Traditional Fertilizers Beat Out Industrial Chemicals in Soil Health Test

As the Indian population grows, ramping up food production is crucial—but so is preserving the sustainability of the ecosystem so that food production can persist into the future. Since the 1960s, the Indian government has subsidized chemical-intensive fertilizers to enhance crop growth.

Now, new research from western India has shown that in a head-to-head test of soil properties, organic fertilizer based on Traditional Ecological Knowledge encouraged better soil structure and fertility, even during drought periods. Only about 10%–15% of farms in the region studied use the traditional fertilizer, but studies like this one could incentivize more sustainable agricultural practices.

Time-Tested Fertilizer

For years, Seema Sharma, an assistant professor of environmental sciences at Krantiguru Shyamji Krishna Verma Kachchh University, had heard stories from farmers that a traditional organic fertilizer cultivated more healthy and sustainable soils than chemical approaches. The traditional fertilizer recipes and application timing were even written in Vedic scriptures more than a thousand years ago, she said.

“The research was already there because the ancient people did their research long ago, but when it comes to the scientific community, you need research that is in a peer-reviewed journal.”

A few years ago, Sharma was at a global conference discussing traditional agricultural strategies from western India, a semiarid region of the country. She said other researchers asked whether science supported the stories that the traditional approach was better for soil health. “The research was already there because the ancient people did their research long ago,” she said. “But when it comes to the scientific community, you need research that is in a peer-reviewed journal and then finally verified.”

Sharma realized that she needed to put the traditional fertilizer to the test.

Traditional and Chemical Fertilizers Go Head-to-Head

Soil health broadly comes down to key physical, chemical, and biological characteristics. In a 2020 study, Sharma compared the biological characteristics of soils fertilized with chemicals and soils fertilized with a combination of farmyard compost and jeevamrutha, a fermented liquid of cow dung, cow urine, a form of cane sugar called jaggery, gram flour, and soil. Traditionally fertilized soils showed greater microbial diversity—a sign of nutrient availability, soil health, and resilience—than chemically fertilized soils did.

In a new study published in PLOS Sustainability and Transformation, Sharma empirically tested and compared physical and chemical characteristics of traditionally and chemically fertilized soils. Characteristics included maximum water holding capacity, density, electrical conductivity, and pH.

For the experiment, Sharma tested soils from 10 farms in the Kachchh district of Gujarat in western India using commercial chemical fertilizers and 10 farms in the same area using traditional fertilizer. She tested the soils before, during, and after the crop harvest over six cropping seasons and 3 years.

Back in the lab, Sharma found that the water-holding capacity of the traditionally fertilized soil was higher than in soils using chemical fertilizers, even throughout two seasons of drought. The more water the soil can retain, the less it leaches nutrients, making it more sustainable in the long term. Soils using traditional fertilizer also had lower soil density, which is crucial for plant rooting, and more stable pH levels throughout the drought periods, even though dry conditions tend to increase salinity. Soils treated with chemical fertilizers tended to have higher pH over time, which can decrease the solubility of nutrients. Overall, jeevamrutha worked better than chemical fertilizers for improving the soil structure and fertility.

Sudeshna Bhattacharyja, a soil scientist at the Indian Council of Agricultural Research–Indian Institute of Soil Science, said she wasn’t surprised by the results because similar studies have been carried out around the country, but having data from western India, where the soil is drier and more salinated, gave a broader understanding of what traditional organic fertilizers can do. “The important thing is the area where the study has been done,” she said, because the data can help inform models for better predictions of soil health under different management systems. “If we have ground data from a different corner of the country with a different agroclimatic situation, that will be really good for the future.”

Promoting Sustainable Agriculture

Sharma said that her next steps are to test whether the crop yields using the traditional fertilizer can be as high as those with chemical fertilizers. Changing from chemical to organic fertilizers can result in yield losses for several years, so farmers must know that the transition will be worth it. “The farmers that I work with are now telling me that we have yields that are on par with the common system of chemical farming,” she said. “But that study has to be done.”

—Andrew Chapman (@Andrew7Chapman), Science Writer

Citation: Chapman, A. (2022), Traditional fertilizers beat out industrial chemicals in soil health test, Eos, 103, https://doi.org/10.1029/2022EO220169. Published on 29 March 2022.

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