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1.
Potassium fixation capacity and mineralogical analysis of 24 representative soils, collected from southern Iran, were studied. Potassium fixation analysis was performed by adding six rates of K from 0 to 1000 mg kg?1 soil in a plastic beaker and shaking for 24 h. Mineralogical analysis showed that the clay fractions were dominated by smectite, chlorite, mica, palygorskite, vermiculite and quartz. In general, the studied soils fixed 8.5–55% of the added K. The potassium fixation capacity of the studied soils was significantly correlated with smectite content (r 2 = 0.87), clay content (r 2 = 0.60), cation-exchange capacity (r 2 = 0.79) and NH4OAc-K. Wetting and drying treatment and incubation time had significant effects on K fixation. The average percentage increase in K fixation following the wetting and drying treatment was 24 and 30% for surface and subsurface soils, respectively. The average percentage increase in K fixation with increasing residence time was 79 and 56% for surface and subsurface soils, respectively. Because K fixation is a diffusion process, time and increased concentration of soluble K (because of soil drying) are factors affecting the rate of K diffusion from a soil solution to the interlayer positions of the expansible 2:1 clay minerals.  相似文献   

2.
通过室内恒湿和干湿交替培养试验,研究了钾素受到生物耗竭的耕地棕壤对外源钾的固定特征和施用胡敏酸后对土壤固钾作用的影响。结果表明,在保持土壤处于饱和含水量的恒湿条件下,施用外源钾(K)483. 7mgkg-1,经过一天培养土壤的固钾量和固钾率分别达到265. 8mgkg-1和54. 95%,第3天土壤的固钾量达到最大值,为268. 0mgkg-1,再继续恒湿培养,土壤的固钾量有小幅度降低的趋势。然而,恒湿培养4天以后再经过风干1天,土壤的固钾量呈大幅度升高,固钾率提高30. 31%;在恒湿和干湿交替条件下培养,施用胡敏酸对土壤固钾状况的影响不同:施用胡敏酸不仅没有表现出降低土壤固钾量的作用,反而在第3个干湿交替循环周期结束后提高了土壤的固钾量,但在恒湿条件下施用胡敏酸表现出降低土壤固钾量的作用,与对照之间的差异达到了显著水平。  相似文献   

3.
Non-exchangeable potassium (Knex) contributes to soil K availability and several extractants are used to access its contribution. This study evaluated sodium tetraphenylboron (NaBPh4) as a soil test of K availability in 20 soils from Northern Greece. Winter wheat (Triticum aestivum L. var. ‘Yecora’) was sown in a greenhouse pot experiment and five cropping cycles were carried out until K-depletion. Soils were analyzed with NH4OAc and NaBPh4 (1 and 5 min incubation periods). Critical levels of K ranged between 130–140 and 330–340 mg K kg?1 of soil for NH4OAc and NaBPh4 (1 min incubation period), respectively, and between 32 and 35 g K kg?1 of wheat dry matter. NaBPh4-K (1 min) related better with K concentration and uptake compared to NH4OAc for each cropping cycle (r2 = 0.45–0.83 and 0.44–0.89) and for all soils (r2 = 0.58 and 0.51). Similar results obtained in soils low in exchangeable K (r2 = 0.41 and 0.39). Correlation between NH4Oac- and NaBPh4-extractable K was weaker among soils below the critical level (r = 0.70) compared to those above (r = 0.93). Inclusion of illitic K and cation exchange capacity in a multiple linear regression between NH4OAc- and NaBPh4-extractable K showed that they significantly contributed to NaBPh4-extractable K.  相似文献   

4.
Abstract

Fixation and recovery of added phosphorus (P) and potassium (K) were studied in different soil types of pulse‐growing regions. Amounts of P and K fixed increased in all the soils irrespective of type and texture. With the increase in levels of added P and K, maximum P fixation was observed at lower levels of added P (50 mg kg?1). Alfisols showed maximum P‐fixation capacity (92.7%), followed by Vertisols (86.5%) and Inceptisols (76.6%) at 50 mg kg?1 added P. However, K fixation increased with increasing levels of added K up to 200 mg kg?1, and thereafter fixation either decreased or was maintained at similar levels. Vertisols showed higher K fixation than Inceptisols and Alfisols. Fertilizer P requirement per unit increase in available P in soil was highest in Bangalore (3.23) and lowest in Delhi (2.38). Fertilizer K requirement per unit increase in available K in soil was highest in Raipur and Gulbarga (1.75) and lowest in Ranchi (1.28).  相似文献   

5.
Abstract

Potassium (K) fixation and release in soil are important issues in long‐term sustainability of a cropping system. Fixation and release behavior of potassium were studied in the surface and subsurface horizons in five benchmark soil series, viz. Dhar, Gurdaspur, Naura, Ladowal, and Nabha, under rice–wheat cropping system in the Indo‐Gangetic plains of India. Potassium fixation was noted by adding six rates of K varying from 0 to 500 mg kg?1 soil in plastic beakers while K release characteristics were studied by repeated extractions with 1 M HNO3 and 1 M NH4OAc extractants. The initial status of K was satisfactory to adequate. Potassium fixation of added K increased with the rate of added K irrespective of soil mineralogy and soil depth. Soils rich in K (Ladowal and Nabha) fixed lower amounts (18–42%) of added K as compared to Gurdaspur, Dhar, and Naura (44.6–86.4%) soils low in K. The unit fertilizer requirement for unit increase in available K was more in low‐K soils. The study highlights the need for more studies on K fixation in relation to the associated minerals in a particular soil. Potassium‐release parameters such as total extractable K, total step K, and CR‐K varied widely in different soil series, indicating wide variation in the K‐supplying capacity of these soils. K released with 1 M NH4OAc extractant was 20–33% of that obtained with 1 M HNO3. Total extractable K using 1 M HNO3 varied from 213 to 528 mg kg?1 and NH4OAc‐extractable K ranged from 71 to 312 mg kg?1 soil in surface and subsurface layers of different soil series. The Ladowal and Nabha series showed higher rates of K release than Gurdaspur, Dhar, and Naura series, indicating their greater K‐supplying capacity.  相似文献   

6.
This study aimed at quantifying nitrogen (N) and potassium (K) released from winery solid waste (WSW) composts during laboratory incubation to address deficiency in two texturally distinct soils. Composts had 4, 10, 20, 30, 40% (w/w) of filter materials (FMs) mixed with grape marc and pruning canes. The composts were mixed with the soils at equivalent rate of 200 kg N ha?1 and incubated for 42 days. Quantitatively higher (p < 0.05) ammonium N content was recorded in sandy than sandy loam soil during the incubation duration while exchangeable K was increased in K-deficient sandy soil. Cumulative total mineralized N (TMN) measured during the incubation duration ranged from 59 mg kg?1 to 672 mg kg?1 depending on compost type and soil texture while a 10-fold increase in compost FMs content resulted in 144% and 139% increases in cumulative mineralized K in sandy and sandy loam textured soil, respectively. Percent N mineralized from the composts relative to the amount applied during the incubation duration was less than 54% reflecting the composts and soils inherent characteristics. The high ammonium N and K mineralized suggests that farmers must be cautious in utilizing these composts for field crops production due to the potential environmental risks.  相似文献   

7.
The benefits of liming acidic or calcium (Ca)-deficient soils for soil structure and fertility are well documented. However, little is known about the effect of liming nearly neutral loess soils – lacking Ca – on interactions between soil nutrients. Over a 2-year period, 62 field trials were conducted in Germany and Austria with three treatments (0, 3 and 12 t CaO ha?1) on slightly acidic loess soils. Soil samples from the top soil layer were taken 4, 8, 16 and 24 weeks after liming. In addition to the pHCaCl2, the phosphorus (P), potassium (K) and Ca contents were analysed using electro-ultrafiltration (EUF). The application of lime increased the pH in average from 6.6 up to 7.0 and 7.2, but did not decrease EUF extractable P and K below the level of untreated control. Contrary to our expectations, EUF extractable P increased 4 weeks after liming in the treatment with 3 t CaO ha?1. At the end of incubation period, 24 weeks after liming, the EUF extractable K in treatment 12 t CaO ha?1 remained still 1.3 mg K 100 g?1 soil above the untreated control.  相似文献   

8.
This investigation was done to determine the release of potassium (K) from five calcareous soils of southern Iran using 0.025 M CaCl2, HCl and citric acid during six successive extractions and to study the K fixation capacity of the soils after K release experiment. Mineralogical study indicated that Vertisols and Mollisols were dominated with smectites; while other soils had illite, chlorite, palygorskite and smectite. Results indicated that citric acid extracted more K than CaCl2 and HCl (137 vs. 111 and 113 mg kg?1, respectively). The analysis of calcium (Ca), magnesium (Mg) and K concentrations in the solutions suggests that the exchange of K with soluble Ca and Mg (originated from dissolution of carbonates by acidic solutions) is the main mechanism of K release, but citrate is able to dissolve K-bearing minerals and release K in slightly calcareous soils. Soils with more illite released more K. Potassium fixation capacity of soils increased after extractions of soils with different extractants from 324 to 471 mg kg?1, with no significant difference. It is suggested to apply more K fertilizers in K-depleted calcareous soils and use of different solutions for extracting K from soil minerals may be a temporary and short term solution.  相似文献   

9.
华北与西北地区典型土壤固钾能力差异研究   总被引：1，自引：0，他引：1  
试验在我国华北和西北小麦玉米种植地区进行,研究了几种典型土壤在连续13年的K肥施用及小麦秸秆还田条件下耕层土对外源K素的固定能力差异.结果表明:相比常年只施NP肥处理,连续施用K肥或秸秆还田可显著降低土壤对外源K素的固定量,土壤固K量随环境溶液中K素浓度的增加而增加,但固定率下降.随土层变深,各定位点土壤固K量和固K率均随之增加,华北两定位点相对明显.轮作地区各处理0 ～ 20 cm土层土壤对外源K素的固定量(率)均远高于原始土壤,而单作区土壤的固K量(率)稍高或低于原始土.土壤固K能力表现出地带性规律,整体看取自华北两个定位点的土壤对外源K的固定能力强于取自西北两个定位点的土壤.  相似文献   

10.
Abstract

The diffusive mobility of fluoride (F) in soil (Entisol heplaquent) has been investigated as a function of soil water content and F‐concentration gradient. The data on F‐diffusion coefficients were recorded by determining the F‐concentration profile in horizontally incubated and homogenized soil columns, under varied experimental conditions (volumetric soil water content (θ)=0.12?0.25 cm3 cm?3, initial concentration of F at source ([F]t=0)=8?32 µM/g, pH=7.6±0.5, incubation time (t)=96 and 384 h, temperature=303±1.2 K). The effects of aluminum (Al) and calcium (Ca) ions, which are known to be strong binders for F in soil, on the F mobility have also been investigated by observing F diffusion in soils amended with externally added Al and Ca. The study suggests that F diffusion in soil increases with increase in θ and [F]t=0. Further, when the soil was amended with Ca, F diffusion was observed to decrease regularly with the increase in Ca amount. In Al‐amended soil, when Al concentration is raised, F diffusion increases, at 96 h incubation time but decreases at 384 h incubation.  相似文献   

11.
Effects of potassium (K) fertilization, cropping history, and soil mineralogy on K fixation and availability were investigated in three sugarcane development projects. Hence, water-soluble, exchangeable, nonexchangeable, and available K (sum of water-soluble and exchangeable) was evaluated in the three projects including Haft-Tapeh (H), Karun (Ka), and Sugarcane Development Project (T) with 41, 26, and 8 years of sugarcane plantation, respectively, in the Iranian soils of Khuzestan province. According to the results, K fixation ranged from 17.74 to 129.15 mg kg?1 and with increasing K levels, its amounts and percentage (P = 0.01) increased. With less than 30 years of plantation, there were not any differences in different plantation histories with regard to K fixation and availability. Evaluation of K dynamic based on long-term experiments can effectively contribute to the determination of appropriate rates of K fertilization for sugarcane production.  相似文献   

12.
Incubation and pot experiments were done to determine the effect of poultry manure on soil potassium (K) fractions and soybean K concentration. Representative soils from southwestern Nigeria were used. The treatments applied consisted of five rates of manure (0, 2.5, 5.0, 7.5, and 10 t ha?1). The experiments were arranged in a completely randomized design with three replicates. Soybean (TGx 1448-2E) was grown for three consecutive cycles (7 weeks each), analyzed for K. Order of abundance of soil fractions in the soil was as follows: Total K > non-exchangeable K > mineral K > > 1 N (hydrochloric acid) HCl K > 1 N (nitric acid) HNO3K > available K > exchangeable K > water-soluble K. Most of the K is in nonavailable forms; and the exchangeable forms are less than non-exchangeable forms. Organic manure increased soil K fractions, but these increases could not be sustained with cycles of soybean growth due to crop uptake.  相似文献   

13.
The potential of Nostoc 9v for improving the nitrogen (N)2–fixing capacity and nutrient status of semi‐arid soils from Tanzania, Zimbabwe, and South Africa was studied in a laboratory experiment. Nostoc 9v was inoculated on nonsterilized and sterilized soils. Inoculum rates were 2.5 mg dry biomass g?1 soil and 5 mg dry biomass g?1 soil. The soils were incubated for 3 months at 27 °C under 22 W m2 illumination with a photoperiod of 16 h light and 8 h dark. The moisture was maintained at 60% of field capacity. In all soils, Nostoc 9v proliferated and colonized the soil surfaces very quickly and was tolerant to acidity and low nutrient availability. Cyanobacteria promoted soil N2 fixation and had a pronounced effect on total soil organic carbon (SOC), which increased by 30–100%. Total N also increased, but the enrichment was, in most soils, comparatively lower than for carbon (C). Nitrate and ammonium concentrations, in contrast, decreased in all the soils studied. Increases in the concentration of available macronutrients were produced in most soils and treatments, ranging from 3 to 20 mg phosphorus (P) kg?1 soil, from 5 to 58 mg potassium (K) kg?1 soil, from 4 to 285 mg calcium (Ca) kg?1, and from 12 to 90 mg magnesium (Mg) kg?1 soil. Positive effects on the levels of available manganese (Mn) and zinc (Zn) were also observed.  相似文献   

14.
Mobility and bioavailability of lead (Pb) could be affected considerably by soil physicochemical properties;however,less is known about the effect of Pb levels and aging time.This study was conducted to evaluate the effects of Pb levels and wetting-drying (WD) cycles on distribution and bioavailability of Pb in three semi-arid zone soils treated with different levels of Pb(NO 3) 2.Wetting-drying cycles simulated the actual field irrigation in the semi-arid soils.A soil with a long history of Pb contamination was also taken as a reference soil.The soils were spiked with various levels of Pb and incubated under WD cycles for 160 d.Sequential extractions and batch sorption experiments were performed to assess the fractionation of Pb in the spiked soils.Redistribution index (U ts) and reduced partitioning parameter (I R) were applied to semi-quantify the distribution of Pb in the spiked soils.A small amount of Pb sorbed was desorbed by the soils,indicating a strong and irreversible binding of Pb in the studied soils.Contribution of carbonate-bound (Car) and residual (Res) Pb fractions to the total Pb of the soils was more than 97%.The Car,soluble plus exchangeable (SE),and organic matter-bound (OMB) fractions of Pb were transferred to the Res fraction under the WD cycles.The I R and U ts values were influenced by Pb loading levels and WD;therefore,the Pb lability and/or redistribution pattern could semi-quantitatively be assessed via these parameters.At the end of the experiment,the I R and U ts values for the Pb salt-spiked soils did not show the quasi-equilibrium state.The lability of Pb in the soils decreased with increasing incubation time and showed a strong dependence on Pb levels and soil chemical composition.WD cycles significantly affected the overall lability of Pb in soils through influencing the redistribution of Pb among solid-phase components.  相似文献   

15.
Abstract

Nonexchangeable potassium (K) release kinetics of six major benchmark soil series of India as affected by mineralogy of clay and silt fractions, soil depth and extraction media was investigated. The cumulative release of nonexchangeable K was greater in smectitic soils (353 mg K kg?1 at 0‐ to 15‐cm depth and 296 mg K kg?1 at 15‐ to 30‐cm depth, averaged for 2 soils and 3 extractants) than in illitic (151 mg K kg?1 at 0‐ to 15‐cm depth and 112 mg K kg?1 at 15‐ to 30‐cm depth) and kaolinitic (194 mg K kg?1 at 0‐ to 15‐cm depth and 167 mg K kg?1 at 15‐ to 30‐cm depth) soils. Surface soils exhibited larger cumulative K release in smectitic and illitic soils, whereas subsurface soils had larger K release in kaolinitic soils. Among the extractants, 0.01 M citric acid extracted a larger amount of nonexchangeable K followed by 0.01 M CaCl2 and 0.01 M HCl. The efficiency of citric acid extractant was greater in illitic soils than in smectitic and kaolinitic soils. Release kinetics of nonexchangeable K conformed fairly well to parabolic and first‐order kinetic models. The curve pattern of parabolic diffusion model suggested diffusion controlled kinetics in all the soils, with a characteristic initial fast rate up to 7 h followed by a slower rate. Greater nonexchangeable K release rates in smectitic soils, calculated from the first‐order equation (b=91.13×10?4 h?1), suggested that the layer edge and wedge zones and swelling nature of clay facilitated the easier exchange. In contrast to smectitic soils, higher release rate constants obtained from parabolic diffusion equation (b=39.23×10?3 h?1) in illitic soils revealed that the low amount of exchangeable K on clay surface and larger amount of interlayer K allowed greater diffusion gradients, thus justifying the better fit of first‐order kinetic equation in smectitic soils and parabolic diffusion equation in illitic soils.  相似文献   

16.
Abstract

This study was conducted to investigate the effect of time and rate of phosphorus (P) addition on phosphorus availability and phosphorus buffer coefficient in some calcareous soils. Phosphorus was added to the samples at rates of 0, 50, 100, 200, 400, 600 and 800 mg P kg?1 soil. The samples were incubated for 0.041, 1, 7, 14, 21, 30, 60 and 90 days at constant temperature and moisture. Extractable phosphorus was determined after the incubation. The results showed a sharp decrease in available P within 1 h after P addition. There was a linear relation between added P and extractable P in all soils. The buffer coefficients of soils were estimated by Olsen P for above incubation periods. Generally the buffer coefficient decreased with increasing time of incubation. The results indicated that inputs of between 23 – 59 mg kg?1 are required to raise Olsen P by 10 mg kg?1 in these calcareous soils, which assuming 2500 t soil ha?1, gives a required input of 58 – 148 kg P ha?1.  相似文献   

17.
A large proportion of phosphate fertilizer applied to calcareous soils reacts with calcium. Changes in soil phosphorus (P) availability after single application of biochar and phosphate-solubilizing bacteria have been reported. However, interaction of biochar (increasing soil pH) and phosphate-solubilizing bacteria (decreasing soil pH) on P availability in calcareous soil is not well known. An incubation experiment was conducted to study how the interactive effects of biochars (produced from wheat straw and cow manure at 300°C and 500°C with residence time of 1, 3 and 6 h) at different rates (0, 5 and 10 t ha?1) and phosphate-solubilizing Pseudomonas sp. IS8b2 affected on content of soil available P after 0, 60, 120 and 180 days of incubation (DOI) in a calcareous soil. After 60 DOI, the maximum value of available P (50.31 mg kg?1) was observed in the compound treatment of Pseudomonas sp. IS8b2 and wheat straw biochar (10 t ha?1) produced at 500°C with residence time of 3 h. We conclude that the combination use of wheat straw biochar and phosphate-solubilizing bacterium is promising to potentially improve soil P availability in calcareous soil, but further research at field scale is needed to confirm this.  相似文献   

18.
Potassium (K) leaching is detrimental to the maintenance of sustainable arable soil K fertility,especially in low-K fixation soils.It is not known whether the application of inorganic fertilizers with lower K mobility or crop straw can reduce potential K leaching in low-K fixation arable soils.The potential K leaching of 14 representative arable soils with different K fixation capacities in China was evaluated with or without the addition of K under two rainfall intensities (90 and 225 mm),and then potential K leaching was assessed in relation to five K sources (KCl,K2SO4,KH2PO4,maize (Zea mays L.) straw,and rice (Oryza sativa L.) straw).Without K addition,K leaching mainly occurred in sandy soils at 90 mm of rainfall and in soils with greater organic matter at225 mm of rainfall.With K addition,the leaching percentage of exogenous K ranged from 0.6%to 11.6%at 90 mm of rainfall and 1.2%to 21.2%at 225 mm of rainfall.The greatest K leaching occurred in soils with fewer K-bearing minerals and lower pH at both rainfall intensities.In most cases,KH2PO4,which has lower K mobility,markedly reduced K leaching in both high-and low-K leaching soils at the two rainfall intensities.Maize and rice straw reduced K leaching only in soils with high K leaching,regardless of rainfall amount,whereas more K was leached in soils with lower K leaching at high rainfall intensity.In conclusion,KH2PO4 and straw should be preferred for reducing K leaching in low-K fixation arable soils.  相似文献   

19.
Soil testing is an important diagnostic tool in determining nutrient imbalances and providing a basis for fertilizer application. The reliability and reproducibility of nutrient determination in soils is affected by the temperature of the extracting solution. We carried out laboratory investigations to account for the effect of temperature of the extractant on ammonium bicarbonate diethylene triamine penta‐acetic acid (ABDTPA)–extractable potassium (K), and developed a correction factor to standardize the results to a standard temperature. Forty soil samples with a wide range of characteristics were analyzed for ABDTPA‐extractable K at five laboratory temperatures, ranging from 15 to 35 °C. The soils represented soil textures varying from loamy sand to heavy clays. The electrical conductivity (EC) ranged from 0.14 to 47.8 dS m?1 (average 2.78 dS m?1), pH from 7.2 to 8.4 (average 8.0), lime from 3.7 to 22.4% (average 12.9%), organic matter from 0.25 to 1.43% (average 0.72%), and ABDTPA‐extractable K at 25 °C from 42 to 489 mg kg?1 (average 167 mg kg?1). The ABDTPA‐extractable K was positively correlated with temperature. Average values increased from 129 mg kg?1 at 15 °C to 225 mg kg?1 at 35 °C with R2 ranging from 0.63 to 0.997, and regression coefficient “b” ranged from 2.14 to 8.94. From the data, a temperature correction factor, Y = 2.85 + 0.01X (R2 = 0.46), was developed to convert ABDTPA‐extractable K determined at room temperature to a standard temperature of 25 °C.  相似文献   

20.
ABSTRACT

The 1 M ammonium acetate (NH4OAc) (AA) is the most widely used method for soil-test potassium (K), but other methods have been also suggested to estimate crop available K. The accuracy of these extractants may be influenced by soil texture and clay mineralogy. This study evaluated the relationships among AA, Mehlich-3 (M3), and sodium tetraphenylboron (TPhB) methods using soils differing in texture and clay minerals from the agricultural area of Uruguay. The M3 and AA extractable K concentrations were highly correlated (R2 > 0.97) across soils, although AA extracted slightly higher amount of K than M3. The TPhB method extracted more K than AA and M3, indicating that extracted K from different pools. The slopes of the relationships between TPhB and AA or M3 varied among soils being higher in fine-textured and illitic soils than in coarse soils. These results would be useful for evaluating the feasibility of incorporating M3 into a test program using the existing calibrations of the AA method. In addition, TPhB could be considered a complementary tool to improve the interpretations of the extractants to estimate soil-test K along with other characteristics such as the texture and clay mineralogy.  相似文献   

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