Effect of Different Nitrogen Levels on Phenology, Growth Indices and Yield of two Lentil Cultivars under Rainfed Conditions in Mashhad

Introduction Lentil (Lens Culinarris Medik.) is an important pulse crop in Iran and is usually grown in rainfed areas. The average lentil yield in Iran is 1195 and 476 Kg.ha-1 in irrigated and rainfed farms, respectively. Low productivity occurs due to different factors. One of these factors is poor agronomic management practices that applied by the farmers, e.g. Limitation or inappropriate fertilizer distribution. Plant development occurs in a number of consecutive phases. These phases can be affected by temperature, moisture, photoperiod, cultivar and other factors. The amount of available nitrogen affects the distribution of assimilates between vegetative and reproductive organs and phenological stages of growth. Therefore, analysis of growth indices and its effective factors can be used as a suitable tool in evaluating the yield. The aim of this study was to evaluate the effect of different nitrogen levels on phenology and growth indices of two lentil cultivars in rainfed conditions of Mashhad.Materials and Methods The experiment was conducted as split plot layout based on randomized complete blocks design with three replications at the Agricultural Research Station, Ferdowsi University of Mashhad, during growth season 2016. Nitrogen fertilizer as urea (in three levels i.e. 0, 40 and 80 kg.ha-1) and cultivar (in two levels i.e. Birjand and Robat) were in main plots and sub plots, respectively. To determine the leaf area and dry matter, sampling was done every two weeks during the growing season. Phenological stages timing for each plot were determined based on 50% of emergence, 50% of flowering, 50% of maturity. Final yield was estimated from three square meter from each plot. Data were analyzed with the SAS software; the means were compared with Duncan's multiple range tests at the 5% level of probability. The graphs were prepared by SigmaPlot software.Results and Discussion The results showed that the effect of urea fertilizer was significant on vegetative, reproductive and overall plant growth based on days and growth degree-days. Also, 40 kg urea fertilizer per hectare showed that maximum of these traits. The effect of cultivar was significant on days and growth degree-days of planting to emergence, vegetative growth, reproductive growth and overall plant growth. Maximum of these traits were obtained in the Birjand cultivar. The difference in two lentil cultivars is related to genetic differences and their different adaptations to region. Urea fertilizer and cultivar interaction effects was not significant on phenological stages.Urea fertilizer had a significant effect on leaf area index, dry matter accumulation and yield. The highest leaf area index was obtained in treatment of 40 kg urea fertilizer per hectare. More production of leaf area affected on other growth indices and led to increasing of crop production. The highest grain and biological yield were achieved in this treatment. Cultivar effect was significant on maximum leaf area index, dry matter accumulation and yield. Birjand cultivar had maximum leaf area index, dry matter accumulation, crop growth rate, grain and biological yield. Since the most of growth indices are dependent on leaf area index, changes in this indicator through change in the nitrogen fertilizer levels, is one of the most important practices to improve yield. Correlation analysis showed that, grain yield had positive and significant correlations with vegetative growth, reproductive growth, overall plant growth, maximum leaf area index and dry matter accumulation.Conclusions In this study, using of 40 kg urea fertilizer per hectare had a greater effect on leaf area index in comparison to other nitrogen fertilizer levels. That leads to an increase in the dry mater accumulation, crop growth rate and eventually increased the seed yield. So, application of 40 kg urea fertilizer per hectare is advised to achieve maximum crop production. Birjand cultivar had a good situation in terms of all growth indices and produced the highest yield, but it is a late cultivar and requires the optimum planting date for cultivation in this region. According to the observed correlations, leaf area index and dry matter accumulation can be introduced as traits affecting the yield of the two lentil cultivars.