Availability of Organic and Inorganic Phosphorus Fractions to Wheat in Toposequences of Calcareous Soils

Abstract

Information on the availability of different soil phosphorus (P) forms is useful for crop production. Phosphorus contents of 12 Iranian calcareous soils from upper‐, mid‐, and lower‐slope positions of two arid and two semiarid toposequences were fractionated to various organic and inorganic pools, and correlations of the P fractions with wheat responses were investigated. Among the inorganic P (IP) fractions, apatite type (Ca₁₀‐P) and dicalcium phosphate equivalents (Ca₂‐P) possessed the highest and the lowest amounts of P reserve in the soils, respectively. On average, about 20% of the total P was found in organic form (OP), of which 32% was labile (LOP), 51% was moderately labile (MLOP), and 17% was nonlabile (NLOP). The amounts of the soil P fractions were considerably influenced by the positions of the soils on the landscapes. The maximum contents of soil IP, Ca₂‐P, Fe‐P (iron‐bound P), and Ca₁₀‐P were observed in the lower‐slope positions. The amount of soil available [0.5 M sodium bicarbonate (NaHCO₃) extractable] P was significantly correlated with Ca₂P (r=0.895), Fe‐P (r=0.760), and Occl‐P (iron‐occluded P) (r=0.897). Direct correlation studies, however, showed that wheat shoot dry‐matter yield (DMY) was significantly affected by the amounts of Ca₂‐P, Fe‐P, OP, LOP, and MLOP fractions both at early (4 weeks) and late (10 weeks) stages of growth. All organic and inorganic P fractions, except Al‐P (aluminum‐bound P), Ca₈‐P (octacalcium phosphate equivalents), and NLOP, also showed significant relations to the amount and/or concentration of P in wheat tissues at 4 and 10 weeks after sowing. Among the measured soil properties, the amount of organic carbon was the most affecting factor on the size of the P fractions.     

Soil Boron Fractions and Response of Green Gram in Calcareous Soils

A greenhouse experiment with green gram on boron (B) deficient calcareous soils was conducted for two years at Ludhiana (Punjab), India to study soil B fractions and response of green gram to B application. Three soils with calcium carbonate (CaCO₃) content 0.8 (Soil I), 2.1 (Soil II) and 4.6 (Soil III) percent were collected from different sites of Ludhiana and Bhatinda districts, Punjab, India. The treatments comprised of five levels of soil applied B (0, 0.5, 0.75, 1.0, and 1.5 mg B kg^?1). The experiment was laid out in completely randomized design (CRD) factorial design with three replications. Readily soluble B comprised 0.39 to 0.76 percent in Soil I, 0.32 to 0.54 percent in Soil II, and 0.21 to 0.34 percent in Soil III of the total B, taking into account of all the levels of B applied at both stages of crop growth. Readily soluble B increased with increasing application rates of B and decreased from grand growth stage (40 days after sowing) to maturity of the crop. Specifically adsorbed, oxide bound, residual, and total B was higher in Soil III as compared to Soil II or Soil I. At maturity, specifically adsorbed B converted into other fractions to maintain equilibrium in soil solution. Organically bound B was greater than oxide bound B. Among all fractions, the residual fraction accounted for the major fraction of the total B. Soil application of lowest level of B was adequate to cause significant increase in dry matter yield and seed yield of green gram regardless of type of soil.     

Copper Release Behavior in Two Calcareous Soils Amended with Three Organic Materials

Understanding time-dependent copper (Cu) desorption behavior is critical for improving the prediction of Cu availability in soils. This study was conducted to evaluate the influence of municipal waste compost, sheep manure, and wheat straw on desorption characteristics of Cu and to evaluate the suitability of different kinetic models to describe the Cu release pattern in two calcareous soils. Diethylenetriaminepentaacetic acid (DTPA) and ethylenediaminetetraacetic acid (EDTA) were employed to extract Cu from soils. Best-fitted kinetic models including Elovich, simple Elovich, two-constant rate, and parabolic diffusion were selected based on their low standard error and high coefficient of determination. Extractable copper significantly decreased with increasing rates of sheep manure and wheat straw but increased with increasing rates of municipal waste compost amendment. Results revealed that copper was more readily desorbed from clay soil compared to silt loam soil. The copper desorption patterns were almost similar for both extractants; however, EDTA extracted more Cu from soils.     

Effect of Oxalic and Citric Acids on Zinc Release Kinetic in Two Calcareous Soils

Rate of zinc (Zn) release from solid to solution phase by organic acids can influence Zn availability in calcareous soils. The objective of the present study was to investigate the effect of different concentrations (1.1, 2.2, and 3.3 mM) of oxalic acid and citric acid on the kinetic release of Zn from two calcareous soils from Eastern Iran. The two organic acids showed significant difference in Zn release from studied soils. Cumulative Zn release during 72 h ranged from 5.85 to 10.4 mg kg^?1 in soil 1 and ranged from 8.7 to 16.9 mg kg^?1 in soil 2 using different concentrations of oxalic acid. The amount of cumulative Zn release after 72 h in soil 1 ranged from 13.65 to 28.77 mg kg^?1 and from 17.63 to 23.13 mg kg^?1 when different concentrations of citric acid was used. In general, Citric acid released 38% more Zn from soils than oxalic acid. The release of Zn from soils increased with citric acid concentration but decreased with increasing of oxalic acid concentrations in the solution. The simplified Elovich equation best described Zn release as a function of time (r² = 0.93 and SE = 0.78). From the present study, Zn release from soils can be limited by the higher concentration of oxalic acid, while citric acid is suitable for enhancing soil lability of Zn.     

Distribution and Availability of Zinc in Soil Fractions to Wheat on Some Alkaline Calcareous Soils

Experiments under laboratory and greenhouse conditions were conducted to investigate the response of wheat to Zn application in five loess-derived alkaline calcareous soils and to assess the contribution of Zn in various soil fractions on its uptake by plants. Zinc in soil extracted by different reagents was also determined. Total Zn ranged from 58 to 81 mg/kg. On an average 45% of total Zn in all soil fractions was associated with sand, silt and clay. Whereas silt alone held 33% of total Zn among soil fractions in the five soils. Ammonium acetate extractable and acid residual Zn (Sand, silt and clay) explained 98% of variation of Zn in plants, and 70 or 75% of Zn in the AB-DTPA extract and DTPA extract respectively. Application of 10 mg Zn/kg soil significantly (P < 0.01) increased plant shoot dry weight, Zn concentration and total Zn content in plants over control. Concentration of Zn in plants was significantly positively correlated with Zn extracted with DTPA and AB-DTPA in soils.     

Impact of Poultry Manure Application on Phosphorus Desorption in Some Calcareous Soils

Laboratory experiments were conducted to study the kinetics of phosphorus (P) desorption in different calcareous soils of Hamadan Province of Iran. Soils were fertilized with poultry manure at 50 ton ha^–1 and incubated at 25 ± 1 °C at 15% moisture for 6 months. The release rate of P was studied by successive extraction with 0.5 M sodium bicarbonate (NaHCO₃) over a period of 1–1752 h. Also, available P was determined. The results showed that available P in fertilized and unfertilized soils ranged from 13.3 to 55.1 and 10.0 to 50.1 mg kg^–1, respectively. Phosphorus desorption from the fertilized and unfertilized soils began with a fast initial reaction, followed by a slow secondary reaction. The amount of P released after 1752 h in fertilized and unfertilized soils ranged from 319.2 to 623.9 and 309 to 586.7 mg kg^–1, respectively. The amount of P released was significantly correlated with available P. The kinetics of cumulative P release were evaluated using the five kinetic equations. Phosphorus desorption kinetics were best described by the parabolic diffusion law, first order, and power function equations. Rate constants of these equations different in fertilized and unfertilized soils.     

Kinetics of Iron and Manganese Release from Contaminated Calcareous Soils

Knowledge of the release of heavy metals (HM) and their chemical speciation is necessary for characterizing HM behavior in soils. The kinetics and characteristics of iron (Fe) and manganese (Mn) release were studied in 10 contaminated calcareous soils using 0.01 M calcium chloride (CaCl₂), 0.01 M ethylenediamine tetraacetic acid (EDTA), and 0.01 M malic acid (malic acid) extractions. Iron and Mn in soil samples were fractionated before and after 2084 h kinetic release using a sequential extraction procedure. The proportion of Fe and Mn released by EDTA was greater than that with CaCl₂ and malic acid. A power model satisfactorily described Fe and Mn release from soils. In general, the mean release rate of Fe was greater than that of Mn, indicating a greater rate of Fe release from contaminated soils. It was shown that Fe and Mn distributions were similar in native soils and they were mainly found in Fe-Mn oxides and organic-matter (OM) fractions. There were changes in the proportional distribution of Fe and Mn in all soils during the 2084 h kinetic study with different extraction solutions. In general, the proportions of Fe and Mn associated with carbonate (CARB) and OM fractions tended to decrease, with corresponding increases in the Fe-Mn oxides for Mn and residual (RES) fractions for Fe during the kinetic study with all extraction solutions. The Fe and Mn solubility at the initial and final stages of release was controlled by siderite (FeCO₃), vivianite [(Fe)₃(PO₄)₂·8H₂O], MnCO₃(am), MnHPO₄, and rhodochrosite (MnCO₃) minerals in all extraction solutions. Based on a risk assessment and percentage of release of metals, there is a high potential for Mn release into the food chain from contaminated soils.     

Phosphorus Use Efficiency of Wheat Genotypes Grown in Calcareous Soils

ABSTRACT

Phosphorus (P) deficiency and low P-use efficiency are induced by soil properties, especially in calcareous soils, which are dominant in semi-arid regions of the world such as the Mediterranean region. Alternative approaches to P fertilization involve exploiting plant genetics in order to achieve more efficient use of P by the growing crop. Accordingly, in a greenhouse pot experiment, we evaluated P-efficiency in wheat genotypes grown in typical calcareous soils in southern Turkey. Ten common local genotypes were grown in six soil series for eight weeks using five P application rates (0, 25, 50, 100, and 200 mg P kg^?1). Dry matter (DM) yield and P content were significantly increased by increasing P rates, with significant differences between soils. Some genotypes performed better under P stress because of better P utilization efficiency. Shoot DM was the most sensitive indicator of genetic variability under P-deficient conditions. Genotypes classified as efficient-responsive (Adana-99, 1014, Golia, Balatilla) had above average DM yield when P was not added, and responded well to P applications; efficient-non-responsive genotypes (Firat-93, Seri-82, Genc-99, Panda) had below average DM yield, but responded to P applications; inefficient-non-responsive genotypes (Fuat Bey and Ceyhan-99) had below average DM yield; and no genotypes were in the inefficient responsive category. Such P response categorization is needed for better breeding programs for nutrient-use efficiency. The study may aid in selecting P-efficient genotypes in low-P soils, especially where little P is used. The use of P-efficient genotypes should be seen as complement to, rather than a substitute for, chemical P fertilization depending on local conditions.     

Genotypic Responses of Corn to Phosphorus Fertilizer Rates in Calcareous Soils

In the Mediterranean region, much emphasis is placed on the role of fertilizers in enhancing crop production to achieve food security. Given the complex nature of phosphorus (P) reactions in soils, considerable research has dealt with fertilizer aspects related to efficient P use, but comparatively less emphasis has been given to plant variation with respect to P efficiency. In this study, selection and adaptation of P‐efficient corn genotypes was seen as one possible approach to enhancing P efficiency. Thus, a greenhouse experiment with 10 corn genotypes (traditional to modern), five P application rates (0–200 mg kg^?1), and four field trials with three genotypes for 2 years were carried out on various calcareous soils (Vertic Torrifluvent, Vertic Calciorthid, Entic Chromoxerert, and Typic Xerofluvent). Measurements were made of root characteristics. Treatments in the field trials were five P application rates as main plots (0–68 P ha^?1) and three corn genotypes as subplots. Genotypes were selected for the field trials from the greenhouse experiment as “efficient‐responsive,” “efficient‐nonresponsive,” and “inefficient‐responsive.” Dry‐matter (DM) yield and plant P uptake by plants increased with P application rates in the greenhouse experiment. Root length and mass were considerably increased by increasing P levels. Genotypes were classified for P efficiency. The studies indicated that because corn genotypes respond to P‐fertilizer application differently, this trait could be utilized to exploit native and applied P more efficiently, especially at low levels of available P and when P‐ fertilizer use is limited. This differential response derives from morphological, physiological, and genetic variability among the genotypes. Although genotypic efficiency is important for fertilizer management, the contribution of the efficiency is not a substitute for fertilizers, especially if high yields are required. Nevertheless, breeding for P‐use efficiency should be a component of any program to improve crop yield potential.     

Potassium Fixation and Release in Some Calcareous Soils under Orange Cultivation

Eurasian Soil Science - Arid and semiarid soils of southern Iran may fix a large content of applied potassium (K), but the fixed K may be gradually supplied to plants. Sixteen representative soils...     

Adsorption Characteristics of Zn2+ Ions onto Different Aggregate Size Fractions of Some Calcareous Soils and their Relationship with Soil Properties

Eurasian Soil Science - Soils are exposed to potentially toxic trace elements (PTEs) such as zinc (Zn) through various ways. Adsorption of Zn in soils is one of factors affecting its availability...     

Role of Phenolics and Organic Acids in Phosphorus Mobilization in Calcareous and Acidic Soils

Abstract

Phenolic acids (caffeic, CAF; protocatechuic, PCA; p-coumaric, COU; and vanillic, VAN), catechol (CAT), poly-galacturonic acid (PGA), and citric acid (CIT) were compared for their effectiveness in phosphorus (P) mobilization in three soils differing in chemical properties. The addition of organic ligands at 100 μmol g^{? 1} soil increased the concentrations of resin P (P_r), water-extractable P (P_w), and bicarbonate-extractable inorganic P (P_bi), thus improving the phosphorus availability. The magnitude of P mobilization in the calcareous soil can be expressed in the following order: CAF > CAT > PCA = CIT > VAN > COU > PGA, which was consistent with the number of phenolic hydroxyl groups they contained and the position of carboxyl on the benzoic ring. In the two acid soils tested, the order of P mobilization was CIT > CAT > PCA > CAF after 24 h incubation, and CIT > PCA > CAF > CAT after a 14 d incubation. The mobilized P originated partly from the organic P fractions, which could be extracted by 0.5 M NaHCO₃. In addition, P_r decreased and P_w increased during incubation. The exceptions were that the CAF treatment increased P_r and the CIT treatment did not affect P_w. Calcium extraction from the soils after a 1 d or 14 d incubation could not fully account for the P mobilization. The results suggest that the inorganic P dissolution by the organic ligands was not the only mechanism of P mobilization in the calcareous soil, while in acid soils the chelation of metal cations by organic ligands is likely an important factor in P mobilization.     

砂质土壤磷素的组成特点与释放规律研究

砂质土壤磷素主要以可提取态形式积累,有很高的释放潜力。该类土壤磷素的释放受土壤pH、土水作用时间和土壤溶液化学组成等的影响。土壤酸化、土壤溶液中Na+浓度的提高及土壤与水的作用时间增加可促进土壤磷素的释放。用淋洗方法和平衡提取等2种方法对土壤磷素的释放评价表明,淋洗方法测得的P量较小,可代表土壤短期内P释放强度;而平衡提取法提取的P数量较大,可代表土壤P长期释放的容量。     

Phosphorus Management of Lucerne Grown on Calcareous Soil in Turkey

ABSTRACT

Lucerne or alfalfa (Medicago sativa L.) is grown as a forage crop on many livestock farms. In calcareous soils in eastern Turkey, lucerne production requires phosphorus (P) additions as the soils are naturally P deficient. Phosphorus sorption isotherms were used to estimate P fertilizer needs for lucerne grown for two years in a 3-cut system on a calcareous P deficient Aridisol in eastern Anatolia, Erzurum province, Turkey. Annual P applications ranged from 0–1200 kg P ha^?1. The Langmuir two-surface adsorption equation was used to derive the maximum P sorption capacity of unamended soil and to determine soil solution P, maximum buffer capacity (MBC), equilibrium buffer capacity (EBC), and P saturation at the optimum economic P rate (OEPR) for dry matter (DM) production. Soils were tested for Olson P at the onset of the study and after two years of P applications. In both years, tissue was analyzed for P content at flowering prior to first cutting. The OEPR (2-year average) was 754 kg P ha^?1 yr^?1 corresponding with a soil solution P concentration of 0.30 mg L^?1, a DM yield of 8725 kg DM ha^?1, and $528 ha^?1 annual profit. The P content of leaves at flowering increased linearly with P application beyond 100 kg P ha^?1 and was 3.2 g kg^?1 P at the OEPR. The unfertilized soil had an EBC, MBC, P saturation, and X_max of 3304 mL g^?1, 3401 mL g^?1, 6%, and 1086 mL g^?1, respectively, whereas two years of fertilization to the OEPR decreased EBC and MBC to 358 mL g^?1 and 540 mL g^?1, and increased P saturation and Olsen P to 56% and 32 mg kg^?1, respectively. These results suggest a P saturation >50% or Olsen P >30 mg kg^?1 are needed to maintain an optimum soil solution concentration of 0.30 mg L^?1 in this calcareous Aridisol. Similar studies with different soils and initial soil test P levels are needed to conclude if these critical soil test values can be applied across the region.     

Evaluation of Phosphorus Pools and Fractions in an Acid Tropical Soil Recapitalized with Different Phosphorus Sources

Abstract

Bray 1 phosphorus (B1P) and sequential phosphorus (P) fractions were determined on soils treated with triple superphosphate (TSP), Gafsa (GPR), and Christmas Island phosphate rocks (CIPR), respectively, with and without manure. The fractions extracted in decreasing lability were iron oxide–impregnated paper strip P (Pi‐strip P), inorganic (Pi), and organic (Po) bicarbonate (NaHCO3‐Pi and ‐Po), hydroxide [sodium hydroxide (NaOH)‐Pi and ‐Po], hydrochloric acid (HCl) P, and residual (residue P). The magnitude of B1P was in the order TSP>GPR=CIPR. Average B1P from PRs was two‐fold the amount in TSP, whereas that of the fractions was NaOH‐P>Residue P<sodium bicarbonate (NaHCO₃) P<Pi‐strip P <HCl. Bray 1 extracted mainly the most labile fractions (Pi‐strip P and NaHCO3‐Pi), and plant P uptake was correlated mainly to NaOH‐Po and NaHCO₃‐Pi. Magnitude of various fractions differed between TSP and PRs. Both B1P and the fractions were equally correlated to P uptake (R²=0.38**). Nevertheless, sequential fractionation appears to be a powerful tool to identify the P status and availability in soil.     

淹水土壤磷释放机理研究进展

磷是水体富营养化的主要控制因素,以农业磷为主的非点源污染通常是水体富营养化的主要来源。在许多农业地区,尤其在季节性洪水淹没的条件下,变化的环境因素导致农业土壤释放到水中的磷加剧。本文主要以影响磷释放吸附的因素为角度,综述了国内外淹水条件下土壤磷释放机理的研究进展,并指出了目前研究存在的问题,提出了建议。     

施磷对滨海盐土无机磷组分的动态影响

采用蒋柏藩、顾益初提出的土壤无机磷组分测定方法,在50d的培养过程中对滨海盐土的各无机磷组分进行了跟踪测定。结果表明:施入盐土中的无机磷在短期内主要增加土壤中的Ca2-P和Ca8-P的含量,而对A1-P、Fe-P和O-P的影响较小;施入盐土的无机磷首先转化成Ca2-P,然后再向Ca8-P、Ca10-P、Al-P、Fe-P和O-P转化;培养过程中,水分和温度的有利条件促进了土壤微生物的活动,加强了微生物对无机磷的固定。     

Phosphorus Fractions of Soils Treated with Phosphate Rock and Monocalcium Phosphate after Ryegrass Growth

Abstract

Excess EDDHA (ethylenediamine di(o‐hydroxyphenylacetic acid) ) had little effect on leaf concentrations of Fe in bush beans (Phaseolus vulgaris L. var Improved Tendergreen) when grown in nutrient solution at three pH values from 4.3 to 8.7. An excess of EDDHA 20 times that of Fe decreased yields slightly, but not as result of Fe deficiency. A resulting hypothesis is that chelated Fe can be transferred from chelating agent to uptake sites on roots without going in the ionic form through the solution around roots.     

Role of Different Soil Fractions in Copper Sorption by Soils

Abstract

To evaluate contributions of organic matter, oxides, and clay fraction to copper (Cu) adsorption in six characterized soils, adsorption isotherms and distribution coefficients were obtained by a batch experimental method. Copper adsorption isotherms from untreated soil, organic matter removed from samples, and organic‐matter‐ and oxide‐removed samples were compared with curve patterns and correlated to Langmuir and Freundlich models. Copper sorption data on untreated soils described L or H‐curves, whereas in soils deprived of any component, their curves were S‐type. Distribution coefficients allowed knowing Cu adsorption capacity of untreated soil and of organic matter, oxides, and clay fraction. Soil organic matter is the main component that affects Cu adsorption as long as soil pH is near neutrality. At acid pH, oxides are the main component that affects Cu adsorption, although to a much smaller extent than organic matter near neutral conditions. Soil pH is the main soil factor that determines Cu adsorption.     

Soil Phosphorus Available for Crops and Grasses Extracted with Three Soil-Test Methods in Southern Brazilian Soils Amended with Phosphate Rock

The Mehlich 1 (M1) soil-test method has been used for soil phosphorus (P) extraction in southern Brazil. The objective of this work was to compare M1, Mehlich 3 (M3), and ionic exchange resin (resin) soil-test methods to evaluate the soil P available for crops and grasses in soils amended with phosphate rock (PR). Oxisol and Alfisol received triple superphosphate (TS) and PR. The M1 solution extracted greater P amounts in soils amended with PR compared with the M3 solution and resin methods. Lesser P amounts were extracted with the M3 solution. Crops yields were better associated with the P amounts extracted with M3 and resin methods in soils amended with PR. The results showed that M1 overestimates soil P availability to plants in soils amended with PR; the M3 solution best estimated the soil P available for crops and grasses in soils amended with PR.