Spatial Assessment and Mapping of Soil Fertility Status in Chaurjahari Municipality, Rukum West, Nepal

In the steep, terraced hills of Nepal, the soil beneath a farmer's feet is not a uniform blanket but a patchwork quilt of hidden strengths and weaknesses. This landscape, where families grow food on narrow strips of land carved into mountainsides, relies entirely on the earth's ability to provide nutrients like nitrogen, phosphorus, and potassium. These nutrients are the invisible fuel for crops, and when they are missing or imbalanced, harvests suffer. Scientists call this uneven distribution "spatial variability," a concept that simply means the quality of the ground can change dramatically over short distances, sometimes even between two neighboring fields. For decades, farmers in these regions have often applied fertilizer based on broad, general advice for entire districts, a strategy that risks wasting money on land that already has enough nutrients while leaving other fields starving. To fix this, researchers need a clear, local picture of what is actually in the soil, a map that shows exactly where the earth is rich and where it is poor, allowing for care that is tailored to the specific needs of each patch of ground.

In the Chaurjahari Municipality of Rukum West, a researcher set out to create this kind of detailed picture. They walked through nine different administrative wards, visiting fifty-two specific fields belonging to local farmers. At each location, they collected a sample of the top twenty centimeters of soil, carefully recording the exact spot with a global positioning system. Back in the laboratory, they tested these samples for five key indicators of soil health: how acidic or alkaline the soil is, how much organic matter it contains, and how much nitrogen, phosphorus, and potassium are available for plants to use. The goal was not just to take an average of the whole area, but to understand the unique story of each field and how those stories connect across the landscape.

The results revealed a soil landscape that is surprisingly mixed. On average, the soil in the municipality is neither too acidic nor too alkaline, sitting comfortably in a neutral range that is generally good for growing crops. The land also appears to have plenty of phosphorus, a nutrient that plants need to grow strong roots and seeds; nearly all the samples showed medium to high levels of this element. However, the story changes dramatically when looking at other nutrients. The soil is largely poor in organic matter, which is the decomposed plant and animal material that holds water and feeds microbes, and it is also low in nitrogen, the primary driver of leafy green growth. More than seventy percent of the fields tested had low or very low levels of organic matter, and nearly sixty percent were low in nitrogen. This suggests that the soil is struggling to recycle its own nutrients, likely because crop residues are not being returned to the ground or because the steep terrain makes it difficult for organic material to build up.

The most striking finding, however, concerns potassium, a nutrient essential for plant health and disease resistance. The researcher found that potassium levels were all over the place, varying wildly from one field to the next. In fact, nearly half of the samples tested were rated as very low in potassium. This nutrient was not spread evenly across the municipality; instead, it formed a distinct pattern. The northern, higher-elevation parts of the area were particularly depleted, with large clusters of fields showing severe shortages. In contrast, the southern and southwestern areas had much better potassium levels. This clear geographic split means that a blanket recommendation to add potassium to the entire municipality would be inefficient; farmers in the south might not need it at all, while those in the north are in urgent need of it.

The study also uncovered a technical detail that adds a layer of caution to the findings. The researcher noticed that the numbers for total nitrogen were almost perfectly linked to the numbers for organic matter, suggesting that the nitrogen values were not measured directly but were instead calculated from the organic matter data using a standard formula. While this does not invalidate the findings about organic matter, it means the specific nitrogen numbers should be treated as estimates based on that relationship rather than independent measurements. Additionally, the data showed that for most nutrients, the variation between fields was so random and fine-grained that it was difficult to draw smooth, continuous lines of fertility across the map. The soil properties changed so quickly over short distances that a single sample could not reliably predict the conditions of the field right next to it. This is likely because the farming practices, such as how much manure a farmer adds or how they manage their terraces, differ from one household to the next, creating a complex mosaic that is hard to smooth out.

Despite these complexities, the study provides a vital roadmap for the future of farming in Chaurjahari. It shows that the most pressing need is to rebuild the organic matter in the soil, particularly in the central and southern wards where it is lowest, perhaps by encouraging farmers to compost more crop residue or use green manure. It also highlights that potassium is the most critical missing nutrient in the northern highlands, where targeted application could make a significant difference. The researcher suggests that instead of treating the whole municipality as one big block of land, agricultural planners should focus on these specific ward-level differences. By using the maps they created, which show exactly where the soil is struggling, local officials can guide farmers to apply the right amount of fertilizer in the right place. This approach moves away from guesswork and toward a system where every field gets the specific care it needs, ensuring that the land remains productive for the families who depend on it.