EVALUATION OF ROOTS SYSTEM DISTRIBUTION I N TALL COCONUT CULTIVARS

Root system distribution was evaluated in Tonga Tall, Rotuma Tall, Ren nell Tall, Polynesia Tall, West African Tall and Praia do Forte Brazil Tall coconut cultivars, with the aim of identifying the materials mos t suitable for planting in northeastern Brazil, the country's main coc onut producing region, based on root system performance. The poor rain fall distribution and the occurrence of extended water deficits someti mes exceeding 500 mm/year have a major impact on coconut development, hence the low mean national productivity of 30 fruits/tree/year. The s amples were taken after the dry and rainy seasons al lateral distance from the coconut stem of 0.6 m, 1.8 m, 3.0 m and 4.2 m and at depths o f 0 to 0.2 m, 0.2 to 0.4 m, 0.4 to 0.6 m and 0.6 to 0.8 m. The Polynes ia Tall and Praia do Forte Brazil Tail cultivars performed better than the others in terms of both total root production and fine root densi ty, and they also reacted more effectively to water stress by better d eep root production. Excluding the other factors that influence water supply, these characteristics suggest that these materials are more su itable for planting zones subject to extended water deficits. As regar ds root system distribution throughout the soil profile, around 70% of roots were found within a 1-metre radius around the stem, at a depth of between 0.1 and 0.5 m, irrespective of the cultivar.