INTRODUCTION:

Nowadays, farmers are using inorganic fertilizers to provide nutrients to the soil. Inorganic fertilizer use has also significantly supported global population growth — it has been estimated that almost half the people on the Earth are currently fed as a result of synthetic nitrogen fertilizer use. Fertilizers typically provide, in varying proportions, sixmacro nutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S) and eight micronutrients: boron (B),chlorine (Cl), copper (Cu), iron (Fe),manganese (Mn), molybdenum (Mo),zinc (Zn) and nickel (Ni).

Organic fertilizers are substances that arederived from the remains or by products of organisms which contain the essential nutrients for plant growth. Chemical fertilizers, in effect, “kill” the soil while organic fertilizers improve and sustain the soil. Chemical fertilizers provide short term results yet, in the long term, damage the soil, ground water and our health. Whereas biofertilizers have the following special features:

· Provide slow-release plant nutrients

· Avert “run-off” and retain moisture in soil

· Improve the condition of the soil

· Prevent plant disease

· Increase nutritional content in plants and

· Produce tastier fruits and vegetables.

Bio-fertilizers add nutrients through the natural processes of nitrogen fixation solubilize phosphorus and stimulate plant growth through the synthesis of growth-promoting substances. Bio-fertilizers can be expected to reduce the use of chemical fertilizers and pesticides. In order to bring out new view, we are trying to prepare fertilizer from seaweeds which are easy to cultivate and abundantin all the coasts. Since they are rich in micro and macro nutrients required for plant growth they can be used as bio fertilizer. This paper reviews and justifies the effect of seaweed is advantageously made use of to stimulate germination and growth, thereby increasing the yield and resistance ability of many crops and. Seaweeds represent an alternative to conventional chemical fertilizers. Commercial use of liquid extracts, obtained from seaweeds is successfully used as foliar sprays for several crops. In the present investigation, an attempt has been made to study the influence of SLF prepared from Dictyotadichotomaon the growth and yield characteristics of Okra (Abelmoschusesculantus)

CHEMICAL VS. ORGANIC FERTILIZER:

Many organic materials serve as both fertilizers and soil conditioners—they feed both soils and plants. This is one of the most important differences between a chemical approach and an organic approach toward soil care and fertilizing. Soluble chemical fertilizers contain mineral salts that plant roots can absorb quickly. However, these salts do not provide a food source for soil microorganisms and earthworms, and will even repel earthworms because they acidify the soil. Over time, soils treated only with synthetic chemical fertilizers lose organic matter and the all-important living organisms that help to build a quality soil. As soil structure declines and water-holding capacity diminishes, more and more of the chemical fertilizer applied will leach through the soil. In turn, it will take ever-increasing amounts of chemicals to stimulate plant growth. When you use organic fertilizers, you avoid throwing your soil into this kind of crisis condition. The manufacturing process of most chemical fertilizers depends on nonrenewable resources, such as coal and natural gas. Others are made by treating rock minerals with acids to make them more soluble.

FEATURES OF BIO FERTILIZER:

Biofertilizers have the following special features:

· Provide slow-release plant nutrients

· Avert “run-off” and retain moisture in soil

· Improve the condition of the soil

· Prevent plant disease

· Increase nutritional content in plants and

· Produce tastier fruits and vegetables.

Essential Nutrients required for plant growth:
Nutrient elements obtained from atmosphere through photosynthesis: Hydrogen, Carbon, Oxygen
Nutrient elements obtained from the soil: Nitrogen, Phosphorus, Potassium, Sulfur, Magnesium, Calcium, Iron, Boron, Manganese, Zinc, Molybdenum. Copper

Nutrients present in seaweeds: Macro-Minerals Found in Seaweeds:

Calcium (C), Chloride (Cl), Iron (Fe), Magnesium (Mg), Phosphorus (P), Potassium (K), Sodium (Na), Sulphur (S)

Seaweed Micro-Nutrients:

Boron (B), Chromium (Cr), Cobalt (Co), Copper (Cu), Fluorine (F), Germanium (Gr), Iodine (I), Manganese (Mn), Molybdenum (Mo), Nickel (Ni), Selenium (Se), Silicon (Si), Sulphur (S), Tin (Sn), Tungsten (W), Vanadium (V), Zinc (Zn).

DETERMINATION OF NUTRIENTS IN SEAWEEDS:

Determination of Nitrogen:

Nitrogen was determined by the micro-Kjeldahl method reported by Pearson (1976) and crude protein content was subsequently calculated by multiplying the nitrogen content by a factor of 6.25.

Determination of carbohydrate:

Carbohydrate content was estimated by subtracting the sum of the weights of protein, fibre, ether extract and ash from the total dry matter and reported as nitrogen-free extractives (NFE by difference). The protein solubility was examined from pH 1~12 by the method of Adeyeye et al. (1994). All determinations were in triplicates.

Determination of Phosphorus:

Dried seaweed samples [1-2g] were weighed accurately, ashed with magnesium nitrate, the ash was dissolved in 2NH and SO, (101n1) and the solution made up to 50ml.The amount of phosphorus present in this solution was determined by measuring the density of the colour produced on complexing with vanadomolybdate reagent on a Corning Model 252 colorimeter using 430,470 and 490nm filters.

Determination of Sulphur:

Accurately weighed sample (1-2g) of seaweed was treated with concentrated nitric acid (10ml) and the mixture was allowed to stand overnight at room temperature. The resulting mixture was evaporated to dryness and the residue was ashed in a muffle furnace at 450° C. The ash was dissolved in a minimum volume of 25%nitric acid and the solution made up to 50ml in volumetric flask. A known volume of this solution was treated with an excess of standard barium chloride. The un-reacted barium chloride was determined by titration with standard EDTA. The amount of sulphate was estimated by the method of difference.

Determination of Iron:

The test solution was prepared in 0.6M HC1 as described above. The amount of iron present in the test solution was determined by measuring the density of the colour produced by the addition of1,10-orthophenanthroline on a Corning model252 calorimeter using a490nm filter.

Determination of Calcium and Magnesium:

The amount of calcium present in seaweeds was determined by titrating a known volume of the test solution with standard EDTA with Patton-Reeder's indicator and using potassium cyanide as the masking agent. The amount of magnesium present in seaweeds was estimated as follows: The total amount of magnesium and calcium present was determined by titrating known volumes of test.solution with standard EDTA solution with Eriochrome Black T as indicator and using potassium cyanide as masking agent. The amount of magnesium is obtained by subtracting the amount of calcium present from this value.

Determination of Sodium and Potassium:

Sodium and potassium were determined using a Corning Model400flamephoto-meter using appropriate interference filters. The flame intensities for sodium were corrected for interference by calcium by the standard addition method.

PREPARATION OF SEAWEED LIQUID FERTILIZER:

Seaweeds were shade-dried for four days, followed by oven-drying for24 hours at 60°C. The dried seaweeds were used for the preparation of Seaweed Liquid Fertilizer (SLF) following the method of Rama Rao. The filtrate thus obtained was considered as 100% SLF, from which different concentrations (12.5%, 25%, 50%, 75% and 100%) were prepared by adding distilled water. As the liquid fertilizer contained organic matter, it was refrigerated between 0-4^oC until use.

SELECTION OF CROP PLANTS:

The crop plant, selected for the present study was Abelmoschusesculantus belonging to the family of Malvaceae. The seeds were collected from the SPIC Bio-technology Division, Chennai, Tamil Nadu. The seeds with uniform size, color and weight were chosen for the experimental purpose and surface sterilized with 0.1% HgCl_l2 for 1minute and thoroughly washed with distilled water 35 times. Seeds were presoaked for 12 hours in distilled water and were sown in sterilized vermiculate, moistened with distilled water.

SEAWEED LIQUID FERTILIZER TREATMENT:

After 20 days of germination, the seedlings which were of uniform length (15±2cm) were transferred to pots containing garden soil. After 20, 40, 60 and 90 days, selected concentrations of SLF were sprayed on the leaves (20seedlings/concentration) @ of 2ml /seedling. One batch of seeds were kept as control and treated with distilled water. Plants that were hundred days old were taken for observation. Different parameters namely fresh and dry weight of whole plant, root and shoot length, number of lateral roots, leaf area, number of leaves, flower and fruits, fruit length, fresh and dry weight of fruits and yield were recorded.

RESULT ANALYSIS:

The present investigation shows that the foliar treatments using extract from Dictyotadichotoma exhibits promising effects on growth and yield characteristics of the test plant Abelmoscusesculantus. The growth promoting properties of the seed treatment using sea weed extract improves the quality of the soil and increases the crop yield. This study also confirms that use of SLF is a wise ecofriendly technique to enhance crop production.

CONCLUSIONS:

Since the plant Abelmoscusesculantus shows improved growth when it is treated with seaweed liquid fertilizer, we can further proceed by making seaweeds in to different types of fertilizers such as direct usage of seaweed as fertilizer, decomposed seaweed as fertilizer, dried seaweed fertilizer etc. not only that since seaweeds are rich in minerals it can be used along with some other bio fertilizers to improve the plant growth in the field. It is to enrich the soil fertility. In large scale seaweeds can be cultivated and it can be used as fertilizer, it is not only eco friendly and to improve the soil fertility, it will also help to improve the economic background of the people living along the coastal area.

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Received on 25.08.2013 Accepted on 01.09.2013

Research J. Engineering and Tech. 4(4): Oct.-Dec., 2013 page 149-151