EARLY PLANTING AND SUPPLEMENTAL IRRIGATIO N, ON CASSAVA GROWTH AND YIELD

A field study was carried out in Paraipaba, Ceara, Brazil, with the ob jectives of studying the viability of increasing the length of the gro wing season of cassava in a single agriculture year, by using irrigati on combined with early planting. The crop was grown in different cycle s, as a result of the combination of four times of planting (December, January, February and March) with four times of harvesting (June, Aug ust, October and December). Cultivars Jaburu and EAB 652 showed signif icant increases in top and root yields when the planting was anticipat ed from February to December. When performed at the beginning of the g rowing cycle, the irrigation was more effective than when applied at t he end, when the raining season had ceased. The water restriction that took place when rains ceased in the second half of the year appeared to be the main factor responsible for the decrease in the dry matter p resent in the leaves. The higher tuber yield observed in cv. Jaburu, w as associated with its higher harvest index. Cassava yield appeared to be more related to the increase in the root diameter than to the coot number or root length. The last two parameters were stabilized 90 day s after planting. A direct relationship between cassava yield and the length of the planting growing cycle was found.