The Consequences of Land Management, Particularly Compaction, on Soil Ecosystems.

One of the many current global problems is soil degradation. A major contributor to soil degradation is compaction. This is caused by overgrazing by livestock or the use of heavy agricultural machinery. Three study areas in Britain (Leicester, Wicken Fen and Loddington) and two in Kenya (Bogoria and Naivasha) were established. The following soil physical and chemical properties were measured: particle size, total porosity, penetration resistance, hydraulic conductivity, organic matter content and pH. And the following biotic properties were measured: invertebrate biodiversity, abundance, biomass, decomposition rates and carbon dioxide efflux. Firstly, a causal relationship was established between artificial compaction and the response of many soil physical and biotic properties. Total porosity, hydraulic conductivity, biodiversity, abundance and biomass, and CO2 efflux were reduced; penetration resistance increased. Organic matter content and pH remained unaffected. Different land-management practices were studied by investigating their inferred effects on the soil physical and biotic properties. Different practices were investigated as follows: woodland (Wicken Fen, Loddington and Naivasha); pasture (Wicken Fen, Loddington, Bogoria); no-till cultivation (Wicken Fen, Loddington); restoration/conservation cultivation (Bogoria), organic cultivation (Naivasha), overgrazed (Bogoria) and tilled (Wicken Fen, Loddington, Naivasha). A Compaction Index, comprising data from total porosity and penetration resistance, was devised to describe the physical effects of different management-practices on the soil ecosystem. Management practices that resulted in low Compaction Indices were no-till, pasture, restoration /conservation cultivation and organic cultivation. High values of the compaction Index were found in all tilled or overgrazed sites. Woodland often gave intermediate values, especially at Loddington. Biotic properties of the different soils were negatively correlated with the Compaction Index, with British pasture sites having the highest values for the biotic parameters, except decomposition rate, which was highest in no-till sites. The importance of the use of cultivation techniques sensitive to the health of soil ecosystems is stressed.