Evaluation of traditional methods for estimating lime requirement in Brazilian soils

Abstract

The optimal soil pH for most annual crops in Brazil varies between 5.7 and 6.0. Numerous methods have been developed for estimating lime requirement (LR), but they vary widely in their predictions and fail to raise pH to desired values for optimum crop production in the highly weathered soils of Brazil. The objectives of this study were to (i) compare seven traditional methods for estimating LR in Brazilian soils; (ii) assess the effects of LR predicted by these methods on soil-acidity related properties, and (iii) determine if these methods are predicting LR to attain target pH values of 5.8 and 6.0, which are within the pH range recommended to optimize crop yields. The traditional LR methods evaluated in this study are based on the following criteria: exchangeable acidity (EA), base saturation (BSAT), exchangeable acidity along with Ca 2+ and Mg 2+ as proposed by the 4th (MG4A) and 5th (MG5A) Approximations to the Minas Gerais State, SMP soil-buffer pH (SMP), potential acidity (PA), and soil pH along with organic matter (pHOM). These methods were compared with the standard incubation method using correlation-regression analysis and, alternatively, the identity test designed for assessing equivalence between methods. Representative agricultural soils (n = 22) were incubated for 60 days with incremental amounts of lime determined by the tested methods. On average, LR predictions differed among methods, and increased in the following order: EA < BSAT ≈ MG5A ≤ MG4A ≈ SMP ≤ PA < pHOM. Suitable changes in soil pH, exchangeable acidity, potential acidity, base saturation, and Ca 2+ and Mg 2+ were achieved upon application of LR estimated by all methods except the EA and pHMO, which resulted in undesirable soil acidity characteristics. All methods evaluated in this study were unable to predict LR for attaining target pH values of 5.8 and 6.0 as revealed by the identity test, even though they were moderate to strongly correlated with the standard incubation method as indicated by the correlation-regression analysis. Further research should focus on the development of reliable methods for predicting LR to attain desired pH values and consequently maximize crop production on Brazilian soils.

Lime requirement for agricultural soils: A review of the current and potential methods for routine use

“…The incubation time of this approach is pragmatic as reaction of LM with moist soils may take weeks or months at room temperature. For examples, incubation times of 30, 60, and 90 days have been reported, respectively, for soils in Alberta and north‐eastern British Columbia (Canada) (Webber et al., 1977), soils in Kansas (Godsey et al., 2007) and soils in the Palouse region (USA) (McFarland et al., 2020) as well as Brazilian soils (Teixeira et al., 2020). Although most pH changes occur rapidly after base additions, a slow soil–lime reaction continues over a long period (Barrow & Cox, 1990).…”

“…Brazilian soils (Teixeira et al, 2020). Although most pH changes occur rapidly after base additions, a slow soil-lime reaction continues over a long period (Barrow & Cox, 1990).…”

Estimating Lime Requirements for Tropical Soils: Model Comparison and Development

“…The lime requirement models were evaluated using data from four soil incubation studies that measured the effect of liming on exchangeable acidity and ECEC or acidity saturation (Ananthacumaraswamy and Baker, 1991;Cochrane et al, 1980;Kamprath, 1970;Teixeira et al, 2020a). Soil incubation studies are experiments in which soil samples are mixed with different amounts of lime and incubated under controlled conditions (~ 30 • C and soil moisture at field capacity) for about a month to ensure that all lime reacts with the soil.…”

“…In the remainder of this paper, pH refers to the pH measured in a soil-water solution. This is the most commonly used method to measure pH and the pH measure available across the datasets we used (e.g., Teixeira et al, 2020a). Other methods to measure the soil pH include mixing the soil with an equivalent volume of 0.01 M CaCl 2 or 1 M KCl.…”

“…In acid tropical soils, the yield of many crops may not be negatively affected by a soil pH as low as 5.0 depending on other soil chemical properties (Abruña et al, 1969;Bell, 1996;Pearson et al, 1977) and raising the pH can result in a loss of soil structure and other problems (Harter, 2007). Therefore, a target pH level is seldom used, and if it is used, it should be defined locally (Fageria and Baligar, 2008;Teixeira et al, 2020a).…”