Nitrogen is one of the most widely used nutrients for crop development. Application of Nitrogen fertilizers plays a crucial role in increasing agricultural yield and production. In order to achieve maximum crop yield and reduce the negative environmental effects, application of Nitrogen fertilizers should be based on the dynamics between Nitrogen supply and crop demand. In order to manage the consumption of Nitrogen fertilizers, it is necessary to accurately predict the crop Nitrogen requirements at different growth stages. In present study, the concept of critical Nitrogen concentration (Nc) has been used as an effective approach to determine Nitrogen status and estimate Nitrogen requirement of basil. For this purpose, basil was cultivated in the research greenhouse of the College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran. Different Nitrogen fertilizer treatments were applied at seven levels with three replications. Crop dry matter and Nitrogen concentrations were measured seven times during the growth period. Then Nitrogen Nutrition Index (NNI) and basil Nitrogen requirement (NR) were calculated for the first experiment. Results showed that, there was a significant regression relationship between basil NNI and NR (R2> 0. 96). Accordingly, the NR prediction model was developed using NNI values and day after planting (DAP). Then, accuracy and performance of the NR-NNI relationship were verified by the second experiment data. The values obtained for RMSE, NMB and NRMSE statistical indicators were less than 1 kg / ha, 0. 10% and 3. 10%, respectively, which indicates high accuracy of the model for prediction of crop Nitrogen requirement. In general, results showed that estimation of crop NR based on the concept of Nc could be used as a scientific and suitable approach for managing Nitrogen application in agricultural production.

In scale universal after drought, Nitrogen is the most important factor limiting. After Nitrogen, phosphorus is the most nutritious element for plant. Between Nitrogen and phosphorus is a positive reaction and absorption Nitrogen increases absorption phosphorus by plant. The Studies very few is performed in order to study fluorescence chlorophyll plant in nutritious shortage stress conditions. Reduction access to Nitrogen decreases quantum yield in transfer electron (photo system II) and its maximum efficiency. Also shortage of Nitrogen destroys photo system II and decreases fluorescence variable (Fv). Quantum yield increases consequently interaction effects Nitrogen and phosphorus. In view of the fact that measurement concentration Nitrogen with methods like measuring Nitrogen Nutrition Index (NNI) is very costly, take up time and need to expensive equipment, so measurement chlorophyll Index by hand chlorophyll meter and transportable is very comfortable. Also consumption of Nitrogen is improved pigments, as rate of chlorophyll (a, b) increases by using Nitrogen. this research in order to study relations between concentration Nitrogen, chlorophyll (a, b), chlorophyll Index and Nitrogen Nutrition Index (NNI) and study parameters fluorescence chlorophyll and rate of chlorophyll (a and b) under effect of different treatment fertilizer of Nitrogen and phosphorus in wheat was performed. Afield experiment was conducted in a factorial arrangement using randomized complete block design with 4 replications in Aliabadkatool city of Golestan province in 2014-2015 and 2015-2016 growing seasons. The experimental factors were three net Nitrogen fertilizer (N, 0, 163 and 326 kg ha-1 and five net phosphorus fertilizer (P, 0, 98, 196, 294 and392 kg ha-1. ) In this experiment some traits such as chlorophyll Index, Nitrogen Nutrition Index, fluorescence chlorophyll parameters, rate of chlorophyll (a, b), Nitrogen concentration, grain protein and grain yield were measured. The study of scattering diagram of data be showed, traits of chlorophyll Index, Nitrogen Nutrition Index, quantum yield, chlorophyll concentration (a, b), Nitrogen concentration in plan and yield protein follow from simple linear regression model, as in each level Nitrogen, with increase rate of fertilizer phosphorus, traits under study were prospered from increasing trend. Concentration of Nitrogen and Nitrogen Nutrition Index was under effect interaction year and Nitrogen. Fluorescence chlorophyll parameters including minimum fluorescence, maximum fluorescence (Fo, Fm) against other traits were showed decreasing trend, That connected to increase quantum yield consequently increase in consumed fertilizer. Correlation of significant and positive between chlorophyll Index, Nitrogen Nutrition Index, Nitrogen concentration, chlorophyll was observed. The maximum yield achieved at combination of fertilizer N326P392 and N326P294that point of view statically was in one of surface significantly. The results this experiment showed that very strong relation is between chlorophyll Index, chlorophyll concentration, Nitrogen Nutrition Index and Nitrogen available to plant, as with increase available Nitrogen and phosphorus rate, quantum yield and grain yield increased grain yield, so can be used from chlorophyll meter set for assessment fertilizer in plant replacing methods of expensive and take up tim like Nitrogen Nutrition Index. In management fertilizer in addition on Nitrogen, phosphorus must be considered too.

Nitrogen and phosphorus are the most important mineral elements needed by plants that are essential for growth and development of crops. In order to study yield, Nitrogen Nutrition Index (NNI), Chlorophyll Index and Nitrogen concentration of wheat in different regimes Nutrition, a factorial experiment based on a randomized complete blocks design with four replications was done at a research field in Golestan Province during growing seasons 2014-2015 and 2015-2016, The experimental factors were three net Nitrogen fertilizer rates of 0, 75 and 150 kg N ha-1 and five net phosphorus fertilizer rates of 0, 20, 40, 60 and 80 kg P ha-1 that in stage make ready of field, before from planting, tillering and stem elongation was divided, According to the results, traits under study in each three stage of planting, tillering and stem elongation had significant effect and follow from simple linear regression model, as in each level Nitrogen from different levels phosphorus, with increase rate of consumed phosphorus, traits under study were prospered from increasing trend and the maximum traits were recorded with 80 kg P ha-1 that yield was not showed significantly difference analysis with consumption of 60 kg P ha-1, Also The results this experiment showed that on the basis of results of table correlation between traits is very strong relation between Nitrogen Nutrition Index(NNI), chlorophyll Index and Nitrogen available to plant, so is offered with due attention to deficiency phosphorus fertilizer in field of Golestan Province, in management fertilizer in addition on Nitrogen, phosphorus must be considered, also is offered in order to reach to maximum yield is consumed a least 60 kg P net ha-1.

The Nitrogen (N) consumption management during the plant growth season plays an important role in achieving maximum crop yield and reducing environmental hazards. Determination of N Nutrition Index (NNI) is one of the methods for diagnosing plant N status. The main objective of this study was to investigate the role of monitoring NNI in improving Nitrogen consumption management. The field experiment was carried out during the growth period of summer maize in Pakdasht region, southeast of Tehran, in 2015 and 2016. Grain yield, dry matter and Nitrogen concentration of crop samples from seven treatments including: 0 (N0), 50 (N1), 100 (N2), 150 (N3), 200 (N4), 250 (N5) and 300 kg N. ha-1 (N6) were measured during the growing season. The results showed that NNI monitoring during the growing season could show the variation of N status in different treatments. In addition, NNI was closer to one in the optimal treatment (N4), which produced maximum dry matter with less N application, as compared with other treatments. Moreover, the relative grain yield decreased with a constant rate whenever the NNI was less than one. Agronomy and recycling efficiencies for the N4 treatment were higher than the ones in the other treatments. Water use efficiency of N4, N5 and N6 treatments in both cultivation years was almost equal and more than the ones of other treatments. These results indicated that the water and Nitrogen use efficiencies were higher in treatment with NNI closer to 1 (optimal treatment) as compared to other treatments.

Introduction Crop response to Nitrogen (N) is usually evaluated by N use efficiency and diminishing return curves between yield and applied N fertilizers. However, both methods are highly variable due to environmental conditions and are dependent to the amount, timing and type of N fertilizers. Extending the results of such studies will led to overestimation of crop N requirements as a result of differences in precipitation, temperature and radiation across locations and years. Therefore optimizing fertilizer use for maximum productivity should be based on methods with higher certainty. Nitrogen Nutrition Index i. e. the ratio of actual N concentration in plant tissues to the critical N concentration is more reliable measure for fertilizer recommendation because of its stability over environmental fluctuations. However, for development of N Nutrition Index the critical dilution cure should be specifically established for each crop. In this papers N Nutrition Index is estimated for different wheat cultivars and tested for evaluation of grain yield in response to N application rates. Materials and Methods To determine N Nutrition Index for wheat cultivars, a field experiment was conducted with factorial arrangement based on complete randomized block design with three replications. Experimental factors included three wheat cultivars (Chamran, Gaskogen and Sionez) and four N application rates (0, 55, 110 and 170 kg N ha-1). Shoot dry matter and N concentration was measured in five sampling during vegetative growth period. Using these data critical N concentrations and critical N dilution curves were calculated and compared with the previously established reference dilution curve for wheat crop. Nitrogen Nutrition Index (NNI) was then calculated as the ratio between measured shoot N (%) and the critical N concentration. Using NII grain yield and protein content of wheat cultivars was compared under different levels of N fertilizer. Results and Discussion Critical concentration of Nitrogen was slightly underestimated by the curve obtained in this study compared to reference curve. However, estimated coefficients of the dilution curve were closed to those of reference curve of wheat crop. Overall, Nitrogen deficiency, sufficiency and excess in shoot dry matter were properly described by the estimated critical dilution and critical uptake curves. All wheat cultivars were Nitrogen limited in no fertilized control and with application of 55 kg N ha-1 however, in 170 kg N ha-1 shoot Nitrogen content was more than amount required for optimal growth and in 110 kg N ha-1 Nitrogen uptake was closed to critical values. In unfertilized control and 55 kg N ha-1 NNI was lower than 1 during the whole vegetative growth period. However, in 110 kg N ha-1 NNI was almost 1 and in 170 kg N ha-1 varied between 1-1. 3. A significant relation was obtained between NNI at flowering and relative yield of wheat cultivars and grain yield of three cultivars reached to its maximum at NNI between 0. 9-1. Grain protein was also linearly correlated with NII at flowering. Conclusion Based on the results Nitrogen Nutrition Index calculated from critical dilution curve could be used as a powerful tool for precise estimation of crop growth rate, dry matter accumulation, grain yield and protein and to optimize the amount of N fertilizer required for any predefined yield level.

Improving Nitrogen utilization efficiency (NUtE) is one of the most important challenges in the agricultural sector. The NUtE Index, which is the amount of dry biomass (g) produced per Nitrogen absorbed (g) by the plant, is influenced by some factors such as climate and Nitrogen Nutrition status. Therefore, providing management strategies to increase NUtE should be performed by taking into account the Nitrogen status of the plant. In this study, relationships between Nitrogen Nutrition Index (NNI) and NUtE in lettuce were extracted based on the concept of critical Nitrogen concentration. For this purpose, two experiments were conducted in the research greenhouse of the College of Agriculture and Natural Resources, University of Tehran, located in Karaj, Iran, with six N fertilizer treatments. Then, NUtE and NNI were calculated for all treatments. The results showed that the NNI varied from 0.70 to 1.22 and 0.60 to 1.23 for the first and second experiments, respectively. The NUtE decreased due to the increase in fertilizer application rate. Also, application of Nitrogen fertilizer more than the plant uptake capacity led to a decrease in the Nitrogen uptake efficiency (NUpE). The relationship between NUtE and NNI for different dry biomass values was investigated. The results showed that at constant NNI values, NUtE increased non-linearly with increasing dry biomass production. Also, the critical Nitrogen utilization efficiency curve (NUtEc) discriminated well between different N treatments. Under the optimal Nitrogen Nutrition conditions (NNI = 1), the critical value of NUtE for lettuce was equal to 24 (g g-1 N).

There is no report on the Nitrogen Nutrition status of wheat fields using Nitrogen Nutrition Index (the ratio of the total actual N to critical N concentration at any time course of the crop growth period) method in Iran. Hence, this study was carried out to evaluate the N Nutrition status of 16 selected wheat fields in Gorgan during 2006-2007 growing season. Plant sampling were conducted in six growth stages during wheat growing season to determine dry matter yields, actual N concentration, critical N concentration and NNI. Soil samples were provided from 0 to 30 and 30 to 60 soil layers to determine some of physical and chemical characteristics, and NO3-N and NH4-N at the early season. Based on the obtained results, dry matter yields of fields were varied from 0.38 ton ha- at the beginning tillering to 12.51 ton ha- at the harvesting maturity. The mean of N concentrations (%) in plant dry matter were 3.09 at beginning tillering, 2.60 at complete tillering, 1.62 at stem elongation, 1.56 at boot stage, 1.14 at the beginning watery ripe stage and 1.08 at harvesting maturity. These results indicate that the most reduction in N concentration occurred in stem elongation stage, and that N concentration in plant dry matter decreased as plants developed. Actual N concentrations in dry matter were substantially less than critical N concentrations at all development stages; The means of critical N concentrations at above mentioned development stages were 4.38, 4.33, 2.88, 2.32, 1.95 and 1.72, respectively. Then, the means NNI for 16 wheat fields were very lower than optimum (NNI=1) at all development stages; 0.71 at beginning tillering, 0.59 at complete tillering, 0.57 at stem elongation, 0.68 at boot stage, 0.59 at the beginning watery ripe stage and 0.61 at harvesting maturity. Based on these findings, N Nutrition status in studied wheat fields was unsuitable through growing season, and that N can be considered as one of the limiting factors for wheat growth and yield in these fields. Finally, the obtained results indicated that achieving potential yield of this region using current N management is impossible.

In order to determine the Nitrogen requirement of rice (cv. Guilaneh) using the Nitrogen Nutrition Index and chlorophyll meter, an experiment was conducted as a randomized complete block design with three replications in the research field of the Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran in 2016. Experimental treatments consisted of six Nitrogen fertilizer levels (0, 60, 120, 180, 240, and 300 kg N. ha-1; Urea source). Evaluation of the relationship between Nitrogen Nutrition Index and chlorophyll-meter readings at three stages of plant growth (maximum tillering, booting, and heading) to predict grain yield in response to Nitrogen fertilizer showed that the equation of the critical Nitrogen concentration in Guilaneh was Nc = 3.99W -0.36. The correlation between chlorophyll-meter readings and Nitrogen Nutrition Index was positive and significant at each plant growth stage. The results showed that the mature lower leaves were more sensitive than the younger higher leaves in response to Nitrogen fertilizer and were more suitable for detecting plant Nitrogen status, especially during the booting and heading stages. The highest correlation was found between the Nitrogen Nutrition Index and chlorophyll-meter (r=0.95*) and relative chlorophyll-meter (the ratio of chlorophyll-meter readings in each treatment to Nitrogen saturated treatment) (r=0.96**) in the third leaf and booting stage. The overall results of this experiment showed that the Nitrogen Nutrition Index and chlorophyll meter may consider reliable indicators for evaluating the Nitrogen status of rice (cv. Guilaneh) during the growing season.

Monitoring Nitrogen Nutrition Index (NNI) during the growing season requires costly experiments and is a time-consuming process. Recently, some remarkable studies have been carried out in order to determine NNI by employing different plant parameters which can improve fertilizer and water use efficiency and reduce environmental hazards. The main objective of this study was to estimate the NNI during the growing season of maize by using a non-destructive method. Dry matter (W) and actual Nitrogen uptake (Nu), the required parameters for predicting NNI, were estimated by AquaCrop and HYDRUS-2D models, respectively. The critical Nitrogen curve, proposed by Ranjbar et al. for summer maize in Iran, was used in this study. Plant and soil samples were taken for calibration and validation of the two models during the two growing seasons. The results showed that AquaCrop can accurately predict maize dry matter production during the growth period (R2 =0. 995, NRMSE= 14. 21 %). Moreover, the accuracy of the estimation of Nitrogen uptake by the HYDRUS-2D was relatively acceptable (R2 >0. 907, NRMSE< 28. 20 %). Finally, NNI was calculated using measured (NNIo) and simulated (NNIp) data over the two seasons. Comparing the NNIp versus the NNIo revealed that accuracy of the estimated values was acceptable based on the R2 and NRMSE criteria (>0. 638 and <20. 86, respectively) in both years.

Background and Objective: The goals of study were to evaluate the combined effects of tillage practices, corn residues, and Nitrogen (N) rates for improving Nitrogen use efficiency (NUE) and protecting yield performance of wheat in arid and semi-arid regions of southern Iran. Materials and Methods: The experiment was conducted as split split-plot based on randomized complete blocks design with three replications in the Zarghan Field Station, Agriculture and Natural Resources Research and Education Center of Fars Province during two cropping seasons (2015-17). The experimental treatments included tillage practices (Conventional tillage, CT; Reduced tillage, RT; No Tillage, NT) as main plots, with and without corn residue (at 30% residue retained and removed) as sub plots, and pure N rates (0, 101, 152, and 202 kg N ha-1 from Urea source) as sub sub-plots. Results: After 2 years, wheat yields (5266 kg. ha-1) were tended to be increased with increasing N rates from 101 to 202 kg N ha-1 under RT with corn residue retention. Likewise, the increasing N rate at 202 kg. ha-1 can be increased apparent recovery efficiency of N (AREN) and Nitrogen uptake efficiency (NUpE) under the reduction of soil tillage operations when crop residue retained. In the contrast, the highest physiological and agronomic efficiency of N (PEN and AEN, respectively) (58. 18 and 19. 31 kg. kg-1, respectively) were obtained by CT and RT methods with 101 and 152 kg N ha-1, respectively. Nitrogen Nutrition Index values <1, around 1, >1 were recorded at <152, 152, >152 kg ha-1 of N applied, respectively. Conclusion: Our research has shown that replacing RT with CT and/or NT with corn residue retention and 152 kg N ha-1 can greatly increase NUE especially AEN and PEN, improve NNI, and protect wheat grain yield under wheat-and corn in a rotation.