EFFECT OF SOIL-WATER AND TILLAGE ON COWPEA [VIGNA-UNGUICULATA (L) WALP] GROWTH AND YIELD ON A CLAY SOIL

The growth and yield of cowpea [Vigna unguiculata (L.) Walp] on a clay soil under flooding and irrigation, with and without tillage, were studied to assess the potential of growing the crop on clay soils in the wet and dry seasons of the Caribbean. Flooding the soil at the vegetative stage for 1, 2, 4, or 6 days significantly (P less-than-or-equal-to 0.05) reduced seed weight plant-1 and several vegetative plant growth parameters. The reductions were greater for the longer durations. Flooding for 1 or 2 days at the flowering and pod set stages did not significantly affect any of the plant parameters measured (plant height, leaf number, leaf area, leaf and stem dry matter, root dry matter). However, flooding for more than 2 days at the flowering stage generally significantly reduced the plant parameters. If the soil was allowed to drain for 2 days after being flooded for 2 days, the 4- and 6-day duration flooding was not as damaging as continuous flooding. Tillage did not significantly affect cowpea. Irrigation at 4- and 8-day intervals significantly (P less-than-or-equal-to 0.05) increased seed yields and there was no significant difference between 4- and 8-day irrigation intervals. Mulching plots irrigated at 8-day intervals did not significantly affect seed yield compared with the unmulched plots. Irrigating at 8-day intervals from the flowering stage only was as good as irrigating at 4- or 8-day intervals throughout the crop. The implications of the findings to all-year cowpea production on clay soils are discussed.