Tuesday, October 29, 2013

Effects of modern agriculture - Fertilizer Pesticide problems, Water logging, Salinity

Agriculture is an art, science and industry of managing the growth of plants and animals for human use. Agriculture includes preparation of soil for cultivation of crops, harvesting crops, breeding and raising livestock, dairying and forestry.
The two major types of agriculture are:

  1. Traditional agriculture and
  2. Modern or Industrialized agriculture
Modern agriculture makes use of hybrid seeds of single crop variety, technologically advanced  equipment, fertilizers, pesticides and water to produce large amounts of single crop.

Problems using fertilizers
  1. Micronutrient imbalance: Chemical fertilizers used in modern agriculture contain Nitrogen, Phosphorus and Potassium (N,P,K) which are macronutrients. Excess use of fertilizers in fields causes micronutrient imbalance. Ex: Excessive use of fertilizers in Punjab and Haryana caused deficiency of micronutrient Zinc thereby affecting productivity of soil.
  2. Nitrate pollution: Excess Nitrogenous fertilizers applied in fields leach deep into the soil contaminating the groundwater. If the concentration of nitrate in drinking water exceeds 25 mg/L it leads to a fatal condition in new-born babies. This condition is termed "Blue Baby Syndrome"
  3. Eutrophication: The application of excess fertilizers in fields leads to wash off of the nutrient loaded water into nearby lakes causing over-nourishment. This is called "Eutrophication". Eutrophication causes the lakes to be attacked by "algal blooms". Algal blooms use nutrients rapidly and grow fast. Their life is short, they die and pollute water thereby affecting aquatic life in the lake. 
Problems in using Pesticides:
In order to improve crop yield, pesticides are used indiscriminately in agriculture. Pesticides are of two types:
  1. First generation pesticides that use Sulphur, Arsenic, Lead or Mercury to kill pests
  2. Second generation pesticides such as  Dichloro Diphenyl Trichloroethane (DDT) used to kill pests. These pesticides are organic in nature. Although these pesticides protect our crops from severe losses due to pests, they have several side-effects as listed below:
      1. Death of non-target organisms: Several insecticides kill not only the target species but also several beneficial not target organisms
      2. Pesticide resistance: Some pests that survive the pesticide generate highly resistant generations that are immune to all kinds of pesticides. These pests are called "superpests"
      3. Bio-magnification: Most pesticides are non-biodegradable and accumulis ate in the food chain. This is called bio-accumulation or bio-magnification. These pesticides in a bio-magnified form are harmful to human beings.
      4. Risk of cancer: Pesticide enhances the risk of cancer in two ways (i) It acts as a carcinogen and (ii) It indirectly suppresses the immune system.
If water stands on land for most of the year, it is called water logging.
In water logged conditions, pore-voids in the soil get filled with water and soil-air gets depleted. In such a condition the roots of plants do not get enough air for respiration. Water logging also leads to low mechanical strength of soil and low crop yield.

  1. Excessive water supply to the croplands
  2. Heavy rain
  3. Poor drainage
  1. Avoid and prevent excessive irrigation
  2. Sub-surface drainage technology
  3. Bio-drainage by trees like Eucalyptus
Water not absorbed by soil, is evaporated leaving behind a thin layer of dissolved salts in the top soil. This is called salinity of the soil. Saline soils are characterized by accumulation of soluble salts like sodium chloride, calcium chloride, magnesium chloride, sodium sulphate, sodium carbonate and sodium bicarbonates. Saline conditions are exhibited when pH is greater than 8.0

  1. Saline soils yield less crop
In order to remedy the condition of saline soils the following two techniques may be used:
  1. Salt deposit is removed by flushing with good quality water
  2. By using a sub-surface drainage system, the salt water is flushed out slowly.
Canal irrigation in Haryana resulted in rising water table followed by water logging and salinity causing  low crop productivity thereby huge economic losses.
Similarly the "Indira Gandhi Canal Project" in Rajasthan converted a big area into a "water soaked waste land".

In Delhi, accumulation of pesticides and DDT in the body of mothers caused premature deliveries or low birth weight infants.

Food centre at Center for Science and Environment  (CSE) India reported Pepsi and Coca-Cola companies sold soft drinks with a pesticide content 30-40 times higher than EU guidelines permit. At the reported concentrations the pesticides damage the nervous system.

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