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.

International Symposium on Tropical and Subtropical Fruits

C. Sritontip, Y. Khaosumain, S. Changjeraja

biomass accumulation, lysimeter, SPAD value, ‘I Do’, chlorophyll fluorescence

https://doi.org/10.17660/ActaHortic.2014.1024.29