The Effect of Planting Density and Supplementary Irrigation on the Agricultural Traits of Lentil (Lens culinaris Medik.) in Dry Conditions

IntroductionLentil (Lens culinaris Medik.) from the Fabaceae family, is a self-fertilizing and diploid annual plant (2n=14), herbaceous and botanically has a short and branched stem with a bright green color. Drought stress is one of the most common climate-related challenges in nature, and few plants can fully overcome it. It is a major factor limiting plant growth. Given that over 80% of the area under lentil cultivation in Iran relies on rainfed agriculture, drought has the greatest impact on reducing yield during various stages of the plant's growth and development. Supplementary irrigation technique is effective in reducing the possible risk and increasing the reliability of crop yield under rainfed conditions. Planting density can play an important and strategic role in plant yield. Materials and MethodsThe present experiment was conducted in the crop year 2023. The soil of the study site, first, was plowed and then disked and finally leveled with a trowel. Before planting, the seeds were disinfected using Captan fungicide to prevent lightning disease. After the initial preparation of the land, planting was done at the end of March 2023. The experiment was carried out in the form of split plots based on a randomized complete block design with three replications. The main factor (main plots) included two levels (irrigation at the time of planting and no supplementary irrigation) and the sub factor (subplots) was related to planting density (100, 200 and 300 plants per m2). All crop care was done at a certain time according to the customs of the research area. In this research, the characteristics of plant height, number of pods per plant, number of seeds per plant, number of branches per plant, dry weight of a whole plant (biomass), total weight of seeds of a plant (seed yield), 100-seed weight and the SPAD value were measured. Relevant measurements were performed with standard methods. SPSS version 26 software was used for statistical analysis of data. Results and DiscussionThe results of this study showed that there is significant genetic diversity for the studied traits. Based on the Analysis of variance results, in the case of supplementary irrigation factor, the traits of number of pods per plant, number of seeds per plant, biological yield, 100-seed weight and SPAD value at the probability level of 1% (P≤ 0.01) and for traits of plant height and seed yield were significant at the 5% probability level (P≤ 0.05). Regarding the planting density, traits of number of pods per plant, biological yield, seed yield, 100-seed weight and SPAD value were significant at 1% probability level (P≤ 0.01). Considering the interaction effect of these two factors (supplementary irrigation and planting density), the number of seeds per plant was significant at the 5% probability level (P≤ 0.05) and the 100-seed weight was significant at the probability level 1% (P≤ 0.01). Mojdeh cultivar with a density of 100 and 200 plants per m2 and with additional irrigation conditions at the beginning of flowering had the best yield (3.26 and 2.93 g, respectively). Correlation analysis (Pearson method) of traits showed that there is a significant correlation between the yield and other evaluated traits (P≤ 0.01 and P≤ 0.05), which indicates the relationship between yield components and yield which can pave the way for future agricultural and plant breeding research on the same topics as current research.  Conclusions According to the results of this experiment, it seems that the density of 100 or 200 plants per m2 is suitable for lentil cultivation in conditions similar to the location of this research. The results also showed the significant diversity and difference for most traits, which can be useful and practical in future agricultural and breeding programs.