Phosphorus-Sorption Characteristics and Phosphorus Buffer Coefficients of Some Important Soils in Lao PDR

An estimated 97 percent of the soils in Laos are characterized by low phosphorus (P). This characteristic, together with high acidity, constrains food crop production. The P status, sorption, and associated properties were evaluated for fifteen important agricultural soils from the uplands. Soil pH values ranged from 4.5 to 5.9. Soil organic carbon (C) varied from 7.0 to 22.9 g kg^?1. Soil clay varied from 179 to 709 g kg^?1. The cation exchange capacity (CEC) also varied from 4.30 to 32.1 cmol_c kg^?1. Extractable P levels of thirteen of the fifteen soils were P deficient with medium to very high P sorption, indicating substantial fertilizer P requirements. Dithionite and oxalate aluminum and iron predicted P sorbed at 0.2 mg P L^?1. The extractable P increase per unit added P, P buffer coefficient (PBC), was low, also indicating high P sorption. Field studies are needed to confirm predictions of P requirements.     

Assessing the Feasibility of Olsen P and P Sorption Parameters in Acidic Soils

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.     

Phosphorus fractions of soils under <Emphasis Type="Italic">Lotus corniculatus</Emphasis> as affected by different phosphorus fertilizers

The objective of this work was to assess the changes of soil P fractions by Lotus corniculatus and to determine contribution of each fraction to plant P nutrition. Phosphorus was added at a rate of 240 mg/pot as triple superphosphate (20% P), phosphate rock (13% P), or poultry litter (2% P) to a Vertisol or an Inceptisol; a control treatment (without P fertilizer) was also included. Then, L. corniculatus was sowed and harvested eight times; both yields and P content of plant were determined at each harvest. Soil P fractions were determined by Hedley’s modified method. The content of labile and moderately labile P [anionic exchange membrane-Pi (AEM-Pi), NaHCO₃-Pi, and NaOH-Pi] fractions were markedly reduced and were probably due to P uptake by plants. The content of the HCl-Pi fraction of the phosphate-rock-treated soil decreased whereas that of the residual P fraction was not modified. The content of organic forms increased in all treatments. The content of both labile organic P and moderately labile organic P were positively and significantly correlated with the P concentration of roots and with roots biomass, suggesting that the increase in these two organic fractions was related to root production. AEM-Pi accounted for 95% and 84% of absorbed P in Vertisol and Inceptisol, respectively.     

长期施肥红壤性水稻土磷素演变特征及对磷盈亏的响应

研究双季稻种植制度下长期不同施肥红壤性水稻土磷素含量及磷素有效性演变特征及其对土壤磷盈亏(磷平衡)的响应,为南方双季稻区红壤性水稻土科学施磷提供依据。以35年长期肥料定位试验为平台,研究不同施肥处理土壤全磷、有效磷及磷活化系数(PAC)的演变规律,计算不同处理土壤-作物系统每年磷素盈亏量及累积磷素盈亏量,探讨土壤全磷、有效磷及PAC与累积磷盈亏量的响应关系。结果表明,不施磷肥的CK和NK处理土壤全磷、有效磷和PAC随试验年限呈持平或下降趋势;不施磷肥仅施猪粪的NK+PM处理土壤全磷呈缓慢上升趋势,有效磷和PAC呈下降趋势;施化学磷肥或化学磷肥配施稻草的NP、NPK、NP+RS和NPK+RS处理土壤全磷在试验前10年上升速率较快,之后25年上升速率变缓或随时间变化不显著,土壤有效磷在试验前5年急剧升高,之后随时间变化速率减缓或基本持平。CK、NK和NK+PM处理35年土壤PAC平均值较试验初始值分别下降33.2%、29.7%和16.6%,NP、NPK、NP+RS和NPK+RS土壤PAC较初始值分别提高66.2%、60.6%、65.6%和52.9%。不施磷肥导致红壤性水稻土磷素亏缺,不施化学磷肥仅施猪粪土壤磷素基本持平,施用化肥磷及化肥磷配施稻草土壤磷素盈余。土壤全磷、有效磷及PAC与土壤磷累积盈亏量均呈极显著正相关关系,土壤每盈余磷100 kg hm-2,全磷含量提高0.03 g kg-1,有效磷提高1.20 mg kg-1,土壤PAC上升0.09%。外源磷投入是影响土壤磷素及磷有效性的重要因素,在本试验条件下,长期不施磷或磷投入不足导致土壤磷亏缺,进而导致土壤磷及磷有效性降低,而化肥磷及有机无机磷配施促进了土壤磷盈余及土壤磷素肥力的提高。     

Changes in recovery of native and applied phosphorus with time as affected by soil properties in some calcareous soils

In an attempt to investigate variations in availability of native and applied phosphorus (P) with time, twenty five calcareous soil samples were treated with 0, 50 and 500 mg P kg^?1 soil and incubated at 80–90% of field capacity moisture content in an open door glasshouse for a period of one year. Soil samples were taken out at certain intervals for P extraction with Olsen extractant under moist condition. Results indicated that following wetting the mean value of native Olsen-P decreased initially and then increased gradually with time of incubation. Generally, the short term (24 h) recoveries were not correlated with long term ones. The recovery of added P with time was described properly by the following new proposed model: R = 100/(1 + kt^b), where R is percent recovery at time t, and k and b are empirical parameters. The values of k constant at 50 and 500 mg P kg^?1 were in the ranges of 0.40 to 1.22 (0.84 ± 0.25, on average) and 0.04 to 0.52 (0.23 ± 0.14, on average), respectively. The corresponding respective values of b constant also ranged from 0.05 to 0.32 (0.15 ± 0.06, on average) and 0.12 to 0.92 (0.46 ± 0.23, on average).     

Hydrolysis rates of inorganic polyphosphates in aqueous solution as well as in soils and effects on P availability

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.     

Yield of alfalfa as influenced by levels of P and K fertilization

Abstract

This study was conducted to ascertain further the need for P and K fertilizers to obtain maximum herbage yields from alfalfa (Medicago sativa L.). Vernal alfalfa was established on a low K Piano silt loam (Typic Argiudoll) soil and topdressed with zero, 22.4, and 44.8 kg/ha of P in autumn of seeding year and with zero, 224, and 672 kg/ha of K as KC1 each autumn. The harvest schedule was three cuts annually at first flower; a schedule widely recommended in the North Lake states. No statistical significance was found for P levels nor for the P x K interaction; significance was found only for K levels. Maximum herbage yield was obtained with 224 kg/ha of K in the first harvest year, but with the 672 kg/ha of K rate in the second harvest year. Herbage K and Cl percentages and amounts removed from the soil increased significantly each year with each increase in K applied. Herbage P and N percentages were decreased significantly with the first increment of K. Residual herbage yields showed dramatically the influence of K fertilization on winter survival. All alfalfa stands with no K fertilization were killed completely. Residual yields and stands increased with each increase in K applied. Yield increase over the control was significant only with the second increment of K, while stands increased significantly with each increase in K applied. These data continue to confirm that high levels of soil K are needed for stand survival as well as for high herbage yields.     

Characteristics of P accumulation and distribution at the maturity stage of Brassica Napus varieties with different phosphorus use efficiency for grain production

Phosphorus (P) is one of nutrients essential for plant growth. The differences in P content, accumulation, and distribution among 98 rapeseed (Brassica napus) varieties with different P use efficiency for grain production (PUEg) were studied. The results showed that there were highly significant differences in P contents of the whole plant and various organs among different rapeseed varieties. Furthermore, PUEg had significantly negative correlations with P accumulations in whole plant, stems, shells, and seeds. The correlation analysis showed that the correlation coefficient of PUEg and P distribution ratio in stems was smaller, and it was significantly negatively correlated in shells, while it showed highly positive correlations in seeds. It indicated that P content in rapeseed plant stems and shells appeared to be transported into seeds to increase P distribution in seedpods at the late maturity stage, which could help improve PUEg.     

Effects of equilibrating salt solutions on phosphate sorption by soils

Abstract

Several equilibrating salt solutions have been used in the studies of P sorption by soils and sediments. This study was conducted to evaluate the effects of 10 salt solutions on estimation of P sorption by soils. Results obtained showed that, when the equilibrating solution was made to contain 0.01M with respect to CaCl₂, Ca(NO₃)₂, CaSO₄, MgCl₂, KCl, LiCl, Nacl, or KHCO₃, the amount of P sorbed by soil always exceeded the amount sorbed from the soil‐water system. In comparison with the amount of P sorbed from water, 0.01M NaHCO₃ reduced P sorption by soils. Use of THAM buffer (0.05M pH 7.0) to control the pH increased P sorption by some soils and decreased P sorption by others, relative to that sorbed from the soil‐water system. The results indicated that inclusion of salts in the equilibrating solution for P‐sorption studies should be avoided, especially in studies related to water quality.     

Effective diffusion coefficient of cations as influenced by physical and chemical properties of selected Indiana soils

Abstract

Ion diffusion through the soil matrix is dependent upon both the physical and chemical properties of the soil. Cation (K, Na, Ca and Mg) diffusion coefficients De, were determined for seven Indiana soils by using the ion diffuison flux to a hydrogen resin paper technique. Volumetric moisture, clay content exchange and solution phase ionic concentrations, buffer capacity and organic C content were variously related to the determined De values. The larger the diffusion coefficient of K, Ca, and Mg, the lower the clay content, and exchange capacity of soils, and the higher the concentration of these cations in the solution phase. From the present study, it was concluded that the De of these cations was affected by one or more soil physical and chemical property which must be considered if De is to be used to estimate supply rate of these ions to growing roots in soil systems.     

长期施磷稻田土壤磷素累积及其潜在环境风险

应用常规化学分析法和数学统计方法,基于太湖地区13年的长期定位试验,研究长期不同施磷水平下[0(不施磷)、30 kg.hm 2.a 1(低磷)、60 kg.hm 2.a 1(适磷)、90 kg.hm 2.a 1(高磷)]稻麦轮作系统稻田土壤磷素累积规律及磷素流失引发的环境风险。在本试验区土壤环境条件下,可能发生稻田磷素淋溶及径流的土壤耕层(0~15 cm)Olsen-P临界值分别为26.0 mg.kg 1和24.8 mg.kg 1。连续13年适磷、高磷施肥,土壤耕层Olsen-P含量分别达到26.9 mg.kg 1和33.2 mg.kg 1,均高于临界值浓度,且已导致稻田田面水与30 cm渗漏水中总磷浓度显著升高,大大提高了稻田磷素淋溶及径流的风险。低磷施肥土壤Olsen-P长期稳定在(10.1±2.0)mg.kg 1水平,并且每年的稻麦产量与高磷、适磷处理相比并无显著差异,而长期低磷施肥土壤磷的流失风险也较小。因此,在太湖地区稻麦轮作体系下,磷肥不宜以常规适磷水平长期施用,建议以低磷水平(30 kg.hm 2.a 1)长期施用或以适磷水平(60 kg.hm 2.a 1)间歇式施用。     

Development of buffer methods and evaluation of pedotransfer functions to estimate pH buffer capacity of highly weathered soils

The pH buffer capacity of a soil (pHBC) determines the amount of lime required to raise the pH of the soil layer from its initial acid condition to an optimal pH for plant growth and the time available under current net acid addition rate (NAAR) until the soil layer acidifies to a critical pH leading to likely production losses. Accurate values of pHBC can also be used to calculate NAAR from observed changes in soil pH. In spite of its importance, there is a critical shortage of pHBC data, likely due to the long period of time needed for its direct measurement. This work aimed to develop quick, simple and reliable methods of pHBC measurement and to test these methods against a slow (7‐day) titration used as benchmark. The method developed here calculates pHBC directly from the pH buffer capacity of the buffer solution and the increase in soil pH and corresponding decrease in pH of the buffer solution following mixing and equilibration. The pHBC values calculated using Adams and Evans or modified Woodruff buffers were in accord with those measured by slow titration. Buffer methods are easily deployed in commercial and research laboratories as well as in the field. The advantage of using buffer solutions to calculate pHBC instead of lime requirement is the broad application of this soil property. The pHBC of a soil is an intrinsic property that would not be expected to need remeasurement over periods of less than decades. Recurring lime requirement can be calculated from the soil's pHBC, initial and target pH values. A large proportion of the variability in pHBC was explained by the soil organic carbon content. This relationship between pHBC and soil organic carbon content allowed us to develop local pedotransfer functions to estimate pHBC for different regions of Australia.     

Study of the Potentially Mineralized Nitrogen Content and Nitrogen Supply by Soil Incubation Method in a Long-Term Field Experiment in East Hungary

The formation and fate of soluble nitrogen (N) forms and their response to organic-matter mineralization is not obvious yet, and results are often inconsistent despite intensive research. The available N supply of the soil is very important for plant nutrition and environmentally sound N fertilization. The determination of actual N supply is very important for sustainable agriculture in Hungary, especially in acidic sandy soils, which are very sensitive to environmental effects and inefficient human treatment. Therefore, the aim of this article is to provide further information about N mineralization processes and organic–mineral interactions of soil. To establish the potentially mineralized N content and available N supply of soil, a biological (incubation) method was carried out an acidic brown forest soil of the Nyírlugos long-term field experiment in Hungary. The incubation was carried out in the laboratory with differently treated soils of the long-term field experiment to investigate the effect of treatments on N mineralization processes of soil. The incubation period was 16 weeks long. The pH and the easily soluble mineralized and organic N fractions of soil were measured periodically from leached solution (0.01 M calcium chloride; CaCl₂). The leaching process was repeated after 2, 3, 5, 7, 9, 12, and 16 weeks. The potentially mineralized N content of soil and the actual rate of N mineralization were calculated from periodically collected data. The results of the incubation method can be summarized as follows: the kinetics of incubation of 0.01 M CaCl₂ soluble organic N is similar to mineral N; 0.01 M CaCl₂–soluble N fractions were mainly in inorganic forms in the incubation period but the content of the organic form was significant too; and the mineralization rate is greater where the microbiological activity of the soil is expressed and the soil properties are more favored as a result of applied treatments.     

Characterization of Soil Phosphorus in Differently Managed Clay Soil by Chemical Extraction Methods and 31P NMR Spectroscopy

Changes in land use alter the natural cycling of phosphorus (P) in soil. Understanding the chemical nature of these changes is important when developing sustainable management practices for cultivated soils. In this study, we evaluated the ability of commonly used laboratory methods to characterize land use–induced changes in various P pools. Also, the characteristics of soil P revealed by different methods are discussed. Soil samples were taken from three differently managed field plots of the same clay soil: uncultivated grassland and organic and conventional crop rotations. Soil P reserves were characterized using Chang and Jackson and Hedley sequential fractionation procedures and by sodium hydroxide (NaOH)–ethylenediaminetetraacetic acid (EDTA) extraction followed by ³¹P NMR spectroscopy. Both of the tested fractionation methods identified differences in the P pools and provided evidence regarding land use–induced changes. However, the ³¹P NMR analysis suggests that the quality of organic P in this soil was not affected by the change in land use.     

天鹅湖潟湖表层沉积物磷的吸附容量及潜在释磷风险

研究了天鹅湖潟湖表层沉积物对磷的吸附容量,分析了沉积物磷吸附指数(PSI)、磷吸附饱和度(DPS)及由这两个指标构成的磷释放风险指数(ERI),预测了不同区域沉积物磷的潜在释放风险。结果表明,沉积物的PSI变化范围为7.44~28.53 mg L/100 gμmol,湖北部和中部沉积物的PSI值较高;DPS与PSI的变化趋势相反,变幅为0.85%~4.99%,表现为湖南部和中部沉积物的DPS高于北部。沉积物的PSI与磷的理论吸附容量(Qmax)呈极显著正相关(P0.01),而DPS与沉积物各理化参数间的相关性较差。有机质(OM)、活性铝(Alox)和粘粒是表层沉积物对磷持留的主要影响因素。此外,天鹅湖潟湖表层沉积物的ERI变化范围为2.93%~44.70%,磷释放诱发富营养化的风险处于中度范围,其中东南部发生富营养化的风险较高     

The Effect of Legume Species Grown as Cover Crops in Olive Orchards on Soil Phosphorus Bioavailability

Some legume species are able to utilize phosphorus (P) from sparingly soluble P sources benefiting companion crops or those following in the rotation. Lupinus albus, Vicia villosa, and a mixture of eleven annual pasture legumes were used in olive orchards as mulched cover crops as a means of increasing the soil P availability. By soil testing and growing bioindicator P plants in the next season, it was possible to detect a slight but consistent increase in soil P availability. The results indicated that the increase in soil P availability was mainly due to the mineralization of the high P content legume residues, rather than the direct effect in the rhizosphere of the living plants. The results also suggested that the good adaptation of white lupine to low P environments might be due to a high internal P use efficiency of this species, producing high dry matter yields with low P concentration in their tissues.     

长期定位施肥对土壤磷素吸持特性与淋失突变点影响的研究

通过对黄土旱塬地区长期(26a)定位施肥条件下的不同施肥处理的土壤磷素及其吸持参数的测定,以及通过室内模拟试验对土壤磷素淋失突变点的测定,研究了土壤磷素吸持参数、土壤磷素淋失突变点和部分土壤性质之间的关系。结果表明,经过26年的长期施肥,M75P60和M75N120P60处理的Olsen-P含量比CK处理的提高了10.7和9.8倍,全磷(T-P)含量比CK处理的提高了60.4%和57.7%。长期磷肥和有机肥投入可以减低土壤磷素的最大吸附量(Qm),而提高土壤磷素的吸附饱和度(DPSS),M75N120P60处理的Qm比CK的减低了49.92%,而DPSS比CK的提高了21.5倍。相关分析表明,黄土旱塬土壤的Qm与Olsen-P、T-P和CaCl2-P呈极显著的负相关关系(P<0.01),与土壤有机质呈显著负相关关系(P<0.05)。零净吸附浓度磷(EPC0)与Olsen-P和CaCl2-P呈极显著正相关关系,与T-P和SOM也达到显著正相关,而与pH值的关系不显著,但土壤磷最大缓冲能力(MBC)与pH值的关系达到极显著。DPSS与Olsen-P、T-P、CaCl2-P和SOM呈极显著正相关关系。土壤磷素淋失的Olsen-P突变点值与土壤吸持参数Qm呈极显著正相关,与MBC也达到显著正相关,与DPSS、Olsen-P、T-P和CaCl2-P呈极显著负相关关系。该地区土壤磷素淋失的Olsen-P突变点值与DPSS15%的值极为吻合,即可以用DPSS15%值作为该地土壤磷素淋失的突变点值。     

Relationship between Soil Phosphorus Availability and Phosphorus Loss Potential in Runoff and Drainage

Abstract

Elevated soil phosphorus (P) content is common in the central coastal valleys of California, the result of decades of the intensive vegetable production. Undesirably high P concentration in surface water in this region stimulated interest in evaluating techniques to rank the potential for soil P loss to the environment. Phosphorus availability of 25 representative soils from fields in vegetable rotations were evaluated by the following techniques: bicarbonate‐extractable P (P_bc)–calcium chloride, extractable P (P_cc), P extractable by iron‐impregnated paper (P_Fe), P extractable by anion exchange resin (P_ae), and the degree of P saturation (P_sat). A column study was conducted in which these soils were evaluated for soluble P concentration in runoff and leachate from two simulated irrigation events. There were strong correlations among all measures of soil P availability (r=0.66–0.90). Runoff soluble P was most strongly correlated with P_cc, P_ae, and P_bc (r=0.98, 0.93, and 0.91, or 0.98, 0.90, and 0.85 in the first and second irrigation, respectively). The relationship of runoff soluble P to P_bc, P_ae, and P_cc was characterized by a change point; runoff soluble P from soils <50 mg kg^?1 P_bc was minimal, whereas at higher P_bc runoff P reached levels of environmental concern. Leachate soluble P was also correlated with P_cc, P_ae, and P_bc (r=0.84–0.99). Across soils, leachate soluble P averaged 1.4 mg L^?1, compared to 0.11 mg L^?1 for runoff P. We conclude that P_cc, P_ae, and P_bc are useful tests to rank the potential for P loss in irrigation runoff or drainage. Given the relative complexity of the P_ae technique, P_bc and P_cc appear to be the most practical soil tests for this purpose.     

施用常规磷水平的80%可实现玉米高产、磷素高效利用和土壤磷平衡

【目的】近年来,黑土有效磷含量呈逐年增加趋势。研究田间条件下,黑土的玉米产量及构成因素、磷素的吸收利用和土壤有效磷含量变化对不同施磷水平的响应,为黑土区的磷肥合理施用和地力培育提供理论依据。【方法】在土壤有效磷初始含量较高（30.15 mg/kg）的吉林公主岭黑土区,进行了3年的田间试验,以不施磷肥为对照（P0）,设置当地磷肥用量的80%（P₂O₅ 60 kg/hm2,P60）和当地施肥量（P₂O₅75 kg/hm2,P75）,研究不同施磷水平对玉米产量及产量性状、磷素吸收分配、磷肥利用效率的影响,并分析了土壤表观磷平衡和有效磷含量的变化。【结果】连续三年（2009~2011年）不同施磷水平下,玉米的产量随施磷水平的提高而增加,到第三年施磷处理的玉米产量显著高于不施磷处理,随施肥年限增加,P60与P75处理的增产效应差距缩小。P75处理吸收的磷素高于P60,但分配到籽粒中的磷素比例逐年下降,说明其吸收的磷素未高效转移到籽粒中,存在磷素奢侈吸收现象。两个施磷处理的磷肥利用率均为P75>P60,磷肥偏生产力均为P60>P75,说明P60处理中土壤基础养分和施入磷肥的综合效应更大。2009~2011年,土壤的表观磷平衡,P0处理一直处于亏缺状态,P60和P75处理均有盈余。P0、P60和P75处理的土壤有效磷的变化量为-15.4、-0.19和3.50 mg/kg。有效磷含量变化与表观磷盈余量呈极显著线性正相关,土壤P盈余每增加100 kg/hm2,有效磷含量增加9.6 mg/kg。【结论】在有效磷含量较高的黑土区,适当减少磷肥用量（60 kg/hm2 P₂O₅,比传统施肥减少20%）能获得与传统施磷相当的产量,维持土壤适宜的有效磷含量和供磷水平,并能保证磷肥的高效利用。可以考虑将P₂O₅ 60 kg/hm2作为黑土区的推荐施磷水平。     

Effect of Manure Types and Period of Incubation on Phosphorus-Sorption Indices of a Weathered Tropical Soil

Application of animal manures with inorganic phosphate (PO₄) fertilizer is proposed as one of the management options to improve availability and solubility of applied phosphate in weathered soil. We studied the effects of poultry, cattle, and goat manures at different incubation periods (0 to 120 days) on phosphorus (P) sorption indices of a weathered sandy clay loam soil. The soil P adsorption isotherms conformed to the H curve. Generally, the soil P-sorption efficiency decreased as the number of days of incubation increased irrespective of manure amendments. Manure application reduced the P-sorption efficiency of the soil; the lowest P-sorption efficiency was observed after 30 days of incubation. The data conformed to adsorption models in the order Temkin > Freundlich > Langmuir. Cattle, goat, and poultry manures reduced the adsorption constants in all models. Standard phosphate requirement and P-buffering capacity were also reduced with the application of the manures.