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Can organic fertilizer replace chemical fertilizer?

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There is a huge uproar in Sri Lanka regarding the new agriculture policy proposed by the current regime. The Sri Lankan government is to ban importation of chemical fertilizers and other Agrochemicals with immediate effect. The news has made panic waves among the farming communities, academics, research scientists, plantation companies, fertilizer Importing companies, and many others who are involved in agriculture.  If the new policy comes into effect, it could cripple the nation’s agriculture and meet the food demand to feed 21 million people living in the country. The country could run into a severe food shortage, hunger, and collapsing farming communities. This would lead the country to import food from overseas ending up spending billions of dollars, indebted country into further debt. The major export cash crops like tea, rubber, coconut, and spice crops with the attached livelihoods would be at stake. According to statistics, agriculture sector contributes 21% of the GDP and employs roughly 38% of the workforce in Sri Lanka.

 Plant Physiology

Plants require nutrients to grow, and they are taken up mainly by the roots. Nitrogen (N) Phosphorous (P) and Potassium (K) are considered as the main macro nutrients since these three primary nutrients are essential for plant growth and they are required in larger quantities. N, P and K are directly involved in the plant metabolic activity. Calcium (Ca), Magnesium (Mg) and Sulfur (S) are also required by plants in sizeable amounts for their growth. Then there is a bunch of nutrients that are essential for plants for their growth, but these are required in small quantities. Therefore, they are referred as micronutrients. The fertilizers that are primarily imported to Sri Lanka consist of NPK mixtures and they are mixed in different N:P:K ratios based on the crop type and their specific nutrient demand. When the crop is harvested, the harvest could be in the form of leaves (tea), grains (paddy), pods (corn) or vegetables and fruits (chilies, tomato, papaya, pineapple) etc. In agricultural lands the crop is harvested and taken elsewhere for human consumption. As lands are cultivated over a longer period, we basically remove nutrients from the soil in the form of crop and soils become depleted in nutrients. This creates the need for fertilizers to replenish the soil with nutrients and thereby continuously get a higher amount of yield. Nitrogen is provided either by Urea which has 46% of Nitrogen or by Ammonium Sulfate that has 21% of Nitrogen.

Most of the organic compost have around 1% Nitrogen. No organic compost has more than 4% Nitrogen except some artificially concentrated product. So, if organic compost is to replace the amount of nutrients supplied by synthetic inorganic fertilizer, the only way would be to add tons of organic compost to the fields.  This could create practical issues for farmers to walk through their fields, use of any machinery and practicing other agricultural activities. Most importantly, nutrients in organic compost are not readily available to plant roots. In contrast, chemical fertilizers are readily soluble in water and thereby become available for the plants to uptake, soon the fertilizers are applied to the soil. According to plant physiology, different plants need different quantities of nutrients at different time intervals. The challenge in organic compost is that, since they are complex carbon-Hydrogen-nutrient molecules, and as they break down slowly their nutrient release to the plants cannot be timed.

Harmful Effects of Chemical Fertilizer and Agrochemicals

It is a fact that chemical fertilizers and Agrochemicals have harmful impact on people’s health. There are plenty of research and findings to show that Agrochemicals have caused land degradation and created serious health issues among farmers. The real problem that we face in Sri Lanka is the misuse of chemical fertilizer and Agrochemicals. Local farmers apply more fertilizer than what the plants need and apply excessive amounts of pesticides to kill every single pest instead of applying the minimum quantity to keep down the pest population under the economic threshold limit.  Inappropriate use of chemical fertilizers and Agrochemicals has led to soil degradation, loss of fertile topsoil due to erosion. As the soil degrade, most of the fertilizer that is applied to the soil leach down and making them unavailable for the plants. These leached fertilizers are dissolved in water and end up in the streams and finally in ground water, polluting the whole ecosystem.

Organic Compost and Heavy Metals

Organic compost is not always beneficial. It all depends on its composition and what kind of raw materials went into the organic compost production. If the cover crop lopping, farm crop residue, cattle waste, poultry waste and other were used for the preparation of organic compost, then that compost can be called as “good quality organic compost” and should be fine for field application. However, if the original compost was made of city solid waste or any industrial waste, then these could have heavy metals at toxic levels, which could leach into the soil and end up in plants, streams, as well as in the ground water, causing extremely adverse health effects for humans and other living organisms. Regardless how the organic compost is made, they must be tested for the presence of any heavy metals. Heavy metal presence in organic compost is quite common and therefore application of organic compost must be done with great care.

Building a healthy soil

Good organic compost does more towards building a healthy soil than a plant nutrient source. In general, organic compost has exceedingly small amounts of nutrients compared to chemical fertilizers. Organic composts breakdown and form humic acid molecules. Humic acid molecules are the building blocks of humus which can be easily understood as a complex network of carbon hydrogen molecules. Organic compost break down and eventually form in to humus, which is the miracle substance that improve the soil structure and thereby improving soil aeration, soil water holding capacity, creating a perfect micro environment for the beneficial microorganisms that live in the rhizosphere, increasing plant immune system due to the relationship between beneficial microorganisms and roots, increasing the soil cation exchange capacity that help the soil to build more nutrient retention sites and there by minimize the nutrient loss from fertilizer applications. Afterall application of good quality organic compost is all about building a healthy soil.

The World Picture and the Challenges in Sri Lanka

The United States, China, India, Russia and Brazil happen to be the largest food producers in the world. Among those India, Brazil and China have to meet a huge local consumption, whereas the United States exports 25% of their farm products. Interestingly, most of this production is based on conventional agriculture with the chemical fertilizers. Considering total arable land in the world, 17% is used for organic agriculture, and it is 0.8% of the arable crop lands. In some major food producing countries, this number is less than 10%. For instance, it is 8.5% of the total European Union for all organic agriculture.  With the increasing population and other barriers world has understood that the organic based agriculture, especially for staple food crops like wheat, rice, corn, and Barley, can be done minimally.   According to the State of Food Security and Nutrition in the World 2020 report, 690 million people in the world went hungry in the year 2019 and this number was higher than the number in year 2018 due to the impact of COVID-19 pandemic. As Sri Lanka is currently battling with COVID, the task to meet the current local food demand is even more challenging as the whole country is locked down time to time to control COVID.

The correct approach

The correct approach is not to zero the chemical fertilizer and agrochemical usage and totally replace it by organic compost but a holistic approach towards an integrated sustainable agriculture system. It is time for our policy makers to call for a brainstorm session. Get the policy makers, small-scale and large-scale farmers, academics, research scientists, plantation companies, Fertilizer Importers, Crop Exporters, and plan for a long-term goal to minimize the fertilizer imports, increase the use of organic compost, improve our soils, build our soil carbon levels by incorporating good quality organic compost. To achieve the goal, it will need to improve the infrastructure facilities as well. Plan to build organic compost production facilities, increase the number of cover crops, give incentives for farmers for building their soil and making it healthy, building of temperature and humidity-controlled seed storage and fruits and vegetable storage facilities within local communities, improve on the post-harvest technology, have an efficient system of transportation to get the farmer produce to the supermarkets and consumers and thereby to minimize food waste. Improve the supply chain and build a government unit that buys the harvest directly from the farmer so that will remove the middleman as well.

 Time to speak up before it is too late.

The most damage is not done by the corrupted short-cited politicians but by the intellectual intelligent educated few who use their master minds to mislead the government officials and policy makers for their personal greed. It is time for all the farming communities, academics, agriculture research scientists, environmentalists, policy makers, and everyone else involved in the agriculture to speak up before it is too late.

Sumudu Munasinghe
Sumudu Munasinghe
MS Forestry- Soil Nutrient Cycling, West Virginia University, USA. MS Geology- Environmental Geochemistry, University of Oklahoma, USA. BSc. Agriculture- Soil Science, University of Peradeniya, Sri Lanka. Staff Geologist, Soil and Land Use Technology Inc. Maryland, USA

5 COMMENTS

  1. An important article enriched with facts and figures . Thank you very much for your valuable ideas on burden issue in SL..

  2. Very well said. Sri Lankan leaders who are involved in this matter is lack of knowledge to understand the situations like this nature. Also they have to implement correct agricultural procedures to develop the sri lankan soil to get proper results
    Proud to be a brother of you and like to see more articles from you in future too.

  3. Very well said.
    Proud to be a brother of you and like to see more articles regarding the Sri lankan fertiliser matter in future too.

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