STRUCTURAL-CHANGES IN A SILT LOAM UNDER LONG-TERM CONVENTIONAL OR MINIMUM TILLAGE

The effects of conventional tillage (CT) and minimum tillage (MT) on t he stability of soil aggregates, pore-size distribution, bulk density, infiltration and penetration resistance were assessed after more than 10 years of crop production at a silt loam soil in Canterbury, New Ze aland. Results show that a detrimental decrease in the aggregate stabi lity occurred if the soil was cultivated annually. Conventional tillag e slightly increased total and macro-porosity at the cultivated depth. Below this depth, however, this practice resulted in soil compaction as indicated by lower soil porosity, higher bulk density and higher pe netration resistance than those under MT. No significant differences w ere found in the infiltration rate.