GROWTH AND YIELD RESPONSE OF BARLEY AND CHICKPEA TO WATER-STRESS UNDER 3 ENVIRONMENTS IN SOUTHEAST QUEENSLAND .2. ROOT-GROWTH AND SOIL-WATER EXTRACTION PATTERN

Root growth and water extraction of two barley cultivars, Corvette (ea rly maturing), Triumph (late maturing) and one cultivar of chickpea (A methyst at Redland Bay and Borwen at Hermitage) were compared under th ree environments: April sowing and July sowing at Redland Bay and June sowing at Hermitage Research Station, south-east Queensland. This wor k was designed to explain differences in dry matter production in term s of root growth and water uptake during the crop growth, which relied only on stored soil moisture. In the April sowing where all crops gre w well during the early stages of growth, decline in soil water with t ime for the whole profile was similar among all crops. In the winter s owings (June, July), total water use was less in chickpea than in barl ey, particularly during early stages when chickpea growth was poor. Wa ter extraction patterns of two barley cultivars were similar in all ex periments, though the late-maturing Triumph extracted slightly more wa ter than early maturing Corvette towards maturity. Water extraction fr ont velocities of the three crops were similar in each experiment. At Redland Bay, the water extraction front velocities varied from 1.4 to 1.6 cm day(-1) in the April sowing and 2.3 to 2.4 cm day(-1) in the Ju ly sowing, while they varied from 2.0 to 2.3 cm day(-1) at Hermitage. However, descent of the water extraction front commenced later in chic kpea than in barley when sown in winter months, and this resulted in l ower total water use in chickpea, particularly at Hermitage. In both s owings at Redland Bay total root length increased rapidly to about 60 days after sowing in barley, whereas the increase was slower in chickp ea. Root length density was high in the upper soil layers, and this wa s associated with high extractable soil water. In deeper layers both r oot length density and extractable soil water decreased. For a given r oot length density chickpea extracted more water than barley. These re sults indicate that the differences in root growth and water extractio n by the two barley crops were rather small and were unlikely to be th e reason for the differences in total dry matter production. Chickpea on the other hand appeared to be susceptible to low temperatures durin g early stages of growth, and this caused poor growth of both shoots a nd roots.