Performance and Productivity of Ocimum species under an Aonla-based Agroforestry System in the Submontane low hill zone of the North-Western Himalaya

In the foothills of the Himalayas, where the land is steep and the soil is precious, farmers face a constant challenge: how to grow enough food and medicine without exhausting the earth. For centuries, the solution has often been to mix different types of plants together, a practice known as agroforestry. Instead of planting a single crop in a vast, empty field, farmers grow trees alongside smaller plants. The trees provide shade and structure, while the smaller plants fill the gaps, creating a busy, layered ecosystem that uses sunlight and nutrients more efficiently. Among the most valuable trees in this region is the aonla, or Indian gooseberry, a fruit known for its high vitamin C content and deep roots in traditional medicine. Alongside it grows tulsi, a sacred herb with a distinct aroma and powerful medicinal properties. While both plants are valuable on their own, scientists have long wondered if they could thrive together, and if adding natural soil boosters like compost could make them even more productive. The question is not just about growing more plants, but about finding a way to farm that keeps the soil healthy and the farmer's income secure for the future.

A team of researchers set out to answer these questions in the sub-montane low hill zone of Himachal Pradesh, India. They established a study in an existing orchard of eleven-year-old aonla trees, creating a living laboratory where they could test how different types of tulsi would perform under the tree canopy. They chose three distinct varieties of the herb: Ram tulsi, known for its spiritual significance; Shyam tulsi, a green-leaved variety; and Bhabri tulsi, a bushier type. To see how the soil could be improved, they divided the orchard into plots and applied different treatments. Some plots received standard chemical fertilizers, others received farmyard manure, a third group received vermicompost, which is nutrient-rich compost made by worms, and a final group received no fertilizer at all to serve as a baseline. Over the course of a year, from 2024 to 2025, the researchers carefully measured how tall the plants grew, how many leaves they produced, and how much essential oil could be extracted from their foliage. They also dug up soil samples to see how the different treatments changed the earth's chemistry and calculated the financial returns for each method.

The results painted a clear picture of what works best in this specific environment. The plants that received vermicompost grew significantly taller and produced far more leaves than those in the control plots or those treated with chemical fertilizers alone. Among the three varieties, the Bhabri tulsi proved to be the most vigorous in terms of physical growth, reaching heights of nearly ninety centimeters and producing over seven hundred leaves per plant when fed with the worm compost. This variety also developed the heaviest root systems and the most leafy biomass. However, the story changed slightly when the researchers looked at the essential oil, the valuable liquid used in medicines and perfumes. While the Bhabri tulsi grew the most, the Ram tulsi variety produced the highest amount of oil, yielding over nine kilograms per hectare when grown with vermicompost. The Shyam tulsi variety, while not the tallest or the most oily, showed the highest levels of chlorophyll, the green pigment that helps plants make food from sunlight, suggesting it was very efficient at photosynthesis.

Beyond the plants themselves, the study revealed how these farming methods affected the ground beneath them. The soil under the trees remained stable, with no significant changes in its acidity or salt levels, which is a good sign that the system is balanced. However, the soil did become richer. The plots treated with organic matter, particularly the vermicompost and the farmyard manure, showed a marked increase in the amount of organic carbon and the availability of essential nutrients like nitrogen, phosphorus, and potassium. This means the soil was becoming more fertile and better able to support plant life without the need for harsh chemicals. The researchers found that the combination of aonla trees, tulsi, and vermicompost created a synergistic effect where the whole system was greater than the sum of its parts. The trees provided a microclimate that protected the herbs, while the herbs and the organic fertilizers helped nourish the soil for the trees.

The economic analysis of the study confirmed that this approach is not just ecologically sound but also financially smart. While the cost of growing the herbs with vermicompost was higher due to the expense of the compost, the returns were substantial. The treatment combining aonla trees, Ram tulsi, and vermicompost generated the highest total income, bringing in over two hundred and sixty thousand rupees per hectare. Even more impressive was the benefit-cost ratio for the treatment using farmyard manure with Ram tulsi, which showed that for every rupee spent, the farmer could expect to get back nearly four rupees. This suggests that while the initial investment in high-quality organic inputs might be steep, the long-term payoff in terms of yield and soil health is significant. The study concludes that integrating these medicinal herbs with fruit trees, especially when supported by organic nutrient sources, offers a viable path forward for farmers in the region. It provides a way to maximize the use of limited land, improve soil health, and generate multiple streams of income, turning a simple orchard into a resilient and productive ecosystem.