SENSITIVITY OF 8 CEREAL AND LEGUME SPECIES TO THE COMPACTION STATUS OF DEEP, SANDY SOILS

The effects of soil compaction and deep ripping on the growth and yield of crop (wheat, barley, oats, triticale, narrow leaf lupins and field peas) and pasture species (barrel medic and subterranean clover) were investigated for deep, sandy soils near Geraldton, Western Australia. In 1984 (an average rainfall season), growth and yields of all species were substantially reduced by soil compaction. Lupins were not included in the experiment. Barley, wheat and pea yields were reduced by around 45%; oat and triticale yields by 30%; and spring biomass of both pasture species was reduced by about 30%. The differences in response between the species were not significant (P > 0.05). In 1985 (a very dry year), amelioration of soil compaction by deep ripping increased the dry matter at flowering of all the species, including lupins, by about 30%. Severe water stress in the cereals after flowering prevented the conversion of this dry matter advantage into grain yield differences. Because of late flowering and slow maturation, the yield of the oats was significantly (P < 0.05) lower on the deep-ripped areas, compared with the yield on the compacted soil. Deep ripping increased the yield of peas by 60% and lupins by 20%, probably because flowering and seed filling were completed before the onset of severe water stress. For deep, sandy soils in mediterranean environments, maximum economic benefit would normally accrue from deep ripping prior to the cereal phase, given that current agronomic principles generally preclude the growing of peas on these soils. Selection of cereal species mainly depends on relative yields and prices; however, the results suggest that use of cultivars with rapid early growth, early flowering and quick maturity would maximise the response to compaction amelioration and minimise the risk of poor grain filling.