DIFFERENT NITROGEN CONCENTRATIONS AFFECTING CHLOROPHYLL AND DRY MATTER DISTRIBUTION IN SAND-CULTURED LONGAN TREES
The effects of nitrogen concentrations on dry matter accumulation of longan were studied on four-year-old grafted trees, I Do. The trees were grown from January to December 2006 in a lysimeter filled with fine sand. A CRD was used in an experimental design with five treatments, namely 0, 2, 4, 8 and 16 mM L-1 of nitrogen (N), in a nutrient solution. The results showed that increased nitrogen raised the SPAD value, chlorophyll a, chlorophyll b and chlorophyll fluorescence in the leaf. At the lower nitrogen concentrations these values were also the lowest. The 8 mM N L-1 concentration gave higher dry weight of fruit, twig, leaf, larger branch, stem, smaller roots while produced larger roots than 2, 4 and 16 mMN L-1. With 0 mMN L-1 these dry weights were the lowest. All treatments differed little in smaller branch production. Increasing nitrogen from 2 to 8 mMN L-1 raised the total dry matter, while the 16 mMN L-1 treatment lowered the total dry matter. N and Mg increased while P and Ca decreased leaf production. Therefore, care must be taken in not over fertilizing, because at higher than 8 mMN L-1 concentrations, the beneficial effects become a detriment to fruit production.
Sritontip, C., Khaosumain, Y. and Changjeraja, S. (2014). DIFFERENT NITROGEN CONCENTRATIONS AFFECTING CHLOROPHYLL AND DRY MATTER DISTRIBUTION IN SAND-CULTURED LONGAN TREES. Acta Hortic. 1024, 227-233
biomass accumulation, lysimeter, SPAD value, 'I Do', chlorophyll fluorescence