Tactic 3 Weed control in wide-row cropping Glossary
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Tactic 2.3b Inter-row cultivation Benefits Key benefit #1 Inter-row cultivation gives the opportunity to control weeds without herbicides. Inter-row cultivation was used in grain sorghum crops in the Northern Territory in the 1950s (Phillips and Norman 1962). They found that with 18-inch and 36-inch row spacings, one inter-row cultivation was beneficial for yield whereas two cultivations removed too much soil moisture. Research conducted in northern New South Wales in the 1970s (Holland and McNamara 1982) indicated that inter-row cultivation reduced weed growth in dryland sorghum to about half that of the unweeded controls. Buhler et al (1995) reported weed control using inter- row cultivation in the range 50–75% to be common in the United States of America and many North American growers find inter-row cultivation highly effective in wide-row summer crops. Research in the USA also found that inter-row cultivation used in combination with residual herbicides can reduce the quantity of herbicide required for high levels of control (Buhler et al 1995; Forcella 2000). Despite this, there is some uncertainty regarding the level of effective weed control resulting from inter-row cultivation (Forcella 2000). Practicalities Key practicality #1 Timing of inter-row cultivation is critical to ensure maximum levels of weed control. Best weed control is obtained when the majority of the target species population has emerged and the weeds are small. In Minnesota, USA, Forcella (2000) found that to obtain maximum control of three Setaria spp. by cultivation it was necessary to wait for 60% emergence. In the Australian cotton industry it is recommended that inter-row cultivation is carried out when the soil is drying out. With this timing, more weeds are killed and any damage from tractor compaction and soil smearing from the tillage implements is minimised (Roberts and Charles 2002). Key practicality #2 Weed control is reduced if the soil is too wet. With any cultivation, weeds will successfully transplant if the soil is too wet. Soil structure can also be damaged when cultivating soil that is too wet. Key practicality #3 Heavy stubble cover may preclude the use of inter-row cultivation. Where retained stubble is dense, it may not be physically possible to carry out inter-row cultivation. Key practicality #4 Inter-row cultivation does not control weeds in the crop row, so an additional tactic must be used for the crop-row weeds. Some cultivation implements move sufficient soil from the inter-row to the crop row to smother some weeds, but this is only effective either on very small weed seedlings or if the crop is tall enough to avoid being covered. In many situations band spraying is required for crop-row weed control. Holland and McNamara (1982) found that inter-row cultivation combined with a band spray of pre-emergent atrazine over the crop row was as effective in weed control as, and used less chemical than, an overall spray of pre-emergent atrazine. Key practicality #5 Inter-row cultivation cannot be used in conjunction w ith grou n d co ver in g st u bble m u lc h t echn iqu es . Mulching the soil surface has been shown to have benefits in retaining soil moisture and suppressing weeds. Inter-row cultivation reduces the opportunity to maintain the mulch, and therefore is not a complementary tactic with mulching. Key practicality #6 Inter-row cultivation can stimulate emergence of some weed species. Cultivation is known to stimulate fresh germination of weeds. An understanding of the likely impact of cultivation on the weed species in the paddock is essential. This allows for a management plan to be put in place to control the expected weeds that do germinate. Contributors Warwick Felton, Di Holding and Andrew Storrie References Buhler, D.D., Doll, J.D., Proost, R.T. and Visocky, M.R. (1995). Integrated mechanical weeding with reduced herbicide use in conservation tillage corn production systems. Agronomy Journal 87: 507–512. Forcella, F. (2000). Rotary hoeing substitutes for two- thirds rate of soil-applied herbicide. Weed Technology 14: 298–303. Holland, J.F. and McNamara, D.W. (1982). Weed control and row-spacing in dry-land sorghum in northern New South Wales. Australian Journal of Experimental Agriculture & Animal Husbandry 22: 310–316. Phillips, L.J. and Norman, M.J.T. (1962). The influence of inter-row and intra-row cultivation on the yield of grain sorghum at Katherine, N.T. Australian Journal of Experimental Agriculture & Animal Husbandry 2: 204–208. Roberts, G. and Charles, G. (2002). Integrated weed management (IWM) – Guidelines for Australian cotton production. www.cotton.crc.org.au/Assets/ PDFFiles/WEEDpak/WPb2 .pdf Further reading Rochecouste, J. and Burgis, M. (2003). Shielded sprayers. The Conservation Farmer 4(2): 137–146. |