IMPROVING SEEDBED CONDITIONS USING A WINGED SOWING POINT FOR DIRECT DRILLING OF WHEAT

Suitability of a winged point for sowing to improve early growth of wheat crops using direct drilling on a hardsetting soil in Cowra, New South Wales, Australia was evaluated. Soil physical conditions, including bulk density, shear strength, water content, water potential and porosity close to the seedlings, were monitored. Comparisons were made between the winged point and the conventional combine point. Results indicate that on a compacted soil (bulk density = 1.7 Mg m-3), use of the winged point encouraged downward growth of roots. Sowing with the winged point doubled the root length density in the 25-50 mm layer below seed level compared with that of the combine point 18 days after sowing. Bulk density and shear strength measurements did not explain this difference. However, analysis of epoxy-resin-impregnated seedbeds revealed the presence of more large voids (> 4 m) at 50- and 75-mm depths in the plots sown with the winged points. These large voids were in the form of fracture planes possibly created by the wing. Sowing with a combine point caused compaction, especially on a previously loosened soil (bulk density = 1.4 Mg m-3), and this was found to restrict downward growth of roots. © 1990.