Inorganic Phosphorus Fractions Research Articles

引种降香黄檀和顶果木对石漠化山区土壤磷素转化及其有效性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 引种降香黄檀和顶果木对石漠化山区土壤磷素转化及其有效性的影响 DOI: 10.5846/stxb202012223252 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31960240）；广西自然科学基金项目（2017GXNSFAA198207，2018GXNSFAA294139，2019GXNSFAA185023） Effects of introducing Dalbergia odorifera and Acricarpus fraxinifolius on soil phosphorus transformation and availability in rocky desertification mountainous regions Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:我国西南岩溶区石漠化严重，植被覆盖率低，土壤贫瘠。植被恢复作为一项重要的生态治理措施，在提高土壤养分有效性，增加生物多样性和改善生态环境等方面发挥着极其重要的作用。以广西马山县经过8年植被恢复的4种样地类型（降香黄檀纯林；顶果木纯林；降香黄檀/顶果木混交林；相邻的天然灌草丛作为对照组）为研究对象，探讨了引进固氮树种（降香黄檀和顶果木）及其种植模式对石漠化山区土壤磷素转化及其有效性的影响。研究结果表明：（1）降香黄檀/顶果木混交林土壤的有机质（SOM）、硝态氮（NO3--N）、有效磷（AP）、微生物生物量碳（MBC）、微生物生物量氮（MBN）和微生物生物量磷（MBP）含量均显著高于对照（P<0.05）；降香黄檀/顶果木混交林、顶果木纯林和降香黄檀纯林的全磷（TP）相比于对照组更易转化为AP，其中以降香黄檀/顶果木混交林的效果最佳。（2）相关分析结果表明，土壤NH4+-N、NO3--N和MBN与AP分别呈显著线性正相关（P<0.05），MBN与MBP呈极显著线性正相关（P<0.01）。（3）引种降香黄檀和顶果木后，各林分的土壤无机磷组分均发生变化，其中降香黄檀/顶果木混交林和顶果木纯林的各种无机磷含量显著增加（P<0.05）。（4）最后，冗余分析表明MBP、SOM和MBN可能是影响土壤无机磷组分变化的最主要因素（P<0.05）。研究表明降香黄檀和顶果木在一定程度上能改善石漠化山区土壤的养分状况和提高土壤磷的有效性，其中以二者混交种植模式的效果最显著，以期为珍贵固氮树种在石漠化生态恢复与重建中的推广应用提供理论依据和实践支持。 Abstract:Rocky desertification is serious in karst areas in southwest China, with low vegetation coverage and poor soil. As an important ecological management measure, vegetation restoration plays an extremely important role in improving the availability of soil nutrients, increasing biodiversity, and improving the ecological environment. In this study, four types of site (the pure plantation of Dalbergia odorifera; the pure plantation of Acricarpus fraxinifolius; the mixed plantation of D. odorifera and A. fraxinifolius; the adjacent natural weed field as the control) in Mashan, Guangxi were selected as the research objects after 8 years of vegetation restoration. The effects of introducing N2-fixing tree species (D. odorifera and A. fraxinifolius) and their planting patterns on the soil phosphorus transformation and availability in rocky desertification mountainous regions were discussed. The results showed that:(1) the contents of soil organic matter (SOM), nitrate nitrogen (NO3--N), available phosphorus (AP), soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN), and soil microbial biomass phosphorus (MBP) in the mixed plantation of D. odorifera and A. fraxinifolius were significantly higher than those of the control (P<0.05). The total phosphorus (TP) of the mixed plantation of D. odorifera and A. fraxinifolius, the pure plantation of A. fraxinifolius and the pure plantation of D. odorifera could be easily transformed into AP than control, among which the mixed plantation of D. odorifera and A. fraxinifolius had the best effect. (2) The results of correlation analysis showed that NH4+-N, NO3--N, and MBN had significant linear positive correlation with AP respectively (P<0.05), while MBN and MBP had extremely significant linear positive correlation (P<0.01). (3) After introducing D. odorifera and A. fraxinifolius, the soil inorganic phosphorus fractions in all sites changed, and the contents of various inorganic phosphorus in the mixed plantation of D. odorifera and A. fraxinifolius and the pure plantation of A. fraxinifolius increased significantly (P<0.05). (4) Finally, the redundancy analysis (RDA) indicated that MBP, SOM, and MBN would be the main factors affecting the changes of soil inorganic phosphorus fractions (P<0.05). Overall, D. odorifera and A. fraxinifolius could improve soil nutrient and phosphorus availability in rocky desertification mountain regions to a certain extent, among which the mixed planting pattern (the mixed plantation of D. odorifera and A. fraxinifolius) had the most significant effect. The purpose of the study could provide theoretical basis and practical support for the application of N2-fixing tree species in the ecological restoration and reconstruction of rocky desertification. 参考文献 相似文献 引证文献

Land-Use Change Affects Inorganic Phosphorus Fractions in Sandy Soils from the Northeastern Cerrado, Brazil

Land-Use Change Affects Inorganic Phosphorus Fractions in Sandy Soils from the Northeastern Cerrado, Brazil

Dynamics of soil inorganic phosphorus fractions at aggregate scales in a chronosequence of Chinese fir plantations

Dynamics of soil inorganic phosphorus fractions at aggregate scales in a chronosequence of Chinese fir plantations

Effects of Spartina alterniflora Invasion on Soil Phosphorus Forms in the Jiaozhou Bay Wetland

To investigate the effects of Spartina alterniflora invasion on soil phosphorus(P) cycling in coastal wetlands, we selected a S. alterniflora zone(SA zone) and mudflat zone(MF zone) in the Jiaozhou Bay as the target areas for the study. The variability of total phosphorus(TP), inorganic phosphorus(IP), and their component contents in wetland soils after S. alterniflora invasion and their influencing factors was evaluated. The results showed that the average contents of TP(472.70 mg·kg-1) and IP(239.00 mg·kg-1) in the soils were significantly higher than those of TP(386.19 mg·kg-1) and IP(212.68 mg·kg-1) in the pre-invasion area, with an increase of 22.40% and 12.38%, respectively. The IP fractions in the study area were dominated by calcium-phosphorus(Ca-P) and iron-phosphorus(Fe-P), accounting for 45%-61% and 31%-49% of IP, respectively. The Ca-P content of the soil in the 10-30 cm layer decreased significantly(P<0.05) after S. alterniflora invasion, which was especially significant in July. The Fe-P content increased significantly(P<0.05); in the 0-40 cm soil layer, Fe-P was higher than that in the 40-60 cm layer(P<0.05), and showed significant enrichment in the 10-40 cm soil in July. The structural equation model showed that organic matter(OM) had a significant positive effect on TP and Fe-P after S. alterniflora invasion(P<0.01), and the normalized path coefficients were 0.775 and 0.724, respectively. Fe-P had a significant negative effect on Ca-P after invasion(P<0.01) with a normalised throughput coefficient of -0.435. The study found that S. alterniflora invasion generally increased wetland soil P content, while promoting the conversion of Ca-P to Fe-P, improving wetland P bioavailability.

Unveiling the role of sediments in phosphorus removal in pilot-scale constructed wetlands for swine wastewater treatment

The accumulation rate, fractions, and sorption capacity of phosphorus in sediments determine the removal efficiency and service life of constructed wetlands (CWs). Nine pilot-scale three-stage surface flow CWs were constructed to treat three loading rates of lagoon-pretreated swine wastewater, and surface sediment samples at initial and one-year treatment were collected to analyze the phosphorus fractions and sorption capacity. After one-year treatment, concentration of total phosphorus (TP) in sediments increased for high loading rates of wastewater, but remained stable for low loading rates. The annual accumulation rate of TP in sediments (Ma) was −43–445 mg kg−1 yr−1 at surface loading rate (SLR) of 36–355 g P m−2 yr−1. Their association could be described well using a sigmoid model, i.e., Ma = −23 + 538/(1 + exp.(−(SLR–262)/48)) (R2adj = 0.897, RMSE = 40.8, p < 0.01), indicating that the phosphorus accumulation rates in sediments were loading rate-dependent. The sum of inorganic phosphorus fractions contributed to 80–100% of the TP concentration, and accumulation of aluminum-bound phosphorus (AlP) and iron-bound phosphorus (FeP) was responsible for variability of TP concentration in sediments. Phosphorus sorption capacity of CW1 sediments increased by 1.3–1.8 times, attributed to increased pH, and concentrations of ammonium oxalate-extractable aluminum and iron in sediments due to the wastewater input. Selecting iron and aluminum-rich materials preferentially as substrates and regulating the ratio of metal ions to phosphorus in wastewater should be alternative enhancement strategies of CWs for phosphorus removal.

Phosphorus forms and distributions in soils under selected land use practices at the Federal University of Agriculture, Abeokuta, Ogun State, Nigeria

The forms and distributions of phosphorus were determined for four different land use practices in Federal University of Agriculture, Abeokuta, with the aim of evaluating the effects of land use and soil depth on soil physical and chemical properties, forms and distributions of phosphorus. The study was a 4×2 factorial experiment laid out in a Randomized Complete Block Design. Factor 1 was four different land use practices (Gmelina arborea, Tectona grandis, Leucaena leucocephala plantations and secondary forest), and Factor 2 was soil samples collected from two soil depths (0-30cm and 30-60cm). The soil pH, electrical conductivity, exchangeable bases (Na, K, Mg and Ca), particle size, organic carbon, total nitrogen, total phosphorus, inorganic phosphorus fractions (Al-P, Fe-P and Al-P) and available phosphorus analyses were carried out using standard procedures. Data collected from the laboratory analysis were subjected to two-way Analysis of Variance while the means among the treatments were separated using Duncan Multiple Range Test. The results showed that the soils had low total and available P contents. The soil under Leucaena leucocephala plantation had the highest total phosphorus (111.05mg kg-1), followed by Tectona grandis (97.63mgn kg-1), Gmelina arborea (96.41mg kg-1) and secondary forest (83.63mg kg-1). Total P decreased with depths (0-30cm and 30-60cm). Inorganic P-fractions were greatly influenced by soil properties such as soil pH, soil electrical conductivity, organic carbon, and soil particle size. The inorganic phosphorus fractions of the soils in all study area occurred generally in the following sequential order; Fe-P&gt;Ca-P&gt;Al-P. The highest inorganic phosphorus recorded in all in the study area was Fe-P, followed by Ca-P and Al-P. Al-P had the lowest content between the depths examined. Lower nutrient concentrations in soils under secondary forest within the depths were due to lower organic matter content, higher nutrient demand, nutrient immobilization by tree species and other flora present. P fractionation investigations are therefore recommended in soils under indigenous species plantation in order to provide adequate understanding of P status in the soils and fertilizer recommendation so as to improve productivity.

Effect of Phosphorus Solubilizing Bacteria on Soil Available Phosphorus and Growth and Yield of Sugarcane

Phosphorus solubilizing bacteria (PSB) can increase soil phosphorus (P) availability and improve plant growth, yield, and phosphorus content of several crops. The experiment was conducted to evaluate the effect of PSB on soil available phosphorus, growth, and yield of sugarcane at field conditions. Kosakonia radicincitans (PSB1) and Bacillus subtilis (PSB2) were applied with two different sources of phosphorus fertilizers: Di-ammonium phosphate (DAP) and rock phosphate (RP). The application of PSB with phosphorus fertilizers enhanced the yield from 17.03 to 38.42 % over no application of fertilizer. It also increased the percentage of commercial cane sugar percent (CCS %) from 4.8 to 19.96 % over control. The application of PSB2 with DAP showed effective results in available phosphorus content in the soil and yield of sugarcane. The PSB population and the available phosphorus contents were higher in treatments when phosphorus was given partly through RP and DAP than the control. The application of phosphorus fertilizer and PSB increased phosphorus fractions in the soil. The addition of phosphorus fertilizer to soil increased all the inorganic phosphorus fractions in soil. The treatments with PSB resulted in statistical differences in total phosphorus concentrations in the soil. The application of PSB with RP (T6, T7, and T8) showed the highest weight among the treatment at the harvesting time. The yield of sugarcane was highest in the application of PSB2 with either DAP or RP (T4 and T7). HIGHLIGHTS Evaluate the effect of Phosphate Solubilizing Bacteria (PSB) (Kosakonia radicincitans and Bacillus subtills) comminated with two different phosphorus (di-ammonium phosphate (DAP) and rock phosphate (RP) fertilizers on the changes in the soil available phosphorus level and sugarcane growth at Sa Kaeo Province, Thailand The application of P fertilizer and PSB can increase the inorganic P fractions in the soil and increased the cane yield over NPK without PSB The PSB application either single or co-inoculation of PSBs increased the average cane more than 13 % to over control

Long-Term Application of Chemical and Organic Fertilizers over 35 Years Differentially Affects Interannual Variation in Soil Inorganic Phosphorus Fractions in Acidic Paddy Soil

Long-Term Application of Chemical and Organic Fertilizers over 35 Years Differentially Affects Interannual Variation in Soil Inorganic Phosphorus Fractions in Acidic Paddy Soil

Biochar Alters Inorganic Phosphorus Fractions in Tobacco-growing Soil

It is important to consider tobacco stalks as sources of biochar and improve the soil quality of tobacco-producing areas in Southwest China. Therefore, in this study, we investigated the effects of biochar produced from tobacco stalks on soil inorganic phosphorus (P) fractions in bulk and rhizosphere soils. We also analyzed the factors influencing these effects in tobacco-planting fields. Biochar was applied to two experimental fields in Heishi and Qianxi in Bijie City, Guizhou Province in China, at application rates of 0, 5, 20, and 40 t ha−1. Subsequently, the soil inorganic P (Pi) fractions, pH, and exchangeable and hydrolytic acidities were analyzed, while the factors influencing the soil Pi fractions were determined by redundancy analysis (RDA). The results indicated that the biochar application rate, experimental site, and tobacco roots all affected the soil Pi fractions. Aluminum-phosphate (Al-P), iron-phosphate (Fe-P), and occluded-phosphate (O-P) levels in the bulk soil had significantly increased with biochar application in the Qianxi site. Meanwhile, there was a reduction in Al-P, Fe-P, and O-P levels in the rhizosphere soil in the Heishi site but not in the Qianxi site. The calcium-phosphate (Ca-P) levels in the soil were also greatly reduced in the Heishi site, while in the Qianxi site, the Ca-P levels were relatively constant in the bulk soil and increased in the rhizosphere soil. Furthermore, the exchangeable and hydrolytic acidities decreased with increasing biochar application. Soil Pi fractions varied according to biochar application rate and experimental site. We found that 20 t ha−1 was an appropriate biochar application rate for enhancing soil Pi fractions. In addition, the soil Pi fractions were negatively correlated with the dissolved organic carbon (DOC) content but were positively correlated with the hydrolytic acidity.

Elucidating the effect and interaction mechanism of fulvic acid and nitrogen fertilizer application on phosphorus availability in a salt-affected soil

The present study was performed to investigate the effects of the interaction of fulvic acid (FA) with different amounts of nitrogen fertilizer (N) on soil phosphorus availability and transformation in a salt-affected soil and to obtain the direct and indirect relationships between inorganic phosphorus (Pi) fractions and Olsen-P. An incubation experiment was conducted to evaluate the effects of nitrogen addition (215, 183, and 151 mg kg-1, referred as N100, N85, and N70), fulvic acid addition (30 and 60 mg kg-1, referred as F1 and F2), and their interactions on phosphorus availability (based on soil Olsen-P and inorganic P fractions). The results indicated that the application of N100 significantly reduced the release and availability of phosphorus (P). However, the phosphorus recovery (PR) as Olsen-P was significantly enhanced in the N100F1 and N100F2 treatments. The P kinetics was best described by the power function model. Moreover, labile Ca2-P and Ca8-P contents decreased as N application rate increased. Combined application of FA and fertilizer N increased the percentage of Ca2-P and decreased the percentage of Ca10-P at the end of the incubation period. According to the correlation analysis and path analysis, the direct effects of Ca2-P, Fe-P, and O-P on Olsen-P were significant after 112 days of incubation (P<0.05). The indirect effects of Ca2-P (R21Py1 = 0.57) and Fe-P (R24Py4 = 0.19) were essential contributors to the correlation between Ca8-P and Olsen-P. Additionally, the indirect effect of Ca8-P (R41Py1 = 0.53) contributed significantly to the correlation between Fe-P and Olsen-P. In conclusion, our results show that the availability of phosphorus can be improved by reducing the amount of nitrogen fertilizer applied in salt-affected soils. Integrating FA and inorganic N fertilizer enhances the release and availability of phosphorus, when excessive amounts of N fertilizers are applied to salt-affected soils.

Distribution of cationic micronutrients in relation to different soil properties and fractions of phosphorus in coastal soils of West Bengal

This study aims to establish the relationships between cationic micronutrients and soil properties in 52 surface soils (0-15 cm) collected from coastal areas of West Bengal, India. The initial status of cationic micronutrients and their relationship with soil properties were also studied. The DTPA-extractable micronutrients namely, zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) ranged from 0.03-2.65, 5.59-68.4, 10.8-49.9 and 0.69-3.71 mg kg-1 with mean values of 0.65, 27.3, 33.7 and 1.71 mg kg-1, respectively. Different soil properties namely, pH, organic carbon (OC), electric conductivity (EC), cation exchange capacity (CEC), Olsen-P and different inorganic phosphorus (P) fractions were determined. Results showed a significant negative correlations between pH and Zn, Fe, Mn and Cu, whereas OC showed positive and significant correlations with Zn, Fe and Cu and non-significant positive correlations with Mn. The EC showed the non-significant negative correlations with Fe and Cu and non-significant positive correlation with Zn and Mn. Olsen-P showed the non-significant positive correlations with Zn, Fe and Cu and non-significant negative correlations with Mn. Results also revealed that CEC and EC enhanced the loosely bound-P explaining 47% of total variability. Loosely bound-P and reductant soluble-P showed the significant negative correlations with all the micronutrients. However, Al-P showed the significant positive correlations with Zn, Fe and Cu.

Seasonal variation characteristics and release potential of phosphorus in sediments: a case study of the Qiuxi River, a typical diffuse source pollution river in southwestern China

To better control and manage phosphorus (P) in the aquatic environment of the Qiuxi River, a typical river severely influenced by anthropogenic activities in southwest China, the morphological characteristics and the release potential of P in sediments during different water seasons were determined. The overlying water and sediment samples were collected from the Qiuxi River in the normal-water season (NWS), low-water season (LWS), and high-water season (HWS), and physicochemical properties were quantified. Total phosphorus (TP) in sediment and the inorganic phosphorus (Pi) fraction were analyzed using the standard measures technology (SMT) procedure, and organic phosphorus (Po) was further determined to be labile Po (LOP), moderately labile Po (MLOP), or non-labile Po (NLOP). The release potential of P from the sediments was studied by experiments under simulated conditions. The results showed that P pollution in the Qiuxi River was the most serious during the LWS, with mean TP concentrations in the sediment of 854.6 mg kg−1, and the release risk of the sediment P was also highest during this water season. The variation in P concentration was significantly influenced by the discharge of domestic sewage, agricultural diffusion, flow rate, and OM. The concentrations of P fractions varied with water season, but Pi was constantly higher than Po. HCl-extractable Pi (HCl-Pi) accounted for most of the P in the sediments, which was related to its characteristics and the geographical location of the Qiuxi River. The maximum P release (Rmax) was 25.9 mg kg−1 in the LWS and 15.3 mg kg−1 in the HWS, which were positively correlated with the TP (r2 = 0.848, p < 0.01) and OM (r2 = 0.847, p < 0.01) concentrations in the sediments and explained why the release risk of the sediment P in the LWS was higher than that in the HWS. Phosphorus pollution and the P release potential in the sediments of the Qiuxi River were most severe in the LWS, so more effective measures to restrain the release of P should be taken during the LWS. Moreover, OM in sediments should be given more attention owing to its significantly positive correlation with the risk of P release.

Dynamics of phosphorus fractions and potential bioavailability along soil profiles from seasonal-flooding wetlands in a Chinese estuary.

Soil phosphorus fractions in wetland ecosystems have received increasing attention due to its high eutrophication risks. Soil samples were collected to 40 cm depth in three sampling seasons to investigate the seasonal dynamics of organic and inorganic phosphorus fractions, bioavailability, and relationship between those and soil properties in a seasonal-flooding wetland in the Yellow River Estuary. The results showed that inorganic phosphorus (IP) and organic phosphorus (OP) contents exhibited much higher levels in the top 10cm soils, and declined along soil profiles in spring. IP kept constant along soil profiles in fall, while OP decreased in summer and fall. They were greatly affected by water content (WC), pH, Cl-/SO42-, soil organic matter (SOM), and electrical conductivity (EC). Middle labile organic phosphorus (MLOP) and non-labile organic phosphorus (NLOP) accounted for higher percentages of total OP in summer and fall respectively than labile organic phosphorus (LOP) in spring. MLOP and NLOP levels showed a decrease along soil profiles in spring and in spring/fall, respectively, while NLOP significantly increased with depth in summer. Ca-P was the dominant IP fraction in all soils in three sampling seasons, declined with depth in spring/fall and increased in summer. Comparatively, soluble/loosely-P(S/L-P) generally decreased with depth along soil profiles in three sampling seasons. And residual P (Res-P) kept little change with depth in spring. Fe/Al-P levels decreased firstly and then increased with depth in spring and summer. Available phosphorus and potential bioavailable phosphorus contents decreased with depth in spring and summer not in fall, and had a strong significant positive correlation with WC and SOM. Alkaline phosphatase not acid phosphatase was the key factor influencing soil MLOP levels. Generally, the fractions and bioavailability of phosphorus as well as phosphatase in this region were affected by soil depth, sampling seasons, and soil properties (e.g., WC, pH, Cl-/SO42-, SOM, and EC).

Relationship between some soil characteristics and contribution on available phosphorus of inorganic phosphorus fractions in calcareous soils

Aims: The aim of this study is to determine the amount and distribution of inorganic phosphorus fractions in soil profiles classified as Mollisol and Entisol, which are common in the Eastern Anatolian region, and to determine their soil properties and their relationships with each other, and to evaluate the contribution of inorganic phosphorus fractions to available soil phosphorus (Olsen-P).Methods and Results: The total amount of phosphorus in these soils with calcareous and slightly alkaline reactions has been determined as 280-1713 mg kg-1 and an average of 713 mg kg-1. Ca-P’, which make up an average of 80.9% of the total phosphorus and which are determined as the first phosphorus fraction in these soils, have been determined between 163.2-951.1 mg kg-1. The occluded phosphates (CDB-P), which rank second in quantity in these soils after Ca-P2, are between 2.07-105.6 mg kg-1, and thirdly, phosphates (CB-P) held by carbonates during the first extraction are 0.76-52.83 mg kg-1. In the fourth and last row, nonoccluded aluminum and iron phosphates (Al-P + Fe-P) were found as the least amount of phosphorus fractions in these soils between 0.09-5.0 mg kg-1.Conclusions: In summary, the order of inorganic phosphorus fractions in these soils was determined as Ca-P&amp;gt; CDB-P&amp;gt; CB-P&amp;gt; Al-P+Fe-P. Significance and Impact of the Study: It was determined that two fractions contribute to phosphorus (Olsen-P), nonoccluded aluminum and iron phosphates (AI-P + Fe-P) and occluded phosphates (CDB-P) in these soils.

Biochar and phosphorus fertilization improved soil quality and inorganic phosphorus fractions in saline-alkaline soils

ABSTRACT The establishment of high-yielding agricultural production systems is severely restricted by low soil organic carbon (SOC) and high Na+ concentration in saline-alkaline soils. In order to confirm the effects of biochar and phosphorus (P) fertilization on SOC sequestration, soil physical structure and inorganic P (Pi) fractions, as well as optimize the amount of P fertilizer, a field experiment was designed with two factors: with biochar at 0 (C0), 1% (C1) and 3% (C2); with P at 0 (P0), 64 (P1) and 128 kg ha−1 (P2). The results indicated that biochar input enhanced SOC, however, the effect of P application on SOC and soil physical structure were negligible. Compared to C0, SOC was increased by 98–113% for C1 and 180–195% for C2. Due to the SOC enhancement and reduction of soil Na+ concentration, biochar input decreased ρb, increased MWD and WSMA. For Pi fractions, soil Olsen-P, Ca2-P, Ca8-P, Fe-P and Al-P were increased, mainly due to the direct supply, retention and the improvement of biological availability. Overall, C2P1 was the most efficiency treatment to enhance SOC, improve soil physical structure, and C2P2 avail to increase the supply capacity of soil P, but had no significant difference with that in C2P1.

Responses of organic and inorganic phosphorus fractions in brown earth to successive maize stover and biochar application: a 5-year field experiment in Northeast China

To compare the effects of maize stover and its biochar on soil P fractions and investigate the effects of different stover incorporation practices (direct return or pyrolysis) on the transformation of soil P fractions after a long-term field experiment. Total P, Olsen-P, inorganic P fractions, and organic P fractions were analyzed via a 5-year field experiment growing maize. The treatments were as follows: CK0 (no fertilizer application or amendment), CK (application of mineral NPK fertilizer), ST (application of maize stover at 7.5 t ha−1 along with mineral NPK fertilizer), and BC (application of biochar at 2.63 t ha−1, a rate approximately equivalent to a maize stover biomass of 7.5 t ha−1; the biochar was charred according to a 35% output ratio in the factory). All treatments received N mineral fertilizer at 120 kg N ha−1, P mineral fertilizer at 26 kg P ha−1, and K mineral fertilizer at 50 kg K ha−1 annually. Relative to the initial fractions in 2013, biochar generally increased the inorganic P fractions (Ca8-P, Ca10-P, Al-P, and Fe-P), and maize stover generally increased the organic P fractions (MLOP, MROP, and HROP), while both maize stover and its biochar significantly decreased O-P in the soil. After 5 years (in 2017), relative to CK treatment, amendment with maize stover and its biochar increased total P and decreased Olsen-P. The total inorganic P, Ca8-P, and Fe-P were significantly increased by biochar. Ca2-P and O-P were significantly decreased by maize stover and its biochar. Total organic P was increased with maize stover and biochar amendment. LOP and HROP were significantly increased under biochar application, and all organic P fractions were significantly increased under maize stover amendment. The application of maize stover and its biochar affected both organic and inorganic phosphorus fractions; biochar had a more advantageous effect on the soil inorganic P fractions, while stover had a greater effect on the content of organic P fractions.

Phosphate fertilizer addition increases the movement distance and content of the acid soil inorganic phosphorus fractions at green manure microsites

To investigate the movement and content of the acid soil Pi fractions at different distances from the green manure (GM) application site at a GM microsite, an incubation experiment was conducted. Stylosanthes GM (10 or 40 ton/ha) was applied with or without phosphate fertilizer (monocalcium phosphate, MCP) at a concentration of 44 kg/ha P, which was laid on the surface in soil cylinders. The GM/fertilizer and soil were incubated for 14 and 28 d. The results indicated the movement distance and content of the Pi fractions (Al-, Fe-, and Ca-associated Pi as well as occluded P) in the acid soil microsite were significantly increased after the addition of MCP; however, the movement distances of the Pi fractions were all less than 3 mm after incubation for 28 d. This information will improve the efficiency of combined P and GM use and decrease the environmental load due to P pollution caused by GM and phosphate fertilizer.

Studies on forms and distribution of phosphorus in the different soil series of a sub-watershed in northern dry zone of Karnataka

A study was undertaken during 2018-19 in the soils of Babaleshwar East sub-watershed of Vijayapura district which belongs to Northern dry zone of Karnataka to study the forms of phosphorus and their relationship with soil properties. Thirteen soil series were identified in the study area, one representative soil profile was selected from each soil series and horizon-wise soil samples were analyzed for different fractions of phosphorus. Saloid-P, Fe-P, Al-P, Org-P and available-P decreased with profile depth in all the soil series and were positively and significantly correlated with organic carbon. Reductant soluble-P, occluded -P and Ca-P and total-P did not follow definite trend in most of the soil series. Occluded-P was negatively correlated with free CaCO3, whereas Ca-P and total-P were significantly and positively correlated with free CaCO3. Fe-P, Al-P and reductant soluble -P significantly and negatively correlated with pH and free CaCO3. Among the inorganic phosphorus fraction Ca-P was dominant as the soils are under semi-arid region.

Exogenous phosphorus compounds interact with nitrogen availability to regulate dynamics of soil inorganic phosphorus fractions in a meadow steppe

Abstract. Here we investigated the effects of P compounds (KH2PO4 and Ca(H2PO4)2) with different addition rates of 0, 20, 40, 60, 80, and 100 kg P ha−1 yr−1 and NH4NO3 addition (0 and 100 kg N ha−1 yr−1) on soil labile inorganic phosphorus (IP) (dicalcium phosphate, Ca2-P), moderate-cycling IP, and recalcitrant IP fractions in a calcareous grassland of northeastern China. Soil moderate-cycling IP fractions, not readily available to plants but transforming into soil-available P quickly, include variscite (Al-P), strengite (Fe-P) and octacalcium phosphate (Ca8-P); recalcitrant IP fractions include hydroxylapatite (Ca10-P) and occluded P (O-P). Soil labile and moderate-cycling IP fractions and total P significantly increased with increasing P addition rates, with higher concentrations detected for KH2PO4 than for Ca(H2PO4)2 addition. Combined N and P treatments showed lower soil labile IP and moderate-cycling IP fractions compared to ambient N conditions, due to enhanced plant productivity. Moderate-cycling IP was mainly regulated by P addition and plant P uptake to further enhance labile IP and total P concentrations with KH2PO4 and Ca(H2PO4)2 addition. Soil labile IP was also directly and negatively affected by soil pH and plant P uptake with Ca(H2PO4)2 addition. Ca(H2PO4)2 addition significantly increased the soil recalcitrant IP (Ca10-P) fraction, while KH2PO4 addition showed no impact on it. A significant positive correlation was detected between soil labile IP, moderate-cycling IP fractions and soil Olsen-P which illustrated that labile IP and moderate-cycling IP fractions were important sources for soil-available P. Our results suggest that moderate-cycling IP fractions are essential for grassland P biogeochemical cycling and the chemical form of P fertilizer should be considered during fertilization management for maintaining soil-available P.

Impact of Rice-Catfish/Shrimp Co-culture on Nutrients Fluxes Across Sediment-Water Interface in Intensive Aquaculture Ponds

Exchange of nitrogen and phosphorus across sediment-water interface plays an important role in the management of nutrient recycling in the aquaculture pond. In this study, a plot experiment was conducted to study the effect of rice-catfish/shrimp co-culture on the micro-profile of oxygen (O2), pH and nutrient exchange across sediment-water interface in the intensive culture ponds. The results showed that rice-catfish co-culture increased the concentration and penetrating depth of O2, but decreased the pH value across the sediment-water interface, compared with catfish monoculture. Additional rice cultivation significantly reduced the flux rates of ammonium (NH4+) and nitrate (NO3−) across sediment-water interface in the catfish and shrimp ponds. The flux rates of NO2− and soluble phosphorus (PO43−) showed no significant difference between rice-catfish/shrimp co-culture ponds and catfish/shrimp monoculture ponds. Rice only affected the dissolved inorganic nitrogen and phosphorus fractions in the sediment. The concentrations of NH4+ were significantly lower in the sediment of co-culture ponds than in the monoculture ponds. Additional rice cultivation also significantly reduced the content and percentage of dissolved inorganic phosphorus in the sediment of catfish ponds.