Liming Acid Soils Research Articles

Iron Toxicity in Lowland Rice

ABSTRACT Lowland rice is a staple food for more than 50% world population. Iron toxicity is one of the main nutritional disorders, which limits yield of lowland rice in various parts of the world. The toxicity of iron is associated with reduced soil condition of submerged or flooded soils, which increases concentration and uptake of iron (Fe2 +). Higher concentration of Fe2 + in the rhizosphere also has antagonistic effects on the uptake of many essential nutrients and consequently yields reduction. In addition to reduced condition, increase in concentration of Fe2 + in submerged soils of lowland rice is associated with iron content of parent material, oxidation-reduction potential, soil pH, ionic concentration, fertility level, and lowland rice genotypes. Oxidation-reduction potential of highly reduced soil is in the range of –100 to –300 mV. Iron toxicity has been observed in flooded soils with a pH below 5.8 when aerobic and pH below 6.5 when anaerobic. Visual toxicity symptoms on plants, soil and plant tissue test are major diagnostic techniques for identifying iron toxicity. Appropriate management practices like liming acid soils, improving soil fertility, soil drainage at certain growth stage of crop, use of manganese as antagonistic element in the uptake of Fe2 + and planting Fe2 + resistant rice cultivars can reduce problem of iron toxicity.

Soil Fertility and Plant Nutrition Research Under Controlled Conditions: Basic Principles and Methodology

ABSTRACT In modern agriculture, use of essential plant nutrients in adequate amounts and proper balance is one of the key components in increasing crop yields. Further, in developing crop production technologies, research work under field and controlled conditions is necessary to generate basic and applied information. In addition, research is very dynamic and complex due to variation in climatic, soil, and plant factors and their interactions. This demands that basic research information can only be obtained under controlled conditions to avoid or reduce effects of environmental factors on treatments. Hence, the objective of this article is to discuss basic principles and methodologies of research in soil fertility and mineral nutrition under controlled conditions. Topics discussed are soil and solution culture experimental techniques including, fertilizer application and planting, liming acid soils, experimental duration and observations, composition of nutrient solutions, preparation and sources of iron (Fe) in nutrient solutions, pH of nutrient solutions, and stable supply of nutrients in the solution culture.

Pressurized Hot Water and DTPA‐Sorbitol as Viable Alternatives for Soil Boron Extraction. II. Correlation of Soil Extraction to Responses of Boron‐Fertilized Alfalfa

Pressurized hot water and DTPA‐Sorbitol are two relatively new, proposed alternative soil boron (B) extraction methods for which no data on yield or plant nutrient uptake have been reported for validation. Both methods initially have shown significant correlation with the hot water extraction method in untreated soils as well as soils incubated with various levels of B. The objective of the research was to extract samples of B‐treated soils by using all three extraction methods and correlate the B values obtained to yield, B tissue concentration, and total B removal of alfalfa (Medicago sativa). Greenhouse and field experiments on alkaline and limed acid soils naturally low in hot water‐extractable B were conducted to test alfalfa response to B fertilizer. In the greenhouse, highly significant relationships exist between plant uptake and extractable B with all three methods at varying levels of applied B, but no alfalfa yield response was observed. All three methods result in accurate predictions of plant B tissue concentrations and total B removal. The field experiment exhibited a significant positive relationship between total alfalfa yield and extractable B using hot water and pressurized hot water extractions. Extractable B using DTPA‐Sorbitol was not related to total alfalfa yield in the field experiment. This work, coupled with the earlier incubation studies, supports the pressurized hot water extraction method as an improvement over hot water in diverse soil types. The lack of relationship in the acid soil supports DTPA‐Sorbitol as an improvement over hot water in alkaline soils.

Peanut response to lime and molybdenum application in low pH soils

Liming acid soils is considered to assure the availability of Mo in crops. Additionally, in peanuts (Arachis hypogaea L.) the positive response to liming is associated to a better supply of Ca+2, Mo for the nitrogenase-complex activity, and other non-nitrogen fixing activities of the crop. This study was thus undertaken to assess the effect of lime, Mo, and the lime-Mo interaction on peanut crop, on an acid Ultisol at the Mococa Experimental Station, Instituto Agronômico, São Paulo State, Brazil, from 1987 to 1990. A randomized complete block design with four replications, in a 4 x 4 factorial arrangement, was used in the study. The factors included four lime rates (0, 2, 4, and 6 t ha-1) broadcast and incorporated into the soil, and Mo (0, 100, 200, and 300 g ha-1) as (NH4)2MoO4 applied as seed dressing. Lime was applied once at the beginning of the study while Mo was applied at every planting. Peanut seed cv 'tatu' was used. Significant increase in peanut kernel yield with liming was only evident in the absence of Mo, whereas the peanut response to Mo was observed in two out of the three harvests. A higher yield response (28 % increase) was found when Mo was applied without liming. Soil molybdenum availability, as indicated by plant leaf analysis, increased significantly when lime was applied. Molybdenum fertilization led to higher leaf N content, which in turn increased peanut yield in treatments with smaller lime doses.

Phosphorus Forms and Desorption Patterns in Heavily Fertilized Calcareous and Limed Acid Soils

Phosphorus desorption from fertilized soils is significant for agriculture and the environment. This study was aimed at characterizing the forms in which P occurs in calcareous and limed acid soils and their influence on P desorption patterns. The P forms of two limed acid and three calcareous soils of Europe were characterized by chemical extraction, isotopic exchange, and sequential fractionation. Phosphate desorption was studied using resins and goethite as ion sinks. Total P ranged from 705 to 1400 mg kg−1 Isotopic exchange revealed more surface‐adsorbed P in the limed acid than in the calcareous soils. Calcium phosphates predominated in the calcareous and Al and Fe phosphates in the limed acid soils; one limed acid soil contained significant amounts of Ca phosphates. The mixed cation and anion exchange resins (ACER) were more effective in desorbing P than the anion exchange resin (AER) and goethite. The desorption curves indicated significant differences in the degree of homogeneity of the P desorption reactions, the greatest and lowest degree of homogeneity corresponding with calcareous soils. The proportion of ACER‐extractable P that was plant‐available P was >50% for the limed acid and <20% for the calcareous soils. The proportion of ACER‐extractable P that was released to 0.002 M CaCl2 was >60% for the limed acid and <40% for the calcareous soils. Plant P availability was thus poorer in the calcareous soils than in the limed acid soils.

Tolerance of tropical common bean genotypes to manganese toxicity: Performance under different growing conditions

Manganese (Mn) toxicity is an important constraint to the production of common bean (Phaseolus vulgaris L.) in tropical and subtropical soils. Amelioration of Mn toxicity by soil modification is difficult in Andosols, and liming of acid soils is often not feasible for small farmers. Substantial genetic variation for Mn tolerance exists in bean germplasm, but is difficult to assess in field trials due to interactions with several environmental factors. The objectives of this study were to identify sources of genetic tolerance to Mn toxicity and to compare their performance using three growing conditions. Contrasting genotypes were evaluated for Mn tolerance by 1) biomass accumulation under Mn stress in solution culture, 2) biomass accumulation under Mn stress in silica sand culture, and 3) seed yield of plants grown in Mn‐amended soil. Genotypes varied substantially in Mn tolerance: A‐283, BAT‐795, Dore de Kirundu, IPA‐7419, Carioca, G‐12896a, and NEP BAYO 22 were susceptible, while Argentino, BAT‐271, Calima, EMP‐84, H6 Mulatinho, and Pintado were more tolerant when tested in solution culture. Genotypic tolerance observed in solution culture correlated well with tolerance observed in silica sand. Some genotypes that performed very well in solution culture and in silica sand did suffer severe yield reduction in Mn‐amended mineral soil. Manganese toxicity reduced shoot branching resulting in fewer seeds per plant in soil grown plants. We conclude that screening of genotypes in solution culture is useful to identify sources of tolerance to Mn toxicity, but performance of those genotypes in soil might be confounded by other edaphic stresses.

Effects of acidity on mineralization: pH-dependence of organic matter mineralization in weakly acidic soils

The literature is ambiguous regarding the influence of acidity on mineralization of soil organic matter. Although mineralization is often regarded as being relatively insensitive to acidity, reports of agronomically-significant increases in N mineralization after liming of acid soils are common. We analyzed 61 soils (pH 5.1–7.9), representing all agro-ecological zones of Saskatchewan, Canada, to determine the pH-dependence of N mineralization. Mineralization was measured by aerobic incubation. There was no statistical relationship between the parameters of the first-order kinetic equation [i.e. the rate constant (k) and potentially mineralizable N (N 0)] used to describe the incubation data and soil pH. However, when pH of two slightly acid (pH 5.7 and 5.8) soils was raised using Ca(OH) 2, mineralization of N and C was stimulated. Initially, the rate of CO 2 evolution from soils treated with Ca(OH) 2, to raise pH to 7.3–7.4, was 2–3 times that from the unamended soils. Rate of CO 2 evolution from Ca(OH) 2-treated soil declined rapidly after about 7–10 d. During the entire 100-d incubation, Ca(OH) 2-treated soils at pH 7.3–7.4 produced 37% and 67% more CO 2C than their untreated counterparts. We observed comparable increases in N mineralization. The effect of Ca(OH) 2 was attributed to release of labile organic matter when pH was increased. Dissolved organic matter in saturated paste extracts was well correlated with C and N mineralized. A model consisting of two simultaneous first-order equations was needed to describe mineralization in Ca(OH) 2-treated soil. Application of Ca(OH) 2 increased the labile pool of mineralizable C from 18 to 157 mg kg −1 in one soil and from 45 to 301 mg kg −1 in the other. We showed that the phosphate-borate buffer test for mineralizable N is pH-dependent because of the effect of pH on organic N solubility. In contact with the buffer, soil pH is raised to 11.2 (i.e. buffer pH), resulting in release of organic N, which is then susceptible to hydrolysis. Organic N extracted using an unbuffered extractant, hot 2 m KCl, was independent of soil pH.

Acidification rate of limed soil in a semiarid environment

To evaluate the benefits of liming acid soils, a method is needed to predict the longevity of its effect on soil pH. We coupled a simple index of soil buffering with estimates of the proton budget to predict long-term pH changes in a limed soil (Dark Brown Chernozem) in Saskatchewan. Analysis of published data for Saskatchewan soils showed that acceptable estimates of soil buffering can be obtained from organic matter and clay content. Buffer capacities of organic matter and clay were estimated at 487 and 26 mmol(±) kg−1 (pH unit)−1, respectively. Soil pH, titratable acidity, and effective cation exchange capacity (CEC) were monitored for 18 yr after lime application [Ca(OH)2 at rates of 0, 4.5 and 6.7 t ha−1] to field plots in a wheat (Triticum aestivum L.)-fallow rotation. In limed plots, there was a tendency for pH, exchangeable Ca and effective CEC to decrease with time in the 0–7.5 cm layer and to increase in the 7.5–15 cm layer. This was attributed to mixing of the two layers during cultivation. In the 0–15 cm layer as a whole, there was no discernible change in acidity, Ca, or CEC during the monitoring period. Negligible re-acidification in limed soil was consistent with the estimated H+ budget. External acidification sources were negligible (no N fertilizer was applied). Acidification due to leaching of nitrate and export of cations in grain over 18 yr was estimated at 6–7 kmol(H+) ha−1. This amount of acidity would lower soil pH by less than 0.1 units [buffer capacity of the top 15 cm of soil was ≈70 kmol(±) ha−1 (pH unit)–1], an amount too small to be detectable against background variability. Key words: Buffer capacity, organic matter, proton budget, titratable acidity

Measurement of the sensitivity of orchard soils to acidification

The pH buffer curves for 45 surface soils from apple (Malus domestica Borkh.) orchards in southern British Columbia were determined. Buffer curve shape differed according to the initial soil pH and incubation treatment. Soils with initial pHw < 7.4 and incubated with either H2SO4 or CaCO3 had typically sigmoid or modified sigmoid buffer curves. Non-calcareous soils with initial pHw > 7.4, incubated with H2SO4 were far less buffered above pH 6.5–7.0 than soils with initial pH < 7.4. Thus, non-calcareous neutral to alkaline soils may be more susceptible to acidification than buffer curves derived from liming acid soils might predict. A new measure of soil susceptibility to acidification, the acidification resistance index (ARI), was derived from buffer curves. It is defined as the amount of acid (cmol (p+) kg−1) required to reduce soil pH from its initial level to pH 5.0. Best-fitted multiple regression equations between ARI and soil properties routinely measured in soil test laboratories determined that 79% of the variation in ARI could be explained by a combination of extractable cations and initial soil pH. This regression model could be used to provide an inexpensive measure of soil susceptibility to acidification for orchards where acidifying fertilizers are applied through drip irrigation systems. Key words: Soil acidification, pH buffer curves, Malus domestica Borkh, drip irrigation

Predicting lime-induced changes in soil-pH From exchangeable aluminum, soil-Ph, total exchangeable cations and organic-carbon values measured on unlimed soils

The 'Lime-it' model is a decision support system for graziers wanting to lime acid soils. In this study we used field experimental data to test, improve and validate the model's ability to predict changes in soil pH due to variable rates of lime. Data from 13 field experiments, in which soil parameters were measured 1 year after liming acid soils, were used to derive an index of pH responsiveness to lime (LRI) at each site. Multivariate analysis was used to derive a predictive model: LRI was found to be significantly correlated (P < 0.0001) with hydrogen ion concentration ([H+]x 105 ), exchangeable aluminium (Al), exchangeable cations (TEC) and percent organic carbon (C) data of the unlimed soils. The multivariate equation was then tested against an independent data set by comparing the predicted pH change with the measured pH change for eight soils. This evaluation, though generally acceptable, showed a small but significant deviation from the desired 1:1 ratio between observed and predicted pH change. We re-calibrated the model for the combined data to derive the model: LRI = 0.764 + 0.042 [H+] - 0.016 TEC - 0.097 Al - 0.016 C. When this model was tested over the whole data set for predicted v. measured pH changes, the following result was found: measured pH change = 1.01 (predicted pH change) - 0.05 (R2 = 0.85, n = 308). The implications of the predictive equation are considered with regard to the mechanisms that are thought to be associated with pH buffering.

Influence of Liming on the Susceptibility to Leaching of some Elements in Two Incubated Polish Soil

Abstract The objective of this work was to evaluate the contribution of liming to the leaching of C, N, P, Al, Fe, Mn, Cu and Zn compounds in soils. Samples (10 kg dry wt) of a virgin, sandy loam soil and a sandy soil in a rye field were limed with CaCO3 to neutralize 100% of the so-called hydrolytic acidity. They were then moistened to 100% maximum water-holding capacity and incubated for 4 months. During incubation, the soils were leached with 0.5 l deinoized water every week. The leachates were collected and their contents of dissolved substances, C, N, P, Al, Fe, Cu, Mn and Zn, were determined. The amounts of dissolved substances and leaching rates of elements investigated varied depending on soil history and liming. The amounts of dissolved substances and leaching losses of N and P were greater in the cultivated soil than in the displaced, virgin soil. C was more susceptible to leaching in the latter soil than in the former. Lime application significantly (P ≤ 0.05) increased the solubility of C and P in both soils and solubility of the metals in the virgin soil, whereas it decreased their solubility in the cultivated soil. Hence the liming of acid soils can enhance deficiences of certain nutrients in the soils. Further studies are required to determine whether in the long-term leaching could contribute to the contamination of aquifer under field conditions. Such knowledge is particularly important concerning N and P, which could trigger eutrophication.

Effects of difference in fertilization treatments on nitrification activity in tea soils

Abstract It is generally recognized that the nitrification activity in acid soils is very low. Indeed, nitrification in mineral soils has been found to be negligible at pH values below 5.0 (Dancer et al. 1973; Nyborg and Hoyt 1978). However, it was reported that autotrophic nitrification occurred in some tea soils at pH levels far below 5.0 (Walker and Wickramasinghe 1979; Hayatsu and Kosuge 1993). An acidophilic ammonia-oxidizing bacterium has been recently isolated from strongly acidic tea soils in Japan (Hayatsu 1993). On the other hand, fertilization has-been considered to be an important factor influencing nitrification in agricultural soils. For example, several studies have shown that the addition of ammoniacal fertilizer to soils can lead to the increase of the populations of Nitrosomonas (McLaren 1971; Ardakani et al. 1974). Liming of acidic soils also tends to stimulate the nitrification activity (Dancer et al. 1973; Nyborg and Hoyt 1978). Although nitrification has been studied in a wide variet...

The Importance of Liming Acid Soils of the Sahel Regions of Africa to Sustain High Crop Productivity—a Case Study from the Republic of Cameroon

SUMMARYGroundnut (Arachis hypogaea) has very great economic importance in Cameroon. In pot experiments, groundnut yields on highly acidified but limed soil were 50% greater than those on unlimed soil. These results demonstrate that severely acidified soils of the western highlands of Cameroon should be limed at moderate rates to sustain crop productivity.

EFFECT OF LIMING AND ADDING PHOSPHATE ON PREDICTED PHOSPHORUS UPTAKE BY MAIZE ON ACID SOILS OF THREE SOIL ORDERS

The effect of soil pH on P availability may vary with soils. We limed acid soils of three soil orders (Mollisol, Ultisol, and Oxisol, all with no significant slope differences) to five pH levels and incubated them for 10 days; then four P rates (0, 175, 350, and 525 mg P/kg) were added to each pH level, and we incubated them again for 21 days before examining the effects of soil pH and P rates on the P-soil reactions and predicted P uptake using the Barber-Cush-man nutrient uptake model. The reasons for the differences in P availability were evaluated. As the soil pH increased, values of PH (P concentration in soil solution) and P8i (anion resin exchangeable P) changed independently, and the degree of difference varied with soils. Increasing soil pH generally decreased Pli but increased Psi. Adding P caused a linear increase in Psi and a curvilinear increase in Pli; the increase was much greater in the Mollisol than in the Ultisol and Oxisol, probably due to a higher initial Pli in the Mollisol. Predicted P uptake decreased similarly with increased pH for all soils. Predicted P uptake by maize was controlled more by Pli than Psi.

Management practices to overcome the incidence of grass tetany.

To minimize the incidence of grass tetany, winter pastures should be established on soils containing Mg-rich minerals, drainage should be improved on five-textured soils, legumes should be included in the sward and soil pH should be at least 5.5. Liming acid soils with dolomitic lime increases forage Mg by supplying Mg and by raising soil pH. Calcitic lime applications also can increase Mg availability to plants on soils with adequate Mg. Low rates of application of soluble Mg salts (less than 100 kg/ha of Mg) effectively increase Mg uptake from noncalcareous soils with low cation exchange capacity. Potassium levels in soils and plants should be kept in the lower range of recommended values. Nitrogen application should be regulated to provide the desired level of forage production. Nitrogen fertilizers, especially the nitrate form, stimulate plant Mg uptake if Mg is available in the soil. The most practical and cost-efficient method of supplementing dietary Mg intake is to provide free-choice Mg. Supplements must be palatable and placed in locations frequently used by cow herds. Including a high-energy feed in the supplement may at times increase its preventive effectiveness by increasing Mg absorption and reducing lipolysis. Regardless of the supplement formulation, Mg intake should be monitored on a regular basis, and formulation or management changes should be initiated if Mg consumption is below required levels. In severe grass tetany outbreaks, foliar application of Mg or administration of Mg via the drinking water may be warranted.

Effect of Acidity on Nitrogen Mineralization and Nitrification in Atlantic Coastal Plain Soils

AbstractThe objective of this study was to determine the effect of acidity on mineralization, nitrification, and N2O evolution during these processes on naturally acid soils from the lower Coastal Plain of North Carolina. Six acid surface soils (pH ≤4.5) from the Tidewater region of North Carolina, with a range of organic matter (OM) contents (28‐850 g kg−1) were limed to give a range of pH values so that the effect of acidity on mineralization of organic N and nitrification of (NH4)2SO4 could be studied under controlled conditions in the laboratory. Cumulative net mineralization over 21 d was significantly (p <0.01) influenced by acidity in four of the six soils. However, no soil exhibited a significant net mineralization increase between the very acid initial pH value and the pH value to which liming is recommended (pH 4.8‐5.2 for Histosols) for crop production. Liming to pH values <7 increased net mineralization in only one soil. Adding a small increment of lime tended to decrease mineralization although this effect was significant in only one soil. Essentially all organic N mineralized was converted to NO‐3 at all pH values. However, the very high acidities tended to inhibit the nitrification of NH+4 added as (NH4)2SO4. There was apparently no influence of organic matter content on any of the processes studied except N2O evolution where the soils with <120 g OM kg−1 evolved the highest amounts of N2O during nitrification. Much of the N2O evolution was apparently due to denitrification because addition of nitrapyrin did not eliminate the evolution. It was concluded that the liming of acid soils in the Tidewater Region of North Carolina would have little influence upon N mineralization rates. The recommended pH values of 4.8 to 5.2 for Histosols appears to be adequate for both mineralization and nitrification.

Soil Acidity and Liming: II. Evaluation of Using Aluminum Extracted by Various Chloride Salts for Determining Lime Requirements

AbstractNeutralization of soil Al to a minimum value is one approach to liming acid soils. The objective of this study was to determine which chloride extracting solution removed the quantity of soil Al that readily reacts with limestone and reduces the Al saturation to < 15%. Soils were incubated for 8 weeks after being limed at rates needed to neutralize the Al removed by KCl, LaCl3, and CuCl2. Six soils with a range in organic matter contents were used. When the Al extracted by KCl was used to predict the lime rate, soils containing organic matter had a large amount of residual KCl‐extractable Al and a soil pH below 5.0. The lime rate predicted by the Al removed with LaCl3 reduced the residual Al to < 15% Al saturation for all soils. If residual Al is the criterion for evaluating limed soil, then LaCl3 is the best extracting solution. The LaCl3 not only removes the same amount of Al as KCl from the clay fraction of the soil, but also removes organically bound Al that influences the soil solution Al.

Adsorption of Phosphate by Hydroxy‐Aluminum Species on a Cation Exchange Resin

AbstractA study was conducted to provide a possible explanation for the reported decrease in the concentration of P in soil solutions with increasing pH and/or ionic strength. The assumption was made that P in solution decreases because of the formation of a new P‐adsorbing surface, the source of which would be exchangeable Al3+. An Al‐saturated resin was used as a model of an acid soil to study the effects of pH, charge and/or concentration of associated cation on the concentration of P in solution when the P‐adsorbing complex is affixed to a negatively charged surface. The hydroxy‐Al species formed by adding base was found to be the primary P‐adsorbing surface. The OH/Al molar ratio of the hydroxy‐Al species formed remained nearly constant with addition of base (2.0 to 2.1:1 in the presence of Ca(ClO4)2; 2.4:1 in the presence of NaClO4; µ = 0.003) until all the Al3+ present had been converted to the hydroxy‐Al form. The pH of formation of the hydroxy‐Al species was a function of µ and neutral salt cation.Phosphate was added at Al/P molar ratios of 12:1 or 6:1 in the presence of Ca(ClO4)2 or NaClO4 of equal ionic strengths (µ = 0.0003 or 0.003). The hydroxy‐Al species demonstrated a marked capacity to adsorb P. At an Al/P molar ratio of 2.0:1 (Ca(ClO4)2; µ = 0.003) the equilibrium concentration of P was < 0.2 mg/l. As % neutralization of exchangeable Al3+ increased, at constant total P concentrations, P in solution initially decreased, passed through a minimum, and then increased. The pH of minimum P in solution corresponds to the point where increased adsorption due to increasing adsorbing surface is balanced by increasing competition from hydroxyl ions for adsorption sites. Exchangeable Al3+ did not react with added P until the Al/P ratio of the hydroxy‐Al species equalled or became less than 2.0:1.The effects of µ and pH on P adsorption in the Al‐resin system are similar to many results reported in the literature for soil systems. Our studies suggest that the often observed correlation between exchangeable Al3+ and P fixation by soils is due to the relationship between Al3+ and the formation of the hydroxy‐Al species, unless the P addition rate is high enough to favor the precipitation of an aluminum‐phosphate compound. Hydroxy‐Al species formed by liming acid soils to above the pH at which all exchangeable Al3+ is converted to nonexchangeable forms appear to be stable enough to affect the concentration of P in solution over the short‐term, but may be unstable with respect to gibbsite or other Al minerals over long periods of time.

Effects of Soil pH on Forage Yield, and Chemical Composition of Sorghum and Millet1

AbstractMillet [Pennisetum typhoides (Burm.) Stapf and Hubbard] yields more forage than sorghum [Sorghum bicolor (L.) Moench] does in certain areas of the Southern Coastal Plain. Yield differences are associated with low soil pH in some instances. Experiments were conducted to elucidate the relation between soil pH, forage yield, and selected chemical composition of sorghum and millet.Management practices and plant nutrient applications were applied in a manner and at a level shown by other experiments to be adequate. The forage from both crops was analyzed for N, P, K, Ca, Mg, Al, and Mn. Upon completion of the experiment, soil samples were analyzed for P, K, Ca, Mg, Al, and Mn and soil pH was measured. Millet forage yield was unrelated to the soil pH in the pH range used. Sorghum forage yield increased 2,000 kg/ha when soil pH increased from 5.2 to 5.6. The concentration of Mg in sorghum forage was found to be greater at soil pH of 5.8 and above, while the concentration of Al and Mn decreased at a soil pH ≥ 5.2. The concentration of Ca increased more at soil pH ≥ 5.8; while the concentration of Al and Mn decreased at a soil pH ≥ 5.2. The concentration of Ca increased in millet forage at a soil pH ≥ 5.2; while P and Mg content increased at a soil pH ≥ 5.8.Based on this study, it is recommended that liming acid soils in the Southern Coastal Plain to increase soil pH increases sorghum forage yields and improves the mineral nutritional quality of both sorghum and millet forage.

White Phosphorus‐Ammonia Reaction Product as a Phosphatic Fertilizer in Alkaline and Limed Acid Soils1

AbstractWhite phosphorus dissolved in liquid ammonia yields an insoluble, black, phosphorus‐rich material. In alkaline and limed acid soils, this substance did not inhibit germination or seedling development of sorghum (Sorghum vulgare pers.) but supplied little or no phosphate to tomatoes (Lycopersicum esculentum, var. ‘manapal’). White phosphorus injected into the ammonia zone was available to the tomatoes as phosphates.