Changes in the soil quality attributes of continuous no-till farming systems following a strategic tillage

Abstract

The adoption of no-till farming systems has greatly reduced energy and machinery inputs while significantly improving soil health and productivity. However, the control of crop weeds and diseases in no-till (NT) systems has become increasingly difficult for landholders in Australia's northern grains regions, with occasional strategic tillage (ST) being considered as a potential management option. This study investigated the effects of occasional ST on physical, chemical and biological soil properties, productivity, and weed control on five long-term (7-44 years) NT-managed soils. The study area extended from Biloela (Vertosol, 666mm annual rainfall), Condamine (Sodosol, 624mm annual rainfall), Moonie (Dermosol, 636mm annual rainfall) and Warwick (Vertosol, 675mm annual rainfall) in Queensland to Wee Waa (Vertosol, 582mm annual rainfall) in New South Wales. Tillage treatments included chisel, offset disc and prickle-disc chain with various timings and frequencies. Soil samples (0-0.3m) obtained 3 and 12 months after occasional ST were analysed for total and particulate organic carbon (TOC, POC), available phosphorus (P), bulk density, soil water, and microbial enzymatic activity. In-crop weed density was also recorded. One-time tillage, with chisel tines, offset disc or chain harrows, in long-term NT helped to control winter weeds in the first year, with variable results in the second year. Grain yield overall showed no significant impact in either year, except on the Brown Sodosol (P≤0.08) in the first year. The initial impacts of strategic tillage on soil water were largely restricted to the 0-0.1m depth range, with slight, non-significant decreases occurring. Available P, TOC, POC and total microbial enzymatic activity were not significantly impacted by either cultivation frequency or implement type. The use of an occasional ST for the purpose of weed control could be utilised as a viable management option for NT systems in the region without impacting on long-term productivity.