<![CDATA[Abstract. The decrease in mushroom produc-tivity due to openings at the top of the baglog needs to be balanced with phosphor to increase the mushroom harvest. The research study the interaction effect of opening position plastic baglogs and concentration of phosphor fertilizers to growth and yield of oyster mushroom. The experiment has been done in Mushrooms House, Faculty of Agriculture, Winaya Mukti University, Sumedang with altitude of 850 m above sea level. It was carried out from September until December 2015. The experimental design used in this experiment was completely randomized design and treatment design was factorial. The treatment consisted of two factors: the opening position of plastic baglogs and fertilizer concentrations of phosphor fertilizer. Opening position of plastic baglogs consists of a 6 levels that b1 = vertically baglog, the top of baglog opened entirely, b2 = vertically baglog, left side baglog opened at areas 3cm x 1cm, b3 = vertically baglog, left and right side baglog opened at areas 3cm x 1cm, b4 = horizontally baglog, left and right side baglog opened entirely, b5 = the left side baglog opened at areas 3cm x 1cm, and b6 = left and right side baglog opened at areas 3cm x 1cm. The concentration of phosphor fertilizer consisted of 3 levels that p0 = 0 g L-1 solution, p1 = 0.25 g L-1 solution, and p2 = 0.50 g L-1 solution. All treatment was replicated 2 times. The results showed that there was interaction between opening position of plastic baglog and a concentration of phosphor fertilizer to height of mushroom fruiting bodies.Keywords: Baglog, Oyster Mushrooms, Phosphor Sari. Penurunan produktivitas jamur akibat bukaan plastik pada bagian atas baglog perlu diimbangi dengan pemberian fosfor untuk meningkatkan hasil panen jamur tiram. Penelitian bertujuan untuk mempelajari pengaruh interaksi posisi bukaan plastik baglog dan konsentrasi pupuk fosfor terhadap pertumbuhan dan hasil jamur tiram putih. Percobaan telah dilakukan di Kumbung Jamur Fakultas Pertanian Universitas Winaya Mukti (UNWIM), Kabupaten Sumedang dengan ketinggian tempat 850 m di atas permukaan laut dan dilaksanakan mulai dari bulan September sampai bulan Desember 2015. Rancangan percobaan yang digunakan adalah Rancangan Acak Lengkap dengan rancangan perlakuan adalah faktorial. Perlakuan terdiri dari dua faktor yaitu posisi bukaan plastik baglog dan konsentrasi pupuk fosfor. Posisi bukaan plastik baglog terdiri dari 6 taraf faktor yaitu b1 = baglog diberdirikan, bagian atas baglog dibuka seluruhnya, b2 = baglog diberdirikan, samping kiri baglog bagian tengahnya dibuka seluas 3cm x 1cm, b3 = baglog diberdirikan, samping kiri dan kanan baglog bagian tengahnya dibuka seluas 3cm x 1cm, b4 = baglog ditidurkan, samping kiri dan kanan baglog dibuka seluruhnya, b5 = baglog ditidurkan, samping kiri baglog bagian tengahnya dibuka seluas 3cm x 1 cm, dan b6 = baglog ditidurkan, samping kiri dan kanan baglog bagian tengahnya dibuka seluas 3cm x 1 cm . Konsentrasi pupuk fosfor terdiri dari 3 taraf faktor yaitu p0 = 0 g L-1 Larutan, p1 = 0,25 g L-1 Larutan , dan p2 = 0,50 g L-1 Larutan, sehingga terdiri dari 18 kombinasi perlakuan yang diulang sebanyak 2 kali. Hasil percobaan menunjukkan terjadi interaksi antara posisi bukaan plastik baglog dengan konsentrasi pupuk fosfor terhadap tinggi tubuh buah jamur.Kata kunci : Baglog, Fosfor, Jamur Tiram]]>
