Abstract
Pulse production is decreased when grown on waterlogged soil in rice-based cropping. This study evaluated four pulse crops-grass pea, field pea, cowpea and lentil-to find out their responses to waterlogging (WL) stress at emergence and vegetative stages. The treatment levels at emergence were drained control, 4-, 7- and 10-day WL, while in the vegetative stage they were drained control, 6-, 10- and 14-day WL. In the emergence stage, %emergence was significantly reduced as WL duration increased. After 10-day WL, emergence was reduced to 65% for grass pea, 30% for field pea, 5% for lentil and 7% for cowpea. At the vegetative stage, in both the WL and recovery phases, the WL treatment reduced plant height, tap root length, shoot and root dry mass compared to those in drained control with a significant difference in crops. In recovery as compared to the WL phase at 14-day WL, the chlorophyll content was increased 15% in cowpea and 14% in grass pea but decreased in field pea (26%) and lentil (35%). Similarly, in the recovery phase at 14-day WL, shoot relative growth rates (RGRs) of cowpea, grass pea, field pea and lentil were 20, 66, 10 and 5 mg plant-1 d-1; which were 66%, 70%, 8% and 14% of drained control, respectively. The RGR of root at 14-day WL was also higher in cowpea and grass pea with the rate of 13.8 and 16 mg-1 plant-1 d-1, respectively; in sharp contrast to a reduction of -4.3 mg-1 plant-1 d-1 in field pea and -3.9 mg-1 plant-1 d-1 for lentil than drained control. Furthermore, the higher number of adventitious roots was found in cowpea (14) and grass (9) pea than in field pea (6) and lentil (4). Comparison between growth stages, grass pea was tolerant to WL in both stages. Cowpea was WL sensitive at emergence, but tolerant to vegetative stage. Field pea was moderately tolerant to emergence but was sensitive at vegetative stage. Lentil was sensitive at WL at both stages. These novel insights will allow the fitting of winter pulses to various cropping systems according to the perceived risk of WL at various growth stages.
