AGRITEK VOLUME 17 EDISI ULANG TAHUN KE-18 JULI 2008 1232-1238 ISSN: 0852-5426 1 EFFECT OF DURATION OF INCORPORATION OF COMMON SUNFLOWER (Helianthus annuus L.) LEAVES IN THE SOIL ON THE GERMINATION OF SELECTED WEEDS AND CROPS Mohammad Cholid Indonesian Tobacco and Fibre Crops Research Institute ABSTRACT Experiment were conducted with the following objectives : To determine the effect of length of incorporating common sunflower leaves in the soil on growth of itchgrass [Rottboellia. cochinchinensis (Lour)W.D. Clayton], barnyardgrass (Echinochloa glabrescens Munro ex Hook.f.), water purslane [Ludwigia octovalvis (Jacq.) Raven], mungbean (Vigna radiata L.), and rice (Oryza sativa L.). Treatments were replicated three times in a factorial completely randomized design. The first factor were species of crops/weeds: rice, mungbean, itchgrass, barnyardgrass, water purslane. The Second factor were duration of incorporation of common sunflower residues in soil: untreated, 0 day, 7 days, dan 14 days. The Result indicated that incorporation of common sunflower leaves in the soil at seeding (0 day) reduced seed germination and seedling growth of all test species. The leaves incorporated in the soil decreased germination and further growth of all test plant seedlings according to the duration of incorporation in the following order: 0 day (at seeding) > 7 days before seeding > 14 days before seeding. Incorporated common sunflower leaves in the soil had inhibitory potential on water purslane and itchgrass, but less or no inhibition on rice and mungbean. It may be inferred that common sunflower leaves may be used for effective itchgrass and water purslane controls, without damaging mungbean and rice plants. Barnyardgrass was affected by leaf residues only at germination and initial growth, but less affected at further growth stage. Key word: Allelopathic, Helianthus annuus L, crops, weeds ABSTRAK Pengaruh lama pencampuran residu daun bunga matahari (Helianthus annuus L.) dalam tanah pada perkecambahan beberapa tanaman dan gulma. Penelitian ini bertujuan untuk mengevaluasi pengaruh lama pencampuran residu dari daun tanaman bunga matahari dengan tanah terhadap pertumbuhan Rottboellia cochinchinensis (Lour)W.D. Clayton, Echinochloa glabrescens Munro ex Hook.f., Ludwigia octovalvis (Jacq.) Raven, kacang hijau (Vigna radiata L.), dan padi (Oryza sativa L.). Rancangan Percobaan yang digunakan adalah Rancangan Acak Kelompok Faktorial, dengan 3 ulangan. Faktor pertama adalah spesies tanaman dan gulma yaitu: padi, kacang hijau, Rottboellia. Cochinchinensis, Echinochloa glabrescens, dan Ludwigia octovalvis. Faktor kedua adalah lama pencampuran yaitu : tanpa residu; 0 (saat tanam), 7 hari sebelum tanam (hbt), 14 hbt. Hasil percobaan menunjukkan bahwa pencampuran