taxonomic diversity of the soil biota is so high that inevitably some selection must be made. The taxonomic groups described below were selected on the basis of their diverse functional significance to soil fertility (hence the term "target taxa"); and their relative ease of sampling. 1) Earthworms , which influence both soil porosity and nutrient relations through channeling, and ingestion of mineral and/or organic matter.   2) Termites and ants , which influence a) soil porosity and texture through tunnelling, soil ingestion and transport, and gallery construction; b) nutrient cycles through transport, shredding and digestion or organic matter.   3) Other macrofauna such as woodlice, millipedes and some types of insect larvae which act as litter transformers, with an important shredding action on dead plant tissue, and their predators (centipedes, larger arachnids,...