Effect of Storage Temperature and Moisture Content on Seed Quality, Plant Establishment and Grain Yield of Cowpea

Abstract

Low grain yield of cowpea (Vigna unguiculata L. Walp) undermines its potential as a source of vegetable protein, staple and food security crop in Africa. Among factors militating against increased cowpea production is poor seed quality resulting from storage under warm and humid environments under farmers' circumstances, where over 95% of seeds are produced. Seed storage experiment was conducted at Kwadaso in the Ashanti Region of Ghana. Two popular cowpea seeds in Ghana, a pigmented (IT82E-32) and an unpigmented (IT81D-1951), were stored at 8%mc/10 ºC, 8%mc/26 ºC, 12%mc/10 ºC and 12%mc/26 ºC for 13 months, after which seed quality and field performance were assessed. Seed vigour (as indicated by decreasing percentage germination, vital staining and increasing levels of electrical conductivity, P and K contents of leachate), seedling emergence, number of plants harvested and grain yield decreased in the order of 8%mc/10 ºC, 12%mc/10 ºC, 8%mc/26 ºC and 12%mc/26 ºC, with the white-seeded variety, suffering the most deterioration and agronomic performance particularly at 12%mc/26 ºC. The mean grain yields of 1.50, 1.29, 1.44, and 0.52 t ha-1 for 8%mc/10 ºC, 12%mc/10 ºC, 8%mc/26 ºC and 12%mc/26 ºC respectively observed, provided options among the first three treatments for seed storage, depending on facilities available, the value of the seed and period of storage. Agronomic performances, including grain yields were better in the transition zone than in the forest and also better in the minor season than the major season. Correlation coefficients indicated highly dependence of grain yield on number of seedlings and plants harvested, which intend depended on the seed vigour indices, ecology and season.