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Agrochemical fertilizers use in tea gardens and their impact on drinking water sources of Sonitpur district, Assam, India.


India is one of the most important tea producing country in the world, where 60% of tea is produced in Assam a state of India. Historically, Assam is the second commercial tea production region after southern China. Southern China and Assam are the only two regions in the world with native tea plants. The variety of Assam tea is called Camellia sinensis var.assamica [1]. In Assam there are large multinational tea gardens as well as small tea growers established small tea gardens which is like a revolution. For increase production a large number of agrochemicals are use in these gardens [2]. Types and amounts of chemical substances added to agricultural land are rapidly increasing with development of industrial technology. As a result soil and water pollution becomes conspicuous [3]. In these gardens legally or illegally contaminated fertilizers like zinc-oxy sulphate and sub-standard pesticides are used which are banned in the developed countries. The residues of some pesticides can persist in the environment for more than 20 years [4]. The residues of these chemicals are polluting or contaminating the environment, especially the soil and water, entering in to the food chain, causing threat to human health [5]. So this problem is assumed to be more sever in the near future in the state. In the above context, it is urgent to know as to what extent, the physical environment has been polluted or contaminated by the agro-chemicals. So an attempt has been made to determine the present level of pollution status in the district of Sonitpur, Assam, India.

Materials and methods

Study Area

The district Sonitpur, (second largest district of Assam after Karbi Anglong in area.) which is taken as study area is located in the north east part of Assam. The total area of Sonitpur district is 5103 sq. kms. and lies 100 meter above the mean sea level [6]. It is surrounded by Arunachal Pradesh in north, the Brahmaputra river and Morigaon, Nagaon, Jorhat and Golaghat districts in south, Darrang district in the west, Lakhimpur district in the east and. Sonitpur district is located north bank of river the

Brahmaputra within 26[degrees]2 and 26[degrees]6 N latitude and 92[degrees]2 and 93[degrees]5 E Longitude [4]. Located between mighty Brahmaputra River and Himalayan foothills of Arunachal Pradesh, the district is largely plain with some hills. Land use in the district is divided primarily among tropical semi evergreen, moist deciduous, riverain forest, grassland agricultural land and tea garden. The temperature ranges from 7[degrees]C in January to as high as 38[degrees]C in May. Sonitpur District falls in the Sub-Tropical climatic region, and enjoys Monsoon type of climate. Summers are hot and humid, with an average temperature of 29[degrees] C. The annual rainfall in the district is 2393mm. The climatic conditions of this area are very suit for the tea cultivation. It is interesting to note that the Monabari tea estate, the biggest tea garden in Asia is situated in Sonitpur district. According to the estimate of 2004, in Sonitpur district itself, there are 62 large tea gardens and 207 registered tea gardens covering an area of 497.57 hectares [6] and based on this a numbers of small tea industries are growing day by day. The location map of Sonitpur district is shown in figure 1.


Sampling Methodology

Soil samples were taken at the depth of 0-15 cm. from six selected tea gardens by adopting simple random sampling technique by maintaining a distance of about 50 meters between two samples. A "V" shaped cut at random locations was made in each sampling sites and one inch of soil on either side of pit was scraped and collected in polythene bags. Quartering technique was adopted to reduce the size of the sample to the required mass and air-dried. The air dried samples is crushed by hand using pestle and mortar and analyzed for pH, N,P,K and heavy metals [7]. For water total 60 numbers of samples were collected from different drinking water sources of the six small tea gardens of Sonitpur district. The sources of the water samples were shallow hand tube wells (HTW ~60ft deep, deep tube wells (DTW) like Tara pump (~120ft deep) and mark tube well (~180ft deep), ring well, ponds and drains. Tube wells were operated at least 10 minutes before collection to flash out the stagnant water inside the tube and to get fresh ground water. The water samples were collected in clean 1L Poly propylene bottles.

Sample Analysis

pH of the soil and water samples were measured by Pocket pH meter (Merck, India). The content of chloride and phosphorous concentration was determined by the method of Richard [8]. Heavy metals concentration in soil and water were determined by Atomic Absorption Spetro-Photometer [10, 11] (AAS; model Perkin Elmer 200, USA) at their respective wave length and slit width. Hydrate Generation-Atomic Absorption Spectrometry (Hg-AAS) was used for analysis of As in water samples. S[O.sub.4.sup.2-] content present in the water samples were analysed by turbidimetrically at 450 nm using UV-spectrophotometer (SPECORD 40, Analytic Jena, Germany).

Name of the Agro-Chemicals, which were used in the study area

The agro-chemicals mainly artificial fertilizers and pesticides which are used in small tea gardens are survey by questionnaire which is shown in Table-1.

Result and Discussion

Soil Quality

Soil pH: The pH values reflect the health status of the soil as to whether it is fit for cultivation or not. Soil pH is a good indicator for possible nutrient problems. Soils in the study area are highly acidic, with pH ranging from 3.48 to 5.5. This is because of constant addition of agrochemicals in the soils This may affect the nutrient uptake of the tea plant. Williams [12] has mentioned that chemical fertilizer can play a vital role to change pH condition in soil.

Total Nitrogen (N) in Soil: Nitrogen is essential for plant growth and thus causes problems when it is deficient. The ranges of nitrogen in the study area is 165.8 to 584 Kg/ha. The nitrogen contents of soils in the study area are marginal as according to the chemical rating chart [13]. The highly acidic nature of soils of the study area prevents organic matter from breaking down, resulting in an accumulation of organic matter and the tie up of nitrogen, that are held in the organic matter.

Phosphorous(P) Concentration in Soil: Phosphorous(P) is an important element classified as a macronutrient because of the relatively large amounts of P required by plants. The ranges of Phosphorous in the study area from 2.0 to 48.9 Kg/ha. In acid soils, there is a tendency towards low phosphorous levels over time. This phosphorous applications on soil leaches to water bodies, it may cause eutrophication of water, a form of water pollution. The P in the soil comes from phosphate fertilizers.

Potassium(K) Concentration in Soil

Soil potassium (K) is found in three forms; trapped between clay layers (relatively unavailable), adsorbed on the surface of soil colloids (exchangeable), and in the soil solution (available). The soils in the tea gardens of the study area are ranging from 16.6 to 317.6 Kg/ha.

Organic Carbon

Monitoring levels of soil organic carbon provides a good measure of the fertility of soil. In the study area the soil samples of tea gardens are found to contain 0.40 to 2.66 percent of organic carbon which is actually low contents. Exploitative, environmentally damaging land management practices in the area tend to reduce soil carbon levels.

Water Quality

The water samples are collected from surface, sub-surface and tube well the pH and concentration of different ions and elements like [F.sup.-], [Cl.sup.-], S[O.sub.4.sup.2-] , P[O.sub.4.sup.2-] As, Fe, Mn, Hg, Cd concentration are shown in (table-3&4).

Different parameters of water quality of drinking water sources were shown in the (table 3 & 4). The pH (WHO limit: 6.5- 8.5) is a numerical expression that indicates to which a water is acidic or alkaline and is an operational parameter. High pH levels are undesirable since they may impart a bitter taste to the water. In the present study the variation of pH is 6.0 to 8.8 which is narrow and in general the pH is towards alkaline side.

The [F.sup.-] concentration in the study area is found from 0.01 to 1.51ppm. which is safe limit provided by WHO [14]. Chloride ([Cl.sup.-]) It is one of the major anions found in water and wastewater. The recommended maximum contaminant level is 250 ppm, since the chloride ion imparts a salty taste to the water. In the study area the range of [Cl.sup.-] ion is 11.2 to 138.5 ppm. The drinking water limit of Sulphate is 250 mg/L. Sulfate (S[O.sub.4.sup.2-]) is distributed in natural waters, if it is above standard limit then aesthetic problems and sulfates laxative effects occurs. In the study area the the range of sulphate is within limit of 5.8 to 101.56ppm. Phosphate(P[O.sub.4.sup.2-]) is typically a limiting plant nutrient in surface waters, the WHO limiting value in drinking water is 0.1ppm, the concentration of phosphate in the study area is 0.030 to 1.380ppm. which is above the permissible limit the high concentration is due to excessive use of phosphate fertilizer in the soil. The range of As in the study area is 0.001ppm to 0.083ppm. which is above the WHO guide line of 0.01ppm [14], Arsenic is highly toxic and its prevalence is due to the natural occurrence of this metal and past use of arsenic in pesticides. Arsenic poisoning typically makes people feel tired and depressed and this poisoning is also associated with weight loss, nausea, hair loss, and marked by white lines across the toenails and fingernails. Iron (Fe),the WHO limit in drinking water is 0.3 ppm. The main source of As is DAP and pesticides. Iron is a secondary drinking water standard and primarily regulated because of the aesthetic problems associated with elevated iron concentrations. The range of iron in the study area is from 0.20 to 24.29 ppm. Which is very high to WHO limit this is because of high amount of micronutrients use in the soil. The problem of iron bacteria is result for high amount of iron present in the water. The study revealed that 80% of total water samples had Mn concentration above the permissible limit (0.3 ppm) of WHO standards [14].The range of Mn in the study area is 0.02 to 4.59 ppm. Manganese is primarily regulated because of the aesthetic problems associated with elevated levels of manganese, i.e., a secondary drinking water standard. Elevated manganese levels can disrupt the nervous system and regeneration of hemoglobin [15]. Mn may come from use of huge amount of super phosphate in soil. Mecury (Hg) the WHO limit is 0.006 ppm, in drinking water. Mercury has been associated with kidney disease. In the study area it has been found from trace to 0.095 ppm. Hg may comes to water sources from pesticides. Cadmium (Cd) is very dangerous for human health, the WHO limit for cadmium in drinking water is 0.003ppm. Cadmium poisoning is associated with kidney disease and hypertension and possibly mutations. The range of Cd in water sources of study area is found from 0.002 to 1.38 ppm. Cd may come to water sources from super phosphate, DAP etc.


The drinking water pollution in the tea garden areas of Sonitpur district, Assam, is significant. As found out from the experimental results, soils in the tea gardens of Sonitpur district generally have properties that make their management somewhat difficult. The long- term deterioration of soil under the tea gardens in the area has led to impoverishment of soil fertility and stabilization of yields, despite increasing application of external inputs such as fertilizers and pesticides. Among various chemical parameters of soil quality pH, available N, P, K and %C are considered to be sensitive environmental parameters and have direct bearing on productivity and fertility of soils. These agrochemicals have direct impact on the drinking water sources in these tea garden areas. From the present study it is observed that these drinking water sources are poorly managed and show sign of heavy metal pollution. This is may be due to use of agrochemicals in the tea gardens in a uncontrolled manner. In the present state, these drinking water sources are not safe for use in the tea garden community and this may lead to poor drinking water quality. The continuous and uncontrolled use of different chemicals in the tea gardens areas of this region may increase the pollution rate which may lead to cause an adverse health effects to the tea garden community. Even in long term use of these chemicals, they may cause cancers of kidney, lung, liver etc. this is why there is an immediate and urgent need for the implementation of a better water quality management policy in corporating the following recommendations.

* The use of pesticides, insecticides and other chemical inorganic fertilizers should be reduced.

* Tube wells and other drinking water sources should be installed in a safety place.

* The organic fertilizers may increase the rate of tea production and reduce the pollution rate of the environment of water, soil and air.

* A proper planning and management can solve the problems


The authors wish to acknowledge the director NERIWALM, Tezpur, Assam for providing laboratory facilities and thankful to Indira Gandhi National Open University, New Delhi for financial assistance in the form of MRP, No. D/EDNER/7052.


[1] Kiple, Kenneth F.; Ornelas, Kriemhild C. (October 2000). The Cambridge World History of Food (Volume 1). Cambridge University Press. ISBN 0521402166.

[2] Dutta Joydev, Bhuyna,B. and Misra,A.K., " Chemical Estimation of Soil Fertility Status in and around the Tea Gardens of Gohpur Sub-Division, Assam". Int.J.Chem.Sci.: 6(2),2008,1099-1105.Udaipur,India.

[3] Han,J.-L., F.-S. Jin, and K. Egashira 2007, "Environmental Impact Assessment of Tea Garden Soils by the Heavy Metal Concentration in Shandong Province, Chaina. J. Fac. Agric. Kyushu Univ., 52(1), 135-139(2007).

[4] Miles, C.J. and R.J. Pleuffer, 1997. Pesticides in canals of South Florida. J. Environ. Contam. Toxicol., pp: 337-345.

[5] Roberts, T.R., 1991. Pesticides in water, Human Health, Agriculture and Environmental Aspects. In: Chemistry, Agriculture and the Environment. Richardson, M.I., (Ed.), Cambridge, The Royal Society of Chemistry, U.K.

[6] downloaded on 01.07.09

[7] M. L. Jackson, "Soil Chemical Analysis", Prntice-Hall of India Private Limited, New Delhi (1973), p. 227-255.

[8] Richard, L.A., 1954. Diagnosis and Improvement of Saline and Alkaline Soils. Handbook No. 60 Department of Agriculture, USA.

[9] Eatson A D, Clesceri L S, Rice EW & Greenberg A E, Standard Methods For The Examination of Water and Wastewater, 21st Edition (USA), pp. 4-138 (2005).

[10] Verma N K, Jain O P & Shrivastava P K, Preliminary studies on heavy metals in ground water of Mandideep by atomic absorption spectroscopy, Proc. Acad. Environ. Biol, 4(1), 123-126 (1995).

[11] Williams, C.B., 1964. Patterns in the Balance of Nature and Related Problems in Quantitative Ecology. Academic Press, London, UK.

[12] Indian Council of Agricultural Research (ICAR), "Hand Book of Agriculture", 3rd Edition, New Delhi, Krishi Anusandhan Bhaban, PUSA, New Delhi (2005) p.71.

[13] WHO. 1993, Guideline for drinking water quality, (World Health Organization, Geneva).


* (1) Joydev Dutta and (2) A.K. Misra

(1) Department of Chemistry, Chaiduar College, Gohpur, Assam. 784 168

* E-mail:

(2) Department of Chemistry, Gauhati University, Guwahati, Assam, 781 014
Table 1: Name of major fertilizers used in the tea gardens
of sonitpur district, Assam, india.

Fertilizer Formula

Urea CO[(N[H.sub.2]).sub.2]
Ammonium N[H.sub.4]N[O.sub.3]
Ammonium N[H.sub.4]N[O.sub.3]+
nitrate limestone (CaC[O.sub.3]+MgC[O.sub.3])
Super phosphate Ca[([H.sub.2]P[O.sub.4]).sub.2]x[H.sub.2]O
(Normal) +CaS[O.sub.4]

Super Phosphate Ca(H2PO4)2.x[H.sub.2]O

Murate of Potash KCL
Diammonium [(N[H.sub.4]).sub.2][H.sub.2]P[O.sub.4]
Dolomitic limestone Ca[Co.sub.3]+Mg[Co.sub.3]
Gypsum CaS[O.sub.4]2[H.sub.2]O
Micronutrients CuS[O.sub.4]x[H.sub.2]O,
and others. [Na.sub.2][B.sub.4][O.sub.7]10[H.sub.2]

Fertilizer Nutrients % of nutrients

Urea Nitrogen(N) N-45
Ammonium Nitrogen(N) N-34
Ammonium N, Ca, Mg N-20,Ca-
nitrate limestone 6, Mg-4
Super phosphate [P.sub.2][O.sub.5], Ca,S P-20, Ca-
(Normal) 21,

Super Phosphate [P.sub.2][O.sub.5], Ca,S P-46, Ca-
(Triple) 14,

Murate of Potash K K-60
Diammonium N, [P.sub.2][O.sub.5] N-18, P-
Phosphate(DAP) 46
Dolomitic limestone Ca, Mg Ca- 24to30, Mg-6to12
Gypsum Ca, S Ca-22,S-18
Micronutrients Cu, B, Zn, Cu-
and others. Mo, 25to35,
 Mn etc. B-11,Zn-

Fertilizer Impurities

Urea ...
Ammonium ...
Ammonium ...
nitrate limestone
Super phosphate Cd, Fluride
(Normal) Compounds,
 Mn, Ni, and

Super Phosphate Cd, Fluride
(Triple) Compounds,
 Mn, Ni, and
Murate of Potash ...
Diammonium Cd,Cr,Pb,As.
Dolomitic limestone Heavy metals
Micronutrients Trace as
and others. impurities.

Table 2: Conc. of soil quality parameters in tea gardens.

Gardens Kg/ha. except pH and C
name pH N P K
 (min.-max.) (min.-max.) (min.-max.) (min.-max.)

CR 3.48-4.9 260-264.2 2.0-2.1 23.3-25.4
AS 4.83-5.0 492.3-584 3.14-3.18 23.3-26.8
RP 3.48-4.8 169-172.4 2.01-2.28 16.6-22.4
GD 4.33-4.5 498.7-506.1 6.9-7.04 23.3-28.6
SP 4.5-4.9 277.4-312.9 41.2-48.9 310.5-317.6
SG 4.5-5.4 214.6-235.2 21.7-27.7 44.8-95.6
RU 4.5-4.8 230.6-236.3 26.5-29.6 34.0-38.7
DU 4.5-5.12 214.6-219.5 25.2-32.2 60.7-65.5
BB 4.6-5.1 165.8-167.9 32.8-37.8 99.7-105.5
BD 5.0-5.5 289.3-300.2 40.9-45.2 75.2-80.5

name %C

CR 0.75-0.78
AS 1.75-1.8
RP 0.51-0.65
GD 1.52-1.62
SP 2.04-2.66
SG 0.52-1.23
RU 0.94-0.99
DU 0.40-0.52
BB 0.53-1.32
BD 0.67-0.77

Table 3: Conc. of water quality parameters of pH, [F.sup.-], [Cl.sup.-],
S[O.sub.4.sup.2-], P[O.sub.4.sup.2-] in tea gardens.

Gardens Conc. of different water quality
name parameters in ppm. except pH
 pH [F.sup.-] [Cl.sup.-] S[O.sub.
 (min.-max.) (min.-max.) (min.-max.) (min.-max.)

CR 6.0-7.0 0.17-0.23 11.2-33.9 5.8-25.8
AS 6.7-6.8 0.25-0.67 48.0-103.2 15.4-36
RP 7.1-7.3 0.89-1.1 25.6-99.12 20.1-55.0
GD 6.2-8.0 0.15-1.25 55.9-121.7 46.0-97.5
SP 7.0-8.2 0.01-0.99 82.9-111.1 35.5-88.5
SG 7.1-8.8 0.57-1.02 77.6-101.2 23.9-75.3
RU 7.4-7.6 0.75-0.89 101.1-175.2 45.57-94.57
DU 7.5-7.7 0.92-1.51 78.8-138.5 79.96-101.56
BB 6.8-7.7 0.77-0.95 55.5-100.2 55.5-58.86
BD 6.5-7.3 0.76-0.88 57.8-98.9 68.6-70.7
WHO 7-8.5 1.5 250 500


CR 0.045-1.32
AS 0.105-1.10
RP 0.05-0.135
GD 0.075-0.851
SP 0.080-0.125
SG 0.201-1.380
RU 0.180-1.250
DU 0.030-0.101
BB 0.130-0.160
BD 0.080-0.290
WHO ...

Table 4: Conc. of water quality parameters As,
Fe, Mn, Hg ,Cd in tea gardens.

Gradens Conc. Of heavy metals in ppm.
name As (min.- Fe (min.- Mn (min.- Hg (min.-
 max.) max.) max.) max.)

CR 0.001-0.033 0.31-0.62 0.12-1.64 Trace--0.012
AS 0.02-0.032 0.90-3.99 0.55-0.94 Trace--0.11
RP 0.005-0.083 1.31-4.20 0.84-2.99 .004--0.12
GD 0.02-0.09 0.65-0.95 0.89-2.01 Trace--0.11
SP 0.03-0.067 0.5-1.01 0.94-1.49 0.002-0.095
SG 0.01-0.04 0.20-5.20 0.21-1.83 Trace--0.08
RU 0.01-0.02 1.85-13.22 0.43-6.49 Trace-0.001
DU 0.031-0.033 1.61-3.71 0.02-0.47 Trace-Trace
BB 0.001-0.005 1.40-10.45 0.02-1.26 Trace-0.012
BD 0.011-0.019 22.78-24.29 0.21-4.59 Trace-0.003
WHO ppm. 0.01 0.4 0.001

name Cd (min.-

CR 0.002-0.014
AS 0.005-0.023
RP 0.05-0.135
GD 0.075-0.851
SP 0.08-0.125
SG 0.201-1.38
RU 0.18-1.25
DU 0.03-0.101
BB 0.130-0.160
BD 0.080-0.290
WHO ppm. 0.003
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Author:Dutta, Joydev; Misra, A.K.
Publication:International Journal of Applied Environmental Sciences
Geographic Code:9INDI
Date:Feb 1, 2010
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