The effects of varied plant density and nitrogen fertilization on quantity and quality yield of Camelina sativa L .

R E G U L A R A R T I C L E *Corresponding author: Wacław Jarecki, Department of Crop Production, Faculty of Biology and Agriculture, University of Rzeszow, Zelwerowicza 4, 35-601 Rzeszów, Poland, E-mail: waclaw.jarecki@wp.pl Received: 22 March 2017; Revised: 01 January 2018; Accepted: 07 January 2018; Published Online: 12 January 2018 Czarnik, et al.: The effects of varied plant density and nitrogen Emir. J. Food Agric ● Vol 29 ● Issue 12 ● 2017 989 fertilization modifies evaluation parameters as well as quantity and quality yield of Camelina sativa [L.] Crantz. MATERIALS AND METHODS Crop management The research was carried out in the years 2012-2014 in Przecław (The Experimental Station of Cultivar Assessment), south-eastern Poland (50°11’N, 21°29’E). It was a two-factorial experiment (split-plot) conducted in three replications. The experimental factors were: (A) plant density (200, 300, 400 pcs. m-2) and (B) nitrogen fertilization (50, 100 kg∙ha-1). The breeder of summer Camelina sativa cv. ‘Omega’ was Poznań University of Life Sciences, Poland. The experiment was set up on alluvial soils created from silt loam. The soil was classified in valuation class IIIb of the good wheat complex with pH slightly acid or inert in the range from 6.38 to 7.11. Soil samples were collected by a sampling stick to a depth of 0–60 cm. The content of available forms of phosphorus was high or very high, potassium – average or high, and magnesium – very high (Table 1). Soil analysis was carried out at the Chemical and Agricultural Station in Rzeszów, with generally accepted methods in Polish Stanards. The data concerning weather conditions came from the Experimental Station of Cultivar Assessment in Przecław. From March to July in 2012 was the period in which the lowest total precipitation appeared. In May and June 2013 as well as in May and July 2014 high level of rainfalls was recorded and it exceeded considerably the long-term average (Table 2). During the plant growth higher air temperatures were noticed in 2012, and the lowest in 2014 (Table 3). Irrigation was not used in field trials. The seeds of false flax were received from the Department of Genetics and Plant Breeding in Poznań University of Life Sciences. Oat was the forecrop of false flax in every year of research. The area of a plot was 7.5 m2, for harvesting 5 m2. The row spacing amounted to 15 cm, and sowing depth 1.5 cm. Seed dressed material was sown in three periods: 4.04.2012, 22.04.2013 and 24.03.2014. The sowing date was optimal for the area of the research. Under the autumn ploughing granular triple superphosphate (40 P2O5 kg∙ha -1) and potash salt (60 K2O kg∙ha -1) were used. Nitrogen fertilization (34% ammonium saltpeter) was applied in varied doses and terms (Table 4). The herbicide Butisan SC 400 (2.5 dm3 ∙ ha-1) were applied after sowing. The secondary weed infestation was removed manually. The diseases and pests were not combated. Plant density per 1 m2 was calculated after emergence and before harvest. At the technical maturity stage, 20 representative plants were collected from each plot for determine yield components: a number of silicles per plant, a number of seeds per silicle and the 1000 seeds weight. Data regarding thousand seeds weight were recorded by counting randomly selected 1000 seeds from each plot and weighed with sensitive electronic balance. BBCH scale for false flax was given by Martinelli and Galasso (2011). The harvest was conducted on the following dates: 18.07.2012, 29.07.2013 and 21.07.2014. The seed yield obtained from the plots was converted into yield per 1 ha, assuming a humidity of 15%. The seed yield was adjusted for missing plants collected for biometric measurements. Total protein yield and crude fat were calculated from seed yield and percentage content of these components in seeds. Experimental design and treatments The content of total protein and crude fat in the seeds was determined with the NIRS method in near infrared on the apparatus Spectrometer FT NIR MPA Bruker (Billerica, USA). Macroand microelements were developed at the University of Rzeszow (The Laboratory of the Faculty of Table 1: Chemical characteristics of experimental soil Measurement 2012 2013 2014 Soil acidity (1 mol L KCl) 6.38 7.11 7.00 Humus (%) 1.92 1.84 1.72 Nmin 0–60 cm (kg∙ha -1) 66.4 60.8 56.8 (mg kg)* P 71.1 96.6 79.8 K 153.6 175.9 160.2 Mg 72.4 66.9 60.9


INTRODUCTION
Camelina sativa (L.) Crantz was cultivated in Poland for centuries, but now occupies a small area in Poland, due to the higher prevalence of yielding rape.There are two cultivated forms such as winter and summer, but the winter forms yielding higher than summer (Toncea, 2014;Mosio-Mosiewski et al., 2015).Martinelli and Galasso (2011) and Zanetti et al. (2017) claim that there are multiple environmental and agrotechnical benefits of camelina for eg.: small climatic and soil requirements.The seeds of camelina can be used universally, eg.: as feed (Steppa et al., 2017;Wang et al. 2017) and derived oil from them as food (Vollmann et al., 2007;Mińkowski et al., 2010) as well as technical oil, including biofuel (Karcauskiene et al., 2014;Mohammed et al., 2017).The nutritional value of oil is mainly due to a high content of unsaturated fatty acids, particularly n-3 (omega-3) fatty acids and multiple use values (Zubr and Matthäus 2002;Zubr, 2003a).It is appropriate to conduct further researches on the improvement of genetic traits of camelina (Vollmann et al., 2007) as well as the optimization agricultural technology.Gesch et al. (2017) as well as Koncius and Karcauskiene (2010) pay attention to the need of usage optimum sowing rate, which affects on plant habit and seed yield.An important agricultural treatment is also a mineral fertilization.Like other cultivated plants in the family Brassicaceae (Brassicaceae Burnett) false flax strongly respond to nitrogen fertilization (Solis et al., 2013;Jiang and Caldwell, 2016;Waraich et al., 2017).
The aim of this study was to estimate a reaction of the summer form of camelina to varied plant density and nitrogen fertilization.In the research hypothesis it was assumed that the varied plant density and nitrogen fertilization modifies evaluation parameters as well as quantity and quality yield of Camelina sativa [L.] Crantz.

Crop management
The research was carried out in the years 2012-2014 in Przecław (The Experimental Station of Cultivar Assessment), south-eastern Poland (50°11'N, 21°29'E).It was a two-factorial experiment (split-plot) conducted in three replications.The experimental factors were: (A) plant density (200, 300, 400 pcs.m -2 ) and (B) nitrogen fertilization (50, 100 kg•ha -1 ).The breeder of summer Camelina sativa cv.'Omega' was Poznań University of Life Sciences, Poland.The experiment was set up on alluvial soils created from silt loam.The soil was classified in valuation class IIIb of the good wheat complex with pH slightly acid or inert in the range from 6.38 to 7.11.Soil samples were collected by a sampling stick to a depth of 0-60 cm.The content of available forms of phosphorus was high or very high, potassium -average or high, and magnesium -very high (Table 1).Soil analysis was carried out at the Chemical and Agricultural Station in Rzeszów, with generally accepted methods in Polish Stanards.
The data concerning weather conditions came from the Experimental Station of Cultivar Assessment in Przecław.From March to July in 2012 was the period in which the lowest total precipitation appeared.In May and June 2013 as well as in May and July 2014 high level of rainfalls was recorded and it exceeded considerably the long-term average (Table 2).During the plant growth higher air temperatures were noticed in 2012, and the lowest in 2014 (Table 3).Irrigation was not used in field trials.
The seeds of false flax were received from the Department of Genetics and Plant Breeding in Poznań University of Life Sciences.Oat was the forecrop of false flax in every year of research.The area of a plot was 7.5 m 2 , for harvesting 5 m 2 .The row spacing amounted to 15 cm, and sowing depth 1.5 cm.Seed dressed material was sown in three periods: 4.04.2012, 22.04.2013 and 24.03.2014.The sowing date was optimal for the area of the research.Under the autumn ploughing granular triple superphosphate (40 P 2 O 5 kg•ha -1 ) and potash salt (60 K 2 O kg•ha -1 ) were used.Nitrogen fertilization (34% ammonium saltpeter) was applied in varied doses and terms (Table 4).
The herbicide Butisan SC 400 (2.5 dm 3 • ha -1 ) were applied after sowing.The secondary weed infestation was removed manually.The diseases and pests were not combated.Plant density per 1 m 2 was calculated after emergence and before harvest.At the technical maturity stage, 20 representative plants were collected from each plot for determine yield components: a number of silicles per plant, a number of seeds per silicle and the 1000 seeds weight.Data regarding thousand seeds weight were recorded by counting randomly selected 1000 seeds from each plot and weighed with sensitive electronic balance.BBCH scale for false flax was given by Martinelli and Galasso (2011).
The harvest was conducted on the following dates: 18. 07.2012, 29.07.2013 and 21.07.2014.The seed yield obtained from the plots was converted into yield per 1 ha, assuming a humidity of 15%.The seed yield was adjusted for missing plants collected for biometric measurements.Total protein yield and crude fat were calculated from seed yield and percentage content of these components in seeds.

Experimental design and treatments
The content of total protein and crude fat in the seeds was determined with the NIRS method in near infrared on the apparatus Spectrometer FT NIR MPA Bruker (Billerica, USA).Macro-and microelements were developed at the University of Rzeszow (The Laboratory of the Faculty of  Biology and Agriculture).To determine macroelements and microelements, plant samples were mineralized in a mixture of concentrated acids HNO 3 :HClO 4 :HS 2 O 4 in the ratio 20:5:1, in an open system, in the heating block Tecator.
In obtained mineralisates the contents of Ca, K, Mg, Zn, Mn, Cu, Fe were determined with atomic absorption spectroscopy (AAS), using the apparatus Hitachi Z-2000 (Tokyo, Japan), whereas P was determined with colorimetry, using the spectrophotometer UV-VIS Shimadzu (Kyoto, Japan), with the vanadium-molybdenum method.Analysis of fatty acids was performed using gas chromatograph Shimadzu's GC-17A (Kyoto, Japan) according to standards: PN-EN ISO 12966-4:2015-07.

Statistical analysis
The results were subjected to statistical analysis of variance.
Calculations were made in the Statistica 8.0 programme (StatSoft, Tulsa, USA).Significance of differences between the means was indicated with the use of Tukey test, with a significance level of α =0.05.

Yield and yield components
Increasing the density of sowing resulted in a significant increase in plant density after emergence and before harvest (Table 5).In 2012, the plant density was the lowest impacted by low rainfall during the germination and plant emergence.Gesch et al. (2017) recommend that sowing should be not less than 3 kg•ha -1 .
Nitrogen fertilization did not modify plant density.While Koncius and Karcauskiene (2010) obtained the diversity of the camelina plant density per 1m 2 with variable doses of NPK.
In own study, an increase the density of sowing significantly reduced the number of silicles per plant.The increase in nitrogen fertilization significantly increased the number of silicles per plant, an average of 9.1 psc.It confirmed the diversity of characteristics in years of the research.
Sowing 200 seeds m -2 compared to the sowing of 300 and 400 seeds m -2 contributed to the significant reduction in the number of seeds in silicle.The use of higher doses of nitrogen resulted in a significant decrease in the number of seeds in silicle.Increasing the amount of sowing seeds from 200 to 400 pcs.m -2 reduced the 1000 seeds weight (Table 5).The resulting difference was significant and amounted to an average of 0.18 g.
The application of sowing seeds of 300 and 400 pcs.m -2 resulted in a significant increase in yield compared to 200 pcs.m -2 .Seed yield was significantly higher with higher doses of nitrogen and the resulting difference as compared to the lower dose was 0.11 t•ha -1 .Between 2013 and 2014 the seed yield was significantly higher in relation to 2012.2014) considered that plant density in spring should be over 350 pcs.m -2 , which guarantees a high yield of seeds.The effect of higher doses of nitrogen on the growth of the yield was confirmed in previous studies by other authors (Jiang et al., 2013;Jiang et al., 2014;Sintim et al., 2015).For the optimal dose of nitrogen for false flax Jiang et al. (2013) reported 120 to 160 kg•ha -1 .Afshar et. al. (2016) considered that higher doses than 45 kg•ha -1 are not effective in growing camelina.Wysocki et al. (2013) said that the camelina requires about 12 kg of kg•ha -1 per 100 kg of expected seed yield.Toncea (2014) reported that yield of camelina also depends on weather conditions and varieties.

Chemical composition of seeds
The increase in seeding rate to 400 pcs.m -2 resulted in reduction of the content in seed protein, and increased fat content and fat yield (Table 6).The higher dose of nitrogen in comparison to the lower contributed to an increase in seed content of protein and protein yield, and reduced crude fat content in seeds.In 2012 it was reported the highest total protein content in the seeds, and the lowest crude fat and fat yield.
Many authors (Jiang et al., 2013;Jiang et al., 2014;Sintim et al., 2015) confirmed that higher doses of nitrogen increase the protein content and lower fat content in the seeds of false flax.It has been shown that nitrogen fertilization increases protein yield (Jiang et al., 2013) and fat yield (Jiang et al., 2014).Zubr (2003b) as well as Zubr and Matthäus (2002) conclude that the differences in the quality of false flax seeds are mainly due to the varietal characteristics and conditions of climate and soil in which the plants were grown.
Applied the highest seed rate (400 psc.m -2 ) resulted in an increase in the content of the seeds K and Mg.In turn, the plating 200 psc.m -2 increased the content in the seeds of Mn and Zn a decrease and of Fe.Increasing the nitrogen fertilization with 50 kg•ha -1 to 100 kg•ha -1 increased the Fe and Zn content in seeds.In the study period content of Fe and Zn in seeds was varied (Table 7).The average macro-and micronutrient content in the seeds of false flax was different from given by Zubr (2010).
Varied sowing rates had no significant effect on the percentage of fatty acids.The higher dose of nitrogen in comparison to the lower increased the proportion of linoleic acid and linolenic acid and reduced oleic.Otherwise, it was proved that the contribution of certain fatty acids in the period was variable (Table 8).Jiang et al. (2013Jiang et al. ( , 2014) ) showed that higher doses of nitrogen increase the percentage of polyunsaturated fatty acids, and reduce the percentage of monounsaturated fatty acids.Wang et al. (2017) reported that the camelina was rich in C 18:4,n-3 and in C 20 FA.

CONCLUSIONS
The agricultural practices, ie.: the sowing rates and nitrogen fertilization diversified yield components, yield and chemical composition in seeds of summer Camelina sativa L.
The increase in the sowing density significantly developed plant density, but reduced the number of silicles per plant.
Sowing 400 seeds • m -2 resulted in a decrease of 1000 seeds compared to 200 seeds •m -2 .In turn, 200 seeds • m -2 significantly decreased the number of seeds in the silicle, seed yield and content of Fe in the seeds.However, it increased the content of seeds in Mn and Zn.It was found that the sowing of 400 seeds • m -2 reduced the protein content in the seeds, K and Mg, and increased the fat yield and crude fat content in the seeds.The higher nitrogen dose (100 kg • ha -1 ) significantly increased the number of silicles per plant, total protein content, Fe, Zn in seeds, seed yield, protein yield and percentage of linoleic and linolenic acids.The lower nitrogen dose (50 kg • ha -1 ) increased the number of seeds in the silicle, the fat content in the seeds and the percentage of oleic acid.
The studies proved that spring summer Camelina sativa L. reacts preferentially at the higher dose of nitrogen (100 kg • ha -1 ) and a higher sowing rates (300 -400 pcs.m -2 ).

Table 1 : Chemical characteristics of experimental soil
* -available forms

Table 5 : Plant density, yield components and seed yield (average of years) Experience factor Number of plants Number of silicles per plant Number of seeds per silicle 1000 seeds weight (g) Seed yield (t•ha -1 ) sowing density (psc.m-2 ) nitrogen fertilization (N kg•ha -1 ) after emergence (pcs.m -2 ) before harvest (pcs.m -2 )
a Note.The mean marked by the same letter do not differ significantly Czarnik, et al.: The effects of varied plant density and nitrogen

Table 6 : Seed content and yield total protein and crude fat (average of years)
aNote.The mean marked by the same letter do not differ significantly

Table 8 : Content of fatty acid (%) in seeds (average of years) Fatty acids Sowing density (psc. m -2 ) Nitrogen fertilization (N kg•ha -1 )
Note.The mean marked by the same letter do not differ significantly