EFFECTS OF HEAVY ADDITIONS OF ORGANIC RESIDUES ON PHYSICAL CHARACTERISTICS OF 3 SOIL TYPES IN QUEENSLAND, AUSTRALIA

Three contrasting soil types from separate horticultural farms producing celery, broccoli and lettuce were investigated for the effects on some physical properties in response to heavy additions (usually 50 t ha-1 year-1) of organic residues. Material such as manure from poultry, cattle and sheep, as well as sawdust, were added and incorporated to a depth of 150 mm for each farm. The soils are located in the Darling Downs region of southeast Queensland, Australia. Increases in soil water retention were recorded at all matric potentials from - 10 to - 1500 kPa for the gritty podzolic soil, for all matric potentials up to - 1500 kPa for the krasnozem, but at no matric potentials for the black earth. Heavy additions of organic residues resulted in greatly increased soil strength parameters of cohesion for the gritty podzolic, but had little effect on the other soils.