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%.     

低分子量有机酸对土壤磷活化影响的研究

研究两种低分子量有机酸（柠檬酸和苹果酸）对土壤磷活化影响,并用修正的Hedley法测定土壤磷活化前后磷组分的变化。结果表明,低分子量有机酸能持续活化土壤磷,活化强度随低分子量有机酸浓度的增大而增强,并且柠檬酸活化土壤磷的能力强于苹果酸。低分子量有机酸能促进作物有效态无机磷组分（H2O-P和NaHCO3-Pi）的释放;同时还促进有机磷组分（NaHCO3-Po和NaOH-Po）的矿化。在低分子量有机酸浓度达到0.5 mmol/L以上时,其对土壤磷组分的活化量的顺序为:NaOH-Pi HCl-P NaHCO3-Pi H2O-P,即铁铝结合态磷 钙结合态磷 作物有效态磷。低分子量有机酸活化土壤磷的过程中伴有大量铁、铝释放,且铁或铝的释放量与磷活化量之间显著正相关（P0.05）。说明铁、铝结合态磷是低分子量有机酸活化土壤磷的主要磷源,并且其活化机制可能与铁、铝结合态磷的螯合溶解有关。     

味精尾液对石灰性潮土无机磷特性及pH值的影响

通过恒温培养试验,探究了以味精尾液为原料的土壤调理剂对北方石灰性潮土无机磷特性和p H值的影响。结果表明,施用味精尾液后土壤有效磷(Olsen-P)、Ca_2-P、Al-P、Fe-P分别增加了70%~120%、155%~288%、29%~42%、6%~10%,Ca10-P减少了7%~8%,且有效性较高的Ca_2-P和Olsen-P持续性好;能够显著降低土壤p H值,培养60 d时,与CK相比,p H值下降了1.17~1.27个单位,而且在一定程度上还能减缓施入土壤的磷肥向无效态转化,提高磷肥有效性。在石灰性土壤施用味精尾液后,运用SPSS软件对土壤Olsen-P及各形态无机磷进行相关性和回归分析得出,Ca_2-P和Fe-P是北方石灰性潮土Olsen-P的主要组分,并得出了Ca_2-P、Fe-P与Olsen-P的回归方程:Y(Olsen-P)=-18.724+1.173X_1(Ca_2-P)+0.905X_4(Fe-P)。     

Isolating the influence of pH on the amounts and forms of soil organic phosphorus

Soil pH influences the chemistry, dynamics and biological availability of phosphorus (P), but few studies have isolated the effect of pH from other soil properties. We studied phosphorus chemistry in soils along the Hoosfield acid strip (Rothamsted, UK), where a pH gradient from 3.7 to 7.8 occurs in a single soil with little variation in total phosphorus (mean ± standard deviation 399 ± 27 mg P kg^?1). Soil organic phosphorus represented a consistent proportion of the total soil phosphorus (36 ± 2%) irrespective of soil pH. However, organic phosphorus concentrations increased by about 20% in the most acidic soils (pH < 4.0), through an accumulation of inositol hexakisphosphate, DNA and phosphonates. The increase in organic phosphorus in the most acidic soils was not related to organic carbon, because organic carbon concentrations declined at pH < 4.0. Thus, the organic carbon to organic phosphorus ratio declined from about 70 in neutral soils to about 50 in strongly acidic soils. In contrast to organic phosphorus, inorganic phosphorus was affected strongly by soil pH, because readily‐exchangeable phosphate extracted with anion‐exchange membranes and a more stable inorganic phosphorus pool extracted in NaOH–EDTA both increased markedly as soil pH declined. Inorganic orthophosphate concentrations were correlated negatively with amorphous manganese and positively with amorphous aluminium oxides, suggesting that soil pH influences orthophosphate stabilization via metal oxides. We conclude that pH has a relatively minor influence on the amount of organic phosphorus in soil, although some forms of organic phosphorus accumulate preferentially under strongly acidic conditions.     

Effects of superabsorbent polyacrylamide hydrogel and gypsum applications on colloidal phosphorus release from agricultural soils

Purpose

The present study aimed to assess the synergistic effects of superabsorbent polyacrylamide hydrogel (SPH) and gypsum on colloidal phosphorus (CP) release from different farmlands (i.e. tea, vegetable, and paddy soils).

Materials and methods

A laboratory experiment was carried out to examine the effects of SPH at different rates of 0.00, 0.01, 0.05, and 0.1% (w/w) and gypsum at the rates of 0 and 0.005% (w/w) on CP released from different farmland soils. For this purpose, CP, colloidal molybdate–reactive P (MRPc), and colloidal molybdenum–unreactive P (MUPc) were measured in soil solutions.

Results and discussion

The results revealed that the release of CP, MRPc, and MUPc ranged respectively from 5.20 to 56.65, 1.62 to 39.09, and 0.33 to 37.10% of total P (TP) in soil solutions across three farmland soils. Besides, the soils treated with SPH and gypsum (0.1%) mitigated CP release respectively by 51.75%, 62.64%, 24.13%, and 62.74% for tea, vegetable, silt loam paddy, and loam paddy soils. However, the MRPc release dropped respectively by 40.22%, 41.04%, 38.55%, and 63.70% in tea, vegetable, silt loam paddy, and loam paddy soils, and similar trends were observed in MUPc, namely, 43.72%, 49.37%, 35.71%, and 56.17% respectively in tea, vegetable, silt loam paddy, and loam paddy soils. The results indicated that gypsum could make a binding in the carboxyl group of polyacrylamide (PAM)/SPH and anion CP because of decreased CP release.

Conclusions

The major form of P was CP, and co-application of PAM/SPH and gypsum could be a promising management approach to moderate CP release from agricultural soils.

     

中国太湖环境土壤磷测试与磷释放

A microtiter plate assay (MPA) for soluble reactive phosphorus (SRP) was applied to samples in overlying water and pore water as well as in three forms of environmental soil test phosphorus (P) types: water soluble phosphorus (WSP), diluted calcium chloride extractable phosphorus (PCaCl2), and Olsen-P in the sediments of Taihu Lake, China, where potential P release in response to pH was analyzed. MPA for rapid P analysis was shown to be promising when applied on samples of natural water and sediment extracts. Concentrations of WSP and PCaCl2 in the sediments were much lower than those of Olsen-P. Olsen-P levels in the littoral sediments along the north coast of Meiliang Bay in Taihu Lake (80 to 140 mg kg^-1) were much higher than those in the mouth of the bay (less than 50 mg kg^-1). The risk of P release in the mouth area of Meiliang Bay was lower than that in the north littoral zone with a risk of sediment P release induced by pH increases.     

不同酸化剂对石灰性土壤pH值、磷有效性的影响

以滴灌方式通过少量多次向土壤施用酸化剂,研究不同酸化剂对石灰性土壤的酸化效果及对玉米磷吸收的影响,以期为提高石灰性土壤的磷素有效性提供理论依据。试验设置对照及两种酸化剂(磷酸脲,硫酸铵+氯甲基吡啶),酸化剂投入量相当于P2O5=60或120 kg/hm~2的等价酸,共计5个处理。施用酸化剂显著降低局部土壤pH值,磷酸脲的作用最佳,土壤pH值最大降幅为0.11个单位,同时也显著提高土壤有效磷含量;在等养分投入和管理水平下,施用酸化剂能增加玉米植株的生物量,提高植株的磷素累积量,且与对照相比,120 kg/hm~2的硫酸铵+氯甲基吡啶处理的玉米产量提高了8.3%。滴灌条件硫酸铵+氯甲基吡啶的酸化效果优于磷酸脲,且高酸化剂量土壤酸化强度较大。滴灌条件下施用酸化剂或酸性肥料是提高石灰性土壤养分有效性和作物增产的一种有效方法。     

碱性长效缓释氮肥对蕉园土壤pH和香蕉氮肥利用效率的影响

【目的】近年来由于超量施用化肥导致蕉园土壤严重酸化,土壤生产力逐年明显下降,香蕉产量骤降,传统产区栽培面积锐减。为此本试验在超高密度栽培条件下,以碱性长效缓释氮肥（ALNF,N 22%）作为供试肥料,研究其降低土壤酸度的效果及对香蕉产量和氮肥利用率的影响,并进一步探讨肥料的碱性能否造成氮素的损失。 【方法】本研究包括两个试验,分别为肥料种类和肥料用量对比试验,香蕉栽培密度均为3333 plant/hm2。试验1为碱性长效缓释肥料（ALNF）、控释配方BB肥料（CRF_BB）、常规肥料（CCF）三因素对比试验,以无氮处理（CK）为对照。试验2为完全ALNF（N 337.5 g/plant）,ALNF+60 g尿素N（ACF1,397.5 g/plant）,ALNF+90 g尿素N（ACF2,427.5 g/plant）,以不施氮肥（CK）为对照。 【结果】超高密度栽培条件下,ALNF处理收获期土壤pH值分别比CRF_BB、CCF、CK、ACF1和ACF2处理提高了1.2、1.2、1.1、0.6和0.3个单位。ALNF和CRF_BB处理香蕉单株产量分别比CCF处理增加了43.4%和35.1%,ALNF和ACF1处理香蕉单株产量分别比ACF2增加了50.6%和40.0%。就氮素平衡而言,CRF_BB和ALNF处理作物携出氮量分别比CCF处理提高了48.9%和24.8%;CCF的氮素表观损失量最多,是ALNF处理的2.3倍;ALNF处理的土壤氮素残留量最多,分别是CRF_BB、CCF处理的1.6倍、2.4倍;ALNF处理香蕉的携氮量分别比ACF1、ACF2处理提高了5.0%、31.9%,土壤残留氮量增加了60.8%、162.6%,ALNF的氮素表观损失最少,并随着尿素添加量的增加而增加,ALNF处理的氮素表观损失量仅为ACF2的1/4。CRF_BB和ALNF处理的氮肥利用率分别比CCF的提高了66.7%、33.7%,ALNF处理比ACF1、ACF2处理提高了27.8%、87.7%,ACF1处理的比ACF2处理提高了46.9%。 【结论】碱性长效缓释氮肥能够显著降低土壤酸度,土壤pH提高了0.3~1.2个单位,提高香蕉产量35%~50%,增加香蕉氮素吸收量24%~50%,增加土壤氮素残留量,减少氮素表观损失,提高氮肥利用率27%~67%。单独施用碱性长效缓释氮肥不会造成氮素损失,但是碱性长效缓释氮肥与尿素混合使用会造成氮素损失并降低氮肥利用率。     

Increasing pH releases colloidal lead in a highly contaminated forest soil

Colloids can play an important role in the leaching of lead (Pb) in soils, and liming to increase pH may produce conditions conducive to colloid release. We studied the effect of pH and the role of counterion valency on the mobilization of Pb in two topsoil horizons of a former shooting range. In batch experiments, the release of both dissolved and colloidal Pb was studied at a pH range between 3 and 7. The pH was adjusted with solutions of nitric acid (pH 3) and KOH and Ca(OH)₂ (pH 4–7) and the chemical composition, size and charge of the mobilized colloids were determined. In the presence of the monovalent K⁺‐ion concentrations of colloidal and dissolved Pb increased markedly with increasing pH. Colloids were stabilized not only by electrostatic but also by steric repulsion. Organic colloids seem to dominate at low pH of the KOH‐treatment; at pH > 4 mineral particles were also dispersed. Even though the presence of the Ca²⁺ ion reduced the concentrations of colloidal Pb more than did the K⁺ ion, our results of the Ca(OH)₂ treatment show that the relevance of both colloidal and dissolved Pb increases at a pH of about 5.8. Risk assessment on limed sites should therefore take into account both dissolved and colloidal Pb in judging the likelihood of Pb leaching.     

胶体态磷和溶解态磷在不同土壤磷饱和度稻田土壤中形态分布

Soil dissolved phosphorus (P) and colloidal P mobilization could be closely related to the degree of phosphorus saturation (DPS). Effects of a wide range of DPS on the distributions of dissolved P and colloidal P in a paddy soil profile were investigated in this study. Dissolved P and colloidal P in water-dispersible soil colloid suspension increased obviously with increasing DPS. The change point of DPS was at 0.12 by using a split-line model. Above the value, dissolved P (3.1 mg P kg-1 ) in soil profile would increase sharply and then transfer downward. Compared with dissolved P, colloidal P was the dominant fraction (78%-91%) of P in soil colloid suspension, and positively related to DPS without a significant change point. The high release of colloids in subsoils with low DPS was attributed to the low ionic strength and high pH value in subsoils. The DPS also had a significant and positive correlation with electrical conductivity (EC), but it showed a negative correlation with pH value. However, the concentration of colloidal P was not greatly correlated to the pH value, EC and optical density of the soil colloid suspension. The results indicated that DPS was an important factor that may affect the accumulation and mobilization of water-extractable colloidal P and dissolved P.     

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。     

Effect of phosphorus status of the soil on selenium availability

Due to its importance for human and animal health, low bioavailability of selenium (Se) is of concern in large parts of the world. Among the factors determining Se availability is competition for binding sites by other anions. In order to evaluate the effect of different soil P status on Se availability from fertilizer, adsorption studies were conducted with soils ranging from low to very high available P as measured in ammonium lactate (P‐AL) and addition of Se as either selenate or selenite. Generally selenite, and to some extent also selenate, adsorption decreased with increasing P‐AL status of the soil. However, in a silt loam, the increase in P‐AL from 140 (high) to 210 mg P kg^–1 (very high) did not result in a corresponding decrease in Se adsorption. Phosphorus saturation, on the other hand, was found to be lower in the sample that was very high in available P, suggesting that both the total amount of P on binding sites and the amount of plant‐available P influence Se availability. Selenate addition caused an increase in P availability, especially when added together with phosphate to a silt loam with very high P‐AL status.     

菜豆根瘤菌对土壤无机磷的活化释放作用

以土壤为磷源,通过液体培养研究了7株菜豆根瘤菌(Rhizobium sp.)对土壤磷的利用。结果表明,菜豆根瘤菌能释放大量的氢离子,使液体培养基的pH大幅度降低,氢离子的浓度至少提高20倍以上。根瘤菌分泌有机酸的种类与数量因菌株不同而异,这些有机酸包括甲酸、乙酸、草酸、丁二酸、柠檬酸、苹果酸和乳酸等,大部分根瘤菌能分泌乙酸。在接种根瘤菌的液体培养基中,全磷含量显著高于不接种的液体培养基,土壤无机磷总量则显著降低。由于土壤是培养基磷的唯一来源,故根瘤菌可促进土壤无机磷的溶解释放。相关分析表明,培养基的pH与土壤无机磷总量呈极显著正相关(r=0.893**,n=8),说明根瘤菌分泌的氢离子可能是溶解土壤无机磷的原因之一。接种根瘤菌显著降低土壤闭蓄态磷,土壤中的铁磷、铝磷和钙磷因菌株不同而降低,其原因可能与有机酸分泌的数量和种类有关。根瘤菌既能释放氢离子又可分泌多种有机酸的现象表明其活化土壤无机磷的方式具有多样性,可能有益于豆科植物利用不同形态的难溶性磷,使之适应各种不同的低磷土壤。     

Effect of superphosphate applications on soil phosphorus and on crop phosphorus removal by the strawberry

Abstract

Rate of superphosphate application significantly increased the Bray #2 (easily acid soluble plus adsorbed P) and “AlPO₄”; fractions for 3 successive years. A single dolomitic limestone application increased “FePO₄”; by an average of 36% one year after application. Crop P removal by the strawberry cv. ‘Acadia’ was approximately 2–3 ppm each year and it was not possible to relate this small amount to any of the soil P fractions determined.     

Effect of organic manure on the biological activities associated with insoluble phosphorus release in a blue purple paddy soil

Abstract

This study examined the effects of organic manure and chemical fertilizer on soil microflora, soil respiration, number of inorganic phosphate solubilizing bacteria, and organic phosphorus (P) mineralizing bacteria. The inorganic phosphate solubilizing rate, organic P mineralizing rate, and selected enzyme activities in a blue purple paddy soil were also studied. The results showed that organic manure significantly increased the total number of fungi, actinomyces, bacteria, P solubilizing bacteria, organic P mineralizing bacteria, P solubilizing rate and organic P mineralizing rate, soil respiration rate, and selected enzyme activities, whereas chemical fertilizer resulted in a smaller effect, and bacteria were affected more than fungi and actinomyces by organic manure. The enhancement of biological activities caused by organic manure might be due to the introduction of a large amount of living microorganisms and readily‐utilizable carbon source on which microorganisms live. This study showed that the augment of inorganic phosphate solubilizing bacteria and organic P mineralizing bacteria was one of the reasons that organic manure increased the avilability of P in a blue purple paddy soil.     

盐分对土壤锰释放的影响

盐分能诱导土壤锰的释放 .Na+和Ca2 +的离子交换作用促进了土壤锰向水溶液中释放 ,提高了土壤锰的有效性 ;同时 ,盐分降低了土壤的 pH值 ,并使土壤氧化还原电位发生变化 ,引起土壤中锰形态间的转化 .NO- 3 离子对氧化还原电位影响显著 ,硝酸盐处理土壤中易还原态锰含量显著增加     

过磷酸钙对石灰性土壤有效磷及无机磷组分的影响

为研究水溶性磷肥在石灰性土壤中的转化,采用室内土壤培养的方法,在土壤中分别添加过磷酸钙0、6.25、12.5、25、50和100 mg/kg干土(即P0、P6.25、P12.5、P25、P50和P100处理),保持土壤湿度为田间持水量的70%～80%,在25℃恒温培养箱中培养120 d。培养期间在第1、3、7、15、30、60和120 d连续采样,测定土壤Olsen-P、CaCl2-P和各无机磷组分的含量。结果表明,在石灰性土壤中施用过磷酸钙能显著增加土壤Olsen-P和CaCl2-P含量,在一定的培养时间内,过磷酸钙转化为土壤Olsen-P和CaCl2-P的比例不随施肥量的变化而变化。随着培养时间的延长,土壤有效磷含量逐渐下降,尤其是培养前期(前7 d)土壤有效磷含量显著下降,之后下降速率减缓。施入土壤中的过磷酸钙主要转化为Ca2-P和Ca8-P(两者之和约占90%),其次是Al-P和Fe-P(两者之和约占10%),在短期内O-P和Ca10-P相对较为稳定。随着培养时间延长,Ca2-P逐渐向Ca8-P转化,在培养的前30 d转化速率较快,之后速率减缓。随着磷肥施用量的增加,Ca2-P转化为Ca8-P所需的时间逐渐延长。Olsen-P和CaCl2-P含量均与土壤无机磷组分中的Ca2-P、Ca8-P和Al-P含量呈显著正相关,通过逐步回归分析表明,其中Ca2-P是土壤Olsen-P和CaCl2-P的主要来源。     

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。     

Effect of soil pH on cation and anion solubility

Abstract

The effect of soil pH on the exchangeability and solubility of soil cations (Ca, Mg, Na, K, and NH₄‐N) and anions (NO₃‐N, Cl, and P) was investigated for 80 soils, spanning a wide range in physical and chemical properties and taxonomic groups. This information is needed from environmental and agronomic standpoints to estimate the effect of changes in soil pH on leachability and plant availability of soil nutrients. Soils were incubated with varying amounts of acid (H₂SO₄) and base (CaCO₃) for up to 30 days. Although acid and base amendments had no consistent effect on cation exchangeability (as determined by neutral NH₄OAc), amounts of water‐soluble Ca, Mg, Na, K, NH₄‐N, and P decreased, while NO₃‐N and Cl increased with an increase in soil pH. The increase in cation solubility was attributed to an increase in the negative charge of the soil surface associated with the base addition. The change in surface electrostatic potential had the opposite effect on amounts of NO₃‐N and Cl in solution, with increases in N mineralization with increasing soil pH also contributing to the greater amount of NO₃‐N in solution. The decrease in P solubility was attributed to changes in the solubility of Fe‐, A1‐, and Ca‐P complexes. The logarithm of the amount of water‐soluble cation or anion was a linear function of soil pH. The slope of this relationship was closely related (R² = = 0.90 ‐ 0.96) to clay content, initial soil pH, and size of the cation or anion pool maintaining solution concentration. Although the degree in soil pH buffering increased with length of incubation, no effect of time on the relationship between cation or anion solubility and pH was observed except for NO₃‐N, due to N mineralization. A change in soil pH brought about by acid rain, fertilizer, and lime inputs, thus, affects cation and anion solubility. The impact of these changes on cation and anion leachability and plant availability may be assessed using the regression equations developed.     

连续施用解磷菌肥对复垦土壤磷酸酶和Hedley磷形态的影响

为了研究增施解磷菌肥对土壤供磷状况的改善和土壤中磷有效性的提高状况,通过田间小区试验研究了连续施用解磷菌肥对复垦5年土壤碱性磷酸酶活性及Hedley磷形态的影响。结果表明:施用无机肥+有机肥+解磷菌肥处理的土壤碱性磷酸酶活性最高,为30.65μg/(g·h),比对照提高了83.86%。本试验年与第3年复垦土壤相比,土壤中Hedley磷形态的含量都有不同程度的增加,H_2O-Po含量以无机肥+有机肥+解磷菌肥处理为最高,比对照提高了93.90%;NaOH-Pi、HCl-Pi、HCl-Po含量以无机肥+解磷菌肥处理最大,分别比对照提高了194.2%、61.87%、105.8%;残渣态磷含量以无机肥处理影响最大,比对照提高了22.87%;H_2O-Pi、NaHCO_3-Po含量以有机肥处理最大,比对照提高了129.2%、85.89%;NaHCO_3-Pi、NaOH-Po含量以有机肥+解磷菌肥处理提高最大,分别提高了176.9%、114.4%。可以得出:施用解磷菌肥的处理增加复垦土壤中H_2O-Po、NaHCO_3-Pi、NaOH-Pi、NaOH-Po、HCl-Pi、HCl-Po含量的效果较好。H_2O-Pi、H_2O-Po、NaHCO_3-Pi、NaHCO_3-Po、NaOH-Pi、NaOH-Po、HCl-Pi与碱性磷酸酶均呈极显著相关。解磷菌肥在一定程度上增强了复垦土壤碱性磷酸酶活性,影响土壤中Hedley磷分级的各形态磷素含量,从而提高磷的有效性。