fertilizer as pollution agents

FERTILIZER AS A SOURCE OF

POLLUTION AND CONTROL MEASURES

  Throughout human history, increasing population growth and

changing dietary patterns have resulted in more and more land

moving from forest or grasslands into agricultural production.

Over the past few decades, the greatly increased use of chemical

fertilizers plus changes in irrigation practices and improved crop

varieties, have enabled land already under cultivation to be

farmed much more intensively. Synthetic fertilizers have played

a dominant role in agricultural intensification in industrialized

and developing countries like India for decades. Both fertilizers

and pesticides have become widely distributed in the

environment and most of the concern today related to the health

consequences of agriculture now centers on these two (as a

source of environmental pollution). 

Fertilizers as a source of pollution

India has come a long way, since independence, in respect of

production and consumption of fertilizers. In the year 1951-52 the

country produced a mere 27,000 tonnes of fertilizers, which now rose

to a level of 13,4 million tone (2000-01). Likewise the per ha

consumption of fertilizers, which was as low as 1,5 kg/ha during

1951-52 has now increased to 94 kg/ha in 2000-01. the increased use

of fertilizers beginning with the year 1966-67 was due to

intensification of agriculture, particularly in irrigated areas.

 Several problems linking excessive use of fertilizer with

environment have been identified. The increase of nitrates in the

drinking water, a development about which general public is greatly

concerned, and believed to be due to excessive use of N fertilizers and

animal manures, is regarded as most important fertilizer related

pollution issue. Nutrient enrichment, eutrophication and deterioration

of surface water quality due to transpiration of nutrients applied

through fertilizers via leaching and /or runoff and sediment erosion is

another problem. The contamination of soils by heavy metals through

fertilizers such as cadmium from phosphatic fertilizers, is also

receiving increasing attention of environmentalists.

 Pollution due to excessive nitrate in soil

 Nitrate can be absorbed by crop plants, lost beyond the rooting

zone of the crops via leaching or denitrified to N

O gases. Nitrate

leaching below the root zone of crop constitutes a potential pollution

threat for surface and groundwater bodies. The production of N

2

O

through nitrification- denitrification reaction represents a potential

danger in terms of damage to both stratospheric ozone layer and the

greenhouse effect. Nitrate can also be absorbed in large amounts by

plants, particularly fodders and vegetables, and result in nitrate

toxicity to the consumers. Thus a majority of the environmental issues

related to N-use in agriculture revolve around transformations leading

to the production of nitrate in soil.

 Nitrate pollution of groundwater

Two major factors controlling the leaching losses of nitrate are

(i) the concentration of nitrate in the soil profile at the time of

leaching, and (ii) the quantity of water passing through the soil

profile. High soil nitrate levels and sufficient downward movement of

water to move nitrate below the rooting depth is often encountered in

high intensity irrigated agriculture combined high levels of nitrate-N

can lead to methemoglobinemia (blue baby syndrome) particularly in

infants (< 6 months old). The WHO standard for drinking water is 10

mg NO

3- N/L. The effects of nitrate on livestock are similar to those

on human beings. Cattle are more susceptible to nitrate poisoning

than sheep and if pregnant, may abort. An excessive ingestion of

nitrates may also increase the risk of cancer in human population

through in vivo formation of carcinogenic nitrosamines by the

reaction of ingested amines with nitrates in the human stomach.

Nitrate concentrations in groundwater have increased in several parts

of the world in recent years.A significant correlation exists between

the amount of fertilizer-N applied per unit area per your and nitrate-N

concentration of well water in Punjab. At many places, nitrate levels

have exceeded the safe limit of 10 mg NO3-N/L (Table 6.1 and 6.2)

 Nitrate- N content (mg N/L) in tube wells and

hand pumps in four blocks of Ludhiana district in July

1999

Block Tube wells Hand pumps

High

fertilizer

use

Jagraon

Samrala

Low

fertilizer

use

pakhowal

Dehion

Range Mean Range Mean

2.46-16.16

1.44-8.73

1.67-4.41

1.32-9.25

6.49

4.06

2.82

4.29

Source: Roopna- Kaur (2000)

3.57-49.74

0.92-29.58

2.95-13.19

0.15-20.64

12.6

12.4

6.75

8.67

. Nitrate concentrations in water supplies

of few cities of India

Location Highest nitrate level

Observed (mg/L

Churu, Rajasthan

530

Meerut, Uttar Pradesh

156

Jaipur, Rajasthan

180

Nagpur, Maharashtra

77

Hyderabad, Andhra Pradesh

78