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This study aimed to assess potassium(K) 's potential mobility for some soils located in the Kurdistan Region of Iraq. Five soil samples were collected from a depth of (0-30) cm. For each sample, 5g of soil was equilibrated with 50 ml of 0.01 M CaCl2, amended with different K concentrations, and incubated for 24 h at 298 Kelvin. The supernatant was filtered, and K, Ca, and Mg were determined. Potassium exchange equilibrium was calculated from quantity-intensity (Q/I) isotherms. Mean AReK values for all studied soils ranged between 2.4x10-3 to 3.6x10-3(mol L-1)1/2, which reveals that K was preferentially held at inner potions. The amount of labile K(KL) ranged from 0.479 to 1.191cmolc kg-1 in studied soils. The highest value of KL was in Kanypanka while the lowest value was in Goizha. The potential buffering capacity (PBCK) was between 619.56 and 857.37 cmolc kg-1(mol L-1) -1/2. All studied soils were characterized by low percent K saturation and a high ability to replenish K concentration in the soil solution. Gapon selectivity coefficient was relatively high and ranged from 5.64 to 7.88 L mol-1. Higher values of KL indicate a greater K release into the soil solution. Such a high affinity of K to the solid soil phase was attributed to both the elevated organic matter content in these soils and their strong buffering capacities.

The Xenopus oocyte is a powerful system for the exogenous expression and functional characterization of plant membrane transport proteins. Until now, a number of potassium transporters and channels have been identified in oocytes expression system by the two-electrode voltage clamp technology. It is difficult to characterize K+/H+ anti-transporters, especially, electroneutral transporter. The K+ efflux assay system enables easy, fast, large-scale measurement of the transporters activity without two-electrode voltage clamp technology. This protocol describes a technique to measure the efflux activity of potassium transporter in oocytes expressing system.

In this paper, we’ve projected a two-warehouse inventory model for deteriorating things beneath the impact of inflation and continuance of cash, wherever demand follows a rare combination of the linear time variable and on-hand inventory level. In one in the entire warehouse (OW), time-varying linear deterioration was thought-about and within the different (RW) weibull distributed deterioration was studied. Here, shortages were allowed and part backlogged. The stock is transferred from the RW to the OW following a bulk unharness rule. The target here is to seek out the optimum amount to that ought to be ordered and also the optimum variety of cycles during which the number from RW should be transferred to OW to maximize world wide web profit per unit time. The model has additionally been exemplified with the many numerical examples. The results have additionally been understood diagrammatically.

Modelos não lineares são adequados para a descrição da liberação de nutrientes, uma vez que estimam quantidades de interesse prático e apresentam boa qualidade de ajuste. Embora seu processo inferencial seja baseado em argumentos assintóticos, existem meios de se conhecer a intensidade da não linearidade. Neste trabalho, avaliou-se a não linearidade de dois modelos de regressão não linear por meio das curvaturas de Bates e Watts, vício de Box e do estudo das propriedades amostrais dos estimadores de mínimos quadrados, obtido por simulação. Os dados são provenientes do estudo, ao longo do tempo, da liberação de K de quatro estercos animais em combinação com dois solos. O modelo Exponencial foi mais adequado, em termos inferenciais e para aplicação prática, uma vez que por todas as medidas apresentou menor não linearidade. Nonlinear models are appropriate to describe nutrient release, since they estimate quantities of practical interest and they have goodness of fit. Although its inferential process is based on asymptotic arguments, there are ways to know the nonlinearity intensity. In this work, we evaluate the nonlinearity of two nonlinear regression models through the curvatures of Bates e Watts, bias of Box and the least squares estimator sampling properties by simulation study. The data are from the study, over time, of the K release from 4 animal manure in combination with 2 soils. The exponential model was more appropriate in terms of inferential and practical aspects, since by all measures showed lower nonlinearity.

Soils of varying K status were selected at the BAU farm, Mymensingh and BADC farm, Madhupur for conducting laboratory, pot, and field experiments to see the dynamics of potassium in wet land rice soils. The soils were BAU-1(0.087 cmol/kg soil), BAU-2 (0.146 cmol/kg soil), Maddhupur-1 soil (0.097cmol/kg soil), and Madhupur-2 soil (0.706 cmol/kg soil). Almost neutral silt loam soils (Sonatola series) of BAU firm developed on the recent alluvial deposits of Old Brahmaputra Flood Plain and the acidic clayey soils (Noadda and Kalma series) of BADC farm developed on Madhupur clay. The laboratory experiments were potassium release capacity of soils, Q/I relationships of potassium. Results of the experiments showed that BADC farm soils released more K than BAU farm soils. The Q/I relationship showed that the equilibrium exchangeable K (EK0) and labile K (KL) of Madhupur-2 soil were higher than other soils. The potential buffering capacity (PBCK) was higher in BAU-2(5.19±0.12 cmol/kg (mol/L)1/2 soil followed by BAU-1 (4.07±0.09 cmol/kg (mol/L)1/2) and then Madhupur-2 soil (2.23±0.04 cmol/kg (mol/L)1/2). BAU farm soils adsorbed 55 to 60% of added K in non-exchangeable form, while it was 33 to 39% in BADC farm soils. DOI: http://dx.doi.org/10.3329/bjar.v36i4.11750 Bangladesh J. Agril. Res. 36(4): 633-646, December 2011

A high concentration of phosphate in the immediate vicinity of the phosphate fertilizer zone of soil could induce K release from K-bearing minerals to soil solution. In this study, the kinetics of K release by monoammonium phosphate (NH4H2PO4) from biotite, muscovite, and microcline were investigated. The results indicate that K release from all of these minerals was promoted by 1 M NH4H2PO4 (pH 4.0). The release of K from these minerals can be described by the zero-order rate equation. The rate coefficients of K released from the minerals (2–5 µm) in 1 M NH4H2PO4 solution ranged from 0.20 to 2.09 mg kg-1 h-1 at 25°C and from 1.22 to 9.00 mg kg-1 h-1 at 45°C, respectively. The amount of K release from the same mineral samples in 1 M NH4Cl solution (pH 4.0) at 25°C was not detectable and was too low to be determined accurately at 45°C. The dfferences in the rate of NH4H2PO4-induced K release from the different minerals were explained by the chemical composition, crystal structure, and the crystallization sequence of the minerals. The activation energies of the phosphate-induced K release from these minerals ranged from 37 to 72 kJ mol-1 and the pre-exponential factor values (Arrhenius equation) ranged from 1.2 × 106 to 7.2 × 1011 mg kg-1 h-1. The examination of the phosphate-reacted minerals shows the formation of crystalline NH4-taranakite in the muscovite and microcline systems and noncrystalline products in the biotite system. The absence of the formation of crystalline NH4-taranakite in the biotite system is attributed to the Fe perturbation. These data indicate that the major mechanism of NH4H2PO4-induced K release from the K-bearing minerals was the combined effect of phosphate and protons on the alteration of minerals. Therefore, the K-supplying rate of soils in the immediate vicinity of fertilizer zones may be enhanced through phosphate fertilization. Key words: Potassium release, kinetics and mechanisms, phosphates, potassium-bearing primary minerals

Alkalosis enhances human exercise performance, and reduces K+ loss in contracting rat muscle. We investigated alkalosis effects on K+ regulation, ionic regulation and fatigue during intense exercise in nine untrained volunteers. Concentric finger flexions were conducted at 75% peak work rate (∼3 W) until fatigue, under alkalosis (Alk, NaHCO3, 0.3 g kg−1) and control (Con, CaCO3) conditions, 1 month apart in a randomised, double-blind, crossover design. Deep antecubital venous (v) and radial arterial (a) blood was drawn at rest, during exercise and recovery, to determine arterio-venous differences for electrolytes, fluid shifts, acid–base and gas exchange. Finger flexion exercise barely perturbed arterial plasma ions and acid–base status, but induced marked arterio-venous changes. Alk elevated [HCO3−] and PCO2, and lowered [H+] (P < 0.05). Time to fatigue increased substantially during Alk (25 ± 8%, P < 0.05), whilst both [K+]a and [K+]v were reduced (P < 0.01) and [K+]a-v during exercise tended to be greater (P= 0.056, n = 8). Muscle K+ efflux at fatigue was greater in Alk (21.2 ± 7.6 µmol min−1, 32 ± 7%, P < 0.05, n = 6), but peak K+ uptake rate was elevated during recovery (15 ± 7%, P < 0.05) suggesting increased muscle Na+,K+-ATPase activity. Alk induced greater [Na+]a, [Cl−]v, muscle Cl− influx and muscle lactate concentration ([Lac−]) efflux during exercise and recovery (P < 0.05). The lower circulating [K+] and greater muscle K+ uptake, Na+ delivery and Cl− uptake with Alk, are all consistent with preservation of membrane excitability during exercise. This suggests that lesser exercise-induced membrane depolarization may be an important mechanism underlying enhanced exercise performance with Alk. Thus Alk was associated with improved regulation of K+, Na+, Cl− and Lac−.

In a pot experiment with five harvests of ryegrass the potassium (K) uptake from soil was studied in a clay and a silt soil, with (K1) and without (K0) K fertilizer. Ammonium acetate lactate-extractable K (K-AL) was rapidly depleted, and in K0 the K-AL level stabilized at 30 and 100 mg K kg -1 in the silt and clay soil, respectively. Corrected for different ''minimum'' values, the K-AL value predicted the K uptake by ryegrass from AL extractable K very well. In the silt soil the K release from reserve K (total K release from soil minus K release from K-AL) was small, whereas in the clay soil there was a substantial release from reserve K. Part of the reserve K in the clay soil was easily releasable and contributed to luxury consumption of K in the first crop. Acid-soluble K (K-HNO 3 minus K-AL) was a good parameter by which to assess the ability of the soil to supply ryegrass with reserve K. The results were compared with the results of the field experiments from which the soils were collected. The differ...

Aldosterone leads to an increase in urinary K+ secretion. To test for the cellular mechanism underlying K+ transport in the early distal tubule of the amphibian kidney, the K

RESUMO A produção e a decomposição de serapilheira de um fragmento de Floresta Atlântica de encosta na Ilha da Marambaia, Mangaratiba, RJ, foram estudadas durante o período de dezembro de 2003 a novembro de 2004. O aporte de serapilheira foi mensurado partindo de trinta coletores cônicos. A taxa de decomposição da serapilheira foi quantificada por meio de 36 sacolas de decomposição instaladas na área. Para avaliação da fertilidade do solo foram coletadas amostras nas profundidades de 0-5, 5-10 e 10-20 cm. A produção total de serapilheira foi de 7,9 Mg ha-1, sendo a maior deposição verificada no mês de novembro e a menor em junho. A fração foliar foi a de maior contribuição em relação às demais. A taxa de decomposição da serapilheira foi 40% em 7 meses de observação, seguindo modelo exponencial. Verificou-se comportamento diferenciado quanto à liberação de N, P e K. Com exceção do fósforo, os maiores valores de nutrientes, carbono e H+Al foram observados na camada superficial. ABSTRACT Litter production and decomposition of an Atlantic Forest fragment in Marambaia Island, Mangaratiba, RJ, were monitored from December 2003 to November 2004. For the litter deposition evaluation, 30 litter traps were installed and 36 litter bags were allocated in the area to quantify litter decomposition. Soil samples were collected at 0-5 cm, 5-10 cm and 10-20 cm depth to evaluate soil fertility. The litter production was 7.9 Mg ha-1 and the highest deposition was verified in November and the lowest in June. The leaf fraction presented the highest contribution comparing to the others. In seven months of observation, litter decomposition rate was 40% and showed an exponential decrease. Different behavior for N, P and K release was verified. Exception for P, carbon, nutrients and H+Al presented highest concentrations in superficial layer.

A produção de biomassa, a manutenção dos resíduos vegetais sobre o solo e sua posterior decomposição são fatores de grande importância no estudo da ciclagem de nutrientes. Este estudo foi desenvolvido na área experimental do CEFET-Uberaba-MG, onde foram avaliados oito tipos de coberturas vegetais: milheto (Pennisetum americanum sin. tiphoydes), braquiária (Brachiaria brizantha), sorgo-forrageiro (Sorghum bicolor L. Moench), guandu (Cajanus cajan (L.) Mill sp.), crotalária (Crotalarea juncea), aveia-preta (Avena strigosa Schreb), pousio e área em preparo convencional de solo (testemunha) em área de Cerrado, na região do Triângulo Mineiro. Avaliaram-se a fitomassa seca (FS), a decomposição dos resíduos em bolsas de decomposição, e a liberação de K. Utilizou-se um modelo matemático para descrever a decomposição dos resíduos e a liberação de K, e calcularam-se a constante de decomposição (k) e o tempo de meia-vida (T½). O milheto, o sorgo e a crotalária foram as coberturas que apresentaram maiores produções de matéria seca. O maior acúmulo de K ocorreu em gramíneas e a maior liberação de K ocorreu no milheto, aveia, braquiária e crotalária nos primeiros 42 dias após manejo, nos dois períodos avaliados. A braquiária apresentou o menor T½ vida e a maior taxa de liberação de K. Crop residue production, plant residue maintenance and their decomposition are important factors in the understanding of nutrient recycling process. To evaluate K accumulation and release a study with eight cover crops types was developed: pearl millet (Pennisetum americanum sin. tiphoydes), brachiaria grass (Brachiaria brizantha), sorghum (Sorghum bicolor L. Moench), pigeonpea (Cajanus cajan (L.) Millsp), sunn hemp (Crotalarea juncea) and black oats (Avena strigosa Schreb), fallow land and conventional culture (control) in the experimental area of CEFET-Uberaba-MG, in a Cerrado area. The dry mass production, crop residue decomposition in litter bags and K release were evaluated. A mathematical model was used to describe residue decomposition and K release, which calculates the decomposition constant (k) and half-time life. Pearl millet, sorghum and the sunn hemp were the cover crops that produced most dry matter while K accumulation was highest in the grasses. K release was highest in pearl millet, oats, brachiaria grass and sunn hemp in the first 42 days after handling. Brachiaria grass had the shortest half-time life and the highest K release rate.

Liming and parent material had major effects on the potassium (K) quantity/intensity (Q/l) relationships of a varied group of naturally base-depleted upland soils of the western Cape. Departures from the usual Q/l curve form were observed, the individual curve sections probably representing specific exchanger states. K buffering (PBCK) in the limed Bokkeveld shale (BS) soils was 4,0-fold that of the limed granite and 6,5-fold that of the limed Table Mountain sandstone (TMS) soils. The response in terms of PBCK to liming by the BS soils was 4,7 and 5,1-fold that of the granite and TMS soils respectively. The granite soils were characterized by high levels of K release (ΔKo), that from the unlimed granite soils being 15,9-fold that from the unlimed BS soils. Relative to the TMS and BS soils, liming had a very limited effect on Δo in the granite soils.

Diurnal changes in K content in leaf blades, petioles, stems and roots of eleven lucerne genotypes were followed. Significant positive correlations between changes in K content in petioles and upper half of stems and significant negative correlations between changes of K content in leaf blades and lower half of stems reflected rapid K movement. The velocity — up to 60 μmol g−1 (f.m.)h−1 — of changes in K content from leaf blades to lower part of stems and the other way round showed that long distance phloem transport occurred. Only moderate increase of K content contemporarily took place in roots. When total K amount in the whole plant was calculated then K uptake alternatively with K release were noticed during the day. Average K release reached 1.48 μmol g−1 (f.m.) h−1. The rate of K movement correlated with irradiance and physiological activity of plants. The time course of K movement was uniform in plants of the same strain and it differed partially in different strains.

Twenty-one representative soils from Northern Greece could be grouped into three categories based on the EUF-K curves which displayed marked differences in the magnitude of K release by the soils employed. The cumulative K desorption by EUF within 35 min and the cumulative K-uptake values of ryegrass (10 cuts) were found to be correlated (r=0.87***). Although this correlation is rather close, the K dynamics of a soil can be better characterized by the course of the K-desorption curves. Because the quotient EUF-K-80°C/EUF-K-20°C can give information on the course of K desorption it is therefore sufficient in routine investigations to know the EUF-K-20°C contents and the numerical values of the quotients EUF-K-80°C/EUF-K-20°C.

Total K, Na, Ca and Mg in the sand, silt and clay of six British and four Malayan soils and the proportions released to H+‐resins in 1 h, 3, 10, 23 and 43 days were measured. The clays contained and released to the resins more K and Mg than coarser fractions. The release was continuous except from the acid Malayan soils which stopped releasing K after 3 days. More Mg was released to the resins than K, although no non‐exchangeable Mg but much non‐exchangeable K was released to ryegrass grown in the soils (after liming). This suggests that H+‐resins caused structural decomposition of the clay minerals which, together with the anomolous K release from acid soils, would limit their usefulness for measuring soil cations available to crop RESP-6773

Palytoxin (PTX) caused K+ release from rabbit erythrocytes at a concentration as low as 10−11 M. The K+ release due to PTX at a concentration below 10−9 M was dependent on Ca2+ in medium. The effect of Ca2+ was substituted fully by Sr2+ and partially by Ba2+. W-7 (2 × 10−4 M), a known inhibitor of calmodulin, markedly inhibited the rate of K+ release due to PTX. W-5 (2 × 10−4 M), an analog of W-7 with lower affinity to calmodulin than W-7, showed weaker inhibition. Other calmodulin antagonists, such as prenylamine, chlorpromazine and compound 48 80 , also inhibited the PTX-induced K+ release. These results suggest that the K+ release induced by PTX involves the process(es) mediated by intracellular Ca2+ and calmodulin.

The retention and release of K from ‘No K ’and K‐treated soils from the Rothamsted Classical Experiments and Saxmundham Experiment were examined using K‐Ca exchange equilibria and the kinetics of K release to Ca‐saturated resin. Free energies and enthalpies of Ca→K exchange showed that Saxmundham soils had the greater preference for K, and that residual K from long‐term manuring significantly decreased K binding strength and preference. K release kinetics showed that residual K increased the rate of K release chiefly from the ‘surface’ region, and the amount of K released from ‘surface’ and ‘peripheral’ regions of 2:1 layer silicates in soils. The increased K release from ‘peripheral’ regions of K fertilised soils, together with their decreased K preference, was associated with slowly reversible K fixation on the weathered periphery of 2:1 layer silicates. RESP-08324