Growth Characteristics of Cowpea (Vigna unguiculata) Seedlings as Affected by Depth to Water Table

Seedlings of two Nigerian varieties of cowpea (IT82D and IT84E716)were grown together from seeds on loamy soil for 8 weeks intwo identical sloping moisture gradient boxes established outdoorsduring the dry season. Gradients of 13 cm to 79 cm depth towater table were maintained. For all growth characters determined,differences between the two varieties did not differ statisticallythough variety IT84E716 showed marginal improvement over varietyIT82D. Depth to water table had significant effects on all growthcharacteristics determined except for number of lateral shoots.No significant depth to water table x variety interactions wererecorded for any characters examined. Nodules and nodulatedroots showed maximum development in the wettest soils wherethey were relatively thick and large. The main pattern of growththat emerged was limited growth in very wet soil, maximum growthin wet soil and increasingly limited growth as the soil becamedrier. The experiment supported the hypothesis that depth towater table may provide a major edaphic control of cowpea unlessthere is frequent rainfall or irrigation. Cowpea (Vigna unguiculata cylindrica (L.) Walp.), growth characteristics, moisture gradient boxes, phenotypic plasticity, water table