What to expect in the short term and long term

Banning the import and use of synthetic chemical fertilizers:

By Darshani Kumaragamage, PhD d.kumaragamage@uwinnipeg.ca-2021/06/14

I read with interest and concern the conflicting and controversial views expressed by many experts and stakeholders, regarding the Sri Lankan government’s decision to ban the importation of agrochemicals, including synthetic chemical fertilizers. Undoubtedly, some have genuine concerns regarding the negative impacts of synthetic chemical fertilizers on the environment and human health, while others see the potential threat of a food shortage if synthetic fertilizers are totally replaced by organic sources. Any action adopted in a quest to do the “right” thing should be guided by careful analysis of the expected outcomes as well as the unintended consequences, which are often difficult to foresee.

Based on my training and experience in Sri Lanka and in Canada over the last three decades as agriculturist, soil scientist, and environmental scientist, I will attempt to provide a balanced analysis both from an agronomic and environmental point of view. My hope is that these arguments perhaps could shed more light on different thought processes expressed and guide the momentous decisions that are being made.

Organic farming has its benefits and is gaining global popularity. The demand for organically produced food is steadily increasing, particularly in the developed world. Certain aspects of organic farming such as the avoidance of pesticides, have potential benefits in producing food with less negative impacts on the ecosystem health. However, to date, there is no evidence to support that total replacement of synthetic chemical fertilizers with natural organic sources is better for the environment and human health. I am using the term “natural organic fertilizer” in this article, since urea, the most common chemical fertilizer used in Sri Lanka, is also an organic fertilizer, but synthetically produced. While synthetically manufactured urea is not considered an ‘organic’ fertilizer, manure containing naturally produced urea as a metabolic by-product of animals is an approved ‘organic’ fertilizer in organic farming systems.

Chronic kidney disease of unknown etiology (CKDu) and agrochemicals

The alarming rate of chronic kidney disease incidences among farming populations in some regions of Sri Lanka is a grave concern. The decision to ban agrochemicals is undoubtedly taken with the best intention of protecting farming communities against this deadly disease, considering that agrochemicals are the root cause, even though this is yet to be proven. I would like to make three arguments against banning inorganic fertilizer and its replacement with organic sources in relation to CKDu prevention. Firstly, the incidences of CKDu are not from the regions in Sri Lanka where farmers use heavy inputs of inorganic fertilizers such as the Hill Country, which leaves us with an uncertainty whether CKDu is indeed linked to fertilizer. Secondly, even if CKDu is linked to fertilizer, replacing synthetic inorganic fertilizer by natural organic fertilizer will not solve the problem as both these sources have similar impacts on ecosystem and human health. Thirdly, unlike pesticides which are toxic by design (since the intention is to kill an organism), fertilizers are not toxic at recommended rates. Therefore, any environmental or health impacts with fertilizers (inorganic or organic) could be better addressed by importing fertilizers with higher standards (with low impurities), combined with efforts to increase awareness to farmers on the use and management of fertilizers.

Based on current knowledge research findings from Sri Lanka and elsewhere, total reliance on natural organic sources to supply nutrients in crop production systems is likely to cause a serious food shortage with negligible benefits to the environment. Below, I am listing some of the challenges in using natural organic sources, and the major concerns regarding the total replacement of chemical fertilizers with organic sources for mass crop production in Sri Lanka.

 Low inherent soil fertility. Despite our unsubstantiated belief that Sri Lanka is blessed with fertile soils, the majority of agricultural soils in Sri Lanka exhibits serious fertility limitations for crop production. This is not unique to Sri Lanka, but common to most tropical countries. The soils are much older (highly weathered) than in temperate regions and high temperature decomposes organic matter rapidly while heavy rainfall removes nutrients from the soil system. Therefore, unlike soils of temperate regions, tropical soils have low organic matter, low supply of nutrients, and low ability to retain nutrients. Even if a shift to complete reliance on natural organic sources for nutrients could be sustainable in temperate soils, it is not a sustainable approach for mass production of crops in the tropics.

Nutrients not available at critical stages. Unlike synthetic chemical fertilizers, nutrients in natural organic sources are in a form not readily available to crops until the material is decomposed, which takes time. When organic material is added to soils, activity of microorganisms increases, resulting microorganisms and crops competing for nutrients that are in limited in supply in tropical soils. This may cause an initial deficiency of nutrients at the early, but very critical, stage of the crop.

Food security at a time of pandemic. It is well established that crop yields are usually reduced when nutrients are provided with only natural organic sources, compared to synthetic sources or a combination of them. The most serious and immediate consequence of shifting to total reliance on natural organic sources for crop production in Sri Lanka would be a significant reduction in crop yields, which will threaten the country’s food security particularly at a time when the COVID-19 pandemic has interfered with the international food supply chain. Such a move will also have a devastating effect on livelihoods of vulnerable farmers and will impact foreign exchange earnings through plantation agriculture and horticulture.

Myth of healthier and better-quality food. The belief that foods produced through natural organic sources of nutrients are healthier and are of better quality is a myth. Whether we supply nutrients through synthetic chemical fertilizes or natural organic sources, the crop plants take up nutrients primarily in the same chemical forms, i.e., as inorganic cations and anions. On the other hand, recent studies conducted by researchers at the Centers for Disease Control and Prevention in the USA has shown increasing incidences of disease outbreaks, which the authors linked to Salmonella and E. coli contamination from animal waste used in the production of organically grown food (https://pubmed.ncbi.nlm.nih.gov/28221898/ ). As such, a cautious and careful assessments of such risks should precede a shift towards 100% organic farming for an entire nation, which is quite a gigantic step.

Bulk quantities required. One of the main challenges in supplying plant nutrients through natural organic sources is the requirement of bulk quantities due to their low nutrient concentrations, which makes it costly and inconvenient to use. While synthetic chemical fertilizers are required in rates no greater than a few hundreds of kilograms per hectare (few bags), natural organic sources are required in a few tons per hectare (truck loads) to meet the crop requirement of nutrients. The economic and environmental cost of long-distance transportation offsets the environmental benefits of organic farming unless the organic material is locally available in adequate quantities.

Pollution of freshwater bodies.

A more serious and long-lasting threat with continuous application of natural organic sources for crop production is the buildup of certain nutrients in soil that eventually ends up in water bodies polluting aquatic environments. Natural organic sources such as animal manure have low nitrogen to phosphorus ratio, and their use to meet the crop nitrogen requirement result in over application of phosphorus to crop lands. This has resulted in P-laden soils polluting surrounding water bodies. Many regions across the world are experiencing algal blooms in freshwater lakes (e.g., Great Lakes in North America, Lake Winnipeg in Canada), with phosphorus from intensive agricultural lands contributing to aggravate the problem. Therefore, regulations for restricting manure applications exist in several provinces and states across North America as well as other parts of the world.

 Potentially toxic metals. Potentially toxic metals present in some inorganic fertilizers as impurities (e.g., cadmium in triple superphosphate), poses a threat to human health through polluting drinking water or contamination of food sources, particularly when low quality fertilizers are used. These potentially toxic metals are naturally present in rocks and soils and can remain in the fertilizer after processing of rocks (e.g., rock phosphate), used as raw material. Natural organic sources also contain appreciable quantities of potentially toxic trace elements. Accumulation of toxic metals such as arsenic, cadmium, nickel, selenium, and lead in agricultural soils have been well documented with the application of manure and manure-based composts, which can lead to phytotoxicity and a threat to human health. In this regard, a total shift to natural organic fertilisers could make the situation worse.

My intention is not to undermine the benefits of organic farming, but to caution that more needs to be considered before taking such a huge step as banning all agrochemicals for the entire country. Research findings have shown that the potential environmental and human health threats through the nutrient inputs in agriculture exist even with organic sources. It should also be noted that the early arguments for excluding inorganic chemical fertilizers in the organic farming movement are now being debated by scientists. A concluding statement in a recent review by an eminent Swedish Professor in plant nutrition and soil fertility published in Outlook for Agriculture reiterates that “The decision to ban inorganic fertilizers in organic farming is inconsistent with our current scientific understanding.” (https://journals.sagepub.com/doi/pdf/10.1177/00307270211020025 ).

What then is the best approach?

Integrating synthetic and natural sources – middle path?

The best approach in my view is to continue taking the middle path avoiding the two extremes. Thanks to the many years of excellent research conducted by scientists at the Department of Agriculture and various Research Institutes in Sri Lanka for various crops in different parts of the country, most of the current fertilizer recommendations takes an integrated approach (or the middle path) combining inorganic fertilizer with organic sources that are locally available. The benefits of adding organic sources to soil is unquestionable; not only do they improve soil properties and soil health but sequester carbon and mitigate greenhouse gas emissions in combating climate change. Combining synthetic inorganic fertilizers with natural organic sources provides the flexibility of adjusting the rates as required to supply nutrients in sufficient quantities while improving the soil organic matter and soil health, thus ensuring greater productivity while protecting the environment. It is however important that we address the non-compliance of farmers in the correct use of chemical fertilizers. This can be achieved through comprehensive farmer education and training on the 4R concept of nutrient management (applying the right source at right rate at the right time to the right place) . http://www.ipni.net/article/IPNI-3255 This will improve the fertilizer use efficiency, reduce waste, and minimize nutrient losses to broader environment, which will ensure the most economical outcome, while providing desirable social and environmental benefits essential to sustainable agriculture. Regular soil health assessments and environmental monitoring for pollutants and corrective actions would also be needed.

I have no doubt that the decision to ban the use of synthetic chemical fertilizers in crop production in Sri Lanka, if implemented, will be reversed possibly after a few seasons of cultivation, but that may be too late for the most vulnerable farmers and consumers, and for the maintenance of soil health. I am hoping that professional advisors promoting and supporting the decision to ban the import and use of chemical fertilizers in Sri Lanka, most of whom were my former colleagues, would give more thought to this important decision considering the facts I presented as well as views expressed by other scientists at various forums. If the decision to make Sri Lanka the first country in the world with 100% organic farming remains unchanged, my final appeal is to do it in stages, targeting only the regions that are affected by CKDu as a trial, before implementing it to the whole country without knowing the consequences of such a decision.

 

About the author:

Dr. Darshani Kumaragamage is a Professor in Environmental Studies and Sciences at the University of Winnipeg, Manitoba, Canada, and a former Professor in Soil Science at the University of Peradeniya, Sri Lanka. She has a BSc in Agriculture from University of Peradeniya, M.Phil. in Agriculture from the Postgraduate Institute of Agriculture, Sri Lanka and a PhD in Soil Science from University of Manitoba, Canada. She served the Faculty of Agriculture, University of Peradeniya as a faculty member for 23 years. She currently teaches courses in “Environmental Impacts of Agriculture”, “Environmental Sol Science” and “Human-Environment Interactions” at the University of Winnipeg. Her current research focuses on assessing and mitigating environmental impacts of agricultural activities with emphasis on fertilizer and manure use in crop production. She continues to actively collaborate in agricultural research activities in Sri Lanka and is involved in training students and early career researchers from Sri Lanka at the University of Winnipeg.