<![CDATA[Tanaman kubis lahan pasir pantai memiliki peranan penting dalam mencapai ketahanan pangan nasionaldan memanfaatkan peluang pasar luar musim kubis dataran tinggi dalam rangka meningkatkan pendapatanpetani dan produktivitas lahan. Teknologi spesifik lokasi yang belum lengkap menyebabkan hasil kubis masihlebih rendah daripada potensinya. Penelitian bertujuan menentukan naungan optimum bagi pertumbuhantanaman kubis di lahan pasir pantai tanpa dan dengan lapisan bentonit. Penelitian dilaksanakan di lahan pasirpantai Samas, Bantul, Daerah Istimewa Yogyakarta dari Januari 2005 sampai Mei 2006. Naungan danpemberian lapisan kedap dari campuran bentonit dan pasir 15% tebal 2 cm pada jeluk 30 cm berinteraksimempengaruhi total lengas tanah, lebar bukaan stomata, kadar klorofil, panjang akar, luas daun penutup,pertumbuhan dan hasil tanaman. Tanaman tanpa naungan dengan intensitas cahaya (ISMH) 537,7 ????mol.m-2.det-1 di lahan tanpa lapisan bentonit memiliki kadar prolin daun 7,8 mol.g-1 lebih tinggi daripada daun tanamandi lahan dengan lapisan bentonit 7,1 mol.g-1. Lapisan bentonit menyediakan lengas segera tersedia lebih lamadaripada tanpa lapisan bentonit. Tanaman kubis bawah naungan 20,5% dengan intensitas cahaya 427,3mol.m-2.det-1 di lahan tanpa lapisan kedap memberikan hasil maksimum 34,3 t.ha-1 mengikuti persamaankudratik Ybsh.tb = 4,15 +0,141 X ismh –1,65 10-4 X2ismh , (R2=0,786**). Di lahan dengan lapisan bentonit,pemberian naungan menurunkan hasil secara linier sesuai persamaan Ybsh.db = 13,0759 +0,056632 X ismh(R2=0,819 **) dengan hasil maksimum 44,4 t.ha-1, 136,6% lebih tinggi daripada lahan tanpa lapisan bentonit.Kata kunci: naungan optimum, lapisan bentonit, produktivitas kubis, lahan pasir pantai ABSTRACTCabbage in coastal sandy land has an important role in national food resilience and in taking advantageout of season market of upland cabbage for increasing farmer income and land productivity. Uncomplete specifictechnology gave yield lower than the potential. The research objectives was to determine the optimum shadingfor cabbage growth on land without and with bentonite layer application. Field experiment was carried out incoastal sandy land of Samas, Bantul, Yogyakarta Special Province from January 2005 up to May 2006.Interaction between shading and bentonite layer 15% by volume affected total soil water, stomatal aperture,chlorophyll content, root length, wrapped leaves area, growth rate and yield. The leaf of crop without shadingwith light intensity (ISMH) of 537,7 mmol.m-2.s-1 on land without bentonite layer had proline content 7,8mol.g-1 higher than that with bentonite layer application 7,1 mol.g-1. Application of bentonite layer resultedin longer readily available water than the soil without layer. Cabbage under 20,5% shading with light intensityof 427,3 mmol.m-2.s-1 on land without bentonite layer produced maximum yield 34,3 t.ha-1 according toquadratic equation Ybshs.tb = 4,15 +0,141 X ismh –1,65 10-4 X2ismh (R2=0,786**). Land with bentonite layerapplication, shading decreased the yield linearly according to equation Ybshs.db = 13,0759 +0,056632 X ismh(R2=0,819 **) with maximum yield of 44,4 t.ha-1, 136,6% higher in the land without bentonite layer.Key words: optimum shading, bentonite layer, cabbage productivity, coastal sandy land]]>
