不同有机废弃物对土壤磷吸附能力及有效性的影响

城郊农地是循环有机废弃物的重要场所,但长期施用畜禽粪和城市污泥可引起土壤磷素积累、磷饱和度提高,增加土壤向环境流失磷的风险。为了解施用不同来源的有机废弃物对城郊耕地土壤磷素化学行为的影响,选择4种不同磷含量的土壤,探讨在等量磷素情况下,施用KH2PO4、猪粪/稻草秸秆堆肥、沼渣、猪粪、鸡粪、生活垃圾堆肥和2种污泥等不同磷源时,土壤有效磷含量及磷吸附能力的差异。结果表明,施用有机废弃物增加了土壤有效磷和水溶性磷含量,降低了土壤对磷的吸附能力,但影响程度因有机废弃物来源而异。施用猪粪/稻草秸秆堆肥和猪粪降低土壤磷最大吸附量比例(9.03%~15.60%)与施KH2PO4(10.59%~16.63%)相当,但施用沼渣、鸡粪和生活垃圾堆肥降低土壤磷最大吸附量的比例(5.09%~9.84%)明显低于施KH2PO4;施用2种污泥降低土壤磷最大吸附量的比例(4.32%~6.77%)最小。不同有机废弃物对土壤有效磷的影响差异较小,但对水溶性磷的影响较大。施用有机废弃物后,土壤磷最大吸附量的下降值与施用有机废弃物中铁、铝、钙含量呈负相关;土壤水溶性磷的变化量与施用有机废弃物后土壤交换性钙的增加量呈负相关,表明有机废弃物中铁、铝和钙等矿质成分的增加,可在一定程度上减少有机废弃物在土壤循环处理时磷对环境的负影响。在农田施用有机废弃物时,不仅要考虑有机废弃物磷素状况,也应适当考虑其他矿质成分的组成特点。该研究可为城郊农地科学施用有机废弃物提供依据。     

黄土高原石灰性土壤不同形态磷组分分布特征

以黄土高原自北向南采集的12个0～20 cm耕层土壤为供试土样,采用Tiessen和Moir修正的Hedley土壤有机无机磷分级方法研究了黄土高原石灰性土壤中不同形态磷组分的分布特征。结果表明:供试土壤各形态P总体分布特征为:HCl-P>Residual-P>NaHCO3-Po>NaHCO3-Pi>NaOH-Po>NaOH-Pi>H2O-P,以HCl-P和Residual-P为主,分别占土壤全磷的54.00%～88.96%和0～39.11%。黄土高原土壤磷含量总体分布表现为南高北低。在各土壤类型间,NaOH-Po、Residual-P和全磷平均含量表现为干润砂质新成土<黄土正常新成土<简育干润均腐土<土垫旱耕人为土,自北向南依次增加;H2O-P和HCl-P表现为简育干润均腐土<黄土正常新成土<干润砂质新成土<土垫旱耕人为土,自北向南先降后升,且上升幅度较大。黄土高原土壤全氮与全磷及各形态磷含量相关性均达显著水平,其中与NaOH-Pi、NaOH-Po、HCl-P及全磷含量达到极显著水平。C/N、pH及砂粒与全磷及各形态磷含量呈负相关关系,其中pH与NaHCO3-Po呈显著负相关,与H2O-P、NaHCO3-Pi、NaOH-Pi及HCl-P呈极显著负相关;砂粒与NaHCO3-Pi、Residual-P及全磷呈显著负相关。除NaHCO3-Po、NaOH-Po及Residual-P,CaCO3与其他各形态磷含量具有一定程度负相关。除NaOH-Pi和NaOH-Po外黏粒与其他各形态磷及全磷也具有一定程度负相关。土壤各形态磷组分和有效磷的多元回归分析发现,各形态磷中对有效磷贡献最大的是H2O-P,其次为NaOH-Pi和NaHCO3-Po;土壤各形态磷组分和有效磷逐步回归分析结果,进一步说明H2O-P的有效性最高。     

Phosphorus-induced zinc deficiency in wheat pot-grown on noncalcareous and calcareous soils of different properties

High levels of phosphorus (P) often induce zinc (Zn) deficiency in plants grown on Zn-poor soils. We investigated P-induced Zn deficiency in durum wheat (Triticum durum L. ‘Carpio’) grown on 16 noncalcareous and 31 calcareous soils differing in levels of available (Olsen) P and available (diethylenetriaminepentaacetic acid (DTPA)-extractable) Zn using micropots. A completely randomized factorial design with two levels of P (0 and 40 mg P kg^?1 soil) and Zn (0 and 3 mg Zn kg^?1 soil), i.e. four treatments (‘control’, + P, + Zn, and + PZn), were used. Grain yield of control plants depended mainly on the Olsen P level. Phosphorus had a negative effect on yield in 6 soils with Olsen P/Zn_DTPA > 25, and Zn a positive one in 5 soils with Olsen P/Zn_DTPA > 50; and the + PZn treatment generally resulted in the highest yield. Grain Zn concentration of control plants was negatively correlated with growth and Olsen P. Calcareous soils were less sensitive to P-induced Zn deficiency than noncalcareous soils because phosphate is sorbed by calcite rather than being co-adsorbed with Zn on the Fe oxides. Co-application of P and Zn to soil at low and application of Zn at high Olsen P ensured both maximum yield and grain Zn bioavailability.     

Chemical fractionation of phosphorus in calcareous soils of Hamedan,western Iran under different land use

We investigated the effects of land uses on P distribution and availability in selected calcareous soils under different management practices. KCl‐P (labile P), NaOH‐P (Fe‐Al‐bound P), HCl‐P (Ca‐bound P), and residual P (Res‐P) fractions at 0–30 cm depth were determined for soils planted to garlic, orchard, pasture, potato, leafy vegetables, and wheat. Trends in P distribution between chemical fractions were similar between land uses. Ca‐bound P was the most abundant P fraction in the soils, constituting between 61% and 78% of the total P, whereas P associated with labile was less abundant (< 2%). Soils under leafy vegetables and wheat along with pasture presented the highest and lowest values in all fractions of P, respectively. Labile P generally was highest for leafy vegetables and potato. Labile P and Fe‐Al‐bound P comprised < 1.4% and 8% of total P, respectively. Residual P ranged from ≈ 14% (potato and garlic) to 31% (pasture). Long‐term fertilization increased P allocation to inorganic fractions, as Ca‐bound P contained 78% of total P for potato and garlic and 74% for leafy vegetables but 61% for pasture. A strong positive correlation between labile P and Fe‐Al‐bound P (r = 0.534, p < 0.01), labile P and Ca‐bound P (r = 0.574, p < 0.01), Ca‐bound P and Fe‐Al‐bound P (r = 0.504, p < 0.01), Olsen‐P and CaCl₂‐P (r = 0.821, p < 0.01) was found. Principal‐component analysis showed that the first four components accounted for most of the variation, 32.5%, 16.9%, 12.9%, and 7.9% of total variation, respectively.     

有机酸根对不同土壤组分无机磷生物有效性的影响

A field investigation was conducted to determine the survival and growth rate of eucalyptus (Eucalyptus camaldulensis Dehn.) and guava (Psidium guajava L.) saplings planted in salt-affected soils. The field used was highly saline-sodic in nature with a wide variation in electrical conductivity of the saturated soil extract (ECe), pHs, sodium adsorption ratio (SAR) and gypsum requirement (GR). A randomized complete block design was utilized with three treatments, i.e. T1=plastic container bags totally removed, T2=only the plastic container bag‘s base removed and T3=plastic container bags un-removed. There were 34 and 8 plants in each block for eucalyptus and guava, correspondingly. The survival rates of eucalyptus and guava saplings were greater than 90%. In addition, gain in eucalyptus height was significantly higher in the T1 treatment where the bags were totally removed while for guava height the treatments were not significant. The gain in girth was not significant for both eucalyptus and guava saplings. With eucalyptus the taproot length was greater than the lateral roots while for guava the lateral roots were longer than the taproots. There was a decrease in the salinity-sodicity of the soils for the upper 30 cm depth under both types of vegetation, indicating that the salts had leached down to the B-horizon.     

低分子量有机酸对红壤无机磷活化的作用

采用室内模拟试验研究了低分子量有机酸,如草酸、柠檬酸、酒石酸和苹果酸在红壤无机磷活化中的作用。结果表明,相同浓度下,有机酸活化土壤磷的能力为柠檬酸酒石酸苹果酸。低浓度(0.5mmolL-1)时,草酸活化能力最小;高浓度(≥5mmolL-1)时,其活化能力最大。对同一种有机酸而言,土壤各无机磷形态活化量均随pH的升高而降低;且在同一酸度下,其活化量以铝磷(Al-P)为最多,铁磷(Fe-P)和钙磷(Ca-P)次之,闭蓄态磷(O-P)则最少。有机酸活化土壤无机磷酸盐应该是质子酸效应和有机酸阴离子络合效应共同作用的结果,且与磷酸盐的溶度积常数密切相关。研究结果对根系土壤无机磷素循环研究有着重要的意义。     

Density separation of soil organic matter across three land uses in calcareous soils of Iran

ABSTRACT

The aim of this study was to examine the usefulness of physical and chemical fractionation in quantifying soil organic matter (SOM) in different stabilized fraction pools. Soil samples from three land use types in Lorestan province, Southwest Iran were examined to account for the amount of organic carbon and nitrogen in different SOM fractions. Size/density separation and chemical oxidation methods were applied to separate the SOM fractions including particulate organic matter (POM), Si + C (silt and clay), DOC (dissolved organic C), rSOM (oxidation-resistant organic carbon and nitrogen) and S + SA (sand and stable aggregates). The values obtained for TOC, TN, and HWC were highest in forest lands followed by the range and agricultural lands. Among the SOM fractions, S + SA showed the highest values (5.75, 5.77 and 20.6 g kg^?1 for agriculture, range and forest lands respectively) followed by POM, Si + C, rSOM, and DOC. The concentrations of C and N in the labile fractions obtained the higher values than in the stabilized fractions. Forest lands had the highest amounts of organic C and N among all fractions whereas agricultural lands showed highest values for inorganic C content of soils in different fractions.     

Water dispersible clay in calcareous soils of southwestern Spain

Water dispersible clay (WDC) is a good indicator of the risk of soil erosion by water and the consequent losses of nutrients and contaminants in overland flow. We measured the content and studied the properties of WDC in 26 samples of calcareous Xeralfs, Xerepts and Xererts of southwestern Spain collected from fields under different crop and tillage management; the soils ranged widely in total clay content (60–455 g kg^− 1), calcium carbonate equivalent (CCE) (< 1–559 g kg^− 1) and active calcium carbonate equivalent (ACCE; 2–135 g kg^− 1), and were poor in organic carbon and soluble salts. The WDC content was determined by shaking 10 g of soil in 1 L of simulated rainwater for 4 hours. Non-carbonate WDC contents were found to be strongly correlated with the total clay content of the soils and ranged from 1 to 92 g kg^− 1 soil (mean = 29 g kg^− 1), the non-carbonate WDC/total clay ratio ranging from 0.01 to 0.29 (mean = 0.12). Based on regression analyses, illite was more dispersible than smectite and iron oxides decreased dispersion of clay. Carbonate WDC contents ranged from 1 to 27 g kg^− 1 (mean = 8 g kg^− 1) and were averaged one third the non-carbonate WDC contents; also, they were strongly correlated with the soil ACCE. WDC was rich in phosphorus (P) relative to the bulk soil. The enrichment ratio (ER) for total P (i.e. the ratio of total P in WDC to total P in soil) ranged from 0.2 to 29 (mean = 5) and was inversely related to the total clay content. On average, about one tenth of the soil total P was exported in the WDC and about one fifth of the total P in WDC was in the form of bicarbonate-extractable P (i.e. relatively soluble or ‘labile’ P). Part of the P in WDC seemingly occurred as metal phosphate particles formed by reaction of P fertilizers with soil. In summary, significant amounts of P can be exported via WDC, even though the proportion of total clay that is water dispersible is substantially lower in these soils than in cultivated soils of other semiarid regions.     

氧化土和老成土中自然产生的有机酸对磷的活化

Citric and malic acids at concentrations of 0.1,1.0,10,and 100 mmol/L were added to three Ultisols and one Oxisol,The amount of P in solution increased with increasing organic acid concentrations,while the amount of Fe-and Al-bound P decreased.This result suggested that naturally occurring products of organicmatter decomposition could increase the P availability to plants in soils where there is a relatively large pool of Fe-and Al-bound P.The interactions between citric and malic acids at the above concentrations,and p added at rates of 10,20,40,and 80mg/kg were determined.At zero levels of organic acids,all added P became either labile or bound ,and greater proportions remained soluble as the concentration of orgaic acids increased,which suggested that organic acids reduced fixation of dissolved P in Fe-and AL-rich soils .Agricultural practices which increase organic matter input on P-deficient acid soild could decrease P deficiency,This would be important in many tropical and subtropical regions where these soils are common,and where the costs of fertilizers and lime are relatively high.     

Effects of low-molecular-mass organic acids on P nutrition and some plant properties of Hordeum vulgare

One of the strategies of the plants growing in phosphorus (P)-deficient environments is to exudate low-molecular-weight organic acids (LMWOA). Thus, we aimed to investigate the effect of LMWOA on phosphorus uptake of barley from either fertilizer or inherited soil phosphorus. The experiment was set up in full factorial arrangement in completely randomised design with two phosphorus (0 and 50 mg P kg^?1), five organic acids, LMWOA (malic acid, oxalic acid, citric acid, acetic acid, ascorbic acid), and four organic acid rates (0, 10, 20, and 30 mmol kg^?1). The effects of LMWOA on yield in descending order were: oxalic acid > ascorbic acid > malic acid > acetic acid > citric acid. The maximum P concentration in grain was obtained at 30 mmol kg^?1 LMWOA treatments. As a result, it was found that oxalic acid was the most effective LMWOA in increasing nutrient uptake induced grain yield with and without phosphorous fertilizer application.     

On the use of phosphorus solubility parameters for the evaluation of phosphate plant availability

Abstract

Several phosphate solubility and availability parameters were obtained for calcareous soil samples fertilized with superphosphate, partially acidulated phosphate rock and a mixture of the two. Plant response to the fertilizer application was studied in a greenhouse experiment. The ionic product of calcium carbonate phosphate [Ca₃(HCO₃)₃PO₄] correlated best with the plant response parameters. The correlations of the plant response parameters with the other solubility parameters (CaPO₄, H₂PO₄ or HPO₄ potentials) were higher than that obtained with conventionally determined available soil phosphorus (P).     

Interactions between phosphorus availability and an AM fungus (Glomus intraradices) and their effects on soil microbial respiration, biomass and enzyme activities in a calcareous soil

The interactions between soil P availability and mycorrhizal fungi could potentially impact the activity of soil microorganisms and enzymes involved in nutrient turnover and cycling, and subsequent plant growth. However, much remains to be known of the possible interactions among phosphorus availability and mycorrhizal fungi in the rhizosphere of berseem clover (Trifolium alexandrinum L.) grown in calcareous soils deficient in available P. The primary purpose of this study was to look at the interaction between P availability and an arbuscular mycorrhizal (AM) fungus (Glomus intraradices) on the growth of berseem clover and on soil microbial activity associated with plant growth. Berseem clover was grown in P unfertilized soil (−P) and P fertilized soil (+P), inoculated (+M) and non-inoculated (−M) with the mycorrhizal fungus for 70 days under greenhouse conditions. We found an increased biomass production of shoot and root for AM fungus-inoculated berseem relative to uninoculated berseem grown at low P levels. AM fungus inoculation led to an improvement of P and N uptake. Soil respiration (SR) responded positively to P addition, but negatively to AM fungus inoculation, suggesting that P limitation may be responsible for stimulating effects on microbial activity by P fertilization. Results showed decreases in microbial respiration and biomass C in mycorrhizal treatments, implying that reduced availability of C may account for the suppressive effects of AM fungus inoculation on microbial activity. However, both AM fungus inoculation and P fertilization affected neither substrate-induced respiration (SIR) nor microbial metabolic quotients (qCO₂). So, both P and C availability may concurrently limit the microbial activity in these calcareous P-fixing soils. On the contrary, the activities of alkaline phosphatase (ALP) and acid phosphatase (ACP) enzymes responded negatively to P addition, but positively to AM fungus inoculation, indicating that AM fungus may only contribute to plant P nutrition without a significant contribution from the total microbial activity in the rhizosphere. Therefore, the contrasting effects of P and AM fungus on the soil microbial activity and biomass C and enzymes may have a positive or negative feedback to C dynamics and decomposition, and subsequently to nutrient cycling in these calcareous soils. In conclusion, soil microbial activity depended on the addition of P and/or the presence of AM fungus, which could affect either P or C availability.     

不同类型有机物料的有机磷组成及生物有效性

[目的]研究不同有机物料的有机磷组成及其作为磷源施用后的供磷能力,为化肥磷的有机替代奠定理论基础.[方法]供试有机物料包括粪肥类(猪粪、羊粪)、绿肥类(豌豆、苜蓿和绿豆)、秸秆类(小麦秸秆、玉米秸秆和油菜秸秆).分析了8种有机物料的全磷、有机磷含量和C/P值,采用Bowman-Cole方法测定了有机磷中的活性(LOP)...     

Organic matter effects on phosphorus sorption in sandy soils

Phosphorus (P) sorption processes in soils contribute to important problems in agriculture: a deficiency of this plant nutrient and eutrophication in aquatic systems. Soil organic matter (SOM) plays a major role in sorption processes, but its influence on P sorption remains unclear and needs to be elucidated to improve the ability to effectively manage soil P. The aim of this research was to investigate the influence of SOM on P sorption. The study was conducted in sandy soil profiles and in topsoils before and after removal of SOM with H₂O₂. The results were interpreted with the Langmuir and Freundlich isotherms. Our results indicated that SOM affected P sorption in sandy soils, but that P sorption also depended on specific soil properties (e.g. values of the degree of P saturation (DPS), P sorption capacity (PSC) and pH) often related to land use. Removal of SOM decreased PSC in most of the topsoils tested; other soil properties became important in controlling P sorption. An increase in P desorption observed after SOM removal indicated that SOM was potentially that soil constituent which increased P binding and limited P leaching from these sandy soils.     

Effect of organic manure on organic phosphorus fractions in two paddy soils

We investigated the transformation of the organic P fractions from organic manure in two paddy soils (Ultisol, Entisol) and the influence of organic manure or cellulose on organic P under anaerobic conditions. The results obtained from the P fractionation experiment indicated that during the incubation labile and moderately labile organic P fractions increased in the Ultisol and decreased in the Entisol, which might be related to the difference in the organic matter content of both soils. Immediately after the application of organic manure, a large part of labile and moderately labile organic P supplied with the manure was transformed into moderately resistant organic P, possibly Ca- or Mg-inositol P were transformed into Fe-inositol P. During anaerobic incubation, the labile forms of organic P in the soils treated with organic manure were increased along with the incubation period in the first 4 weeks. The change in the moderately labile fraction was dramatic. It increased sharply in the first 2 weeks, then decreased, which was more pronounced in the soils treated with pig faeces. The moderately resistant fraction decreased during the whole incubation period. This indicated that under anaerobic conditions, the moderately resistant fraction can be transformed into labile and moderately labile organic P fractions, perhaps as Fe³⁺-inositol P is reduced to Fe⁺²-inositol P. Cellulose as an organic substrate had an increasing effect on organic P, especially when it was combined with inorganic P. Therefore, it is suggested that the application of inorganic P fertilizer combined with organic manure may be an effective way of protecting inorganic P against intensive sorption in soils.     

Magnesium-fortified phosphate fertilizers improve nutrient uptake and plant growth without reducing phosphorus availability

Magnesium (Mg) deficiency can significantly limit crop yield and quality. Separate application of straight Mg fertilizer is unattractive because of additional labor costs. Meanwhile, bulk blending Mg with other macronutrient fertilizers is also a suboptimal solution because bulk blended fertilizers often yield poor nutrient distributions. One rapid and economical alternative to alleviating Mg deficiency is to co-granulate macronutrient fertilizers with Mg. However, few commercial products have implemented this approach. One of the barriers hindering the production of Mg-fortified phosphorus (P) fertilizers is the assumption that precipitation of P with Mg will reduce P solubility. In this study, four Mg compounds, anhydrous magnesium sulfate (MgSO₄), magnesium oxide (MgO), anhydrous magnesium chloride (MgCl₂), and dolomite (CaMg(CO₃)₂), were co-granulated with mono-ammonium phosphate (MAP), and their granule strength, Mg and P availabilities, and agronomic effectiveness were evaluated. Results showed that there were no significant differences in P solubility between Mg-fortified MAP and MAP treatments. X-ray diffraction (XRD) indicated that the Mg species after co-granulation were boussingaultite (Mg(NH₄)₂(SO₄)₂·6H₂O), schertelite (Mg(NH₄)₂H₂(PO₄)₂·4H₂O), magnesium hydrogen phosphate (Mg(H₂PO₄)₂), and dolomite (CaMg(CO₃)₂). A pot experiment using an acidic soil demonstrated an average 9.6-fold increase in shoot Mg uptake, 3.0-fold increase in shoot P uptake, and 3.2-fold increase in soybean shoot dry matter in Mg-fortified MAP treatments, compared to those in MAP treatment. The current study provides a simple, effective, and low-cost approach for the addition of Mg to macronutrient fertilizers, to minimize Mg deficiency.     

Effect of low-molecular-weight organic acids on Cl- adsorption by variable charge soils

Low-molecular-weight (LMW) organic acids exist widely in soils and have been implicated in many soil processes.The objective of the present paper was to evaluate effect of two LMW organic acids, citric acid and oxalic acid, on Cl^- adsorption by three variable charge soils, a latosol, a lateritic red soil and a red soil, using a batch method. The results showed that the presence of citric acid and oxalic acid led to a decrease in Cl- adsorption with larger decreases for citric acid. Among the different soils Cl- adsorption in the lateritic red soil and the red soil was more affected by both the LMW organic acids than that in the latosol.     

Kinetics of phosphorus release from calcareous soils under different land use in Iran

The rate of phosporus (P) release from soils can significantly influence P fertility of soils. The objectives of this study were to investigate the effects of land‐use types on the kinetics of P release under different management practices and the relationship between kinetic parameters and soil physical and chemical properties from calcareous soils. The kinetics of P release in 0.01 M CaCl₂ was studied in surface samples of 30 calcareous soils planted to garlic, garden, pasture, potato, vegetables, and wheat. Trend in P‐release kinetics was similar between land‐use types. Significantly different quantities of P were released under different land use. The maximum amount (average of five soils) (46.4 mg kg^–1) of P was released in soil under potato and the minimum amount (10.4 mg kg^–1) under pasture. The kinetics of P release from soils can be described as an initial rapid rate followed by a slower rate. Different models were used to describe P release. In general, parabolic diffusion and power equation were found to be appropriate for modeling P release. The P‐release rate for the soils was estimated by parabolic equation for the studied land‐use types. The constant b was lower for pasture and wheat than for garlic and potato. The relationship between the rate of P release with Olsen‐P was linear, while it was curved with respect to the CaCl₂‐P, indicating that release of P was diffusion‐controlled. When the kinetic parameters of models were regressed on soil properties, CaCl₂‐P and CaCO₃ appeared to be the most important soil properties influencing P‐release rates in these soils.     

磷素吸附特性演变及其与土壤磷素形态、土壤有机碳含量的关系

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)。