EFFECTS OF FERTILIZATION ON CACAO ROOT-SYSTEM IN YELLOW LATOSOL OF SOUTHERN BAHIA (BRAZIL)

The effect of fertilization with NPK and organic matter on the distribution of the root system of ten-year-old cacao trees (Theobroma cacao L.) was evaluated in areas with and without burning. The experiment was carried out in a yellow latosol (''tabuleiro'') at the Gregorio Bondar Experimental Station, with four treatments of N, P2O5 and K5O in the following proportions: treatment 1, 0, 0, 0 kg-ha-1 and treatment 2, 60, 180, 60 kg.ha-1 in areas with burning; treatment 3, 0, 0, 0 kg.ha-1 and treatment 4, 60, 90, 60 kg.ha-1 in areas without burning. In the latter two treatments, 16 t of bovine manure per hectare were added. The sources of N, P2O5 and K5O were urea, triple superphosphate and potassium chloride, respectively. Dry matter production of lateral roots was determined as well as the volume of the principal root and the trunk. The cacao tree showed a superficial root system in all treatments. Treatment 2 caused significant increases in the dry matter production of the lateral roots and resulted in a longer principal root. Compaction of the soil, due to the use of heavy machines in the preparation of the soil without burning, increased the volume of the lower third of the principal root in treatment 3 and 4. However, treatments 2 and 4 showed a tendency to a greater total volume of the principal root. Only in treatment 3 and 4 was the correlation of total volume of the principal root and volume of the trunk highly significant. In treatment 2 the correlation was negative, but not significant. For trunk volume, there was no significant difference among the treatments.