Nitrogen and Chlorophyll Correlation Index in Marandu Palisadegrass Leaf Fertilized with Nitrogen Sources.

Chlorophyll index of leaf calculated by the equipments is usually highly correlated with leaf chlorophyll content and may identify nitrogen (N) deficiency without need for the determination of N in plant tissue. The objective of this experiment was to evaluate N concentrations, chlorophyll index of leaf and correlation of these parameters in Marandu palisadegrass (Brachiaria brizantha cv. Marandu) in response to sources of N (urea, urea with urease inhibitor, polymer coated urea, ammonium sulfate, ammonium nitrate, ammonium sulphonitrate and without N) in seven harvests (11/24/2012, 12/27/2012, 01/24/2013, 03/08/2013, 04/05/2013, 05/23/2013 and 07/03/2013), in Ilha Solteira, SP, Brazil (20^o 21^' S, 51^o 22^' W and 226 m).  The determination of N and the reading of the leaf chlorophyll were made in diagnostic leaves in Marandu Palisadegrass. The experimental design was a randomized complete block with four replications. Nitrogen concentration in diagnostic leaves was influenced by N sources for the first, fourth, fifth, sixth and seventh harvest. Sources of N did not influence chlorophyll index of leaf in all harvests, with the exception of the fifth and seventh harvest, but were lower in the control (absence of N). Pearson's correlation for the index chlorophyll of leaf and N concentrations in diagnostic leaves was positively significant. Index chlorophyll of leaf can be used to N fertilization recommendation. As the effect of N sources varied among harvests for N concentration and the leaf chlorophyll index in diagnostics leaves, the option is the use of urea, because it is lower cost and higher N concentration.