The objective of this work was to evaluate the chemical alterations of the substrate in the cultivation of pepper in coconut husk fiber, in a protected environ-ment. Initially, 160 pepper plants ('Eppo') were divided into four blocks, where two pots per block were analyzed every 21 days after transplanting. The cultivation of pepper was carried out in plastic pots of 13 L, containing coconut husk fiber, and placed in double rows with a spacing of 0.5×0.8 m between single rows and 1.10 m between double rows. After removal of the plants from the pots, individual samples of substrate (approximately 1 L) were collected from each pot and dried at ambient temperature. Electrical conductivity (EC), pH, and levels of NH 4 + -N, NO 3 -, P and K were determined for all periods of the cultivation. These analyses were performed using the method of extraction 1:1.5 v/v. For the conditions which the experiment was conducted, there was an increase in substrate EC, as well as in the levels of nitrogen, phosphorus and potassium. INTRODUCTION In Brazil, pepper is one of the vegetables species that is most popular and widely cultivated. It is very appreciated in its raw form, due to the delicious flavor. It is considered one of the ten species of major economic importance in the Brazilian vegetable market. Growing areas of pepper in Brazil have shown many problems with root-knot nematodes (Meloidogyne spp.), especially Meloidogyne incognita and M. mayaguensis (recently identified) which have reduced productivity. Currently, there are no cultivars of pepper resistant to M. incognita and M. mayaguensis, which causes a marked change in cultivation areas or enhances the necessity of treating the soil, which has a great environmental impact. One possible solution to this problem is cultivating in pots or bags filled with substrate. In this context, coconut husk fiber, a residue from the coconut industry has been introduced as a substrate. The importance of the recycling of nutrients and the utilization of organic residues in agriculture should also be emphasized, where these practices together with modern techniques of production are aimed at increasing productivity and reducing environmental impacts. Growing pepper in substrate would thereby make its cultivation possible in areas contaminated with Meloidogyne incognita and M. mayaguensis. The evaluation of the quality of a substrate is based on its physical and chemical characterization. Among the chemical properties, pH, EC and level of nutrients are important. The pH determines the acidity of a medium and is an important chemical criterion for the development of the plant, due to its direct effect on the availability of nutrients, mainly micronutrients (Kämpf, 2000). According to the cited author, the measure of EC provides an estimate of the content of soluble salts of a growth medium, as dissolved ions