The municipality of  Sergio Osmeña, Sr. is situated on the northeastern part of the province of Zamboanga del Norte. it is located approximately forty-eight (48) kilometers east of Dipolog City the Provincial Capital, or two hours ride from the City of Dipolog. The town is accessible by four wheeled vehicles through the National Highway connecting Zamboanga del Norte to its twin province, Zamboanga del Sur. Technically, the municipality is described as follows: 

“ From the intersection of longitude 123-10-00 and latitude 8-20-00 in a straight line due east until it intersects the provincial boundary of Misamis Occidental and Zamboanga del Norte with longitude 123-33-30: thence due south to latitude 8-13-00; thence due west until it intersects longitude 123-10-00; thence due north until reaches to the point of beginning.” 

In shape, it appears to be rectangular. It is bounded on the north by the municipalities of Pres. Manuel Roxas, Katipunan, Polanco, Piñan and Mutia; on the south by Province of Zamboanga del Sur; on the east by the Province of Misamis Occidental; and on the west by the municipalities of Jose Dalman and Siayan.  

III. Physical Characteristics

A. Land Area

At, present, the Municipality of Sergio Osmeña, Sr. has 55,644 hectares of land within its juridical boundaries. These are distributed among its thirty-nine (39) barangays. Categorically, these land areas are identified as follows 13,986 hectares Strategic Crp Development zone; 12,787 hectares Agro-Forestry Zone; 6,351 hectares for Remaining Network protected areas for agricultural development; 18,416 hectares forest and watershed areas; and 3,104 hectares built-up areas.

Like the rest of the province, the land area of the municipality of Sergio Osmeña, Sr. is mostly agricultural with 32,549 hectares being cultivated for crop production and the remaining 2,174 hectares classified as open grassland or pastureland. The settlement areas on the other hand include the areas used for residential, commercial, institutional, industrial and other purposes.

  B. Topography

    The topographic situation of the Municipality of Sergio Osmeña ranges from plain, slightly rolling, and hilly to mountainous. The plain areas, slightly rolling to rolling areas constitute approximately sixty  percent (60%) of the total land area. The severely rolling with an estimated height of approximately 2,850 feet above sea level constitute forty percent (40%) of the total area. 

    The slope of the land is one of the factors considered in determining the suitability of lands for urban development as well as its capabilities for agricultural cultivation. The different slope categories used as basis for settlement planning are the following: 

    Levels to moderately sloping areas that have good soil characteristics are favorable for cultivation and urban utilization. Strongly sloping to mountainous condition renders the land highly prone to soil erosion and unfavorable for agricultural production and urban development. 

    There are approximately forty percent (40%) of the total land area of the municipality that have a slope of eighteen percent and above. These areas are strongly sloping to mountainous. Most of these areas are open grasslands  although several patches of these are planted with diversified crops. Because of the soil characteristics in these areas, these are best suited to the establishment of tree  Farms to keep the soil from further erosion. These areas are mostly situated at barangay Tinago, Bagumbayan, and the forest areas near the boundary between the municipality of Pres. Manuel A. Roxas and Siayan, all within the Province of Zamboanga del Norte. Due to its soil characteristics, these are presently being reforested, while some portions are left as open grassland. 

    Areas having slopes of zero to less than eighteen percent (0-18%) constitute approximately sixty percent (60%) of the total land area. These are currently planted with diversified crops like palay, corn, legumes, vegetables, root crops and tree species.

  C. Erosion Potential

     Soil erosion is a process by which soil particles are detached and transported by run-off water. The slope of the land, intensity of rainfall, vegetative cover, land use of soil affect this.

      The terrain of Sergio Osmeña, Sr. is such that approximately 40% of its total land are are characterized as undulating hills to steep lands. These steep lands and the lack of forest covers contribute to the occurrence of severe run-off. Besides, big rivers such as Salug, Layawan, Yabu and Dicayo rivers traverse the municipality. these rivers and numerous streams and creeks often overflow its bank during the rainy months. 

    To minimize erosion, farming activities especially the cultivation of annual crops  on slopes of over 18% is discouraged. Farmers  instead are encouraged  in establishing tree farms on these areas to hold the soil and to minimize severe soil damage. 

D. Soils

Basic Soil Types

    Knowledge of the basic soil types and its characteristics existing in an area is necessary selection for the best use of the land. It is also needed for the selection for the crop most suitable for cultivation. 

    Records of the Soils Division, Department of Agriculture show that the soil of Sergio Osmeña, Sr. is classified as belonging to the Adtuyon Clay Loam, La Castellana-Jessa-Luisiana Complex, and Mountain soil undifferentiated. These soil types were formed from residual soil of volcanic rock and pyroclastic. The soil description found in horizon A is nearly dark brown, dark yellow brown, moist clay loam, no mottles, moderately weak, fine sub angular block structure, many fine to medium continuous random tabular open pores sticky plastic and firm, presence of few stones partially with rock fragment  sands, few fine to medium crystalline quarts; many fine to medium rocks; diffused smooth boundary. (ZNLREP I, 1984-85) 

    The amount of organic matter, available phosphorous and potassium in the soil reaction (PH) are the indicators of inherent fertility of the soil. Based on the results of the soil analysis of the samples collected at different areas of the municipality, showed that the average PH is 5.8 percent of the organic matter, 1.75% available phosphorous, 0.23 parts per million (ppm), and available potassium 112.3 pm. The average PH is within the range of the requirements of most crops. The organic matter content and available phosphorous are considered to be low while, the available potassium is considered to be average. The inherent fertility of the soil in the municipality is classified as fair. 

    Specifically, fifty percent (50%) of the land area of the municipality especially those  in the northern part of the municipality is classified as mountain soil undifferentiated. La Castellana-Jassan Luisiana complex type is mostly found in the southern part of the municipality near the boundary between the municipality and the province of Zamboanga del Sur. The Adtuyon Clay Loam and the Adtuyon Loam is situated  in the eastern part near the boundary with Misamis Occidental. 

Land Capability

    The factors that are vital in determining the capability of the place for crop production are the soil texture, slope, soil erosion, drainage, flooding hazards, and climatic condition. Statistics show that great majority of land in the municipality is rolling, however the place is generally fertile and suitable for the production of corn, upland rice, vegetables, coconut,  coffee and bananas. 

E. Climate