Differences in surface soil aggregation under six different crops

The effects of lupin, field pea, barley, canola, linseed and lentil crops on the surface (0-0.10 m) aggregation of a red earth at Wagga Wagga, New South Wales, were investigated in the field under identical cultivation and agronomic practices. Soil friability after cropping was in the order lupin lentil canola field pea = linseed barley. Both lupin and canola cropping produced significantly stronger aggregates (measured as tensile strength of the aggregates) than barley, lentil and field pea. There was no significant difference (P0.05) in water-stable macro-aggregation after growing the different crops. However, there was a significant (P0.05) correlation between the tensile strength of the aggregates and amount of dispersed clay released from moist soil (-10 kPa), possibly indicating different abilities of crops to modify soil bondings affecting aggregate strength.