YIELD AND QUALITY OF KENAF (HIBISCUS-CANNABINUS L) STEM AS AFFECTED BY HARVEST DATE AND IRRIGATION

In view of the potential for kenaf as a viable paper-pulp crop for Ita lian areas, a field trial was conducted in 1992 in Cadriano (latitude 44 degrees 3'N, longitude 11 degrees 2'E) to estimate quantitative and qualitative crop performance as influenced by harvest date (114, 129 and 152 days after emergence, DAE) and irrigation. The productivity of two mid-late cultivars (BG 52-38-2 and Everglade 41) was positively a ffected by the length of the growing season and by the restoration of 100% of the crop evapotranspiration (ETc). Total dry yield of the rain fed crop was 10 t ha(-1) at early harvest (mid-September) and reached a 13 t ha(-1) plateau at late harvest (late October). Under well water ed conditions crop biomass was 50% higher and it increased linearly wi th time, reaching a value of 20 t ha(-1). The stem yield accounted for from 74 to 89% of the total biomass, and mean stem growth rates of 18 and 11 g m(-2) d(-1) were recorded for irrigated and non-irrigated cr ops, respectively. The bark content of the stem varied in relation to crop age and genotype and increased with time only in Everglade 41. Ce llulose content in the bark was affected by harvest date, ranging from 54 to 56% at early and mid harvest to 61.6% at the latest harvest, an d by irrigation, which favoured a similar increase. Positive relations hips (r between 0.64 and 0.74) were found between growth traits (total and stem dry yield, stem height and basal stem diameter) and cellulos e accumulated in the bark.