Abstract: In order to assess responses of eight soybean cultivars to drought stress and manganese foliar application, a field experiment was conducted as split plot based on randomized complete block design with three replicates at research station of Islamic Azad University, Kermanshah province, Iran during 2012, growing season. At the end of growing season, economic and biological yield were determined. Also, oil and protein contents in soybean grain were measured. Statistical analysis showed that irrigation and manganese interaction had significant effects on economic and biological yield, while, this treatment had no significant effects on oil and protein in soybean grain. In addition, there are significant differences among cultivars in economic and biological yield. Based on results obtained, withholding irrigation at flowering stage reduced oil, protein, economic and biological yield, but this reduction was not statistically significant for the oil. The lowest oil, protein, economic and biological yield were recorded in I2Mn0C2, I1Mn0C4, I2Mn0C5 and I2Mn0C4 treatments. There was a significant and positive correlation between economic yield with oil percentage and biological yield.
INTRODUCTION
Availability of micronutrients in calcareous soil is influenced by soil moisture. Also, in calcareous soils wet and dry periods can influence manganese availability by root plants. Under drought stress, plant roots cannot absorb micronutrients (Heidarian et al., 2011), such as manganese and foliar spraying of manganese is useful and more influential as compared to soil application (Narimani et al., 2010). In the other side, Soybean is considered a sensitive crop to drought stress (Lobato et al., 2008) and manganese deficiency (Barker and Pilbeam, 2007). Manganese fertilization could be very important in the case of soybean grown in soil with low manganese availability (Hellal and Abdelhamid, 2013), especially at water deficit conditions (Vadez et al., 2000). Recent evidence in the literature indicates that deficiencies in minerals due to drought stress at any plant growth stage result in poor seed quality and low yield (Bellaloui et al., 2013). In addition, drought stress is recognized as a affecting factor in soybean oil and protein contents (Kumawat et al., 2000; Rotundo et al., 2009; Kirnak et al., 2010). Based on Wilson (1995), Liu et al. (1995) and Maestri et al. (1998) studies protein and oil content, chemical composition of oil and protein and grain appearance are three important factors determining the quality of soybean. Previous studies indicated that there exists an inverse relationship between seed protein and oil concentration (Panthee et al., 2006; Okporie and Oselebe, 2007) and there is positively correlation between quality traits with seed yield as a quantity trait (Rajni et al., 1983). Therefore, the main objective of this study was to evaluate the effects of withholding irrigation and manganese foliar treatments on some quantitative and qualitative traits in eight cultivars of soybean.
MATERIALS AND METHODS
This experiment was conducted as split split plot in randomized complete block design with three replications in 96 plots at Agricultural Research field of Islamic Azad University of Kermanshah, Iran (34˚23'N, 47˚8'E; 1351 m elevation) during 2012 growing season. Eight commercial soybean cultivars, Clark (V1), Williams (V2), Sahar or Pershing (V3), Hobbit (V4), Gorgan 3 (V5), M7 (V6), M9 (V7) and DPX (V8), were grown under field conditions. Main plot treatments consisted two irrigation regimes: (I1) Irrigation at all of growth stages, (I2) Irrigation Withholding at flowering stage, Subplot included (Mn0) spray with distilled water, (Mn1) manganese spray and eight soybean cultivars arraigned in sub subplot. Soil samples were collected from experimental area at 0-30 cm depth. The texture of the soil based on silty clay with (silt 49.1%, clay 42.4% and sand 8.5%), pH 7.3, organic matter 2.6, total nitrogen 0.11%, available phosphorus, potassium, zinc, iron and manganese 8.2, 531, 0.81, 2.76 and 4.49, respectively. All seeds were inoculation with Bradyrhizobium japonicum immediately before sowing. Each plot was 6 m in length, 2.4 m in width, 0.6 m in row spacing and with density of 33 plants per meter square. The quantity of irrigation water in each plot was calculated according to Karam et al. (2005), controlled by counter and exercise irrigation treatment at flowering stage. At the V4 growth stage based on Fehr and Caviness (1977), the plants were sprayed twice (with one week interval) with 0.5% manganese liquid or distilled water until the leaves were wet. At the end of growing season and harvest time, two middle rows of each plot were completely harvested considering the sides. Weight 13% deduction of moisture, grain dry weight was calculated and considered as economic yield. To determine biological yield, total plant dry weight was employed as biological yield. Also, oil and protein contents in soybean grain were measured according to Emami (1996) and Jung et al. (2003). Data for evaluated traits were statistically analyzed using a standard analysis of Variance technique using the MSTATC software. Means were separated by the Least Significance Difference Test (LSD) at 5 percent probability level.
RESULTS AND DISCUSSION
The results of analysis of variance were shown in Table 1. Irrigation treatments made significant effects on oil at 5% level and economic and biological yield at 1% level. The similar results were reported by Aderolu (2000). Also, manganese foliar application had significant effects on protein (p<0.05) and economic and biological yield (p<0.01). While, Protein and oil unaffected by irrigation and manganese treatments, respectively (Table 1). The positive effect of manganese foliar application on seed protein of safflower was emphasized by Movahhedy-Dehnavy et al. (2009). Statistical analysis showed that irrigation and manganese interaction had significant effects on economic and biological yield, while, (I) × (Mn) treatment had no significant effects on oil and protein in soybean grain. The similar results were obtained by Babaeian et al. (2011). The results of this experiment show that there are significant differences among cultivars in economic and biological yield (p<0.01). Among soybean cultivars there was no significant difference in terms of oil and protein. Effect of (I) × (C) and (Mn) × (C) interactions on biological yield were significant probability levels at 1 and 5%, respectively. Whereas, other evaluated traits unaffected by these interaction effects.
| Table 1: | The results of analysis variance of oil, protein, economic and biological yield in eight soybean cultivars under short-term drought stress and manganese foliar application |
| -: ns, * and **: Non significant, significant at 5 and 1% levels of probability, respectively | |
| Table 2: | Means comparison of qualitative and quantitative traits in eight soybean cultivars under short-term drought stress and manganese foliar application |
*Similar letters in each column shows non-significant difference according to LSD test in 5% level, **I1: Irrigation at all of growth stages and I2: Withholding irrigation at flowering growth stage; Mn0: Spray with distilled water and Mn1: Manganese spray, C1: Clark, C2: Williams, C3: Pershing, C4: Hobbit, C5: Gorgan3, C6: M7, C7: M9, C8: DPX | |
Oil and protein contents were not affected by the interaction of (I) × (Mn) ×(C). In contrast, interaction effect of (I) × (Mn) ×(C) treatment had significant effects on economic yield (p<0.05) and biological yield (p<0.01). The results of means comparison (Table 2) were shown that withholding irrigation at flowering stage in I2 treatment reduced oil, protein, economic and biological yield compared regular irrigation (I1 treatment), However, this reduction was not statistically significant for the oil. These results are somewhat different from the results obtained by Zaman and Das (1991). With manganese foliar application, protein content, economic and biological yield increased by 5.47, 12.95 and 13.96, respectively. Hellal and Abdelhamid (2013) reported that total manganese uptake by the soybean plants per metric ton of grain production is 123 g. Manganese fertilization increased oil content in soybean grain, but this increased was not statistically significant. These results are in contrast with the results obtained by Yasari and Vahedi (2012) that showed the highest seed oil yield in soybean was obtained by applying manganese. Economic yield ranged between 2305.83-1627.50 kg ha–1 in cultivars. The highest and lowest economic yield was observed in C2 and C4 cultivars, respectively. The similar results for biological yield was observed and among cultivars C2 and C4 had the highest and lowest biological yield with 6159.25 and 4679.17 kg ha–1 (Table 2). Based on results obtained, the highest oil, economic and biological yield were achieved with manganese spray at regular irrigation (I1Mn1 treatment) by 19.92, 2605.12 and 6949.72 kg ha–1, respectively. So that, there are significantly differences between cultivars concerning oil and protein contents in soybean grain at different irrigation regimes (Table 3). Furthermore, at all of cultivars evaluated the highest economic and biological yield belonged to I1 (regular irrigation). Among cultivars C2 had the highest economic yield (2828.41 kg ha–1) and biological yield (7608.43 kg ha–1). Manganese application compared distilled water spray at water deficit condition led to increase in oil, protein, economic and biological yield by 4.81, 6.19, 22.23 and 23.19%, respectively (Table 3).
| Table 3: | The effect of (I) × (Mn) and (I) × (C) interactions on soybean qualitative and quantitative traits |
* Similar letters in each column shows non-significant difference according to LSD test in 5% level, ** I1: Irrigation at all of growth stages and I2: Withholding irrigation at flowering growth stage; Mn0: Spray with distilled water and Mn1: Manganese spray; C1: Clark, C2: Williams, C3: Pershing, C4: Hobbit, C5: Gorgan3, C6: M7, C7: M9, C8: DPX | |
These results are agreement with Movahhedy-Dehnavy et al. (2009) and Maghsud et al. (2014) findings. Fageria (2007) and Hellal and Abdelhamid (2013) emphasized that micronutrients such as manganese have important role in growth and yield of crops. In addition, Mn plays an important role in stabilization of structural protein (Popelkova et al., 2003). Concerning oil content in grain, response of Clark and Pershing cultivars to manganese application was better than the other cultivars tested. While, at manganese spray condition Hobbit, M9 and DPX cultivars had more protein in grains. In M1 treatment, the highest economic and biological yield was recorded in Williams cultivar (Table 3). Means comparison of quantity and quality traits in soybean grain under (I) × (Mn) ×(C) interaction effects was shown in Table 4. Generally, the highest oil, economic and biological yield were observed when that manganese was applied in irrigation regular treatment. Bellaloui et al. (2013) reported that nutrients deficiencies due to drought stress at any plant growth stage result in low quality and yield of crops. While, withholding irrigation and manganese application increased protein content in soybean grain. The role of micronutrients application in protein synthesis in crops grain was emphasized by Ziaeian and Malakoti (2002) study. Clark cultivar had the highest oil content in the grains.
| Table 4: | Means comparison of soybean qualitative and quantitative traits under (I) × (Mn) ×(C) interaction effect |
* Similar letters in each column shows non-significant difference according to LSD test in 5% level, **I1: Irrigation at all of growth stages and I2: Withholding irrigation at flowering growth stage; Mn0: Spray with distilled water and Mn1: Manganese spray; C1: Clark, C2: Williams, C3: Pershing, C4: Hobbit, C5: Gorgan3, C6: M7, C7: M9, C8: DPX | |
| Table 5: | Pearson correlation coefficients among evaluated traits in eight soybean cultivar under short-term drought stress and manganese application |
| -ns, * and **: Non significant, significant at 5 and 1% levels of probability, respectively | |
Among cultivars, DPX had more protein in the grain and the highest economic and biological yield belonged to Williams cultivar. The lowest oil, protein, economic and biological yield were recorded in I2Mn0C2, I1Mn0C4, I2Mn0C5 and I2Mn0C4 treatments. There was a significant and positive correlation between economic yield with oil percentage (r = 0.692*) and biological yield (r = 0.965**) (Table 5). Also, biological yield had a significant and positive correlation with oil content in soybean grain (r = 0.680*). In our experimental conditions, a significant correlation between oil and protein content in soybean grain was not recorded.
ACKNOWLEDGMENTS
The authors wish to thank from the Islamic Azad University of Kermanshah Branch for supporting projects.