INTRODUCTION:

Common salt plays an important role in the world’s economy. Almost 71% of the earth surface is covered with seawater which contains at least 2.5% of common salt.¹ The chemical industry is the largest consumer of salt, using about 60% of the total production. The second largest user of salt is mankind itself. Humans need about 30% of the total salt produced to support their physiological functions and eating habits. The production of common salt is one of the most ancient and widely distributed industries in the world. Evaporation is the chief operation involved in the concentration of weak brine to a stage at which it is saturated with the salts dissolved in it resulting in their separation.² In tropical countries like India, where long dry weather exists, manufacture of salt by solar evaporation is followed and salt of very good quality and quantity has been produced.³While the process for solar evaporation of brines is same around the world, the manufacturing techniques and product quality vary considerably.⁴ The technique of solar salt production involves fractional crystallization of salts in different ponds to get common salt in the purest form possible.⁵ Bittern is an unavoidable material formed during the salt production. It is a desirable source of marine chemicals.

As bittern consists of all the nutrients and trace elements, it can be used as a fertilizer. It can be used in minimum level to attain maximum growth and yield. The nutritive values and growth were very high in plants grown in soil rich in minerals and trace elements.⁶ Bittern can be converted into solid fertilizers like magnesium ammonium orthophosphate and magnesium hydrogen orthophosphate by various improved methods.

MATERIAL AND METHODS:

(a)Magnesium ammonium orthophosphate

The synthesis of this fertilizer using bittern was carried out, using different improved methods.

Method -I:

To 20 ml of bittern, added 15 ml of dilute hydrochloric acid. Then added, 3 ml of orthophosphoric acid and 70 ml of ammonia solution with continuous stirring. A white solid of magnesium ammonium orthophosphate was formed and was filtered and dried. The presence of various ions like Mg²⁺, NH₄⁺and PO₄^3-were analyzed qualitatively and the yield was 12.05g. The solubility was found to be 300mg in 100 ml of distilled water.

Method -II:

To 20 ml of bittern, added 15 ml of dilute hydrochloric acid and 3 ml of orthophosphoric acid. 50 ml of saturated solution of ammonium chloride was added with constant stirring. A white solid of magnesium ammonium orthophosphate was formed and was filtered and dried. Various ions were analyzed qualitatively and the yield was comparatively more i.e., 13.50g. The solubility was 300 mg in 100 ml of distilled water.

Method III:

To 20 ml of bittern, added 20 ml of ammonium hydroxide and 50 ml of saturated solution of ammonium chloride. To this added, 10 ml of a saturated solution of disodium hydrogen phosphate with constant stirring. A white solid of magnesium ammonium orthophosphate was formed and was filtered and dried. The presence of various ions were confirmed by qualitative analysis and the yield was satisfactory i.e., 12.85g. The solubility was again 300 mg in 100 ml of distilled water.

Method IV:

To 20 ml of bittern, added 20 ml of ammonium hydroxide and 50 ml of saturated solution of ammonium phosphate. A white solid of magnesium ammonium orthophosphate was formed and was filtered and dried. Various ions were analyzed qualitatively and the yield was found to be 12.65g. The solubility was 300mg in 100 ml of distilled water.

(b)Magnesium hydrogen orthophosphate:

By using bittern as raw material, this important solid fertilizer was synthesized by the following method.

To 20 ml of bittern, added 50 ml of saturated solution of disodium hydrogen orthophosphate with constant stirring. A white solid of magnesium hydrogen orthophosphate was formed and was filtered and dried. The presence of magnesium and phosphate ions were confirmed by qualitative analysis and the yield was found to be extra-ordinarily high.

To know the fertilizer value of bittern, the biomass production of magnesium demanding plant green chillies was studied. The influence of concentration of solid fertilizer on the growth and yield was studied, by growing these plants in different pots.

Experimental set-up:

All the pots were even with one feet height and 25 cm width. Soil, sand and organic mixture were mixed in the ratio 1:1:1 and this mixture were filled 3/4^th in all the different pots. This experimental set-up was kept in the open terrace so that all the pots can have the same exposure to sunlight. In each pot, two seeds were sown and was watered daily in the morning and evening. The number of days for germination was even in all the five different pots and the entire experiment was carried out for ninety days. The height, stem-width, maximum leaf-width, number of leaves having maximum leaf width and total number of leaves in the plants of the five different pots were recorded. A very dilute solution of metacid (2 ml in one litre of water) was sprinkled using a hand-sprayer once in fifteen days to eradicate the harmful pests. Throughout the study, the yield of fruits was not uniform in all the five different pots. The total number of fruits and total weight of the fruits were recorded on the 91^stday.

Ash Analysis:

The well matured leaves of the plants were cut-off and dried well at room temperature for 3 to 4 days. Of the dried leaves, 3 gm of each was weighed and further dried in an oven at a temperature of 110° – 140°C and were made to ash in silica crucibles. The ash of the five different samples was then digested with triple acid i.e. HNO₃, H₂SO₄ and HClO₄ in the ratio 7:2:1. The contents in the crucibles were heated in sand-bath and were allowed to cool in desiccators. The extract was made up in 25 ml S.M. Flask with double distilled water.⁷

The five different samples were subjected to various analysis viz., percentage of calcium, magnesium, and potassium by standard methods.⁸The trace metals like iron, manganese, zinc and copper were analyzed by Atomic Absorption Spectrophotometer.

RESULTS AND DISCUSSION:

The solid fertilizer was tried as a fertilizer to magnesium demanding crop like green chillies. (Fig 1)The yield of the plants from different pots were presented. The amount of various nutrients like potassium, calcium, magnesium and also the trace metals like iron, copper, manganese and zinc present in the different plants were also presented.

Application of solid fertilizer to plants:

Five pots were used and labeled as G.C-C, G.C-S1, G.C-S2, G.C-S3, and G.C-S4.

G.C-C - Control pot containing the soil mixture alone.

G.C-S1 - Soil mixture + 5g of solid fertilizer evenly mixed.

G.C-S2 - Soil mixture + 10 g of solid fertilizer evenly mixed.

G.C-S3 - Soil mixture + 15 g of solid fertilizer evenly mixed.

G.C-S4 - Soil mixture + 20 g of solid fertilizer evenly mixed.

Yield report:

The yield of fruits started from 76^th day. The number of fruits and weight of the fruits were recorded as and when the fruits were plucked. Since the yield of fruits was not uniform, measurements were made as and when and a consolidated table comprising the total number of fruits and the total weight of fruits are presented.

G.C-C had minimum number of fruits i.e., 15. The total weight of fruits was 75 g. G.C-S1 yielded 19 fruits and the total weight was 83 g. G.C-S2 yielded 24 fruits and the total weight was 94 g. The number of fruits in G.C-S3 was 29 and the total weight was 110 g. But a maximum of 32 fruits was observed for G.C-S4 and the total weight of the fruits was 123 g.

The gradual increase in the total number of fruits and also the total weight of fruits clearly indicated that the increased addition of solid fertilizer which is enriched with secondary nutrients and micronutrients served as a fertilizer by enhancing the fertility of soil and inturn the yield. (Table: 1)

Table:1 Yield report

Classification	Total number of fruits	Total weight of fruits (grams)
G.C-C	15	75
G.C-S1	19	83
G.C-S2	24	94
G.C-S3	29	110
G.C-S4	32	123

G.C – Green chillies

Ash Analysis:

Ash samples from the five different pots were analysed for various parameters such as, the percentage of calcium, magnesium, sulphate and potassium. The trace metals like iron, manganese, zinc and copper were also analysed and presented in ppm. A gradual increase in the values of all the secondary nutrients and micro nutrients from G.C-C to G.C-S4 was observed. (Table: 2)

The percentage of potassium was found to increase marginally from G.C-C to G.C-S4 because the necessary potassium was totally supplied by the soil, sand and organic mixture. Despite the soil mixture provides the required potassium, the increasing addition of bittern, activated a marginal increase in the intake of potassium i.e., 3.6%. For G.C-S1, G.C-S2 and G.C-S3 it was 3.9, 4.0 and 4.4% respectively. Maximum value of 4.8% was observed for G.C-S4. From the earlier observation it was known that the sufficient requirement of potassium for green chillies was 3.5 to 5.0%.⁹(Table: 3)

The percentage of calcium in all the five different ash samples was found to increase gradually from G.C-C to G.C-S4. Though soil provides required calcium, the increasing addition of bittern activated a marginal increase in the intake of calcium. G.C-C had the minimum value of calcium i.e., 1.6% and for G.C-S1, G.C-S2 and G.C-S3 it was 2.0%, 2.8% and 3.1% respectively. A maximum value of 3.5% was observed for G.C-S4. From the earlier observations it was learnt that the sufficient requirement of calcium for tomato is 1.5 to 4.0%.⁹ (Table: 3)

The percentage of magnesium was found to increase significantly from 0.33 to 0.60% since magnesium needed for the plant was exclusively supplied by bittern. G.C-C had the minimum percentage of magnesium i.e., 0.33%. But for G.C-S1, G.C-S2 and G.C-S3 it was 0.42%, 0.48% and 0.54% respectively. Maximum value of 0.60% was observed for G.C-S4. These values were found to correlate with the earlier observations that 0.30 to 0.1% of magnesium is sufficient for green chillies.⁹ (Table: 3)

The percentage of sulphate also increased markedly from G.C-C to G.C-S4 because bittern supplied the necessary requirement of sulphate. G.C-C had minimum percentage of sulphate i.e., 0.56% and for G.C-S1, G.C-S2 and G.C-S3 it was 0.63%, 0.69% and 0.71% respectively. But G.C-S4 recorded the maximum percentage of sulphate i.e., 0.77%. The above results were in agreement with the earlier observation that 0.5 to 1.0% of sulphate is sufficient for green chillies.⁹ (Table: 3)

The trace metals present in the five different samples were also analysed and a marginal increase was observed from G.C-C to G.C-S4.Though the soil mixture provides the required micro nutrients, the trace metals present in bittern activated the intake of various micronutrients, resulted in gradual increase in the values of iron, manganese, zinc and copper from G.C-C to G.C-S4.

G.C-C had minimum value of iron, i.e., 52 ppm and for G.C-S1, G.C-S2 and G.C-S3 it was 69, 76 and 92 ppm respectively. Maximum value of 115 ppm was observed for G.C-S4. The value of manganese is minimum for G.C-C i.e., 62 ppm and for G.C-S1, G.C-S2 and G.C-S3 it was 70, 95 and 119 ppm respectively. Maximum value was observed in G.C-S4 i.e., 132 ppm.

G.C-C had minimum value of zinc i.e., 9 ppm and for G.C-S1, G.C-S2 and G.C-S3 it was 13, 16 and 20 ppm respectively. G.C-S4 was found to have a maximum value of 23 ppm.

Similarly, the value of copper increased gradually from G.C-C to G.C-S4. G.C-C had minimum value of 28 ppm. For G.C-S1, G.C-S2 and G.C-S3 it was 33, 49 and 54 ppm respectively. G.C-S4 had a maximum value of 62 ppm. (Table:3)

Table:2 Ash Analysis

Classification	K (%)	Ca (%)	Mg (%)	SO₄^2- (%)	Fe (ppm)	Mn (ppm)	Zn (ppm)	Cu (ppm)
G.C-C	3.6	1.6	0.33	0.56	52	62	9	28
G.C-S1	3.9	2.0	0.42	0.63	69	70	13	33
G.C-S2	4.0	2.8	0.48	0.69	76	95	16	49
G.C-S3	4.4	3.1	0.54	0.71	92	119	20	54
G.C-S4	4.8	3.5	0.60	0.77	115	132	23	62

Table: 3 Standard values

Classification	Low value	Sufficient value	High value
K (%)	1.05 - 2.89	2.9 - 5.0	>5.0
Ca (%)	0.80 - 0.99	1.0 - 3.0	>3.0
Mg (%)	0.25 - 0.39	0.4 - 0.6	>0.6
SO₄^2-(%)	0.25-0.39	0.4-1.2	>1.2
Fe (ppm)	30 - 39	40 - 200	>200
Mn (ppm)	30 - 39	40 - 250	>250
Zn (ppm)	18 - 19	20 - 50	>50
Cu (ppm)	3 - 4	5 - 20	>20

E.R. Beaufils, Diagnosis and Recommendation Integrated System (DRIS), Univ. Natal Pietermaritzburg, South Africa, 132, 1973.

Fig 1: Green chillies in pots having different concentration of solid fertilizer

CONCLUSION:

As the addition of solid fertilizer was increased, the yield and growth of green chillies also increased gradually. The intake of all nutrients such as calcium, magnesium, sulphate, potassium and micronutrients such as iron, manganese, copper and zinc was high in the plants after the addition of solid fertilizer and was determined by ash analysis.

ACKNOWLEDGEMENT:

The authors are very much thankful to the Principal and the Department of Chemistry, S.T. Hindu College, Nagercoil for providing necessary facilities.

REFERENCES:

1. R. Prakash, Training Course in Salt Technology, Salt Department, Government of India,12, 4-22 August, 1981.

2 JP. Sorgeloos and W. Tackaert, Proc. of the Intl. Symp. on Biotechnology of Salt Pond, Tang Gu, PR China, 13 – 21 September, 1990.

3 M.J. Mehta, Training Course in Salt Technology, Salt Department, Government of India, 51, 4-22 August, 1981.

4 D.W. Kaufmann, Sodium Chloride, ACS Monograph 145, Reinhold Publishing Corp., New York, 1960.

5 D.C. Hahl, Water Resources Bull.10, Utah Geological and Minerological Survey, USA, 1968.

6 S. Chandraju and C.S Chidan Kumar Nutrients Uptake of Top Vegetables Irrigated by Distillery Spent wash in Normal and Spentwash Treated Soil. Asian Journal of Research in Chemistry. 4 (1); 2011: 75-79.

7 C.S. Piper, Soil and Plant Diseases, Hans Publishers, Bombay, India. 1966; 6^th ed: pp. 251-275.

8 B.S. Bhargava and H.B. Raghupathi, Methods of Analysis of Soil, Plants, Waters and Fertilizers, Fertilizer Development and Consultation Organisation, New Delhi. 1999; 3^rd ed: pp. 49-82.

9 E.R. Beaufils, Diagnosis and Recommendation Integrated System (DRIS), Univ. Natal Pietermaritzburg, South Africa, 1973, 132.

Received on 04.08.2013 Modified on 20.08.2013

Asian J. Research Chem. 6(12): December 2013; Page 1099-1102