Transport of ammonium- and nitrate-nitrogen in surface runoff from pasture as influenced by urea application

Water, Air, & Soil Pollution - The effect of a surface application of urea on the transport of N in surface runoff from permanent pasture in New Zealand was investigated under natural rainfall...     

Plant availability of phosphorus in superphosphate and a phosphate rock as influenced by earthworms

The effect of earthworms on the plant availability of phosphorus (P) in superphosphate and Chatham Rise phosphorite (CRP) was evaluated in a glasshouse experiment using perennial ryegrass over seven harvests. A mixed earthworm population of Lumbricus rubellus (Hoff.) and Allolobophora caliginosa (Savigny) was used. Increases in the yield of ryegrass in the presence of earthworms varied from 2 to 32%, whereas increases in P uptake by ryegrass ranged from 0 to 40% over seven harvests. With superphosphate, the initial increases in both ryegrass yield and P uptake by ryegrass in the presence of earthworms ranged from 20 to 40% at first harvest to less than 10% by the seventh. In marked contrast, earthworms increased the agronomic performance of pelletized CRP by 15 to 30% throughout the trial period. An increase in plant-available soil N concentrations due to earthworm activity probably explains the initial difference in the performance of superphosphate. The increased agronomic effectiveness of CRP appears to result from the incorporation and intimate mixing of the PR with the soil by earthworms. The implications of the results obtained in the present study to the interpretation of glasshouse and field trials evaluating P fertilizers are also discussed.     

外源磷对土壤无机磷的影响及有效性

通过对我国具有代表性的几个典型土类15年长期定位试验的CK和NPK处理以及原始土壤中无机磷组分的分析，研究施磷肥对土壤无机磷形态的影响及有效性。结果表明，原始土壤中闭蓄态磷和Ca10-P占无机磷比例大，土壤磷有效性低；在不施外源磷条件下连续耕作，各个土类的无机磷总量均逐年减少，其中主要是Ca2-P、Al-P和Fe—P明显降低；长期施用磷肥提高了土壤无机磷总量（TIP）和各组分的含量，其中以Ca2-P、Al-P和Fe—P提高比例显著，而0-P和Ca10-P提高的比例少。说明累积在土壤中的肥料磷多以有效性较高的形态存在。     

Leaching of mineral nitrogen in the soil influenced by addition of compost and N-mineral fertilizer

This paper deals with the problem of mineral N leaching from arable lands due to the fertilization method. The influence of different doses of compost (50 and 100?Mg ha^?1) and N-mineral fertilizer (35-70-140 kg N ha^?1) on leaching of N_min in a lysimetric experiment with winter wheat. The area of our interest represents the main source of drinking water for the city of Brno and its neighborhoods. To demonstrate the effect of compost and mineral nitrogen addition, the lysimetric experiment was established there. Seven variants of the experiment with different fertilization schemes were studied during two vegetation seasons (2013 and 2014), each with three repetitions. The experiment was carried out in plastic experimental containers of 0.3 m diameter and 0.5 m height. Therefore, each lysimeter was the same size and was filled with 25 kg of subsoil and 25 kg of topsoil. The highest leaching of N_min was detected in the variant C2 where 140 kg N ha^?1 was applied, in both vegetation periods (5.97 kg N_min ha^?1 after the first vegetation period and 17.02 kg N_min ha^?1 after the second vegetation period). The positive effect of compost application (individually or in combination with the mineral N) on decrease in mineral N leaching was found during both vegetation period in comparison with variant C2. The highest doses of compost (100?Mg per ha) significantly decreased the concentration of mineral nitrogen in the soil eluate in both periods (3.03 kg N_min ha^?1 and 5.79 kg N_min ha^?1, respectively), by 197% and 293% in comparison with variant C2. There is evidence that the application of compost has a positive effect on the reduction of N_min leaching.     

Solubility of soil phosphorus as influenced by urea

The objective of this study was to investigate possible ways of mobilizing residual fertilizer P as a result of local pH elevation caused by urea hydrolysis. The response of water-soluble P (P_w) and dissolved organic C (DOC) to urea hydrolysis was monitored in three cultivated soils and at two P levels for up to 127–135 d and compared with corresponding changes in soils limed with Ca(OH)₂. Hydrolysis of urea was complete in 8–15d during which soil pH increased by 1–1.5 units at the maximum. Subsequently, the pH decreased to or below the original level owing to nitrification. Mobilization of soil P was enhanced substantially in parallel with the increase in pH, the peak P_w occurring simultaneously with the highest pH value. In all urea-treated soils, P_w remained at an elevated level for at least 60d. As compared to urea, elevation of soil pH with Ca(OH)₂ had only a minor and inconsistent influence on P_w. In mobilization of soil P, the urea-induced increase in pH and a simultaneous production of NH₄⁺ ions proved to be superior to liming with Ca(OH)₂. It was hypothesized that when an acid soil is amended with urea, phosphate is first displaced by OH^? ions, resulting in elevated solution P concentrations. A simultaneous dissolution of organic matter contributes to the persistence of high P concentration by competition for sorption sites on Fe and Al oxides, and thus retards the resorption of P.     

Infiltration rates, surface runoff, and soil loss as influenced by grazing pressure in the Ethiopian highlands

Abstract. The effect of grazing pressure on infiltration, runoff, and soil loss was studied on a natural pasture during the rainy season of 1995 in the Ethiopian highlands. The study was conducted at two sites with 0–4% and 4–8% slopes at the International Livestock Research Institute (ILRI) Debre Zeit research station, 50 km south of Addis Ababa. The grazing regimes were: light grazing stocked at 0.6 animal-unit-months (AUM)/ha; moderate grazing stocked at 1.8 AUM/ha; heavy grazing stocked at 3.0 AUM/ha; very heavy grazing stocked at 4.2 AUM/ha; very heavy grazing on ploughed soil stocked at 4.2 AUM/ha; and a control with no grazing. Heavy to very heavy grazing pressure significantly reduced biomass amounts, ground vegetative cover, increased surface runoff and soil loss, and reduced infiltrability of the soil. Reduction in infiltration rates was greater on soils which had been ploughed and exposed to very heavy trampling. It was observed that, for the same % vegetative cover, more soil loss occurred from plots on steep than gentle slopes, and that gentle slopes could withstand more grazing pressure without seriously affecting the ground biomass regeneration compared to steeper slopes. Thus, there is a need for developing 'slope-specific' grazing management schedules particularly in the highland ecozones rather than making blanket recommendations for all slopes. More research is needed to quantify annual biophysical changes in order to assess cumulative long-term effects of grazing and trampling on vegetation, soil, and hydrology of grazing lands. Modelling such effects is essential for land use planning in this fragile highland environment.     

低温胁迫下磷肥施用量对油橄榄生长发育的影响

  【目的】  探究自然低温胁迫下磷肥施用量对油橄榄幼苗生长发育的影响，旨在确定低温条件下增强油橄榄幼苗抗寒性及促进其生长发育的最适磷肥施用量，为油橄榄苗期养分管理提供科学依据。  【方法】  本试验选用我国油橄榄主栽品种‘鄂植8号’为试验材料，所用磷肥为磷酸二氢钠 (NaH₂PO₄·2H₂O)，6个处理的每株幼苗P₂O₅施用量分别设为0、15、30、45、60和75 g，记作P0、P15、P30、P45、P60 和 P75；低温胁迫是在自然条件下，取样时间为2018年9月16日、11月15日和12月30日上午9:00左右，取样当日与前两日平均气温分别为17.6℃、3.1℃和–5.3℃，采集样品为植株叶片、根系，分析油橄榄幼苗叶片冻害指数、渗透调节物质含量、膜伤害指标、抗氧化酶活性、叶绿素含量、磷含量及根系活力、根系形态和生物量积累。  【结果】  在低温环境 (3.1℃、–5.3℃) 下，增施适量磷肥可降低油橄榄叶片冻害指数，增加叶片中脯氨酸 (Pro)、可溶性蛋白 (SP)、可溶性糖 (SS)、叶绿素和磷含量，增强叶片抗氧化酶活性，降低叶片膜透性、超氧阴离子产生速率和丙二醛 (MDA) 含量，增强根系活力。在3.1℃条件下，P45处理油橄榄叶片超氧化物歧化酶 (SOD)、过氧化氢酶 (CAT) 与抗坏血酸过氧化物酶 (APX) 活性较P0分别增加了104.75%、95.02%和100.01%；叶绿素含量和磷含量较P0分别增长了114.83%和33.66%。在低温条件下，油橄榄幼苗根系和地上部生长均受到抑制，P45处理的油橄榄总根长、根表面积、根体积和根尖数较P0处理增加了42.60%、28.79%、55.50%和25.01%，各磷肥处理下根系平均直径间差异不显著；株高、根干重、地上部干重较P0处理分别增加了48.48%、80.27%和34.51%。  【结论】  低温抑制油橄榄幼苗生长发育，而适量增施磷肥可有效提高油橄榄的生理活性，进而缓解低温对油橄榄幼苗的损伤，增强了植株的抗寒性。低温胁迫条件下，每株施用45 g磷肥 (P₂O₅)的效果最佳。     

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。     

Zinc desorption kinetics as influenced by pH and phosphorus in soils

Abstract

The rate of zinc (Zn) desorption from soil surfaces into soil solution is a dynamic factor that regulates its continuous supply to growing plants. To ascertain the pattern of Zn desorption as a function of phosphorus (P) application rate and pH, kinetics of Zn desorption from three surface soils representative of three major benchmark soil series were investigated using four equations. Zinc desorption decreased continuously with increase in pH from 4.25 to 8.00 in Oxisol. By contrast, Alfisol and Vertisol exhibited maximum Zn desorption at pH 5.50. Thereafter, Zn desorption decreased abruptly at pH 6.75 and finally steady state condition was obtained in both sodium chloride (NaCl) and calcium chloride (CaCl₂) medium. The Elovich equation described Zn desorption kinetics much better at pH 4.25 and 5.50 followed by Parabolic diffusion equation at pH 6.75 and 8.00 for all the soils in NaCl medium. Whereas in the CaCl₂ medium, the Elovich equation was superior in fitting the Zn desorption data irrespective of P level, pH, and soil. The Elovich constant (β) indicated that P affects Zn desorption inversely up to pH values 6.75.     

不同磷源对设施菜田土壤速效磷及其淋溶阈值的影响

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

Phosphorus fertilizer requirements as estimated by phosphate sorption

Abstract

Twenty‐nine soil samples representing 12 soil series and varying levels of P fertility were obtained from cooperating agricultural experiment stations in the southern U.S. Fertilizer P requirements were estimated from P sorption curves and correlated with P requirements established by field experiments. Estimated and measured P requirements were highly correlated (r =0.93**) with the quantitative relationship being nearly 1:1. With one exception, P sorption also accurately estimated needs of fertilized soils; in that one case, fertilizer needs were estimated at 45 kg P/ha although there was no response to P in the field.

The quantity of sorbed P in equilibrium with 0.02 μg P/ml apparently was a good estimate of fertilizer P requirement. The value 0.02 was somewhat lower than has been reported from other research; this lower value may be associated with somewhat lower yields, warm soil temperatures, and relatively long growing season in the southern U.S.A. It also may have been caused by under‐evaluating the effectiveness of residual fertilizer P or by a more stable P concentration in soil solution for soils receiving long‐term applications of fertilizer P.     

Economics of phosphorus fertilization of barley as influenced by concentration of extractable phosphorus in soil

Abstract

Field experiments were conducted at 60 sites in central and north‐central Alberta to determine the yield response of barley (Hordeum vulgare L.) to phosphorus (P) fertilizer and economics of P application on soils with different concentrations of extractable P in the 0–15 cm soil layer. On the unfertilized plots, barley yield increased with increasing concentration of extractable P in the soil up to 22 mg P kg^‐1, but the yield response to applied P decreased. The net present value (NPV) of returns from P fertilization increased with increasing rate of P up to approximately 51 kg P₂O₅ ha^‐1. The NPV of applied P decreased with increasing concentration of extractable P in soil. On soils with extractable P more than 22 mg P kg^‐1, P application did not result in positive NPV.     

Increasing phosphorus fertilizer value of recycled iron phosphates by prolonged flooding and organic matter addition

Iron (Fe) minerals are commonly used to remove phosphorus (P) from waste streams, producing P-loaded Fe(III) oxides or Fe(II) phosphate minerals (e.g., vivianite). These minerals may be used as fertilizers to enhance P circularity if solubilized in soil. Here, we tested the P fertilizer value of recycled Fe phosphates (FePs) in a pot trial and in an incubation experiment, hypothesizing that P release from FePs is possible under Fe(III)-reducing conditions. First, a pot trial was set up with rice (Oryza sativa) in all combinations of soil flooding or not, three P-deficient soils (acid, neutral, and calcareous), and six FePs (three Fe(III)Ps and three Fe(II)Ps) referenced to triple superphosphate (TSP) or zero amendments. Shoot P uptake responded to TSP application in all treatments but only marginally to FePs. The redox potential did not decrease to -200 mV by flooding for a brief period (13 d) during the pot trial. A longer incubation experiment (60 d) was performed, including a treatment of glutamate addition to stimulate reductive conditions, and P availability was assessed with CaCl₂ extraction of soils. Glutamate addition and/or longer incubation lowered soil redox potential to < -100 mV. On the longer term, Fe(III) minerals released P, and adequate P was reached in the calcareous soil and in the neutral soil amended with Fe(III)P-sludge. It can be concluded that prolonged soil flooding and organic matter addition can enhance the P fertilizer efficiency of FePs. Additionally, application of FeP in powder form may enhance P availability.     

Arsenic biogeochemistry as affected by phosphorus fertilizer addition,redox potential and pH in a west Bengal (India) soil

This laboratory experiment systematically examines arsenic, iron, and phosphorus solubilities in soil suspensions as affected by addition of phosphorus fertilizer under different redox potential (Eh) and pH conditions. Under aerobic conditions, As solubility was low, however, under moderately reducing conditions (0, − 150 mV), As solubility significantly increased due to dissolution of iron oxy-hydroxides. Upon reduction to − 250 mV, As solubility was controlled by the formation of insoluble sulfides, and as a result soluble As contents significantly decreased. Soluble Fe concentration increased from moderate to highly anaerobic conditions; however, it decreased under aerobic conditions likely due to formation of insoluble oxy-hydroxides. A low pH, 5.5, led to increased soluble concentrations of As, Fe, and P. Finally, addition of P-fertilizers resulted in higher soluble P and As, even though the concentration of As did not increased after an addition rate of 600 mg P kg^− 1 soil.     

Potassium and magnesium uptake by wheat and soybean roots as influenced by fertilizer rate

Abstract

Greenhouse‐pot experiments were conducted to compare wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merrill] in terms of their potassium (K) and magnesium (Mg) uptake. Previously, a field study indicated that various rates of K and Mg fertilization did not produce a significant wheat‐yield response. However, a yield increase with residual K and Mg was measured for the subsequent soybean crop. The 0 to 15 cm layer of Norfolk loamy fine sand (fine loamy, siliceous, thermic Typic Kandiudult) from two different sites was used for the pot experiments. Soil from both sites had a pH of 5.1. Potassium as potassium sulfate (K₂SO₄) was mixed into the soil from the K‐deficient site and Mg as magnesium sulfate (MgSO₄) was mixed into the soil from the Mg‐deficient site. ‘Florida 301’ wheat and ‘Cobb’ soybean were grown in winter and summer, respectively.

Soybean and wheat were similar in K uptake/g of roots on the first and second sampling dates. However, by the third sampling date, K uptake/g of wheat roots was about twice as high as for soybean. Potassium uptake/cm of soybean roots was two to five times that of wheat at each sampling date. Magnesium uptake/g of soybean roots was about four to five times as high as wheat on each sampling date. Similarly, Mg uptake/cm of soybean roots was 10 to 30 times higher than for wheat. Soybean showed higher total K and Mg content than wheat, suggesting that soybean has a higher demand for both K and Mg. The higher demand for K and Mg by soybeans than by wheat suggests that wheat could meet its demand for K and Mg at much lower soil levels than that for soybean. This would also explain a grain‐yield response to K and Mg by soybeans in the previously reported field study, despite a lack of yield response by wheat grown on the same site.     

炭基磷肥对黑土和红壤磷素有效性及形态变化的影响

为探究炭基磷肥作为磷源对土壤磷素有效性及形态变化的影响,采用土壤培养试验,将牛粪生物质炭(BC)、重过磷酸钙(TSP)、不同方式制备的炭基磷肥(TSP-1和TSP-2)添加到黑土(高磷)和红壤(低磷)中培养70d,并作空白对照(CK)。研究结果表明,BC处理对黑土和红壤磷素有效性影响很小,但呈现上升的趋势;TSP、TSP-1和TSP-2处理显著增加了黑土和红壤的全磷和有效磷含量。黑土培养前期(0～28d),TSP、TSP-1和TSP-2处理的土壤有效磷含量分别下降了42.21%、16.81%和29.93%,培养中后期(28～70d),TSP-1和TSP-2处理的土壤有效磷含量平均分别比TSP处理高9.47%和9.81%;红壤培养前期(0～28d),TSP、TSP-1和TSP-2处理的土壤有效磷含量分别下降了78.31%、24.64%和57.53%,培养中后期(28～70d),TSP-1和TSP-2处理的土壤有效磷含量平均分别比TSP处理高129.23%和53.10%。BC处理增加了黑土HCl-P的含量及红壤NaOH-P、HCl-P的含量;TSP、TSP-1和TSP-2处理显著增加了黑土和红壤Water-P和NaHCO3-P的含量,对其他磷组分(NaOH-P、HCl-P、Residual-P)也有影响。BC、TSP-1和TSP-2处理显著提高了黑土和红壤的pH值,TSP处理降低了黑土的pH值,对红壤的pH值影响较小。综上所述,相比无机磷肥,以炭基磷肥作为磷源可以减缓磷素在黑土和红壤中的释放速率,避免磷素被土壤大量固定,并影响土壤磷素形态的分布,提高磷肥在土壤中的有效利用率,尤其在红壤中作用效果更为明显。     

N2O emissions from an irrigated and non‐irrigated organic soil in eastern Canada as influenced by N fertilizer addition

Drainage and cultivation of organic soils often result in large nitrous oxide (N₂O) emissions. The objective of this study was to assess the impacts of nitrogen (N) fertilizer on N₂O emissions from a cultivated organic soil located south of Montréal, QC, Canada, drained in 1930 and used since then for vegetable production. Fluxes of N₂O were measured weekly from May 2004 to November 2005 when snow cover was absent in irrigated and non‐irrigated plots receiving 0, 100 or 150 kg N ha⁻¹ as NH₄NO₃. Soil mineral N content, gas concentrations, temperature, water table height and water content were also measured to help explain variations in N₂O emissions. Annual emissions during the experiment were large, ranging from 3.6 to 40.2 kg N₂O‐N ha⁻¹ year⁻¹. The N₂O emissions were decreased by N fertilizer addition in the non‐irrigated site but not in the irrigated site. The absence of a positive influence of soil mineral N content on N₂O emissions was probably in part because up to 571 kg N ha⁻¹ were mineralized during the snow‐free season. Emissions of N₂O were positively correlated to soil CO₂ emissions and to variables associated with the extent of soil aeration such as soil oxygen concentration, precipitation and soil water table height, thereby indicating that soil moisture/aeration and carbon bioavailability were the main controls of N₂O emission. The large N₂O emissions observed in this study indicate that drained cultivated organic soils in eastern Canada have a potential for N₂O‐N losses similar to, or greater than, organic soils located in northern Europe.     

Cadmium adsorption as influenced by poultry manure addition in soils of South-Western Nigeria

Soil contamination with heavy metals is of great concern worldwide because of its negative effects on human health and environment. The objective of this study was to evaluate the influence of poultry manure on cadmium (Cd) adsorption characteristics in soils from ten different land uses and to determine the effects of Cd adsorption on soil properties. Laboratory experiments were carried out using Cd concentrations ranging from 0 to 160 mg Cd L^?1 and poultry manure rates ranging from 0 to 8% w/w basis. Results showed that all the soils exhibited varying capacity to adsorb Cd with values ranging from 28.78 to 130.2 mgkg^?1; 126.2 to 153.5 mgkg^?1 and 126.2 to 156.1 mgkg^?1 for 0%, 4% and 8% poultry manure at 160 mgkg^?1 initial Cd concentrations, respectively. Lowest Cd adsorbed (28.78 mgkg^?1) was recorded in samples from 6 months fallow and highest (156.1 mgkg^?1) from vegetable field. On the average, capacity to adsorb Cd was 72.1%, 99.7% and 95.3% with 0%, 4% and 8% applied poultry manure, respectively. Organic carbon, CEC, pH were significantly correlated with Cd adsorption. Poultry manure use will increase Cd adsorption and decrease Cd in the environment.     

Changes in some soil phosphorus availability parameters as induced by phosphorus addition and soil sorption properties

Abstract

Changes in agronomic and environmental soil phosphorus (P) availability parameters, i.e., Mehlich‐ and Olsen‐extractable P, reversibly‐adsorbed P, soil‐solution P, and equilibrium‐P concentration were determined following equilibration of 13 Italian soils with five rates of P application (0, 12.5, 25, 50, and 100 mg P kg^‐1 soil). Soil P availability as determined by each parameter increased with added P. The relative change in soil P availability with added P was a function of soil sorption index silicon (SI), according to the equation DP=(P_added)^a*exp(b+g*SI). This equation accounted for 94 to 98% of the variance in soil‐P availability. The inclusion of SI in a soil testing program may increase the reliability in assessing both soil‐P fertilizer requirements and the vulnerability of a soil to P loss in runoff following land application of fertilizer or manure P.     

磷肥和有机肥对不同磷水平土壤磷吸附-解吸的影响

采用培养试验结合Langmuir吸附等温方程进行拟合求出吸附、解吸的相关参数的方法,研究了磷肥和有机肥对不同磷水平土壤磷吸附和解吸特性的影响。结果表明,随土壤磷水平和磷肥和有机肥用量的增加,土壤最大吸磷量、土壤磷最大缓冲能力显著降低;土壤易解吸磷和土壤磷的解吸率显著增加。土壤易解吸磷和土壤磷的解吸率与土壤Olsen-P呈显著正相关;土壤最大吸磷量、土壤磷最大缓冲容量与土壤Olsen-P呈显著负相关。单位量磷肥所增加的土壤易解吸磷随着磷肥用量和土壤磷水平的增加而增大;土壤磷水平和磷用量是影响土壤磷最大吸磷量和土壤磷最大缓冲能力的重要因素。