Abstract
The low phosphorus availability in tropical and subtropical soils, normally related to adsorption of phosphate to the minerals surfaces, can be attenuated when organic matter (OM) accumulates in the soils. Herein, we report the results of long-term experiments (18–32 years) aimed at quantifying the maximum phosphorus adsorption capacity (MPAC) and its determinant mineralogical variables in Brazilian soils and at assessing the effect of no-tillage (NT) in mitigating the phosphorus adsorption of soils. The MPAC of soils ranged from 297 to 4,561 mg kg-1 in the 0.00–0.10 m layer and from 285 to 4,961 mg kg-1 in the 0.10–0.20 m layer. The MPAC was correlated with the concentrations of iron oxides, goethite and ferrihydrite, gibbsite/(gibbsite+kaolinite) ratio and the specific surface area. The OM increased in the 0.00–0.10 m layer of NT soils, which was not reflected on the decrease of MPAC for the no-tillage soils.
Highlights
Phosphorus is an essential plant nutrient that is usually present in forms of low availability in the highly weathered soils of tropical and subtropical regions from Brazil, a phenomenon that has been suggested as one of the main limiting factors for agricultural production (NOVAIS; SMYTH, 1999)
The Alfisol and Ultisol developed from sandstone and granite, respectively, showed lower clay contents (≤ 228 g kg-1 of soil) than the Oxisols developed from basalt (Table 2)
The CTCpH7 values ranged from 7.3 cmolc kg-1 in the conventional tillage (CT) of Ultic Hapludalf to 16.6 cmolc kg-1 in the NT of Rhodic Hapludox, with base saturations (V) greater than 50% only in the Typic and Rhodic Hapludox soils
Summary
Phosphorus is an essential plant nutrient that is usually present in forms of low availability in the highly weathered soils of tropical and subtropical regions from Brazil, a phenomenon that has been suggested as one of the main limiting factors for agricultural production (NOVAIS; SMYTH, 1999). This lack of available phosphorus mainly is attributed to its strong adsorption (this term is used for all forms of retention of the element) by mineral surfaces, making a part of the total phosphorus unavailable to plants (ALMEIDA et al, 2003; CESSA et al, 2009; JOHNSON; LOEPPERT, 2006). The concentrations of these minerals in the soil and characteristics such as crystallinity and specific surface area vary with the parent material, intensity of weathering, composition of the soil solution and drainage conditions (MOTTA; KÄMPF, 1992; SCHAEFER et al, 2008) and may be affected by soil management systems (SILVA NETO et al, 2008)
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