Study Of Relationship Between N Concentration And Chlorophyll Content On Tarom And Nemat Rice Cultivars

Two field experiments were carried out to study of elationship between N concentration and chlorophyll content on Tarom and Nemat cultivars. The experiments were conducted in 2001 and 2002. Trails were located in two different fields of the Rice Research Institute farm (Mazandaran province). A randomized complete block design with three replicates with five treatments on Tarom ,(0, 23, 46, 69, 92 Kg N per ha) and seven treatments on Nemat with different N rates of Urea-N input,(0, 23, 46, 69, 92,115 and 138 Kg N per ha), was selected. Plot size was 12 m2 per treatment and seedlings were transplanted at 25 × 25cm spacing. Phosphorus and potassium were uniformly applied to all plots at last puddling. Other cultural practices such as water management and crop protection were the same as those of local farmers. The performance of different N rate applications was measured in terms of grain yield at 14% moisture content. SPAD readings were taken at critical growth stages (i. e. early tillering, panicle initiation and first flowering). A chlorophyll meter was used to take measurements the youngest fully expanded leaf of 10 randomly selected plants from each plot. 10 leaves from each plot were sampled and leaf N concentration was determined by standard microkjeldahl digestion and distillation. The results were evaluated in terms of correlation between SPAD values and leaf N concentration on a dry-weight basis (Ndw). The results showed that linear relationship between leaf N concentration on a dryweight basis (Ndw) and the SPAD values differed depending on development stages and genotype. there was correlation between SPAD values and weight-based leaf N concentration at each stage but this correlation differed significantly between growth stages and/ or variety. Correlation between Ndw and SPAD values were gratest at panicle initiation and first flowering and weaker at early growth stage in two variety. The results suggest that we can use chlorophyll meter to predict time of N application in rice. The effect of year was significant on the correlation, indicating invironment factors such as radiation diffrences between seasons affect SPAD values.