Phosphorus adsorption in soils under forest and savanna from Northern Amazon, Brazil

Abstract

Studies on maximum phosphorus adsorption capacity (MPAC) in soils from Roraima State and attributes that interfere with the magnitude of this characteristic are relevant and motivated this study. . P was analyzed in the supernatant for determining its adsorbed amount (P-rem). Adsorption values were fitted to the Langmuir isotherm in order to assess MPAC. Correlation tests were performed between MPAC and binding energy, pH, organic matter, clay, and CEC. MPAC values ranged from 14.50 to 527.93 mg kg −1 in the soil. The soils FT-Bonfim and LV-ITÃ presented a higher MPAC. Considering the representative soil classes in the State, MPAC does not correlate with any of the assessed attributes. In the soil classes Oxisol and Ultisol, MPAC has a negative and significant correlation with binding energy. Key words: Maximum phosphorus adsorption capacity. Correlation. Langmuir isotherm. ResumoEstudos sobre capacidade máxima de adsorção de fósforo (CMAP) em solos de Roraima e atributos que interferem na magnitude dessa característica são relevantes e motivaram esse trabalho. Nesse contexto, amostras da camada superficial (0-0,20 m) de quatro classes de solos: Latossolo Amarelo -LA e Latossolo Vermelho -LV (ITÃ, Caracaraí); Latossolo Amarelo -LA (Serra da Prata, Mucajaí); Latossolo Amarelo -LA e Argissolo Amarelo -PA (CCA, Boa Vista-RR); Plintossolo Argilúvico -FT (Bonfim) e Planossolo Nátrico -SN (Surumu, Pacaraima) representativos do estado de Roraima, foram utilizadas no presente trabalho, com a finalidade de determinar a influência de atributos físicos, químicos e da mineralogia dos solos sobre a CMAP. Amostras de 2,5 g de TFSA (terra fina seca ao ar) foram mantidas em contato com soluções de CaCl 2 0,01 mol L -1 (25 mL), mediante agitação por 24 h, as quais foram adicionados fósforo (P), na forma de KH 2 PO 4 , nas concentrações de 0-60, 0-80 e 0-110 mg L -1 . O P foi analisado no sobrenadante para a determinação da quantidade adsorvida (P-rem). Para avaliar a capacidade máxima de adsorção de fósforo (CMAP), os valores de adsorção foram ajustados à isoterma de Langmuir. Foram realizados testes de correlação entre CMAP e energia de ligação, pH,

Dynamic of P Flux in Tropical Acid Soils Fertilized with Humic Acid–Complexed Phosphate

“…The synergistic effects between P and liming application on Pi BIC and Pi HID-0.1 (clayey soil), and on Pi HID-0.1 and Pi HID-0.5 (sandy soil) demonstrated the importance of both managements to increase P available in the soil, minimizing P immobilization in tropical soils. Pi HID-0.1 and Pi HID-0.5 are characterized as the most stable P pool in the soil, generally associated with Fe/Al (hydr)oxides present on clay surface (Matos et al 2017;Yang et al 2013;Abolfazli et al 2012;Cross and Schlessinger 1995). The study of Jalali and Ranjbar (2010) reported that P fractions associated with Fe/Al (hydr)oxides represent large amounts in calcareous soils, as well as in tropical soils under continuous cultivation as demonstrated by Teles et al (2017).…”

“…Phosphorus (P) availability has restricted crop growth in tropical acid soils due to the predominance of iron (Fe) and aluminum (Al) oxides in the soil fine fraction, which leads to P adsorption and P precipitation with Al and Fe (Vásconez and Pinochet 2018;Nascimento et al 2018;Matos et al 2017;Camargo et al 2013;). Both, P adsorption and precipitation, have negatively affected agricultural production in tropical conditions due to P unavailability (Barbosa et al 2018;Withers et al 2018;Yang et al 2012).…”