Use of buffer methods to estimate the potential acidity of Mato Grosso soils

Abstract

Mato Grosso, with a total area of 903357 km², does not have an official methodology for estimating soil potential acidity (H + Al), and determination of H + Al using the standard method is onerous and time consuming. The objective of this study was to compare estimated values of H + Al determined using the standard calcium acetate method with those obtained using three buffer methods, namely, the Shoemaker, McLean, and Pratt (SMP) buffer, Sikora buffer, and Santa Maria buffer (SMB) methods, with samples of the main classes of cultivated soils in the state of Mato Grosso. A total of 196 soil samples were collected from the arable layer (0-20 cm) in agropastoral and adjacent native systems. Statistical models were obtained and compared with models used by laboratories that are hypothetically inadequate because there is no calibration for soils in the state. After laboratory analyses, the paired H + Al and equilibrium pH values corresponding to the equilibrium of each buffer solution (SMP buffer, SMB, and Sikora buffer) were subjected to nonlinear regression analysis (P < 0.05). The SMB method, which does not release pollutant residues into the environment, was better than the Sikora and SMP methods for replacing the standard method used in state laboratories for soil analysis, that is, H + Al (cm3 c dm-3) = 51.189 -25.70 ln(pHSMB) (R2 = 0.88, P < 0.0001). Thus, if laboratories use uncalibrated equations to estimate soil potential acidity, the recommended limestone correction will be underestimated or overestimated, which may compromise crop productivity in Mato Grosso.

Relationship between pH and base saturation associated with soil cation exchange capacity in soils of Mato Grosso do Sul, Brazil

“…Descriptive statistics of soil samples collected in the state of Mato Grosso do Sul, Brazil, at a depth of 0-0.2 m subdivided according to their CEC pH 7. Although lime is normally incorporated to ~20 cm or soil surface applied, pH and Al for the 0.2-0.4-m depth (Table 2) was similar to 0-0.2-m observations (Table 1) (Prado et al 2020). However, soil acidity under native conditions is generally similar throughout the profile of highly weathered soils (Motta and Melo 2009).…”

“…In a soil survey of a Cerrado area under native conditions, Lopes and Cox (1977) found a mean equivalent pH of 4.4 in CaCl 2 0.01 M (pH 5 in water) and 0.56 cmol c ·dm -3 for Al. This difference was expected since liming is almost a mandatory practice in converting native regions for agricultural use (Prado et al 2020).…”

“…As well as providing calcium (Ca 2+ ) and magnesium (Mg 2+ ), the practice of liming is very effective for neutralizing acidity originating from hydrogen (H + ) deprotonation of hydroxyls group from mineral and organic matter fractions and those hydrolyzed from exchangeable aluminum (Al 3+ ) (Bolan et al 2023, Vargas et al 2019). Among calculation methods for liming recommendation (LR), the most widely used method (Prado et al 2020, Predebon et al 2018) aims to increase soil base saturation (V%) (Quaggio et al 1985) by elevating initial soil base saturation (V1) to levels required for producing a certain crop (V2). This method considers the cation exchange capacity at pH 7 (cmolc·dm -3 ) and the total neutralizing relative power of the soil corrective (Quaggio et al 1985).…”

Growth and Wood Quality from 32-Year-OldEucalyptus pellitaOwing to Chemical Characteristics of the Soil

“…The mathematical and computational models studied by LIMA et al (2017) showed that hydrogen potential (pH), potential acidity (H + +Al +3 ) and Mg, P, K, and Al contents were, in that study, crucial characteristics for growth of Eucalyptus urograndis. The use of buffer methods studied by PRADO et al (2020) to estimate soil potential acidity indicated that the overestimation or underestimation of soil potential acidity may incur a limestone dosage error during the management of soil fertility (liming). BALBINOT et al (2010), studying the intercropping between E. tereticornis, and Mimosa caesalpiniifolia and Mimosa pilulifera, observed a reduction in effective CEC, sum of bases, Mg, P, Ca content and base saturation (%) of the soil, while, at the same time, pH, N, Na, Al and H + +Al +3 values increased in all planting systems.…”

Photosynthetic Assimilation of the Guava (Psidium guajava) cv. Paluma under Different Pruning and Fruit Thinning Intensities

“…The monthly means of air relative humidity ranged from 80.6% to 27.4%. The soil is classified as a dystrophic yellow Oxisol with a sandy texture [41]. The physicochemical characteristics of the soil before the experiment was set up are shown in Table 1.…”