Busuk pangkal bawang putih yang disebabkan Fusarium oxysporum Schlecht. f.sp. cepae (Hanz.) Snyd.et. Hans. adalah penyakit paling penting di Tawangmangu sejak musim tanam 2000. Penyakit ini telahmerugikan hasil bawang putih secara ekonomi. Penelitian ini bertujuan untuk menganalisis hubungan antarakondisi lingkungan tanah terhadap intensitas busuk pangkal bawang putih di Tawangmangu. Penelitiandilakukan melalui survei pertanaman bawang putih di daerah endemik busuk pangkal di Tawangmangu,Karanganyar, Jawa Tengah. Sebanyak 30 pertanaman bawang putih yang ditentukan dengan metode purposivesampling digunakan pada penelitian ini. Sampel tanah rhizosfer untuk keperluan analisis biologi dan kimia tanahditentukan dengan metode transect system. Data yang diperoleh dianalsis regresi linier berganda dengan programSPSS. Hasil penelitian menunjukkan bahwa intensitas busuk pangkal bawang putih di Tawangmanguberhubungan dengan perubahan kondisi lingkungan tanah. Intensitas busuk pangkal bawang putih cenderungtinggi pada lahan dengan kapasitas pertukaran kation, bahan organik, dan Nitrogen yang tinggi, tetapi Fosfor danKalium yang rendah.Kata Kunci: Fusarium oxysporum, busuk pangkal, bawang putih, ekologi. ABSTRACTBasal rot of gar;ic caused by Fusarium oxysporum Schleht. F.sp. cepae (Hanz.) Snyd et. Hans. Is the mostimportant disease in tawangmangu since planting season 2000. The disease has lased garlic productioneconomically. The aim of research was to analysze the relationship beetwen soil environmental condition towardintensity basal rot of garlic in Tawangmangu. Dat was collected by survey on garlic plant of epidemic area ofbasal rot in Tawangmangu, Karangayar, Central Java. There were 30 samples of garlic determined by purposivesampling method. Rhizosper soil sample for biological and soil chemical analysis gained by transect systemmethod. Data obtained where analyzed by multiple linear regression using SPSS softwere. The result showedthat intensity of garlic basal rot in Tawangmangu has significant relationship with the change of soilenvironmenr condition. Intensity of garlic basal rot terd to increase in lard which have high cation exchangecapacity, organic material and nitrogen, but low phosphorus and kalium.Keywords: Fusarium oxysporum, basal rot, garlic, ecology.