The strategic use of minimum tillage within conservation agriculture in southern New South Wales, Australia

Abstract

Occasional, strategically applied tillage within an otherwise no-till system conflicts with the philosophical ideal of zero disturbance of soil, yet is often needed to manage soil constraints, pests and weeds. This study reports the impacts of a single strategic tillage applied to long term no-till soils (10–16 years) with a scarifier or offset discs, compared with ongoing no-till, on soil conditions and crop growth over four seasons at three locations in southern New South Wales, Australia. The tillage occurred just prior to sowing in autumn and under different management conditions at each site. The effect of a single tillage on wet aggregate stability (WAS) ranged from 0 to 14% loss of macro-aggregates, and the recovery time was generally one or two years with the exception of one site-year. The effect of a single tillage on saturated hydraulic conductivity was not statistically significant. Crop establishment was decreased by tillage in some site-years but effects on crop dry matter and grain yield tended to be neutral or minor. In most cases, seasonal effects and crop sequence had a much larger effect on crop productivity than tillage.The results demonstrated that strategic use of tillage within an otherwise no-till system generated minor and short term impacts on soil conditions. Strategic tillage therefore provides a tool for more flexible management of soil, pest and weed constraints to ensure long term productivity and sustainability of dryland mixed farming systems in southern New South Wales, Australia.