The Pollution of Water bodies in the Dry Zone has begun
If extremely large quantities of phosphate fertilizer continue to be added to the farmlands of Sri Lanka, the quality of the drinking water in the country may be affected adversely in the not too distant future owing to eutrophication.
The word eutrophication which came into common usage in environmental circles in the early 1960s, is derived from the Greek words eu and trophe meaning well nourished. It may be defined as the nutrient enrichment process of a water body that can lead to unusually high growth of aquatic biota, an example being algae. Increase in the concentration of phosphorus (P) in many waterbodies has led to algal blooms in diverse parts of the world, mostly during the last 50 years. Excessive growth of algae may discolour the water, make washing, bathing, swimming, and other recreational activities not possible, hinder navigation, reduce significantly the visits of birds and prevent wallowing of buffalo. Furthermore, it can lower the levels of oxygen in the water, lead to fish kills, bring about unpleasant smells and produce algal toxins that are highly poisonous and make water unsuitable for human drinking even after boiling.
For the last fifty years vegetable growers in Nuwara Eliya have been adding very much more chemical fertilizers than is recommended by the Department of Agriculture (DOA) as shown by the researchers of DOA and the Post Graduate Institute of Agriculture. In fact some growers have been adding up to eight times the recommendation. Furthermore, almost all vegetable growers in Nuwara Eliya add large quantities of cattle manure every year that also adds phosphorus to the soil. Excess additions of phosphate fertilizer do not give higher crop yields.
Soil tests are used throughout the world in determining the amount of phosphorus fertilizer to be added to a crop. The most widely used method is the Olsen test. This test is used by DOA for its mandated crops that include rice, vegetables, potato, maize, chilli, onion, grain legumes, fruits and many other crops.
Soil phosphorus status in Nuwara Eliya district
The Olsen phosphorus (P) value of unfertilized forest lands in Nuwara Eliya rarely exceeds 10 parts per million (ppm). If a soil contains 30-40 ppm P only small amounts of fertilizer phosphorus are required to obtain optimum crop yields.
The Sita Eliya Agriculture Research Station carries out chemical analysis of soils of farmers’ fields. Very recently I took a look at the soil phosphorous values of Nuwara Eliya farmers’ fields collected by the Agriculture Research Station at Sita Eliiya during the last twelve years. The values were very much higher than what they should be. The highest ten values were 490, 450, 440, 400, 390, 380, 355, 340, 315 and 309. The names of the cultivators and the locations of their farms are given in the soil register of the Research Station.
I hasten to say that I have hardly seen such high soil phosphorus values in the farmers’ fields of any other country during my study of the subject of soil science during the last fifty years.
The farmers have lost money by adding excess fertilizer. The public has lost money by subsidizing the fertilizer. The country has lost a colossal sum of money in foreign exchange by importing triple superphosphate. The country has also lost by harming the environment, a damage that can hardly be expressed in terms of money.
How is the environment damaged when soil phosphorus levels are very high ?
The United States Department of Agriculture (USDA) has made a major contribution in 2003 towards minimising eutrophication of waterbodies. A document titled “Agricultural Phosphorus and Eutrophication” published by USDA shows that when a soil exceeds 60 ppm Olsen P there is a very rapid increase in the movement of phosphorus from land to water. This value is now referred to as the Environmental Critical Limit (ECL) of soil phosphorus.
A number of steps has been taken by the developed countries to ensure that this limit is not exceeded in their farm lands. In some countries farmers have to get their soils tested at accredited laboratories every five years before permission is granted for cultivation. In a few others laws are in place to prevent excess additions of phosphorus containing fertilizers that exceed the ECL.
I hasten to inform the reader that Nuwara Eliya today has 742 farms that have soil P in excess of the ECL. Furthermore, the average soil P value of these lands is 134 ppm. It should be said that Nuwara Eliya soils are highly polluted with phosphorus and would thereby pollute the waterbodies downstream.
Furthermore, even if phosphorus fertilizer application is banned in these farms forthwith, the soils will continue to release their phosphorus to the waterbodies because they have already exceeded the environmental critical limit. The pollution of water in our reservoirs has begun. It may take even a decade for the phosphorus levels to come down to safe values.
Recent research carried out by seven universities and three research institutes have found high levels of phosphorus in many of the lakes, tributaries of Mahaweli river, Mahaweli river itself and several reservoirs, particularly those at Anuradhapura and very recently in Maduru Oya.
The National Water Supply & Drainage Board has been collecting and analysing water samples every month from a number of waterbodies in the country to ensure that the people get safe drinking water. The water of reservoirs Nachchaduwa, Nuwarawewa, Kalawewa and Mahakanadarawa for the period October 2016 to March 2017 were eutrophic, meaning that algal blooms could occur at anytime. Such an event will severely restrict the use of the water. It may be mentioned here that the Department of Agriculture analysed P content of several reservoirs in 1965. None of them had high phosphorus values at that time.
Toxic algal species have been found in the reservoirs at Anuradhapura
Local scientists have shown the presence of the toxigenic Microcystis and Cylindrospermopsis species in Anuradhapura waterbodies for more than a decade. Some researchers indicate that their spread is increasing. The toxins released by these algae cannot be destroyed by boiling. There are several examples from other countries of instances of algal contamination of drinking water sources.
On August 04, 2014, The New York Times reported that 500,000 residents of Toledo, the fourth largest city in Ohio, USA, were without drinking water for 48 hours. The municipal water supply has been shut down due to the detection therein of Microcystis, the toxin producing blue-green alga. It has been reported that this situation arose due to eutrophication of Lake Erie arising from excessive use of phosphorus containing fertilizers. What happened in Toledo can happen here.
Hardly any scientist can state with certainty whether algal blooms will occur or not at any point of time in a waterbody. This is mainly because several factors are involved in the formation of a bloom. However, there can be no bloom if phosphorus levels are low, and therefore no toxins.
If excess phosphorus fertilizer addition continues it is certain that phosphorus content in water will increase with time. And a point may be reached where it is too late. This should not be allowed to happen.
1. Cultivators have been adding excess phosphate fertilizer for a long time in Nuwara Eliya.
2. Consequently, the soil phosphorus levels have increased to environmentally dangerous levels.
3. The reservoirs in Anuradhapura have very high phosphorus content. Algal blooms may occur there anytime.
4. Toxic algal species are found in many of the reservoirs in Anuradhapura. If they spread, the water will be not drinkable.
5. Immediate action must be taken to prevent addition of excess P fertilizer.
The problem has originated in Nuwara Eliya although the potential victims may be elsewhere. There are several government and non government institutions directly or indirectly involved in this matter. They include the District Secretariat, Nuwara Eliya, Ministry of Agriculture, Ministry of Environment, Department of Agriculture, Department of Agrarian Services, Department of Irrigation, Department of Health, Central Environment Authority, Universities, Research Institutes, National Water Supply and Drainage Board, Ceylon Fertilizer Corporation and other state organizations marketing fertilizer, Private sector fertilizer dealers, farmer organizations, Environmental Action Groups and perhaps many others. All of them must do their job to prevent yet another calamity in the country.
Disaster management is smart. Disaster prevention is much smarter.