Effect of Submergence on Iron Transformation and Phosphorus Availability in Calcareous Soils

A thermostatic incubation experiment was carried out to estimate the effects of flooding periods,stalk application and P addition of Fe transformation and P availability in calcareous soils.Submergence increased amorphous Fe,especially in the case of stalk application.The newly formed amorphous Fe with a great surface area played an important role in Psorption;and submergence also stimulated the dissolution of inorganic P,thus increasing the availability of soil P in calcareous soils.Meanwhile,a part of soluble P was absorbed and fixed again on the surface of newly formed amorphous Fe,thus resulting in a decrease of P availability.Soil rapidly available P increased after 150-day incubation.There existed significantly negative correlations between soil amorphous Fe content and soil Fe-P and rapidly available P contents.Submerged conditions promoted the transformation of inorganic P added toward Fe-P in calcareous soils,especially in the case of stalk application.     

共施磷酸二氢钙和硫酸铵对土壤中钾形态转化的影响

Soil potassium (K) deficiency has been increasing over recent decades as a result of higher inputs of N and P fertilizers concomitant with lower inputs of K fertilizers in China; however, the effects of interactions between N, P, and K of fertilizers on K status in soils have not been thoroughly investigated for optimizing N, P, and K fertilizer use effciency. The influence of ammonium sulfate (AS), monocalcium phosphate (MCP), and potassium chloride application on K fractions in three typical soils of China was evaluated during 90-d laboratory soil incubation. The presence of AS significantly altered the distribution of native and added K in soils, while addition of MCP did not significantly affected K equilibrium in most cases. Addition of AS significantly increased water-soluble K (WSK), decreased exchangeable K (EK) in almost all the soils except the paddy soil that contained considerable amounts of 2:1 type clay minerals with K added, retarded the formation of fixed K in the soils with K added, and suppressed the release of fixed K in the three soils without K added. These interactions might be expected to influence the K availability to plants when the soil was fertilized with AS. To improve K fertilizer use effciency, whether combined application of AS and K was to be recommended or avoided should depend on K status of the soil, soil properties, and cropping systems.     

紫色水稻土的有机金属-矿物胶体复合物对磷的吸附、解吸特征

The kinetic characteristics of P adsorption and desorption by organo-mineral colloidal complexes (OMC) were studied using acid, calcareous and neutral purple paddy soils taken from Chongqing and Sichuan, China. The results showed that the P adsorption capacity of the organo-mineral colloidal complexes differed with the soil tyes, being higher for the acid and calcareous purple soils than for the neutral purple soils. Partial removal of the organic matter increased the adsorption capacity of the colloidal complexes. A very significant positive correlation was found between the amounts of P desorbed from OMC and the P saturation degrees. The P adsorption reaction was quick at the early stage and slowed later. The raise of temperature increased P adsorption capacity and P adsorption rate of the colloidal complexes. The adsorption processes could be described by the Elovich equation.     

玉米秸秆应用和腐化对钙质苏打土改良的影响: 实验室试验研究

A laboratory lysimeter experiment was conducted to investigate the effects of forage corn (Zea mays L.) stalk application on the CO₂ concentration in soil air and calcareous sodic soil reclamation. The experimental treatments tested were soil exchangeable sodium percentage (ESP) levels of 1, 11, and 19, added corn stalk contents of 0 to 36 g kg^-1, and incubation durations of 30 and 60 days. The experimental results indicated that corn stalk application and incubation significantly increased CO₂ partial pressure in soil profile and lowered pH value in soil solution, subsequently increased native CaCO₃ mineral dissolution and electrolyte concentration of soil solution, and finally significantly contributed to reduction on soil sodicity level. The reclamation effciency of calcareous sodic soils increased with the added corn stalk. When corn stalks were added at the rates of 22 and 34 g kg^-1 into the soil with initial ESP of 19, its ESP value was decreased by 56% and 78%, respectively, after incubation of 60 days and the leaching of 6.5 pore volumes (about 48 L of percolation water) with distilled water. Therefore, crop stalk application and incubation could be used as a choice to reclaim moderate calcareous sodic soils or as a supplement of phytoremediation to improve reclamation effciency.     

Natural Nitrogen-15 Abundance of Ammonium Nitrogen and Fixed Ammonium in Soils

The present article deals with the natural nitrogen-15 abundance of ammonium nitrogen and fixed ammonium in different soils.Variations in the natural ^15N abundance of ammonium nitrogen mineralized in soils under anaerobic incubation condition were related to soil pH.The δ ^15N of mineralizable N in acid soils was lower but that in neutral and calcareous soils was higher compared with the δ ^15N of total N in the soils.A variation tendence was also found in the δ ^15N of amino-acid N in the hydrolysates of soils.The natural ^15N abundance of fixed ammonium was higher than that of total N in most surface soils and other soil horizons,indicating that the increase of δ ^15N in the soil borizons beneath subsurface horizon of some forest soils and acid paddy soils was related to the higher δ ^15N value of fixed ammonium in the soil.     

Application of Ground Phosphate Rock to Dimmish the Effects of Simulated Acid Rain on Soil Properties

The effects of simulated acid rain retained in soil on the properties of acid soil and its diminishing by application of ground phosphate rock were investigated by using the sorption method.Results show as follows:(1)For yellow brown soil,the effect of simulated acid rain on the properties of soil with a pH value of 5.9 was relatively small,except a great quantity of acid rain deposited on it.(2) for red soil,the effect of simulated acid rain on the properties of soil was significant.With the increase of the amount of acid deposition,the pH value of soil was declined,but the contents of exchangeable H^ ,Al^3 and Mn^2 and the amount of SO4^1- retention were increased.(3) Many properties of acid soils could be improved by applying ground phosphate rock.For example,pH value of soils and the amounts of available P and exchangeable Ca^2 and Mg^2 were increased,and the amounts of exchangeable H^ and Al^3 and SO4^2- retained was reduced.The application of ground posphate rock could effctively diminish the pollution of acid rain to soil.     

Factors Influencing Runoff P Losses from Farmlandsof the Dianchi Lake Watershed in Yunnan, China

Effects of factors such as slope, surface soil texture, fertilization and crop cover with different rainfall intensitieson phosphorus (P) losses in farmland runoff of the Dianchi Lake Watershed in Yunnan Province of China were studiedthrough a rainfall simulation test using a red soil, one of the most widely distributed soils of the study area. Resultsshowed that the runoff concentrations of total phosphorus (TP) and P losses differed with the slope, being highest whenthe slope was 18~. At two different rainfall intensities, the runoff TP and P losses had a similar decreasing trend asthe surface soil texture became coarser, therefore applying the grit would decrease P in runoff from soils of farmland onslopes with heavier textures. With wheat as a crop cover the runoff TP concentrations and P losses were significantlylower than those of the bare soil. This showed that plant cover would greatly decrease P in runoff from the farmland ofthe study area. The TP concentration in runoff from the soil two days after fertilization doubled when compared withthat from the non-fertilized soil, indicating that fertilization could mean a dramatic rise in P runoff if irrigation or heavyrainfall occurred immediately after application and that no fertilization before a rain and no irrigation immediately afterfertilization would reduce runoff P loss from the farmland of the study area.     

Study on Transfer of Ni in Soil—Plant System Using ^63Ni Tracer Method

A study was carried out on the transfer of native and added Ni towards plant both in different soils and at different time by using ^63 Ni tracer technique.The transfer of added Ni in soil was greater than native Ni and declined as time increased.The mobility was greater for soluble plus exchangeable fraction of soil Ni but very smaller for residual and Fe/Mn oxide bound fractions.These indicated that Ni was more mobile and more harmful in soils with a low pH and /or low content of Fe/Mn oxides.     

土壤中氮磷钾肥转化中的交互作用: Ⅰ.土壤pH的动态变化

Dynamic changes of soil pH as influenced by ammonium sulfate (AS), monocalcium phosphate (MCP),potassium chloride (KCl) and their interaction in soils were evaluated in incubation experiments. Applyingthese fertilizers significantly reduced soil pH values in all cases and followed sequences of AS ＞ MCP ＞KCl, MCP ＞ KCl ＞ AS and KCl ＞ AS ＞ MCP for the paddy, calcareous and red soils, respectively. TheAS-induced reduction of pH in the three soils followed the sequence of red soil ＞ paddy soil ＞ calcareous soil,while in MCP and KCl systems the reduction of pH followed the sequences of calcareous soil ＞ paddy soil ＞red soil and red soil ＞ calcareous soil ＞ paddy soil, respectively. The interactions of the NPK fertilizers on pHwere significant. MCP plus KCl or MCP plus AS reduced pH values more than the fertilizers applied solelyin the paddy soil, but AS partly counteracted the effect of MCP on pH in the 1 d sample of the calcareoussoil. The effect of MCP on pH was trivial when MCP was applied in combination with KCl or AS in the redsoil. When applied in combination with AS, KCl did not affect soil pH initially, but suppressed the reductionof pH at the later incubation stage, which was related to inhibition of nitrification by KCl in the soils.     

不同土壤水分状况下遮蔽对棉花叶片气体交换的影响

An incubation experiment was carried out in laboratory to study the effect of temperature,moisture,phosphorus,organic matter,cropping and previous elemental sulfur application on elemental sulfur oxidation in four selected soils,fluvo-aquic soil,black soil,yellow-brown soil and red soil,In all the soils tested,sulfur oxidation rate was influenced by temperature and the temperature coefficient(Q10) values at the range from 10 to 30℃ were 4.41,,6.19 and 3.71 for the four soils,respectively.The rate of sulfur oxidation was parabolically related to soil water content.The optimum moisture content for the maximum oxiation rate was different among soils,Phosphorus increased the oxidation rate of elemental sulfur by 57.7%,33.1%,21.7% and 26.4% for the above four soils,respectively,compared with the control (no phosphorus applied).Organic material of corn straw which was gound and passed through a 0.5-mm sieve also increased th oxidation rate of elemental sulfur in the four soils by 59.8%,7.8%,39.2% and 540.4%,respectively.Elemental sulfur which was applied previously to soils significantly enhanced the oxidation of elemental sulfur subsequently added and increased sulfur-oxidizing populations such as autotrophic elemental sulfur oxidizers with pH optimum 6.8,autotrophic thiosufate oxidizers with pH optimum 6.8,heterotrophic thiosulfate oxidizers and heterotrophic sulfate producers.Cropping had little effect on elemental sulfur-oxidizing potentiality of soils.     

钾和碳氮比对铵态土壤转化过程的影响

Two soils, one consisting of 1：1 clay minerals at pH 4.5 and the other containing 2：1 clay minerals at pH 7.0, were used to estimate the conversion of added NH4^＋ under different C/N ratios （glucose as the C source） and the addition of potassium. Under lower C/N ratios （0：1 and 5：1）, a large part of the added NH4^＋ in the acid soil was held in the forms of either exchangeable or water soluble NH4^＋ for a relatively long time and under higher C/N ratio （50：1）, a large amount of the added NH4^＋ was directly immobilized by microorganisms. In the second soil containing appreciable 2：1 type clay minerals a large part of the added NH4^＋ at first quickly entered the interlayer of the minerals under both lower and higher C/N ratios. In second condition, however, owing to microbial assimilation stimulated by glucose the newly fixed NH4^＋ could be completely released in further incubation because of a large concentration gradient between external NH4^＋ and fixed NH4^＋ in the mineral interlayer caused by heterotrophic microorganisms, which imply the fixed NH4^＋ to be available to plants. The results also showed that if a large amount of K＋ with carbon source together was added to soil, the higher K＋ concentration of soil solution could impede the release of fixed NH4^＋, even if there was a lot of carbon source.     

土壤性质对砂土亚表层磷迁移的影响

The soil factors influencing the potential migration of dissolved and particulate phosphorus （P） from structurallyweak sandy subsoils were evaluated by means of soil column leaching experiments. Soil colloids were extracted from two types of soils to make the colloid-bound forms of P solution. Eight sandy soils with diverse properties were collected for packing soil columns. The effects of influent solutions varying in concentrations of colloids, P, and electrolyte, on the transport of P and quality of leachates were characterized. P migration in the soils was soil property-dependent. High soil electrical conductivity values retarded the mobility of colloids and transportability of colloid-associated P （particulate P）. Soil electrical conductivity was negatively correlated with colloids and reactive particulate P （RPP） concentrations in the leachates, whereas, the total reactive P （TRP） and dissolved reactive P （DRP） concentrations in the leachates were mainly controlled by the P adsorption capacity and the P levels in the subsoil. The reactive particulate P in the leachates was positively correlated with the colloidal concentration. Increased colloidal concentration in the influent could significantly increase the colloidal concentration in the leachates. Elevated P concentration in the influent had little effect on P recovery in the leachates, but it resulted in significant increases in the absolute P concentration in the leachates.     

褐煤腐殖酸对不同土壤上小麦生长的影响

Humic acid(HA),a fairly stable product of decomposed organic matter that consequently accumulates in ecological systems,enhances plant growth by chelating unavailable nutrients and buffering pH.We examined the effect of HA derived from lignite on growth and macronutrient uptake of wheat(Triticum aestivum L.) grown in earthen pots under greenhouse conditions.The soils used in the pot experiment were a calcareous Haplustalf and a non-calcareous Haplustalf collected from Raisalpur and Guliana,respectively,in Punjab Province,Pakistan.The experiment consisted of four treatments with HA levels of 0(control without HA),30,60,and 90 mg kg -1 soil designated as HA 0,HA 1,HA 2,and HA 3,respectively.In the treatment without HA(HA 0),nitrogen(N),phosphorus(P),and potassium(K) were applied at 200,100,and 125 mg kg -1 soil,respectively.Significant differences among HA levels were recorded for wheat growth(plant height and shoot weight) and N uptake.On an average of both soils,the largest increases in plant height and shoot fresh and dry weights were found with HA 2(60 mg kg -1 soil),being 10%,25%,and 18%,respectively,as compared to the control without HA(HA 0).Both soils responded positively towards HA application.The wheat growth and N uptake in the non-calcareous soil were higher than those of the calcareous soil.The HA application significantly improved K concentration of the non-calcareous soil and P and NO 3-N of the calcareous soil.The highest rate of HA(90 mg kg -1 soil) had a negative effect on growth and nutrient uptake of wheat as well as nutrient accumulation in soil,whereas the medium dose of HA(60 mg kg -1 soil) was more efficient in promoting wheat growth.     

同位素动力学方法评价中国亚热带地区主要酸性土壤磷状况及生物有效性的适用性

A ^32P isotope kinetic approach was used to describe the chemical status and bioavailability of phosphorus in 32 acidic soils from subtropical China.By determining the residual radoactivity,rt,in soil solution at different time,t,after introduction of the isotope in an amount of R into the steady soil-water system,a well-defined isotope kinetic model was established,and upon this model the decrease rate ,n,of log(rt/R) with respect to logt,the mean sojourn time of phosphate ions in solution,the mean exchange rate and the mean flux of phosphate ions between soil solid and solution phases were calculated.Other parameters,such as the exchangeable P within the first minute of isotope exchange(E1),and P in various compartments that could be exchanged with solution phosphte ions at different perods of time,were also obtained.For these acidic soils,the r1/R had a significant correlation with the contents of clay and free Al2O3 where r1 is the radioactivity in solution 1 minute after introduction of the isotope into the system.Parameter n also had a significant correlation with clay content and a neagtive correlation with soil pH,E1 values and Cp,the P concentration in soil solution,also Significantly correlated with clay and sesquioxide contents of the soils.these indicated that these isotope kinetic parameters were largely influenced by P-fixing components of the soils.For the soils with strong P-fixing ability,the E1 values overestimated labile P pools and hence their correlations with A values and plant P uptake were not significant .The other iostope kinetic parameters also had no significant correlation with plant P uptak.On the other hand,the convetional chemical-extracted p correlated better with plant P uptake .It was concluded that the iostope kinetic method could assess the p chemical status yet it would inappropriate in predicting plant available P for soils with a high P-fixing ability as the problem of an overestimation of soil lable P in these soils was inevitable.     

中性盐和pH对红壤、砖红壤胶体交换性酸的影响

In the present work, the exchangeable acidity of a red soil colloid and a latosol colloid at different pH during reacting with four neutral salts was measured. The results show that the exchangeable acidity increased with increasing amounts of the neutral salts added, and the relation between them was almost linear. When the amount of the neutral salt added was lower than a certain value, the slope of the line was high, and the slope turned low when the amount exceeded that value, so there was a turning point in each line. The addition amounts of the neutral salts for the turning points were affected by the cation species of the neutral salts, but pH had less effect on them. After the turning points occurred, the exchangeable acidity of the red soil colloid still gradually increased with the addition amounts of the neutral salts, but that of the latosol colloid did not increase any more. The exchangeable acidity in NaClO₄, KClO₄ and NaCl solutions increased at first, and then decreased with increasing pH, that is to say, peak values appeared. The peak positions of the exchangeable acidity in relation to pH changed with neutral salt solutions and were affected by the surface characteristics of the soil colloids, but not affected by the amounts of the neutral salts added. The exchangeable acidity in the Ba(NO₃)₂ solution increased continuously with increasing pH. The exchangeable acidity of the red soil colloid was obviously larger than that of the latosol colloid.     

长期施肥对黑土磷素的影响

A twelve-year field trial was carried out to determine the impact of long-term fertilization on phosphorus (P) distribution in the soil profile, P balance, and the transformation and availability of soil P in a black soil (Phaeozem, FAO). Under a wheat-soybean-corn rotation, during twelve years where no fertilizer was applied, crops removed 60 and 81 mg P kg^-1 soil in the control and NK treatment, respectively. About one third of the P absorbed by crops was originated from organic P. Ca2-P, Ca8-P, Al-P and Fe-P were the main forms of inorganic P absorbed by crops. The surplus P from fertilization remained in the 0-20 cm soil layer and increased with the application rate of P. The combined application of NP or NPK increased available P to a lesser extent than the combined application of PK. Fertilizer P had mainly transformed to the Al-P, Fe-P, Ca2-P, and Ca8-P forms. By using the P budget (X), changes in total P (Y1) and available P (Y2) in soils under the current cropping system could be predicted by the equations: Y1 = 0.02 1.01X and Y2 = 2.08 0.15X.     

A conceptual framework and an empirical test of complementarity and facilitation with respect to phosphorus uptake by plant species mixtures

Plant species have different traits for mobilizing sparingly soluble phosphorus (P) resources,which could potentially lead to overyielding in P uptake by plant species mixtures compared to monocultures due to higher P uptake as a result of resource (P) partitioning and facilitation.However,there is circumstantial evidence at best for overyielding as a result of these mechanisms.Overyielding (the outcome) is easily confused with underlying mechanisms because of unclear definitions.We aimed to define a conceptual framework to separate outcome from underlying mechanisms and test it for facilitation and complementarity with respect to P acquisition by three plant species combinations grown on four soils.Our conceptual framework describes both mechanisms of complementarity and facilitation and outcomes (overyielding of mixtures or no overyielding) depending on the competitive ability of the species to uptake the mobilized P.Millet/chickpea mixtures were grown in pots on two calcareous soils mixed with calcium-bound P (CaP) and phytate P (PhyP).Cabbage/faba bean mixtures were grown on both acid and neutral soils mixed with P-coated iron (hydr)oxide (FeP) and PhyP.Wheat/maize mixtures were grown on all four soils.Rhizosphere carboxylate concentration and acid phosphatase activity (mechanisms) as well as plant P uptake and biomass (outcome) were determined for monocultures rhizosphere and species mixtures.Facilitation of P uptake occurred in millet/chickpea mixtures on one calcareous soil.We found no indications for P acquisition from different P sources,neither in millet/chickpea,nor in cabbage/faba bean mixtures.Cabbage and faba bean on the neutral soil differed in rhizosphere acid phosphatase activity and carboxylate concentration,but showed no overyielding.Wheat and maize,with similar root exudates,showed overyielding (the observed P uptake being 22%higher than the expected P uptake) on one calcareous soil.We concluded that although differences in plant physiological traits (root exudates) provide necessary conditions for complementarity and facilitation with respect to P uptake from different P sources,they do not necessarily result in increased P uptake by species mixtures,because of the relative competitive ability of the mixed species.     

北京地区菜园土壤磷素积累的剖面特征及对环境的潜在影响

Profile characteristics of accumulated P in 10 representative soils of vegetable fields in suburban districts of Beijing were investigated. Bioavailability of the accumuIated P and its potential effect on the environment were studied in a greenhouse pot experiment and a soil column experiment. The results showed that theconcentration of Olsen-P in the 0-20 cm soil samples of the vegetable fields ranged from 22.1 to 358.0 mg kg^-1, which was 2 to 10 times higher than that of the crop fields in the suburbs of Beijing. Most of theexcessive phosphorus was accumulated in the topsoils. The longer the soils cultivated with vegetables, thehigher the soil total P, Olsen-P and organic matter concentration. Accumulated P in the soils from vegetablefields had higher bioavailability. Application of phosphorus fertilizer could not increase the dry weights ofcucumbers, Chinese cabbage, and rape seedlings continuously planted. The soil column study showed high P concentration (> 0.6 mg L^-1) in the leachates from the columns of the vegetable field soils with high accumulated P, which has a potential effect on the groundwater and natural water quality.     

Transformation of Phosphate Fertilizers with Different Solubilities in Calcareous Soils

In this research work,the authors,using the recently developed method of fractionating the forms of inorganic phosphorus in calcareous soils,have studied the transformation processes of inorgnic phosphorus in three different phosphate fertilizers,i.e.,superphosphate,diammonium phosphate and calcium magnesium phyosphate,being commonly used in China,during a period of 3 years after their application to calcareous soils,and based on the experimental results obtained,some problems in current use of phosphate fertilizers are discussed.     

长期施磷对土壤磷素吸附演变的影响

Knowledge of phosphorus （P） behavior in long-term fertilized soils is essential for programming fertilization practices and for sustaining environmental quality. The long-term （1984-1997） effects of various fertilization treatments on P changes and sorption isotherms as well as the relationship of soil properties to P sorption and P forms were evaluated in an Ustic Isohumisol, a calcareous soil, on the Loess Plateau, China. Compared to 1984, after 13 years of crop production, total soil P in the no-P treatments （control and N treatment） decreased by 5%-7%, but in the phosphorus fertilizer alone （P）, nitrogen and phosphorus fertilizers in combination （NP）, manure alone （M）, and nitrogen and phosphorus fertilizers and manure in combination （NPM） treatments, it increased by 22%, 19%, 28%, and 58%, respectively. Residual fertilizer P was found mainly in NH4Ac-soluble P （Cas-P）, followed by NaHCO3-soluble P （NaHCO3-P）, and NH4F-soluble P （Al-P）. Phosphorus sorption in the soils with different fertilization practices fit the Langmuir equations. Phosphorus sorption capacity in the no-P treatments increased, whereas it decreased in the P-included treatments （P, NP, and NPM treatments）. Phosphorus sorption maximum （Qm） was significantly and negatively correlated to inorganic P including NaHCO3-P, Cas-P, NaOH-Na2CO3-soluble P （Fe-P）, and Al-P （P ≤ 0.01）. Moreover, long-term fertilization increased soil organic carbon in the NP, M, and NPM treatments and decreased pH in the NP and NPM treatments. Thus, the ability of the soil to release sorbed P to the environment increased under long-term P fertilization.