Abstract: A greenhouse experiment was carried out to investigate the effects of chemical fertilizer include N and P (chemical fertilizing system), animal manure (organic fertilizing system), combined use of manure and chemical fertilizer (integrated fertilizing system) and Barvar Phosphate Biofertilizer (BPB) on seed yield, mucilage and seed P content of Isabgol at the Agriculture Research Center, University of Tehran, Karaj, Iran. The results showed that BPB inoculation significantly increased seed yield, mucilage and seed P content. The results also showed that seed and mucilage yields were significantly affected by fertilizing systems. Animal manure and combined use of manure and chemical fertilizer resulted in a greater seed yield, mucilage yield, mucilage percentage, swelling factor and P content than sole application of chemical fertilizer. The most seed (4.58 g pot-1) and mucilage yield (0.876 g pot-1) were observed in integrated use of animal manure and chemical fertilizers with BPB inoculation.
INTRODUCTION
Plants known as medicinal are rich in secondary metabolites and are potentially useful to produce natural drugs. The biosynthesis of the secondary metabolites, although controlled genetically, is affected strongly by environmental factors (Singh et al., 2003). Plantago ovata is an important herb that has been used in health care for many centuries in South Asia, whereas it is now widely used for its medicinal properties all over the world. Isabgol an Ayurvedic herb is found in Iran, India and Afghanistan. It is also native to the surrounding of Mediterranean region including Northern Africa, Europe and Pakistan. This plant can be grown under a wide range of agro-climatic conditions, but it is mostly confined to the arid areas of the world due to its low water requirements (Zahoor et al., 2004). Isabgol has been used as medicine since ancient times, but it has been cultivated as a medicinal plant only in recent decades (Yadav et al., 2002). The seed of Isabgol contains mucilage, fatty oil; large quantities of albuminous compound, a pharmacological inactive glycoside, namely Aucubin (C13 H19 O8 H2O) and a pentose sugar (Zahoor et al., 2004). The seed husk has the property of absorbing and retaining water which accounts for its application in controlling diarrhea. It is diuretic, alleviates kidney and bladder complaints, gonorrhea, arthritis and hemorrhoids (Zargari, 1994).
To provide economically sustainable yields, nutritional elements must be present in sufficient quantities in soil and they must be available for root uptake. Nitrogen and phosphorous are essential nutrients for plant growth and development (Blaise et al., 2005). The extensive uses of chemical fertilizers in Iran have increased crops productivity but did not promote the quality of medicinal and aromatic plants which are the most important characteristics for export. To increase the crops quality especially medicinal and aromatic plants, organic fertilization is more acceptable than chemical fertilizers (Karla, 2003). Organic farming can guarantee the quality of medicinal plants and that is why the medicinal plants consumers prefer to use the organic plant components (Griffe et al., 2003). Organic fertilizers are excellent sources of nutrients for crop production and improving physical and chemical properties of soil (Ewulo, 2005). It has been shown that addition of organic matter improved soil properties such as aggregation, water-holding capacity, hydraulic conductivity, bulk density, the degree of compaction, fertility and its resistance to water and wind erosion (Franzluebbers, 2002). Application of organic matter positively affects the growth and development of plant roots and shoots (Ghosh et al., 2004). Yadav et al. (2002) reported that integrated use of chemical fertilizer and animal manure increased the seed and mucilage yields of Isabgol. Singh et al. (2003) reported that the total dry matter, seed and mucilage yields of Isabgol can be increased with application of chemical and organic fertilizers. Also Parihar and Singh (1995) and Patel and Sadaria (1996) reported that chemical fertilizers can increase seed and mucilage yields, spike length and spike number per plant of Isabgol.
Microorganisms are important attributes in agriculture to promote the circulation of plant nutrients and reduce the need for chemical fertilizers (Rodríguez et al., 1999). Biofertilizers are organic products containing living cells of different types of microorganisms, which have the ability to convert nutritionally important elements from unavailable to available form through biological processes (Vessey, 2003). In recent years, biofertilizers have emerged as an important component of the integrated nutrient supply system and hold a great promise to improve crop yields through environmentally better nutrient supplies. P-solubilizing bacteria may be important for plant nutrition by increasing P uptake and play a significant role as PGPR in the biofertilization system. Trials with rhizosphere-associated plant growth-promoting P-solubilizing Bacillus species indicated that yield increases in sugar beet (Akmakc et al., 2006), wheat (De Freitas, 2000), sugar beet and barley (Ahin et al., 2004). Accordingly, great attention should be paid to studies and application of new combinations of phosphate-solubilizing bacteria. Barvar Phosphate Biofertilizer (BPB) is a new biofertilizer including P-solubilizing bacterial strains which has been produced by Green Bio-tech Co. in University of Tehran.
The primary objective of this study was to evaluate the efficiency of novel P-solubilizing bacterial strains isolated from Iran’s soils (Barvar Phosphate Biofertilizer) and different soil fertilizing systems (chemical, organic and integrated) on the promotion of plant growth, mucilage percentage, seed swelling factor and seed P content of Isabgol. The secondary goal was to find out whether sufficient and high quality yields of the Isabgol crop could be produced by solely biologic fertilizer application in organic farming system in Iran conditions.
MATERIALS AND METHODS
This experiment was conducted in glasshouse of College of Agronomy and Animal
Sciences, University of Tehran, Karaj, Iran, during Autumn, 2006. Seeds used
in this experiment were obtained from the Jahad Medicinal Plant Research Center,
Ministry of Jahad of Agriculture in Iran. The original seed were collected from
the Khorasan province in northeastern part of the country. The Effects of different
fertilizing treatments were investigated in pots. The treatments were arranged
in factorial based on a completely randomized block design with three replications.
The effect of Barvar phosphate biofertilizer (inoculated and without inoculation)
was tested with two levels of chemical fertilizer including N and P (chemical
fertilizing systems), two levels of animal manure (organic fertilizing systems),
two levels of combined use of manure and chemical fertilizers (integrated fertilizing
systems) (Table 1). Intact soil volume for this experiment
was collected from Dolat-Abad farm in Karaj (Table 2). The
soil was air-dried and grounded to pass through a 4 mm sieve. About 2.5 kg of
soil was allocated to each pot and thoroughly mixed with different fertilizing
treatments (Table 2). Fifteen viable seeds were sown in each
plastic pot (20 cm diameter and 30 cm high) at a constant temperature (20±4°C).
Ten days after seed germination, the emerged seedlings were thinned to 5 plants
in each pot. The pots were watered on a daily basis to maintain the moisture
at approximately 60% water holding capacity of the soil. The crop was harvested
after 101 days. The sources of N, P and animal manure were urea, super phosphate
and dairy cow manure (Table 3), respectively. The first half
of the nitrogen fertilizer was applied before sowing and the remainder at spike
formation stage. The total P and dairy cow manure were applied before sowing.
The biofertilizer (BPB) used for this experiment was supplied by Green Bio-tech
Co.; which consisted of two kinds of phosphate solubilizing bacteria (Pseudomonas
putida (strain p13) and Bacillus lentus (strain p5). The bacteria
strains were originally isolated from farm soils in Iran. For seed inoculation
according to instructions, 50 g of Isabgol seed was inoculated with one gr BPB
before being immediately planted.
| Table 1: | Soil fertilizing system treatments details |
| Table 2: | Some of soil characteristics |
| Table 3: | Some dairy cow manure characteristics |
Measurements: Biological yield was determined by cutting and harvesting the whole plants per each pot. Samples were oven-dried at 75°C for 72 h for Dry Matter (DM) determination. Mucilage percentage, swelling factor according to Ebrahimzadeh et al. (1998) method, seed phosphorous content according to Olsen and Sommers (1990) method, seed and mucilage yield per pot, were measured after harvesting.
Data analysis: Two-way General Liner Model (GLM) ANOVA was used (SAS Institute Inc., 1989) for soil fertilizing systems and Barvar phosphate biofertilizer effects on yield, yield components and seed P content of Isabgol. Duncan at p<0.05 tested the significance of differences among treatment means.
RESULTS AND DISCUSSION
Results showed that all traits investigated in this study were significantly affected by fertilizing systems (Table 4). Barvar Phosphate Biofertilizer (BPB) inoculation significantly affected all traits except mucilage percentage and swelling factor. The interaction of these treatments significantly affected seed yield and seed phosphorous content (Table 5). Application of all kind of fertilizers significantly increased biological, seed and mucilage yield compared to control (Table 4). Among fertilizing systems, chemical system had less effect on above mentioned traits compared to other fertilizing systems. Integrated system could increase more seed and mucilage yield compared to organic system, so the highest seed yield (4.58 g pot-1) was observed in N20P10 + 20 t ha-1 manure which were inoculated with BPB (Table 5). This could be attributed to the fact that animal manure can improve physical and chemical properties of soil (Blaise et al., 2005).
Many studies have shown that the fertilizing power of animal manure is due
to its content of stabilized organic matter and due to the amount of nutritive
elements contained therein (Ewulo, 2005; Ghosh et al., 2004). Yadav et
al. (2002) also reported that biological, seed and mucilage yields of Isabgol
significantly increased by using integrated application of chemical and organic
fertilizers, which can increase the available nutrition for plant roots and
improve photosynthesis process. Singh et al. (2003) reported that biological,
seed and mucilage yield of Isabgol could be increased with application of animal
manure and chemical fertilizers in organic and integrated systems due to improving
of physical and chemical soil properties. The highest mucilage yield (0.876
g pot-1) was obtained in N20P10 + 20 t ha-1
manure treatment, which was not significantly different from 20 t ha-1
manure (Table 4). Sing et al. (1996) reported total
dry matter, seed and mucilage yields of Isabgol could be increased with application
of chemical and organic fertilizers. Also Parihar et al. (1995) and Patel
et al. (1996) reported that chemical fertilizers can increase seed and
mucilage yields, spike length and spike number per each plant of Isabgol. Inoculation
of BPB along with all fertilizing systems increased seed yield and this effect
was more identical in low levels of fertilizer application. This result could
be attributed less activity of phosphate solubilizing bacteria in rich phosphorous
soils (Table 5). Phosphate solubilizing bacteria can increase
yield of spinach (Urashima et al., 2003), sugar beet and barley (Ahin
et al., 2004). Inoculation with BPB had no significant effect on swelling
factor and mucilage percentage (Table 4). On the other hand
all of the fertilizing systems increased seed mucilage percentage and the highest
mucilage percentage (19.67%) were obtained in 20 t ha-1 manure which
did not have a significant difference with N20P10 + 20
t ha-1 manure treatment (Table 4). Chemical fertilizing
system compared to organic and integrated systems did significantly affect swelling
factor, however, the most swelling (10.10 mm) appeared in 20 t ha-1
manure which did not have a significant difference with N20P10
+ 20 t ha-1 manure (Table 4). Correlation analysis
showed that there is high and significant relation between mucilage percentage
and swelling factor. Swelling factor will increase as mucilage percent increases.
As a result, higher seed mucilage percentage can make higher swelling factor
(data not shown). Ebrahim Zadeh et al. (1998) also reported the high
correlation between mucilage percentage and swelling factor in Isabgol.
| Table 4: | Mean comparison effects of Barvar Phosphate Biofertilizer (BPB) and fertilizing systems on yield, mucilage, swelling factor and seed P concentration. With Duncan test at the 5% level of probability |
| Means with the same letter(s) in columns are not significantly different at p<0.05; BPB = Barvar Phosphate Biofertilizer N50P30 = 50 kg ha-1 nitrogen and 30 kg ha-1 phosphorous, M = Dairy cow manure | |
| Table 5: | Mean comparison of interaction effects of Barvar Phosphate Biofertilizer (BPB) and fertilizing systems on seed yield and seed P concentration. With Duncan test at the 5% level of probability |
| Means with the same letter(s) in columns are not significantly different at p<0.05; BPB = Barvar phosphate biofertilizer N50P30 = 50 kg ha-1 nitrogen and 30 kg ha-1 phosphorous, M = Dairy cow manure | |
The results of this experiment showed that seed P content increased by BPB inoculation compared to non-inoculated plants (Table 4). This could be caused by more phosphorous availability resulted from phosphate solubilizing bacteria activities. These results support the findings of Urashima et al. (2003) on spinach and Ahin et al. (2004) on sugar beet and barley and Poberejskaya and Egamberdiyeva (2003) on cotton. The highest seed phosphorous content was observed in N20P10 + 20 t ha-1 manure treatment along with BPB (Table 5). This could be due to improving soil available P and physical and chemical properties of soil. Application of animal manure on farmlands, recycle nutrients from manure to soil for plant growth and add organic matter to improve soil structure and water holding capacity. On the other hand, phosphate solubilizing bacteria can increase soil available P by hydrolysis of P from inorganic and organic compounds due to acidification of soil or secretion of phosphatase enzymes (Akmakc et al., 2006).
CONCLUSIONS
Results of this study indicated that organic and integrated fertilizing systems could produce the most mucilage percentage, swelling factor, seed phosphorous content and biological, seed and mucilage yields and provide with more profits compared to chemical fertilizing system. Barvar Phosphate Biofertilizer (BPB) increased seed and mucilage yields of Isabgol. This biofertilizer could be used as a suitable fertilizer along with organic and chemical fertilizers to achieve the maximum benefits. To prevent the environmental pollution from extensive application of chemical fertilizers, the biological fertilizers could be recommended to insure the public health and a sustainable agriculture.