An experiment was conducted in 1993 in the Greenhouse Unit of the College of Agriculture, Sana’a University, to study the effect of qat leves residue and extract on tomato seed germination. Plastic pots 20 cm in diameter were filled with soil taken from the college field. Treatment was started directly at tomato seeding and included the control (no residues or extracts), residues (10 or 30 gms/pot) added either on top of the soil or mixed with it, and extracts (either 10 or 30 gms residues in 100 cm3 water/pot). In general the results showed that residues and extracts reduced percent germination of tomato seeds .The most significant reduction resulted when 30 gms of residues broadcasted on top of the soil, which was about 48% compared to the control treatment. The results also showed that in general all treatments tended to delay germination. The most significant delay, which was about 7 days resulted from extracts made of 30 gms residues in 100 cm3 water, compared to the control treatment. It was concluded that this effect on germination may be due to the presence of allelochemicals in qat leaves, and hence it could he related to the phenomenon of allelopathy.
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