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1.
Cyclotriphosphate (Na(3)P(3)O(9)) and cyclotetraphosphate (Na(4)P(4)O(12)) are not strongly sorbed by soil constituents. Potential movement and efficient plant utilization of P from these compounds are dependent on the hydrolysis of the cyclophosphate ring structure and their hydrolysis products. The objectives of this study were to prepare pure useable quantities of these cyclophosphates and their hydrolysis products and to extract, separate, and analyze these compounds after application to diverse soils. Cyclophosphates of high purity (>99.0%) were prepared, and improved methods of extraction and analysis by ion chromatography were developed. Cyclophosphates and their hydrolysis products were extracted from soil using a sequential water/0.5 M H(2)SO(4)/1.0 M NaOH extraction that maximized P recovery and minimized hydrolysis of cyclic and linear phosphates during the extraction procedure. Gradient elution chromatography separated cyclic phosphates and their hydrolysis products. Separation and direct quantitative analysis of the applied cyclophosphates and their hydrolysis products were accomplished in <15 min.  相似文献   

2.
Influence of iron content in sewage sludges on parameters of phosphate availability in arable soils The use of iron salts for the P elimination in sewage plants is widely used. But it is not clear whether the P availability in arable soils is negatively influenced by iron compounds or not. The aim of the investigations was, therefore, to study the influence of two sewage sludges with a high and a low Fe content respectively on P sorption and phosphate concentration (Pi) in the soil solution after application of CaHPO4 or sewage sludge to 5 loamy and 4 sandy soils (pot experiments and 1 silty loam (field experiment)). Soils were analyzed 1, 6, and 13 months after P application. Sludge Gö contained 12 kg P and 65 kg Fe (t DM)—1 (P : Fe = 1 : 5.4) and sludge Sh 25 kg P and 39 kg Fe (t DM)—1 (P : Fe = 1 : 1.5). The basic P application was 60 kg P ha—1 (= 30 mg P (kg soil)—1 in the pot experiment, as sludge or as CaHPO4). P uptake by maize was determined in a separate pot experiment with a loamy soil and the same P application rate. The P sorption capacity remained similar in all soils after application of sludge Sh (P : Fe = 1:1.5) compared with soils without sludge, however, after application of sludge Gö the P sorption increased by 16% (0—59%). After application of sludge Sh the mean Pi concentration increased in loamy soils by 34% and in sandy soils by 15%. On the other hand the Pi concentration decreased after applying sludge Gö by 13% and 36% as compared to the controls of the respective soils. In the field experiment the Pi concentration of plots with a high P level (50 mg lactate soluble P (kg soil)—1) was also significantly decreased after application of 10 t sludge Gö (126 kg P ha—1) in comparison with triple phosphate. One month after the application of increasing amounts of sludge Gö (5, 10, 15 t DM ha—1) both the concentration of oxalate‐soluble Fe in the soil and the P sorption were increased. The elevated relationship between these two parameters was highly significant (r2 = 0.6 — 0.97). Plant uptake of P was less after application of sludge Gö than after application of sludge Sh and much less than P uptake from CaHPO4. Sewage sludges with a P : Fe ratio of 1 : 5 should not be recommended for agricultural use, as the P availability is significantly reduced. Iron salts should not be used for conditioning of sludges.  相似文献   

3.
Abstract

The phosphate sorption (P sor) capacity of soils increased when the soils were reduced (Willet and Higgins, Aust. J. Soil Res., 16, 319–326, 1978). The present study aimed at the elucidation of this mechanism using Na2S2O4 and 5 different soils. The P sor of the 5 soils increased with the addition of a small amount of Na2S2O4. Fe(II) was released from the soils with the addition of the same small amount of Na2S2O4. Furthermore, when the amount of FeCl2 corresponding to the amount of Fe(II) released along with the small amount of Na2S2O4 was added, the P sor of the soil increased. However, the P sor of the lowland soils, of which the hydrous Fe oxide content was lower than the others, decreased when the amount of Na2S2O4 addition was increased up to 150–200 g kg?1. Based on these results, the following process is inferred for the increase in the P sor of the soils when they are reduced. Hydrous Fe oxide in soil takes the form of very fine, high-density particles and reacts with P mainly on their surface. When a small amount of Na2S2O4 is added, the hydrous Fe oxide is partially reduced, dissolved and finally re-precipitates with P by oxidation with O2 from the air during the experiment.  相似文献   

4.
水磷一体化对磷素有效性与磷肥利用率的影响   总被引：14，自引：1，他引：14  
水肥一体化是发挥水肥耦合效应提高养分效率的重要途径,然水磷一体化研究较少。本文在模拟滴灌条件下研究了液体磷肥和固体颗粒磷肥(TSP)及其不同施用方法对土壤磷移动性、各形态无机磷含量动态变化的影响,比较了玉米磷素营养与磷肥利用率对不同磷源及其施用方式的响应,旨在提出滴灌条件下磷肥高效利用的最优策略。研究结果表明:1)与TSP肥料分次施用相比,液体磷肥分次施用更能提高土壤磷素有效性,在各土层Ca2-P与树脂磷(resin-P)平均含量分别提高12.4%与21.6%,且可显著提高磷在土壤中的移动性(P0.05),resin-P含量的垂直下降幅度降低56.5%;2)与TSP分次施用相比,液体磷肥分次施用的土壤中高活性无机磷含量(Ca2-P、resin-P及Na HCO3-P之和)占无机磷总量的比例提高21.0%,而低活性无机磷含量(Ca10-P与residue-P之和)占无机磷总量的比例则下降10.1%,说明液体磷肥分次施用可减小磷肥在土壤中的固定转化;3)玉米地上部干物质、叶片吸磷量和植株磷素累积吸收量均对不同磷源与施用方式有明显响应(P0.05),液体磷肥分次处理的玉米生物量、吸磷量及肥料利用率分别比TSP肥料分次处理提高27.1%、34.6%及61.4%。水磷一体化施用可提高磷在土壤中的移动性和有效性,减少磷的固定转化,显著改善玉米磷素营养,并明显提高磷肥利用率。  相似文献   

5.
The deposition of magnesium (Mg)‐rich dust from magnesite mining activities has resulted in serious land degradation. However, the main factors limiting plant growth in Mg‐contaminated soils are unclear. Moreover, little information is available on the remediation of Mg‐contaminated soils. In this study, remediation of soils contaminated with Mg‐rich dust was investigated in a pot experiment using maize as the indicator plant. There were five treatments: (i) control; (ii) leaching; (iii) application of CaCl2; (iv) leaching + CaCl2 application; and (v) application of Ca(H2PO4)2 · H2O. Soil properties and growth of maize (Zea mays L.) seedlings were measured. Leaching alone significantly decreased soluble Mg concentration. Leaching + CaCl2 application greatly increased exchangeable Ca concentration and decreased soil pH by 0·3 units. Application of CaCl2 alone increased soluble Mg concentration sharply, which directly inhibited the germination of maize seeds. Application of Ca(H2PO4)2 · H2O significantly increased the concentrations of exchangeable Ca and available phosphorus and decreased soil pH by 1·7 units. The biomass of maize seedlings increased in the order of control = leaching < leaching + CaCl2 < < Ca(H2PO4)2 · H2O. These results suggested that the plant growth in Mg‐contaminated soils was limited primarily by Ca deficiency and secondarily by high soil pH when exchangeable Ca was sufficient. High soil pH suppressed plant growth probably mainly by inhibiting phosphate uptake from the soil. Applying acid Ca salt with low solubility is an attractive option for the remediation of Mg‐contaminated soils. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

6.
Abstract

In semiarid and arid regions, plant growth is limited by high pH, salinity, and poor physical properties of salt‐affected soils. A field experiment was conducted in the semiarid region of Kangping in northeast China (42°70′ N, 123°50′ E) to evaluate a soil‐management system that utilized a by‐product of flue‐gas desulfurization (FGD). Soil was treated with 23,100 kg ha?1 of the by‐product. Results of corn growth were grouped into three grades (GD) according to stages of corn growth: GD1, seeds did not germinate; GD2, seeds germinated but corn was not harvested; and GD3, plants grew well and corn was harvested. The pH, electrical conductivity (EC), bicarbonate (HCO3 ?), carbonate (CO3 2?), exchangeable and soluble calcium (Ca2+), chloride (Cl), and sulfate (SO4 2?) in surface soils of the three grades (>20 cm) was measured to assess the correlation between corn growth and soil properties. Vertical differences in subsoil properties (0‐100 cm) between GD1 and GD3 were compared to known benchmark soil profiles. The FGD by‐product significantly increased EC, exchangeable and soluble Ca2+, and SO4 2? and decreased CO3 2?, exchangeable sodium (Na+), and soluble Na+. pH, EC, HCO3 ?, CO3 2?, and Cl? were higher in surface soils of GD1 than GD3. Soil hardness, soil moisture content, Cl?, and calcium carbonate (CaCO3) were higher in GD1 than in GD3, whereas the amount of available P was lower in GD1. Interestingly, the concentration of Cl?, a toxic element for plant growth, was 2.5 and 1.5 times higher in GD1 than in GD3 and control soil, respectively. In the comparison study of subsoils, GD1 and GD3 were classified as having typical characteristics of saline‐alkali soil (pH>8.5; exchangeable‐sodium‐percentage [ESP]>15; EC>4.0) and alkali soil (pH>8.5; ESP>15; EC<4.0), respectively.  相似文献   

7.
Abstract

Accurate measurement and characterization of phosphate rock dissolution are important for a better understanding of phosphorus (P) availability in soils. An incubation study was carried out on two New Zealand topsoils (0–15 cm; high P buffering capacity Craigieburn and low P buffering capacity Templeton) amended with North Carolina phosphate rock (NCPR) and water‐soluble phosphate (WSP) at 218 mg P kg?1 (equivalent to 60 kg P ha?1). Isotopic exchange kinetics was carried out after 12 h and 28 days of incubation to characterize P availability. This study showed that sensitivity of capacity factors (r1/R, n) to explain changes in E1min values was affected by the P buffering capacity of the soils. The recovery of applied P in the E pool (RecinE%) with extended incubation time was similar from the NCPR and WSP treatments (3.1–3.3%) in the Craigieburn soil compared with the Templeton soil in which RecinE% values were greater in WSP (9%) than NCPR (1.3%) treatment. The higher values of P derived from the applied P fertilizers in the E pool (PdffinE%>80%) suggested that the NCPR application in both soils would be efficient for increasing P availability to plants.  相似文献   

8.

Purpose

Crop growth on sandy soils can be increased by claying. In modified sandy soils, the added clay is in the form of peds ranging in size from millimetres to centimetres creating a highly non-uniform matrix where ped size could influence nutrient availability and organic C binding. The aim of the study was to determine the effect of clay addition rate and ped size in residue amended sandy soil on soil respiration, nutrient availability and organic C retention.

Materials and methods

In this study, clay peds of 1, 2 or 3 mm size derived from a clay-rich Vertosol (73 % clay) were added to a sandy soil (3 % clay) at clay addition rates of 10 and 20 % w/w. After the addition of ground faba bean residue (C/N 37) at 10 g kg?1, the soils were incubated for 45 days at 80 % of water-holding capacity.

Results and discussion

Clay addition had no consistent effect on cumulative respiration, but reduced NH4 + availability with a greater reduction at 20 % compared to 10 % clay and with 1 and 2 mm compared to 3 mm peds. Sandy soil with clay peds had a greater maximum NH4 + and P sorption capacity than sandy soil alone, and sorption capacity was higher at 20 % compared to 10 % clay addition and greater with 1 mm compared to 3 mm peds. Retrieval of clay peds at the end of the experiment showed ped breakdown during the experiment but also the formation of larger peds. Compared to the <53 μm fraction added at the start of the experiment, the total organic carbon (TOC) content of the <53 μm fraction was increased up to nearly two fold, particularly in the smaller peds (1 and 2 mm).

Conclusions

When sandy soils are amended with clay, N availability and organic C binding depend on both clay addition rate and ped size.
  相似文献   

9.
<?show $38#Bo;>Phosphorus fertilization effect of sewage sludges treated with iron compounds The result of waste water treatment with iron salts are sewage sludges with higher P but also Fe contents. The effect of such sludges on P availability in soils is not clear and was, therefore, compared with CaHPO4 as a P mineral fertilizer. In experiments (Mitscherlich pots, 6 kg soil) two sandy soils (pH 4.3 and 4.9), two luvisols ( pH 6.3 and 7.2), a loess (13 % CaCO3), and quartz sand all differing in their P status were treated with two sewage sludges which differed in their molar Fe:P ratios (sludge Gö: 1:0.3, sludge Sh: 1:1.2). For sludge Gö the P elimination had been carried out with FeSO4 and the sludge was stabilized with FeCl3 + Ca(OH)2 (filter press). For sludge Sh P was eliminated by FeCl3 in the aerobic basin. The first crop was maize (total shoot dry matter), the second red clover. In case of sludge Sh both crops took up in comparison to CaHPO4 the same amount of P from all substrates with the exception of quartz sand. The effect of sludge Gö was quite different: from the neutral luvisol soils maize was able to take up only 64—82 % P and red clover 77—82 % P only as compared to CaHPO4. On the sandy soils maize and red clover grew after sludge Gö as good or better than after CaHPO4 application and P uptake was quite similar (83—106 %). This result was concomitant to an increase of pH values (from 4.3 to 4.9, 4.9 to 5.6, respectively). The negative efficiency of P uptake in heavy soils after application of sludge Gö resulted from an increase of P sorption and decrease of orthophosphate concentration in soil solution. This sludge contains a high proportion of iron hydroxides/oxides with free sorption sites for P. In future P elimination from waste water should be done without iron salts. At least during the process of conditioning no Fe salts should be used.<?show $6#>  相似文献   

10.
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.  相似文献   

11.
Changes to soil nutrient availability and increases for crop yield and soil organic C (SOC) concentration on biochar‐amended soil under temperate climate conditions have only been reported in a few publications. The objective of this work was to determine if biochar application rates up to 20 Mg ha?1 affect nutrient availability in soil, SOC stocks and yield of corn (Zea mays L.), soybean (Glycine max L.), and switchgrass (Panicum virgatum L.) on two coarse‐textured soils (loamy sand, sandy clay loam) in S Quebec, Canada. Data were collected from field experiments for a 3‐y period following application of pine wood biochar at rates of 0, 10, and 20 Mg ha?1. For corn plots, at harvest 3 y after biochar application, 20 Mg biochar ha?1 resulted in 41.2% lower soil NH on the loamy sand; the same effect was not present on the sandy clay loam soil. On the loamy sand, 20 Mg biochar ha?1 increased corn yields by 14.2% compared to the control 3 y after application; the same effect was not present on the sandy clay loam soil. Biochar did not alter yield or nutrient availability in soil on soybean or switchgrass plots on either soil type. After 3 y, SOC concentration was 83 and 258% greater after 10 and 20 Mg ha?1 biochar applications, respectively, than the control in sandy clay loam soil under switchgrass production. The same effect was not present on the sandy clay loam soil. A 67% higher SOC concentration was noted with biochar application at 20 Mg ha?1 to sandy clay loam soil under corn.  相似文献   

12.
Abstract

A better understanding of nitrogen (N) availability to crops remains an essential key for a productive and safe production system. The main objective of this study was to evaluate the potential of anionic exchange membranes (AEMs) as part of a soil‐testing procedure to predict in situ soil NO3‐N availability for forage and corn produced in eastern Canada. The AEMs were buried in the surface horizon (0–15 cm) at four experimental sites for forage and at one site for corn. Treatments consisted of five NH4NO3 rates (0, 60, 120, 180, and 240 kg N ha?1) in forage and of six anhydrous ammonia (0, 50, 100, 150, 200, and 250 kg N ha?1) in corn production. In all sites, NO3 ? adsorbed on AEMs (NO3AEMs) increased significantly with N fertilizer rates, indicating the ability of the AEMs to detect differences between N fertilizer treatments and to predict the soil N availability to crops. The NO3AEMs fluxes were significantly related to soil NO3‐N concentration as extracted by water or KCl (0.66≤R2≤0.95). Significant relationships between crop N uptake and NO3AEMs were obtained (0.52≤R2≤0.94), suggesting that AEMs can be used as an index of soil N availability. Results indicated that AEMs provide a reasonably accurate evaluation of N availability to forage and corn. Because of their low cost, simplicity, and consistency over years, soils, and crops, AEMs could be efficiently used in soil N availability analysis.  相似文献   

13.

Purpose

Understanding organic carbon mineralization and its temperature response in subtropical paddy soils is important for the regional carbon balance. There is a growing interest in factors controlling soil organic carbon (SOC) mineralization because of the potential for climate change. This study aims to test the hypothesis that soil clay content impedes SOC mineralization in subtropical paddy soils.

Materials and methods

A 160-day laboratory incubation at temperatures from 10 to 30 °C and 90% water content was conducted to examine the dynamics of SOC mineralization and its temperature response in three subtropical paddy soils with different clay contents (sandy loam, clay loam, and silty clay soils). A three-pool SOC model (active, slow, and resistant) was used to fit SOC mineralization.

Results and discussion

Total CO2 evolved during incubation following the order of clay loam > silty clay > sandy loam. The temperature response coefficients (Q 10) were 1.92?±?0.39, 2.36?±?0.22, and 2.10?±?0.70, respectively, for the sandy loam soil, clay loam soil, and silty clay soil. But the soil clay content followed the order of silty clay > clay loam > sandy loam. The sandy loam soil neither released larger amounts of CO2 nor showed higher temperature sensitivity, as expected, even though it contains lower soil clay content among the three soils. It seems that soil clay content did not have a dominant effect which results in the difference in SOC mineralization and its temperature response in the selected three paddy soils. However, dissolved organic carbon (DOC; representing substrate availability) had a great effect. The size of the active C pool ranged from 0.11 to 3.55% of initial SOC, and it increased with increasing temperature. The silty clay soil had the smallest active C pool (1.40%) and the largest Q 10 value (6.33) in the active C pool as compared with the other two soils. The mineralizable SOC protected in the silty clay soil, therefore, had even greater temperature sensitivity than the other two soils that had less SOC stabilization.

Conclusions

Our study suggests that SOC mineralization and its temperature response in subtropical paddy soils were probably not dominantly controlled by soil clay content, but the substrate availability (represented as DOC) and the specific stabilization mechanisms of SOC may have great effects.  相似文献   

14.
The impact of horticultural management on carbon sequestration in soils has been limited so far to tillage and nitrogen fertilization. Our objective was to evaluate by mathematical modeling the effect of potassium fertilization on CO2 binding in cropland soils. The developed model integrates three subunits: (1) A published simulator of crop dry‐matter (DM) production in response to N, P, K fertilization, but not DM partitioning; (2) a published soil–crop–atmosphere model predicting crop yield and DM partitioning as a function of N but not K fertilization; (3) an original model computing the organic‐inorganic carbon transformations, inorganic‐carbon reactions and transport in soil, CO2 diffusion, and soil carbon sequestration. The model described the K‐fertilization effect on C binding in soil as a function of the soil pH, the Ca2+ concentration in the soil solution, hydraulic properties, air temperature, and crop DM production, and partitioning characteristics. In scenarios of corn (Zea mays L.) growth in clayey soil and wheat (Triticum aestivum L.) in loam soil, the computed K‐induced CO2 sequestration amounted to ≈ 14.5 and 24 kg CO2 (kg K)–1, respectively (0 vs. 100 kg ha–1 K application). The soil CO2 sequestration declined by 8% when corn grew in sandy instead of clayey soil and by 20% when the temperature was 10°C higher than the temperature prevailing in mild semiarid zones. All predicted CO2‐sequestration results were approximately 30‐fold higher than the 0.6 kg CO2 emitted per kg of K manufactured in industry.  相似文献   

15.
Applications of polyphosphate‐based fertilizers have been reported to have a positive impact on crop yields as compared to orthophosphate sources. Since plants take up P mainly as orthophosphate, hydrolysis rates of polyphosphates into orthophosphates will determine their fertilizer ability. Laboratory and soil incubation experiments were performed to evaluate hydrolysis rates of pyrophosphate (PP), tripolyphosphate (TP), and trimetaphosphate (TMP) in water as well as in two soils having different P‐fixing capacities. P availability was characterized by measuring the orthophosphate (ortho‐P) and polyphosphate (poly‐P) concentration in soil solution as well as the calcium‐acetate‐lactate (CAL)‐extractable amounts of both forms. In water, PP was completely hydrolyzed within 15 d, whereas TMP was hydrolyzed only to about 30% after 90 d. In the two soils, polyphosphates hydrolyzed during the incubation period increasing ortho‐P concentration in soil solution as well as in CAL extract. At the end of the incubation, no significant differences in ortho‐P concentration in soil solution and CAL extract were found in the sandy soil, whereas in the silty‐loam soil, polyphosphate applications resulted in higher soil‐solution ortho‐P concentration. Although polyphosphate hydrolysis is mainly affected by the soil‐specific enzymatic activity, it seems that polyphosphates and/or hydrolysis products are preferentially adsorbed/precipitated compared to ortho‐P in the silty loam, thereby influencing the P availability from polyphosphate sources.  相似文献   

16.
In a pot experiment, the P‐efficient wheat (Triticum aestivum L.) cultivar Goldmark was grown in ten soils from South Australia covering a wide range of pH (four acidic, two neutral, and four alkaline soils) with low to moderate P availability. Phosphorus (100 mg P kg–1) was supplied as FePO4 to acidic soils, CaHPO4 to alkaline, and 1:1 mixture of FePO4 and CaHPO4 to neutral soils. Phosphorus uptake was correlated with P availability measured by anion‐exchange resin and microbial biomass P in the rhizosphere. Growth and P uptake were best in the neutral soils, lower in the acidic, and poorest in the alkaline soils. The good growth in the neutral soils could be explained by a combination of extensive soil exploitation by the roots and high phosphatase activity in the rhizosphere, indicating microbial facilitation of organic‐P mineralization. The plant effect (soil exploitation by roots) appeared to dominate in the acidic soils. Alkaline phosphatase and diesterase activities in acidic soils were lower than in neutral soils, but strongly increased in the rhizosphere compared with the bulk soil, suggesting that microorganisms contribute to P uptake in these acidic soils. Shoot and root growth and P uptake per unit root length were lowest in the alkaline soils. Despite high alkaline phosphatase and diesterase activities in the alkaline soils, microbial biomass P was low, suggesting that the enzymes could not mineralize sufficient organic P to meet the demands of plants and microorganisms. Microbial‐community composition, assessed by fatty acid methylester (FAME) analysis, was strongly dependent on soil pH, whereas other soil properties (organic‐C or CaCO3 content) were less important or not important at all (soil texture).  相似文献   

17.
Anionic polyacrylamide (PAM) can prevent soil erosion, but its effect on fine particulate phosphorus (P), such as colloidal P, has not been thoroughly examined. The effects of PAM on the release potentials of water‐dispersible colloids (WDC) and total P, molybdenum‐reactive P (MRP), and molybdenum‐unreactive P (MUP) in the colloidal and truly dissolved phases (i.e., TPcoll, MRPcoll, MUPcoll, TPtruly, MRPtruly, and MUPtruly) from six soils across South China were tested in this study. The results showed that the release potentials of TPcoll in the control treatments were 6·9–46·1 mg kg−1 and generally highest in sandy loam soil. Following low (12·5 kg ha−1), middle (25 kg ha−1), and high (50 kg ha−1) levels of PAM application, the release potential of TPcoll decreased by 41·7, 63·2, and 77·4% compared to the control group, respectively. Additionally, PAM may trigger MRPcoll and TPtruly releases in sandy loam and/or silt soils, and for most soils, MRPtruly and MUPtruly showed the highest release potentials at middle or high PAM levels. A significant PAM application level by soil site interaction for the release potentials of WDC and colloidal P was observed. Multiple linear regression showed that the PAM rate combined with soil sand content can successfully predict the release potentials of WDC (R2 = 0·552, p  < 0·001) and TPcoll (R2 = 0·738, p  < 0·001). Our results suggest that PAM can effectively reduce the loss of soil colloids and colloidal P, while its effects are related to both application level and soil texture. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

18.
Abstract

Plants commonly suffer from phosphorus (P) deficiency in calcareous soils. Plant responses to P application on such soils mostly show poor correlation with their soil test P values. Experiments were conducted on 24 different soil samples under laboratory and greenhouse conditions to illustrate the relationship of various inorganic P fractions in different calcareous soils with P uptake by plants, P extraction by iron‐impregnated filter paper, and P soil test values estimated by 0.5M NaHCO3 and ammonium bicarbonate diethylene triamine penta‐acetic acid. Total P in the 24 soils ranged from 652 to 1245 mgkg?1 with a mean of 922 mgkg?1. A major proportion (98%) of inorganic P was in HCl‐P (Ca‐bound) form. The HCl‐P (Ca‐bound) ranged from 296 to 729 with a mean of 480 mgkg?1. The iron (Fe) and aluminum (Al)‐P (NaOH‐P) ranged from 0.92 to 12 mgkg?1 with a mean of 1.57 mgkg?1. The Fe‐P (citrate‐dithionite bicarbonate) ranged from 0.22 to 4.40 mgkg?1 with a mean of 5.99 mgkg?1. Data regarding P release from the soil matrix obtained by desorption with iron‐impregnated filter paper was best described by the Elovich equation. Range of slope and intercept values were found to be 5.48 to 17.3 and 17.23 to 56.27 mgkg?1, respectively. Intercept values calculated for the Elovich equation may be related to labile P initially available for plant uptake in soils. Intercept values calculated for the Elovich equation correlated (r=0.77) significantly (p<0.01) with NaHCO3 extractable (Olsen‐P)P. Significant correlation (p<0.05) of intercept with CDB‐P (r=0.44) and of slope with HCl‐P (0.43) suggested that the initially available P, regulated through CDB‐P, is replenished by HCl‐P [calcium (Ca) bound].  相似文献   

19.
土壤有效钾的吸附特征与钾肥有效性的研究   总被引：6，自引：0，他引：6  
应用化学分析、吸附试验和生物诊断方法及田间验证,系统研究了3种土壤钾的丰缺状况及钾的有效性和利用率。结果表明,3种土壤有效钾含量和对钾吸附能力为黑土＞淡黑钙土＞风砂土。由于土壤有效钾含量和吸附反应不同,钾生物有效性表现出较大差异。施钾风砂土增产49.4％,淡黑钙上增产273％,黑土增产13.1％。田间试验亦有相同趋势,在风砂土、淡黑钙土和黑土试验地上施用钾肥分别使玉米增产39.1％、24.5％和14.9％。最大产量钾肥施用量,黑土和谈黑钙土为100kg／hm2,其利用率为33.1％和38.9％,风砂土为50kg／hm2,其利用率为61.0％。  相似文献   

20.
Wood ash is a residual material produced during biomass burning. In the northeastern United States up to 80 % of the ash is spread on agricultural lands as a liming amendment with the remainder being disposed of in landfills. As well as raising soil pH, wood ash also adds plant nutrients to soil. This study is an examination of the plant availability of the P in 8 different soils amended with one wood ash. Plant availability was assessed by measuring the biomass and P concentration of corn (Zea mays) L.) plants grown in the greenhouse for 28 d in soil amended with either CaCO3 (control), wood ash to supply 200 mg kg?1 total P, or monocalcium phosphate (MCP) to supply 200 mg kg?1 total P and CaCO3. Both corn growth and P uptake were highest in the MCP treatments, intermediate in the wood ash treatments, and lowest in the controls for all soil types. The soil property which seemed to have the greatest influence on P availability was pH buffer capacity. The soils with the greatest capacity to buffer OH additions also tended to exhibit the greatest absolute P uptake from wood ash-amended soils and the greatest P uptake relative to that from MCP-amended soils. The ability of soil test extractants to predict uptake of P in the three soil treatments was examined. A buffered ammonium acetate extradant overestimated P availability in the ash-amended soils relative to the MCP-amended soils. An unbuffered, acid, fluoride-containing extract provided a measure of P levels that was consistent with P uptake from all soil treatments. In this study the predictive relationship was as follows: P uptake = 0.017× (Bray P, mg kg?1) + 1.19; r = 0.81.  相似文献   

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