Buffer Ph methods for estimation of lime requirement of tropical acid soils

Abstract

Lime requirements (LR) of 26 agricultural acid soils were estimated using the following buffer methods: Shoemaker‐McLean‐Pratt (SMP) single buffer (SMP‐SB), SMP double buffer (SMP‐DB), Mehlich buffer method for crops with high LR (MEHLICH I), and Mehlich buffer methods for crops with low LR (MEHLICH II). The LR were determined to three pH targets (6.5, 6.0 and 5.5). The LR values were then evaluated through regression analysis using LR values obtained by the Ca(OH)₂ titration (for the 6.5 pH target) and moist CaCO₃‐incubation (for the 6.0 and 5.5 pH targets) as reference methods. All the buffer methods were well correlated with the reference methods but the SMP‐DB gave the best results for both high and low LR soils, and was particularly impressive at the lowest pH target.     

Comparative study of selected lime requirement methods for some acid Ghanaian soils

Abstract

The acid soils of the western region of Ghana which hitherto have been relegated to forest and tree crops production are becoming increasingly important for agricultural food crop production in the country. However, on account of their strongly acidic properties, there is the need to apply agricultural lime to the soils to improve upon their productivity. At present, however, information on the lime requirement and appropriate liming practice for these soils is lacking. The objective of this study was to compare the suitability of selected chemical methods for the determination of the lime requirement to predict lime needs of these naturally occurring acid soils. The lime requirement of six acid soils were determined by calcium hydroxide [Ca(OH)₂] titration, exchangeable aluminum (Al), and Shoemaker, McLean, and Pratt (SMP) buffer methods. Correlation analysis showed that all the methods were highly correlated with one another. The SMP method was found to be somewhat better than either exchangeable Al or Ca(OH)₂ titration method for estimating the lime requirement of the soils. Hence, the SMP method is recommended for use as the diagnostic index of lime requirement of these soils because of its speed and simplicity. Regression studies on the lime requirement values by the three methods and selected soil properties showed that exchangeable Al and organic carbon were the most important soil factors contributing to the lime requirement of these soils. Clay content was significantly correlated only with the Ca(OH)₂‐based lime requirement values (r = 0.81*).     

Predicting the lime requirement of soils under permanent grassland and arable crops

Abstract. Graphs of soil pH against time were plotted for the Park Grass Experiment at Rothamsted Experimental Station, begun in 1856, and the Long-term Liming Experiments at Rothamsted and Woburn farms, begun in 1962. These showed that the magnitude and duration of the effect of lime applications varied with soil type, initial pH, fertilizer nitrogen application, and the crop grown. Simple equations for each situation were linked to form an empirical model which, with appropriate input data for soil type, crop, and initial and target pH, predicted the lime needed to reach that pH. Model predictions compared well with estimates from a Woodruff-type buffer method. The model forms a sound basis for a more comprehensive lime requirement model covering the whole of the United Kingdom.     

A rapid method for predicting the lime requirement of acidic temperate soils with widely varying organic matter contents. II. Testing the lime requirement model

A model for predicting lime requirement (Bailey et al. , 1989) was tested using data from independent liming experiments on soils from Northern Ireland and New Zealand. Lime requirements predicted by the model were also compared with those obtained by the methods currently used by the Department of Agriculture for Northern Ireland and by the Ministry of Agriculture, Fisheries and Food in England and Wales.
The model predicted lime requirement precisely for the independent set of soils from Northern Ireland, and was as reliable at predicting lime requirement for New Zealand soils as the best of seven other quick-test methods. The model was more reliable at predicting lime requirement for soils from Northern Ireland than the method currently used by the Department of Agriculture for Northern Ireland, and appeared to be as reliable as the method used by the Ministry of Agriculture, Fisheries and Food in England and Wales.     

A rapid method for predicting the lime requirement of acidic temperate soils with widely varying organic matter contents. I. Development of the lime requirement model

A model to describe the shapes of soil pH-CaCO₃ neutralization curves is presented. The model can be used to predict lime requirement in soils with widely varying organic matter contents. Parameters of the model are predicted from the easily measured soil properties of sample density and initial pH. The results suggest that soil titratable acidity is primarily related to soil organic matter content, and that soil organic matter content may be predicted from measurements of soil sample density. The proposed method for predicting lime requirement should be superior to other established quick-test methods for routine soil testing both in terms of speed and versatility.     

A robotic procedure for the determination of soil lime requirement

Abstract

A commercial laboratory robot has been programmed to aid in the determination of soil lime requirement. Soil samples submitted to our laboratory, after drying, grinding, and sieving, are manually scooped into racks of pre‐weighed glass tubes. From this point onward, the robot performs all functions. The weight of soil in each tube is obtained using an analytical balance. Deionized water is added using a mobile pipet, and the contents of each tube stirred, and optionally centrifuged. The soil/water pH (pHw) is determined using a mobile combination electrode. SMP buffer solution is added, the contents stirred, optionally centrifuged again, and the soil/SMP buffer pH (pHsMP) value is obtained. The weight and two sets of pH data for each soil sample are transferred to disk, and lime requirement results calculated using a computer spreadsheet program.     

Principles underlying the practice of determining lime requirements of acid soils by use of buffer methods

Abstract

A buffer is generally a mixture of a weak acid and a salt of the same weak acid. Hence it can neutralize both acids and bases, and thus resists marked changes in pH of a system. Yet systematic change in pH of a buffer caused by addition of an acidic substance can be used to indicate the total acidity represented by the change in buffer pH. Since acid soil is itself a buffer, when it is added to a buffer mixture for the purpose of measuring its acidity or lime requirement (LR), the resulting double‐buffer suspension (soil‐buffer) is a relatively complex system. Much of the complication in interpreting the changes in buffer pH brought about by mixing soil and buffer stems from the facts: i) that much of the acidity is pH‐dependent, and ii) that quick‐test methodology involves reaction of only a fraction of the total soil acidity with the buffer. Marked change in relative amounts of H ions dissociating from the soil‐SMP‐buffer system at soil‐buffer pH 6.9 and above accounts for relatively wide variations between buffer‐indicated and CaCO₃ incubation‐measured LR of low LR soils. Similarly, decreased reactivity of H⁺ in high organic matter soils and increased reactivity of H in acid‐leached soils cause errors in buffer‐indicated LR. Awareness of these principles helps avoid pitfalls of existing buffer methods, and has led to incorporation of the double‐buffer feature for improving the SMP method.     

Effect of calcium carbonate as determined by lime requirement buffer pH methods on soil characteristics and yield of sorghum plants

Abstract

A primary limit to crop production in extended regions of northern Greece is the infertility of acid soils, especially nutrient element unavailability or toxicity. An experiment was conducted to determine under greenhouse conditions which buffer pH method selected in a previous laboratory experiment is best suited to predict the lime requirement (LR) of acid soils which is most appropriate in relation to plant growth and nutrient element uptake of sorghum plants. The lime needs of three naturally occurring acid soils were estimated by three methods: Adams‐Evans (AE), Shoemaker‐McLean‐Pratt single buffer (SMP‐SB), New Woodruff (NWOOD), and the calcium hydroxide [Ca(OH)₂] equilibration procedure. Two greenhouse experiments were conducted: (i) Experiment I during the 1996 season with ORESTIAS a sandy loam soil, and (ii) Experiment II during 1997 and 1998 season with XANTHI a loam sandy soil and DRAMA a sandy clay loam soil, respectively. The following results were obtained. Differences were noticed between the soils as well as within the LR methods. The ORESTIAS soil needed 63% more calcium carbonate (CaCO₃) than the XANTHI soil and 70% more than DRAMA soil to achieve the target pH. Among the three LR methods, results showed that in two of the three soils the highest LRs were determined by the NWOOD and the lowest by the Ca(OH)₂ methods. After six weeks of incubation, no one method gave exactly the needed amounts of CaCO to achieve the target pH, the estimated amounts being mostly higher than tiiat needed except for the DRAMA soil. Among the methods, in general the SMP‐SB method predicted lime rates that raised the soil pH nearest to the target pH and the NWOOD soil seemed to be the more consistent for the three soils. The smallest LRs were predicted by the Ca(OH) method. Based upon plant production and nitrogen (N) uptake in the 1996 season, the shoot yields were significantly higher using the SMP‐SB method and lower with the NWOOD method. Similar results were obtained for the XANTHI and DRAMA soils during the 1997 season. On the contrary in the 1998 season (2nd experimental year), the highest yields were obtained with the NWOOD buffer method. For the 1996 and 1997 seasons, tissue N concentrations were partly significantly higher using the SMP‐SB method. In the 1998 vegetation period, the N concentrations were low and the control plants had significantly higher N contents.     

Phosphorus requirement for irrigated bush beans production on coastal plain soils

Economic agricultural production of coastal plain sandy soils requires intensive nutrient and irrigation management. Optimization of nitrogen and phosphorus applications will bring environmental sustainability also to the production. A greenhouse study was conducted on irrigated sandy soils with bush beans comparing six different phosphorus (P) rates set in completely randomized blocks with four replications during 2016 and 2017 to determine optimum P requirement. Soil and tissue nutrients, plant height, dry matter, and relative yield (RY) data were collected. Agronomic Use Efficiency (AUE) was calculated. Highest RY and AUE were recorded at 53 or 59?kg ha^?1 of P application rates, above which there was no response. A negative P: zinc (Zn) impact was also documented. A maximum soil application rate of 59?kg P ha^?1 can be suggested as adequate to optimize the yield of bush beans produced on coastal plain sandy soils of the southeastern United States.     

A trial to determine the lime requirement for reseeded grassland on a peaty hill soil

Abstract. Lime was applied in summer 1981 at rates up to 201 ha⁻¹ prior to reseeding an unimproved peaty hill soil. A marked pH gradient with depth developed showing that 3 years after application lime had very little effect below a depth of 5 cm. Soil pH values for 0–7.5 cm samples were: nil lime-4.2; 1 t ha⁻¹-pH 4.3; 2 tha⁻¹-pH 4.6; 4 t ha⁻¹-pH 5.0; 6 t ha⁻¹-pH 5.6. In the 0–2.5 cm layer pH values were much higher.
In all years at least 80% of maximum yield was achieved from an initial application of 21 ha⁻¹ lime. Botanical analysis showed that maximum persistence of sown species, perennial ryegrass and timothy, occurred from 2 t ha⁻¹ lime; 6 t ha⁻¹ lime was necessary for maximum persistence of clover. Lime application had only small effects on the mineral composition of the herbage.     

Application of lime and wood ash to decrease acidification of forest soils

Liming and wood ash application are measures to decrease acidification of forests soils. The assessment of lime requirement can be based on that base saturation, which indicates a low risk of acid toxicity. Because of a wide spread Mg deficiency in Central European forests, Mg containing lime is normally applied. Ash from untreated wood is applied to decrease soil acidity as well as to improve K and P nutrition. In wood ash, K is the most soluble nutrient, follwed by Ca and Mg. The overall dissolution rate of lime applied to the forest floor is about 1t ha^?1 a^?1. After liming, soil solution alkalinity and Mg concentrations increase markedly, while changes of Ca, H ions and Al concentrations are less pronounced. After the application of wood ash, K concentrations increase due to the high K content and the high solubility of K in wood ash. After the application of a sufficiently high dosage of lime to the forest floor, the decrease of acidity in deeper soil layers may need decades because of the low solubility of lime. Nitrification and nitrate leaching induced by lime or wood ash may reduce their acid buffering efficiency.     

The effect of lime on the response of soils to sodic conditions

The role of CaC0₃ in preventing clay dispersion and losses in hydraulic conductivity (HC) of sodic soils was determined directly by mixing two lime-free soils with 0.5 and 2.0 per cent CaCO₃. Whereas the HC of the lime-free soils dropped sharply when 0.01 n solutions of SAR 20 were displaced with distilled water, mixing the soils with powdered lime prevented both HC losses and clay dispersion. The response of a sandy soil mixed with lime was similar to that of a calcareous sandy soil. The beneficial effect ofCaC0₃ was not so pronounced in soils equilibrated with solutions of SAR 30. The increase in electrolyte concentration, due to CaCO₃ dissolution, was suggested as the mechanism responsible for the beneficial effect of lime.     

Response of maize for grain to potassium and magnesium fertilizers in soils with high lime contents

An antagonistic reaction between calcium (Ca) and magnesium (Mg) and potassium (K) may lead to low absorption of K and Mg by plants from soils with high Ca contents even when levels of K and Mg should be adequate. Two separate field studies were carried out in 2009 and 2010 to determine the effects of potassium (0, 40, 80, 120 kg K₂O ha^?1; as potassium sulfate) and magnesium (0, 20, 40, 60 kg magnesium oxide (MgO)ha^?1; as magnesium sulfate) applied to a soil with high lime content either separately or in combinations, on the grain yield and yield components of maize for grain in semi-arid Central Anatolia in Turkey. One dose of the K, Mg-fertilizers was applied during sowing in both years. According to the results, increasing the dosage of K increased yield components more than increases in Mg dosages. Combinations of K and Mg tended to maximize the yield components. Moreover, the greatest plant heights, first ear lengths, grain weights per ear and protein ratios were obtained for the K₈₀Mg₄₀ dose.     

Handy methods for determining the isoelectric point of soils

Three handy electrochemical methods for measuring the isoelectric point (IEP) of soil are described.     

Effects of lime and nutrient salts on the microbiological activities of forest soils

Summary In pot experiments, lime and mineral salts were applied to forest soils taken from three different sites. Microbial biomass, basal respiration, N turnover, and the activities of protease, phosphatase, and CM-cellulase were determined monthly. The fertilized soils showed a great increase in biomass, respiration and N turnover, and some increase in protease activity, whereas phosphatase activity decreased in comparison with the untreated soils. Estimates of the number of colony-forming units of different classes of microorganisms showed an increase in treated soils in most cases. The untreated soils had the lowest biological activity but the maximum application of lime and mineral salts did not automatically lead to maximum activity.     

Zinc requirement of corn grown on two calcareous soils of Pakistan

In greenhouse studies, corn (Zea mays L.) growth increased with Zn fertilization of two alkaline calcareous soils. Zinc concentration and total uptake increased with Zn application. Very high correlations were recorded between plant tissue Zn concentration, total Zn uptake and soil Zn levels determined by DTPA and AB-DTPA soil tests. Correlation between Zn concentration in plants and relative yield was poor. However, close relationships were revealed between extractable soil Zn and relative yield. Near maximum dry matter yield of corn was associated with a fertilizer rate of 2 mg Zn/kg soil. Plant tissue Zn-requirement was 27 mg/kg in 15 days old plants and 32 mg/kg in corn shoots of 40 day age. Critical soil test Zn level was 1.2 mg/kg by DTPA and 1.7 mg/kg by AB-DTPA method. Use of AB-DTPA soil test is suggested for evaluating Zn status of calcareous soils.     

The effect of lime and compost amendments on the potential for the revegetation of metal-polluted, acidic soils

The revegetation of soils affected by the historic pollution of an industrial complex in central Chile was studied. Spontaneous and assisted revegetation and changes in the physicochemical properties of the soils were evaluated in field plots that were amended with lime or lime + compost. Lime had no effect on plant productivity in comparison with the control, whereas the incorporation of lime + compost into the soil increased the plant cover and aboveground biomass. The application of lime + compost increased the plant productivity of Chrysanthemum coronarium (a species sensitive to the atmospheric emissions from the industrial complex), thus showing effective in situ stabilization of soil contaminants. Regression analyses suggested that the plant response was due to the increase in the soil organic matter content rather than to the increase in the soil pH. The aboveground biomass and plant cover did not differ under the spontaneous and assisted revegetation regimes. The native soil seed bank was sufficient for attainment of the proper plant cover and biomass production after the application of the soil amendments. Although the pCu²⁺ in the amended soils was 4 orders of magnitude higher than in the unamended control, the shoot Cu concentration was similar among most of the combinations of plant species and amendments.     

Comparison of a combination pH electrode and field effect transistor electrode for the determination of soil pH and lime requirement

Abstract

A commercial laboratory robot has been used to compare the responses of two different types of electrode for the determination of soil in water pH (pH_w), and soil in SMP buffer solution pH (pH_SMP). The latter is integral to a popular method for the determination of soil lime requirement. A combination pH electrode is compared with a solid state, ion selective field effect transistor electrode. Response times and hysteresis effects are discussed.     

Evaluation of three calcium extractants for coastal plain soils

Abstract

Mehlich 1‐Ca is used as an index to predict the Ca requirement for peanut (Arachis hypogaea L.) fruit development in major peanut growing states. Recently, some concern has been raised about the inadequacy of Mehlich 1 extractable Ca for that purpose. Possible use of alternative extractants for soil Ca has been suggested. In this study, relationships among Mehlich 1, 0.2 M NH₄Cl and 0.01 M NaNO₃ extractable Ca were examined in several Coastal Plain soils to which gypsum or lime had been applied. Variability in extractable Ca was much greater following lime treatment than following gypsum treatment. In Bonifay soil, the quantity of Ca extractable by the three extractants was similar in a gypsum treatment, but in a lime treatment (at an application rate equivalent to the gypsum treatment) Mehlich 1‐Ca was 2 and 5‐fold greater than NH₄Cl‐ and NaNO₃‐Ca, respectively. In Greenville soil, Mehlich 1‐Ca was 3 to 4‐fold greater than NaNO₃‐Ca regardless of gypsum or lime amendment.

For soil samples from a field experiment on Lakeland sand, where lime or gypsum was applied prior to planting, Mehlich 1‐Ca was 7.5 and 2.2‐fold greater than NaNO₃‐Ca for the lime and gypsum treatments, respectively. Greater variability in Mehlich 1‐Ca in lime than in gypsum treatments was due to possible inclusion of undissolved limestone in the soil samples, resulting in overestimation of Ca available for peanut fruits. Mehlich 1‐Ca appears to be an adequate index of soil Ca for prediction of supplemental Ca requirement for peanut if lime has not been applied or has been applied well in advance of planting, thus minimizing the inclusion of undissolved limestone with the soil sample taken from the fruiting zone (0–8 cm depth) 10–14 d after planting.     

Evaluation of four soil test extractants for Zimbabwe soils

Abstract

The objective of this research was to compare the results from anion exchange Resin extraction of P, and the acidified ammonium acetate (AA) extraction of K and Mg with the results obtained using two single extraction procedures, Mehlich 1 (M‐l) and Mehlich 3 (M‐3). Phosphorus extracted from 72 Zimbabwe soils using M‐l and M‐3 was comparable to Resin extracted P in about 80% of the soils. Mehlich 1 extracted about half the amount of P as the Resin method, and M‐3 extracted about one and one‐half times as much. Phosphorus by M‐3 was highly correlated, (r — 0.846), with Resin extracted P from soils having 0.01M CaCl₂ pH values of equal to or greater than 5.9. On soils less than pH 5.9, the r value was 0.502, and for all soils, the r value for M‐3 vs Resin P was 0.615. Mehlich 1 extracted P vs Resin P had a r value of 0.298. Acidified ammonium acetate (AA) extraction of K and Mg was comparable to M‐l and M‐3 extraction of K and Mg in 92% or more of the 72 soils. The K correlation coefficient (r) for AA vs M‐l and AA vs M‐3 was 0.918 and 0.944, respectively. The Mg correlation coefficient (r) for AA vs M‐l and AA vs M‐3 was 0.940 and 0.962, respectively.