Effect Of Phosphorous Fertilizer On The Yield, Yield Components And Quality Of Linseed

Effect of phosphorous fertilizer on the yield, yield components and quality of linseed (Linum usitatissimum) crop on Nitisols of Lemu-Bilbilo district of Arsi Zone, southeastern Ethiopia

Kulumsa Agricultural Research Center, Ethiopian Institute of Agricultural Research. P.O.Box 489, Kulumsa, Ethiopia.

*Corresponding author E-mail: [anonimizat]

Abstract

Soil fertility depletion coupled with no or improper fertilization is one of the major constraints limiting linseed crop production in Ethiopia among other poor management practices such as lack of proper weed management, poor seed bed preparation, inappropriate seeding rates and methods. Field experiment was conducted on 13 sites, which were found low to medium initial available soil phosphorous levels, during the growing season of 2014 / 2015 on Nitisol of Lemu-Bilbilo district in the southeastern highlands of Ethiopia to study the effect of phosphorous fertilizer application on growth characters, yield and quality of linseed (Kulumsa -1 variety). The experiment comprised of six levels of P fertilizer (0, 5, 10, 15, 20 & 25 kg P ha-1) arranged in randomized complete block design with three replications. The result revealed that P fertilization significantly affected the biomass yield, harvest index and other yield components of linseed. The highest biomass yield of linseed was obtained due to application of the highest level of phosphorous fertilizer, 25 kg P ha-1, which was statistically similar with the lowest level of phosphorous fertilizer, 5 kg P ha-1. All levels of phosphorous fertilizers resulted in statistically superior biomass yields over application of no phosphorous fertilizer. Application of phosphorous fertilizer also brought significant effect on the harvest index of linseed, increased its plant height, number of capsules per plant and kernel size. Application of phosphorous fertilizer; however, did not bring significant grain yield and oil content increase on linseed. Having considered the contribution of P on the biomass yield increment and improvements on other yield components, application of 5 to 10 kg P ha-1 along with 34.5 kg N ha-1 have been recommended for increased production of linseed crop in Nitisols of southeastern highlands of Ethiopia and other similar agroecologies.

Key words: Linseed, phosphorous, Nitisol, yield, yield components and oil content.

INTRODUCTION

Ethiopia is considered as one of the origins and center of diversity for linseed crop (Linum usitatissimum) (Adugna and Adefris, 1995; Seegler, 1983; Harlan, 1969; Vavilov, 1951). The wide ranges of agro-climatic conditions on the country have contributed to its diversification (Adugna, 2000; MoA, 1998). It is widely cultivated in higher elevations of Ethiopia including the Arsi and Bale highlands, where frost is a major threat for other oilseeds such as Noug (Guizotia abyssiniccacass), Ethiopian mustard (Brassica carinata) and Safflower (Carthamus tinctorius L.) (Abebe et al., 2015; Tadesse et al., 2009; Getinet and Nigussie, 1997).

In terms of area coverage and total production, linseed is the third most important oil crop next to sesame (Sesamum indicum) and Noug (Guizotia abyssinica) in the highlands of Ethiopia (CSA, 2014). During 2014/15 cropping season, 810,657 subsistence farmers allocated 82,326 hector of land for linseed production and produced 83.13 tons of linseed with national mean yield of 1.01 t ha-1 (CSA, 2014).

In Ethiopia, linseed has been cultivated since ancient times for two primary purposes, seed and oil use. It is now grown primarily for food and to generate revenue, either in local markets or by export (Negash, 2015; Seegler, 1983).

Linseed oil is very suitable for human consumption and is used as a nutritional supplement. It is well utilized and valued for food in Ethiopia for cooking oil; for making beverage especially during fasting periods; for stew, locally called ‘‘wot’’ substituting pluses; for consumption in soups, with porridges and cooked potatoes, etc (Worku et al. 2012; Vaisey-Genser and Morris 2003; Geleta et al. 2002). Linseed meal and seed oil has many reported health benefits (Ayad et al. 2013). It contains about 36 to 48% oil content, which is an important source of essential fatty acids for human diets and used medically because it has several human health benefits (Berti et al., 2009; Millis, 2002). It is rich in omega-3 fatty acids, especially alpha-linolenic acid that was beneficial for heart disease, inflammatory bowel disease, arthritis, constipation and a variety of other health conditions. It also contains a group of chemicals called lignans that play a significant role in the prevention of cancer (Budwig, 1994). The meal, which remains after oil extraction, is a valuable feed to animals as a protein supplement and is very good manure.

Oilseeds are the second export products next to coffee and already more than 3 million small holders are involved in their production (Wijnands et al., 2007). Besides, linseed possesses great export potential like sesame (Sesamum indicum).

Linseed is also an important precursor crop for cereal, pulse and potato crops in southeastern highlands of Ethiopia (Abebe et al. 2015; Getinet and Nigussie, 1997; Worku et al. 2012; Rowland 1998; Seegeler 1983). It has been used as one of the break crops for maintaining soil fertility for increasing the yields of various crops especially cereals.

Linseed is also grown all over the world for the oil extraction from the seeds and for its fibers. Linseed oil is used for paints, inks, varnish and other wood treatments, soap, linoleum, concrete sealants, putty and pharmaceuticals. The fiber from flax is a widely used and valuable raw material for linen and other textiles, thread/rope and packaging materials; the straw and short fiber for pulp to produce special papers for cigarettes, currency notes and artwork; and the wooden part serves as biomass energy or litter in cattle farming (Akram et al., 2014; Feihu et al., 2013; El-Nagdy et al., 2010; Jhala and Hall 2010; Mackiewicz-Talarczyk et al. 2008; Grant et al., 1999; Rowland 1998; Pasricha et al., 1989).

Despite its diverse use and wider area coverage, linseed production in Ethiopian in general and in Arsi district in particular is characterized by low productivity and poor product quality. No or improper fertilization is one of the major constraints on cultivation of linseed crop in Ethiopia among other poor management practices such as lack of proper weed management, poor seed bed preparation, inappropriate seeding rates and methods (Worku et al. 2012; Belayneh et al. 1990; Seegeler 1983; Abebe et al., 2015; Abebe et al., 2011). For example, among the 82,322 hectare of land covered by linseed in 2014 / 2015, it was only 12,443 hectare (only 15%) of land was fertilized with 556700 kg of natural and organic fertilizers (6.76 kg ha-1) indicating how fertilizer usage is poor (CSA, 2014).

The majority of the soils of the study sites are deficient in available phosphorus for maximum production of oilseed and other field crops (ATA, 2014). Phosphorus is an essential nutrient for crop production due to its improvement of physiological functions (Jiao et al., 2013). Plants need P throughout their life cycle, especially during early growth stages for cell division and during maturity stage for seed formation and increase in seed weight (Lafoand et al., 2008). Phosphorus is an immobile nutrient in the soil and as such, is absorbed from a thin layer of soil around plant roots (Bray, 1954). Due to rapid reactivity of Ρ with soil constituents only a very small portion of applied Ρ is available to and taken up by a crop (Soper and Kalra, 1969; Kalra, 1971; Strong and Soper, 1973, 1974a, a974b). To optimize nutrition and increase linseed productivity per unit area, P must be available to the crop in adequate amounts during the growing season; hence, its fertilization plays great role on crop production (You et al., 2007).

Studies on the effects of phosphorus on linseed yield and yield components are scanty. For this reasons, this study was therefore conducted to determine optimum phosphorous fertilizer rate for increased linseed production.

MATERIALS AND METHODS

Description of the study sites

This study was conducted at Lemu-Bilbilo district of Arsi zone in the southeastern highlands of Ethiopia, which is among the most potential areas for linseed production. The agro-ecology of Lemu-Bilbilo district, which is located 230 km southeast of the capital city of Ethiopia, Addis Ababa, is categorized as warm temperate per humid and warm temperate humid and also cool highland. Its dominant soil type is Eutric Nitisol (Atals of Arsi, 2002). The study was conducted on a total of 13 farmers' fields for one main growing season in 2014 and were located between 07031.596'' to 07037.013'' N latitude and 39013.168'' to 39016.769'' E longitude, at altitude range from 2515 to 3054 m.a.s.l.

Analysis of climatic data collected by Kulumsa Agricultural Research Center at its Bekoji weather station indicated that the study area has extended rainy season, which starts in March and continues to October. The highest rainfall concentrations are in June, July and August. The area receives an annual average rainfall of 1066 mm, while the mean minimum and maximum annual temperature of the area are 9.6 °C and 23.9 °C, respectively. November is the coldest month with a temperature of 8.3 °C while March is the hottest month with a temperature of 25.8 °C.

Do long term-average vs 2014. Write to Olika!

Soil sampling and analysis

In order to select representative experimental sites, a total of 39 soil samples from 0 – 20 cm depth from farmers' fields in the district were collected, where cereals were precursor crops. All samples were air-dried and ground to pass a 2 mm sieve. Soil samples were analyzed for available soil phosphorous using both Olson and Bray II methods at the soil and plant nutrition laboratory of Debrezeit Agricultural Research Center. The available soil phosphorus ranges based on Olson extraction methods considered for categorization were <5 ppm P for low, 5 – 15 ppm P for medium, and >15 ppm P for high (Landon, 1991). According to this categorization, among the 13 fields, 9 were found in medium while the remaining 3 in high initial available phosphorous content. Similarly, the available soil phosphorus ranges based on Bray II extraction methods considered for categorization were <15 ppm P for low, 15 – 50 ppm P for medium and >50 ppm P for high (Landon, 1991). Based on this classification, among the 13 farmers' fields, 3 sites were found with low and the remaining 9 fields with medium initial available phosphorous content.

Experimental set-up and procedure

The experiment included six levels of P fertilizer (0, 5, 10, 15, 20 and 25 kg P ha-1). The recommended amount of nitrogen fertilizer, 34.5 kg N ha-1, was applied to all experimental plots including the control. The experiment was laid out in randomized complete block design with three replications.

The seedbed plowed four times using traditional plough, locally called maresha drawn by ox before planting. All experimental plots at each location and site were planted during the third and fourth weeks of June with a recently released linseed variety, namely Kulumsa -1 at a seed rate of 25 kg ha-1. Seeds were drilled by hand at 0.20 m spacing between rows at the optimum planting time for all sites and locations in plot sizes of 2.6 m by 4 m. The spacing between plots and replications were 0.5 m and 1 m, respectively. The phosphorus fertilizer was applied to all plots according to the treatment arrangement as basal dose at planting in the form of triple super phosphate (TSP) while the recommended rate of N fertilizer (34.5 kg N ha-1) was uniformly applied in splits, half at planting and the remaining half at tillering in the form of urea. Weeding and hoeing were carried out by hand based on research recommendations.

Data collection

Data collected were stand count, tillers per plant, plant height, spike per m-2, number of primary branches per plant, number of capsules per plant, seed and above-ground total biomass yields, hectoliter and thousand seed weights, and oil content of linseed. Height of ten plants in each plot at random was measured at physiological maturity from soil surface to the tip of spike. Total number of capsules of each of ten plants in each plot at random was recorded at physiological maturity.

When the crop was physiologically mature, harvesting was done from a net plot area of 4 m2 (2 m by 2 m) by hand for yield determination. The harvested samples were subjected to air drying to constant moisture content, threshed manually, cleaned and the seed weight recorded. The weighed samples adjusted to 8% moisture content and converted into kg ha-1 for statistical analysis. Harvest index was calculated as percentage ratio of seed yield and biological yield. After threshing, grain samples were randomly collected from each plot and their respective thousand kernel weights were determined using seed counter device in the physiology laboratory of Kulumsa Agricultural Research center. The oil content of linseed was determined using the nuclear magnetic resonance (NMR) analyzer by measuring the liquid proton (H+) content of the seed at the oilseeds and nutrition laboratory of Holeta Agricultural Research Center. The oil content was measured according to the procedure of Röbbelen et al. (1989).

Statistical analysis

Analysis of variance was carried out for each of the measured or computed parameters following the method described by Gomez & Gomez (1984). All yield, yield component and quality data were subjected to analysis of variance using PROC ANOVA of SAS version 9.0 (SAS Institute, 2008) statistical software. The significance of differences among treatment means was compared using least significant difference (LSD test).

RESULTS AND DISCUSSION

Weather

Generally, the total rainfall amount and distribution for 2011 was significantly higher for most of the months compared with 2010 cropping season and long term average (Figure 1). However, considering the main growing season from June to October, except for the month of August, the rainfall amount and pattern for 2011 was very close to the long term average. Unusually, very high and low rainfall amounts recorded for 2011 in the months of August and October, respectively and resulted in alternate floods and acute shortage of moisture, which consequently affected the performance of the crop. The rainfall amounts recorded were considerably lower in 2010 than in 2011 and long term average; which had negative impact on the performance of the crop. Acute deficiency of moisture in October and afterwards critically affected grain filling and resulted in lower yield of malting barley.

Figure 1. Monthly total rainfall for 2010, 2011 crop growing seasons and 35 years monthly average rainfall around Lemu-Bilbilo district.

Plant growth, yield, yield components and oil content

Generally, the analysis of variance over sites indicated that phosphorous fertilization highly significantly (p < 0.001) affected some of the variables measured for linseed crop including plant height, number of capsules plant-1, kernel weight and biomass yields (table 1). It also significantly (p < 0.05) affected the harvest index of linseed. The result further indicated that location was also a large source of variation for all of the variables measured. There were significant interaction effects of phosphorous fertilizer rates and sites (table 1). However, application of various levels of phosphorous fertilizer did not bring significant seed yield, oil content and other yield components increase on linseed crop at Lemu-Bilbilo district of Arsi zone (table 1).

Table 1. ANOVA table for the effects of phosphorous fertilizer rate, location and their interaction on the yield, yield components and oil content of linseed across sites in 2014.

Note: ns, * and *** = Not significant at 0.05 and significant at 0.05 and 0.001 probability levels, respectively.

The result of this study revealed that application of phosphorous fertilizer did not bring significant seed yield increase on linseed at Lemu-Bilbilo district of Arsi zone. The highest seed yield (2095 kg ha-1) was recorded from the application of highest rate, 25 kg P ha-1; however, it was statistically equivalent with application of the lowest rate, 5 kg P ha-1 (2034 kg ha-1). This indicates that linseed was found to be a poor extractor of fertilizer Ρ from a soil. This inefficient utilization of applied Ρ by linseed crop was shown to be related to the inability of its root system to expand and proliferate within the fertilizer reaction zone (Soper, 1969; Kalra, 1971) or to absorb phosphorus efficiently from high concentrations (strong, 1973). In the study, linseed crop appeared to continue to take up Ρ throughout the growing period. Uptake of Ρ by linseed crop was slower than that by wheat and rape, but that uptake continued later than 60 days after seeding (Racz et. al., 1965).

The lowest seed yield of linseed (1976 kg ha-1) was obtained from the application of no phosphorous fertilizer; however, it was statistically equivalent with all levels of phosphorous except for the highest level, 25 kg P ha-1. Compared to the mean seed yield of linseed in the country, which was only 1010 kg ha-1, the seed yield obtained in this current study was so high and encouraging (table 2). The most important agronomic packages attributed for high seed yields of linseed were improved land and crop managements. The usual practice of production in the study area was sowing of linseed after a single plough. Besides, there has been a long standing tradition of not weeding linseed due to unproved thought of lodging. Contrary to the farmers’ practices of the study area, all of the experimental plots were ploughed and weeded four and two times, respectively per cropping season. Hence, improved land and crop management practices along with proper nitrogen fertilizer have been contributed more than the application of phosphorous fertilizer to the highest seed yield of linseed in study area.

A review on the mineral nutrition of linseed (Hocking et al., 1993) indicated that there was little information on the response of seed yield of linseed to P supply. Numerous other field, greenhouse and laboratory studies including L.D. Bailey and C.A. Grant (1989), Ukrainetz, (1963), Soper et al (1963), Racz (1969), Ridley (1974), Grant et al (1999) and farmers’ experience have shown that seed yield of linseed did not generally respond significantly to the applications of phosphorous even in soils low in available phosphorus.)

Application of the highest level of phosphorous fertilizer, 25 kg P ha-1, resulted in the corresponding highest biomass yield of linseed (7413 kg ha-1), which was statistically very different from application of no phosphorous; it gave a biomass yield advantage of 835 kg ha-1. The result, however, revealed that there were no statistically significant biomass yield differences among the five different levels of phosphorous fertilizers. Application of the lowest level of phosphorous fertilizer, 5 kg P ha-1, gave a biomass yield of 7141 kg ha-1, which was statistically superior over application of no phosphorous fertilizer (6578 Kg ha-1). Compared to application of no phosphorous fertilizer, application of 5 kg P ha-1 brought a biomass yield advantage of 563 kg (8.6%) (table 2). The increased biomass yield of linseed due to application of various levels of phosphorous fertilizers has been documented in the works of Grant et al (1999), Salah M. Emam and Mohamed D. H. Dewdar (2015), Grant et al. (1999) and Khan et al. (2000) and Hocking et al (1993).

The result further revealed that application of various levels of phosphorous fertilizer brought significant effect on the harvest index of linseed (table 2). Akram et al (2014) reported that mean performances of harvest index of linseed significantly differed with various levels of phosphorus fertilizers. The highest harvest index (30.56 %) was attained at the application of no phosphorous fertilizer. Generally, harvest index got decreased as the level of phosphorous fertilizer increased indicating an inverse relationship. The relatively lower grain and higher biomass yields at higher levels of phosphorous fertilizer attributed to the inverse relationship. L.D. Bailey and C.A. Grant (1989) reported that at high rates of P, the harvest index decreased from 20 to 17 and 13 when 15 kg ha-1 or greater quantities of Ρ were applied.

The application of P significantly (P<0.001) enhanced plant height of linseed (table 2). Salah M. Emam and Mohamed D. H. Dewdar (2015) also got similar results. The tallest plant height of 101 cm was recorded at the highest application rate, 25 kg P ha-1; though it was not significantly different from the lowest rate of 5 kg P ha-1. The shortest plant height of 98 cm was recorded at P rate of 0 kg ha-1. Generally, the result showed that as the level of P increased, plant height got enhanced, which shows a direct relationship. Mengel and Kirkby (1987) reported that phosphorus deficiency in small grains is usually expressed as stunted growth.

The result further indicated that application of phosphorous fertilizer very significantly increased the number of capsules per linseed plant. All levels of P resulted in very significantly higher number of capsules per linseed plant. The highest and lowest numbers of capsules per linseed plant were recorded from the applications of 10 and 0 kg P ha-1, respectively. Application of 10 kg P ha-1 resulted in an increase of 3 capsules per single plant when compared to application of no P. The result; however, indicated that there were no statistically significant differences among the five levels of phosphorous fertilizer (table 2). Salah et al (2015) and Pande et al. (1970) reported a significant variation due to treatment of linseed plant by phosphorous fertilizer applications for the number of capsules plant-1.

The result of this study further indicated that application of phosphorous fertilizer seemed to increase the kernel size of linseed plant. Application of the highest level of P, 25 kg ha-1, brought the highest kernel weight of linseed (6.2 mg), which was statistically superior over all other levels. Generally, the result reveled that as the level of P increased, the kernel weight of linseed increased, which showed a direct relationship (table 2).

The result of this study also showed that application of various levels of P did not significantly affect the oil content of linseed. Hocking et al (1993) reported that phosphorus supply had little effect on seed oil concentration. However, the result implied that there was an increasing trend of oil content as the level of P increased. In fact, application of the highest rate of P, 25 kg ha-1, was superior compared to application of no P at all.

Table 2. Table of means for the effect of phosphorous fertilizer on yield and yield component of linseed at Lemu-Bilbilo district of Arsi Zone in 2014.

CONCLUSIONS

The result of our current study showed that application of phosphorous fertilizer did not bring significant grain yield increase in linseed. However, application of 5 kg P ha-1 gave statistically higher biomass yield, harvest index and number of pods per linseed plant when compared to application of no fertilizer. Having considered the contribution of P on the biomass yield increment and improvements in other yield components, application of 5 to 10 kg P ha-1 along with 34.5 kg N ha-1 have been recommended for increased production of linseed in Nitisols of southeastern highlands of Ethiopia and other similar agroecologies. Production of linseed without application of P fertilizer will deprive of the soil in the long run; hence, application of 5 to 10 kg P ha-1 helps for maintenance of soil fertility and increasing quality of linseed.

The result of this study further revealed that good land and crop managements practices have been found more important than the application of phosphorous fertilizer for increasing the yield of linseed on Nitisols of southeastern highlands of Ethiopia.

Since nutrients uptake by plants is dependent up on balanced fertilization, further study using balanced fertilization has been recommended to be conducted in order to further increase the yield and quality linseed crop. Besides, the effect of P on the oil content and quality needs to be investigated at higher phosphorous fertilizer levels.

It is needed to investigate more thoroughly the effect of phosphate fertilizer rates on flax production.

ACKNOWLEDGMENTS

The authors would like to thank Ethiopian Institute of Agricultural Research for the provision of funding for the execution of this research activity. The authors are thankful for Kulumsa Agricultural Research Center for the provision of logistics. Due to their unreserved efforts from planting across harvesting to proper data management, all members of Land and Water Resources Research team of Kulumsa Agricultural Research Center are greatly acknowledged. The management and laboratory technician of Holeta and Debrezeit Agricultural Research Centers are also warmly acknowledged for the provision of analytical services.

REFERENCES

Abebe D, Birhane A, Workiye T, Adane C (2011). Prevalence of Weeds in Linseed Fields and Farmers Cultural Practices in Producing Linseed. In: Terefa G, Wakjira A and Gorfu D (eds.). Oilseeds: Engine for Economic Development.

Abebe Delesa and Adane Choferie. 2015. Response of Linseed (Linum usitatissimum L.) to seed rates and seeding methods in Southeastern highlands of Ethiopia. Journal of Biology, Agriculture and Healthcare. Vol.5, No.13

Adugna W, Adefris TW (1995). Agronomic performance of linseed regenerants at two locations in Ethiopia. In: Sebil. Proceedings of the 7th Annual Conference of the Crop Science Society of Ethiopia (CSSE), 27-28 April 1995, Addis Ababa, Ethiopia, pp.9-21.

Akram Othman Esmail, Haifa Sediq Yasin and Bahar Jalal Mahmood. 2014. Effect of levels of phosphorus and iron on growth, yield and quality of flax. Journal of Agriculture and Veterinary Science. Volume 7, Issue 5, pp 07-11

ATA. 2014. Draft Soil Fertility Maps of Ethiopia. EthioSIS Project, Addis Ababa, Ethiopia.

Atlas of Arsi Zone. 2002. Regional State of Oromia: Arsi Zone Planning and Economic Development Office and Rural Development & Rural Development Project Arsi and Bale.

Ayad A, Merzouk H, Hamed YB, Merzouk SA, Gresti J, Narce M(2013) Beneficial effects of dietary olive and linseed oils on serum and tissue lipids and redox status in the aging obese rat. J Nat Prod Plant Resour 3:61–71

Belayneh H, Alemayehu N, Alemawu G (1990) Progress in linseed on-station and on-farm research in Ethiopia. In: Omran A (ed) Oil Crops: Proceedings of the three meetings held at Pantnagar and Hydrabad, India, 4–17 January 1989, pp 220–227

Berti, M.; Susana, F.; Rosemarie, W and Felicitas, H. (2009) .Flaxseed response to N, P, K fertilization in South Central Chile. Chilean Journal of Agricultural research 69(2):145-153.

Bray, R.H. 1954. A nutrient mobility concept of soil-plant relationships. Soil Sci. 78:9-22.

Budwig J (1994). Linseed and Linseed Oil. An internet record from http://www.numark

Central Statistical Agency. 20154. Report on Area and production of major crops for 2013 / 2014 (private Peasant Holdings, Meher Season). Statistical Bulletin No. 532. Addis Ababa, Ethiopia.

El-Nagdy, G.A., Nassar, Dalia M. A., El-Kady, Eman A., El-Yamanee, Gelan S.A. 2010. Response of flax plant (Linumusitatissimum L.) to treatments with mineral and bio-fertilizers from nitrogen and phosphorus. J. of Amer. Sci,. 6(10): 207-217.

Feihu Liu, Fei Li, Guanghui Du and Fu Xiao. 2013. Balanced Fertilization Improves Fiber Yield and Quality of Winter Flax (Linum usitatissimum L.) American Journal of Plant Sciences, 4, 291-296. http://dx.doi.org/10.4236/ajps.

Geleta M, Asfaw Z, Bekele E, Teshome A (2002) Edible oil crops and their integration with the major cereals in North Shewa and South Welo, Central Highlands of Ethiopia: an ethnobotanical perspective. Hereditas 137:29–40

Getinet Alemaw, and Negusei Alemayehu. (1997). Highland Oil Crops: A Three Decade Research Experience in Ethiopia. Research report No. 30. Institute of Agricultural Research, Addis Abeba, Ethiopia.

Gomez, K.A. and A.A. Gomez. 1984. Statistical Procedures for Agricultural Research. 2nd Ed. John Willey & Sons, Inc. New

Grant CA, Dribnenki JCP, Bailey LD (1999). A comparison of the yield response of solin (cv. Linola 947) and flax (cvs. McGregor and Vimy) to application of nitrogen, phosphorus, and Provide (Penicillium bilaji). Can. J. Plant Sci., 79: 527-533

Harlan JR (1969) Ethiopia: a center of diversity. Econ Bot 23:309–314 harmacist.com/hn/Supp/Flaxseed.htm.

Hocking P.J. and A. Pinkerton. 1993. Phosphorus nutrition of linseed (Linum usitatissimum L. ) as affected by nitrogen supply: effects on vegetative development and yield components. Field Crops Research, 32 pp 101-114.

Jhala AJ, HallLM(2010) Flax (Linum usitatissimum L.): current uses and future applications. Aust J Basic Appl Sci 4:4304–4312

Kalra, Y.P. 1971. Different behavior of crop species in phosphate absorption. Plant and Soil 34:535-539.

Kalra, Y.P. 1971. Different behavior of crop species in phosphate absorption. Plant and Soil 34:535-539.

Lafond GP, Irvine B, Johnston AM, May WE, McAndrew DW, Shirtliffe SJ, Stevenson FC (2008). Impact of agronomic factors on seed yield formation and quality in flax. Can. J. Plant Sci., 88: 485-500.

Landon, J.R. (Ed.), 1991. Booker tropical soil manual: A Handbook for Soil Survey and Agricultural Land Evaluation in the Tropics and Subtropics., New York. 474p.

Mackiewicz-Talarczyk M, Barriga-Bedoya J, Mankowski J Pniewska I (2008) Global flax market situation. ID#97, International Conference on Flax and Other Bast Plants (ISBN #978-0-9809664-0-4), pp 408-412

Mengel K, EA Kirkby (1987). Principles of Plant Nutrition. (4th Ed.). International potash institute, Bern, Switzerland

Millis P (2002). Nutrition, cooking and health: let’s eat flax. Wholeness and Wellness J. Saskatchewan, 8: 8-9. Online available: http://www.wholife.com/issues/8 3/02 article.html.

MoA (1998). Agro-Ecological Zones of Ethiopia, Addis Ababa, Ethiopia.

Negash Worku, J. S. Heslop-Harrison and Wakjira Adugna. 2015. Diversity in 198 Ethiopian linseed (Linum usitatissimum) accessions based on morphological characterization and seed oil characteristics. Genetic Resources and Crop Evolution. DOI 10.1007/s10722-014-0207-1

Pande RC, Singh M, Agrawal SK, Khan RA (1970). Effect of different levels of irrigation, nitrogen and phosphorus on growth, yield and quality of linseed (Linum usitatissimum Linn.). Indian J. Agron., 15:

Pasricha, A.S. Azad and K.L. Ahuja. 1989. Response of linseed (Linum usitatissimum L.) to fertilizer nitrogen, phosphorus and sulphur, and their effect on the removal of soil sulphur. Soil Use and Management. Aulakh M.S., N.S. Volume 5, Issue 4, pp 194–198. DOI: 10.1111/j.1475-2743.1989.tb00783.x

Racz, G.J. 1969. Effect of fertilizers on flax – 1968. 13th Ann. Manitoba Soil Sci. Meeting, Univ. of Man., Winnipeg, Man. pp. 177-179.

Racz, G.J., M.D. Webber, R.J. Soper and R.J. Hedlin. 1965. Phosphorus and nitrogen utilization by rape, flax and wheat. Agron. J. 57:335-337.

Ridley, A.O. and S. Tayakepisuthe. 1974. Residual effects of fertilizer phosphorus as measured by crop yields, phosphorus uptake and soil analysis. Can. J. Soil Sci. 54:265-272.

Robbelen G, Downey RK, Ashri A (1989). Oil Crops of the World, McGrawHill, New York, pp.157-183

Rowland GG (1998) Growing flax: Production, management and diagnostic guide. Flax Council of Canada and Saskatchewan Flax Development Commission

Salah M. Emam and Mohamed D. H. Dewdar. 2015. Seeding rates and phosphorus source effects on straw, seed and oil yields of flax (Linum usitatissimum L.) grown in newly-reclaimed soils. International Journal of current Microbiological and applied sciences. Vol 4 No. 3 pp: 334-343.

Seegler CJP (1983). Oil plants in Ethiopia, their economy and agriculture. M. H. Thijssen, Zewde B, Beshir A, de Boef WS (2008). (eds) farmers seed and varieties: supporting informal seed supply in Ethiopia. Wagningen, Wagenningen International.

Soper, R.J. and G.J. Racz. 1963. Effect of fertilizer on various crops in Manitoba. 7th Ann. Manitoba Soil Sci. Meeting, Univ. of Man., Winnipeg, Man. pp. 93-100.

Soper, R.J. and Y.P. Kalra. 1969. Effect of mode of application and source of fertilizer on phosphorus utilization by buckwheat, rape, oats and flax. Can. J. Soil Sci. 49:319-326.

Strong, W.M. and R.J. Soper. 1973. Utilization of pelleted phosphorus by flax, wheat, rape and buckwheat from a calcareous soil. Agron. J. 65:18-21.

Strong, W.M. and R.J. Soper. 1974. Phosphorus utilization by flax, wheat, rape and buckwheat from a band or pellet-like application. I. Reaction zone root proliferation. Agron. J. 65:597-601.

Strong, W.M. and R.J. Soper. 1974. Phosphorus utilization by flax, wheat, rape and buckwheat from band or pellet-likeapplication. II. Influence of reaction zone phosphorus concentration and soil phosphorus supply. Agron. J. 65:601-605.

Tadesse,T., Singh, H., and Weyessa, B. 2009. Correlation and path coefficient analysis among seed yield traits and oil content in Ethiopian linseed Germplasm. Int. J. Sustain. Crop Prod. 4(4):08-16.

Ukrainetz, H. 1963. Fertilizer placement for flax. Progress Report, 1954-1958. Experimental Farm, Scott, Sask. Information Division, Can. Agric., Ottawa. p. 12.

Vaisey-Genser M, Morris DH (2003) History of the cultivation and uses of flaxseed. In: Muir AD, Westcott ND (eds) Flax: the genus Linum. CRC Press, London, pp 1–21

Vavilov NI (1951) The origin, variation, immunity and breeding of cultivated plants. Chron Bot 13:20–43

Worku N, Zemede A, Haileselassie Y (2012) Linseed (Linum usitatissimum) ethnobotany and its cultivation status in Ethiopia. Int J Agric Appl Sci 4:48–57

You J. Cynthia, A, G. and Loraine, D, B (2007). Growth and nutrient response of flax and durum wheat to phosphorus and zinc fertilizers. Canadian Journal of Plant Science, 87(3): 461-470.