| چکیده انگلیسی مقاله |
Introduction
According to its genetic, botanical, physiological characteristics, weather conditions, soil and growth environment each wheat cultivar can produce the highest grain yield in a certain condition of plant density (Elhani et al., 2007). The highest grain yield is achieved when the competition amoung the plants are at its minimum and the plant can make maximum use of the environmental factors (Bastos et al., 2020). Therefore, it seems necessary to determine the most appropriate density of each promised line and variety in order to achieve the higest grain yield potential before distribution and planting by farmers.
Materials and Methods
In order to investigate the effect of seed rate on yield and yield components of new cultivars and promising lines of bread wheat, an experiment was carried out in two cropping seasons (2020-2022) at Gonbad agricultural research station. The experiment was carried out as a factorial with two factors of density and cultivar in the randomized complete block design (RCBD) in four replications. Plant density in six levels including 200, 250, 300, 350, 400 and 450 seeds per m2 and genotype in six levels including N-93-9 line and Araz, Arman, Tektaz, Kalateh and Tirgan cultivars were two factors of this experiment. During the growth seasons, agricultural technical recommendations were applied equally for all treatment. Traits were recorded during the vegetative and reproductive growth season. After harvesting, weighing and measuring the desired traits and ensuring the uniformity of the error variances in the experiments, combined variance analysis was performed for two years. Then, the mean of the treatments based on Duncan's test at a statistical level of 5% was compared.
Results and Discussion
According to the results of this study, the simple effect of density was significant at statistical level of 1% for all investigated traits. That is, the characteristics of grain yield, biomass yield, thousand kernel weight, plant height, and number of grains per spike, number of spikes per square meter, peduncle length, days to heading and days to physiological maturity were different in various densities. The results of comparising means showed that the highest and lowest values for the traits of grain yield, biomass yield and the number of spikes per square meter were obtained at densities of 350 and 200 seeds per square meter, respectively.The highest grain yield and biomass yield at density of 350 seeds per square meter were obtained with 5388 and 14017 kg ha-1, respectively. Then the density of 400 seeds per square meter was ranked second with 5189 and 13732 kg ha-1 for seed yield and biomass yield. The interaction effect of year and density was significant in trait of grain yield, but in each year, the highest grain yield was obtained at density of 350 seeds per square meter. Kalateh, Arman and Taktaz cultivars had the highest grain yield with 5087, 5085 and 5068 kg ha-1, respectively, also Arman cultivar had the highest number of spikes with 473 spikes per square meter, and Araz cultivar had the highest thousand kernel weight with 41.9 gram. The highest number of spikes i.e. 503 spikes per square meter, was obtained at density of 350 seeds per square meter, and the lowest number of spikes per square meter was obtained at density of 200 seeds per square meter with 437 spikes per square meter. These findings show that the density of 350 seeds per square meter is the optimal density to maximize wheat yield. In fact, at this density, plants can fully use the available resources without experiencing negative effects (Lollato et al., 2024).
Conclusion
In general conclusion of this study, the maximum values for the traits of grain yield, biomass yield and number of spikes per square meter was obtained at density of 350 seeds per square meter. Although the interaction effect of year and density was significant in grain yield, the highest grain yield was obtained at density of 350 seed per square meter (51480 kg ha-1 in the first year and 5804 kg ha-1 in the second year). The highest grain yield with 5087, 5085 and 5068 kg ha-1 was related to Kalateh, Arman and Taktaz cultivars, which was significantly higher than Araz and Tirgan cultivars. |