Effects of planting date on growth indices and yield and yield components spring wheat cultivars in Neyshabur

Recognizing and evaluating the physiological parameters of crop growth, are important in the analysis of effective factors on yield and its components. With the help of these, the stages of plant growth can be evaluated and, with a brief description of growth and development, the product is evaluated (Soleymani Fard et al.,2011). The production and accumulation of dry matter can be studied through Crop Growth Rate (CGR) and Relative Growth Rate (RGR), which are two important physiological parameters (Ghiasabadi, et al., 2015). Environmental stress has a negative effect on leaf area expansion, via low leaf production rate, delayed planting, facing to extreme high and low temperatures, etc. (Karim and Siddique, 1991).Sarvada et al., (2014) reported a positive relationship between leaf area index and crop yield and biomass. They although described that physiological parameters such leaf area index and dry matter production, decreased by delayed planting. According to them, the reduction in crop yield is related to the decline in such parameters. The aim of this study was to determine the appropriate planting date for wheat and investigating the response of promising spring wheat cultivars, to climate changes in Neyshabour- Iran.
materials and ways: The experiment was carried out at Agricultural Research Station of Neyshabour during 2014-2015 growing season. A split plot experiment, based on randomized complete block design with three replications performed to investigate the effects of planting date on wheat physiological characteristics. The main plots belonged to three planting dates (October 11th, November 10th, December 10th), while subplots belonged to different spring wheat cultivars (Chamran, Pishtaz, Bahar, Sirvan, Sivand, Parsi). In order to estimating physiological characteristics, quadrat sampling was carried out with a 20×60 cm frame, at 6 growing stages: tillering, stem elongation, booting, heading, pollination and ripening. dry matter accumulation (DMA), leaf area index (LAI) and crop growth rate (CGR), were calculated using the following equations, based on growing degree day: DMA(g.m-2)=exp(a漟鳇) (1)
LAI=(a漟鳇) (2)
CGR(g.m-2.10GDD-1)=(b�)exp(a漟鳇) (3)
Yield of wheat estimated after harvesting 5.7 m2 of each plot. First rows of each plot leaved unharvest in order to minimize border effect. Random sample of plants was chosen from two middle rows (0.3 m2) to record yield components (spike per square meter, grain per spike, thousand grain weight). Harvest index calculated using yield and biomass data. Plants harvested with a combine harvester.
Results of analysis showed that planting date had a significant effect on plant height, Fertile tiller per square meter, Grain per spike, grain yield and average CGR. with delay in sowing date leaf area, crop growth rate ,dry matter accumulation decreased. effect of sowing date was significant on grain yield Results of mean comparison of sowing date on grain yield showed that date of 11 October with mean 6113( kg.ha-1) had the most grain yield. The sowing date of 10 December had the least grain yield with mean of 4124( kg.ha-1). (Table 3). Analysis of grain yield correlation with its components confirmed that spike number per square meter was most correlated with grain yield (table 5). This revealed that the reduction of spikes per square meter, was the main cause of grain yield reduction in delayed planting. There was a positive correlation between grain yield and average CGR (table 5).
In conclusion wheat plants produced more spike numbers per square meter during longer growing seasons, which resulted in higher grain yield at Neyshabour climate. Wheat common cultivars can be cultivated in October to achieve more grain yield.