DECREASING THE IMPACT OF SURFACE CRUSTING ON SEEDLING EMERGENCE BY SPRAY WETTING

A soil crust, produced by applying 44 mm of distilled water at an intensity of 290 nun/h using a rainfall simulator, was sufficiently rigid to significantly decrease emergence of barley from 76 to 40% and of oil seed rape from 82 to 61 %. If the crust was kept wet by regular application of water asa fine mist, its strength was significantly decreased, but emergence remained poor because of prolonged soil wetness. After mist-spraying the crusted surface just before emergence, per cent emergence was greater than uncrusted controls. Application to the soil of a static pressure after sowing but without crusting either had no effect or increased emergence, probably because of improved seed-soil contact. However, crusting of the compacted soil decreased emergence severely. If the crust was allowed to dry it became very strong (> 300 kPa). Mist-spraying at the time of emergence only also improved seed emergence almost to that in the uncrusted controls. Repeated mist spraying after crusting decreased the strength of the crust, but the resulting waterlogging decreased emergence to less than half those of the controls and of the treatments sprayed just before emergence only. Compared with other management techniques available for amelioration of crusted seedbeds, carefully timed fine spray watering seems to offer the best opportunity for ensuring rapid seed emergence comparable to that in uncrusted soils.