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1.
评价土壤磷素植物有效性的物理化学指标   总被引：7，自引：2，他引：7       下载免费PDF全文
室内分析结合温室盆栽试验研究了土壤磷素植物有效性和无机磷酸盐的解吸特性之间的关系。供试材料为浙江省分布较广的四种代表性土壤,并以吸磷能力较强的黑麦为指示植物。结果表明,在四种供试土壤上黑麦吸收磷与解吸磷之间的相关性都比与两种常规化学方法浸提磷之间的相关性更为显著。不仅如此,黑麦吸收磷与解吸磷间在数量上较化学浸提磷要接近的多,并且在各供磷强度下以及不同土壤上都符合较好。黑麦吸收磷或解吸磷(Q)随土壤供磷强度(I)变化的Q—I关系能够很好地符合Langmuir方程;而Olsen-P和Brayl-P对供磷强度的关系与该方程的符合性在酸性土壤上要差得多。可见,植物吸收磷与磷酸盐解吸有内在联系。结果还表明,由拟合Langmuir方程计算得的最大解吸缓冲容量(MBCD)能够很好解释不同性质土壤间磷肥利用率的差异,它较之最大吸附缓冲容量(MBCA)能够更好指示土壤中磷的植物有效性。但平衡解吸缓冲容量反映土壤供磷能力更为灵敏,可望成为好的土壤磷诊断指标。  相似文献   

2.
长期不同施肥红壤磷素特征和流失风险研究   总被引：13，自引：2，他引：11  
为探索长期施肥对红壤磷素吸附固持的影响,分析不同施肥土壤磷流失风险及影响因素。在南方丘陵区红壤上开展了持续25年的长期定位试验,处理包括:不施肥(CK)、施氮肥(N)、施磷肥(P)、施钾肥(K)、施氮磷钾肥(NPK1)、施2倍量氮磷钾肥(NPK2)、单施有机肥(OM)和氮磷钾配施有机肥(MNPK)。研究了不同施肥下土壤全磷、Olsen-P、Mehlich1-P、CaCl2-P含量及磷吸持指数(PSI)、磷饱和度(DPS)的变化,探讨不同施肥处理土壤对磷的吸附和解吸特征,并分析了土壤磷指标与土壤有机碳、pH、CEC之间的关系。结果表明:长期施用化学磷肥有利于补充土壤磷素,特别是土壤全磷,并使Olesn-P和Mehlich 1-P有增加趋势,而对CaCl2-P影响不显著;施用化肥对DPS影响不显著,单施磷会降低PSI,低量氮磷钾提高了PSI,高量氮磷钾处理与对照差异不显著;长期施用有机肥(猪粪)土壤全磷增加,而Olsen-P、Mehlich 1-P和CaCl2-P则大幅累积, PSI显著降低, DPS显著增加。长期施用化肥处理土壤对新添加磷的吸附较强,长期施用有机肥降低了土壤对新添加磷的吸附;土壤全磷、Olsen-P、Mehlich1-P、CaCl2-P、PSI、DPS及最大吸附容量(Qm)与土壤pH、CEC、土壤总有机碳(TSOC)、土壤水溶性有机碳[冷水提取水溶性有机碳(CWSOC)和热水提取水溶性有机碳(HWSOC)]间相关性较高;土壤磷指标和土壤有机碳、pH、CEC指标之间存在典型相关关系,第1对和第2对典型变量的典型相关系数分别为0.997和0.951,达显著水平。研究表明,施用有机肥是调节土壤磷的供给和保持的重要措施,土壤水溶性有机碳和pH可能是反映红壤磷素供应和流失的关键指标。  相似文献   

3.
Abstract

Phosphate (P) sorption isotherms have been widely used to characterize the P status and to establish fertilizer requirements of soils. Recently, mechanistic models have successfully described the nutrient uptake by plants under changing soil and plant parameters. Phosphorus sorption characteristics of eleven representative soils of the Appalachian Region of the United States were evaluated, and experimental P adsorption data were fitted to Temkin, Freundlich, and Langmuir equations to determine the relative importance of the soil parameters in P retention and supply to plant roots. The Barber and Cushman model was used to predict the effect of P fertilization on P uptake by plant. The soils of Appalachia differ considerably with respect to the retention of added P. All three isotherm equations gave good fit with the experimental data and were reliable to describe the P quantity/ intensity relationships of these soils. The following sequence of P adsorption capacity in various soils was established: Tate (BA)? Hayesville (Bt) > Westmoreland (Bt2) ～ Upshur (Btl) ～ Gilpin (A) > Lily (A) ～ Dandridge (E) ～ Watauga (Ap) > Ashe (A) ～ Berks (A) ～ Dekalb (A). In spite of the great differences among soil properties related to surface area and degree of weathering of these soils, the content of free iron (Fe) oxides was the only soil property that correlated with the constants of the isotherm equations. Amounts of P required to give 0.20 μg P/mL varied with soils and were closely related to the constants of the isotherm equations. Soil P parameters from the P adsorption isotherms were used to determine a measure of Cli, b, and De instead of those used conventionally in the Barber and Cushman (1981) model to predict P uptake by corn. Predicted P uptake by corn varied with soils, even at the same P concentration in equilibrium solution (0.20 μg P/mL) or when an equal amount (90 μg P/mL) of P was added to all soils. Predictions of P uptake, however, were not correlated with the amount of P required to give 0.20 μg P/mL in 0.01M CaCl2 solution or with the constants of the isotherm equations used. Diffusion coefficient and equilibrium P concentration in solution, and two intensity factors, were more important than buffer power in predicting P supplied to roots. These findings may help to explain the lack of significant correlations between the constants of the P isotherm equations and P uptake.  相似文献   

4.
Abstract

Investigating the relation between concentration or release of phosphorus (P) into soil solution (CaCl2‐P, determined by 0.01 M CaCl2 extraction of soils) and soil test phosphorus (Olsen P, or 0.5 N NaHCO3‐extractable soil phosphorus) for 10 widely ranging and variously managed soils from central Italy, a change point was evident where the slopes of two linear relationships meet. In other words, it was possible to distinguish two sections of the plots of CaCl2‐P against Olsen P, for which increases of CaCl2‐P per unit of soil test P increase were significantly (p<0.05) greater above than below these change points. Values of change point ranged from 14.8 to 253.1 mg kg?1 Olsen P and were very closely correlated (p<0.001) to phosphorus sorption capacity of soils. Similar change points were also previously observed when Olsen P (and also Mehlich 3 P) of surface soils was related to the P concentration of surface runoff and subsurface drainage. Because insufficient data are available relating P in surface soils and amount of P loss by overland, subsurface, or drainage flow, using the CaCl2 extraction of soil can be convenient to determine a change point in soil test P, which may be used in support of agricultural and environmental P management.  相似文献   

5.
Sorption of phosphorus (P) in complete soil profiles in northern Europe is not adequately documented. I measured the sorption in genetic horizons of four cultivated soils (Inceptisols, Spodosol) in Finland using both field‐moist and air‐dried soil samples, fitted modified Freundlich equations (Q = a × Ib ? q) to the data, and presented the results in quantity/intensity (Q/I) graphs. Least‐squares‐estimates for the parameters of the modified Freundlich equation (a, b, q) were found to be imprecise measures of sorption. Values derived from the fitted equations (the amount of P sorbed at the P concentration of 2 mg litre?1 and P buffering capacity at the same concentration) were more precise. Both were correlated with concentrations of oxalate‐extractable iron and aluminium. In all soils, there was a distinct difference in sorption between the fertilized Ap horizons and the subsurface horizons, which retained P strongly. Most of the sorption capacity was located in the B horizons at depths between 0.3 and 0.7 m. The results demonstrate the effects of soil‐forming processes and human impact on the sorption of P in the soils. Drying the samples prior to the sorption experiments altered the shape of the Q/I graphs. It increased dissolution of P at small P concentrations, sorption at large P concentrations, and the estimates for P buffering capacity. The effects of drying soil samples on the results and the imprecision of the parameters estimated with the modified Freundlich equation should be taken into account when interpreting results of Q/I experiments.  相似文献   

6.
The effect of previous P additions on commonly used sorption parameters was studied using four alkaline-calcareous soils of Greece, two Vertisols and two Entisols. Solution concentration and buffering capacity indices were significantly affected while sorption curves of the quantity of P removed from the solution (x/m) against final P solution concentration (c) were shifted to the right, towards the higher c concentration values. Different buffering indices (e.g. the slope of the Freundlich equation, the slope of the semi-logarithmic sorption curve of x/m against log c, the slope of the linear portion of the high c concentration range) showed an increasing trend with increasing previous P additions to the soils, with the exception of the slope of the tangent of the Freundlich equation at c = 1 μg P/ml. However, correction for the quantity of exchangeable P already present in the soil (q), resulted in an increasing trend for this parameter as well, while obviously it did not have any effect on the slopes of the linear portions of the sorption curves. Chemical changes, as for example the slow formation of insoluble Ca–P salts, could possibly explain the increased capacity of previously fertilized alkaline-calcareous soils to remove P from the experimental equilibration solution suggested by the increasing trend in the buffering indices of the present work. At any case, this effect should be taken into account, especially in studies where sorption parameters are related to various soil-plant characteristics with respect to P.  相似文献   

7.
Phosphate (PO4-P) sorption characteristics of soils and bedrock composition were determined in catchments of two mountain lakes, Ple?né Lake (PL) and ?ertovo Lake (CT), situated in the Bohemian Forest (Czech Republic). The aim was to explain higher terrestrial P export to mesotrophic PL compared to oligotrophic CT. Concentrations of Al and Fe oxides were the dominant parameters affecting soil ability to adsorb PO4-P. Depending on concentrations of Al and Fe oxides, P sorption maxima varied from 9.7 to 70.5 mmol kg?1 and from 7.4 to 121 mmol kg?1 in organic and mineral soil horizons, respectively. The catchment weighted mean PO4-P sorption capacity was 3.4 mol m?2 and 11.9 mol m?2 in the PL and CT soils, respectively. The higher PO4-P sorption capacity in the CT catchment was predominantly associated with higher pools of soil and Fe oxides. The CT bedrock (mica schist) released one order of magnitude less P than the PL bedrock (granite) within a pH range of catchment soils (pHCaCl2 of 2.5–4.5). The higher ability of PL bedrock to release P and the lower ability of PL soils to adsorb PO4-P thus contributed to the higher terrestrial P loading of this lake.  相似文献   

8.
It is desirable to know the distribution of phosphorus (P) fractions in soil so that plants may use P efficiently. Here we report the dynamics of inorganic and organic P in P-deficient black and rice soil cropped by soybean, white lupin, and maize supplied with nitrogen (N) inputs by N fixation and urea fertilizer. Inorganic P fractions of the three cropped soils could be ranked as O-P (organic phosphorus) > Al-P (aluminum phosphorus) > Fe-P (iron phosphorus) > Ca10-P (calcium-10 phosphorus) > Ca8-P (calcium-8 phosphorus) > Ca2-P (calcium-2 phosphorus), irrespective of soil type. The potential of various inorganic P fractions to plant nutrition differed between soybean and white lupin. The percentage of total P present as inorganic P was affected by crop, soil type, and N source. In black soil, the change of organic P fraction induced by N fixation was larger than by urea application. The moderately labile organic P (MLOP) concentration was not affected significantly by soil type and crop species, and it was probably the main P source to the inorganic P fraction because the correlation between the two pools was high (r = 0.945; P < 0.05). Crop species differed in their uptake of inorganic and organic P from soil. Though P fraction concentrations varied between black soil and rice soil, their response to crop species and N source was similar. The amounts of P removed from soil were affected by N source. The right choice of crop species and the application a suitable N source may increase crop yield and P uptake by plant in P-deficient soils.  相似文献   

9.
Plant-available phosphorus (P) and P adsorption capacities are important for crop growth in acidic soils. Olsen P test, which is based on extraction with bicarbonate for predicting the amount of soil P available to plants, was used in this work. Soil P-adsorption capacities were determined by Langmuir line equation. The purpose of this work was to examine the suitability of Olsen P for predicting phytoavailable P and P sorption parameters in acid soil. To this end, we (i) assessed the phytoavailable P by successively pot-cropping rice and (ii) P adsorption characteristics of soil and their relation with Olsen P. Plant-available P, estimated by Olsen P in tested soil, was correlated to labile P. Qm (phosphorus sorption maximum) was negatively correlated with K (P sorption strength). P buffering capacity of soils was P3 (the highest P rate) >P2 (the second highest P rate) >P1 (the lowest P rate) >P0 (no P adding) after 75 day’s rice growth, which indicated P replenishment capacity was different among P treatments. This also suggested that P of plant uptake may decrease soil buffering capacity, especially for soils that contained relatively lower amounts of P. Qm and K were not significantly correlated to Olsen P. Degree of P saturation and Olsen P shared the similar trend with the change of P application rates and sampling dates. We concluded P status in soil can be characterized by degree of P saturation and Olsen P in tested soil. They were able to explain P status from both agronomic and environmental aspects.

Abbreviations: Qm, P sorption maximum; K, P sorption strength; P3, highest P rate in soil; P2, second highest P rate in soil; P1, lowest P rate in soil; P0, P adding in soil.  相似文献   


10.
上海土壤磷的吸附特性及缓冲性能的研究   总被引：8，自引：0，他引：8  
本文以上海土壤为对象,研究选定了土壤磷等温吸附试验条件为:水土比10,平衡时间6天,控温25℃,磷加入量为100,200,400,600μgP/g土,溶液基质为0.01M CaCl2。磷缓冲能力试验条件为:平衡时间2天,磷加入量为20,40,100,200μgP/g土。根据Freundlich, Tempkin和Langmuir方程计算的土壤吸附指标与土壤类型及土壤性质有密切关系,是土壤磷素肥力的重要指标。反映土壤缓冲能力的“磷肥指标”与土壤有机质、粘粒、活性铝及pH值相关较好。上海几种主要土壤中以青紫泥的最大吸附量(Xm),0.2ppm P吸附量和“磷肥指标”为最高,其次为青黄土,沟干泥和黄泥头,最小为夹沙泥。应用磷吸附指标与“磷肥指标”来预测土壤需磷量,初步试验是可行的,但实际应用还需进一步试验研究。  相似文献   

11.
在黄土旱塬区长期试验(1985-1997年)中,选取对照(不施肥,CK)、磷肥(P2O5.60.kg/hm2,P)、氮肥(N.120kg／hm2,N)、氮磷(N,120.kg／hm2,P2O5,60.kg/hm2,NP)、氮磷有机肥(N.120.kg/hm2,P2O560.kg/hm2,有机肥75.t／hm2,NPM),种植方式为冬小麦连作的5种有代表性的施肥处理,研究了石灰性土壤磷素吸附特性的演变及其与土壤磷素形态、土壤有机碳(SOC)含量的关系。结果表明,P素的最大吸附量(Qm),1997年对照(CK)、N处理比1985年分别提高了18％和14％;而P、NP和NPM处理分别降低了26％、13％和24％。吸附能常数(k值)随时间延长,对照和N处理相对稳定,P和NP处理呈升高趋势,而NPM处理有降低趋势。土壤磷素吸附饱和度(DPS)和零净吸附磷浓度(EPC0)对照和N处理随时间延长呈降低趋势,P、NP和NPM处理呈升高趋势。Qm与Ca8-P、Al-P存在极显著相关关系(P0.001),与Ca2-P、Pe-P存在显著相关关系(P0.05)。Ca2-P、有机磷含量变化与土壤DPS的相关性达到显著水平(P0.05)。EPC0只与有机磷间存在显著的相关关系(P0.05)。Qm、DPS和EPC0变化与SOC存在显著或极显著的线性相关关系(P0.001)。  相似文献   

12.
长期轮作与施肥对农田土壤磷素形态和吸持特性的影响   总被引：10，自引：0，他引：10  
通过对黄土旱塬地区长期定位施肥(26a)条件下的不同轮作系统的土壤磷素形态和吸持参数的测定,研究了轮作和施肥对土壤磷素吸持特性和磷素形态的影响,以及土壤磷素吸持参数与磷素形态之间的关系。结果表明,长期轮作与施肥都可以减低土壤磷素的最大吸附量（Qm）,相对于其它轮作和连作,在氮磷（NP）施肥下,小麦-玉米-豌豆轮作可以减低土壤的Qm,在氮磷有机肥（NPM）施肥下,小麦-玉米轮作可以减低土壤的Qm。在施肥相同的条件下,小麦-玉米轮作和小麦-豌豆轮作可以显著增加土壤中各形态无机磷的含量,长期轮作比连作可以增加土壤中的有效磷养分,尤其对Ca2-P的提高效果更为显著。相关分析表明,Qm和磷吸持指数（PSI）与全磷（T-P）、Olsen-P、CaCl2-P、Ca2-P、Ca8-P、Fe-P、Ca10-P和有机磷呈极显著负相关（p＜0.01）,与闭蓄态磷（O-P）呈显著负相关（p＜0.05）,与Al-P关系不显著。土壤有机质（SOM）与Qm、PSI和磷最大缓冲能力（MBC）之间存在极显著负相关关系,与磷吸持饱和度（DPSS）存在显著正相关。通径系数和逐步回归分析表明,在石灰性黑垆土土壤的无机磷形态中,Ca2-P对Olsen-P的贡献最大。  相似文献   

13.
Abstract. Recent work has demonstrated that the Olsen test for phosphorus (P) is an unreliable predictor of plant-available P in soils derived from basalt parent material in Northern Ireland. The present study was conducted to develop a more reliable soil-P test for these soils by regressing P fractions removed from soil by various chemical extractants against herbage P indices calculated from plant tissue test data using a diagnosis and recommendation integrated system. The degree of P saturation of the soil P sorption capacity, based on ammonium oxalate extractable P, Al and Fe, provided a better prediction of P available to swards on basaltic soils than either the Olsen test or a number of other well-known soil-P test procedures. The superiority of the degree of P saturation test on basaltic soils was attributed to the fact that it simultaneously takes account of both P quantity and P buffering capacity factors in predicting P availability. The Olsen-P test, which accounts for the P quantity factor alone, was only reliable for non-basaltic soils. Re-classifying the P fertility status of basaltic soils according to the degree of P saturation test could result in considerably less P being recommended for these soils with possible consequential benefits to water quality.  相似文献   

14.
【目的】 研究土壤无机磷和有机磷组分变化,有助于选择和优化特定作物体系下不同肥料管理措施,提高磷资源效率。 【方法】 基于20年土冬小麦/夏休闲体系长期肥料定位试验,利用Tiessen-Moir磷素分级法,测定土壤无机磷和有机磷组分,并分析其与小麦磷吸收量、土壤磷表现平衡之间的关系。试验设7个处理:不施肥 (CK)、单施化学氮肥 (N)、氮钾化肥配施 (NK)、磷钾化肥配施 (PK)、氮磷化肥配施 (NP)、氮磷钾化肥配施 (NPK) 和氮磷钾化肥配施有机肥 (MNPK)。 【结果】 旱作条件下,20年长期NP、NPK和MNPK处理较CK、N、NK、PK处理显著提高了小麦籽粒产量,年平均增产在205～265 kg/hm2之间,以MNPK增幅最高。NP、NPK和MNPK处理较CK处理显著提高了小麦籽粒和秸秆吸磷量。PK、NP、NPK、MNPK处理较CK处理显著提高了树脂磷 (Resin-P)、碳酸氢钠提取无机磷 (NaHCO3-Pi)、氢氧化钠提取无机磷 (NaOH-Pi)、浓盐酸提取无机磷 (C.HCl-Pi) 和残余磷 (Residual-P) 含量,显著降低了碳酸氢钠提取有机磷 (NaHCO3-Po) 和氢氧化钠提取有机磷 (NaOH-Po) 含量。PK、NP、NPK与CK相比,对稀盐酸提取无机磷 (D.HCl-Pi)、浓盐酸提取有机磷 (C. HCl-Po) 含量影响不大,而MNPK显著提高了D. HCl-Pi和C. HCl-Po含量。N、NK处理较CK显著增加了Residual-P和C. HCl-Po,显著降低了NaHCO3-Po和NaOH-Po,对Resin-P、NaHCO3-Pi、NaOH-Pi、C.HCl-Pi和D.HCl-Pi含量没有影响。与试验初始时相比,长期施用化学磷肥和有机肥主要增加了土壤中可利用态无机磷的比例,降低了残余态磷和有机磷的比例。土壤中Resin-P、NaHCO3-Pi和C. HCl-Pi与小麦磷吸收量之间呈显著正相关关系。磷素盈余显著增加了D. HCl-Pi、Resin-P和NaHCO3-Pi的含量。 【结论】 供试土壤条件下,NP、NPK和MNPK三种平衡施肥措施都不仅有利于作物增产,而且有利于保持高比例的土壤有效磷库。   相似文献   

15.
Abstract

In nineteen surface horizons of red Mediterranean soils from various locations of Greece, phosphorus (P) sorption experiments were conducted and the sorption characteristics were studied in relation to soil properties. Phosphate sorption data were fitted both to the Langmuir and Freundlich equations. From these equations, the following P sorption parameters were determined from the Freundlich equation, X = ACn, the parameters A (the phosphate sorbed at C = 1 mg P/L), n (the P sorption intensity), the P sorption index (PS = X/log C) and maximum P sorption (Xmfr). From the Langmuir equation, C/X = 1/KXm + C/Xm, the parameters K (showing the bonding energy), maximum P sorption (Xmla), the quantity of P adsorbed at a standard concentration of 0.2 mg P/L (P0.2), and P maximum buffering capacity (PMBC). The Freundlich parameter A was strongly correlated to the clay and sesquioxides ("free”; iron and aluminum oxides and amorphous iron oxides) content. Seventy‐four percent of the variance of this parameter was explained by clay and “free”; iron (Fe) content. The Freundlich parameter n was significantly correlated with pH and amorphous iron oxides content, while 52% of its variance was explained by amorphous Fe and dithionite extrac‐table aluminum (Al). The P sorption maxima calculated from the Freundlich equation were in general lower than those calculated by the Langmuir equation. Both these parameters were strongly correlated with clay and more slightly with sesquioxides content. About 50% of their variance was explained by clay content of the soils. The P sorption index was strongly correlated with the clay content and less strongly with dithionite‐extractable Fe and Al. The P‐buffering capacity calculated from the data of Langmuir equation was also strongly correlated with these two parameters. In addition, clay content and dithionite‐extractable Fe and Al were well correlated to the amounts of P required to obtain an equilibrium concentration of 0.2 mg P/L while 61% of the variation of this parameter was explained by the clay and the dithionite‐extractable Fe content. From these findings, it seems that for the red Mediterranean soils from Greece, P sorption is affected by clay content and iron and aluminum oxide contents.  相似文献   

16.
Crop response to the phosphorus (P) application is often erratic in most soil types in the world. In Algeria, there is no information on the P behavior in calcareous soils. The purposes of this work were to investigate the degree of P fixing capacity and to predict P fertilizer requirements of crops according to calcareous levels in the soil. Soil samples (at 0–30 cm depth) were collected and spiked with 0, 25 and 50% of lime (CaCO3). Phosphate sorption curves were well fitted to the Freundlich equation. Results indicated that the calcareous level was predominantly controlled the P sorption indices [sorption capacity (a), and P sorption energy (n)] to affect the estimation of external d P requirement (EPR0.2) and P fertilizer rates. The understanding of P sorption and desorption by soils and extrapolating the developed relationship between soil calcareous contents and P fertilizer rates would be quite promising and accurate approach for the economic and effective use of P fertilizers in calcareous soils of Algeria.  相似文献   

17.
Abstract

The methods used to predict phosphorus (P) fertilizer requirements use extractable P levels. The inclusion of soil P buffer capacity with extractable P levels to improve fertilizer P prediction accuracy should be further investigated for Mediterranean soils. The objectives of this study, were to characterize the P adsorption properties of selected soils and to compare different soil P buffering capacity indices to determine their contribution to predict P fertilizer requirement. Twenty‐one soils were collected and P adsorption isotherms determined. On 11 soils wheat was grown in the greenhouse and P requirement determined. The Langmuir adsorption isotherm described the P adsorption of all soils. The prediction of crop P requirement was improved by the inclusion of a soil P buffer capacity index in the prediction equation. The index proposed by Salmon is easy to determine under routine soil analyses and does not require special analytical equipment. However, clay content can be used to predict the Salmon buffer index for similar soils.  相似文献   

18.
Abstract

Knowledge of the change in soil extractable phosphorus (P) as a consequence of soil P fertilization could be useful in discriminating soils with a potential for soil P release to runoff or movement of P along the soil profile. In this research, soils with low to medium P retention capacity were equilibrated for 90 days with soluble P (KH2PO4) at rate of 100 mg P kg‐1 soil. After this period, soil samples both with and without the P addition were analyzed using six conventional methods: 1) Olsen, 2) Bray 1,3) Mehlich3,4) Egner, 5) Houba, dilute CaCl2 solution, and 6) distilled water, and three “innovative”; P‐sink methodologies: 1) Fe oxide‐coated paper strip, 2) anion exchange resin membrane, and 3) cation‐anion exchange resin membrane. The soils without P addition had low levels of extracted P as determined by all nine procedures. Net increases in the amount of P extracted from the soils with added P ranged from 4.2 mg kg‐1 (CaCl2 extraction) to 57.6 mg kg‐1 (cation‐anion resin membrane extraction). Relationships between change in extracted P and i) physical and chemical characteristics, and ii) soil P sorption properties are also presented and discussed.  相似文献   

19.
不同磷源对设施菜田土壤速效磷及其淋溶阈值的影响   总被引：2，自引：0，他引：2  
土壤中磷的移动性不仅取决于磷的数量且与磷肥形态有关。了解不同磷源（有机肥和化肥）对设施菜田土壤磷素的影响对于指导科学施肥和面源污染防治至关重要。本文选取河北省饶阳县3种不同磷含量的农田土壤（未种植过蔬菜的土壤、种植蔬菜30年的塑料大棚土壤和种植蔬菜4年的日光温室土壤）为研究对象,采用室内培养试验和数学模型模拟方法研究有机无机磷源对设施菜田土壤磷素的影响,确定无机肥和有机肥源土壤磷素淋溶的环境阈值。结果表明添加有机肥和无机磷肥都会显著增加3种不同种植年限设施菜田土壤速效磷（Olsen-P）和氯化钙磷（CaCl2-P）含量,但增加速度不同。对于未种植过蔬菜的低磷对照土壤,磷投入量高于50 mg·kg-1（干土）后,无机肥比有机肥显著提高了土壤Olsen-P含量。对于已种植蔬菜30年的塑料大棚土壤,高磷投入时[300 mg·kg-1（干土）和600 mg·kg-1（干土）],无机肥比有机肥显著提高了土壤Olsen-P含量,低于此磷投入量时有机肥和无机肥处理之间没有显著差异。3种不同农田土壤CaCl2-P的含量所有处理均表现出无机肥显著高于有机肥处理,尤其是在高磷量[>300 mg·kg-1（干土）]投入时表现更加明显。两段式线性模拟结果表明,设施菜田土壤有机肥源磷素和无机肥源磷素淋溶阈值分别为87.8 mg·kg-1和198.7 mg·kg-1。随着土壤Olsen-P的增加,添加无机肥源磷对设施菜田土壤CaCl2-P含量的增加速率是有机肥源磷的两倍。因此,建议在河北省高磷设施菜田应减少无机磷肥的投入,特别是土壤速效磷高于198.7 mg·kg-1的设施菜田应禁止使用化学磷肥和有机肥,在土壤速效磷低于198.7 mg·kg-1的设施菜田应加大有机肥适度替代无机肥技术的推广。  相似文献   

20.
Geochemical sorption and biological demand control phosphorus (P) retention and availability in soils. Sorption and the biota predominantly utilize the same inorganic form of P, from the same soil pool, on the same time scale, and thus are likely to compete for P as it flows through the available pool. In tropical soils, P availability is typically quite low and soil geochemical reactivity can be quite high. We tested whether greater P sorption strength in tropical soils resulted in lower biological uptake of available P. Since the strength of soil sorption and biological demand for P change as ecosystems develop and soils age, we used soils from the two upper horizons from three sites along a 4.1 million-year-old tropical forest chronosequence in the Hawaiian archipelago. We evaluated the strength of geochemical sorption, microbial demand, and the partitioning of added available P into biological versus geochemical soil pools over 48 h using a 32PO4 tracer. Soil sorption strength was high and correlated with soil mineral content. The amount of added phosphate geochemically sorbed versus immobilized by microbes varied more between the organic and mineral soil horizons than among soil ages. Microbial activity was a good predictor of how much available P was partitioned into biological versus geochemical pools across all soils, while sorption capacity was not. This suggests that microbial demand was the predominant control over partitioning of available P despite changes in soil sorption strength.  相似文献   

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