Strategic tillage impacts in long-term no-till

摘要

Continuous no-till (NT) has demonstrated tangible economic, environmental and soil health benefits aspects over conventional tillage (CT). However, adoption of NT has contributed to the build-up of herbicide-resistant weed populations, increased incidence of soil- and stubble-borne diseases, and stratification of nutrients and organic carbon near the soil surface. Some farmers resort to an occasional strategic tillage (ST) to manage constraints in NT systems. However, farmers who practice strict NT are concerned that even a single tillage operation may undo positive soil condition benefits accruing from NT farming systems. We selected five fields on long-term no-till (NT) managed soils (7—44 y) to represent typical conservation farming systems across north-eastern Australia. One-time tillage with either chisel tines or offset disc, or chain harrows in long-term NT helped control winter weeds. Grain yield overall showed no significant impact in both years; except in brown Sodosol (P = 0.06) in thefirst year. One-time tillage generally retained many of the soil health benefits of NT farming systems. However, tillage reduced soil moisture at most sites, but this decrease in soil moisture did not adversely affect productivity. This could be due to good rainfall received between tillage and seeding and subsequently during crop growth, which was able to replenish soil water lost from the seed zone for successful germination, seedling establishment and crop growth. These studies are allowing us to develop a conceptual framework for the potential impact of strategic tillage (ST) over time. Uptake of ST in long-term NT systems would depend on three aspects: system costs and profitability, soil health and environmental impact. For many Australian farmers, maintaining farm profitability is the priority and likely to dictate its adoption. However impacts on soil health and environment, especially the risk of erosion and the loss of soil carbon, will also influence a grower's choice to adopt ST.