Lime was incorporated at the time of land preparation at a rate of
625 kg ha1
. Triple superphosphate (122 kg ha1
) and potassium
chloride (62.5 kg ha1
) were applied prior to planting. The crop
was grown in eleven-row plots, 6 m long, with a spacing of 0.5 m
between rows and of 0.2 m between plants within a row. A
commercial peat-based inoculum of Bradyrhizobium (mixture of
strains THA 201 and THA 205; Department of Agriculture, Ministry
of Agriculture and Cooperatives, Bangkok, Thailand) was applied as
a a water slurry over the planted rows soon after planting. At 14 days after emergence (DAE), the seedlings were thinned to two plants per hill.
A subsoil-drip-irrigation system was installed 10 cm below the soil surface. A pressure valve connected to a water meter ensured a uniform supply of a pre-calculated amount of water to each plot. Soil moisture was initially maintained at field capacity (93.1 mm in 60 cm depth) until 14 DAE in all treatments to support crop establishment. At 14 DAE, stress treatments MD and SD were begun by withholding irrigation until the soil moisture levels at 0– 60 cm of soil depth equilibrated to the predetermined levels of 75 and 56 mm in MD and SD treatments, respectively. Predetermined soil moistures for MD and SD treatments were reached at 21 DAE and 28 DAE, respectively. The MD and SD treatments were maintained at