The qualitative and quantitative contribution in organic carbon (C-org) and also the bioactivity and P content in Santa Bárbara soil were evaluated using the conservation no tillage system. Conventional tillage and conservation no-tillage were compared at three strata. The methods for fractionating C-org, carbohydrates, and dehydrogenases were adapted to volcanic soils. The percentages of C-org at the 3 soil strata were 6.30, 4.49 and 1.03 using traditional tillage, whereas they increased to 9.34, 6.86 and 5.06 using no-tillage system. The higher Carbon content contributed with stabilized matter, i.e., the percentages obtained using traditional tillage were 1.91, 1.82 and 0.50 for C-humic acid and 0.78, 0.66 and 0.72 for C-fulvic acid; whereas those using notillage system were 4.19,4.08 and 3.92, and 0.97, 0.98, and 0.60 respectively. The labile pool of C-org, i.e. ,carbohydrates, also exhibited a positive variation in all levels. This is essential for biological activation, as can be concluded by observing the dehydrogenase activity. The total P content contribution using no-tillage was also improved: 2310,2205,1939 mg/kg instead of 1910,1417 and 1190 mg/kg using the conventional method.