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1.
The quantity: potential relationships for Ca→K exchange in six soils were evaluated, where potential is defined by ΔGK,Ca+Mg. Using the percentage K saturation of the CEC as the index of quantity, the Worcester Series soil, rich in hydrous micas, was shown to have the highest concentration of K selective sites, and Newport Series soil, with mainly kaolinitic clay, the lowest. The other soils, containing mainly smectites, had intermediate K selectivities. An algebraic transformation of this relationship to separate the effects of exchangeable K and CEC showed that 0.01 m CaCl2 released more K than m ammonium acetate. From the exchangeable K : ΔG relationship, two regions of K buffering were observed for all but the Newport soil, the transition occurring at a mean ΔGK,Ca+Mg value of ?20.7 kJ mol?1, signifying the K concentration below which K from ‘perlpheral’ regions of micaceous minerals is released. This may explain why the percentage K saturation of the CEC of a soil cropped exhaustively (without K manuring) in the field does not drop below a minimum value. Based on pot experiments, exhaustion and optimum K potentials (ΔGexh and ΔGopt) were derived from second-degree polynomials fitted to the response curves of plant dry matter yield against ΔGK,Ca+Mg for five soils, the Worcester soil showing little response. ΔGexh was inversely related to the 2 : 1 layer silicate content of the soil (r2=0.98 and 0.94 for ryegrass and fescue respectively), and similarly, ΔGopt, to their CEC values (r2=0.74 and 0.77). Potassium uptake was more closely correlated with exchangeable K than with ΔGopt.  相似文献   

2.
To evaluate the effect of three phosphorus (P) fertilization regimes (no P, P input equivalent to P off‐take by crops, P input higher than P off‐take) on crop yield, P uptake, and soil P availability, seven field experiments (six in crop rotations, one under permanent grassland) were conducted in Switzerland during nine years (six trials) or 27 years (one trial). Soil total P (Pt), inorganic P (Pi), organic P (Po), and the amount of isotopically exchangeable soil P were measured in the 0–20 cm and 30–50 cm layers of the arable soils and in the 0–10 cm layer of the permanent grassland soil. Omitting P fertilization resulted in significant yield decreases only in one field crop trial as the amount of P isotopically exchangeable within one minute (E1min) reached values lower than 5 mg P (kg soil)–1. In the absence of P fertilization Pi decreased on average from 470 to 410 mg P (kg soil)–1 in the upper horizon of 6 sites while Po decreased only at two sites (from 510 to 466 mg P (kg soil)–1 on average). In all the treatments of the trials started in 1989 the E1min values of the upper horizon decreased on average from 15.6 to 7.4 mg P (kg soil)–1 between 1989 and 1998. These decreases were also observed when P inputs were higher than crops needs, showing that in these soils the highest P inputs were not sufficient to maintain the high initial available P levels. Finally for the six arable trials the values of the isotopic exchange kinetics parameters (R/r1, n, CP) and P exchangeable within 1 minute (E1min) at the end of the experiment could be estimated from the values measured at the beginning of trial and the cumulated P balance.  相似文献   

3.
Abstract

Soil cation exchange capacity (CEC) measurements are important criteria for soil fertility management, vaste disposal on soils, and soil taxonomy. The objective of this research was to compare CEC values for arable Ultisols from the humid region of the United States as determined by procedures varying widely in their chemical conditions during measurement. Exchangeable cation quantities determined in the course of two of the CEC procedures were also evaluated. The six procedures evaluated were: (1) summation of N NH4OAc (pH 7.0) exchangeable Ca, Mg, K, and Na plus BaCl2 ‐ TEA (pH 8.0) exchangeable acidity; (2) N Ca(OAc)2 (pH 7.0) saturation with Mg(OAc)2 (pH 7.0) displacement of Ca2+; (3) N NH4OAc (pH 7.0) saturation with NaCl displacement of NH4 +; (4) N MgCl2 saturation with N KCl displacement of Mg2+; (5) compulsive exchange of Mg2+ for Ba2+; and (6) summation of N NH4OAc (pH 7.0) exchangeable Ca, Mg, K, and Na plus N KCl exchangeable AJ. The unbuffered procedures reflect the pH dependent CEC component to a greater degree than the buffered methods. The compulsive exchange and the summation of N NH4OAc exchangeable cations plus N KCl exchangeable Al procedures gave CEC estimates of the same magnitude that reflect differences in soil pH and texture. The buffered procedures, particularly the summation of N NH4OAc exchangeable cations plus BaCl2 ‐ TEA (pH 8.0) exchangeable acidity, indicated inflated CEC values for these acid Ultisols that are seldom limed above pH 6.5. Exchangeable soil Ca and Mg levels determined from extraction with 0.1 M BaCl2 were consistently greater than values for the N NH4Oac (pH 7.0) extractions. The Ba2+ ion is apparently a more efficient displacing agent than the NH4 + ion. Also, the potential for dissolving unreacted limestone is greater for the Ba2 + procedures than in the NH4 + extraction.  相似文献   

4.
紫色土K+吸附解吸动力学研究   总被引：7，自引：0，他引：7       下载免费PDF全文
从国家紫色土肥力与肥料效益监测基地定位试验上 ,在第 10年水稻收获后从 0～ 30cm土层采取土壤样品 ,研究土壤K 吸附、解吸动力学过程。结果表明 ,不同施肥处理土壤K 吸附、解吸反应分别在2 4～ 32min和 4 6～ 6 4min达到平衡 ,吸附、解吸平衡量分别为 14 1～ 19 2cmolkg-1和 11 6～ 17 5cmolkg-1。相关分析说明 ,土壤阳离子交换量 (CEC)及粘粒含量是影响吸附平衡时间、吸附平衡量的重要因素 ;CEC、交换钾量是影响解吸平衡时间、解吸平衡量的重要因素。由此可见 ,长期不同施肥对土壤CEC、粘粒及交换钾量产生影响 ,从而影响了紫色土K 吸附、解吸平衡时间及吸附、解吸平衡量。平衡前钾离子的吸附、解吸速度及吸附、解吸率与反应时间lnt间存在良好的线性关系。其中反应速度直线和解吸率直线的斜率、初始反应速度及初始吸附率均与CEC、粘粒含量密切相关。Elovich方程和一级扩散方程分别为描述紫色土K 吸附、解吸反应的最优与最差模型 ,指数方程和抛物线扩散方程拟合性介于Elovich方程和一级扩散方程之间。由此可见 ,紫色土K 吸附、解吸过程不是一个单纯的过程 ,而是一个包括土体膨胀、吸附位活化、表面扩散等诸多因素的复杂过程。  相似文献   

5.
Potassium (K+) directly released from primary K‐bearing minerals can contribute to plant nutrition. The objective of this research was to assess short‐term K+ release and fixation on a range of intensively cropped calcareous soils. Potassium sorption and desorption properties and the contributions of exchangeable‐K+ (EK) and nonexchangeable‐K+ (NEK) pools to K+ dynamics of the soil‐solution system was measured using a modified quantity‐to‐intensity (Q : I) experiment. Release and fixation of K+ were varied among soils. The relation between the change in the amount of NEK during the experiment and the initial constrain was linear, and soil ability for K+ release and fixation (β) for all soils varied from 0.041 to 0.183, indicating that 4% to 18% of added K+ converted to NEK when fixation occurred. The equilibrium potential buffering capacity (PBC) for K+ derived from Q : I experiments had significant correlation (r = 0.75, p < 0.01) with β, indicating that PBC depends not only on exchange properties but also on release and fixation properties. The depleted soils showed higher β value than the other soils, indicating much of the added K+ was converted to NEK in case of positive constraint. The range of the amount of EK which was not in exchange equilibrium with Ca (Emin) in the experimental conditions was large and varied from 0.68 to 9.00 mmol kg–1. On average, Emin amounted to 64% of EK. This fraction of EK may not be available to the plant. The parameters obtained from these short‐term K+ release and fixation experiments can be used in plant nutrition.  相似文献   

6.
Potassium (K) exchange isotherms (quantity–intensity technique, Q/I) and K values derived from the Q/I relationship provide information about soil K availability. This investigation was conducted to study Q/I parameters of K, available K extracted by 1 N ammonium acetate (NH4AOc) (exchangeable K plus solution K), K saturation percentage (K index, %), and the properties of 10 different agricultural soils. In addition, the relationship of mustard plant yield response to the K requirement test based on K exchange isotherms was investigated. The Q/I parameters included readily exchangeable K (ΔK0), specific K sites (KX), linear potential buffering capacity (PBCK), and energy of exchange of K (EK). The results of x-ray diffraction analysis of the oriented clay fractions indicated that some mixed clay minerals, illite clay minerals, along with chlorite/hydroxy interlayered vermiculite and kaolinite were present in the soils. The soil solution K activity ratio at equilibrium (AR0) ranged from 8.0 × 10?4 to 3.1 × 10?3 (mol L?1)0.5. The readily exchangeable K (ΔK0) was between 0.105 to 0.325 cmolckg?1 soil, which represented an average of 88% of the exchangeable K (Kex). The soils showed high capacities to maintain the potential of K against depletion, as they represented high linear potential buffering capacities (PBCK) [13.8 to 50.1 cmolc kg?1/(mol L?1)0.5. The EK values for the soils ranged from ?3420 to ?4220 calories M?1. The percentage of K saturation (K index) ranged from 0.7% to 2.2%. Analysis of variance of the dry matter (DM), K concentrations, and K uptake of mustard plants indicated that there were no significant differences among the adjusted levels of K as determined by the exchange-isotherm curve.  相似文献   

7.
Abstract

In Oxisols, acidity is the principal limiting factor for crop production. In recent years, because of intensive cropping on these soils, deficiency of micronutrients is increasing. A field experiment was conducted on an Oxisol during three consecutive years to assess the response of common bean (Phaseolus vulgaris L.) under a no‐tillage system to varying rates of lime (0, 12, and 24 Mg ha?1) and boron (0, 2, 4, 8, 12, 16, and 24 kg ha?1) application. Both time and boron (B) were applied as broadcast and incorporated into the soil at the beginning of the study. Changes in selected soil chemical properties in the soil profile (0- to 10‐ and 10- to 20‐cm depths) with liming were also determined. During all three years, gain yields increased significantly with the application of lime. However, B application significantly increased common bean yield in only the first crop. Only lime application significantly affected the soil chemical properties [pH; calcium (Ca2+); magnesium (Mg2+); hydrogen (H+)+ aluminum (Al3+); base saturation; acidity saturation; cation exchange capacity (CEC); percent saturation of Ca2+, Mg2+, and potassium (K+); and ratios of exchangeable Ca/Mg, Ca/K, and Mg/K] at both soil depths (0–10 cm and 10–20 cm). A positive significant association was observed between grain yield and soil chemical properties. Averaged across two depths and three crops, common bean produced maximum grain yield at soil pHw of 6.7, exchangeable (cmolc kg?1) of Ca2+ 4.9, Mg2+ 2.2, H++Al3+ 2.6, acidity saturation of 27.6%, CEC of 4.1 cmolc kg?1, base saturation of 72%, Ca saturation of 53.2%, Mg saturation of 17.6%, K saturation of 2.7%, Ca/Mg ratio of 2.8, Ca/K ratio of 25.7, and Mg/K ratio of 8.6. Soil organic matter did not change significantly with addition of lime.  相似文献   

8.
Abstract

A greenhouse experiment was conducted to study the minimal exchangeable potassium (minimal K) status of fifteen smectite dominant soils and its relationship with K uptake and plant mobilization rate of soil reserve K. Exchangeable K reached minimal level decreasing about 35% from initial K status after 350 days of continuous cropping. Soils with high clay content and initial K status showed higher minimal exchangeable K. Cumulative K uptake by six successive crops varied from 160 mg kg‐1 to 823 mg kg‐1 and plant mobilization of soil reserve K varied from 0.151 mg kg‐1 day‐1 to 1.880 mg kg‐1 day‐1 among soils. Minimal K explained well the variation in total K uptake (r=0.85) and plant mobilization rate (r=0.83) as compared to initial exchangeable K status of soils (r=0.67 and 0.59, respectively) suggesting that the former is a better index of K supplying capacity of soils than the later.  相似文献   

9.
A long‐term fertilizer experiment, over 27 years, studied the effect of mineral fertilizers and organic manures on potassium (K) balances and K release properties in maize‐wheat‐cowpea (fodder) cropping system on a Typic Ustochrept. The treatments consisted of control, 100% nitrogen (100% N), 100% nitrogen and phosphorus (100% NP), 50% nitrogen, phosphorus, and potassium (50% NPK), 100% nitrogen, phosphorus, and potassium (100% NPK), 150% nitrogen, phosphorus, and potassium (150% NPK), and 100% NPK+farmyard manure (100% NPK+FYM). Nutrients N, P, and K in 100% NPK treatment were applied at N: 120 kg ha—1, P: 26 kg ha—1, and K: 33 kg ha—1 each to maize and wheat crops and N: 20 kg ha—1, P: 17 kg ha—1, and K: 17 kg ha—1 to cowpea (fodder). In all the fertilizer and manure treatments removal of K in the crop exceeded K additions and the total soil K balance was negative. The neutral 1 N ammonium acetate‐extractable K in the surface soil (0—15 cm) ranged from 0.19 to 0.39 cmol kg—1 in various treatments after 27 crop cycles. The highest and lowest values were obtained in 100% NPK+FYM and 100% NP treatments, respectively. Non‐exchangeable K was also depleted more in the treatments without K fertilization (control, 100% N, and 100% NP). Parabolic diffusion equation could describe the reaction rates in CaCl2 solutions. Release rate constants (b) of non‐exchangeable K for different depth of soil profile showed the variations among the treatments indicating that long‐term cropping with different rates of fertilizers and manures influenced the rate of K release from non‐exchangeable fraction of soil. The b values were lowest in 100% NP and highest in 100% NPK+FYM treatment in the surface soil. In the sub‐surface soil layers (15—30 and 30—45 cm) also the higher release rates were obtained in the treatments supplied with K than without K fertilization indicating that the sub‐soils were also stressed for K in these treatments.  相似文献   

10.
Background : Potassium (K) availability in soil and plant uptake is restrained by the dynamic interactions among the different pools of K. Aims : To understand these interactions, a study was undertaken to assess the quantity–intensity (Q/I) and buffering characteristics of rainfed maize (Zea mays L.) growing soils. Ten contrasting soils were evaluated for K partitioning changes in exchangeable K (ΔEK) and non‐exchangeable K (ΔNEK) pools in the soil‐solution phase and buffering characteristics using a modified version of Q/I approach. Results : The partitioned Q/I isotherms showed strong adsorption with the increase in K concentration ratio (CRK) and the changes due to ΔEK were higher than changes due to ΔNEK. Total buffering capacity (PBCK) significantly correlated (r = 0.92, p <0.01) with clay content with a major share contributed by buffering capacity owing to non‐exchangeable K ( PBC Δ NEK K ) rather than exchangeable K ( PBC Δ EK K ). The fixation capacity (β) factor, the magnitude of added K converted into a non‐exchangeable pool, ranged from 41 to 63%, whereas release (α) factor, the magnitude of added K converted to the exchangeable pool, ranged from 19 to 36%. Both threshold solution K (CKr) and threshold exchangeable K (EKr) values were found to be high in Satran clay loam (S2) and lower in Doon silty clay loam (S3) soils. The equilibrium exchangeable K (EKo) was found close to minimum exchangeable K (Emin) in Doon silty clay loam (S3) and Babaweyl sandy clay loam (S1) soils and overall Emin constituted about 8.94 to 0.57% of the EKo. Conclusion : It may be concluded that K Q/I isotherm partitioning provides a valuable insight to assess the dynamic relations. The ratio of α/β (K recharge index) could be used to evaluate the K enrichment capacity of soil to K additions while EKr and Emin can be potentially useful in the elucidation of exchangeable K as K fertility index especially in soils with poor K fertilizer management.  相似文献   

11.
Cation exchange characteristics of the K:Ca saturated forms of five soils were measured at 25°C and 50°C. The rates of isotopic exchange of 42K and 45Ca were too fast to be measured except that of 42K in the K:Ca Harwell soil at 25°C. The slower isotopic exchange of K in this soil was attributed to the presence of a zeolite, clinoptilolite. The intra-particle diffusion coefficient, Di, of K in this soil increased with K-saturation to a maximum at about 40 per cent K, probably because of the ‘blocking’ action of the larger hydrated Ca ions at small K-saturations in clinoptilolite. The CEC, measured by isotopic exchange along the K:Ca adsorption isotherm, decreased with increasing temperature probably because some interlayer spaces collapsed. The standard free energy, enthalpy, and entropy changes were negative for the reaction Ca-soil+2K+? 2K-soil+Ca++. These results seem to show that K is more strongly bound than Ca by the soil and that the Ca-preference shown by the isotherm at small external electrolyte concentration is caused by entropy changes in solution. Calculated activity coefficients of the exchangeable ions changed with K-saturation similarly at both temperatures but values at 50°C were smaller than at 25°C.  相似文献   

12.
Twenty surface soils from four main Soil Groups in Malawi and their sub-soils were divided into three groups based on cation exchange capacity (group I, CEC < 50; group II, 50–100; and group III > 100μeq g–1). In each soil group the maximum amounts of K removed by successive extraction with 0.005 M CaCl2 solution were well related to the potassium potential pK–0.5p(Ca + Mg), exchangeable K, ‘step K’, and the quotient ‘step K’/CR.K, where CR.K is ‘constant-rate’potassium. In Group III soils only, ‘step K’/CR.K values were significantly correlated with pH, clay, and CEC, and this suggested that the soils were relatively rich in K+ specific binding sites. In 27 soils from an NPK factorial experiment on tea, the rate of depletion of extractable K reserve increased with ammonium sulphate treatment, whereas K fertilizers tended to off-set significantly (P= 0.001) the depletion of K reserve. The values for the change in free energy ΔG =RT In aK/ (a(Ca+Mg)) ½, ranged from –12 to –16 kJ mol–1, and field observations showed that tea plants growing on soils having ΔG values less than –15 kJ mol–1 responded to K fertilizers. The investigation has indicated that heavily cropped soils are likely to show crop responses if the intensive cropping system does not include supplementation of K.  相似文献   

13.
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14.
A sample of Harwell soil containing 36 percent fine clay (< 0.3 μm) and 14 per cent coarse clay plus fine silt (0.3–5μm) was separated into fractions, and the K-supplying power of soil and fractions measured by cropping with ryegrass, exchange with Ca resin and double-label isotopic exchange with 42K and 45Ca ions. Mineralogical examination of the fractions coupled with the cropping experiments showed that the K-supplying power of the soil to ryegrass can be explained by the presence of a zeolite, clinoptilolite-heulandite, in addition to the clay minerals, mica, and interstratified illitic smectite, commonly found in a glauconitic clay-rich soil. The 0.3–5 μm fraction, containing much zeolite, has an exchange diffusion coefficient for K ions to Ca resin of 1.8 × 10?16 cm2sec?1 compared with a value of 5.7 × 10?20 for the < 0.3μm fractions in which interstratified illitic smectite is the dominant mineral. Isotopic exchange shows that all Ca ions in fractions < 50μm are isotopically exchangeable. In fractions coarser than 20μm, some of the K ions in felspar and mica were not exchangeable within the duration of the experiments.  相似文献   

15.
Abstract

Wide differences in levels of exchangeable K considered adequate for maximum yields in different States are probably a consequence of the acceptance of either a single 200 pp2m rate for 95–987. sufficiency suggested by Bray, or a variable level based on a percentage of the soil cation exchange capacity (CEC) proposed by Bear. It now appears that sufficiency levels should vary with soil CEC, but not merely as a simple percentage of it. Moreover, the relatiorshlp in practice is complicated by such factors as leaching of K from coarse textured soils, and fixation of added K in, and release of native K from, non‐exchangeable forms in soils high in micaceous clay content. Since these influences occur widely in Ohio soils, the need for new field studies was recognized and implemented. Laboratory and growth chamber studies relating K sufficiency to energies of exchange were examined. Also, a new procedure used by the Ohio Soil Testing Laboratory for providing K sufficiency baaed on soil CEC and crop yield and composition is described.  相似文献   

16.
To avoid over‐fertilization of potassium (K) and thereby a mineral composition in the grass crop not optimal for animal health, estimation of K release from soil is important. The analytical methods should therefore predict the total K release. Furthermore, to minimize costs for the farmers they should provide information which remains valid over a period of several years. The relationship between different soil extraction procedures for K and K uptake in ley for three subsequent years after soil sampling was studied in 19 field experiments on a range of mineral soil types in Norway. Potassium determined with solutions that extracted exchangeable K or parts of exchangeable K (0.01 M CaCl2, 0.5 M NaHCO3, 1 M NH4oAc, or ammonium acetate lactate) was significantly (p < 0.05) related to the K yield only in the 1st yr after soil sampling. Potassium extracted with boiling in 1 M or 2 M HNO3 was significantly related to the K yield only in the 2nd and 3rd yr. Potassium extracted with cold 2 M HCl, boiling 0.1 M HNO3 or 0.5 M HNO3 was significantly related to the K yield in all 3 yr after soil sampling. Among these extractants, 0.1 M and 0.5 M HNO3‐extractable K were better predictors of K uptake than 2 M HCl‐extractable K. These three extractants release some non‐exchangeable K in addition to exchangeable K. The fraction of 1 M HNO3‐K extractable with 0.1 M HNO3 varied from 4% to 45%, whereas from 15% to 78% of 1 M HNO3‐K was extractable with 0.5 M HNO3. Consequently, the more easily releasable fraction of K extracted by boiling with 1 M HNO3 varied considerably between different sites.  相似文献   

17.
Low phosphorus (P) availability in Ferralsols of the Malagasy Highlands is a major limitation to crop growth. Direct seeding mulch-based cropping practices which were adopted in the region to improve and sustain soil fertility are known to favour earthworms’ presence. The mesocosm study aims to analyse the effect of an endogeic geophageous earthworm species on the soil P status. Total P content (P t), NaOH-extractable P content, P ions (Pi) concentration (C p) in solution and rapid and slow reactions of Pi in solution with solid phase were determined in two Malagasy Ferralsols. Both C p and reactions rates were assessed in laboratory batch experiments using 32Pi labelling and isotopic exchange kinetics (IEK). The P t values were 836 and 349 mg P g−1 in a clayey soil and a sandy–clayey soil, respectively. For both soils, NaOH-extractable organic P was significantly higher in earthworm casts than in parent soils, whereas Pt was unchanged. Also, the effect of earthworm ingestion significantly changed parameters of the IEK. In casts compared with the soil from which they were derived, the immediate isotopically exchangeable Pi (E 1 min) increased by 116%, whereas relative rates of Pi release at the solid-to-solution with time were slightly lowered. The effect of earthworm ingestion on IEK corresponded to a transfer of slowly exchangeable Pi towards quicker Pi pools of exchange. However, according to the literature, the increase in E 1 min remained below the critical level for optimal growth, stating that the soils remained P-deficient even in the presence of active and numerous earthworms.  相似文献   

18.
Potassium (K), a plant nutrient with diverse roles to play in plant metabolism, is required in large amounts by most crops. It interacts with many other plant constituents to affect crop yield and quality. The magnitude of this interaction is high in areas of high cropping intensity, as in the tropics. The interaction of nutrients with K may be in the soil or in plant. Potassium modifies ammonium (NH4 +) ion fixation in soils to restrict nitrogen (N) availability. On the other hand, an antagonistic effect between K and NH4 absorption has been suggested in which K absorption is restricted. Similarly, magnesium (Mg) or calcium (Ca) deficiency occurs from ion antagonism in acid soils following K fertilization and in soils with high exchangeable K. Sulfur (S) has been reported to increase K absorption and productivity of oilseed crops. With increasing levels of applied or soil K, the severity of phosphorus (P)‐induced zinc (Zn) deficiency in corn has been observed to decrease. Application of K decreases manganese (Mn) content and iron (Fe) toxicity in rice. Application of K has been reported to decrease B levels in plants and to increase incidence of boron (B) deficiency. Top‐dressing with K fertilizer was reported to lower the copper (Cu) content of alfalfa forage. In root, sugar‐producing, or fiber‐producing crops, the sodium (Na) and K relationship is important with the specific response to either element depending on which element is in low or high supply. Molybdenum (Mo) stimulated K uptake in alfalfa and com. In intensive agriculture with high‐yielding single crops or with multiple crops per year, farm management must include strategies to maintain substantial K reserves in the soil and to balance K nutrition with other fertilization practices.  相似文献   

19.
Austrian winter pea (Pisum sativum subspecies arvense (L.) Poir) is grown as a cool season annual to produce high protein seed and forage as well as for soil fertility improvement. This legume is grown on a wide range of soil types with many different cropping systems. The objective of these studies was to determine the influence of K levels, with and without P and Ca fertilization, for increased growth, yield, nodulation and nitrogenase activity. Results were from 3 years’ field and greenhouse experiments with a Psammentic Paleustalf (Eufaula series) utilizing Rhizobium leguminosarum (Frank), ATCC 10314 as inoculum. Soil fertility effects on composition and histology of field‐grown nodules are presented.

Available soil P was a limiting plant nutrient in field studies with significant response to K resulting with PK combinations for top growth, tillers, pods, seed yield, nodule mass, and nitrogenase activity levels (C2H2, red.). Multiple regression for nitrogenase (umol C2H4 h‐1) = 1.09 tiller number + 3.37 nodule weight + 2.29 pod number, R2 = 0.837, C.V. = 29.9%. Results from the greenhouse experiments indicated significant responses with increased K application levels when combined with P and Ca fertilization for top growth, nodule weight, number of nodules and nitro‐genase activity. Highly significant correlations resulted with nitrogenase x nodule weight (r=0.538) and nitrogenase x top growth (r=0.359) with multiple regression of treatment effects for nitrogenase (μmol C2H4 h‐1) = 2.73 P + 1.04 K + 4.92 Ca, R2 = 0.797 and C.V. = 48.8%. Soil addition of plant nutrients resulted in significantly increased concentrations of those elements within nodules. Magnesium content was not consistently influenced by P, Ca, and K amendments. Sodium decreased with increased K fertilization. Multiple regression of elemental composition (mg g‐1 nodule) for nitrogenase (pmol C2H4 h‐1) = 0.21 P + 0.86 K + 2.35 Ca ‐ 2.01 Na, R2 = 0.772, C.V. = 55.6%. The proportion of plant nutrients in nodules contained within the nodule cytosol was highest for K (56.2%) and lowest for Ca (21.4%) with intermediate levels of Mg (50.2%), P (45.4%), and Na (37.2%).

Practical application from these data include the requirement of adequate available soil K for increased yield and nitrogen fixation with favorable P and Ca soil levels in Austrian winter pea production.  相似文献   


20.
Abstract

We examined soil potassium (K) supply capacity as related to wheat response to K fertilization, using a cation exchange membrane (CEM) burial technique to measure potential K supply rate. A growth chamber experiment was conducted to determine soil and plant response relationships. Canadian Prairie Spring wheat (Triticum aestivum ’Biggar') was grown on three soils of different initial K fertility with three rates of added K. Wheat response to K fertilization was well related to the amount of exchangeable K and K supply rate in the soil. Soils with high initial K supply rate demonstrated an adequate K release rate which was associated with low response to added K fertilizer. A soil K supply rate less than 5 μg cm2 hr‐1 represented soil K supply power that is less than optimal for wheat nutrition.  相似文献   

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