Soil phosphorus fractions in aggregate size classes in southwestern China

The build‐up of topsoil phosphorus (P) through excess fertilizer application can increase P losses in run‐off leading to negative impacts on aquatic ecosystems. To better understand the risk of P losses, the fractions of soil P in four aggregate size classes were quantified for two vegetable production sites (<10 and >25 yrs) and a conservation buffer site (8 yrs) in southwestern China. Sequential extraction methods of inorganic P (Pi) and organic P (Po) were carried out on samples from Nitisol and Gleysol soils from 0 to 5 cm and 5 to 10 cm depths. On average, soil Pi concentrations exceeded Po concentrations threefold, primarily in the bioavailable Pi fractions (labile Pi, loosely bound Pi and non‐occluded Pi). Soil Po fractions and bioavailable Pi fractions were significantly greater under the >25 yrs field than in the <10 yrs field. The conversion of fields under vegetable production to forested buffer substantially decreased the levels of the bioavailable Pi and labile Po in the Gleysol after 8 yrs. Soil macro‐aggregates (>0.25 mm) had greater concentrations of bioavailable Pi fractions and of labile and moderately labile Po than did micro‐aggregates and silt and clay size components. Although more P was stored in recalcitrant P forms, a larger percentage of all P fractions was found in macro‐aggregates in these soils. Small active P‐enriched aggregates potentially intensify export of P from the vegetable soils by run‐off, and therefore, management practices must be optimized to enhance agricultural P efficiencies.     

Phosphorus fractions of soils under <Emphasis Type="Italic">Lotus corniculatus</Emphasis> as affected by different phosphorus fertilizers

The objective of this work was to assess the changes of soil P fractions by Lotus corniculatus and to determine contribution of each fraction to plant P nutrition. Phosphorus was added at a rate of 240 mg/pot as triple superphosphate (20% P), phosphate rock (13% P), or poultry litter (2% P) to a Vertisol or an Inceptisol; a control treatment (without P fertilizer) was also included. Then, L. corniculatus was sowed and harvested eight times; both yields and P content of plant were determined at each harvest. Soil P fractions were determined by Hedley’s modified method. The content of labile and moderately labile P [anionic exchange membrane-Pi (AEM-Pi), NaHCO₃-Pi, and NaOH-Pi] fractions were markedly reduced and were probably due to P uptake by plants. The content of the HCl-Pi fraction of the phosphate-rock-treated soil decreased whereas that of the residual P fraction was not modified. The content of organic forms increased in all treatments. The content of both labile organic P and moderately labile organic P were positively and significantly correlated with the P concentration of roots and with roots biomass, suggesting that the increase in these two organic fractions was related to root production. AEM-Pi accounted for 95% and 84% of absorbed P in Vertisol and Inceptisol, respectively.     

Organic and inorganic phosphorus in Mollisol soil under different tillage practices

The distribution of soil phosphorus (P) between different organic and inorganic forms depends on, among other factors, the tillage systems. The evaluation of soil P fractions is essential to determine if they are related to available P. The objective was to characterize the P forms from a soil under no tillage (NT) and conventional tillage (CT). Soil samples were taken at 0–5, 5–10 and 10–20 cm depth from a fine, mixed, thermic Petrocalcic Paleoudoll, after 8 years under NT and CT. Inorganic and organic P was measured in the anion exchange membrane (AEM), NaHCO₃, NaOH, NaOH after sonication, HCl and residual fractions extracted sequentially. Microbial P was determined by fumigating with chloroform after P extraction with AEM. The tillage systems did not affect the total P content but the distribution of P among fractions changed between NT and CT. No tillage system had significantly higher microbial P at all soil depths and ranged from 34 mg P kg⁻¹ at 0–5 cm to 10 mg P kg⁻¹ at 10–20 cm. In the upper 10 cm of soil, NT tended to have higher AEM-Pi and NaHCO₃-Pi comparing to CT system. The increase in AEM-Pi was closely related to organic carbon increases and pH decreases. The was a consistently higher concentration of NaOH-Po but the increase was significant al 5–10 and 10–20 cm, and represented on average about 35% of total P. The residual P which was considered mostly organic was also an important pool in both NT and CT, and accounted for about 30% of total P. Therefore, P availability is mainly controlled by organic P which makes up a larger proportion of total P.     

Phosphatase activity and phosphorus fractions in Karri (Eucalyptus diversicolor F. Muell.) forest soils

Summary Karri forest soils contain negligible concentrations of labile-P, low concentrations of total P and more P in organic forms than inorganic. The ratio of organic P to inorganic P was lowest (1:2) in recently burnt surface soils and greatest (7:1) at depth in soil that had been undisturbed for long periods of time. Phosphomonoesterase and phosphodiesterase activities (to 10 cm depth, phosphomonoesterase 700–1300; phosphodiesterase 2000–2400 g nitrophenol released h^-1 g^-1 fresh weight) were comparable to those in other, organically rich forest soils. The optimum pH for phosphatase activities were within 1–2 units of soil pH (6) and little reduction in activity was observed over the pH range 4–8. Phosphatase activity was reduced by air-drying (up to 20-fold reduction) and was almost entirely absent in soils that were heat-affected as a result of logging/burning operations. Neither phosphomonoesterase nor phosphodiesterase were directly related to soil P fractions or total P. A reduction in P demand is postulated as the cause of reduced phosphatase activity and the increased concentration of organic P with increasing soil depth.     

Phosphorus fractions in an acid soil continuously fertilized with mineral and organic fertilizers

The effect of different treatments on the fate of applied P was investigated in a long-term field experiment started in 1972–1973 following a maize–wheat sequence. The soil samples were collected after 29 years of continuous addition of mineral fertilizers and amendments such as farmyard manure (FYM) and lime. The total P content of all the treatments increased compared to the original soil; NaOH-inorganic P (P_i) (NaOH-P_i) representing Fe and Al-bound P was the dominant P_i fraction. At the beginning of the experiment (1972–1973), the various P pools could be quantitatively ranked in the following order: residual P>NaOH-organic P (P_o)>NaOH-P_i>NaHCO₃-P_o>NaHCO₃-P_i>HCl-P>H₂O-P. As a result of continued P fertilization and cropping, the order changed as follows: residual P>NaOH-P_i>NaOH-P_o>NaHCO₃-P_i>NaHCO₃-P_o>HCl-P>H₂O-P. Compared to the imbalanced mineral fertilizer application, the balanced as well as integrated application of nutrients resulted in significantly lower P adsorption capacity of soils. The Olsen extractable-P fraction (plant-available P) increased from about 12 mg kg^–1 soil in 1972 to about 81 mg kg^–1 soil in the treatments receiving P for the last 29 years.     

Tillage effects on maize yield in a Colombian savanna oxisol: Soil organic matter and P fractions

Soil organic matter (SOM) and phosphorus (P) fractions play a key role in sustaining the productivity of acid-savanna oxisols and are greatly influenced by tillage practices. In 1993, a long-term experiment on sustainable crop rotation and ley farming systems was initiated on a Colombian acid-savanna oxisol to test the effects of grain legumes, green manures, intercrops and leys as possible components that could increase the stability of systems involving annual cereal crops. Five agropastoral treatments (maize monoculture—MMO, maize–soybean rotation—MRT, maize–soybean green manure rotation—MGM, native savanna control—NSC and maize-agropastoral rotation—MAP) under two tillage systems (no till-NT and minimum tillage-MT) were investigated. The effects of NT and MT on SOM and P fractions as well as maize grain yield under the five agropastoral treatments were evaluated. Results showed that soil total C, N and P were generally better under no-till as compared to minimum-tilled soils. While P fractions were also generally higher under no-till treatments, SOM fractions did not show any specific trend. Seven years after establishment of the long-term ley farming experiment (5 years of conventional tillage followed by 2 years alternative tillage systems), MT resulted into moderately higher maize grain yields as compared to NT. The MGM rotation treatment had significantly higher values of maize yield under both tillage systems (4.2 Mg) compared to the NSC (2.3 Mg ha⁻¹). Results from this study indicate that the rotational systems (maize–soybean green manure and maize-pastures) improved the soil conditions to implement the no-till or minimum tillage systems on Colombian savanna oxisol.     

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

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

Influence of cultivation on the distribution of phosphorus in three soils from NE Scotland and their aggregate size fractions

Abstract. The effect of cultivation on the P properties of whole soils and aggregate sizes separated from them was investigated for soil developed on three types of parent material. Cultivation, with associated fertilizer additions, increased both the total soil P content and extractable P of the whole soils. When the soils were separated into aggregate sizes (< 2, 2-52, 53-150 and 151 2000 μm), total soil P and resin extractable P increased with decreasing aggregate size. Water extractable inorganic P exhibited the opposite trend, while concentrations of water extractable organic P were similar from each aggregate size. Eroded aggregates can adsorb P or release P to solution, the extent of which will be dependent upon a combination of soil attributes and the prevailing solution conditions. The resulting equilibrium P concentration (EPC) of the eroded material will be markedly different from that of the whole soil. By increasing the P content, particularly of the smaller sized aggregates it is likely that the EPC of the eroded material would favour greater P desorption.     

酸性土壤固磷机理研究进展

随着酸性土壤固磷机理研究的不断深入,已经有一些研究开始重视土壤中Mn对P的固定作用.本文以Mn-P的提出为出发点,论述了近10年来对酸性土壤固磷机理研究的新进展,突破了常规P素形态分级研究中分为Fe-P,Al-P,O-P和Ca-P等无机磷测定的经典分级,认为玄武岩母质砖红壤中的Mn-P是P素固定的主要形式之一,进而比较了Fe、Al、Mn对P固定作用,并从P的化学有效性与生物有效性差异等方面进行了比较全面的论述,提出了减少P素固定提高磷肥利用率的措施及今后的重点研究方向.     

Distribution of inorganic phosphorus fractions in some soil profiles of Zagros forest of Iran

The aim of the present study was to evaluate the status of inorganic phosphorus (P) fractions in ten virgin soil profiles, and to study the relationships between P fractions and soil properties from Kohgyloyeh and Boir Ahmad province, Iran. The soils belonged to Alfisols, Entisols, Mollisols, and Inceptisols. Mean annual precipitation and temperature ranges were 450–850 mm and 12.2–22.4°C, respectively. Inorganic P was fractionated by sequential extraction with NaHCO₃, NH₄OAc, MgCl₂, NH₄F, NaOH, citrate-dithionite-bicarbonate (CBD), and H₂SO₄, which are referred to as NaHCO₃–P, NH₄OAc–P, MgCl₂–P, NH₄F–P, NaOH–P, CBD–P, and H₂SO₄–P, respectively. Generally, the NaHCO₃–P, NH₄OAc–P, MgCl₂–P, and NH₄F–P were higher in surface horizons, especially wherever there was higher annual precipitation. Results showed that H₂SO₄–P constituted the largest inorganic P fractions in all profiles. For all the soils studied the distribution of P fractions was similar to that of weakly weathered soils under arid and semi-arid regions which represent an early stage of development. Pedogenic P compounds were higher where weathering was higher, i.e., in surface horizons and at higher annual precipitation.     

Sequentially extracted phosphorus fractions in peat‐derived soils

Phosphorus (P) forms were sequentially extracted from peat derived soils (Eutric Histosols and Gleysols) at eight sites in Saxony‐Anhalt (Germany) to disclose general differences in P pools between mineral and organic soils and to investigate effects of peat humification and oxidation in conjunction with land use and soil management on the P status of soils. Overall 29 samples providing a wide variety of basic chemical properties were subjected to the Hedley fractionation. The Histosol topsoils contained more total P (P_t) (1345 ± 666 mg kg^—1) than the Gleysol topsoils (648 ± 237 mg kg^—1). The predominant extractable fractions were H₂SO₄‐P (36—63 % of P_t) in calcareous and NaOH‐P_o (0—46 % of P_t) in non‐calcareous Histosols. These soils had large pools of residual P (13—93 % of P_t). Larger contents and proportions of P_o and of labile P fractions generally distinguished organic from mineral soils. Regression analyses indicated that poorly crystalline pedogenic oxides and organic matter were binding partners for extractable and non‐extractable P. Intensive management that promotes peat humification and oxidation results in disproportional enrichments of labile P fractions (resin‐P, NaHCO₃‐P_i, and NaHCO₃‐P_o). These changes in P chemistry must be considered for a sustainable management of landscapes with Histosols and associated peat derived soils.     

Influence of ferredoxin levels on nitrate reductase activity in iron deficient lemon leaves

The relationship between nitrate reductase activity and ferredoxin levels in lemon tree leaves was studied. The experiments were carried out on leaves from full‐nutrient sufficient trees as the reference, and on leaves from trees with several nutritional stresses, mainly iron chlorosis from trees growing under Fe‐stressed conditions.

Iron deficiency reduced leaf ferredoxin concentration and consequently decreased nitrate reductase activity. Fe(II) infiltration treatments of intact leaves, as well as several incubation assays, permit to deduce the dependence of the enzymatic nitrate reduction of the leaf ferredoxin levels.     

Effects of repeated manure and fertilizer phosphorus additions on soil phosphorus dynamics under a soybean-wheat rotation

 Soil P availability and efficiency of applied P may be improved through an understanding of soil P dynamics in relation to management practices in a cropping system. Our objectives in this study were to evaluate changes in plant-available (Olsen) P and in different inorganic P (P_i) and organic P (P₀) fractions in soil as related to repeated additions of manure and fertilizer P under a soybean-wheat rotation. A field experiment on a Typic Haplustert was conducted from 1992 to 1995 wherein the annual treatments included four rates of fertilizer P (0, 11, 22 and 44 kg ha^–1 applied to both soybean and wheat) in the absence and presence of 16 t ha^–1 of manure (applied to soybean only). With regular application of fertilizer P to each crop the level of Olsen P increased significantly and linearly through the years in both manured and unmanured plots. The mean P balance required to raise Olsen P by 1 mg kg^–1 was 17.9 kg ha^–1 of fertilizer P in unmanured plots and 5.6 kg ha^–1 of manure plus fertilizer P in manured plots. The relative sizes of labile [NaHCO₃-extractable P_i (NaHCO₃-P_i) and NaHCO₃-extractable P₀ (NaHCO₃-P₀)], moderately labile [NaOH-extractable P_i (NaOH-P_i) and NaOH-extractable P₀ (NaOH-P₀)] and stable [HCl-extractable P (HCl-P) and H₂SO₄/H₂O₂-extractable P (resisual-P)] P pools were in a 1 : 2.9 : 7.6 ratio. Application of fertilizer P and manure significantly increased NaHCO₃-P_i and -P₀ and NaOH-P_i, and -P₀ fractions and also total P. However, HCl-P and residual-P were not affected. The changes in NaHCO₃-P_i, NaOH-P_i and NaOH-P₀ fractions were significantly correlated with the apparent P balance and were thought to represent biologically dynamic soil P and act as major sources and sinks of plant-available P. Received: 23 October 1997     

Influence of soil fractions on microbial degradation behavior of mineral hydrocarbons

Various interactions occurring between organic chemicals and soil constituents participate in the determination of the fate of these pollutants, including their biodegradability. These relations need to be characterized in order to design and successfully implement a bioremediation application. In the present study, biodegradation of spiked and aged crude oil contamination in two dissimilar soils was related to their composition. GC-FID analysis of bulk soil samples as well as sand- and <63 μm fractions showed considerable differences in contaminant distribution and degradation behavior within these fractions. Whereas a freshly spiked silty soil showed reasonable degradation (51%), degradation was not significant after ageing. By contrast, a sandy soil was degraded by 25% (recently contaminated) and 19% (aged). Biodegradation occurred in the fine fraction only, with a comparably high content of organic carbon whereas hydrocarbon concentration remained constant in the sand fraction. This was correlated with sorption to the fine fraction where hydrocarbon concentrations were higher by over an order of magnitude compared to the sand fraction. Soil composition, biology and chemistry exert a pronounced influence on microbial degradation in respect to (i) contaminant availability and (ii) the structure and density of the microbial community.     

施磷对苦麦菜生长及土壤磷素淋失的影响

利用网室土柱模拟试验, 研究了不同磷用量[0、0.05 g·kg^-1(土)、0.10 g·kg^-1(土)、0.20 g·kg^-1(土)]对苦麦菜产量、磷素吸收和利用及土壤磷淋失的影响。结果表明, 施磷显著增加苦麦菜产量、促进植株对磷的吸收。苦麦菜产量在低磷水平[0.05 g·kg^-1(土)]时最高, 为每个土柱186.29 g。随磷用量增加, 苦麦菜产量和磷肥利用率明显降低, 植株吸磷量无明显变化。施磷显著增加土壤磷淋失量, 且随磷用量增加, 不同形态磷淋失量均显著增加。同一磷处理颗粒磷淋失量高于溶解态磷。不同磷用量条件下土壤各形态磷的淋失率均低于0.1%。低量施磷条件下溶解态磷在施磷后第10 d 出现第1 次淋失高峰; 中量和高量施磷条件下溶解态磷在施磷后第10 d 和第40 d 分别出现2 次淋失高峰。土壤总磷和颗粒磷淋失高峰期在施磷后第40~50 d 出现。施肥后第60 d, 土壤总磷、溶解态磷和颗粒磷淋失浓度均明显降低。综合考虑苦麦菜产量、磷素吸收和利用及土壤磷淋失量等因素, 苦麦菜以0.05 g·kg^-1(土)的施磷量为佳。     

Phosphorus fractions in Andisol and Ultisol inoculated with Bacillus thuringiensis and phosphorus uptake by wheat

Abstract

Only a small portion of soil phosphorus (P) is available to plants on a short-term basis, and therefore, P taken up by crops in one growing season is small compared to total P (Pt) content of the soil. A group of soil microorganisms capable of transforming insoluble P into soluble and plant accessible forms. The objective of this study was to evaluate the changes in soil P-pools and P uptake by wheat crops as influenced by inoculation with Bacillus thuringiensis in two soils (Andisol and Ultisol), the experiment was conducted in pots under greenhouse conditions using a completely randomized design. Wheat plants were inoculated and re-inoculated at 20 and 46?days after sowing, respectively, with B. thuringiensis; and, plant sampling were performed after 46, 66 and 87 and soil at 87?days based on the Zadoks growth scale, and the soil was submitted by Hedley’s P fractions. The inoculation with B. thuringiensis affected significantly some P organic P (P_o) and inorganic P (P_i) fractions in both soils (Andisol and Ultisol), improved P uptake by wheat crop in (Ultisol) and decreased significantly in (Andisol). The positive effect was more consistent in Ultisol than in Andisol, this strain can be solubilized P fraction extracted with conc. HCl-P_o and HCl 1?mol.     

Manganese deficiency in wheat genotypes: Physiological responses and manganese deficiency tolerance index

Manganese (Mn) deficiency limits wheat productivity on sandy loam, calcareous and alkaline soils cropped with rice. Variation of wheat genotypes to sustain production and Mn use from Mn deficient condition was investigated to screen efficient genotypes. Forty-seven diverse wheat genotypes were evaluated on Mn sufficient (0.195 µM) and Mn deficient (0 µM) nutrient solution to elucidate physiological basis of Mn deficiency tolerance and to develop manganese deficiency tolerance index (MDTI). Shoot dry weight and mean Mn accumulation was 136.7% and 76.5% enhanced when Mn nutrition was improved, respectively. Efficient genotypes under limited Mn had lower root length/shoot weight ratio but higher relative shoot growth rate with higher shoot demand on root which reflected higher Mn influx. Genotypes were classified as tolerant (>0.66), semi-tolerant (0.33–0.66) and sensitive (<0.33) on the basis of MDTI (0–1 scale). Manganese efficient genotypes are most desirable for sustainable production of wheat under low Mn.     

施磷对玉米吸磷量、产量和土壤磷含量的影响及其相关性

为了给玉米磷高效利用提供理论依据, 在低磷土壤(Olsen-P 4.9 mg·kg^-1)上, 通过田间试验, 研究了施磷0(T₀)、50 kg(P₂O₅)·hm^-2(T₁)、100 kg(P₂O₅)·hm^-2(T₂)、200 kg(P₂O₅)·hm^-2(T₃)、1 000 kg(P₂O₅)·hm^-2(T₄)对两个玉米品种"鲁单9002" (LD9002)、"先玉335"(XY335)的产量、磷素吸收利用及根际磷动态变化的影响。结果表明: 两玉米品种根际土、非根际土速效磷含量在不同生育时期都表现为T12O₅)·hm^-2的T₃处理非根际土转化为根际土土壤磷的量最大, 同时玉米生物量、产量、磷转移量也达到最高, 而施磷1 000 kg(P₂O₅)·hm^-2处理玉米生物量、产量与中磷水平相比没有显著增加, 但植株吸磷量较高。XY335的花后磷转移量小于LD9002。相关分析表明, LD9002根际土、非根际土速效磷含量与茎、叶吸磷量之间显著相关, 以播种后79 d与茎、叶磷浓度、吸磷量、生物量、产量之间的相关系数最高; 而XY335根际土、非根际土速效磷含量与茎、叶磷浓度之间显著相关, 在播种后47 d期间与茎、叶磷浓度、吸磷量、生物量、产量之间的相关性最好。因此, 在低磷土壤上, LD9002和XY335分别在播种后79 d和47 d时是植株对磷的敏感期, 可以通过测试根际土、非根际土速效磷含量来反映土壤的供磷状况; LD9002在79 d时最大吸磷量需要的根际土、非根际土速效磷含量分别为54.95 mg·kg^-1、32.99 mg·kg^-1, XY335品种在47 d时最大吸磷量需要的根际土、非根际土速效磷含量分别为51.24 mg·kg^-1、35.35 mg·kg^-1; 施磷量1 000 kg(P₂O₅)·hm^-2处理两品种玉米产量、生物量、磷积累量与施磷量100~200 kg(P₂O₅)·hm^-2处理没有显著差异。     

长期不同供磷水平下南方黄泥田生产力及磷组分特征

红壤性水稻土磷素易受铁、铝等固定而有效性低,过量施用磷肥则产生磷素淋失风险,研究不同供磷水平下黄泥田生产力、磷库平衡及磷组分特征,可为磷素高效管理提供依据。本研究基于福建黄泥田连续30年的供磷定位试验,研究连续30年3个供磷水平下[不施磷肥(CK)、30 kg(P_2O_5)·hm~(-2)(P1)、60 kg(P_2O_5)·hm~(-2)(P2)]水稻(1987—2004年为双季稻,2005年始种植单季稻)产量演变规律,并于试验的第31年分析土壤有效磷、全磷、无机磷库与有机磷库组分变化。结果表明,连续30年施用磷肥,与CK相比,早稻、晚稻与单季稻历年平均产量P1处理分别提高64.9%、37.0%与19.9%, P2处理分别提高67.0%、41.2%与20.4%,差异均显著。不同稻作制度下黄泥田磷肥的增产效果为早稻晚稻单季稻。与P1处理相比,P2处理第31年土壤有效磷含量提高190.5%,全磷含量提高32.4%,差异均显著;Al-P、Fe-P、Ca-P含量与无机磷含量均显著提高,Al-P、Fe-P占无机磷比重分别提高2.12个百分点与4.40个百分点,但O-P比重降低9.45个百分点,差异均显著。施磷肥总体提高了活性有机磷(LOP)与中等活性有机磷(MLOP)含量,降低了高稳定性有机磷(HSOP)含量,P2处理表现尤为明显;增施磷肥, LOP与MLOP占有机磷比重增加, HSOP比重降低。籽粒或秸秆产量与Al-P、Fe-P、Ca-P、MLOP、LOP含量呈显著正相关。综上,黄泥田连续30年施磷肥增产效果明显, P1与P2处理的产量无显著差异,但P1处理呈现磷表观亏缺。增施磷肥提高了无机磷Al-P、Fe-P、Ca-P比重,有机磷组分呈现由活性较低的形态向活性较高的形态转化趋势。每茬60 kg(P_2O_5)·hm~(-2)可维持磷素养分表观平衡并保持适宜的有效磷水平。     

Effect of phosphorus,nitrogen fertilization and foliar applied manganese on yield and nutrient concentration of soybean

Abstract

A greenhouse experiment was conducted on clay loam soil of pH 7.8 to evaluate the effect of P, N fertilization and foliar applied Mn on yield and nutrient concentration in leaves and seeds of soybean. A significant yield increase was obtained for each added increment of P fertilizer up to 30 kg P₂O₅/acre. At application rates of 0, 15, 30 & 45 kg P₂O₅/acre, the seed yield was subsequently 27.8, 65.8, 82.8 & 83.6% of the maximum yield obtained at the maximum calculated P level. The yield increase accounted 14.2 and 10.2% for N and Mn applications. In all treatments, in which P was combined with N, the seed yield was relatively higher than with P or N applied alone.

Phosphorus, N and Mn content in leaves and seeds were positively correlated with the applied nutrient fertilizers. At any given level of applied P and Mn, P content was significantly higher in +N than ‐N treatments. By Mn application, P content in leaves and seeds was decreased. Phosphorus and Mn applications did not influence N content in leaves and seeds.