SOIL TYPE INFLUENCES RELATIVE YIELD OF BARLEY AND WHEAT IN A MEDITERRANEAN-TYPE ENVIRONMENT

In the eastern wheatbelt of Western Australia the yield of barley rela tive to wheat is influenced by soil type. Field trials studied detaile d aspects of growth, development, yield and water use of a range of ba rley and wheat cultivars on 2 soil types at 2 locations to identify th ose factors that lead to the differential relative yields. Barley had greater grain yields than wheat on both fine and coarse textured soils . On both soil types barley had a greater number of mainstem leaves wh ich appeared faster than those of wheat and this was associated with g reater tillering (6.5 v. 3.5 shoots/plant), higher GAI and greater dry matter production (845 v. 804 g/m2). The difference in yield between the two species was greater on the fine textured soil (15 v. 7 %). Bar ley also had greater harvest index than wheat (6-15 %), and this combi ned with greater dry matter production on the fine textured soil led t o a larger yield advantage over wheat than occurred on the coarse text ured soil. Water use efficiency was greater for barley than for wheat on both soils. The greater yield advantage of barley over wheat on the fine textured soil was the result of greater biomass production by ba rley and greater harvest index. Differences in pattern of water use, a nd water use efficiency of grain production were associated with great er barley yields but are not themselves considered to be the cause of relative yield differences across soil types. The possible implication s of factors such as intrinsic nutrient supply on the 2 soil types in relation to observed yield differences are discussed.