modeling sorghum response to salinity at germination stage

plant response to salinity varies at different growth stages. information on plant response to salinity at various growth stages can be used in managing saline waters for irrigation. in order to measure the quantitative response of salinity on germination of sorghum (sorghum bicolor l. moench), a greenhouse experiment was conducted in a natural saline sandy loam soil, using plastic pots with 15 cm height and 8 cm diameter. salinity treatments included a non-saline water (ec = 0.3 ds/m) and 12 saline waters with electrical conductivities of 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, and 24 ds/m. the maas and hoffman, van genuchten and hoffman, dirksen et al., and homaee et al. models were used to predict relative germinated seeds (rgs) in different soil salinity treatments and to measure quantitative effect of salinity on seed germination. the results indicated that salinity threshold value (ec*) for sorghum was 5.5 ds/m at germination, and the germination rate was reduced to 50 percent at 9 ds/m soil salinity. the predicted ec* by the models were less than the actual values measured in the experiment and also by those reported by maas and hoffman  (6.8 ds/m). the r2 values for predicting rgs by non-linear models of van- genuchten and hoffman, dirksen et al., and homaee et al. were 0.98, 0.99, and 0.98, respectively.