Ground Cover Supplement : GC Supplement - No-till
5 NO-TILL GROUND COVER AN EVOLVING SYSTEM Soil conservation the no-till attraction A SURVEY TELLS WHY GRAINGROWERS IN WESTERN AUSTRALIA AND SOUTH AUSTRALIA HAVE ADOPTED NO-TILL FARMING -- AND WHY SOME HAVE AVOIDED IT BY BERNIE REPPEL MOST SOUTH AUSTRALIAN and Western Australian growers who responded to a 2003 weed management survey said they expected no-till cropping systems would result in reduced soil erosion. Some also said they had adopted no-till to improve timeliness of sowing and to enhance soil structure and moisture conservation. Those that had not adopted no-till said it was because of the cost of the required machinery. Further analysis has found that the two main factors determining growers’ adoption of no-till are expectations of earlier sowing in periods of less rain and the expected effectiveness of pre-emergent herbicide options, such as trifluralin, under no-till. The survey, conducted by Frank D’Emden and Rick Llewellyn for the Cooperative Research Centre for Australian Weed Management (Weeds CRC), was carried out to identify opportunities for more effective research and extension through greater understanding of no-till adoption and related graingrower perceptions. The two scientists were keen to identify the role of weed management issues in growers’ decisions to adopt no-till, and the possible conflicts between adoption of a soil conserving practice and sustainable weed management. They telephoned nearly 500 growers in WA and SA and received 303 valid responses. “In 2003, 86 per cent of WA respondents reported using no-tillage on some proportion of their cropping land, compared to 42 per cent in SA,” Mr D’Emden says. “On average, the Western Australians used the system on 79 per cent of their cropping country, compared to 70 per cent by their South Australian counterparts. But only 39 per cent of the Western Australians and 24 per cent of the South Australians no-tilled all of their cropping land in 2003.” He says about twice as many growers in SA were using some ‘direct drill’ – single pass sowing with a simultaneous full-cut cultivation – than in WA. About a third of respondents in both states use some pre-seeding cultivation, including harrows or shallow cultivation with narrow points, on some area of cropping land before low disturbance seeding with discs or knife-points. Most growers use more than one type of cultivation method. Most growers in both states believe that herbicide costs, herbicide resistance and in particular glyphosate resistance would be higher under long-term use of no- till with stubble retention (NTSR) relative to sowing with a full-cut cultivation with stubble retention (FCSR). Sixty-eight per cent of non-adopters intending to adopt no-tillage in the next five years considered the risks of herbicide resistance to be higher under NTSR than in a FCSR system, and 75 per cent expected the risk of glyphosate resistance to be higher. There were no significant differences between future adopters and future non-adopters in their perceptions of resistance or the cost of herbicide. At least a third of growers considered narrow row spacings, banding of fertiliser and weed kill in the seeding pass to be unimportant when considering seeding machinery. The perceived importance of narrow row spacings and banding of fertiliser did not differ significantly between states, but differences in the perceived importance of weed kill in the seeding pass were significant between WA and SA. Respondents from WA were more likely to say weed kill in the seeding pass was “not important”, while those from SA – among whom use of no-till was less common – were more likely to say it was either of “some importance” or “very important”. “Overall, 43 per cent of growers believed weed growth would be the same, or higher, under narrow (18 centimetre) row spacings than in wide (30cm) row spacings,” Mr D’Emden says. “Respondents from WA (59 per cent) were significantly more likely than those from SA (32 per cent) to believe that deep banding of fertiliser would lead to lower weed growth. “More than 50 per cent of growers from both states believed that no-till – as opposed to full- cut sowing – would lead to lower weed emergence.” Mr D’Emden says no-till is expected to become more common in both states, with 70 per cent of SA and 88 per cent of WA respondents planning to use the system for a proportion of their cropping by 2008. Nonetheless, no-till is still a fairly recent phenomenon in both states, with only 15 per cent of WA adopters and 23 per cent of SA adopters reporting no-till use before 1994. More information: Rick Llewellyn, 08 8303 8502, email@example.com Frank D'Emden (left) and Rick Llewellyn: understanding no-till adoption and graingrower perceptions.
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