<p>Penelitian yang bertujuan mempelajari komposisi gulma tanaman padi sawah pada sistem bertanam secara IPAT-BO dan konvensional  telah dilaksanakan pada bulan April 2013 sampai bulan Juli 2013 di Kelompok Tani Sadang Mukti, Kampung Sadang Sari, Kabupaten Bandung Jawa Barat yang terletak pada ketinggian 668 m di atas permukaan laut. Penelitian menggunakan metode eksperimen, dengan Rancangan Petak Terpisah, 3 kali ulangan, sebagai petak utama  yaitu faktor metode pengairan (M), yang terdiri dari pengairan secara IPAT-BO dan konvensional, sedangkan anak petak adalah jarak tanam (J), yang terdiri dari : 30 x 35 cm, 30 x 25 cm, 35 x 35 cm,dan 30 x 30 cm. Hasil penelitian menunjukkan bahwa terjadi interaksi antara metode pengairan dan jarak tanam terhadap nilai jumlah dominasi gulma, dan bobot kering gulma.Gulma yang dominan pada perlakuan IPAT-BO lebih banyak dibanding perlakuan konvensional, sedangkan bobot kering gulma terberat terjadi pada metode IPAT-BO dengan jarak tanam 35 cm x 35 cm.</p><p> </p><p>The research was aimed to assess the effect of different plant spacing to weed composition and lowland rice yield in SOBARI and conventional irrigation methods. The experiment had been conducted in Farmers Groups Sadang Mukti, Sadang Sari Village, Bandung District, West Java at 668 m above sea level, from April 2013 to July 2013. It was arranged in split plot design, consisted of two factor, irrigation methods factor (M) as main plot, namely: irrigation methods in SOBARI (m₁) and conventional (m₂),subplot was plant spacing factor (J), which consisted of four levels of factors, namely: 30 x 35 cm, 30 x 25 cm, 35 x 35 cm, and 30 x 30 cm. The results showed that there was interaction between irrigation method and plant spacing on the value of domination number of weeds, and weed dry weight. Dominantweeds in SOBARI method were more than conventional treatment, weed dry weight in SOBARI method with spacing of 35 cm x 35 cm had greater than the other treatments.</p>