Strategic tillage: threat to no-till benefits?
Author: Rachel Bowman | Date: 17 May 2013
- Strategic tillage and moisture conservation remain a balancing act for no-till farmers.
- Strategic tillage may offer benefits in controlling resistant or hard-to-control weeds.
- Single tillage events can reduce moisture but may boost yields and profitability in the presence of a high weed burden.
- Future trial work is scheduled to determine the best timing for strategic tillage.
- Early research results show one-time tillage may be able to improve grain yields and profitability without losing the benefits of no-till.
Dr Yash Dang, Queensland Department of Science, Information Technology, Innovation and the Arts (DSITIA) senior scientist (soil and nutrient management) says balancing soil moisture and weed control has been a dilemma for growers choosing to use strategic tillage to manage difficult-control-weeds within an established no-till farming system.
“Tillage reduced soil moisture at most sites; however, this decrease in soil moisture did not adversely affect productivity.
“This could be due to good rainfall received between tillage and prior to seeding and during the crop this year.
“The occurrence of rain between the tillage and sowing or immediately post-sowing is necessary to replenish soil water lost from the seed zone.”
This suggests timing of tillage and taking seasonal forecast into consideration is important, Dr Dang said.
Dr Rohan Rainbow, Grains Research and Development Corporation (GRDC) manager crop protection says GRDC is funding the research in its bid to help growers manage the growing issue of herbicide resistance.
“Conserving soil moisture is the key to maximising yields in the northern grains region from Dubbo in NSW to Emerald in central Queensland. We certainly don’t want to jeopardise the benefits gained from no-till,” Dr Rainbow said.
“However some weeds, particularly in fallows, can be effectively controlled by a well-timed strategic tillage.
“We are looking forward to more results emerging from the research but the key seems to be timing the tillage with imminent rainfall events where possible.”
Five fields at sites including Biloela, Condamine, Moonie and Warwick, Queensland and Wee Waa, NSW were selected for the trials.
Dr Dang said grain yields showed little response to tillage and one-time tillage using either chisel or offset disc tended to increase grain yields at all the sites but only significantly at the Condamine site.
A second tillage pass did not further improve the grain yield either at Biloela or Condamine sites and the Kelly chain had no effect on grain yield, he said.
“Net returns per hectare from one-time tillage using either chisel or offset disc in long-term no-till systems were estimated to range from $2.5 to $35.8.
“The highest net return was seen at the Condamine site, which could be the result of higher chickpea prices.
“A second tillage pass at Biloela and Condamine did not further increase net returns.
“Among tillage implements, chisel tillage resulted in higher net returns than offset disc at Moonie site, and similarly chisel tillage gave better returns than Kelly chain at Wee Waa.”
Dr Dang said tillage treatment generally slightly lowered bulk density, soil moisture prior to seeding, soil carbon and available phosphorus in the surface 0-0.1metre soil depth.
“Significant negative effect of one-time tillage on soil organic carbon and available phosphorus at the Moonie and Wee Waa sites and total soil microbial activity at Warwick site did not result in adverse effects on productivity and profitability.
“One potential negative effect from tillage is the reduced soil moisture at most sites. However, in this season this decrease in soil moisture did not adversely affect productivity.
“This could be due to good rainfall received between tillage and prior to seeding and during the crop this year and suggests the importance of timing of tillage and taking seasonal forecast into consideration.”
He says it is also important to note that at all sites in this season, all tillage operations were carried out later in the summer fallow period, after March 3.
Tillage earlier in the fallow period could have had a far greater impact on fallow efficiency and water storage for the following crop, he said.
The benefits of no-till systems have been widely recognised for many years – with significant benefits in yield and crop performance especially in lower rainfall environments, erosion control and improved soil health.
Dr Dang says no-till has revolutionised agricultural systems by allowing growers to manage greater amounts of land with reduced energy, machinery and labour inputs.
“Despite these tangible benefits, recent survey of 55 growers and advisers in the northern grains region indicated that diseases such as crown rot and yellow leaf spot and hard-to-kill weeds such as fleabane,feathertop Rhodes, windmill grass and glyphosate resistant barnyard and liverseed grass, tend to be bigger problems in no-till systems than in systems where tillage is regularly used.
“Recent wet seasons have favoured disease and weed development in no-till farming systems and have put pressure on growers’ management strategies to combat heavy infestations of weeds and diseases.
“Issues with cost effective management of glyphosate tolerant or resistant weeds has led to an increasing number of growers and their advisors to seriously consider the merits of re-introducing the plough in certain situations.”
He said many growers are concerned that even a single tillage operation may be enough to send their soil conditions back to the start of conservation farming systems.
“Many growers are keen to know what would be the level of impact of occasional tillage in no-till arming systems on their soil health and production system.”
Caption: GRDC-funded research into strategic tillage shows potential gains in profitability and productivity.
Dr Yash Dang, Senior Scientist (Soil and Nutrient Management)
Queensland Department of Science, Information Technology, Innovation and the Arts (DSITIA)
07 4529 1245
Rachel Bowman, Senior Consultant, Cox Inall Communications
07 3846 43800412 290 673
GRDC Project Code ERM00003
Region North, South, West