Abstract: The effects of Ammonium Sulfate (AS), Foliar Nutrition (FN) and their interaction on the growth and chemical constituents of Nigella sativa L. (N. sativa) were investigated. The highest plant growth characters [Plant Height (PH) (cm), Leaf Number (LN) (plant–1), Branch Number (BN) (plant–1), Capsule Number (CN) (plant–1), Herb Dry Weight (HDW) (plant–1) and Seed Yield (SY) (g plant–1)] were obtained in the 3 g pot–1 of AS+FN treatment with values of 27.7, 30; 46.9, 38.7; 9.3, 8.9; 13.2, 11.3; 45.8, 43.6; 4.6, 5.1 during the first and second seasons, respectively. The highest accumulations of Fixed Oil (FO), Total Carbohydrates (TC), Soluble Sugars (SS), Crude Protein (CP), Nitrogen (N), Phosphorous (P) and potassium (K) contents were recorded at the highest AS level (3 g pot–1)+FN with the values of 27.7 and 27.5%; 36.3 and 27.3%; 16.3 and 8.7%; 27.8 and 25.1%; 2.7, 3.5%; 0.1%; 0.6, 0.8% during the first and second seasons, respectively.
INTRODUCTION
Mineral nutrients applied basally or through foliar application enhance the plant productivity and could be used as tool to ameliorate the quality of herbal medicines. Ammonium Sulfate (AS) is the main source of inorganic nitrogen (N) fertilizer (Fageria, 2003). It has about 21% of N and also contains about 24% sulfur (S). The N is the single most important limiting nutrient for crop growth and hence ample N availability acts as a key contributing factor towards wholesome improvement in agriculture production (Singh, 2009). It is considered to be of prime importance as it plays several important roles in metabolic and regulatory processes in plants. The AS treatments increased herb and essential oil yields and changed the level of secondary metabolites in dragonhead plants. Highest oil yields were obtained with AS at 200 kg N ha–1 (Aziz et al., 2010). The most effective dose of AS was 200 kg ha–1, resulting in a positive increase in vegetative growth characters and content of essential oil, fixed oil, total carbohydrates, soluble sugars, protein and nutrients (NPK) of anise, coriander and sweet fennel plants (Khalid, 2013).
The soils of Egypt are generally sandy with low Cation Exchange Capacity (CEC) values. This means that the soil does not have the ability to hold on to many of the nutrients allowing them to be easily leached out of the rooting zone during irrigation. Foliar feeding is a technique of feeding plants by applying liquid fertilizer directly to their leaves (George, 2003). Foliar Nutrition (FN) is an effective method for correcting soil deficiencies and overcoming the soils inability to transfer nutrients to the plant under moisture conditions. On the other hand soil application of nutrient on calcareous soils is less efficient as these nutrients remain inaccessible to plant roots due to the higher soil pH (Rashid and Ryan, 2004; Ali et al., 2008). However, an alternative approach under such circumstances is FN of nutrients (Rab and Haq, 2012) primarily for two reasons. First, it eliminates the effects of soil pH on the availability of these nutrients (Ali, 2012). Second, it is more effective and less costly (Ali et al., 2007). Kandeel (1991) reported that using FN at 2000 mg L–1 had a significant effect on plant height, fresh weight, dry weight, fruit yield and essential oil content of parsley (Petroselinum crispum Mill). The FN had a significant effect on anise, coriander and sweet fennel plants which positively affect on growth and chemical constituents (essential oils, fixed oil, total carbohydrates, soluble sugars, protein and nutrient content) of these three plants grow under arid regions in Egypt (Khalid, 2012).
Black seed N. sativa plant belongs to the family Ranunculaceae and is most extensively investigated for therapeutic purposes (Aggarwal et al., 2008). Pharmacological studies on N. sativa found analgesic, bronchodilator, hypolipidemic, anti-tumor, diuretic, immunopotentiator, hypotensive, calcium antagonist, antidiabetic, histamine release inhibitor, antioxidant, hepatoprotective, anthelmintic, antifungal, antibacterial, anticancer and anti-inflammatory activities (Al-Logmani and Zari, 2011).
In this study, the possible effects of AS, FN and their interaction on the growth and chemical constituents of N. sativa, an important medicinal plant were investigated.
MATERIALS AND METHODS
Experiments were carried out in a greenhouse at the National Research Centre (NRC), Cairo, Egypt, during, 2013/2014 and 2014/2015 Nigella sativa L. seeds were obtained from the Ministry of Agriculture, Egypt. Uniform seeds were sown into plastic pots (30 cm diameter and 50 cm height) during the first week of November 2013 and 2014 the pots were transferred to a greenhouse adjusted to 24-18°C, 90-60% R.H., day-night and light intensity ~3700 μmol m–2 sec–1. Each pot was filled with 10 kg of air-dried soil. Physical and chemical properties of the soil used in this study were determined according to Jackson (1973) and Cottenie et al. (1982) and are presented in Table 1. Three weeks after sowing, the seedlings were thinned to three plants per pot. After 45 days from sowing date plants were divided into two main groups. The first group was subjected to different levels of AS (0, 1, 2 and 3 g pot–1) (21% N). The second group was subjected to the same levels of AS but FN was added (1 g L–1). Foliar nutrition was solution commercially known as agronal, which consists of the following minerals: N (120 mg L–1), P2O5 (40 mg L–1), K2O (40 mg L–1), Mg (2 mg L–1), S (2 mg L–1), Fe (1200 mg L–1), Zn (1200 mg L–1), Mn (1000 mg L–1), Cu (500 mg L–1), Ni (1 mg L–1) and Co (1 mg L–1).
Harvesting: At the end of fruiting stage (215 day from sowing), the plants were harvested. Vegetative growth characters measurements [Plant Height (PH) (cm), Leaf Number (LN) (plant–1), Branch Number (BN) (plant–1), Capsule Number (CN) (plant–1), Herb Dry Weight (HDW) (plant–1) and Seed Yield (SY) (g plant–1)] were recorded.
| Table 1: | Physical and chemical properties of soil |
Fixed Oil (FO) isolation: For the FO extraction, 50 g of seeds were crushed to coarse powered and extracted with petroleum ether (40-60°C) in a Soxhlet apparatus (AOAC., 1970).
Total Carbohydrates (TC) and Soluble Sugars (SS) determinations: The TC and SS contents were determined from plant material (young leaves) collected from each treatment. The method of DuBois et al. (1956) was used.
Nutrients (NPK) and Crude Protein (CP) determination: The N, CP, P and K (in the leaves) of both seasons of each treatment were determined using the methods described by AOAC (1970).
Statistical analysis: In this experiment, two factors were considered: AS (0, 1, 2 and 3 g pot–1) and FN (1 g L–1). For each treatment there were 4 replicates, each of which had 8 pots; in each pot 3 individual plants were planted. The experimental design followed a Complete Random Block Design (CRBD). According to Snedecor and Cochran (1990). The averages of data from each season were statistically analyzed using 2-way analysis of variance (ANOVA-2). Significant values determined according to p-values (p<0.05; significant, p<0.01; moderate significant and p<0.001; highly significant). The applications of that technique were according to the STAT-ITCF program (Foucart, 1982).
RESULTS
Effect of AS, FN and their interaction on growth characters: Plant growth characters such as PH, LN, BN, CN, HDW and SY of N. sativa were affected by changes in AS, FN and their interaction treatments (Table 2). Thus the various growth characters in general increased under the various AS levels+FN compared AS treatments. The highest plant growth characters were obtained in the 3 g pot–1 of AS+FN treatment with values of 27.7, 30; 46.9, 38.7; 9.3, 8.9; 13.2, 11.3; 45.8, 43.6; 4.6, 5.1 cm during the first and second seasons, respectively. The lowest plant growth characters were obtained in the control treatment with the values of 15.8, 19.1 cm; 17.8, 25.9 plant–1; 5.8, 4.3 plant–1; 2.4, 3.1 plant–1; 22, 22.1 g plant–1; 3.3, 3.6 g plant–1 during the first and second seasons, respectively. The increases in plant height and leaf number were highly significant for AS, FN and their interaction. The increases in branch number were highly significant for AS and FN while it were significant for the interaction between AS and FN. The increases in capsule number were highly significant for AS and FN (during the first season) but insignificant for FN (during the second season) and the interaction between AS and FN. The increases in herb dry weight were highly significant for AS and FN but insignificant for the interaction between AS and FN. The increases in seed yield were highly significant for AS but insignificant for FN and the interaction between AS and FN.
| Table 2: | Effect of AS, FN and their interaction on growth characters |
| *p<0.05 according to F-values of the 2-way analysis of variance (ANOVA-2), ***p<0.001 according to F -values of the 2-way analysis of variance (ANOVA-2) | |
| Table 3: | Effect of AS, FN and their interaction on biochemical constituents |
| *p<0.05 according to F-values of the 2-way analysis of variance (ANOVA-2), ***p<0.001 according to F -values of the 2-way analysis of variance (ANOVA-2) | |
Effect of AS, FN and their interaction FO: The FO content increased at all various AS levels+FN compared AS treatments (Table 3). The highest accumulations of FO content were recorded at the highest AS level (3 g pot–1)+FN with the values of 27.7 and 27.5% during first and second seasons. The lowest FO contents were obtained in control treatment with the values of 17.1 and 17% during first and second seasons. The increases in FO contents were highly significant for AS, FN and their interaction.
Effect of AS, FN and their interaction on TC and SS: The TC and SS content increased with AS, FN and the AS×FN interaction in both seasons (Table 3). However, the highest TC and SS content resulted from 3 g pot–1 of AS+FN, 108.6, 80.8%; 143.3, 123.1% higher than the control for the first and second seasons, respectively. The increases in TC were highly significant for AS and FN while it were significant for AS×FN during the first season and insignificant during the second season. The increases in SS were highly significant for AS, FN and AS×FN except during the second season for FN (were insignificant).
Effect of AS, FN and their interaction on CP: The CP contents of N. sativa were affected by changes in AS, FN and their interaction treatments (Table 3). Thus the CP in general increased under the various As levels+FN compared AS treatments. The highest CP contents were obtained in the 3 g pot–1 of AS+FN treatment with values of 27.8 and 25.1% in both seasons. The lowest CP contents were obtained in the control treatment with the values of 16.9 and 21.2% during the first and second seasons, respectively. The increases in CP contents were highly significant for AS and FN, while it was insignificant for AS×FN interaction.
Effect of AS, FN and their interaction on NPK: The accumulation of NPK in N. sativa leaves during the first and second seasons was promoted by applying various levels of AS, FN and AS+FN (Table 3). The NPK increase by adding AS with FN compared with AS alone. Control treatment resulted in the lowest nutrient accumulation on NPK while the highest mineral content was observed in the control treatment with 3 g pot–1+FN. The lowest values of NPK contents were 2.7, 3.5%; 0.1%; 0.6, 0.8%, while the highest values were 3.7, 3.9%; 0.4%; 1.7, 2.2% during the first and second seasons. The increases in N content were significant for AS, highly significant for FN but it were significant for AS+FN during the first season while it were insignificant during the second season for AS, FN, AS+FN. The increases in P content were insignificant. The increases in K content were highly significant for AS and FN and insignificant for AS+FN.
DISCUSSION
The positive effect of AS on N. sativa may be due to it the main source of inorganic N fertilizer. Nitrogen plays an important role in synthesis of the plant constituents through the action of different enzymes activities and protein synthesis (Jones et al., 1991) that reflected in the increase in growth parameters of plants such as anise, coriander and sweet fennel plants. Also, these results are in accordance with those obtained by Khalid (1996, 2001) on some Apiaceae and N. sativa plants; Ashraf et al. (2006) on cumin, Akbarinia et al. (2007) on coriander and Hellal et al. (2011) on dill (Anethum graveolens L.) all of whom reported that N fertilizer treatments were superior to the control treatment and significantly improved the vegetative growth characters of family Apiaceae. The results of fixed oil were similar to those of Khalid (1996) on some Apiacea plants; Khalid (2001) and Ashraf et al. (2006) on N. sativa and Akbarinia et al. (2007) on coriander (Coriandrum sativum L.). The increase in total carbohydrate and soluble sugars was significant. These results may be due to the increase in chlorophyll content and consequently, photosynthesis efficiency induced by N. So it showed that total carbohydrates and soluble sugars contents increased with application of N (Jones et al., 1991). The results of protein content may be due to the influence of N on the ribosome structure and the biosynthesis of some hormones (gibberellines, auxins and cytokinins) involved in protein synthesis (Jones et al., 1991; El-Wahab and Mohamed, 2007). The increase in the essential minerals according to the N treatments may be due to the increase in the dry matter of plant materials (El-Wahab and Mohamed, 2007).
On the other hand, increasing N rates by ammonium sulfate fertilizers have a tendency to decrease soil pH, this means that the fertilizers increase soil acidity which causing an increase in the availability of other nutrients for N. sativa plants (Fageria et al., 2010).
The results of FN treatments were agreement with some previous investigators. Kandeel (1991) reported that using FN application at 2000 mg L–1 had a significant effect on plant height, fresh weight, dry weight, fruit yield and oil content of parsley (Petroselinum crispum Mill). The FN had a significant effect on anise, coriander and sweet fennel plants which positively affect growth and chemical constituents of these three plants grown under arid regions in Egypt (Khalid, 2012).
CONCLUSION
It may be concluded that the various growth characters and chemical constituents of N. sativa were increased under the various AS levels+FN compared AS treatments. The highest values of growth characters and chemical constituents obtained from the treatment of 3 g Pot–1 of AS+FN.