Reaction of Morphological Traits and Yield Components of Guar Plant (Cyamopsis tetragonoloba L.) in Different Planting Dates and Zinc Sulfate Levels in Khorramabad region

IntroductionGuar is a one-year plant from the Fabaceae family and tolerates dry and salty conditions, and therefore can be used as a high potential for production. The planting date is one of the most critical factors in the cultivation and production of crops. This is especially important for plants being introduced for cultivation in a region for the first time, as research on the optimal planting date for that area is essential. Mineral nutrition of agricultural plants is one of the most important aspects of production, and among the micronutrient elements, zinc has a fundamental role in the catalytic activities of proteins and enzymes involved in biological processes in growing plants. Facilitating the activity of many enzymes in the plant depends on the presence of appropriate amounts of zinc. Considering the research gap related to the effect of planting date and application of zinc sulfate in the study area and in order to compare with other different regions of the country, as well as the importance and development of new plant cultivation in the country, this research was carried out. Materials and MethodsTo investigate the response of morphological traits and yield components of guar plant (Cyamopsis tetragonoloba L.) on different planting dates and zinc sulfate levels in the KhorramAbad region in the 2020 crop year, was carried out. This experiment was carried out as a split plot in the form of a basic design of randomized complete blocks with three replications. In the main plots, the planting date factor was set at three levels (including May 1, 20, and June 10), and in the secondary plots, zinc sulfate foliar treatments were applied at four levels: zero, 20, 40, and 60 kg per hectare of zinc sulfate applied. The amount of zinc sulfate in each plot was mixed with soil based on the treatment levels and the area of each plot. According to the test results, the soil was not deficient in phosphorus and potassium elements, so only urea fertilizer was used. Results and Discussion The results showed that the effect of planting date, zinc sulfate, and their interaction on plant height traits, the number of sub-branches per plant, leaf dry weight, and specific leaf surface area were significant. Also, the effect of planting date and zinc sulfate on the number of pods per m2, grain yield, and leaf area index were significant. Planting guar on June 10 resulted in the highest number of pods per m2 (1998.6 pods) and the number of seeds per m2 (13920 seeds), and on the other hand, despite the positive correlation between them and seed yield, the highest seed yield on this date, 3889.7 kg per hectare was planted. The highest number of leaves per plant (846.75 leaves) and leaf area index (6.02) were obtained on the planting date of June 10 and with the application of 60 kg per hectare of zinc sulfate (689.44 leaves and 5.43, respectively). The highest amount of dry weight of leaves per plant in the treatment of application of 20 kg.ha-1 of zinc sulfate was 21.08 grams and the highest specific surface area of guar leaf was obtained on the planting date of May 20 and in the treatment of no application of zinc sulfate (0.47). The presence of a positive correlation between growth characteristics, yield components, and leaf characteristics with grain yield also indicated the positive effect of zinc sulfate application and planting date of 10 June in increasing these characteristics and as a result increasing grain yield. ConclusionsWith the delay in planting and the application of zinc sulfate fertilizer, which led to an increase in the grain yield components in the guar plant, the grain yield also increased. According to the results of this study, it can be said that to achieve the maximum seed yield in the guar plant in the Khorramabad region, this plant can be cultivated on the planting date of 10 Khordad. Also, considering that there was no significant difference in terms of grain yield among the different levels of zinc sulfate application, in order to achieve the highest grain yield with the lowest amount of cost, it is possible to use 20 kg of zinc sulfate per hectare.