Influence of agro‐ecological zones on soil phosphorus fractions in central Nepal

Abstract Soil plays a pivotal role as the primary repository of phosphorus (P) in terrestrial ecosystems. Sequential fractionation, a widely employed technique, is applied to provide comprehensive insights into the properties and behavior of P within soil systems. Despite this, a knowledge gap persists regarding the distinct P pools existing in Nepalese soils. This study, therefore, aimed to explore how agro‐ecological zones influence the soil P fractions in central Nepal. A total of 225 soil samples were collected, with an even distribution of 75 samples from each zone encompassing the high‐hills, mid‐hills, and Terai plains across diverse locations in central Nepal. The sequential fractionation method was employed to characterize the P pools in the soils. The results indicated significant differences in the soil parameters across agro‐ecological zones, including soil pH, organic matter, texture, available P (Olsen P, Bray‐1 P, and Mehlich‐3 P), inorganic P fractions (loosely bound P, aluminum‐bound P, iron‐bound P, reductant soluble P, and calcium‐bound P), organic P fractions (labile P, moderately labile P, fulvic acid P, humic acid P [HA‐Po], and non‐labile P), as well as residual P and total P. The mid‐hills exhibit higher levels of most P fractions, followed by the high‐hills and Terai. In the high‐hills and Terai, HA‐Po was identified as a primary reservoir of total P, while in the mid‐hills, residual P dominates. The long‐term indigenous P supplying capacity follows a decreasing order: mid‐hills > high‐hills > Terai. The adoption of indigenous P‐releasing practices is beneficial in the mid‐hills. The Terai soil, characterized by high P mining, necessitates more critical P management than other zones. Overall, this study offers important insights into how the diversity of agro‐ecological zones affects P fractions, which can help guide the development of more effective soil P management practices for sustainable agriculture.