Scientists have expressed concern over the use of fertiliser-N (nitrogen), which has caused severe environmental disturbances. Nitrogen has been released in the water bodies, causing unwanted growth of aquatic organisms, and has been released into the atmosphere, causing atmospheric pollution and enhancing climate change-related events.
The scientists made these observations while addressing a two-day-long workshop on ‘Towards Integrated Nitrogen Management System (INMS)’, held at a city hotel yesterday (Sunday).
Agriculture minister Dr Abdur Razzaque spoke at the workshop as the special guest.
The director-general of the Bangladesh Rice Research Institute (BRRI), Dr M Shajahan Kabir, the vice-chancellor of Bangabandhu Sheikh Mujib Agriculture University, Dr M Gias Uddin Mia, the director of International Nitrogen Management System, Prof. D. Mark A Sutton, and SANC professors in New Delhi, India, Prof. Dr Nandulal Raghuram and Dr Tapan K Mukherji, also spoke at the workshop.
“Excessive use of fertilisers is harmful for the environment. Though crop production has increased by 30 to 34 per cent after using N-enriched fertilisers, at the same time it has also reduced the fertility of the arable lands,” Dr Razzaque said.
He pointed out that many farmers have no knowledge about the proper use of fertilisers. “The farmers often over-use fertilisers with a view to increase their production. But the
environment becomes polluted after the nitrogen gets mixed with air. It even becomes harmful for humans after the nitrogen mixes with water. Hence, we have to use such fertilisers on a limited scale. The use of such fertilisers will have to be reduced in phases,” the agriculture minister said.
According to experts, in order to extract maximum efficiency of the fertilizer-N in an agricultural way and an environmentally sustainable manner, it is essential that farmers are advised on the rational use of fertiliser-N in different sectors of agricultural productivity like horticulture, aquaculture, animal husbandry and so on.
Apart from agriculture, other sectors of the economy, such as energy production, transport, industry and waste management, also contribute to N-pollution, the scientists said.
The scientists noted that South Asia is one of the most populous regions on this planet. With an agrarian economy to feed its growing population, it is hugely dependent on the use of N-fertiliser.
According to experts, nitrogen is the most important nutrient affecting the growth of all living organisms in this planet. Although more than two-thirds of the atmosphere is nitrogen, it cannot be directly used for biological growth, the experts said.
They opined that this nitrogen has to be converted into its active forms for their uptake and incorporation into plants and animals.
Soil scientists have pointed out that the continuous use of chemical fertilisers and pesticides in the arable land gradually decreases its productivity.
Chemical fertilisers also destroy soil biomass, which is important for maintaining the ecosystem and crop production. Excessive use of chemicals destroys soil nutrients like sodium, potassium and nitrogen, creating imbalances in soil fertility, according to researchers.
Most of the soils have low fertility because of the high removal of plant nutrients from soils. Annual removal by major field crops is about 2.98 million tonnes compared to acreage application of 0.80 million tonnes of nutrients. About 85 per cent of the net cultivable areas have less than the optimum level of organic matter content. Chemical fertiliser use, combined with the timely transfer of appropriate technology, is essential to sustaining and increasing yields.
Urea, di-ammonium phosphate (DAP)/triple super phosphate (TSP) and muriate of potash (MOP) are the major sources of plant nutrients in Bangladesh. Urea represents about 80 per cent, DAP/TSP 15 per cent, and MOP, zinc sulphate, gypsum, etc. account for the remaining 5 per cent of all other nutrients.
This nutrient use pattern indicates a less than ideal nutrient balance. Though paddy does require, in most instances, a higher nitrogen ratio to phosphate and potash, soil testing, soil type and crop rotation are required to determine the exact NPK ratio required to maximise yield to the extent the yield relates to nutrients.
BK