Comparison of two methods for the determination of nitrogen in leaf and yield in banana, jujube and rubber tree

Nitrogen is an essential element for plant growth and development. Generally, the standard technique of nitrogen analysis is done by the Kjeldahl method. However, this method is a long and time-consuming procedure. A faster, alternative technique for nitrogen analysis is colorimetry. The objective of this work was to evaluate the potential of colorimetry for nitrogen analysis. The investigation was conducted using three plants species, banana (Musa sp.), jujube (Zizyphus mauritiana Lam.) and rubber tree (Hevea brasiliensis). In each plant, the nitrogen contents in both leaf and yield were analyzed. The comparisons of two methods were analyzed using a t-test, analysis of variance and liner regression analysis. The results demonstrated a highly positive correlation between the Kjeldahl method and the colorimetry technique (r²=0.88, pKLEINERDAN0.01). This identified colorimetry as a prospective technique for the measurement of nitrogen analysis in plant tissue. Also, the nitrogen concentrations in the leaves of all plants were higher than those nitrogen concentrations in their respective products. The nitrogen concentrations in leaves analyzed by colorimetry were 1.47% for the banana, 2.30% for jujube and 2.01% for rubber tree plants while the nitrogen in yields was 0.35% for banana pulp, 1.07% for jujube pulp and 0.62% for dry latex.