ABSTRACT
Flax (Linum usitatissimum L.) is an important industrial crop in fiber production. This study is aimed to isolate specific germplazms with high potassium efficiency. Totally 50 flax germplazms were planted in an experimental field in Heilongjiang, China (126°28′E, 46°27′N). Fertilizer was applied under the soil before seeding with two potassium levels (K0, 0 kg/ha K2SO4; K50, 50 kg/ha K2SO4). The potassium utilization efficiency was calculated as fiber yield/(aboveground dry weight × potassium content), and the partial factor productivity was calculated as fiber yield/unit of K2SO4 applied (K50). The application of potassium fertilizer improved the agronomic and yield traits of most flax germplazms, including the plant height, technical length (length from cotyledon trace to base of the first branch), fiber content and yield, stem yield, and seed yield. However, the application of potassium fertilizer did not influence the plant length in 7 germplazms, technical length in nine germplazms, and stem yield in four germplazms. Based on the potassium utilization efficiency, flax germplazms were classified into four categories, including I (low efficiency, K0:17.62–34.38; K50:16.82–29.67), II/III (middle efficiency, K0:36.51–75.34; K50:32.56–58.74), and IV (high efficiency, K0:83.41–91.42; K50:61.38–71.39). Sofie, Yuan-2012-306, Yuan-2012-295, D93005-15-3 were identified to be high potassium utilization efficiency under both K0 and K50. The above agronomic and yield traits of flax were positively correlated with the potassium utilization efficiency. In addition, the partial factor productivity was greater than 70 kg/kg in 8 germplazms, and was lower than 50 kg/kg in 7 germplazms. The top five germplazms in partial factor productivity were Sofie, 92,104-9-3, y0332-1, D93005-15-3, and 98,019–10. To sum up, Sofie and D93005-15-3 with both high partial factor productivity and potassium utilization efficiency were isolated, presenting a promising prospect in agricultural production.
1. Introduction
Flax (Linum usitatissimum L.), belonging to the Linaceae family is an erect annual herb plant with slender stems (Neetu et al. Citation2012). As an important industrial crop, flax can provide two valuable products, including flax seed for oil and fiber for linen products (Xie et al. Citation2018). The fiber of flax is a feedstock for the paper, composite, and textile industries (Bauer et al. Citation2015). Fiber flax is grown as a fiber crop in many countries, such as Holland, Romania, Egypt, France, Russia, and China (Jhala, Hall, and Hall Citation2008). In China, the shortage of raw materials of fiber flax is increasingly prominent, which limited the industrial production. It is urgent to explore effective strategies for increasing the fiber production of flax.
Potassium is one of the three major nutrients in higher plants, and plays an important regulatory role in body electricity, nutrient and metabolite transport, and enzyme activation via acting as a cationic osmolyte (Pramanik et al. Citation2018; Kohlmeier Citation2003). Nowadays, potassium deficiency is common in the world, and about 12.5% cultivated soil in China is deficient in potassium (Gao et al. Citation2000). Application of potassium fertilizer has become a necessary strategy in agricultural production (Bar-Yosef et al. Citation2015). Previous studies have shown that potassium fertilizer can improve the agronomic and yield traits of flax (Yao et al. Citation2016; Shaaban and Nour Citation2012; Deng et al. Citation2014). For examples, the application of K2O increases the technical length, fiber content and fiber yield of 22 flax germplazms (Yao et al. Citation2016). The application of K2SO4 increases the plant height, shoot weight, and capsules weight of flax (Shaaban and Nour Citation2012). K2O increases the fresh weight and stem diameter and improves the lodging resistance of flax (Deng et al. Citation2014). Notably, potassium utilization efficiency was varied in different species and germplazms (Trehan and Singh Citation2013; Wang et al. Citation2013; Zhang et al. Citation2019). The isolation of flax germplazms with high potassium utilization efficiency may alleviate the depletion of potassium resources and improve the quality and yield.
In this study, the effects of potassium fertilizer on the agronomic and yield traits were analyzed in 50 flax germplazms. The potassium utilization efficiency was determined in these germplazms. Our findings may reveal some flax germplazms with high potassium efficiency, which may contribute to the fiber production in agricultural practice.
2. Materials and Methods
2.1. Plant materials and planting
A total of 50 flax germplazms, including 1 germplazm from Holland, 3 germplazms from France and 46 domestic germplazms from China were provided by Flax Sub-center of National Bast Fiber Crops Improvement Center (Harbin, Heilongjiang, China) (). Flax was planted in an experimental field in Shengli village, Yuanda town, Lanxi county, Heilongjiang province, China (126°28′E, 46°27′N). The basic soil fertility included 79.40 mg/kg alkali-hydrolyzed nitrogen, 18.40 mg/kg available phosphorus, 110.20 mg/kg available potassium, 0.17% total nitrogen, 0.07% total phosphorus, 1.73% total potassium, and 21.40 g/kg organic matter (pH7.67). The experiment was designed in a two-factor way (germplazm and potassium fertilizer). Base fertilizer was applied into 8 cm soil layer, and two potassium levels were set, including K0 (0 kg/ha K2SO4) and K50 (50 kg/ha K2SO4). (NH4)2HPO4 was applied at a concentration of 100 kg/ha. The seeds of 50 flax germplazms were then sown at a density of 2000/m2. The experimental field was divided into small plots at 4 m2 area, 2 m length, 10 lines, and 0.2 m line space. Flax was sown at 28 April 2015 and harvested at 3 August 2015 (technical maturing stage)
Table 1. The 50 germplazms of flax (Linum usitatissimum L.) enrolled in this study
3. Detection of agronomic and yield parameters
Plant height and technical length (length from cotyledon trace to base of the first branch) were directly measured using rectilinear scale at technical maturing stage (N = 20 each plot). The dry weight of stem in each plot was quantified as the stem yield. The fiber was extracted by retting in warm water and then weight (50 g fresh stem/plot). The fiber content (%) was calculated as fiber weight/retted stem weight × 100%. The fiber yield was calculated as stem yield × production rate of retted stem (%) × fiber content (%). In addition, the seed yield in each plot was weighted.
4. Detection of potassium utilization efficiency and partial factor productivity
The mature plants at technical maturing stage (N = 30 each plot) were blanched at 105°C for 30 min, dried at 75°C until constant weight, smashed, and filtrated by a sieve mesh (20 mesh). After digestion with H2SO4-H2O2, the content of potassium was measured by a flame photometer. The potassium utilization efficiency was calculated as fiber yield/(aboveground dry weight × potassium content). The partial factor productivity was calculated as fiber yield/unit of K2SO4 applied (Yang et al. Citation2014).
5. Statistical analyses
All experiments were performed in triplicate, and the data were expressed as mean ± standard deviation (SD). Statistical analysis was performed by SPSS version 17.0 (SPSS Inc., Chicago, IL). Comparison between two groups was determined by t test. Cluster analysis of potassium utilization efficiency in different germplazms was performed according to the squared euclidean distance. Correlation analysis was performed by Pearson’s correlation test. A p-value less than 0.05 was considered to be significantly different.
6. Results
6.1. The responses of different germplazms of flax to potassium application in agronomic traits
The effects of potassium application on the agronomic traits of flax, including plant height and technical length were analyzed. As shown in , the plant height was significantly increased by the application of potassium fertilizer (K50) in 42 germplazms (P < 0.05). The increased rate of plant height in five germplazms (D92025-16-9, Diane, 97,175–75-9, Sofie, and Agatha) was more than 5%. The application of potassium fertilizer did not significantly influence the plant height of eight germplazms (90,018-3-1-28, 90,018-6-3-41, 90,018-6-3-15, D97021-10, 98,080-1-3-7, H98003, Heiya-20, and D95009-13-5). In addition, the application of potassium fertilizer (K50) significantly increased the technical length of 41 germplazms (P < 0.05). Among them, 7 germplazms (92,104-9-3, Diane, Yuan-2012-306, s150-5, Sofie, Agatha, and 98,076–15-19) exhibited an increased rate of more than 5%. However, the technical length of nine germplazms (D95027-22-8-2, 98,019–10, 90,018-6-3-15, 98,019-1-6, 98,080-1-3-7, 98,010–23, 90,018-6-3-41, D95009-13-5, and D95027-9-3-1) was not significantly influenced by the application of potassium fertilizer ().
Table 2. The agronomic traits of 50 germplazms of flax (Linum usitatissimum L.)
7. The responses of different germplazms of flax to potassium application in yield traits
The effects of potassium application on the yield traits of flax, including fiber content and yield, stem yield, and seed yield were further analyzed. As shown in , the fiber content and yield were both significantly increased by the application potassium fertilizer (K50) in all 50 germplazms (P < 0.05). The increased rate of fiber content was more than 10% in 13 germplazms, and the increased rate of fiber yield was more than 20% in 7 germplazms (). In addition, the application of potassium fertilizer (K50) significantly increased the stem yield of 46 germplazms (P < 0.05). Four of them (90,018-6-3-15, D95009-13-5, 90,018-3-1-28, and D97021-2) exhibited an increased rate of more than 10%. The application of potassium fertilizer did not significantly influence the stem yield of four germplazms (98,076–15-19, 98,031–12-6-6, Heiya-20, and 92,068–20). Similar with the fiber yield, the seed yield was also significantly increased in all 50 germplazms receiving potassium fertilizer (K50) (P < 0.05). An increased rate of more than 15% was observed in 5 germplazms (S7, D97021-5, 98,010–23, 98,054–40-2-8, and S8) ().
Table 3. The yield traits (fiber content and yield) of 50 germplazms of flax (Linum usitatissimum L.)
Table 4. The yield traits (protostem and seed yield) of 50 germplazms of flax (Linum usitatissimum L.)
8. The potassium utilization efficiency of different germplazms of flax
The potassium utilization efficiency of 50 flax germplazms was determined under K0 and K50. As shown in , the potassium utilization efficiency of 50 flax germplazms was lower under K50 than that under K0. The top five germplazms in potassium utilization efficiency under K0 were Sofie, Yuan-2012-306, Yuan-2012-295, D93005-15-3, and 92,104-9-3, and those under K50 were Sofie, D93005-15-3, Yuan-2012-306, Yuan-2012-295, and 97,175–75-9. Based on the potassium utilization efficiency, 50 germplazms were then classified into 4 categories, including I (low efficiency, K0:17.62–34.38; K50:16.82–29.67), II/III (middle efficiency, K0:36.51–75.34; K50:32.56–58.74), and IV (high efficiency, K0:83.41–91.42; K50:61.38–71.39). There were 20, 9, 16, and 5 germplazms in category I, II, III, and IV under K0, respectively (). There were 19, 13, 12, and 6 germplazms in category I, II, III, and IV under K50, respectively (). Four germplazms with high potassium utilization efficiency were identified under both K0 and K50, including Sofie, Yuan-2012-306, Yuan-2012-295, D93005-15-3.
Table 5. The potassium utilization efficiency of 50 germplazms of flax (Linum usitatissimum L.)
The potassium utilization efficiency was positively associated with the agronomic and yield traits of flax
The correlation between potassium utilization efficiency and the agronomic and yield traits of flax was further analyzed. As shown in , the agronomic traits, including plant height and technical length were positively correlated with the potassium utilization efficiency in flax. Similarly, the yield traits, including fiber content, fiber yield, stem yield, and seed yield were also positively correlated with the potassium utilization efficiency in flax.
Table 6. The correlation between potassium utilization efficiency and agronomic and yield traits of flax (Linum usitatissimum L.)
9. The partial factor productivity of different germplazms of flax
The partial factor productivity of 50 flax germplazms under K50 was analyzed to reflect the overall potassium efficiency. As shown in , the partial factor productivity was diverse in different germplazms. The range of partial factor productivity was 45.5–76.1 kg/kg. The partial factor productivity was greater than 70 kg/kg in 8 germplazms, and was lower than 50 kg/kg in 7 germplazms. The top five germplazms in partial factor productivity were Sofie, 92,104-9-3, y0332-1, D93005-15-3, and 98,019–10.
Table 7. Partial factor productivity of 50 germplazms of flax (Linum usitatissimum L.)
10. Discussion
Potassium is an important nutrient element for plants, which plays a key role in diverse physiological processes, such as energy metabolism, solute transport, photosynthesis, osmoregulation, and phloem transport (Shaaban and Nour Citation2012; Wang and Wu Citation2017). Because potassium deficiency is especially common in the cultivated soil in China, potassium fertilizer has been considered as the first choice to improve the quality and yield of crops (Gao et al. Citation2000; Bar-Yosef et al. Citation2015). Previous studies have demonstrated that potassium fertilizer can improve the agronomic and yield traits of various crops, such as maize (Lu Citation2017), rice (Chen et al. Citation2011), sweet potato (Chen et al. Citation2017), and mung bean (Fooladivanda, Hassanzadehdelouei, and Zarifinia Citation2014). Notably, potassium application also improves the fiber quality, flax rate, fiber yield, and lodging resistance of flax (Yao et al. Citation2016; Shaaban and Nour Citation2012; Deng et al. Citation2014). In this study, the application of potassium fertilizer (K50) increased the fiber content, fiber yield, and seed yield in all germplazms, and increased the plant height, technical length, and stem yield in most germplazms. These results are consistent with previous studies, and illustrated that potassium application can improve the agronomic and yield traits of flax.
Fiber yield is the most important indicator in the production of flax. In this study, the fiber yield was increased by potassium application in all 50 germplazms, indicating that the effect of potassium fertilizer in increasing fiber yield is universal. We also found that the fiber yield was increased more than 20% in 7 germplazms (m0298-4-6, D95009-13-5, s91-2, Heiya-14, 90,018-3-1-28, Yuan-2012-302, and 03134–3). These results showed that these germplazms are high response to potassium application in fiber yield. In agricultural production, more attention should be paid to the potassium application in these germplazms. On the contrary, potassium fertilizer may be redundant in some specific germplazms with low response to potassium application, such as Yuan-2012-295, D92025-16-9, Heiya-20, D93005-15-3, and H98003. The differences of germplasms in response to potassium fertilizer are also reflected in many other agronomic and yield traits of flax. In this study, 5 and 7 germplazms exhibited more than 5% increase in plant height and technical length, respectively. The fiber content and stem yield was increased more than 10% in 13 and 4 germplazms, respectively. The seed yield was increased more than 15% in 5 germplazms. However, the application of potassium fertilizer did not influence the plant length in 7 germplazms, technical length in 9 germplazms, and stem yield in 4 germplazms. Our findings indicated that different germplazms exhibit diverse response to potassium application in different traits. In agricultural production, potassium fertilizer should be applied according to the actual needs of different germplazms.
The potassium utilization efficiency is a key parameter for the evaluation of fertilizer utilization rate (Shin Citation2014). Cultivars with high potassium utilization efficiency are likely to have positive consequences on cost reduction and environmental protection through reducing the application of fertilizer in agriculture. The germplazm-specific differences in potassium utilization efficiency have been reported in a variety of crops, including flax. Yao et al. (Citation2016) screened out four germplasm resources with high potassium utilization efficiency under K0 condition, and two resources with high potassium utilization efficiency under K25 condition (25 kg/ha K2O) (Yao et al. Citation2016). Here, we determined the potassium utilization efficiency of 50 flax germplazms under K0 and K50. We found that the potassium utilization efficiency was lower under K50 than that under K0 in all germplazms. This result suggested that the potassium utilization efficiency can be decreased by potassium application to some degrees. In addition, we classified 50 germplazms into 4 categories according to the potassium utilization efficiency. Four germplazms (Sofie, Yuan-2012-306, Yuan-2012-295, and D93005-15-3) were determined to be high potassium utilization efficiency under both K0 and K50. The high potassium utilization efficiency of these germplazms may be attributed to the advantages in root surface area, potassium translocation, cytosolic potassium maintaining, and substitution of sodium for potassium (Rengel and Damon Citation2008a). The detail physiological mechanisms underlying high potassium utilization efficiency in flax remain to be further studied.
In order to evaluate the agronomic significance of potassium utilization efficiency, the correlations between potassium utilization efficiency and the agronomic and yield traits of flax were further evaluated. The results showed that the potassium utilization efficiency was positively correlated with the plant height, technical length, fiber content, fiber yield, stem yield, and seed yield in flax. These results indicated that the potassium utilization efficiency can reflect the agronomic and yield traits of flax to some degrees. Germplazms with high potassium utilization efficiency are more likely to have a positive consequence on fiber yield. In addition, these agronomic and yield parameters may also be used as target traits for breeding excellent germplazms with high potassium utilization efficiency.
Partial factor productivity is a ratio of yield and fertilization, which reflects the all overall status of fertilizer use. In order to further determine specific flax germplazms with high potassium efficiency, the partial factor productivity under K50 was calculated in this study. The results showed that 8 germplazms have a partial factor productivity of more than 70 kg/kg, while 7 germplazms have a partial factor productivity of less than 50 kg/kg. In addition, Sofie, 92,104-9-3, y0332-1, D93005-15-3, and 98,019–10 were determined to be the top five germplazms in partial factor productivity, presenting a high yield characteristic in agricultural production under potassium application. Notably, high potassium utilization efficiency was also determined in Sofie and D93005-15-3 (IV). These two germplazms with both high potassium utilization efficiency and partial factor productivity exhibit great value in agricultural production. However, some germplazms with high partial factor productivity did not have prominent potassium utilization efficiency. This phenomenon may be attributed to the differences on the potassium uptake and response. Further researches on the internal relationship among potassium utilization, uptake, and response in flax are still needed.
In conclusion, different germplazms of flax exhibited diverse potassium response, potassium utilization efficiency, and partial factor productivity. Sofie and D93005-15-3 with both high partial factor productivity and potassium utilization efficiency were isolated, presenting great value in agricultural production. In addition, Sofie and D93005-15-3 may be valuable experimental materials for evaluating the mechanisms underlying high potassium utilization efficiency and for breeding.
Acknowledgments
This work was supported by the earmarked fund for Modern Agro-industry Technology Research System (Grant No. CARS-16-E04), National Big Data Application Service Demonstration Platform for Food Safety Monitoring, Early Warning and Risk Control (2017YFC1601905), Heilongjiang Province Modern Agricultural Industry Technology Collaborative Innovation System - Hemp (medicinal) Resources Genetic Improvement and Innovative Utilization Collaborative Innovation Post (Grant No. YYM19SQ-24), 13th Five-Year Key Research and Development Program of China (Grant No. 2018YFD0201100). This study was carried out on the Northeast Flax Scientific Observation Experimental Station of Ministry of Agriculture and Flax Branch of the National Bast Fiber Germplasm Improvement Center.
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References
- Bar-Yosef, B., H. Magen, A. E. Johnston, and E. A. Kirkby. 2015. “Potassium Fertilization: Paradox or K Management Dilemma?” Renewable Agriculture and Food Systems 30 (2): 1–5. doi:10.1017/S1742170514000295.
- Bauer, P. J., K. C. Stone, J. Foulk, and R. B. Dodd. 2015. “Irrigation and Cultivar Effect on Flax Fiber and Seed Yield in the Southeast USA.” Industrial Crops and Products 67: 7–10.
- Chen, G. H., Q. M. Guo, Z. L. Lin, Y. X. Huang, and L. M. Yang. 2017. “Effects of Different Application Rate of Potassium Fertilizer on the Yield and Agronomic Traits of Longshu 28.” Crops 3: 91–95.
- Chen, Y., X. H. Li, K. Y. Huang, Y. H. Lu, H. T. Tang, and Y. L. Liao. 2011. “Effects of Potassium Fertilizer Application on Yield and Agronomic Characters in Early Rice.” Crop Research 25 (3): 205–208.
- Deng, X., C. S. Qiu, X. B. Chen, S. H. Long, Y. Guo, D. M. Hao, and Y. F. Wang. 2014. “Influence of Potassium Fertilizer on Lodging Resistance of Flax (Linum Usitatissimum L.).” Plant Fiber Sciences in China 36 (4): 194–198.
- Fooladivanda, Z., M. Hassanzadehdelouei, and N. Zarifinia. 2014. “Effects of Water Stress and Potassium on Quantity Traits of Two Varieties of Mung Bean (Vigna Radiata L.).” Cercetari Agronomice in Moldova 47 (1): 107–114. doi:10.2478/cerce-2014-0011.
- Gao, X. Z., W. Q. Ma, Y. Cui, R. F. Wang, and F. S. Zhang. 2000. “Changes of Soil Nutrient Contents and Input of Nutrients in Arable of China.” Plant Natrition and Fertilizen Science 6 (4): 363–369.
- Jhala, A. J., L. M. Hall, and J. C. Hall. 2008. “Potential Hybridization of Flax with Weedy and Wild Relatives: An Avenue for Movement of Engineered Genes?” Crop Science 48 (3): 825–840. doi:10.2135/cropsci2007.09.0497.
- Kohlmeier, M. 2003. “Potassium.” Nutrient Metabolism 11 (2): 655–660.
- Lu, X. F. 2017. “Effects of Base Potassium Fertilizer on Agronomic Traits and Yield of Ensity-tolerant Summer Maize.” Journal of Anhui Agricultural Sciences 45 (29): 18–22.
- Neetu, N., A. Aggarwal, A. Tanwar, and A. Alpa. 2012. “Influence of Arbuscular Mycorrhizal Fungi and Pseudomonas Fluorescens at Different Superphosphate Levels on Linseed (Linum Usitatissimum L.) Growth Response.” Chilean Journal of Agricultural Research 72 (2): 237–243. doi:10.4067/S0718-58392012000200012.
- Pramanik, P., A. J. Goswami, S. Ghosh, and C. Kalita. 2018. “An Indigenous Strain of Potassium-solubilizing Bacteria Bacillus Pseudomycoides Enhanced Potassium Uptake in Tea Plants by Increasing Potassium Availability in the Mica Waste-treated Soil of North-east India.” Journal of Applied Microbiology 126 (1): 215–222. doi:10.1111/jam.14130.
- Rengel, Z., and P. M. Damon. 2008a. “Crops and Genotypes Differ in Efficiency of Potassium Uptake and Use.” Physiologia Plantarum 133 (4): 624–636. doi:10.1111/j.1399-3054.2008.01079.x.
- Shaaban, S. H. A., and A. E. Nour. 2012. “Effect of Different Potassium Sources on Yield and Nutrient Uptake by Flax (Linum Usitatissimum L.) Grown on Loamy Sand Soil.” Journal of Applied Sciences Research 8: 3.
- Shin, R. 2014. “Strategies for Improving Potassium Use Efficiency in Plants.” Molecules and Cells 37 (8): 575–584. doi:10.14348/molcells.2014.0141.
- Trehan, S. P., and B. P. Singh. 2013. “Nutrient Efficiency of Different Crop Species and Potato Varieties - in Retrospect and Prospect.” Potato Journal 40 (1): 1–21.
- Wang, X. G., C. H. Li, X. Zhao, H. Q. Yu, C. J. Jiang, and M. J. Cao. 2013. “Differences in the Potassium Uptake and Utilization Efficiency of Different Genotype Soybeans under the Low-potassium Stress.” Journal of Shenyang Agricultural University 44 (1): 7–12.
- Wang, Y., and W.-H. Wu. 2017. “Regulation of Potassium Transport and Signaling in Plants.” Current Opinion in Plant Biology 39: 123–128. doi:10.1016/j.pbi.2017.06.006.
- Xie, D. W., Z. G. Dai, Z. M. Yang, Q. Tang, J. Sun, X. Yang, X. X. Song, Y. Lu, D. B. Zhao, and L. G. Zhang. 2018. “Genomic Variations and Association Study of Agronomic Traits in Flax.” BMC Genomics 19 (1): 512. doi:10.1186/s12864-018-4899-z.
- Yang, F. Q., M. W. Du, X. L. Tian, A. Egrinya Eneji, L. S. Duan, and Z. H. Li. 2014. “Plant Growth Regulation Enhanced Potassium Uptake and Use Efficiency in Cotton.” Field Crops Research 163: 109–118. doi:10.1016/j.fcr.2014.03.016.
- Yao, Y. B., G. W. Wu, W. G. Huang, Q. H. Kang, W. D. Jiang, Y. Lu, and S. Q. Zhang. 2016. “Potassium Use Efficiency of Different Flax Genotypes.” Crops 4: 80–85.
- Zhang, Y. H., J. Du, Z. P. Yang, A. L. He, J. Yao, S. M. Huang, B. C. Du, and X. S. Luo. 2019. “Difference of the Application Effect of Potassium in Different High-quality Wheat Varieties.” Tianjin Agricultural Sciences 25 (9): 29–33.