1 INTRODUCTION the ground is not constituted only of particle remaining portion of rocks, but also of remaining portions of plants and animals. The particles of the rocks are the mineral components and the remaining portions of plants and animals are the organic components. The present work has the intention synthetically to show to the definition of organic substance as well as its importance for the balance and fertility of the ground. Inside of this context, it is discoursed on the humificao processes and mineralizao, later becomes one brief communication the use of the organic substance in sustainable agriculture and conclusive they emphasize it importance of its diverse papers in the use and the conservation of the ground. 2 DEFINITION OF ORGANIC SUBSTANCE the organic substance of the ground is composed for the remaining portion of plants and animals. The USA organic word because one mentions the remaining portions to it of organisms, and these in turn are formed mainly by organic composites between which it has four great groups.
The carboidratos and proteins are most important, as much one as the other possesss a fast decomposition, contributing for the nutrients of the ground, as nitrogen (n), match (p) and sulphur (s). Another one is the lignina, a highly resistant composition, that persists in the ground being part of hmus. Finally, we have the lipdios (added with waxes and resins), that also they are component resistant and they contribute with sulphur (s) and match (p) for the ground (GUCHERT, ROUSSENQ GRANDSON, 2007, P. 23). Therefore we can define all material organic substance as of organic origin in high state of decomposition. 3 the IMPORTANCE OF the ORGANIC SUBSTANCE OF the GROUND the presence of organic substance is basic for the maintenance of the micron and mesobiota of the ground, therefore the action of the decompositores on this substance goes to return to the ground the necessary nutrients so that the beings livings creature that inhabit the ground can acquire energy to survive and also to keep the balance and the conservation of the ground.