Effect of Priming on Yield and Yield Components of Soybean [Glycine max (L.)Merrill] Varieties at Assosa, Western Ethiopia

The use of low quality soybean seed is a major limiting factor for yield reduction under tropical and subtropical conditions. Field experiment was carried out at Assosa Agricultural Research Center to determine the effect of priming on yield and yield components of soybean varieties. The experiment had three varieties (Belessa95, Wello and Gishama), three priming types [GA 3 (100PPM), KH 2 PO 4 (50 PP) and water] and three priming durations (0, 6, 12hr) were evaluated using a randomized complete block design (RCBD) in four replications. Highly significant (P ≤ 0.01) difference between interaction of varieties by, priming type and soaking durations for plant height at maturity, number of pods per plants, number of primary branches per plants, yield per hectare, and Varieties by priming type interaction showed highly significant (P ≤ 0.01) difference for day to 50% flowering, plant height at maturity, number of pods per plants, number of primary branches per plants, harvest index, thousand seed weight and significant (P ≤ 0.05) for number of seed per pod and stand count at harvest. The tallest plant height (87.26cm) was recorded when Belessa95 primed with water for 12hr. Also highest number of pods per plant (46) was observed on Belessa 95 primed with KH 2 PO 4 for 12hr, the highest number of seeds per pods (3) was observed when Wello primed with water and highest yield (3418.85 Kg) was recorded for Wello primed with water for 6hr and highest stand count at harvest (119.67) was recorded for Wello primed with water. Hence, Water priming was recommended to user to overcome the problems of poor crop emergence and establishments under this adverse environmental condition.

and Wilson, 1998). The crop is also highly important in cropping system thereby enriching soil fertility through biological N fixation in symbiosis with bacteria better than other legume crops. On the average soybean can fix over 75 kg nitrogen per hectare (LaRue and Patterson, 1981).
The success of the soybean industry is attributed to the crop's agronomic performance and composition (Liu, 2000). Soybean can be grown in a wide range of environments, has moderate drought tolerance, and does not require nitrogen fertilization because of symbiosis with the nitrogen fixing bacteria; Rhizobium. Roughly 60% of the dry weight of soybean seed is composed of protein and oil, and as a result soybean seed has the highest protein and second highest oil content among cereal and legume species (Liu, 1997). These facts make soybean an important crop for oil manufacturing, animal feed, and food production (Hymowitz et al., 1972;Wilcox and Shibles, 2001). Soybean is important because of its nutritional qualities. It has high percentage of high quality and cheap protein and is a rich source of edible oil. The world production of edible oils consists of 30% soybean (Assefa, 2008). Soybean seed contains about 40-45% protein and 20-22% oil, 20-26% carbohydrate and a high amount of Ca, P and vitamins (Rahman et al., 2011). In Ethiopia, soybean was started in 1950's on introduced genotypes with main emphasis of identifying adapted lines for the potential areas, replacing imported soybean flour, introducing into the existing cropping systems, and diet of the poor farmers (Amare, 1987). It is a crop that can play major role as protein source for resource poor farmers of Ethiopia who cannot afford animal products. In our country, now a day's soybean is highly utilized in nutrition industries for both food and feeds. According to CSA (2015) the area under soybean cultivation in Ethiopia is estimated about 35259.76 hectares (ha) and 72183.75 tons of production with the productivity of 2.04 tons ha-1 which is by far lower than the world's average of 2.3-4.0 tons ha-1 and in Benishangul-Gumuz Region the area under soybean cultivation is 12939.90hectares and productivity is 1.90 tons ha -1 (Masuda and Goldsmith, 2008). Soybean was introduced into Benishangul -Gumuz during resettlement program. Since then, the farmers grow soybean on small scale as sole crop primarily for its economic merit and home consumption. In Assosa zone, soybean was the most dominant pulse crop with the total production area and productivity of 3617.63 ha and 1.46 tons/ha, respectively (CSA, 2015). Now a day's, soybean production is highly raised in the region due to increased demand of the farmers and investors.
Even if the region is suitable for production the use of soybean seeds of low physical and physiological quality is a common practice under this environment, leading to inadequate plant population which final reduce the production and productivity in the field. Faster germination and emergence is an important factor for better, more and uniform stand establishment. This poor crop emergence and establishments might happened due to unpredictable and erratic rain fall, low or inadequate soil nutrients, low quality seeds, hard seed coat, sowing time, low moisture contents of the soil, heat stress, limited access to mechanization and diseases of the crops like soybeans which are mainly grown under such environments all contribute to failures and poor crop stand establishment that may survive the crop poorly under such adverse environmental conditions. Under such conditions seed germinations, seed emergence and seedling establishments can be inhibited and reduced. Therefore, seed priming (seed invigoration) before seed sowing has been a best solution to overcome such adverse environmental effects for better, more and uniform seed germination, seed emergence and seedling establishment. Concerning priming treatments studies on soybean are not adequate but encouraged so more information is required to use this technology in seed production. Hence, objectives of this study were:- To determine the effect of priming on yield and yield components of soybean varieties.

Materials and methods 2.1.
Description of the Study Sites The field experiment was conducted in Benishangul-Gumuz Regional State, at Asossa Agricultural Research Center (AARC) on station in the 2015 main cropping season under rain fed field conditions. Benishangul-Gumuz Regional State is geographically located at the latitude of 9 0 30' to 11 0 39'' N and longitude of 34 0 20' to 36 0 30''E covering a total land area of 50,000 square kilometer. The study site is located at 10 0 02' 05'' N latitude and 34 0 34' 09'' E longitudes and situated east of Assosa town and west of Addis Ababa about 14 km and 653 km distance, respectively. The area experiences a unimodal rainfall pattern and has annual rainfall of about 1118 mm out of which 936.3 mm rain was recorded during the growing season of the crop. The rainy season occurs from March to December and the maximum rain is received in August. The minimum and maximum temperatures are 11.9 0 C and 32.7 0 C, respectively. The soil type of the area is Nitosol which is dark reddish brown to dark red in colour and the crops mainly cultivated in the area are sorghum, maize, soybean and finger millet (AARC, 2007).

2.2.
Treatments and Experimental Design The treatments consist of three varieties of soybean namely Belessa-95, Wello and Gishama and priming treatments GA3 (100PPM), KH2PO4 (50PPM) and water at timings of 0, 6 and12hr. The size of each plot was 4x3m (12m 2 ). The space between blocks was 1m, the space between rows in each plot was 60cm and spacing between plants was 5cm. The rate of fertilizer used was100kg DAP which contains 18%N and 46%P2O5 as a source of

2.3.
Experimental Procedure and Field Management The land was prepared for planting by tractor, disked and harrowed. The seeds of all the three varieties were soaked in GA3 (100 PPM), KH2PO4 (50 PPM) and water for 0, 6and12hr. The seeds of all the varieties were used as control where Hydro priming and osmo priming treatments were not applied. After giving treatment for 0, 6and 12 hours the seed was removed from water and solutions then it was kept in filter paper to remove the remaining solution. All the primed seeds were again re-dried at room temperature until they gain their original seed moisture content. Seed was sown in last week of June 2015 in rows by placing the seeds at an appropriate distance as per the treatments with the help of tape meter and then covered it manually with the soil. All cultural practices such as weeding fertilizer application etc were applied uniformly to all plants. The crop was harvested manually when the crop reached physiological maturity and sun dried for up to 14 days to adjust the moisture contents of the seed to 10%.

2.4.
Data Collected 2.4.1. Growth phenology, yield component and yield Days to 50% flowering: The number of days taken from the date of sowing to flowering were calculated and expressed in number as days taken for 50 per cent of plants showed flowers. Plant height: The plant height on five randomly selected and tagged plants were measured from the base of the plant to the tip of the shoot apex at physiological maturity and the average height of five plants was worked out and expressed in centimeters. Days to Physiological maturity: were recorded as the number of days from sowing to 90% plants per plot attains maturity (the seed as well as pod turn yellow).

Number of pods per plant:
The number of pods from five randomly selected and tagged plants and average was taken. Number of seeds per pod: The number of seeds per plant was counted from five randomly selected plants and the average was taken.

Number of Primary branches per plant:
The number of primary branches on the main stem per plant harvested at maturity was obtained by counting the branches from five randomly selected and average was taken. Stand count at harvest: the number of plants per net plot at harvest. Harvest index was determined as the ratio of grain yield to the total above ground dry biomass yield. Thousand seed weight: determined by weighing 1000 seeds sampled from each plot using an electronic sensitive balance. Yield per hectare: The matured pods harvested from the net plot in each treatment were sun dried and the seed was separated. The weight of the seeds harvested from net plot area was recorded and converted to yield per hectare after adjusting to 10% moisture content.

2.5.
Data Analysis Data were subjected to Analysis of Variance (ANOVA) using Gomez and Gomez (1984) with computer software SAS statistical package, Version 9.1 (SAS, 2000). Whenever the effects of the factors were found to be significant, the means were compared using the Tukey's Studentized Range (HSD) test at 5% level of significance.

Results and discussions 3.1.
Field Experiment 3.1.1. Days to 50% flowering There was a highly significant (P≤0.01) difference among varieties, seed priming type and their interaction effect for days to 50 per cent flowering. Wello(2)variety which is primed with GA3(B)took significantly lesser days (82) to 50 per cent flowering followed by wello(2) primed with KH2PO4(C)and unprimed(A)Wello variety which took (85.33) days to 50per cent flowering. Significantly delayed flowering was exhibited on unprimed (A) Belessa95 (1) variety which took (93days) and was at par with Belessa 95(1) variety primed with GA3 (B) and KH2PO4(C) which took (91days) whereas the other combination showed an intermediate values (Table1). The results agreed with Khairul, et al.(2015) who reported that chickpea seed primed with GA3took minimum number of (70) compared to hydro primed chickpea seed which took (82.33) days to 50% flowering. Similarly, Punjabi et al. (1992)reported that soybean variety applied with GA3(100ppm) initiated flowering and increased number of flower per plants (35.44) as compared to control (16.78). On the other hand, Harris et al. (2007) found that the priming in maize led to better crop establishment and growth, earlier flowering and greater yields. The accelerated flowering in case of GA3 might be due to their effect in the fast emergence of the seeds at the beginning and the variation in case of the three different unprimed soybean varieties might be due to early and late flowering of the varieties. In addition to better establishment, farmers reported that primed crops grew more vigorously, flowered Journal of Natural Sciences Research www.iiste.org ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online) Vol.10, No.11, 2020 earlier and yielded higher (Farooq et al., 2008). Plant height There was a highly significant (P≤0.01) difference among varieties, duration of priming, seed priming type and interaction effect for plant height at maturity. The tallest plant height was recorded for Belessa 95 variety (87.27cm) hydro primed for 12 hour which was at par with Gishama hydro primed for 6 hr (86.57cm) and for 12hr (85.23cm) (Table2).Gishama variety which was primed with GA3 for 0, 12and 6 hours has also the highest plant height (84.54cm), (83.80cm) and (83.67cm) respectively. This result was agreed with Punjabi et al. (1992) who reported that Soybean seed primed with GA3(100ppm) records the tallest plant height (57.10cm) as compared to control (25.11cm).This might be due to the importance of priming treatments for stimulations of genes that are important for enhancement of cell division which leads to increase plant height at maturity. Basically, plant height is a genetically controlled character, but several studies have indicated that the plant height can be increased or decreased by different seed quality enhancement practices Ali, (2009).The beneficial effect of exogenous application of GA3 to seeds might be due to the translocation of GA3 to the aerial part of plants, and this perhaps occurs to an extent that is enough to increase hypocotyls size and the consequent increase in first node height hence sufficient to positively affect plant height (Chavan et al.,2014) Bensen et al. (1990, demonstrate the hypocotyls growth rate is directly associated with the amount of GA3.Belessa 95 variety which was primed with KH2PO4 for 12hr records (79.4cm) plant height which is at par with Wello and Belessa 95 variety primed with KH2PO4 for 12hr which records (79.2cm) and (79.4cm) respectively. The result is in agreement with Mohammadi(2009) who reported that soybean seed primed with potassium nitrate showed the highest plant height(43.4%) as compared to control. The enhanced plant height may also be due to the improved and faster plant emergence in GA3, Water and KH2PO4 primed varieties which created cooperative competition among the plants for light and resulted in taller plants. The results agree with Harris et al. (2000) who reported that seed priming of ten rice varieties resulted in taller plants (108 cm and 94 cm) in two years. The shortest plant height was observed on the unprimed Wello variety (68.13cm),Belessa 95 variety(72cm), Wello primed with GA3 for 0 hr (72.20cm) which is at par with Wello primed with KH2PO4 for 0hr (73.20cm) and Wello primed with GA3 for 0hr(73.72cm).

Physiological maturity
There was a highly significant difference among varieties and significant (P≤0.05) difference among priming types for hastening Physiological maturity. Among variety Wello variety took significantly lesser days (120.8) to Physiological maturity as compared to Belessa 95 and Gishama which took (123.2) and (125) days respectively(Table3). Among priming types there was significance Soybean varieties which was primed with GA3 took significantly lesser days (122) to Physiological maturity compared to Water and KH2PO4 which took (123.11) and (123.56) days respectively (Table3) this might be due to the faster germination of seed as the results of gibberallic whereas the variation between varieties to accelerated or delayed physiological maturity might be due to genetic variations among them. 0.80 Where, GA3=Gibberellic acid, KH2PO4=Potassium dihydrophosphate. Means followed by the same letter(s) at each column and row are not significantly different from each other at 0.05 level of probability.

Number of pods per plant:
There was a highly significant (P≤0.01) difference among varieties, priming type, priming durations and their interactions for number of pods per plant. The highest number of pods per plant was observed on Belessa 95 variety primed with KH2PO4 for 12hr (46.00) and 6hr (45.33) followed by Wello variety primed with KH2PO4 for 12hr (45.13) and 6hr (44.87) whereas the lowest number of pods per plant was observed for Gishema varieties primed with GA3for 0hr (22.73), unprimed Belessa 95 (30.27),Wello(31.40)and Gishema (24) varieties (Table 4). These results are similar with the finding of Shahram (2015) who reported that soybean seed primed with KH2PO4 and water records (132.8) and (124.5) number of pods per plant respectively compared to control (85.91). Similarly, Mohammadi (2009) reported that soybean seed primed with potassium nitrate showed the highest value of number of pods per plant (56.5%) as compared to control. Wello variety primed with GA3 for12 hr gave 43.53 pods per plant which was at par with Belessa 95 primed with water for 12hr (43.20) and 6hr (41.93) and Wello variety primed with water for 12hr (41.27) and 6hr (40.40) ( Table 4).These results are in line with the report of (Khairul, et al.,2015) who reports that chickpea seed primed with GA3 225ppm and GA3 300ppm resulted in (55.50) and (52.38) number of pods per plants respectively compared to hydro primed chickpea seeds. Similarly, Aldesuquy and Ibrahim (2000) reported that the seed treatment with shikimic acid improved yield and yield components of cowpea plants by increasing the number of pods per plant and number of seeds per pod.
( Table 2).The three unprimed (A) soybean varieties show the lower number of seeds per pod Gishema (3) (2.33), Belessa95 (1) (2.47) and Wello(2) (2.47) compared to the primed soybean varieties (Table 1).These results are similar with the report of Mohammadi (2009) who reported that soybean seed primed with potassium nitrate showed the highest number of seeds per pod (23.8%) as compared to control. Similarly, Shahram (2015) reported that soybean seed primed with water and KH2PO4 gave the same seed number seed per pods which is (2.59) and (2.52) respectively compared to control (1.94). Similarly, results were also reported by Rashid et al. (2004) in mungbean reported that the primed seed plants produced more seed per pod.

Number of Primary branches per plant
There was highly significance difference (P≤0.01) among varieties, priming type, durations of priming and their interaction effect on number of primary branches per plant. The highest number of primary branches per plant was observed on Wello and Belessa95variety primed with KH2PO4for 12hr (6.60) and for 6hr (6.54) respectively which was at par with Gishema and Belessa95 primed with KH2PO4 for 12hr (6.53) and for 6hr (6.47) respectively. Similarly, the highest number of primary branches per plant was also observed on hydro primed Belessa95variety for 6hr (6.47) and for 12hr (6.27) and Gishema hydro primed for 6hr (6.40) and for 12hr (6.13).The lowest number of primary branches per plant was recorded on Gishema variety primed with GA3 for 6hr (2.47) whereas the other showed an intermediate value (Table 5). Unprimed soybean varieties gave lower number of primary branches per plant. The results are in agreement with those obtained by Kaur et al. (2002) who reported that primed chickpea seeds increased number of branches 30-40% than unprimed seeds. Similarly, Punjabi et al.(1992) found that Soybean seed primed with GA3(100ppm) records the highest number of branches per plant (5.11) as compared to control (3.89).The variation in the number of branches might be due to the vigorous growth of the plants due to the priming effects.
Journal of Natural Sciences Research www.iiste.org ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online) Vol.10, No.11, 2020  1.38 CV 9.92 Where, PT= Priming types GA3=Gibberellic acid, KH2PO4=Potassium dihydrophosphate. Means followed by the same letter(s) at each column and row are not significantly different from each other at 0.05 level of probability.

Stand count at harvest
There was a highly significant (P≤0.01) difference due to varieties, priming type and priming duration and significant (P≤0.05) interaction effect between variety and priming type for stand count at harvest. The highest stand count at harvest was recorded for Hydro primed(D)Wello (2) (Table 1).

Harvest index
There was highly significant difference (P≤0.01) among varieties, priming type and between their interactions effects for Harvest index. The highest harvest index was observed on unprimed (A) Belessa 95(1) variety (31) and unprimed (A)Gishema(3)variety (30.67) followed by Wello(2) variety primed withKH2PO4(C) (30.33). Whereas the lowest harvest index was recorded on Wello(2)variety primed withGA3(B) (21.67) followed by unprimed (A)Wello(2) variety (25.67) which were statistically similar results with that of Belessa 95(1) variety primed with GA3(B) (25.78) and Gishema(3) variety primed with GA3(B) (25.89) ( Table 1).The findings are in agreement with Shahram (2015) who reported that soybean seed primed with water and KH2PO4 records the lowest harvest index (37.32) and (37.60) respectively compared to control which records (40.13) harvest index. It has also been observed that seed priming improved allometric traits, grain yield and harvest index (Ruan et al., 2002) 3.1.9. Thousand Seed weight The result of the study showed that there was a highly significant (P≤0.01) difference between varieties, priming type sand their interaction effects on Thousand Seed weight. The highest hundred seed weight was recorded on Gishema (3)variety primed with water (D) (166.30) followed by Gishema (3)variety primed with KH2PO4(C) (163.90) and the lowest hundred seed weight were observed for Wello (2) variety primed with GA3(B) (136.70) followed by unprimed(A) Wello (2) variety (140.00).Whereas the other shows intermediate values (Table 1). The results are in agreement with Shahram (2015) who reported that the soybean seed primed with water and KH2PO4 gave the highest thousand seed weight of (142.23) and (140.33) respectively compared to control(116.37).

Yield per hectare
Seed yield is the ultimate output of a crop around which all the other factors revolved. There was highly significance (P≤0.01) difference between varieties, priming type, durations of priming and their interaction effect for increments of yield per hectare. The results are in agreement with Harris et al., (1999) who reported that primed crops produced higher yields than non-primed crops. The highest yield per hectare was recorded on Wello variety primed with water for 6hr (3418.85 Kg) followed by Wello variety primed with GA3 for 6hr (3412.15 Kg) that was at par with Wello variety primed with GA3 for 12hr (3406.60 Kg), for 0hr (3329.98 Kg) and Wello variety primed with KH2PO4 for 12hr (3395.24 Kg) and Wello variety primed with water for 12hr (3370.48 Kg), for 0hr (3297.59Kg) (Table6).
This result are consistent with the findings of Shahram (2015) who reported that soybean seed primed with water significantly increases yield per hectare (4.96ton/ha) compared to seed primed with KH2PO4 (4.61ton/ha) and control which records (4.13ton/ha). It was also reported that soybean seed priming made better seedling emergence and yield improvement (Arif et al., 2008).Similarly, Taylor and Harman, (1990) reported that in the Journal of Natural Sciences Research www.iiste.org ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online) Vol.10, No.11, 2020 low external input system of Bihar and West Bengal, in India, primed plots of chickpeas out-yielded non-primed plots in 41 trials with an average yield increase of around 13%. The lowest yield per hectare was observed on Gishema variety hydro primed for 0hr (2373.08) and with GA3 for 0hr (2385.44) that was at par with unprimed Belessa 95 variety(2390.55) and Gishema variety (2392.76).This results are in line with the report of Chavan et al., (2014) who have reported that soybean seed variety primed withGA3, KH2PO4 (100ppm) and water gave highest yield per hectare (2954.50),(2892.00)and (2715.00)respectively over the unprimed one(2403.20). (Mewael and Ravihunja (2008) have reported that soybean seeds primed with CaCl2. 2H2O,GA3 and KH2PO4 recorded (20.73,17.93,17.15 and 8.6%) increment in seed yield per hectare respectively over unprimed seeds. Priming of chickpea seeds has been reported to increase the seed yield (Kaur et al., 2002). Shahram (2015) suggested that hydro-priming is a useful method for improving seedling vigor, establishment and yield of soybean in the field.

. Correlation Coefficients between yield and agronomic traits of soybean varieties.
Correlation analysis between seed yield and the other field parameter showed that significant associations were observed between days to 50% flowering, Harvest index, thousand seed weight, number of pods per plant, number of seed per pods, physiological maturity and stand count at harvest. However, non-significant associations were observed among seed yield, number of primary branches and plant height at maturity (Table 7). There were highly positive correlations between seed yield with number of pods per plant(r=0.54), number of seed per pods(r= 0.42) and stand count at harvest(r=0.45) whereas highly negative correlations between seed yield with day to maturity(r= -0.71), days to 50% flowering(r= -0.67), Harvest index(r= -0.39) and hundred seed weight(r= -0.34) (table 7).

Conclusion and Recommendation
Priming treatment improves or enhanced most of the measured field parameters of the varieties. Under field conditions, there was highly significance(P≤0.01)difference among varieties, priming types, priming durations and their interactions for plant height, number of pods per plants, number of primary branches per plants and yields per hectares. The tallest plant height was recorded for Belessa 95 variety (87.26cm) hydro primed for 12 hour, the Journal of Natural Sciences Research www.iiste.org ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online) Vol.10, No.11, 2020 52 highest number of pods per plant was observed on Belessa 95 variety primed with KH2PO4 for 12hr (46.00).Also, highest number of primary branches per plant was observed on Wello and Belessa95variety primed with KH2PO4 for 12hr (6.60) and for 6hr (6.54) respectively. Most of the Priming treatments increases the yields per hectares compared to the controls. The highest yield per hectare was recorded on Wello variety primed with water for 6hr (3418.85 Kg). Also highly significant (P≤0.01) differences were observed for variety by priming interaction effects for day to 50% flowering, harvest index, thousand seed weights and significance differences for number of seeds per pods and stand counts at harvest. The lesser days to 50% flowering (82 day) was taken by Wello variety primed with GA3.The highest number of seeds per pods were observed when Wello variety is primed with water (3) and KH2PO4 (3) and the highest stand count at harvest was recorded for Hydro primed Wello variety (119.67). Correlation analysis between seed yield and the other field parameter showed that significant (P ≤ 0.05) associations were observed between days to 50% flowering, Harvest index, thousand seed weight, number of pods per plant, number of seed per pods, physiological maturity and stand count at harvest. Generally from field observations soybean varieties primed with water (hydro priming) and GA3 priming Medias showed better results followed by KH2PO4 on most and each of the measured parameters. Hence, better to recommend for seed growers Hydro priming prior to seed sowing because, simple to use, cost effective and easily available for seed growers to overcome the problems of poor crop emergency and establishments under such adverse environmental conditions comparing to GA3 priming media. However, this study was done only for one season at one location using three varieties, priming media and soaking duration. So that, to give conclusion and recommendations furthermore studies could be made on multiple varieties, priming medias and durations of soaking in research centers, on fields of soybean seed growers and on farmers' fields of different soybean growing areas of Ethiopia.