A rich harvest, naturally

Conservation scientist Iris Berger from Cambridge, U.K., has spent nearly 14 months in Andhra Pradesh surveying farmers who have turned away from the Green Revolution. Using an interpreter, she consulted 70 farmers who have replaced synthetic fertilisers and pesticides with blends of cow dung, urine, and other natural substances to nourish their fields of paddy, pulses, and vegetables, and an equal number of farmers who continue to rely on agrochemicals. Berger also drew on the expertise of ornithologists to observe birds across the farms and nearby forests, record their calls, and catalogue each bird species.

The farm surveys and bird-tracking exercises have now produced the strongest evidence to date that zero budget natural farming (ZBNF), which relies almost entirely on natural substances, is a viable alternative to agrochemicals-based conventional farming. In one of the largest assessments yet of ZBNF practices, Berger and her colleagues have found that the average crop yields on ZBNF farms are almost the same as on conventional farms. The clincher: economic profitability on ZBNF farms, after budgeting for all input costs, is more than double (about 123%) that on conventional farms.

"The outcomes we have documented are highly promising," says Berger, a researcher at the University of Cambridge and lead author of the study published in Nature Ecology & Evolution in September (bit.ly/ZBNF-Andhra). "Andhra Pradesh's experiment, if we can call it that, suggests that ZBNF under certain conditions is a compelling alternative to expensive and environmentally unsustainable farming."

The study comes against the backdrop of efforts to lower dependence on agrochemicals and an expanding global market for organic produce. But almost all previous evaluations of natural farming practices in the country had relied on field plot experiments, primarily by agricultural scientists, or on small farmland patches.

"Field plot experiments provide valuable insights into the biophysical impacts; they can answer the question: if ZBNF is executed perfectly, how does it affect the yield and soil health?" says Berger. "But they can't tell us anything about the effects of large-scale adoption such as Andhra's transition towards ZBNF."

This gap in real-world evidence has been particularly pressing amid concerns about how to feed a growing population while safeguarding biodiversity and healthy ecosystems. Conventional farming using agrochemicals has boosted crop yields but also contributed to biodiversity loss, soil degradation, and has introduced potential risks of chemical exposure for humans and wildlife. Some environmental researchers have also been concerned that the extra land needed for organic farming to achieve adequate yields might cancel out any gains made on biodiversity, with more land coming under cultivation.

These challenges are acute in India, where cultivated croplands have expanded over the past five decades: nearly 60% of the country's land is currently under cultivation. Alongside that expansion, the diversity of birds and other species has declined on cultivated lands. And millions of small landholder farmers across the country strive to maintain livelihoods. A 2021 National Sample Survey had suggested that 50% of India's farmers are in debt, mainly due to increasing costs of chemical fertilisers and pesticides.

Faced with these pressures, the Andhra Pradesh government has since 2016 encouraged farmers to adopt ZBNF, a concept proposed by Maharashtra-based agricultural scientist Subhash Palekar in the 1990s, with three key elements. Jiwamrita is a fermented blend of cow dung, cow urine, jaggery, pulse flour, and soil applied to the fields to stimulate earthworms and beneficial microbes. Beejamrita is a seed treatment using dung and urine formulations, intended to protect seedlings from disease. Finally, mulching involves covering the topsoil with crop residues or organic waste to help retain moisture, recycle nutrients, and build organic matter. Jiwamrita and Beejamrita add only small amounts of nutrients compared to chemical fertilisers, but their main value lies in boosting soil microbes, earthworms, and plant health. Jiwamrita, for instance, can increase nitrogen-boosting bacteria thousands of times while Beejamrita shows evidence of protecting seedlings and improving germination, a 2020 study on ZBNF had noted.

But ZBNF has also encountered some scientific criticism. Sarah Duddigan, an environmental scientist at the University of Reading in the U.K. and her colleagues had acknowledged in a 2022 paper (bit.ly/ZBNF-Duddigan) that there is a "genuine danger that the success of the social movement fueling the adoption of ZBNF practices has become out of step with science that supports its efficacy". A 2020 study (bit.ly/ZBNF-challenges) by researchers at the University of Aberdeen had suggested that while ZBNF may suit low-income farms, its strong promotion to high-income farmers could temporarily reduce national food production.

And researchers with the Indian Council of Agricultural Research (ICAR) National Academy of Agricultural Research Management, Hyderabad, had in 2019 documented (bit.ly/ZBNF-mixed-yield) mixed yields: ZBNF farmers in Karnataka harvested better yields in finger millet but lower yields in paddy and sugarcane, while paddy yields improved in Andhra Pradesh.

Amid such mixed scientific evidence, farmer interest has surged. Adoption in Andhra Pradesh has grown at a remarkable pace. A 2024 study (bit.ly/ZBNF-Nabard) by the National Bank for Agriculture and Rural Development estimated that the number of farmers in Andhra Pradesh who adopted ZBNF spiked nearly 19-fold from 40,000 in 2016-17 to over 750,000 by 2021-22. The State reckons that all of its estimated six million farmers would have switched to ZBNF between 2027 and 2030. Over the past decade, the ICAR has also worked with Chhattisgarh, Haryana, Himachal Pradesh, Karnataka, Kerala, Madhya Pradesh, and Tamil Nadu, among others, to introduce ZBNF to local farmers.

For their study, Berger and her colleagues sampled 13 ZBNF, 13 conventional agrochemicals-based, and 26 forest landscapes between 2021 and 2023, collecting data on yields and profits and documenting bird diversity across those farms and forests.

They found that ZBNF landscapes on average maintained crop yields while sharply reducing input costs, delivering substantial profit gains for farmers even without market premiums for their ZBNF produce. These benefits were observed across hundreds of fields, although yields varied in certain locations, which the researchers say highlights the importance of local conditions and management practices. "ZBNF has positive effects on average, but more work needs to be done to understand under what conditions it delivers positive effects and under what conditions it doesn't," says Berger.

The researchers found that ZBNF also had a marked positive impact on farmland birds. Overall, fruit-, insect-, and vertebrate-eating birds were 49% to 160% more abundant on ZBNF fields than on conventional farms. They documented 114 bird species on agricultural landscapes, of which 48 were not found in forests. Among those 48, 13 birds were exclusively found on ZBNF fields, compared with only four birds on conventional farms. The absence of chemical fertilisers, pesticides, or herbicides on ZBNF fields may have contributed to this greater abundance, likely due to higher prey availability. Insect-eaters included bee-eaters, pipits, and warblers, while kingfishers, herons, and egrets were among the vertebrate-eaters.

Ornithologists Ajit Kamble, Varsha Raj, and Sayuj Nair spent hours in the fields and forests, noting every bird they encountered, while bioacoustics expert Viral Joshi at the Indian Institute of Science Education and Research Tirupati verified each species by its call. "More insect-eating birds in the ZBNF fields would likely mean their pest control services to be enhanced, which in turn would improve yields and economic gains for farmers," says Lynn Dicks, Professor of Ecology at the University of Cambridge, who supervised the study. The researchers caution that quantification of such gains from greater bird diversity should be a goal of future studies.

Perhaps most strikingly, the researchers say, ZBNF weakened the usual trade-offs between productivity and biodiversity. While higher yields and profits on conventional farms corresponded with declines in bird populations, in ZBNF fields, bird densities declined less sharply with increasing yields and profits.

The study's findings provide evidence for a scalable path for natural farming in tropical regions. "Most research on organic and alternative farming systems until now has come from three regions — Europe, North America, and Australia — all in the temperate zone," says Divya Veluguri, a researcher studying sustainable food systems and Executive Director of the Deccan Development Society, a non-government entity in Telangana that has been working with local communities promoting traditional knowledge in farming for four decades. "We now have high-quality evidence from a tropical region," says Veluguri, who was not associated with the India-U.K. study.

The U.K. researchers believe the findings could help guide policy decisions in West Africa and Latin America, where countries are examining plans to expand natural farming. However, they note that maximising benefits from ZBNF will require supportive policies, such as removing subsidies for synthetic fertilisers, creating ZBNF-specific value chains, and integrating conservation planning into farmland management.