19
May
Organic Farm Management Fosters Soil Health and Microbial Diversity that Outperforms Chemical-Intensive Systems
(Beyond Pesticides, May 19, 2026) Research continues to mount on organically managed systems, reinforcing the importance of fostering soil health to ultimately reduce dependency on increasingly expensive petrochemical pesticides and fertilizers, ultimately making food more affordable.
Research published in Journal of Soil Science and Plant Nutrition determines that long-term organic management enhances various soil health indicators to a greater degree than conventionally managed systems. The organic soil qualities include greater microbial diversity, increased microbial biomass carbon (MBC), higher dehydrogenase activity (DHA), and higher alkaline phosphatase activity (ALP), among other favorable outcomes.
The positive impacts of organic land management on soil health, microbial diversity, and biodiversity cannot be overstated, given the existential threats imposed on the planet by petrochemical-based agricultural practices.
Methodology and Main Findings
This study was conducted at the Central Arid Zone Research Institute (CAZRI) in Rajasthan province, India. The annual average rainfall for this region is 100 mm (about 4 inches) and 450 mm (18 inches), with nearly 90 percent of that rainfall falling between June and September.
Both the organic and conventional sites consist of loamy soils and shared agro-climatic conditions. The organic site was established in 2008 and certified by the Rajasthan State Organic Certification Study, which has been managed exclusively with organic inputs for over 14 years. To avoid water contamination by synthetic pesticides and fertilizers, 4-foot-deep trenches were dug to separate the test site from neighboring chemical-intensive fields. The baseline soil properties for both fields are similar, with the largest difference in available phosphorous 20 times higher in organic than in conventional fields, due to legacy conditions. For more details on the difference in conventional and organic land management in this study, please see page 4 under Subsection 2.2: Field Experiment.
The experiment on the study sites was organized into a “split-plot†design, with 16 plots for both the organic and conventional systems. The seasons in India support Kharif (June to July) crops requiring high heat and water during monsoon-season and Rabi (October to December) crops needing cooler climates during the winter season. The soil was tested for crop seasons starting in Rabi 2021 and ending in Kharif 2023, with samples collected from the rhizosphere zone of the system at three growth stages per crop (30 days after sowing, 60 days after sowing, and at harvest). Each experimental plot was replicated four times based on the following crop rotations:
- T1 (Fenugreek–Mung bean–Psyllium–Sesame),
- T2 (Fenugreek–Sesame–Psyllium–Mung bean),
- T3 (Psyllium–Mung bean–Fenugreek–Sesame), and
- T4 (Psyllium–Sesame–Fenugreek–Mung bean).
In terms of soil health outcomes and organic land management, researchers arrived at the following conclusions based on their analysis of the data:
- Soil health status in organic systems outperformed conventional systems across the board, including:
- Organically managed systems consistently support higher bacterial and fungal counts, with peak microbial populations across regardless of the crop season.
- Organic plots have 12-32 percent higher microbial biomass carbon (MBC) than conventional plots when soil samples were gathered 60 days after sowing (60 DAS), ultimately declining at harvest due to soil disruption.
- Organic systems show higher dehydrogenase activity (DHA), increasing 6-71 percent over conventional depending on the season. DHA is significant in terms of the enzymes they produce that are vital for cellular energy production, metabolism, photosynthesis, and other biochemical processes critical to soil health.
- The alkaline phosphatase activity (ALP) is 3-56 percent higher under organic land care relative to conventional systems. ALP is an important indicator of microbial diversity in the soil, as microorganisms mineralize (breaks down) organic phosphorus (P) into plant-available nutrients and facilitate P-cycling throughout the soil system.
- Fluorescein diacetate hydrolytic activity (FDA) was 34-70 percent higher under organic land management depending on the season. FDA activity is used to estimate total microbial activity and functional diversity in soil samples.
- Organic management appears to stabilize microbial activity across monsoon and winter crop seasons, whereas conventional plots showed more sensitivity to seasonal climate swings. In other words, biological activity in the soil is significantly higher than conventional systems, since the baseline higher MBC provides better continuity of microbial habitats (e.g., the soil systems).
- Due to the legacy use of organic-compliant fertilizer over 14 years prior to the study, the organic plots have roughly 20 times more available phosphorus than conventional sites.
Previous Coverage
There is a wide range of previous scientific investigations highlighting the dangers of synthetic pesticide and fertilizer use for soil health, as well as the organic alternative with proven benefits.
A study of the effects of flooding on aquatic-terrestrial pesticide transfer, published in Archives of Environmental Contamination and Toxicology, finds heightened risks to riparian zone ecosystems as flooding frequency increases with climate change. Riparian zones, recognized as biodiversity hotspots, “are increasingly subjected to various stressors, including chemical contaminants such as pesticides,†the authors state.  In analyzing pesticide residues following simulated flooding within a controlled experiment, the researchers find: “[S]ix pesticides were detected exclusively in riparian root-zone soil following four repeated flooding events. Our findings indicate that both longer flood durations and repeated flooding events tend to increase the total concentration of pesticides in the riparian root-zone soil. These results demonstrate that flooding promotes the movement of pesticides from streams into adjacent riparian areas. As flood frequency and intensity are expected to increase due to climate change, the significance of this transport pathway is likely to increase, with potential consequences for riparian biodiversity and habitat quality.†(See Daily News here.)
In a novel, continent-wide study of soil biodiversity throughout Europe published in Nature, researchers find 70% of the sampled sites contain pesticide residues, which “emerged as the second strongest driver of soil biodiversity patterns after soil properties,†particularly in croplands. This study, however, highlights how pesticides alter microbial functions, including phosphorus and nitrogen cycling, and suppress beneficial taxa, such as arbuscular mycorrhizal fungi and bacterivore nematodes. In analyzing 373 sites across woodlands, grasslands, and croplands in 26 European countries, and examining the effects of 63 pesticides on soil archaea, bacteria, fungi, protists, nematodes, arthropods, and key functional gene groups, the data reveal “organism- and function-specific patterns, emphasizing complex and widespread non-target effects on soil biodiversity.†As the authors state, “[T]o our knowledge, ours is the first study to demonstrate the relative importance of pesticides in comparison to soil properties, ecosystem type and climate at a continental scale.†(See Daily News here.) In a separate literature review and data analysis of almost 2,000 soil samples, the authors of a recent study found negative effects of pesticide exposure on the presence of plant-beneficial bacteria (PBB) in soil, particularly bacteria with plant growth-promoting traits that are essential for crop productivity. (See Daily News here.)
The intersection of the adverse effects of pesticides and fertilizers on biodiversity is also highlighted in peer-reviewed literature. A recent study of earthworms published in Environmental Science & Technology highlights how chemical mixtures can have both synergistic and species-specific effects, threatening the soil microbiome and overall soil health. In exposing two species, Eisenia fetida and Metaphire guillelmi, to the weed killer glyphosate alone and in combination with urea, a form of synthetic nitrogen fertilizer, the researchers find enhanced toxicity with co-exposure as well as varying health effects between the two species. These results emphasize the need to test a wide variety of nontarget organisms for impacts from environmental contaminants, since species, even within the same genus or family, can exhibit vastly different effects. (See Daily News here.) On the subject of earthworms, a study published in Environmental Toxicology and Pharmacology evaluates the toxicity of environmentally relevant levels of three fluorinated pesticides (fluxapyroxad, fluopyram, and bixafen) through a 56-day soil exposure experiment. The dose- and time-dependent results reveal that effects on growth and reproduction occur at elevated concentrations, with weight loss and reduced offspring occurring from energy depletion and reproductive organ damage. Other implications escalate with concentration as well, including antioxidant system failure and DNA damage. As the authors summarize, “These findings highlight the mechanisms of fluorine-containing pesticide toxicity in earthworms, emphasizing their potential to disrupt soil ecosystems.†(See Daily News here.)
Meanwhile, research by the Rodale Institute, Ohio State University, and Tennessee State University, published in Soil Science of America Journal, documents that organic grain cropping systems contain higher concentrations of total nitrogen and soil organic carbon, exceeding those found in conventional, chemical-intensive systems. This study is an extension of the Rodale Institute’s Farming System Trial (FST), a 40-year-long field study with the overarching goal of “[a]ddress[ing] the barriers to the adoption of organic farming by farmers across the country.†(See Daily News here.) Another study published in Environmental Technology & Innovation finds that organically managed coconut farms significantly improve soil health across numerous markers when compared with conventional (chemical-intensive) plantations. (See Daily News here.) Research published in Microbiological Research finds that organic farming enhances microbial diversity in citrus orchard soil systems, both in terms of nutrient cycling and aiding in the development of more complex microbial networks pivotal to biodiversity. (See Daily News here.)
A study published in Scientific Reports highlights the benefits of organic agriculture in comparison to different farming systems over five years on four crops (maize, tomato, faba bean, and potato). “Soil carbon sequestration is a long-time storage of carbon in soil which represents 70% of the carbon in land,†the authors note. “Therefore, the main aim of this study is to investigate the effect of the agricultural practice systems on the soil carbon sequestration and properties, productivity, water consumption, soil carbon sequestration, CO2 emission and cost of some agricultural crops.†As a result, the experiment reveals that, compared to chemical-intensive farming, organic methods enhance soil properties, reduce water consumption, provide higher yields and higher soil carbon sequestration, reduce CO2 emissions, and achieve the highest total net profit for all four crops after five years. (See Daily News here.) In the Journal of Environmental Quality, researchers at the U.S. Department of Agriculture (USDA) published a noteworthy report that a 4-year organically managed corn-soybean-oat system reduces nitrogen (N) loads by 50 percent with corn and soybean yields “equivalent to or higher than conventional [chemical-intensive] in most years.†The findings from a 7-year study comparing nitrate loss in organic and chemical-intensive management found that organically managed perennial pasture reduced nitrogen loads significantly. The study, which focused on nitrate pollution in agriculture that harms biodiversity, threatens waterways, drinking water, and public health, and releases nitrous oxide (an extremely potent greenhouse gas), was conducted at USDA’s National Laboratory for Agriculture and the Environment. (See Daily News here.)
Call to Action
You can support the continuation of this critical research by calling on your elected officials in the U.S. House of Representatives and Senate to endorse and sponsor the newly reintroduced Organic Science and Research Investment (OSRI) Act. (See Action of the Week here.) Learn more about your potential exposure to toxic pesticides and chemicals in over 90 non-organic crops, vegetables, fruits, nuts, and related items in the Eating With a Conscience database.
You can also take action by telling EPA, FDA, and Congress that regulations must consider the effects of pesticides in the context in which they are used and with reference to the organic alternative. Â
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
