Determination of leaf nitrogen content using simple and effective methods

Abstract

Chlorophyll and Nitrogen are related to each other. Estimating one will help to predict the other. Many techniques are invented to estimate these two. In many cases evaluation of chlorophyll and nitrogen content in plants need to destructive methods, more time and organic solvents. Laboratory plant testing was usually time-consuming and high-costing. Hence, plant nutrient variability must be measured rapidly and the information made known to the farmers before the new season starts. The objectives of this paper was to evaluate the leaf chlorophyll content of different leaf colors in crop growth stage to determine leaf nitrogen content with non-destructive methods in crop leaves. SPAD-502 meter and CCM200 meter were two reliable measurements for total chlorophyll content and chlorophyll content index respectively. Different leaf colors of three field crops (maize, wheat & barley) and one perennial crop(coffee leaves) were selected to compare the performance of a handheld SPAD Chlorophyll meter and CCM-200 chlorophyll meter reading for total leaf chlorophyll and chlorophyll content index. Leaves were sampled and Chlorophyll was quantified using these two methods. Both techniques were compared against nitrogen content of leaf analyzed using standard laboratory procedures (Kjeldahl method).Mean comparison among the treatments (leaf colors) explained highly significant difference (p<0.001) with those two parameters (SPAD, CCM&N) at both growth stage. Significant correlations (r 2 =0.74, 0.88, 0.80&0.96 at vegetative and r 2 =0.93, 0.91, 0.54 &0.74 at flowering) were observed between total leaf chlorophyll (SPAD-502 reading) and chlorophyll content index (CCM-200reading) as well as (r 2 =0.96, 0.84, 0.99&0.99 at vegetative and r 2 =0.92, 0.86, 0.82&0.90 at flowering) for both reading with leaf N concentration (LNC) in all crops. From the result, the color of crop leaves was closely correlated with nitrogen (N) status and can be quantified easily with SPAD-502 meter and CCM-200 meter. The establishment of the relationship between SPAD-502 meter and CCM-200 meter reading and N status of leaf were important for crop monitoring and N diagnosis in the field at different crop growth stage.