Wednesday, November 25, 2015


This article was printed in the WWF quarterly magazine Natura (vol 39)

The air over Pakistan is polluted and often unhealthy for its population which is about three percent of the total population of the world. In October and November this pollution and its effects become worse due to a practice known as crop residue burning that takes place in many places but particularly in the agricultural region of the Punjab of both India and Pakistan.
October - November is the period when rice is harvested and the harvested fields prepared for the planting of wheat, the next major crop. The wheat is in turn harvested April-May. When a crop is harvested (cut), a stubble remains. The next crop in the recently harvested field either incorporates this stubble or is planted after removing it, in a clear field.  The quickest way of removing the stubble is to set fire to it. In October –November due to the recent monsoons and other meteorological reasons smoke is slow to disperse.  The smoke from these fires lingers over the region like a noxious blanket affecting both health and visibility. 
In more leisurely days it was the practice to allow stubble to remain in the field for a while before another crop was planted.  This allowed the stubble to degrade and pass its nutrients back into the soil. The next crop was nourished by both the old and fresh nutrients.
A few decades ago however, farmers decided to waste less time and started burning the stubble to remove it.  This is now common practice in Pakistan. 
Burning leaves a layer of ash over the field, which may be useful depending on several factors.  Not all plants produce nutritious ash for a start. Then, burning removes the nitrogen and sulfur depriving the soil of these nutrients, while calcium, potassium and magnesium remain.  The carbonates and oxides present in the ash raise the soil’s pH balance, which is good only if the soil is acidic and if the crop being planted appreciates alkaline soil.  Not all crops do. Alkaline soil is outright harmful for a crop of potatoes for example because it creates a favourable environment for a kind of potato scab.
Burning stubble is useful if the soil contains termites and ants because the fire gets rid of these insects quite effectively. 
In the final analysis though the burning stubble method of soil preparation appears to do more harm than good.  Crop residue burning has significantly raised greenhouse gas levels. Satellite data reveals high levels of these gases over many regions of the world, including over the Indian Ocean region. Smoke travels surprisingly long distances. The smoke produced in the Indo Gangetic Plains sometimes carries over and across the Himalayas. People breathe in this smoke and fumes and suffer from respiratory disease, particularly the young and the elderly.  In addition to humans, small wildlife living, nesting and feeding off the area also suffers.  Their food sources and nesting sites are destroyed.  These fires can be particularly disastrous for animals that nest on or close to the ground, and for those animals whose young are less mobile.  Other harmless creatures such as bees and some rodents that are ecologically valuable also suffer. 
The old method of preparing fields for harvesting is therefore preferable, the one that allows the stubble to remain while the new seeds are planted around it. This method which does not require the field to be tilled is called ‘zero till’.
Today crop residue is also being converted into bio-energy in many countries.  In Zimbabwe in fact almost half the power used is provided by plant residue.
Pakistan, with its huge energy crisis needs to explore this source of energy. Manufacturing plants could be constructed close to agricultural sites and farmers supplied with the means of transporting plant residue to collection centers. Animal waste such as dung can also be collected in the same way. Together this waste material can be used to produce both kinds of bio-energy, electricity and gas.  
Natural resources that would otherwise go waste used to make clean fuel, produced in a way that is friendly to plants, humans and animals… that is definitely something to work towards. We have the raw material in abundance. Three other things are required to make this work: The will to make it happen, planning and investment.
How about it?

1 comment:

  1. Most arable land in Pakistan has a high soil pH (alkaline). Crop burning worsens this and also contributes to soil erosion in addition to the other drawbacks mentioned.


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