The study evaluated the relationship among soil thermal conductivity (I») organic matter, activity and microbial biomass. In three systems of passion fruit crop (ecological, transitional and conventional) in the municipality of Toro, Valle del Cauca, Colombia. In samples taken at random in two depths (0-15 and 15-30 cm), biological properties microbial activity (C-CO2); microbial biomass (microbial C) - fumigation, extraction - and physical and chemical properties (organic matter, pH, humidity, texture, apparent density, porosity (traditional methods) and thermal conductivity of the soil (electrothermal method) were measured. The results were analyzed program SAS through models of lineal regression, LSD and Duncan. There were highly significant differences in organic matter, activity and microbial biomass and thermal conductivity of the soil at both depths.The most notorious among ecological and conventional crops. High correlations of direct proportionality were calculated among thermal conductivity of the soil (I») and soil organic matter, for the three crop systems. The ecological crop increased these properties and activity and microbial biomass. Key words: Passiflora edulis Sims var flavicarpa, crop systems, soil thermal conductivity, organic matter, activity and microbial biomass.