Sim, RichardMoot, DerrickBrown, HTeixeira, EdmarYunusa, I2020-08-022012https://hdl.handle.net/10182/12261Dryland lucerne (Medicago sativa L.) was established at Lincoln University, New Zealand in two soils which differed in the plant available water content (PAWC). The high PAWC site is a silt loam soil with ~325 mm of water to 2.3 m. The low PAWC site had a very stony silt loam soil with only ~125 mm to 2.3 m. Both crops were sown on 10 October 2011 and established with 200 plants/m2 . The high PAWC site produced 2600 kg DM/ha shoot yield from sowing to 50% flowering compared with only 900 kg DM/ha at the low PAWC site. Both crops extracted water from the soil to a depth of ~1.2m, but the lucerne grown on the high PAWC soil extracted twice as much water to this depth. The water use efficiency (WUE) for both crops was 27.0 kg/DM/ha/mm of water used. The leaf appearance rate was 48 degree-­days per node (Tb=1°C) and was unaffected by site. Leaf area expansion rates exhibited a strong relationship with accumulated thermal time (R 2>0.94). Leaf area on the high PAWC site increased exponentially at about at 0.004 m2 leaf/m2 soil per degree­day, compared to the low PAWC site which increased linearly at a rate of 0.0009 m2 leaf/m2 soil per degree-day. Soil moisture extraction patterns indicated an extraction front velocity of 13 mm/day at both sites. Differences in lucerne yield were therefore fully attributable to differences in water extraction to a depth of 1.2 m6 pagesalfalfaConference Contribution - published