Effect of different ethephon doses on grain yield and yield components of in barley (Hordeum vulgare L.)

This study was carried out under supplementary irrigated conditions in the Harran Plain in 20082009 and 2009-2010 growing seasons. The study aimed to assess the effects of various ethephon doses on durum wheat and barley cultivars. Nine ethephon dosages (0, 240 g/ha, 360 g/ha, 480 g/ha, 600 g/ha, 720 g/ha, 840 g/ha, 960 g/ha, 1080 g/ha) were applied in the study. The results of the combined analysis of two years indicated that the highest grain yield was recorded for Sur-93 cultivar with 4365.63 kg/ha in 600 g/ha ethephon application, while the lowest grain yield of barley was obtained from land race black barley with 1978.00 kg/ha (in control application). The result revealed that ethephon had positive effect on to grain yield. There was not any statistical significants between 960 g/ha and 1080 g/ha ethephone doses in terms of grain yields for land race black barley cultivar. When the years and barley cultivars is evaluated together, the highest grain yield is obtained with 960 g/ha dose of ethephon. Results showed that ethephon application to barley shortened plant height and increased 37-46% of barley yield, and the effects of ethephone varied were connected to cultivar specific. In addition Sur93 600 g/ha, and a land race black barley cultivar 960 g/ha could be recommended.


Introduction
Barley, based on the production area (26.1 million ha) and total yield (7.4 mil. ton), is the second important cereal following wheat in Turkey. In southeast of Turkey, barley has been produced on 372,030.5 ha and total produced grain yield was 556,876 ton (Anonim 2020). Compared to wheat, early maturation of barley allows cultivation of a second crop within the same season which is very important in irrigated areas such as Harran Plain. Barley as a winter cereal is widely planted in southeast of Turkey. However, barley is very sensitive to lodging and even under normal precipitation and fertilization conditions lodging is widely observed and it causes significant yield reduction. Therefore, lodging prevention would make significant contribution to the region and the state economy.
Lodging causes yield reduction by reducing plant growth, reduced photosynthesis and prevented carbohydrate assimilation. Severe lodging generally occurs prior spiking stage which causes 27-40% yield reduction while lodging during kernel maturation causes 20% yield reduction (Rademacher 2009). Lodging is major risk and issue for intensive cereals production and it causes reduced yield and low quality cereals.
Plant growth regulators (PGR) have been applied to cereals from sowing to harvest to increase yield and quality of cereals in Turkey and around the world (Karakus and Koker 2007;Rademacher 2009), reported that some of the PGR reduce plant height, stabilize shoot, auricle and other plant parts growth and increase resistance against lodging by improving plant root development. Ethephon has been reported as one of the PGR that reduces cereals lodging.
In this study, we intended to determine the effect of ethephon on loading reduction of barley cultivars Sur-93 and a local barley cultivars.

Materials and Methods
The study was conducted in Şanlıurfa -Harran plain during 2008-2009 and 2009-2010 growing seasons. Climate data about the growing seasons of the study was conducted has been given in Table 1. In this study, Sur 93 and a local barley cultivar were used as plant materials. Both barley cultivars, during high precipitation and under irrigated conditions, have been shown to be highly susceptible to lodging. The study was carried out as split plot experimental design with four replications. Main plots were barley cultivars while Ethephon [(2-chloroethyl) phosphoric acid] dosages were the subplots. Applied ethephon dosages were 0, 240, 360, 480, 600, 720, 840, 960 and 1080 g/ha.
Ethephon was applied to foliar with a backpack sprayer according to Feekes' scale at 8-9 stages during flag leaf development (Akkaya 1994). Untreated (control) plants were treated with water only. Screens were placed in between plots to prevent drift of the applications. Each plot was 5 m long and covered 6 rows of the crops. There was 20 cm spacing between the rows. Planting density was 600 seeds / m 2 and seeds were sown with a seeder. The seeds were sown during [2008][2009][2009][2010] growing seasons within month of October. All plots were irrigated with sprinklers until soil water holding capacity is reached.
During irrigations water runoff was not allowed. The plots were re-irrigated when 40% of the soil moisture was used up to restore the soil moisture (Rawlins, 1976). During sowing 15-15-15 compound fertilizer was applied based on 80 kg NPK / ha. Based on soil analysis, P and K fertilizers were applied at 80 kg/ha rate during planting while N fertilizer was applied at 180 kg/ha throughout of the vegetative growth. Half of the N fertilizer was applied during planting while the other half was applied during tillering stage. Granstar (%75 tribenuron methyl) herbicide was applied at 1.5 kg/ha rate to control broadleaf weeds and İlloxan (284 g / L diclofop methyl) was applied to control grasses. Barleys were harvested in June for both years. The recorded data were analyzed using ANOVA and means were separated by LSD.  (Table.3). During 2009-2010 growing season grain yield increased proportional to the rates of applied ethephon. The cultivars produced 2947 kg/ha when was not treated with ethephon while 600 g/ha ethephon treated barley plants produced 4856.75 kg /ha. Increased rate of ethephon (600, 720, 840, and 960 g/ha) did not significantly increased yield while 1080 g/ha ethephon slightly reduced yield. Although the differences were not statistically significant, yield gradually decreased as ethephon rate increased from 600 to 960 g/ha ( Figure 1). The yield decreased after the 600 g/ha doses. In regard to the interactions between barley cultivars and ethephon rates, control (untreated) plants of the local barley produced the lowest grain yield (1887.50 kg/ha) while the highest grain yield (3874.50 kg/ha) produced by Sur-93 and ethephon (600 g/ha) combination in 2008-2009 while during 2009-2010 the lowest yield (2068.50 kg/ha) was produced by local barley cultivar when untreated with ethephon and the highest yield (4856.75 kg/ha) was produced by Sur-93 and ethephon (600 g/ha) combination. Based on average yield, Sur-93 cultivar produced higher (3582.69 and 4500.83 kg/ha) yield in both years compared to the local cultivar (2662.00 and 3081.28 kg/ha). The results indicated that Sur-93 and the local cultivar responded differently to the applied rates of ethephon. Sur-93 grain yield increased proportionally as ethephon applied ethephon rates increased up to 600 g/ha while the local cultivar grain yield proportionally increased as applied ethephon concentration increased up to 960 g/ha.
Ethephon applications reduced plant height and lodging but increased grain yield Sur-93 produced the highest grain yield of 4365.63 kg/ha when treated with ethephon 600 g/ha while the local cultivar produced the highest yield of 3591.00 kg/ha. Regression analysis of Sur-93 and ethephon concentrations indicated that regression equation was as y =284.1+ 0.4271x -0.0003x 2 (R 2 = 0.974) (Figure 1) while regression equation of the local cultivar and ethephon concentrations was as y=208.8+0.133x (R 2 =0.929) (Figure 2) The barley cultivars included in this study were tall cultivars but susceptible to the lodging. Rainy seasons, irrigation and application of N fertilizers cause overly growing of already tall varieties and worsen lodging during spike development stage.
Ethephon application prevent plant lodging by reducing plant height, and reduced lodging improve grain development that lead increased yield.
Especialy local barley cultivars are susceptible to loading which is the main cause of reduced grain yield in the region. Ethephone treated plants produced greater grain yield compared to untreated plants.  In 2009-2010, the shortest plant height (58.95 cm) was obtained from Sur-93 and ethephon (840 g/ha) interaction and the tallest plant height (98.950 cm) was observed from Sur-93 x 0 g/ha ethephon interaction.
Average results of a 2-year study indicated that plant height of Sur-93 varied from 58.625 cm (1080 g/ha ethephon application) to 100.550 cm (0 g/ha ethephon application). Plant height was reduced as ethephon concentration increased. However, height of plants treated with either 960 or 1080 g/ha ethephon was not significantly different. The local barley cultivar height ranged from 59.575 cm (1080 g/ha ethephon application) to 85.063 cm (0 g/ha ethephon). Local barley height was not significanly differ at 840, 960 and 1080 g ha -1 ethephon application. In both years, local barley height decreased as ethephon concentration increased (Figure 4).
Regresssion analysis of average plant height of 2 years and ethephon application indicated that regression equation for Sur-93 cultivar was determined as y=106.9-5.675x and (R² = 0.985) while for local barley cultivar was determined as y=85.68-3.220x ve R² = 0.874 ( Figure. 4).
Previous studies have indicated that barley plant height can be reduced with application of ethephon (Lunsgaard 1984 and1986;Szirtes et al. 1986;Lloveras et al. 1990;Ege 1991;Stulova and Egorov 1991;Ma and Smith 1992;Stobbe et al. 1992;Webster et al. 1993).  Şekil 4. 2008-2009, 2009-2010  During the growing season of 2008-2009, regarding lodging and ethephon rates, the highest (98.75%) lodging rate of the local barley cultivar was recorded at 0 g/ha ethephone application while the lowest lodging (0%) was recorded at interactions of Sur-93 treated with 960 and 1080 g/ha rates of ethephon. In 2009-2010, the lodging was like the previous growing season. The highest lodging (100%) was observed from the local barley cultivar and 0 g/ha ethephon interaction while the lowest lodging (0%) was observed from Sur-93 and 960 -1080 g/ha ethephone interactions.
Based on average of 2 years lodging value of Sur-93 varied from 0% when plants treated with 960 and 1080 g/ha to 58.75% when untreated with ethephon. Plant lodging reduced proportionally to the concentrations of ethephon, however, the highest reduction of lodging was between 480 and 600 g/ha ethephone applications while lodging reduction of 960 and 1080 g/ha was not significantly different. Height of the local barley was ranged from 59.57 cm when plants treated with 1080 g/ha ethephon to 85.06 cm when plants when plants was not treated with ethephon. Although plant height gradually reduced as ethephon rate increased the effect of ethephon rates from 840 to 1080 g/ ha ethephon was significantly different. In both years, plant height was reduced as apllied ethephon rate increased (Figure 4). Regression of lodging rate and applied ethephon rates were significant and regression between Sur-93 and ethephon rates was determined y=62.06-7.593x and (R² =0.940) and regression between the local variety and

yetiştirme sezonlarında farklı etephon dozu uygulamalarında yatma yüzdeleri
Barley cultivars added to this study were susceptible to lodging. Susceptible barley cultivars when irrigated and fertilized lodging especially during spike stage become a serious problem. Kernel of lodged plants cannot develop well thus kernels become light-weighted. In this study, applied ethephon rates reduced plant height and therefore delayed spiking which helped better development of heavy kernels. These results agree with the previous studies (Dziamba 1986;Stobbe et al. 1992;Akcura 2001;Aral 2001;Tripathi et al. 2004;Rajala et al. 2002;Auskalniene 2005;Ramburan and Greenfield 2007).

Thousand Kernel Weight
Thousand-kernel weight of Sur-93 ranged from 37.30 g when treated with 240 g/ha ethephon to 47.035 g when treated with 960 g/ha ethephon during 2008-2009 (Table 5). Although 1000-kernel weight increased as applied ethephon rate increased, ethephon rates higher than 840 g/ha did not increase kernel weight significantly. Thousand-kernel weight of Sur-93 ranged from 37.942 g when treated with 0 g/ha ethephon to 45.812 g when treated with 840 g/ha ethephon during 2009-2010. The increase in ethephon rate from 840 to 1080 g ha did not cause any significant change in thousand kernel weight. Although 1000-kernel weight increased as applied ethephon rate increased, ethephon rates higher than 720 g/ha did not significantly increase the kernel weight. The difference between ethephon doses 840, 960,1080 was found insignificant.
Thousand  In regard to 1000-kernel weight from barley cultivars and ehtephon interaction, the lowest 1000-kernel weight was recorded from interaction of the local barley and 0 g/ha ethephon application while the highest 1000kernel weight (47.035 g) was recorded in Sur-93 with 960 g/ha ethephon application in 2008-2009. In 2009-2010, the lowest 1000-kernel weight (31.928 g) was from the untreated local barley. The highest 1000-kernel weight (45.812 g) was from interaction of Sur-93 and 840 g/ha ethephon application (Table 5).
Average 1000-kernel weight of 2 years varied from 31.745 g (local barley x 0 g/ha ethephon) to 46.259 g (Sur-93 x 840 g/ha ethephon). Thousand-kernel weight increased as applied ethephon rate increased. Thousand-kernel weight of the local barley increased as applied rates of ethephon increased. No significant difference of 1000-kernel weight detected when the applied ethephon rate increased from 960 to 1080 g/ha ( Figure 5).

Conclusion
Grain yield of Sur-93 and the local barley cultivars were 2752.25 kg/ha, 4365.63 kg/ha and 1970.00 kg/ha, 3591.00 kg/ha, respectively. Ethephon application up to 600 g/ha significantly increased grain yield of Sur-93 barley. The grain yield of barley did not significantly increase with 720 g/ha ethephon application and higher doses. Grain yield of the local barley significantly increased by ethephon application up to 840 g/ha. There was no statiscal difference between the dosesafter the 840 kg dose.
Ethephon application reduced plant height and numbers of kernels but caused well kernel development thus 1000-kernel weight was increased. The recorded highest grain yield due to ethephon applications was 4365.63 kg/ha for Sur-93 when treated with 600 g/ha ethephon while the recorded highest grain yield for the local barley was 3591.00 kg/ha when treated with 960 g/ha ethephon. The lodging of barley cultivars decreased with the increase in ethephon application rate. The highest lodging rate was recorded in control treatments, while the lowest lodging ratio was obtained with the highest ethephon dose.