Therese McBeath, Vadakattu Gupta, Bill Davoren, Stasia Kroker, Rick Llewellyn and Willie Shoobridge
CSIRO Agriculture Flagship, Waite Campus, Adelaide.
Peer review: Margaret Roper, CSIRO
Trials in the Mallee have highlighted the benefits of strong early crop establishment and nutrition, particularly on sands. Non-wetting (or water repellent) sands have presented additional challenges. Global Positional System (GPS) guided seeding is increasingly common and presents the opportunity for strategic placement of seed in relation to last season’s crop rows. Trials have been established at Karoonda and Loxton to examine when and where on-row (or near-on-row) seeding may have benefits over inter-row seeding in stubble-retained systems.
How was the project done?
In 2015 plots were sown at Karoonda and Loxton with wheat cv. Mace both on-row or inter-row at two sowing dates (April and May). At Karoonda the emphasis was on the effect of the sowing treatment on weed populations and crop performance on two contrasting soil types (a dune sand and a heavier clay loam swale). At Loxton the emphasis was on testing the effect of pre-emergent herbicide (trifluralin) on the response of crops to the position of the seed row in a sand.
• In a non-wetting sand, sowing on-row allowed seedlings to germinate in a wetter soil, with increased competitiveness against weed and disease pressures resulting in significant advantages in crop establishment and biomass production.
• Sowing on-row in sands or loam that did not express non-wetting did not capture the same level of benefits.
• Sowing crops on or very near last year’s crop row greatly suppressed grass weed populations and reduced brome grass seed set by over 70% compared to inter-row seeding.
• Early sowing in the last week of April instead of the third week of May helped to overcome the dry spring conditions and resulted in yield benefits of 28% at Loxton and up to 13% at Karoonda.
• When sowing crops on last year’s row, the potential for higher stubble borne pathogen (Take-All and Fusarium) inoculum and a greater likelihood of N tie-up after opening rains needs to be considered. However, impacts on rhizoctonia disease depend upon inherent biological fertility of soil.