PHOSPHORUS DYNAMICS AND SOLUBILIZING MICROORGANISMS IN ACID SOILS UNDER DIFFERENT LAND USE SYSTEMS IN UYO, AKWA IBOM STATE NIGERIA

Sule, Nicholas Ayegba and Akpan, Godwin Umoren

ABSTRACT

A research on phosphorus dynamics and solubilizing microorganism in acid soil of Uyo, Nigeria was carried out with the aim to investigate selected soil properties, forms of phosphorus (P), total P(TP), Inorganic P (P_i) organic P (P_O), available P, (AVP), microbial biomass P (MBP), enzyme activities (acid and alkaline phosphatase), Phosphorus solubilizing bacteria (PSB) and Phosphorus solubilizing fungi (PSF) and their correlation in acid soils (0-15 and 15-30cm depths) under different land use systems (Coconut plantation, upland rice farm, water leaf farm and uncultivated land). The research was conducted in the Department of Soil science and land Resources Management, University of Uyo, Nigeria from march 2022 to May 2023.Three composites soil samples of two different depths (0-15cm and 15-30cm) were collected each different land use systems making 24 samples in all. The samples were  divided into two parts; The sample for biochemical studies were stored in a sterile labelled bags and conveyed in a cooler containing ice block and then taken to the laboratory where it was stored in a refrigerator at 4^oC for determination of phosphorus cycling enzyme activities, and phosphate solubilizing ability of microorganisms. The second part were processed for selected physical and chemical analyses of the soil in the laboratory. The results showed that sand fraction in all the land use systems varied but not significantly except in coconut plantation that was significantly different from other land use systems at 0-15cm depths but at 15-30cm depth there was no significant difference among the sand fractions. Soil reaction showed strongly acid condition across all the land use systems and in the surface and subsurface layers. The mean data for organic carbon ranged from 0.73% in water leaf land use systems to 1.85% in coconut plantation at the 0-15cm depth whereas at 15-30cm depth it ranged from 0.54% from coconut plantation to 1.75% in uncultivated land. The soil samples in all land use systems differed significantly for the P-forms. Soils in Upland rice (136.77 mg/kg) were best in terms of having Total phosphorus. Soils in coconut plantation (64.66mg/kg) were best in having highest inorganic phosphorus. Soils in waterleaf farming (118.36mg/kg and 81.52mg/kg) had highest organic P and available P respectively. soils in uncultivated soil (7.10 µg P/g soil) had highest microbial biomass P and best in enzyme activities. Uncultivated soil (2.4×10⁷ µg PNP g^-1 h ^-1soil and 2.4×10⁷ µg PNP g^-1 h^-1soil) had highest phosphorus solubilizing bacteria and fungi respectively. PSB and PSF were significantly correlated with all P forms in the soil and P-cycling enzymes with exception to total inorganic phosphorus and alkaline phosphatase. This would lead us to understand the level of phosphorus dynamics and degradation of P pools due to cultivation and other land practices and the suitable management practices needed for soil quality restoration.

Keywords: Acid Soils–Uyo–Phosphorus–Soil Enzymes–Phosphate solubilizers