PHOSPHORUS DISTRIBUTION IN SOILS UNDER DIFFERENT LAND USE AND LAND COVER IN SEMI-ARID REGION OF UTHAL DISTRICT LASBELA

Abstract

This research examined how diverse agricultural land uses on phosphorus (P) distribution and availability in calcareous soils.  Samples were collected from different land types to examine key p fractions, including soluble and exchangeable P (labile P), Fe and Al-bound P (moderately labile P), Ca-bound P (moderately labile inorganic P), and residual P (highly stable P). Labile P was most abundant in crop land (L2) and orchard (L5) surface soils, primarily due to fertilization and organic amendments, where bare land (L1) consistently exhibited the lowest levels due to limited P inputs and vegetation. Moderate labile P, particularly Fe and Al-bound and Ca-bound fractions, was similarly elevated in managed lands like orchards and crop lands, indicating the influence of agricultural practices such as liming and organic amendments. In contrast, forest (L3) and grassland (L4) soils showed moderate P levels, reflecting the role of natural organic matter cycling. Residual P, representing the most stable form, accumulated most in orchard (L5) and crop land (L2), driven by long-term transformations of added P into recalcitrant forms, while bare land (L1) consistently displayed the lowest concentrations (orchard, Crop land, Bare land, Grass land, Forest land) to study different P fractions: labile (easily available), Fe/Al-bound, Ca-bound, and residuum (unavailable) P. Through all land uses, calcium-bound P dominated, of total P, emphasizing the strong impact of calcium carbonate in soils on P fixation. Contrariwise, grassland soils showed the moderate P levels, perhaps due to natural organic matter rates or distinctive P cycling procedures. Remarkably, labile P was comparatively higher in soils growing the most stable orchard land and crop land, demonstrating higher P availability. Long-term fertilization guided to P accretion in inorganic forms, especially as calcium-bound P. This proposes that while manuring upsurges total P, a significant portion develops immobilized. Significant positive correlations between labile P, Fe/Al-bound P, and Ca-bound P indicate that these fractions are interrelated and predisposed by similar soil processes. The strong correlation between Olsen-P and CaCl2-P proposes that these approaches efficiently degree of available P in calcareous soils. Principal component analysis shows that four components clarify most of the difference in P distribution, proposing complex relations between land use, soil properties, and P dynamics.