Influence of Residual Allelopathic Effects of the Seed Powder of Watercress or Mustard on the Following Cowpea Plant and Its Associated Weeds

Cowpea (Vigna unguiculata (L.) Walp.) plants were sown in the same pots after the harvest of tomato plants which were previously treated with different rates (5, 10, 15, 30 and 45g/kg soil) of seed powder of two Brassicaceae plants, watercress (Eruca Sativa M.) or mustard (Sinapis alba L.) compared to those treated with Basamid herbicide at 0.2 g/pot. This work was done in the greenhouse of the Egyptian National Research Centre during the two successive summer seasons of 2017 and 2018. The obtained results indicated that all previous treatments used to tomato were significantly minimized the weight (fresh and dry) of grasses, broad-leaved and the total weeds associated with the following cowpea plants, at 45 and 85 days after sowing (DAS). Generally, all treatments with watercress were more effective than mustard in controlling both broad leaved weeds and grasses. Moreover, broad leaved weeds were more susceptible than grasses. The results also showed that all mentioned treatments had significant effect on cowpea plants, significantly increasing most growth parameters and yield and yield components. The results indicated that all tested treatments had no toxic effects on the following cowpea plants.