Emergence of forage legume seedlings as influenced by water

Abstract

The effects of water potential and so l strength on seedling emergence of 3 forage legume species, desmanthus (Desinanthus virgatus CPI 91146), glycine (Glycine latifolia CQ 3368) and cowpea (Vigna unguiculata cv, Red Caloona) were studied in redbrown earth and black earth under a  ontrolled temperature in a growth chamber, 3 water potentials, -10, -300 and -750 kPa were applied in both soils. To achieve the desired levels of a substrate and soil strength s were placed in columns of dialysis membrane and suspended in polyethylene glyctol (PEG) solutions (molecular weight 10,000) of different concentrations until equilibrium was maintained making sure that the soil did not come in contact with PEG. Soil strength increased with decreased water potential and the effect was more rapid in red-brown earth than in black earth. Seedling emergence black earth occurred at water potentials of -10 and- 300 kPa (soil strength of 0.64 and 1.98 kg/cm2, respectively) while in the red-brown earth seedling emergence was restricted to - 10 kPa (soil strength of 1.75 kg/cm2), However, cowpea showed a greater, emergence force by emerging at water potential of -750 kPa (soil strength 2.66 kg/cm2) m the black earth and at -300 kPa (soil strength of 5.27 kg/cm2) in the red-brown earth. Time to emergence increased with decreasing water potential and increased soil strength. Seedling emergence was rapid at 0.64 and 1.75 kg/cm2 and delayed above this soil strength. It was concluded that low water potential and high soil strength restrict seedling emergence.