Farm Table says:
What is the problem?
A long-term tillage experiment was designed to assess the effect of tillage frequency and intensity on rainfed grain production and quality in the semi-arid subtropical environment of central Queensland, Australia.
What did the research involve?
There were four tillage treatments:
- traditional tillage (TT)
- stubble mulch tillage (SM)
- reduced tillage (RT)
- no till (NT)
Each with and without applied fertilizer (N+Zn). On completion, after 20 years of treatment application, all treatments were managed using no till and appropriate fertilizer (N+Zn) application for a further 7 years.
What were the key findings?
- During the 20 years when tillage treatments were being applied, the reduced tillage treatments (NT, RT and SM) outyielded TT in 10 of 22 crops grown.
- Mean yields without fertilizer were 2.0 t/ha (TT) and 2.6 t/ha (NT) while mean yields with fertilizer were 1.9 t/ha (TT) and 2.9 t/ha (NT). During the next 5 years of across-the-site no till with fertilizer, the former reduced tillage treatments out yielded the former TT in each of the 5 crops grown. For example, the long-term NT gave an average yield of 3.3 t/ha while the short-term NT, formerly TT for 20 years, produced only 2.1 t/ha – a 57% yield increase for the long-term no-till. This increase was due to both increased soil water storage and higher water use efficiency (WUE).
- Both were attributed to the development of improved soil structure, higher population densities of soil macrofauna and slightly higher soil organic carbon content. High WUE in NT was also attributed to a beneficial effect resulting from slow early growth under no till.
Results indicate it takes at least 20 years to attain the full soil benefits (physical, chemical and biological) of a no-till system. The large yield responses from the three reduced tillage treatments, during and after treatment application, were realised in part because cropping frequency exceeded the appropriate level for traditional tillage. Increased cropping frequency also results in higher levels of ground cover, which reduces soil erosion and creates a more sustainable farming system. A high-yielding, viable cropping system can also contribute towards environmental sustainability by reducing the need for further land clearing.