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1.
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 (Pw) 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 Pw occurring simultaneously with the highest pH value. In all urea-treated soils, Pw 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 Pw. 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. 相似文献
2.
《Communications in Soil Science and Plant Analysis》2012,43(21):2700-2714
ABSTRACTSoil compaction interferes in soil nutrient transport and root growth. The aim of this work was to evaluate eucalypt growth and phosphorus (P) nutritional efficiency as affected by soil compaction and P rates. The treatments were composed of a 3 × 4 factorial scheme (soil bulk densities levels versus P fertilization rates) for two weathered tropical soils, a clayey Ferralsol (FClayey) and a sandy Ferralsol (FSandy). The soil bulk densities assessed were 0.90, 1.10 and 1.30 g cm?3 for FClayey, and 1.35, 1.55 and 1.75 g cm?3 for FSandy. The P rates were 0, 150, 300 and 600 mg kg?1 for FClayey, and 0, 100, 200 and 400 mg kg?1 for FSandy. Soil compaction reduced root growth, P content in the plant, P utilization efficiency and P recovery efficiency; and increased average root diameter. Phosphorus fertilization increased root length density, root surface area, dry matter, P content in the plant, P utilization efficiency and P uptake efficiency; and decreased P recovery efficiency. It was concluded that P fertilization is not effective to offset the deleterious effects of soil compaction on eucalypt growth and nutrition.Abbreviations: FClayey: clayey Ferralsol; FSandy: sandy Ferralsol; RDens: root length density; RDiam: root diameter; RSurf: root surface area; RDM: root dry matter; SDM: shoot dry matter; WPDM: whole-plant dry matter; RP: root P content; SP: shoot P content; WPP: whole-plant P content; PUtE: P utilization efficiency; PUpE: P uptake efficiency; PRE: P recovery efficiency. 相似文献
3.
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. 相似文献
4.
Demis Fikre Limeneh Hussien Mohammed Beshir Fekadu Gebretensay Mengistu 《Journal of plant nutrition》2020,43(9):1229-1247
AbstractThe experiment was conducted at Kulumsa, South East Ethiopia, using four levels of nitrogen (N) (0, 50,100 and 150?kg N ha?1) and four levels of phosphorus (P) (0, 35, 70 and 105?kg P2O5 ha?1) fertilizers arranged in 4?×?4 factorial arrangements in randomized complete block design with three replications. The available P was increased after harvest due to the application of N and P fertilizer at the rates of 100 or 150?kg N ha?1 and 70 or 105?kg P2O5 ha?1. More specifically, nutrients concentration and nutrient uptake were significantly (p?<?.01) varied among treatment combinations and nutrient use efficiency was declined by increasing N and P after optimum rates. The higher physiological efficiency of N (53.47?kg kg?1) and P (580.41?kg kg?1) and the highest apparent recovery of N (19.62%) and P (2.47%) was recorded from application of 50?kg N ha?1 and P at 70?kg P2O5 ha?1 and the highest agronomic efficiency of N (10.78?kg kg?1) and P (15.25?kg kg?1) was recorded from N at the rate of 50?kg N ha?1 and P at 35?kg P2O5 ha?1, respectively. The combination of N at 100?kg N ha?1 and P at 70?kg P2O5 ha?1 was promising combination that generated highest net benefit 488,878.5 ETB (Ethiopian birr) ha?1 with the highest marginal rate of return (36638%) and gave the highest seed yield (1858.82?kg ha?1) with yield increment of about 57.72% over the control. 相似文献
5.
Sven Fischer Heinz-Josef Koch Klaus Bürcky 《Archives of Agronomy and Soil Science》2013,59(6):725-736
The benefits of liming acidic or calcium (Ca)-deficient soils for soil structure and fertility are well documented. However, little is known about the effect of liming nearly neutral loess soils – lacking Ca – on interactions between soil nutrients. Over a 2-year period, 62 field trials were conducted in Germany and Austria with three treatments (0, 3 and 12 t CaO ha?1) on slightly acidic loess soils. Soil samples from the top soil layer were taken 4, 8, 16 and 24 weeks after liming. In addition to the pHCaCl2, the phosphorus (P), potassium (K) and Ca contents were analysed using electro-ultrafiltration (EUF). The application of lime increased the pH in average from 6.6 up to 7.0 and 7.2, but did not decrease EUF extractable P and K below the level of untreated control. Contrary to our expectations, EUF extractable P increased 4 weeks after liming in the treatment with 3 t CaO ha?1. At the end of incubation period, 24 weeks after liming, the EUF extractable K in treatment 12 t CaO ha?1 remained still 1.3 mg K 100 g?1 soil above the untreated control. 相似文献
6.
外源磷对土壤无机磷的影响及有效性 总被引:5,自引:0,他引:5
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。 相似文献
7.
M. C. S. Carvalho 《Journal of plant nutrition》2016,39(6):781-792
The root is an important organ which supplies water and nutrients to growing plants. Data related to root growth and nutrient uptake by tropical legume cover crops are limited. The objective of this study was to evaluate root growth of tropical legume cover crops and nutrient uptake and use efficiency under different phosphorus (P) levels. The P levels used were 0 (low), 100 (medium) and 200 (high) mg kg?1 of soil and 5 cover crops were evaluated. Root dry weight, maximum root length, specific root length were significantly influenced by P and cover crop treatments. Maximum values of these root growth parameters were achieved with the addition of 100 mg P kg?1 soil. The P X cover crops interaction for all the macro and micronutrients, except manganese (Mn) was significant, indicating variation in uptake pattern of these nutrients by cover crops with the variation in P rates. Overall, uptake pattern of macronutrients was in the order of nitrogen>calcium>potassium>magnesium>phosphorus (N > Ca > K > Mg > P) and micronutrient uptake pattern was in the order of iron>manganese>zinc>copper (Fe > Mn > Zn > Cu). Cover crops which produced maximum root dry weight also accumulated higher amount of nutrients, including N compared to cover crops which produced lower root dry weight. Higher uptake of N compared to other nutrients by cover crops indicated that use of cover crops in the cropping systems can reduce loss of nitrate (NO3?) from soil-plant systems. Increase in root length and root dry weight with the addition of P can improve nutrient uptake from the soil and less loss of macro and micronutrients from the soil-plant systems. 相似文献
8.
《Communications in Soil Science and Plant Analysis》2012,43(4):281-287
Abstract Twenty surface soil samples, representing two major soil orders alfisols and vertisols were extracted with 0.01N Na2 EDTA solution (pH 4.8) at a soil/solution ratio of 1:25. Phosphorus in the extract was determined following ammonium molybdate‐stannous chloride colorimetric method. The EDTA extractable P showed significant positive correlations with extractable P according to the Olsen, Morgan, Bray 1 and 2 and also with inorganic phosphorus fractions associated with Al, Ca and Fe. 相似文献
9.
The effects of long-term (19 years) different land use and fertilization on activity and composition of ammonia-oxidizing bacteria (AOB) in an aquic brown soil were investigated in a field experiment in Liaoning Province, China. The 19-year experiment conducted from 1990 to 2008 involved seven treatments designed: cropping rotation of soybean-corn-corn with no fertilizer (control, CK), recycled manure (RM), fertilizer nitrogen (N), phosphorous (P) and potassium (K) (NPK), NPK+RM, and no-crop bare land, mowed fallow, and non-mowed fallow. The results showed that the potential nitrification rates of the RM, NPK+RM, mowed fallow, and non-mowed fallow treatments were significantly higher (P < 0.05) than those of the CK and NPK treatments, indicating that the long-term applications of recycled manure and return of plant residues both significantly increased the activity of AOB. Although the application of NPK did not enhance soil potential nitrification because of decreased pH, available K had an important effect on potential nitrification. Denaturing gradient gel electrophoresis (DGGE) fingerprint profiles showed that no-crop treatments had an increase in the diversity of the AOB community compared to the CK, RM, and NPK treatments, implying that agricultural practices, especially tillage, had an adverse effect on the soil AOB community. The NPK+RM treatment had the most diverse DGGE patterns possibly because of the increased available P in this treatment. A phylogenetic analysis showed that most of the DGGE bands derived belonged to Nitrosospira cluster 3, not Nitrosospira cluster 2. These demonstrated that different land use and fertilization significantly influenced the activity and composition of the AOB community by altering the soil properties, mainly including pH, total C, available K, and available P. 相似文献
10.
《Communications in Soil Science and Plant Analysis》2012,43(1-2):145-153
Abstract Physical characteristics of corn (Zea mays L.) kernels influence end‐use. Agronomic practices including nitrogen (N) fertilization may influence kernel hardness. The objective of this study was to determine if com endosperm characteristics influence the effect of N fertilization on kernel hardness and breakage susceptibility. In 1988, six corn hybrids differing for endosperm were grown at two locations in Ohio and with two N rates (34 and 200 kg/ha). Kernels of the waxy hybrid were denser less susceptible to breakage than its near‐isogeneic normal counterpart. Soft kernels weighted less and were less dense than hard kernels, but these two hybrid classifications did not differ for breakage susceptibility. Hard kernels possessed a greater resistance to grinding than soft kernels. Increasing N fertilizer rate increased resistance to grinding and reduced susceptibility to breakage of both soft and hard endosperm types. Fertilization with N not only affects corn grain yield, but also affects physical characteristics that are important to end‐users. 相似文献
11.
A. R. Dexter E. A. Czyż J. Niedzwiecki C. Maćkowiak 《Archives of Agronomy and Soil Science》2013,59(1-2):123-133
Measurements are reported of soil organic carbon content, dry bulk density, water retention characteristics, and saturated hydraulic conductivity of a sandy loam soil with two different crop rotations and two levels of fertilization. The water retention characteristics were fitted to the van Genuchten equation. Values of unsaturated hydraulic conductivity were estimated by calculation. It was found that crop rotation has much larger effects on these soil physical properties than fertilization. Water retention and hydraulic conductivity are greater when mustard, and clover with grass are included in the crop rotation, but only at water contents greater than 0,10 and 0, 13 kg kg?1respectívely. 相似文献
12.
【目的】研究红壤性水稻土长期不同施肥模式下耕层土壤有效磷含量与全磷含量的变化特征,以及有效磷含量与累积磷盈亏的关系,分析不同形态磷肥对土壤磷素有效性影响的差异,找出最有效的红壤性水稻土磷素培肥施肥方式。【方法】供试土壤取自1981~2012年在江西进行的红壤双季稻稻田长期定位试验。试验自始至终保持水分、农药等日常田间管理与当地习惯相同,统一水稻品种并定期更换。试验设5个处理:施氮钾肥(NK);氮磷钾化肥(NPK);两倍氮磷钾化肥(NPK2);早稻氮磷钾化肥配施紫云英,晚稻氮磷钾化肥配施猪粪(NPKM);长期不施肥(CK)。分析了耕层土壤有效磷含量和全磷含量计算了有效磷增量与累积磷盈亏的相互关系。【结果】试验32年后对照土壤磷年均亏缺22.7 kg/hm2,有效磷含量在低水平下维持平衡;NK处理磷素年均亏缺27.9kg/hm2,显著高于不施肥处理,全磷含量缓慢降低32年累计降低了8.6%,有效磷含量呈持平趋势。NPK、NPK2、NPKM处理土壤磷素均有盈余,年均盈余量分别为33.3、39.0、41.0 kg/hm~2,全磷含量分别增加了32.1%、89.4%、165.1%,有效磷含量分别增加了2.2、6.9、15.3倍,年上升速率分别为0.30、1.18、1.79 mg/kg,有效磷增量与累积磷盈余呈显著正相关。NPK化肥配施有机肥处理不仅提高土壤有效磷及全磷的含量,还显著提高磷素有效性。水稻产量增加量随累积磷投入量和有效磷的增加而增加,前期增加较快后期增加较慢,有效磷含量具有明显的拐点,其值超过20 mg/kg后产量就增加缓慢。【结论】红壤性水稻土在双季稻种植模式下,长期不施磷肥处理土壤全磷含量缓慢降低,有效磷含量可维持低水平下的平衡。施磷处理土壤全磷含量,有效磷含量以及磷素有效性均呈上升趋势且无机磷肥与有机磷肥配施处理上升最快。无机磷肥与有机磷肥配合施用在提高土壤全磷含量的同时也提高磷素的有效性。土壤有效磷超过20 mg/kg后相对产量提高缓慢。氮磷钾化肥与有机肥配合施用是提高耕层土壤磷素库容和提高磷素活化能力的有效措施。 相似文献
13.
N. K. Fageria 《Journal of plant nutrition》2016,39(4):562-568
Phosphorus (P) deficiency is one of the most yield limiting factors for dry bean (Phaseolus vulgaris) production in tropical acid soils. Dry beans are invariably grown as mono-crops or as inter-crops under the perennial tropical crops. Information is limited regarding the influence of phosphorus fertilization on dry bean yield and yield components and P use efficiency in tropical acid soils. A greenhouse experiment was conducted to evaluate the influence of phosphorus fertilization on dry bean growth, yield and yield components and P uptake parameters. Phosphorus rates used were 0, 50, 100, 150, 200, and 250 mg P kg?1 of soil. Soil used in the experiment was an acidic Inceptisol. Grain yield, shoot dry weight, number of pods, and 100 grain weight were significantly (P < 0.01) increased with phosphorus fertilization. Maximum grain yield, shoot dry matter, number of pods, and 100 grain weight were obtained with the application of 165, 216, 162, and 160 mg P kg?1 of soil, respectively, as calculated by regression equations. Grain yield was significantly and positively associated with shoot dry weight, number of pods, P concentration in grain and total uptake of P in shoot and grain. Phosphorus use efficiency defined in several ways, decreased with increasing P rates from 50 to 250 mg P kg?1 of soil. Maximum grain yield was obtained at 82 mg kg?1 of Mehlich 1 extractable soil P. Results suggest that dry bean yield in Brazilian Inceptisols could be significantly increased with the use of adequate rates of phosphorus fertilization. 相似文献
14.
长期不同施肥下潮土磷素的演变特征 总被引:1,自引:5,他引:1
【目的】研究在施磷量相等的条件下长期施用有机肥和化肥对潮土全磷、有效磷的演变的影响,为潮土地区农业生产和地力培育提供理论依据。【方法】以河南封丘的肥料长期定位试验(开始于1989年)为平台试验设置7个处理,即有机肥(OM)、1/2有机肥+1/2化肥(1/20M)、氮磷钾(NPK)、氮磷(NP)、磷钾(PK)、氮钾(NK)和不施肥处理(CK)分析比较了不同处理土壤的全磷、有效磷含量及两者比值的演变规律。【结果】所有施磷处理土壤全磷均与试验年份呈显著线性相关,1/2有机肥+1/2化肥、有机肥和氮磷钾处理土壤全磷年均增加量为0.0083、0.0081和0.011 g/kg;各处理2008~2010年3年平均土壤有效磷含量大小顺序为PKOM1/20MNPKNPCKNK施磷处理下试验进行的前11年土壤有效磷快速增加,以后达到稳定状态;有机肥处理和1/2有机肥+1/2化肥处理土壤有效磷与全磷的比值显著高于氮磷钾处理,试验20年后有机肥处理和1/2有机肥+1/2化肥处理有效磷/全磷是氮磷钾处理的1.9和1.4倍。磷素平衡与全磷及有效磷含量均达到了极显著相关相关系数分别为0.981和0.886。磷素盈亏每增加100 kg/hm2土壤全磷含量增加0.04 g/kg土壤有效磷含量增加约为2 mg/kg。试验20年后其他理化性质与土壤全磷、有效磷含量之间的相关关系均未达到显著水平。但土壤有机质和土壤全氮与有效磷/全磷的相关系数达到了显著水平,说明土壤有机质和全氮含量提高有利于土壤磷素的活化。【结论】土壤全磷和有效磷的演变都显著受磷素盈亏的影响。在每年P_2O_5投入量相当于135 kg/hm~2时施用化肥更加有利于潮土全磷含量的提高;经过21年的不同施肥处理,平衡施用化肥处理有效磷含量只能维持在7 mg/kg左右这一水平处于中低水平,依旧需要磷的投入才能维持作物的高产。施用有机肥可以在不增加施磷量的条件下增加作物可吸收利用的磷。因此减少施磷量增施有机肥可能成为潮土地区减肥增效的重要手段。 相似文献
15.
《Communications in Soil Science and Plant Analysis》2012,43(13-14):1951-1962
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. 相似文献
16.
17.
Carbon mineralization kinetics as influenced by soil properties 总被引:3,自引:0,他引:3
In a short-term laboratory study C mineralization potentials were determined on soil samples obtained from some representative agricultural soils in Tuscany, Italy. All the kinetic models tested to describe the mineralization process provided a good fit to the experimental data. A modified first-order model best described C mineralization in the soil. Both potentially mineralizable C and the mineralization rate (k) varied considerably among soils, reflecting the differences in soil properties. Potentially mineralizable C was positively related to C evolved as CO2 and to the exchange capacity. Normalized values (potentially mineralizable C divided by organic C), representing on average about 2% of the total soil C, was positively correlated to soil pH and negatively to the soil C pool, the soil N pool, and total microbial activity. Values for k ranged between 0.050 and 0.104 day-1, being higher in fine-textured soils and in soils with a large free Fe content. A low C:N ratio was indicative of a high k value. Turnover times for mineralized C were relatively rapid, ranging from 10 to 20 days. 相似文献
18.
R. Riffaldi A. Saviozzi R. Cardelli S. Cipolli R. Levi-Minzi 《Biology and Fertility of Soils》2006,43(2):209-214
A 10-week laboratory study, using an open incubation technique, was carried out to determine net sulphur (S) mineralization potentials of soil samples obtained from some representative soils in Tuscany, Italy. The time-course of organic S mineralization in the soils was analyzed by fitting the experimental values to three kinetic models (first-order, first-order E, zero-order). The first-order model was found to be the most suitable because it provided the best fit to the experimental data and for its simplicity. Potentially mineralized S (S
0) values ranged from a minimum of 13.6 to a maximum of 50.7 mg kg−1 soil and the mineralization rate k varied from 0.111 to 0.615 week−1. It was also positively related to organic C, N, and S, protease, arylsulphatase, and dehydrogenase activities. The mineralization rate did not show any significant relationship with soil properties. 相似文献
19.
Changwen Du Mingjiang Lei Jianmin Zhou Huoyan Wang Xiaoqin Chen Yuhua Yang 《植物养料与土壤学杂志》2011,174(1):20-27
Improved information on water‐extractable soil P (Pw) and its distribution in various forms is needed to assess its bioavailability and environmental impact. This study investigated Pw in a fluvo‐aquic soil solution in relation to the continuous application of inorganic fertilizer (NPK) and wheat straw–soybean‐based compost for 15 y. Phosphatase‐hydrolysis techniques were used to fractionate organic P (Po) in water extracts of soil into phosphomonoester (Pom) and phosphodiester (Pod). In comparison with the noncomposted treatments, compost application significantly increased the levels of inorganic P (Pi) and Po. Pom was the main form in water‐extractable soil Po (71%–88%), in which sugar phosphate (Pos) occupied 48%–75%, inositol hexakisphosphate (Pop) comprised 13%–23%, and Pod only accounted for a small percentage (11%–26%). Long‐term compost application significantly increased the content of Pom, Pos, and Pod, but decreased the Pop content; the ratio of Pom to Po increased significantly in compost‐treated soil, but the ratio of Pop to Po and Pod to Po significantly decreased. Thus, the equilibrium of phosphatase involved P transformations shifted to Pi in compost‐treated soil. The phosphomonoesterase and phosphodiesterase activities were significantly higher in compost‐treated soil, which favored the transformations of Pod into Pom and Pom into Pi. The ratio of Po to Pw in water extracts of compost‐treated soil was similar to that of control soils with no fertilizer input (CK), but was significantly lower than in NPK treatment, which demonstrated that a larger increase occurred for soil Pi in water extracts of compost‐treated soil. Long‐term compost application in the fluvo‐aquic soil changed the composition of Pw, promoted the rate of P transformations in soil solution, and significantly increased soil P bioavailability. 相似文献
20.
Effects of long-term phosphorus fertilization and winter cover cropping on soil phosphorus transformations in less weathered soil 总被引:3,自引:0,他引:3
Information concerning sources and sinks of available P in soil is needed to improve soil P management and protect water quality. This study, conducted from 1989 to 1998 on a Sultan silt loam soil (Aquantic Xerochrept), determined the annual P removal rate by corn (Zea mays L.) and P transformation as affected by P rate and winter cover cropping. Treatments included two P rates (0 and 44 kg P ha–1) applied to corn at planting each year. All cover crops received 19.6 kg P ha–1 at seeding each fall. Also included was a control without any cover crop and with no P addition. Corn yield and P uptake were affected by P fertilizer additions, but not by cover crops. A fairly constant amount of P was supplied from indigenous soil P when no external P was added. When the amount of P added exceeded that removed by corn, the excess P was converted mainly to NaOH-extractable inorganic P (NaOH-Pi). When the amount of P applied was below that removed by corn, indigenous soil NaOH-Pi acted as a source of available P for the plant. With no reduction of organic P (Po) extractable by NaOH or NaHCO3, the contribution from Po to the available P pool appeared limited. The role of NaOH-Pi in P availability in the soil was substantiated by its significant correlation with labile NH4Cl-extractable P (NH4Cl-P; r2 =0.60, P <0.001) or NaHCO3-Pi (r2 =0.81, P <0.001) pools. The NaOH-Pi for the soil reflected the changes in soil P resulting from past fertilizer P input and P removal by the crops.Scientific Paper Number 0005-34 相似文献