Nitric Acid Oxidation for Improvement of a Chinese Lignite as Soil Conditioner

Oxidation is known commonly to enhance humic acid (HAs) contents of coal, but in China, most humic substances are used directly as soil conditioners or applied in combination with fertilizers without oxidation. Therefore, we investigated the impact of nitric acid (HNO₃) oxidation on the characteristics of HAs derived from a Chinese lignite. The results showed that total HA content was increased by HNO₃ oxidation, thus consequently increasing its cation exchange capacity and moderate humification. Besides, HAs extracted from oxidized lignite were richer in oxygen-containing functional groups with smaller molecular size than natural lignite. Compared with natural lignite, retention capacities of nitrogen and potassium by oxidized lignite were significantly greater. However, phosphorus-retention capacity was decreased to near zero, which might enhance the availability of phosphorus in soil. In general, optimum HNO₃ oxidation had favorable effects on lignite and improved its characteristics for use as a soil conditioner.     

Effect of a Chemical Modified Urea Fertilizer on Soil Quality: Soil Microbial Populations Around Corn Roots

Slow‐release nitrogen (N) fertilizers are used to increase N‐use efficiency and extend N availability over a plant‐growing season. One formula of this fertilizer commonly used in turf and horticultural crops is methylene–urea–triazone. After this compound is applied in the soil, it is subject to bacterial degradation and becomes available for uptake by plants. The objective of this work is to elucidate the application of methylene–urea–triazone in the soil microbial population as well as effects on soil quality. Zea mays was planted in a silty loam soil. Urea and methylene–urea–triazone were incorporated into the soil. Two weeks and 6 weeks after inoculation, soil samples were collected and used to inoculate agar plates and for DNA extraction. Bacterial colony morphology was examined. Denaturing gradient gel electrophoresis (DGGE) was performed with the polymerase chain reaction (PCR) amplicons from the internal transcribed spacer (ITS) of the rRNA gene cluster. The Shannon Wiener index was determined for colony morphology and DGGE bands. There was a difference between urea and the slow‐release fertilizer on both plant responses and bacterial diversity. Although for the first 2 weeks DGGE did not show any difference in bacterial diversity, after 6 weeks, differences in the composition of the bacterial community were observed. There were concomitant effects on plant growth and microorganism population and diversity, probably reflecting changes in the richness and in the eveness of the bacterial population in the rhizosphere caused by the fertilizers. Therefore, both soil microorganisms and plant growth respond to environmental changes over time.     

Ecotoxicological Assessment of Chemical Fumigants Utilising an Earthworm (<Emphasis Type="Italic">Eisenia andrei</Emphasis>) Bioassay and Soil Microbial Communities

Fumigation is an important crop protection practice employed to control soil pathogens and diseases. Metham sodium and cadusafos are two commonly used soil fumigants for this purpose. However, little information is available on their effects on non-target soil organisms. The aim of the study was to determine the ecotoxicity of these chemical fumigants on earthworms (organismal responses and DNA damage) and soil microbial communities. Changes in soil microbial community function and structure were evaluated by means of Biolog? Ecoplates and phospholipid fatty acid (PLFA) analyses, respectively. Both fumigants had a significant (p < 0.05) negative impact on all earthworm endpoints. Earthworms did not reproduce; biomass was affected negatively and manifested significant DNA damage with metham sodium causing more pronounced effects in comparison to cadusafos. The fumigants had an inhibitory effect on microbial growth. No lasting effects were observed in the community structure but cadusafos had a pronounced effect on the microbial community functional diversity. Metham sodium and cadusafos had varying effects on earthworm and microbial endpoints. This illustrates the importance of using different bioindicators to get a better understanding of the overall effects on the soil ecosystem.     

Effects of soil amendments on antimony uptake by wheat

Purpose

Environmental chemistry of antimony (Sb) is still largely unknown. Many questions remain about its availability to plants and effects of fertilizers on mobility of Sb in the rhizosphere soil. In this work, we focused on the following problems: (1) uptake of Sb by wheat seedlings grown in soil enriched with this metalloid and (2) impact of soil amendments on the plant growth, Sb uptake from soil, and its transfer from roots to upper plant parts.

Materials and methods

To obtain further information on the possible transfer of Sb into plants, greenhouse pot experiments were carried out. Soil was spiked with 15 mg kg^?1 of Sb and amended with either chicken manure or natural growth stimulator Energen. Wheat Triticum aestivum L. seedlings were grown in the soil during 17 days. Plants together with rhizosphere soil were collected several times in the course of the experiment. The ICP-OES and ICP-MS techniques were applied to determine the concentrations of macro- and trace elements in the plant and soil material.

Results and discussion

Growth of wheat seedlings in Sb-spiked soil resulted in Sb accumulation in roots and leaves of the plants. Energen and especially chicken manure were capable of stimulating transfer of Sb to more mobile and, as a consequence, more available to the plants form, thus enhancing both uptake of Sb from soil and its transfer from roots to upper plant parts. The accumulation of Sb by plants led to a decrease of Sb concentration in the rhizosphere soil with time, and the most significant decrease was observed after amendment of soil with fertilizers.

Conclusions

Fertilizers may be used to increase phytoextraction of Sb and its removal from contaminated soils. However, such an amendment of soil should be done with caution in order to exclude or at least reduce the negative effects on plants.     

Effect of Soil Fertilizer,Foliar Fertilizer,and Growth Regulator Application on Milk Thistle Development,Seed Yield,and Silymarin Content

Abstract

An important consideration for milk thistle (Silybum marianum L.) cultivation is regulating development to lengthen the reproductive stage and increase seed yield with high silymarin content. The treatment of milk thistle with foliar fertilizers and growth regulators—thidiazuron (Dropp^®), 2,3,5‐triiodobenzoic acid (Tiba^®), mepiquat chloride (Pix^®), and prohexadione‐Ca (Regalis^®)—resulted in an increase in the proportion of mature flower heads. Highest seed yield was observed in plants treated with Pix^® and mineral soil fertilization, whereas in plants treated with foliar fertilizers, highest yields were observed with Pix^® and Regalis^®. The highest content of silymarin was found in plants treated with Dropp^® and foliar fertilizer. Generally, treatment of milk thistle with plant‐growth regulators in combination with soil or foliar mineral fertilizers increased the total amount of silymarin by increasing seed yield per hectare.     

Short and long-term effects of elevated CO2 on Lolium perenne rhizodeposition and its consequences on soil organic matter turnover and plant N yield

It is still unclear whether elevated CO₂ increases plant root exudation and consequently affects the soil microbial biomass. The effects of elevated CO₂ on the fate of the C and nitrogen (N) contained in old soil organic matter pools is also unclear. In this study the short and long-term effects of elevated CO₂ on C and N pools and fluxes were assessed by growing isolated plants of ryegrass (Lolium perenne) in glasshouses at elevated and ambient atmospheric CO₂ and using soil from the New Zealand FACE site that had >4 years exposure to CO₂ enrichment. Using ¹⁴CO₂ pulse labelling, the effects of elevated CO₂ on C allocation within the plant-soil system were studied. Under elevated CO₂ more root derived C was found in the soil and in the microbial biomass 48 h after labelling. The increased availability of substrate significantly stimulated soil microbial growth and acted as priming effect, enhancing native soil organic matter decomposition regardless of the mineral N supply. Despite indications of faster N cycling in soil under elevated CO₂, N availability to plants stayed unchanged. Soil previously exposed to elevated CO₂ exhibited a higher N cycling rate but again there was no effect on plant N uptake. With respect to the difficulties of extrapolating glasshouse experiment results to the field, we concluded that the accumulation of coarse organic matter observed in the field under elevated CO₂ was probably not created by an imbalance between C and N but was likely to be due to more complex phenomena involving soil mesofauna and/or other nutrients limitations.     

添加生物炭对酸性红壤中玉米生长和氮素利用率的影响

Biochar added to soil can improve crop growth through both direct and indirect effects, particularly in acidic, highly weathered soils in subtropical and tropical regions. However, the mechanisms of biochar improving crop growth are not well understood. The objectives of this study were i） to determine the crop responses to biochar addition and ii） to understand the effect of biochar addition on N use efficiency. Seven acidic red soils varying in texture, p H, and soil nutrient were taken from southern China and subjected to four treatments： zero biochar and fertilizer as a control（CK）, 10 g kg-1biochar（BC）, NPK fertilizers（NPK）, and 10 g kg-1biochar plus NPK fertilizers（BC＋NPK）.15N-labeled fertilizer was used as a tracer to assess N use efficiency. After a 46-d pot experiment,biochar addition increased soil p H and available P, and decreased soil exchangable Al3＋, but did not impact soil availabe N and cation exchange capacity（P 〉 0.05）. The N use efficiency and N retained in the soil were not significantly affected by biochar application except for the soil with the lowest available P（3.81 mg kg-1） and highest exchanageable Al3＋（4.54 cmol kg-1）. Greater maize biomass was observed in all soils amended with biochar compared to soils without biochar（BC vs. CK, BC＋NPK vs. NPK）. This agronomic effect was negatively related to the concentration of soil exchangeable Al3＋（P 〈 0.1）. The results of this study implied that the liming effect of biochar improved plant growth through alleviating Al toxicity and P deficiency, especially in poor acidic red soils.     

聚合果属生物炭引起的咸水灌溉下土壤养分有效性和番茄生长变化

Thermally modified organic materials commonly known as biochar have gained popularity of being used as a soil amendment.Little information, however, is available on the role of biochar in alleviating the negative impacts of saline water on soil productivity and plant growth. This study, therefore, was conducted to investigate the effects of Conocarpus biochar(BC) and organic farm residues(FR) at different application rates of 0.0%(control), 4.0% and 8.0%(weight/weight) on yield and quality of tomatoes grown on a sandy soil under drip irrigation with saline or non-saline water. The availability of P, K, Fe, Mn, Zn and Cu to plants was also investigated. The results demonstrated clearly that addition of BC or FR increased the vegetative growth, yield and quality parameters in all irrigation treatments. It was found that salt stress adversely affected soil productivity, as indicated by the lower vegetative growth and yield components of tomato plants. However, this suppressing effect on the vegetative growth and yield tended to decline with application of FR or BC, especially at the high application rate and in the presence of biochar. Under saline irrigation system, for instance, the total tomato yield increased over the control by 14.0%–43.3% with BC and by 3.9%–35.6% with FR. These could be attributed to enhancement effects of FR or BC on soil properties, as indicated by increases in soil organic matter content and nutrient availability. Therefore, biochar may be effectively used as a soil amendment for enhancing the productivity of salt-affected sandy soils under arid conditions.     

The effect of long-term fertilization with organic or inorganic fertilizers on mycorrhiza-mediated phosphorus uptake in subterranean clover

 A pot experiment was conducted with soil from a long-term (74-year) fertilization field experiment to compare the effects of organic and mineral fertilizers on mycorrhiza formation in clover, and mycorrhiza-mediated plant P uptake. Five treatments were selected from the field experiment representing different forms and levels of P. Mycorrhizal effects on plant growth and P uptake were estimated by comparing plants grown in untreated soil containing indigenous arbuscular mycorrhizal (AM) fungi, with plants grown in pasteurized soil. Short-term versus residual effects of fertilizer/manure were also measured by comparing treatments with or without fertilizers added at the start of the pot experiment. Mycorrhiza formation was greatest in soil that had received no P for 74 years, followed by soil having received 30 or 60 Mg ha^–1 farmyard manure (FYM), and soil having received 25 or 44 kg P ha^–1 in NPK fertilizers. Plant growth and P uptake were severely reduced in the absence of AM fungi for all mineral fertilizer treatments. In contrast, plants growing in soil that had received FYM grew equally well or better when non-mycorrhizal. Recent additions of NK fertilizer and FYM had no effect on mycorrhiza formation, while additions of NPK led to reduced colonization. It thus seems that moderate quantities of FYM have less adverse effects on AM than equivalent amounts of nutrients in NPK fertilizers, a phenomenon that is most likely due to a temporal difference in P availability and its gradual release that balance plant demand. Received: 4 November 1999     

纳米碳对草莓氮素吸收利用及植株生长的影响

以盆栽妙香7号草莓为试材,利用15 N同位素示踪技术探究尿素配施0,2,4,6,8mL纳米碳溶胶(CK、T1、T2、T3)对土壤理化性状、植株氮素吸收利用及生长发育的影响。结果表明:施用纳米碳显著提高了土壤氧化还原电位和土壤脲酶活性;随纳米碳用量的增加处理前期土壤的电导率呈现降低趋势后期呈现增大的趋势。纳米碳的施用促进了草莓植株对氮素的吸收利用,提高了草莓各器官的Ndff值;与对照相比,T1、T2、T3处理草莓植株的氮素利用率分别提高了71.2%,126.8%,98.9%,土壤氮素残留率分别提高了8.2%,16.7%,16.1%,显著减少了氮素的损失。纳米碳的施用不同程度提高了植株叶片的净光合速率、蒸腾速率、气孔导度和叶绿素SPAD值,干物质比对照增加了17.5%,45.8%,32.3%。研究表明,尿素配施纳米碳可改善土壤理化性状,有效吸附土壤中的氮素,提高植株氮素利用率和土壤氮素残留率,减少氮素损失,促进了草莓植株的生长。     

Distribution and turnover of recently fixed photosynthate in ryegrass rhizospheres

The cycling of root-deposited photosynthate (rhizodeposition) through the soil microbial biomass can have profound influences on plant nutrient availability. Currently, our understanding of microbial dynamics associated with rhizosphere carbon (C) flow is limited. We used a ¹³C pulse-chase labeling procedure to examine the flow of photosynthetically fixed ¹³C into the microbial biomass of the bulk and rhizosphere soils of greenhouse-grown annual ryegrass (Lolium multiflorum Lam.). To assess the temporal dynamics of rhizosphere C flow through the microbial biomass, plants were labeled either during the transition between active root growth and rapid shoot growth (Labeling Period 1), or nine days later during the rapid shoot growth stage (Labeling Period 2). Although the distribution of ¹³C in the plant/soil system was similar between the two labeling periods, microbial cycling of rhizodeposition differed between labeling periods. Within 24 h of labeling, more than 10% of the ¹³C retained in the plant/soil system resided in the soil, most of which had already been incorporated into the microbial biomass. From day 1 to day 8, the proportion of ¹³C in soil as microbial biomass declined from about 90 to 35% in rhizosphere soil and from about 80 to 30% in bulk soil. Turnover of ¹³C through the microbial biomass was faster in rhizosphere soil than in bulk soil, and faster in Labeling Period 1 than Labeling Period 2. Our results demonstrate the effectiveness of using ¹³C labeling to examine microbial dynamics and fate of C associated with cycling of rhizodeposition from plants at different phenological stages of growth.     

化肥施用对土壤中重金属生物有效性的影响研究

本研究综述了化学肥料施用对土壤中重金属生物有效性的影响,土壤施肥能改变土壤理化性质如pH、溶液中的离子组成、阳离子交换量等,或直接与重金属离子发生反应,影响重金属的生物有效性。故施用化肥时要考虑到所施化肥的种类和施用量可能会导致重金属的植物可利用性发生改变,从而对人体健康产生影响。     

Phosphorus Availability in Soils Amended with Different Phosphate Fertilizers

Abstract

Accurate measurement and characterization of phosphate rock dissolution are important for a better understanding of phosphorus (P) availability in soils. An incubation study was carried out on two New Zealand topsoils (0–15 cm; high P buffering capacity Craigieburn and low P buffering capacity Templeton) amended with North Carolina phosphate rock (NCPR) and water‐soluble phosphate (WSP) at 218 mg P kg^?1 (equivalent to 60 kg P ha^?1). Isotopic exchange kinetics was carried out after 12 h and 28 days of incubation to characterize P availability. This study showed that sensitivity of capacity factors (r₁/R, n) to explain changes in E_1min values was affected by the P buffering capacity of the soils. The recovery of applied P in the E pool (Rec_inE%) with extended incubation time was similar from the NCPR and WSP treatments (3.1–3.3%) in the Craigieburn soil compared with the Templeton soil in which Rec_inE% values were greater in WSP (9%) than NCPR (1.3%) treatment. The higher values of P derived from the applied P fertilizers in the E pool (Pdff_inE%>80%) suggested that the NCPR application in both soils would be efficient for increasing P availability to plants.     

Applications of fertilizer cations affect cadmium and zinc concentrations in soil solutions and uptake by plants

A pot experiment was conducted to study changes over time of Cd and Zn in soil solution and in plants. Radish was grown in a soil which had been contaminated with heavy metals prior to 1961. Constant amounts of a fertilizer solution (NH₄NO₃, KNO₃) were added daily. Soil solution was obtained at intervals by displacement with water. The cumulative additions of small amounts of fertilizers were made equal to the plants' requirements at the final harvest but were found to exceed them during most of the experiment. Excess fertilizers caused substantial increases of major (K, Ca, Mg) and heavy-metal (Cd, Zn) ions in soil solutions and a decrease in soil pH, probably due to ion-exchange mechanisms and the dissolution of carbonates. Uptake of Cd and Zn into leaves was correlated with the mass flow of Cd (adjusted r²= 0.798) and Zn (adjusted r²= 0.859). Uptake of K, Ca and Mg by the plants was independent of their concentrations in solution. It is concluded that, in order to study effects of plants on heavy-metal availability and obtain soil solution that has not been altered by fertilizer ions, nutrients must be added according to the needs and growth of the plants. This could be achieved by linking fertilizer additions to the rate of transpiration, as nutrient uptake and transpiration were closely correlated in this experiment.     

农用聚磷酸铵在土壤中的有效性研究进展及在农业上的应用

近年来,农用聚磷酸铵作为一种新型肥料逐渐进入我国化肥领域,常用作高浓度液体复合肥料的基础磷肥。聚磷酸铵pH值近中性,结晶温度低,具有螯合性、缓释性,有着很大发展空间。本文综述了聚磷酸铵在土壤中有效性(溶解性与移动性)的影响因素,重点分析水解速率、土壤矿物、土壤质地与水分对聚磷酸铵在土壤中的有效性,并分析聚磷酸铵在农业上的应用与发展前景。     

Soil Total Nitrogen and Natural 15Nitrogen in Response to Long-Term Fertilizer Management of a Maize–Wheat Cropping System in Northern China

The Fengqiu long-term field experiment was established to examine effects of organic manure and mineral fertilizers on soil total nitrogen (N) and natural ¹⁵N abundance. Fertilizer regimes include organic manure (OM), one-half N from organic manure plus one-half N from mineral N fertilizer (1/2OMN), mineral fertilizers [N–phosphorus (P)–potassium (K), NP, NK, PK], and a control. Organic manure (OM and 1/2OMN) significantly increased soil total N and δ¹⁵N, which was expected as a great amount of the N applied remained in soils. Mineral NPK fertilizer and mineral NP fertilizer significantly increased total N and slightly increaed δ¹⁵N. Phosphorus-deficient fertilization (NK) and N-deficient fertilization (PK) had no effect on soil total N. Significantly greater δ¹⁵N was observed in the NK treatment as compared to the control, suggesting that considerable N was lost by ammonia (NH₃) voltalization and denitrification in this P-deficiency fertilization regime.     

Salinity effects on nitrogen metabolism in plants – focusing on the activities of nitrogen metabolizing enzymes: A review

Nitrogen (N) metabolism is of great economic importance because it provides proteins and nucleic acids which in turn control many cellular activities in plants. Salinity affects different steps of N metabolism including N uptake, NO₃^? reduction, and NH₄⁺ assimilation, leading to a severe decline in crop yield. Major mechanisms of salinity effects on N metabolism are salinity-induced reductions in water availability and absorption, disruption of root membrane integrity, an inhibition of NO₃^? uptake by Cl^?, low NO₃^? loading into root xylem, alteration in the activities of N assimilating enzymes, decrease in transpiration, and reduction in relative growth rate which results in a lower N demand. However, the effects of salinity on N metabolism are multifaceted and may vary depending on many plant and soil factors. The present review deals with salinity effects on N metabolism in plants, emphasizing on the activities of N metabolizing enzymes in a saline environment.     

红壤交换性钙、镁和钾的分布及施肥对其影响

A leaching experiment was Carried out with repacked soil columns in laboratory to study the leaching process of a red soil derived from sandstone as affected by various fertilization practices.The treatments were CK(as a control),CaCO3,CaSO4,MgCO3,Ca(H2PO4)2,Urea,KCl,Multiple(a mixture of the above mentioned fertilizers) and KNO3,The fertilizers were added to the bare surface of the soil columns,and then the columns were leached with 120 mL deionized water daily through perstaltic pumps over a period of 92 days,At the end of leaching process,soils were sampled from different depths of the soil profiles ,i.o.,of 92 days,At the end of leaching process,soils were sampled from different depths of the soil profiles,I.e.0-5cm,5-10cm,10-20cm,20-40cm,and 40-60cm,The results showed when applying Ca,Mg,and K to the bare surface of the soil columns,exchangeable Ca^2 ,Mg^2 ,and K^ in the upper layer of the soil profile increased correspondingly,with an extent depending mainly on the application rates of Ca,Mg,and K and showing a downward trend,CaCO3,CaSO4,MgCO3,and Ca(H2PO4)2 treatments had scarcely and effect on movement of exchangeable K^ ,while CaCO3,and CaSO4 treatments singnificantly promoted the downward movement of exchangealble Mg^2 although these two treatments had no obvious effect on leaching losses of Mg,The fact that under Urea treatment,exchangeable Ca^2 and Mg^2 ,were higher as compared to CK treatment showed urea could prevent leaching of exchangeable Ca^2 and Mg^2 ,the obvious downward movement of exchangeable Ca^2 and Mg^2 was noticed in KCl treatment ,In Multiple treatment,the downward movement of exchangeable Ca^2 and Mg^2 was evident,while that of K^ was less evident,Application of KNO3 strongly promoted the downward movement of exchangeable Ca^2 and Mg^2 in the soil profile.     

Ecosystem partitioning of N-glycine after long-term climate and nutrient manipulations, plant clipping and addition of labile carbon in a subarctic heath tundra

Low temperatures and high soil moisture restrict cycling of organic matter in arctic soils, but also substrate quality, i.e. labile carbon (C) availability, exerts control on microbial activity. Plant exudation of labile C may facilitate microbial growth and enhance microbial immobilization of nitrogen (N). Here, we studied ¹⁵N label incorporation into microbes, plants and soil N pools after both long-term (12 years) climate manipulation and nutrient addition, plant clipping and a pulse-addition of labile C to the soil, in order to gain information on interactions among soil N and C pools, microorganisms and plants. There were few effects of long-term warming and fertilization on soil and plant pools. However, fertilization increased soil and plant N pools and increased pool dilution of the added ¹⁵N label. In all treatments, microbes immobilized a major part of the added ¹⁵N shortly after label addition. However, plants exerted control on the soil inorganic N concentrations and recovery of total dissolved ¹⁵N (TD¹⁵N), and likewise the microbes reduced these soil pools, but only when fed with labile C. Soil microbes in clipped plots were primarily C limited, and the findings of reduced N availability, both in the presence of plants and with the combined treatment of plant clipping and addition of sugar, suggest that the plant control of soil N pools was not solely due to plant uptake of soil N, but also partially caused by plants feeding labile C to the soil microbes, which enhanced their immobilization power. Hence, the cycling of N in subarctic heath tundra is strongly influenced by alternating release and immobilization by microorganisms, which on the other hand seems to be less affected by long-term warming than by addition or removal of sources of labile C.