A Method to Determine a Phosphorus Adsorption Maximum of Soils as Measured by the Langmuir Isotherm1

Abstract

Adsorption of phosphorus by soils from dilute solu tions showed a closer agreement with the Langmuir iso therm than with the Freundlich isotherm. Constants calculated from the Langmuir isotherm and interpre tations based upon the meaning of these constants permit a sound theoretical approach to some of the problems of phosphorus retention in soils.The adsorption maximum calculated from the Lang muir isotherm was closely correlated with the surface area of soils as measured by ethylene glycol retention. The correlation coefficients and regression equations were r = 0.98 and y = 0.276x f 3.47 for 10 alkaline soils, and r -0.96 and y = 0.641x f 5.73 for 12 acid soils, where y -mg. P per 100 g. soil and x = rag. ethylene glycol retained per g. of soil. For a given surface area, i.e., 30 mg. glycol per g. soil, the acid soils held 2.17 times as much phosphorus' as the alkaline soils.The average values of a second constant, k, derived from the slope and intercept values, were 0.92 and 4.39 for the alkaline and acid soils, respectively. As the value of this constant increases, .the bonding energy of the soil for phosphorus increases. Thus, the acid soils re tained more phosphorus per unit of surface area and also held the phosphorus with a greater bonding energy than the alkaline soils ''HE reaction of fertilizer phosphorus with soils depends upon the nature and amount of adsorbing surface as

Phosphite as phosphorus source to grain yield of common bean plants grown in soils under low or adequate phosphate availability

“…(1) pH in water, EP = P in the equilibrium solution; OM = level of organic matter; T = cation exchange capacity at pH 7.0; m = aluminum saturation index; V = base saturation index; MPAC = maximum P adsorption capacity according to Olsen and Watanabe (1957); Ct = kaolinite; and Gb = gibbsite. Ki = SiO 2 / Al 2 O 3 ; and Kr = SiO 2 / (Al 2 O 3 + Fe 2 O 3 ).…”

Atributos químicos de solos influenciados pela substituição do carbonato por silicato de cálcio

“…O pH em água, Ca, Mg, Al, P, K, Cu, Fe, Mn e Zn foi determinado conforme Embrapa (1997), sendo o Ca, Mg e Al extraídos com KCl 1 mol L -1 , e P, K e os micronutrientes catiônicos pelo HCl 0,05 mol L -1 + H 2 SO 4 0,0125 mol L -1 (Mehlich-1). Também foram determinados a acidez potencial (H + Al) e o carbono orgânico, conforme Raij et al (1987); o P remanescente conforme Alvarez V. et al (2000); e a capacidade máxima de adsorção de P segundo Olsen & Watanabe (1957). Os valores de P adsorvido foram ajustados à isoterma de Langmuir para estimativa da CMAP.…”

Impact of chemically amended pig slurry on greenhouse gas emissions, soil properties and leachate

“…In conjunction with the P adsorption capacity of the soil, the equilibrium P concentration of the soil (EPC 0 ) (i.e. the point where no net desorption or sorption occurs) was derived using (Olsen and Watanabe, 1957):…”