Calculating changes of legume rhizosphere soil pH and soil solution phosphorus from phosphorus uptake

Abstract

Some legumes are known to reduce rhizosphere soil pH which in turn usually increases soil solution P, P_li and therefore increases P uptake. In an initial experiment with a nonlegume [corn (Zea mays L.)], observed P uptake agreed closely with predicted P uptake while with a legume [alfalfa (Medicago sativa L.)], observed P uptake was greater than predicted P because the rhizosphere was acidified, P_li increased, and more P was absorbed. Using a pot experiment, this investigation calculates the change in rhizosphere pH and P_li necessary to have predicted P uptake obtained with a mechanistic uptake model agree with observed P uptake. The pot experiment was conducted with alfalfa, faba bean (Vicia faba L.) and Austrian winter pea (Lathyrus hirsutus) grown on Chalmers silt loam (fine‐silty, mixed, mesic Typic Haplaquolls) limed to pH levels of 5.72, 6.30, 7.22 and 8.30. Predicted phosphorus uptake at each pH level was calculated with the uptake model using the data for bulk soil. The relation of predicted P uptake to initial soil pH was determined, then this relation was used with observed P uptake to calculate rhizosphere pH. Subsequently, P_li as a function of pH was determined and used to calculate rhizosphere P_li. In this study, the calculations indicate that legumes reduced rhizosphere soil pH by 0.39 to 0.77 units and increased P availability by 20.8 to 241.7%.     

Release of plant-available silicon from various silicon-rich amendments into soil solutions and leachates

Journal of Soils and Sediments - This study assessed the efficacy of selected silicon-rich soil amendments in terms of their ability to provide dissolved silicon (Si) to soil solutions during a...     

Equilibrium composition and properties of soil solutions

The high dynamics of their composition are a characteristic feature of soil solutions, which hampers the use of data on the concentrations and activities of elements in the physicochemical studies of soils. The chemical potentials of independent components, whose values depend of the dynamics of the solution composition only slightly, are more stable and efficient parameters. The calculation of the equilibriums by physicochemical simulation and the data on the composition of the water extracts and soil solutions indicated that, in the A1 horizon of a leached chernozem, the chemical potential of the calcium varied from −173.8 to −174.3 kcal/mol and that of magnesium varied from −150.9 to −151.5 kcal/mol when the calcium and magnesium concentrations changed by more than 20 times. In the B1 horizon of the crusted solonetz, the chemical potential of the sodium varied from −81.3 to −82.0 kcal/mol when its concentration changed by 2–3 times. The determination of the chemical potentials of the independent components (K, Na, Ca, Mg, Mn, Fe, Al, and Si) in the relatively simple basis subsystem of the solution and single-component mineral phases with known solubilities allows calculating the standard Gibbs energies of the other soil phases equilibrated with the solution.     

Bioavailability of DOC in leachates, soil matrix solutions and soil water extracts from beech forest floors

The biodegradability of dissolved organic carbon (DOC) in different fractions from the forest floor was studied. Soil leachate (SL, the soil solution in macropores which is freely drained from forest floor after rainfall), the soil matrix solution (SMS, the soil solution in meso-/micropores of the soil matrix), and soil water extracts (SWE) from two different beech forest floors were compared. Zero-tension and tension lysimeters were used to collect SL and SMS, respectively. Loss of DOC (during 21 days) and respiration of CO₂-C (during 7 days) were used as conventional measures of the availability of DOC. Bacterial production, measured using the leucine incorporation technique, and bacterial growth efficiency were also estimated. All methods were used to study differences in biodegradability between plots with and without ground flora (Deschampsia flexuosa or Anemone nemorosa) and different type of forest floor (with an organic (O) horizon or a mull (A) horizon). There were no differences in bioavailability of DOC from soil solutions extracted from plots with and without ground flora. The bioavailability of DOC in the different collected soil solutions varied, however. DOC in SWE was the most available, with a mean of 39% of DOC-loss in 21 days, and 18% of DOC being respired in 7 days. DOC in soil matrix solution was the least available of the soil solutions (7% respired), significantly less than DOC in soil leachate (11% respired). The methods measuring biodegradation of DOC, DOC-loss and CO₂-C respiration gave similar results and were comparable to bacterial production and bacterial growth efficiency, with the exception of SWE from the O-horizon at the D. flexuosa site, which had low bacterial production and bacterial growth efficiency, indicating a limitation of the bacterial growth. This study is one of the first to use bacterial production and bacterial growth efficiency for measuring bioavailability in terrestrial environments, giving an extra dimension for the process of biodegradation of DOC.     

Dissolved phosphorus composition of grassland leachates following application of dairy‐slurry size fractions

Appropriate management of P from slurry can increase crop production and decrease nutrient loss to water bodies. The present study examined how the application of different size fractions of dairy slurry influenced the quantity and composition of P leached from grassland in a temperate climate. Soil blocks were amended (day 0 = start of the experiment) with either whole slurry (WS), the > 425 μm fraction (coarse slurry fraction, CSF), the < 45 μm slurry fraction (fine liquid slurry fraction, FLF), or not amended, i.e., the control soil (CON). Deionized water was added to the soil blocks to simulate six sequential rainfall events, equivalent to 250 mm (day 0.2, 1.2, 4.2, 11.2) or 500 mm of rainfall (day 18.2 and 25.2), with leachates collected the following day. The results showed that total dissolved P (TDP), dissolved reactive P (DRP), dissolved unreactive P (DUP), orthophosphate, phosphomonoester, and pyrophosphate concentrations generally decreased with the increasing number of simulated rain events. Total dissolved P was leached in the following order WS > FLF ≈ CSF > CON. Dissolved organic C was correlated with TDP, DRP, and DUP in leachates of all treatments. The highest concentrations of dissolved phosphomonoesters and pyrophosphate (147 μg P L^–1 and 57 μg P L^–1, respectively) were detected using solution ³¹P‐NMR spectroscopy in the WS leachates. Overall, there were significant differences observed between slurry treatments (e.g., relative contributions of inorganic P vs. organic P of dissolved P in leachates). Differences were independent from the rate at which slurry P was applied, because the highest dissolved P losses per unit of slurry P applied were measured in the FLF, i.e., the treatment that received the smallest amount of P. We conclude that the specific particle‐size composition of applied slurry influences dissolved P losses from grassland systems. This information should be taken in account in farm‐management approaches which aim to minimizing dissolved slurry P losses from grassland systems.     

外源腐殖酸对棕壤有机磷组分的影响

采用Bowman和Cole提出的有机磷分组方法,对施入外源腐殖酸条件下,不同时期棕壤有机磷的组成变化进行测定。结果表明,施入外源腐殖酸,在培养的各个时期,有机磷各组分所占比例的基本格局没有改变,依然是中等活性有机磷>中等稳定性有机磷>高稳性有机磷>活性有机磷。施入外源腐殖酸后,在培养的30 d,活性有机磷均下降;在培养的60 d和90 d,施入高量腐殖酸的土壤,活性有机磷升高。施入外源腐殖酸,在培养的各个时期均可明显增加中等活性有机磷的含量,特别是在施入高量腐殖酸时增加的最多;同时还可降低中等稳定性有机磷的含量,在施入高量腐殖酸时降低的最多。     

外源植酸酶对土壤有机磷组分含量的影响

采用室内培养的方法,研究了不同用量外源植酸酶在不同培养时期对土壤有机磷组分及数量的影响。结果表明,添加外源植酸酶各处理在各培养时期土壤活性和中等活性有机磷的含量和比例均高于对照,各处理间呈极高量>高量>中量>低量>对照,其含量随培养时间的延长呈增加趋势,至培养第40 d达最高值;而中稳性和高稳性有机磷含量均低于对照,各处理间呈极高量<高量<中量<低量<对照,其含量随培养时间的延长呈减少趋势,至培养第40 d达最低值;添加外源植酸酶各处理的有机磷总量均低于对照,并随植酸酶添加量的增加而减小。外源植酸酶可以促进土壤稳定性有机磷向活性有机磷转化,乃至向无机磷转化,从而提高了土壤有机磷素的有效性。     

外源腐殖酸对棕壤有机磷组分的影响

采用Bowman和Cole提出的有机磷分组方法，对施人外源腐殖酸条件下，不同时期棕壤有机磷的组成变化进行测定。结果表明，施入外源腐殖酸，在培养的各个时期，有机磷各组分所占比例的基本格局没有改变，依然是中等活性有机磷〉中等稳定性有机磷〉高稳性有机磷〉活性有机磷。施入外源腐殖酸后，在培养的30d，活性有机磷均下降；在培养的60d和90d，施入高量腐殖酸的土壤，活性有机磷升高。施入外源腐殖酸，在培养的各个时期均可明显增加中等活性有机磷的含量，特别是在施入高量腐殖酸时增加的最多；同时还可降低中等稳定性有机磷的含量，在施入高量腐殖酸时降低的最多。     

Determination of low concentrations of organic phosphorus in soil solution

Abstract

Phosphorus (P) export from agricultural land is an important source of water‐quality deterioration in many areas of the world. Part of the total phosphorus in the soil solution is represented by dissolved organic P at concentrations that can be as low as 1x10^‐6 M of P. The suitability of four digestion methods for the destruction of organic P and determination of orthophosphate at low concentrations and small volumes using the malachite green method has been evaluated. The acid digestion procedures evaluated were 1) sulfuric and perchloric acid, 2) sulfuric acid and potassium persulphate, 3) nitric acid, and 4) nitric and perchloric acid. As inositol hexaphosphate (IHP) represents one of the more resistant molecules to acid hydrolysis in soils, this compound has been chosen to assess the recovery assay of the recommended procedure. The digestion procedures were adapted for the malachite green spectrophotometric method, in order to obtain lower analytical limits for P determination. The sulfuric‐perchloric acid digestion gave excellent recovery and reproducibility, and can therefore be used for determining organic P in solution at concentrations as low as 6.45x10^‐7 M.     

The effect of phosphorus addition,soil moisture,and plant type on soil nematode abundance and community composition

Journal of Soils and Sediments - Environmental variables such as soil moisture and phosphorus (P) might influence above- and below-ground biodiversity. In this study, we investigated the rarely...     

固体磷肥和液体磷肥对石灰性土壤不同形态无机磷及磷肥肥效影响的研究

土壤磷固定是影响石灰性磷肥肥效的主要原因。本文在田间滴灌条件下采用连续浸提的方法对液体磷肥和固体颗粒磷肥及其不同施用方法对石灰性土壤各形态无机磷含量动态变化的影响进行了研究,并比较了不同处理下加工番茄磷素营养效应。结果表明:各施肥处理0—20 cm土层Ca2-P和Ca8-P含量随施肥时间明显下降,而Ca10-P含量则显著上升,表明磷肥在石灰性土壤中不断向Ca10-P转化并被固定。液体磷肥追肥处理0—20 cm土层Ca2-P含量在各时期均显著高于其他施肥处理(P＜0.05),且液体磷肥追肥可以明显保持土壤0—20 cm土层较高的Ca8-P含量。与其他施肥处理相比,液体磷肥追施可减少石灰性土壤对磷的固定,增加0—20 cm土层Ca2-P和Ca8-P含量(P＜0.05),显著提高土壤磷的有效性。液体磷肥追施处理可显著提高加工番茄叶片含磷量和经济产量(91725 kg/hm2)。与传统过磷酸钙颗粒磷肥作基肥处理（CK1）相比,液体肥料全做追肥可使加工番茄经济产量提高26.7%,并明显提高了磷肥利用率。在滴灌条件下石灰性土壤上液体磷肥分次追施比传统的固体颗粒磷肥基施具有明显的优势,是一种非常具有应用前景的施肥方式。     

The composition of the soil solution as influenced by fertilization and nutrient uptake

The composition of the soil solution in unfertilized and well-fertilized plots of three long-term field experiments has been determined at the beginning and at the end of the growing season. All the plots were manured and the K and P fertilizers given in the autumn before the growth of sugar beet. N was applied in the spring, 3–4 weeks before the first soil sampling.The soil solution was removed at a pressure of 5 atm. The composition and the corresponding osmotic pressure were calculated for the moisture contents at field capacity and wilting point.In spring the salt concentrations, cations + anions, at the field capacity were in the range 91–97 mmoles/l in the fertilized plots. In autumn the concentration had dropped to 13.9–20.3, a decrease of 78–85%. At the wilting point, the concentrations in spring were as high as 211–307 mmoles/l and in autumn 31.5–69 mmoles/l. The corresponding osmotic pressures at field capacity in the spring ranged 2.2–2.3 atm. and at wilting point 5.1–7.4 atm.In spring the unfertilized plots showed concentrations of 16–21 mmoles/l and osmotic pressures of 0.38–0.51 atm., the values decreasing 52–65% during the growing season.It was pointed out that the high soil-solution concentration and osmotic pressure at low moisture contents may lead to an unfavourable effect on root metabolism. Further, the obscuring effect of the varying soil-solution concentration on the relationships between root ion exchange and nutrient uptake by plants has been discussed.     

The efficiency of sequential extraction of phosphorus in soil and sediment: insights from the oxygen isotope ratio of phosphate

Journal of Soils and Sediments - Phosphorus (P) occurs in different chemical forms in soil and sediment, and they play different ecological and environmental roles. Thus, separation and...     

Measurement of phosphorus in the soil microbial biomass: Influence of plant material

The effect of plant material on measurement of P in the soil microbial biomass was evaluated using ³²P-labelled and unlabelled wheat plants. Fresh root and shoot material released significant amounts of P to 0.5 n NaHCO₃ (pH 8.5) following CHCl₃ fumigation. Treatment with CHCl₃ released 13–20% root P and 68–75% shoot P where a 16 h extraction period was used. With a 30 min extraction, release was 39% for roots and 18% for shoots. Calculations based on published values for rooting densities of field crops, show that significant errors in determination of soil biomass P are likely to occur where the CHCl₃ technique is used. Errors from inclusion of root material in the sample can be minimized by extending the extraction time from 30 min to 16 h.     

The effect of industrial aerial pollution on the composition of soil solutions in podzols

The composition of soil solutions is a sensitive indicator of the technogenic transformation of podzols of the Kola Peninsula under the impact of aerial pollution. The soil solutions have been obtained using Rhizon vacuum samplers. A sharp rise in the concentrations of heavy metals and sulfates is registered in the solutions from polluted soils. The leaching of organic substances, potassium, sodium, calcium, magnesium, manganese, and zinc from the litter horizons of polluted soils considerably increases. The ratios between the element concentrations in solutions from the litter horizons to those from the illuvial horizons become narrower, which suggests that the litter has partly lost its barrier function.     

Simultaneous fluometuron and norflurazon analysis in soil extracts and leachates

Abstract

Rapid, methanol‐extraction techniques for fluometuron (N, N‐dimethyl‐N'‐[3‐(trifluoromethyl) phenyl] urea) and norflurazon (4‐chloro‐5‐(methylamino)‐2‐(3‐(trifluoromethyl)phenyl)‐3(2(H)‐pyridazinone) from fortified soils have been reported to attain >90% recoveries. Analytical methods involving chromatographic separation coupled with fluorescence detection have also been described. The objectives of this study were to describe an analytical method for the simultaneous detection of fluometuron and norflurazon using ultraviolet spectro‐scopy in soil leachates and extracts and to examine the influence of residence time on herbicide recovery from fortified soil. The analytical method requires a gradient HPLC system, a reverse‐phase C‐18 column, and ultraviolet spectroscopy at a wavelength of 240 nm. The method is characterized by high reproducibility (spike recovery and diluted sample results are generally within 10% of the expected herbicide concentrations), low limits of detection (less than 1 (μg/L in soil leachates and 20 μg/L in soil extracts, depending on organic carbon content), and an applicable concentration range of more than two orders of magnitude. The recovery of fluometuron and norflurazon from fortified soils was significantly influenced by equilibration time, loading rate, and soil type (assuming zero chemical degradation). Most significantly, as herbicide contact time with the soil increased, recovery decreased. Thus, herbicide recoveries determined in the laboratory may not provide a true measure of herbicide recoveries from field soils.     

长期不施磷肥对旱地红壤养分比例与玉米产量的影响

在湖南祁阳国家红壤肥力与肥料效益长期监测基地,于2008年对已有18年旱地红壤肥料试验历史的不施肥、NK、NP、PK、NPK处理下玉米产量、pH以及养分状况等指标进行了研究.结果表明,长期不施磷肥、只施氮钾肥导致玉米绝产.施用磷肥有极显著的增产作用,其中NP、PK与NPK处理分别比不施肥处理玉米增产33.2%、66.39%与151.45%.施磷的增产作用主要体现在玉米穗粒数、百粒重以及公顷穗数的增加.长期施用氮肥造成了土壤酸化,尤以NK处理酸化严重(pH值降至4.1),导致玉米产量连年下降.长期不施磷肥、只施氮钾肥,导致土壤全磷量和有效磷量降低,而全氮、全钾、碱解氮、有效钾量增加,表现为土壤氮磷钾养分比例严重失衡.NK处理的土壤氮磷钾全量比例为2.8:1:44.5,其它施磷处理的为1.09～1.32:1:17.96～19.36;NK处理的土壤氮磷钾速效量为31:1:57,其它施磷处理的为0.7～1.16:1:1.07～4.6.     

Changes in soil solution composition and pH in urine-affected areas of pasture

Changes in soil solution composition and concentrations of exchangeable cations and mineral N in undisturbed cores of pasture soil were investigated in two experiments following applications of sheep urine to the cores. The major cations applied in the urine were K⁺ and Na⁺, and the major anions were HCO₃^? and Cl^?. Addition of urine increased concentrations of exchangeable K⁺, Na⁺ and NH₄⁺ and measured ionic strength of the soil solution throughout the surface 15 cm of soil, demonstrating that the urine moved through the core by macropore flow immediately following addition. Immediately following urine application the ionic strength in soil solution in the surface 2.5 cm of soil increased from 4–6 MM to 24–41 mM. Hydrolysis of urine-urea was extremely rapid, and in less than 1 d high concentrations of NH₄⁺-N (i.e. 270–370 mg N kg^?1) had accumulated in the surface 0–2.5 cm of the urine patch, and soil pH had risen by over one unit. Nitrification then proceeded and, after approximately 15 d, NO₃^? became the dominant form of mineral N present. During nitrification, soil pH declined and the ionic strength of the soil solution increased substantially with NO₃^? becoming the dominant anion present in solution. There were concomitant increases in the concentrations of Ca²⁺ and, to a lesser extent, Mg²⁺ in the soil solution as NO₃^? concentrations increased. After approximately 30 d, concentrations of exchangeable NO₃^? had risen to 250–330 mg N kg^?1, soil solution NO₃^? concentrations had increased to about 80 mmol, dm^?3, and ionic strength in the soil solution had increased to 130–140 mM. These results demonstrate the dominating effect of N transformations in causing large fluctuations in the pH, ionic composition and ionic strength of the soil solution in the urine patch. It was concluded that nutrient availability in the patch was affected directly by nutrient addition in urine, and also probably indirectly through the fluctuations in soil solution pH and ionic strength that occur.     

Extraction,molecular fractionation and enzyme degradation of organically associated phosphorus in soil solutions

The concentrations and chemical composition of water-extractable P were compared in four soil types from NE Scotland. All sites were sampled during the early establishment phase of a spring barley (Hordeum vulgare) crop. The quantity of total soluble P extracted ranged from <2.0 to 10 mg P kg soil^-1, of which up to 50% was classified as being organically associated. Sample fractionation showed that both orthophosphate inorganic P and organic P were associated with a wide molecular-size range of organic material. A strong positive correlation was readily apparent between P and the sum of Fe + Al in the fractionated samples. The extent of enzymatic hydrolysis of organic P varied between soil samples and the type of enzyme. Phytase consistently produced the greatest degree of hydrolysis.     

Tomato productivity and the associated composition of the hydroponic or soil solution

The concentration and balance of nutrients in both the hydroponic or soil solution has been evaluated with relevance to tomato productivity. Yields of 200 mt/ha have been produced in greenhouse, hydroponic culture in a 9 to 10 month period. Yields of more than 100 mt/ha of field grown tomatoes have been produced in Florida in a 4 to 5 month period. Within the limitations of either culture, it is possible per unit of time to provide the nutrients required to produce equivalent yields. It is most significant that field grown tomatoes in Florida can be grown with minimal management and at a fraction of the cost of those grown hydroponically. The validity of the Florida fresh market tomato industry is based on the production efficiency of the field culture. There are annually 16,000 ha of tomatoes grown in Florida, perhaps less than 40 ha grown in hydroponic cultures.