The effect of drought stress on nitrogen and SPAD reading of wheat (cv Falat) was studied in a complete randomized block design with 3 replications; in the green house. Five levels of drought stress (-0.3, -1, -3, -5 and -7 b) were used as treatments. Soil water curves were plotted using presser plate at a wide range of soil water potential. Water requirement for each treatment determined with weighing by day of each treatment. SPAD reading, nitrogen content, stomatal resistance and specific leaf weight (SLW) of flag leaf and two leaves under flag leaf were measured at anthesis stage. Results showed that with increasing drought stress SPAD reading, nitrogen content, stomatal resistance and SLW increased and there was a high relationship between drought stress and SPAD reading. It was concluded that SPAD reading is a good index of nonstomatal resistance for preduction water stress severity.

In order to use chlorophyll meter (SPAD) to recognize nitrogen deficiency in sugar beet plants and used to predict the appropriate timing for fertilizer top-dressing in sugar beet a research was conducted using various levels of nitrogen fertilizer during different growth stages of sugar beet plants in the research farm of Sugar Beet Seed Institute located in Karaj during 2007, using a split plot design in time based on Randomized Complete Blocks in four replications. Five level of pre-sowing nitrogen from the source of urea was applied in amounts of 0(as control), 120, 160, 200 and 240 kg/h considered as main plots and plant growth stages as sub plots. Chlorophyll concentration in 5th leaf blade was measured by chlorophyll meter (SPAD) at five growth stages based on the number of leaves on sugar beet plants including (GS1:3-6, GS2: 6-12, GS3:12-15, GS4:15-18, GS5:18-20) leaves of each plot. In the same leaves, concentrations of nitrogen (by Kjeldahl method) and chlorophyll a, b and a+b (by Spectrophotometer) were measured. Results from regression analysis on the leaf number 5 showed that there was higest significant correlation between chlorophyll reading and nitrogen on a leaf area basis and on a dry-weight basis, and total nitrogen and concentration of chlorophyll (a, ab) in 12-15 leave stage. Also results of this experiment showed that the chlorophyll meter reading were influenced by the growth stage and sampling time and the level of used nitrogen fertilizer. Nitrogen fertilizer and different growth stage had significant effect on the chlorophyll meter reading. The least number read from SPAD was 34 in 3-6 leaf stage, which associated with no-applied nitrogen treatment. Threshhold of chlorophyll meter was estimated 39/1 in this study in 12-15 leave stage, this threshold can be used as a criteria to compare. According to the obtained results, chlorophyll meter can be used as a simple, rapid and non-destructive instrument to determin chlorophyll concentrations in a leaf during 12-15 leaf stage and to recognize nitrogen deficiency in sugar beet plants and can be used to predict the appropriate timing for fertilizer top-dressing after of calibiration for region in sugar beet.

Since the plant reflects the total N-supply from all sources, plant N status can be a good indicator of N availability to crops at any given time. The chlorophyll meter (SPAD) and leaf colour chart (LCC) are simple, portable diagnostic tools that can measure the crop N status in situ in rice fields to determine the timing of N top dressing. To study optimal N-management an experiment was carried out in Rice Research Institute in mazandaran, in 2009. A test material has been evaluated in a Randomized Complete Block Design with three replications. Shirudi variety was grown under eight treatments, including zero-N control, two splits, chlorophyll meter 35, 37, 40, LCC 4 and 5. Both LCC and SPAD can be used to improve N management for rice. The optimal SPAD threshold used to determine the timing of N-application was 37 LCC treatment indicated that N-management based on LCC shade 5 helped to avoid over application of N. It is suggested that when N-management technology such as real time N-management (SPAD and LCC) were used, it would be possible to avoid the over application of N fertilizer by rice farmers.

Introduction: Nitrogen is the most important limiting factor, after water deficit for biomass production in natural ecosystems. Efficient use of nitrogen fertilizer is important to economical dryland wheat production and to the quality of ground and surface waters. Researchers have been looking for ways to increase the efficiency of N fertilizer use. Soil and in-season plant tissue testing for nitrogen status are a time consuming and expensive process. Chlorophyll concentration in a leaf is closely correlated with leaf N concentration so the Soil Plant Analysis Development (SPAD) chlorophyll meter is one of the most commonly used diagnostic tools to measure crop nitrogen status. The SPAD chlorophyll meter is a simple, portable, diagnostic and nondestructive light weight device used to estimate leaf chlorophyll content. Chlorophyll meter techniques provide a substantial saving in time and resources and offer a new strategy for synchronizing nitrogen application with actual crop demand. The objective of this study was to establish and analyze the relationships between measurements from a SPAD instrument and the leaf pigments, as extracted at different stages. The study also seeks to evaluate the utility of a chlorophyll meter to inform nitrogen fertilization rates of wheat (Triticum aestivum L. ) genotypes in dryland condition. Materials and Methods: This experiment was carried out in split split plot based on RCBD design with three replications. Treatment included: N application time (whole fertilization of N in fall, and its split fertilization as 2/3 in fall and 1/3 in spring), N rates (0, 30, 60 and 90 kg N ha-1) as urea and 7 genotypes (Azar2, Rasad, Ohadi, HN7/OROFEN//BGN8/3/SERI/4/. ., SARA-BW-F6-06-85-86-29-1, TEVEE'S'//CROW/VEE'S' and DH-2049-3. A chlorophyll meter (SPAD-Hansatech Cl-01) was used to read leaf chlorophyll content (SPAD value) at tillering (GS22), shooting (29), stem elongation (GS32), flag leaf (GS39) and anthesis stages. Fresh plant leaf samples were collected from each plot for the estimation of chlorophyll a (Chla), chlorophyll b (Chlb), carotenoids (Ct), total chlorophyll (Chlt) and concentrations. The chlorophylls and carotenoids were determined by spectrophotometric analysis of chemically extracted pigments. To examine the relationship between pigments chlorophyll and SPAD values, 30 wheat leaves were sampled. Average Chla, Chlb, Chlt, carotenoids and SPAD values were computed, and linear regression analysis was performed by least-squares method with Excel. Results and Discussion: The results showed a strong positive and statistically significant (p<0. 01) relationship between SPAD values and total chlorophyll (R2 = 0. 93), chlorophyll a (R2 = 0. 95), chlorophyll b (R2 = 0. 78) and carotenoids content (R2 = 0. 79). We demonstrated that the SPAD readings and plant photosynthetic pigment content per-leaf are profoundly affected by nitrogen rate and timing of application. Nitrogen split application increased significantly (p<0. 01) the SPAD values (8. 3%), Chla (11. 1%), Chlb (10. 9%), Chlc (27%), Chlt (15%), (exception of carotenoids) and seed protein content (8. 5%). Nitrogen application could affect significantly (p <0. 01) all chlorophyll indices in plant. The ideal conditions for the chlorophyll indices in the plant were obtained using 72 kg N ha-1. Nitrogen requirement for maximum and optimum economical dryland wheat production is about 20 and 10 kg ha-1 less than nitrogen requirement for creation the ideal conditions for chlorophyll status and its components in dryland wheat. Using chlorophyll meter, chlorophyll a (16. 6 mg g-1), chlorophyll b (5. 9 mg g-1), chlorophyll c (0. 077 mg g-1), total chlorophyll (23. 9 mg g-1) and chlorophyll a per Chlorophyll b ratio (2. 78), chlorophyll index (9. 4) and chlorophyll relative index (1. 0) were determined in economical optimum N rate (NRD = 0). Genotype1 was most suitable and Azar2 was the most inappropriate condition in terms of chlorophyll index and total chlorophyll ratio per carotenoids (optimum range 40-70) in the plant as a stress resistance index. Conclusions: It can be concluded that, the actual chlorophyll content and its components can be estimated using chlorophyll meter (SPAD) in dryland wheat genotypes at different growth stages. Chlorophyll components and seed protein can be improved by nitrogen fertilizer application time and rates in dryland wheat.

In order to determine relationship of leaf chlorophyll concentration and yield and quality using chlorophyll meter in sugar beet research was conducted using various levels of nitrogen fertilizer during different growth stages of sugar beet plants on research farm of Sugar beet Institute located in Karaj Kamal- Abad during 2007, design based on Randomized Complete Blocks in four replications. Five level pre-sowing nitrogen from the source of urea was applied in amounts of 0 (as control), 120, 160, 200 and 240 kg/h. Chlorophyll concentration leaf blade number 5 was measured by chlorophyll meter (SPAD) at 12-15 leaf stage. In the same leaves, concentrations of nitrogen (by Kjeldahl method) was measured. The results showed that moreover 50% of the variability in yield is explained by the SPAD reading in the growth stages 12-15 leaf in sugar beet. SPAD value was, also related whit N concentration and a- amino N in root. The highest SPAD reading showed maximum a- amino N in root. Nitrogen fertilizer had significant effect on the chlorophyll meter reading. The least number read from SPAD was 38, which associated with no-applied nitrogen treatment. Highest yield of root (ton / hac) in this experiment was related to with N160, which the number read from the chlorophyll meter in levele was equal with 41.2. According to the obtained results, therefore, whit further research chlorophyll meter (SPAD) can be used as a simple rapid and non- destructive and may be useful to predict yield and may be a useful tool determine which field to harvest late in season.

In order to estimate the leaf nitrogen (N) status of rice plant (oryza sativa L Cv. Khazar) and to recommend the precise timing of N-fertilizer topdressing by using chlorophyll meter (SPAD-502), a field experiment was carried out in a RCBD with 6 treatments and three replications in a coastal light texture soil in Guilan province -Iran in 2003 cropping season. Six N rates using Urea T1-control (no N fertilizer), T2-40 kg/ha (Basal), T3-40+40 kg/ha (Basal + Mid-tillering), T4-40+20+20 kg/ha (Basal + Midtillering + Panicle initiation), T5- 60+60 kg/ha (Basal + Midtillering) and T6-60+30+30 kg/ha (Basal + Midtillering + Panicle initiation) Kg/ha were applied. The chlorophyll meter (SPAD) values and leaf N concentration (by Kjeldahl procedure) were determined at 9 stage: 19, 29, 39, 49, 59, 69, 79, 89 and 99 days after transplanting on the uppermost fully expanded leaf in rice plant. Regression analysis showed that, when data for all growth stages were pooled, SPAD values predicated only about 23% of variation of leaf N concentration on a dry-weight basis, but SPAD values predicated about 80% of variation of leaf N concentration on a leaf area basis. At each growth stage, SPAD values correlated with leaf N concentration on a leaf area basis better than leaf N concentration on a dry-weight basis.Thus, chlorophyll meter provides a simple, quick, and nondestructive method to estimate the leaf N concentration on a leaf area basis and can be used to predict the appropriate timing for N fertilizer topdressing in rice.