Reconstructing Indigenous STEM Knowledge of Jono Salt Farmers for Science Learning Integration in Schools

In the quiet corners of science education, there is a growing recognition that the most profound lessons often begin not in a laboratory, but in the daily lives of communities. For generations, scientists have distinguished between formal, textbook knowledge and the practical wisdom passed down through families and cultures. While school science relies on universal laws and standardized experiments, indigenous knowledge is built through observation, trial, and error, deeply rooted in the specific landscape a community inhabits. This distinction has long created a gap in classrooms, where students struggle to see the relevance of abstract concepts to their own surroundings. The challenge for educators is to bridge this divide, finding ways to show that the intuitive practices of local farmers and artisans are not just traditions, but sophisticated applications of the same physical and chemical principles taught in schools. When these two worlds meet, learning becomes a matter of recognizing the science already present in the world, rather than just memorizing it from a book.

In the village of Jono, located far from the coast in the Grobogan district of Central Java, a group of researchers set out to explore this intersection. They focused on a unique form of salt production that has been practiced for centuries but is now on the brink of disappearing. Unlike the vast coastal salt farms that rely on seawater, Jono farmers extract salt from underground brine wells, tapping into a geological secret hidden beneath the earth. The researchers, led by Fitria Fatichatul Hidayah and her team from Universitas Negeri Semarang, spent three months living among the farmers to document their methods. Their goal was not merely to record a dying craft, but to translate the farmers' intuitive techniques into the language of modern science, creating a bridge that could bring this local wisdom into school curriculums.

The story of Jono salt begins deep underground. The village sits in a valley that was once an ancient sea, trapped between two mountain ranges. Over millions of years, sediment buried the remains of swamp plants, which eventually decomposed to release methane gas, while the ancient seawater remained trapped in the rock layers as a salty brine. The farmers have developed a keen ability to locate these hidden sources without any modern equipment. They look for signs of methane bubbles rising from the ground and feel for pockets of warm earth, where the temperature can reach 40 degrees Celsius, significantly higher than the surrounding air. To confirm a spot, they place a roof tile over the ground overnight; if the tile changes color due to mineral deposits left by evaporating moisture, they know they have found a viable source. This simple test reveals a deep understanding of how minerals concentrate as water evaporates.

Once a source is found, the farmers dig a well, known locally as a belik, reaching depths of up to 45 meters. This is no small feat, accomplished with basic hand tools and the help of specialized workers. To keep the walls from collapsing in the soft earth, they reinforce the shaft with thick bamboo poles arranged in a circle. The farmers also manage the intense heat inside the well by dousing the workers with water, a practical application of cooling through evaporation. To bring the heavy, salty water to the surface, they use a system called timbo-kerek. A container is lowered into the well, and a pulley system allows a single person to lift the heavy load with less effort. The water is then channeled through wooden or bamboo troughs, flowing by gravity into a large storage basin called a brumbung. This basin is covered by a roof to protect the water from rain, which would dilute the salt, and to keep the water still so that dirt and clay can settle to the bottom.

The heart of the Jono method lies in the klakah, a platform made from split bamboo. The farmers select bamboo that is between one and three years old, a specific age range that provides the right balance of strength and porosity. They split the bamboo lengthwise to create troughs and arrange them in rows, elevating them about one meter off the ground. This height is crucial; it allows air to circulate freely around the brine, speeding up evaporation. As the sun beats down on the bamboo, the water slowly turns to vapor, leaving behind salt crystals. The bamboo itself plays an active role in this process. Its porous surface acts like a natural filter, trapping impurities and organic matter from the water, resulting in a cleaner, whiter salt than what is produced in traditional mud ponds. The farmers watch the process carefully, knowing that after five to ten days, depending on the weather, the water becomes so concentrated that salt crystals begin to form on the bamboo surface.

When the crystals are ready, the farmers harvest them by scraping the bamboo with wooden tools. The mixture of solid salt and liquid is then poured through a woven bamboo strainer. This simple tool separates the solid crystals from the remaining liquid, known as bittern. The farmers do not discard this liquid; instead, they store it in large clay jars and use it to make tofu or preserve other foods, demonstrating a zero-waste approach that keeps every part of the process in use. The entire cycle, from digging the well to harvesting the salt, is a testament to a sophisticated understanding of mechanical advantage, fluid dynamics, and chemical changes, all achieved without a single piece of modern machinery.

The researchers translated these observations into formal scientific concepts that are taught in schools. They showed that the farmers' method of finding the well corresponds to the study of geology and hydrology, where gas emissions and temperature anomalies indicate the presence of underground resources. The construction of the well and the use of pulleys illustrate principles of engineering and physics, specifically how forces are managed and how simple machines reduce the effort needed to move heavy loads. The settling of dirt in the storage basin is a practical example of sedimentation, where gravity pulls heavier particles to the bottom. The evaporation process on the bamboo platform demonstrates the principles of heat transfer and phase changes, showing how energy from the sun drives water from a liquid to a gas. Finally, the formation of salt crystals and the separation of impurities provide a clear, real-world example of how solutions become saturated and how substances can be purified through adsorption and filtration.

By mapping these traditional practices to the chemistry curriculum, the study offers a new way to teach science that is grounded in the local culture of Indonesia. This approach is particularly important given that science literacy scores in the country have lagged behind international averages. When students learn about chemical bonds, saturation, or heat transfer through the lens of Jono salt farming, these abstract ideas become tangible and meaningful. The research suggests that integrating such indigenous knowledge into education can make science more accessible and relevant, helping students see themselves as part of the scientific process.

The documentation of Jono salt is also an act of preservation. The number of farmers practicing this craft has dwindled from hundreds in the mid-20th century to just fifty today, with production dropping from thousands of tons to a mere hundred. As the older generation passes, this unique knowledge risks being lost forever. By validating the scientific sophistication of these traditional methods, the researchers hope to give the practice new value and ensure its survival. The study concludes that the wisdom of the Jono farmers is not just a relic of the past, but a living resource that can enrich modern science education, proving that the most advanced understanding of the natural world often begins with a close look at the ground beneath our feet.