Nutrient availability under trickle irrigation — phosphate fertilization

The effect of fertilization on the distribution of Bray No. 1 phosphate, total soil phosphate, iron, calcium, manganese and aluminium were studied in a trickle irrigated vineyard.Placement of superphosphate (9% P, 12% S, 20% Ca) at the trickle outlet increased phosphate availability to at least 22 cm depth, and the volume of soil containing more readily available phosphate increased with increasing application rate (18, 36.5 and 73 g per vine). Adding lime to the superphosphate increased P availability below the trickle outlet, but had little effect elsewhere.Placement of 73 g of P at the trickle outlet more than doubled total phosphate to between 20 and 40 cm below the surface. There was a significant linear relationship between P application rate and P concentration in vine leaves.The distribution of aluminium and manganese around the outlet did not change, and most of the calcium from the superphosphate was retained within 5 cm of the application point. Applying P reduced total iron in a region extending to at least 35–40 cm below the surface and to between 15 and 45 cm from the outlet. Reducing conditions in the soil during the irrigation cycle probably caused dissolution of iron which then moved into the profile in association with the P. Loss of iron would also have reduced the capacity of the soil to absorb phosphate, increasing its availability and enhancing its penetration to 25–35 cm.The results show placement of small quantities of superphosphate near the trickle outlet is a satisfactory alternative to broadcasting. (deceased)     

Control of nitrate pollution by application of controlled release fertilizer (CRF), compost and an optimized irrigation system

A nitrogenous controlled release fertilizer (Floranid 32) and a treatment of municipal organic waste compost were tested under two irrigation managements (conventional and ET-adjusted irrigation rates) with the aim of assessing risk of nitrate leaching to the aquifer. A check without N fertilizer was introduced. The experiment was carried out at La Poveda Field Station (30 km SE Madrid, Spain) in alluvial soils with water table depth at 4 m and under maize cropping. The experiment was laid out in a randomized complete block design with three replications, allocating 12 plots to each irrigation management. Although N fertilizer rate (150 kg ha^–1) was reduced at half as related to a previous experiment, no difference in grain yields was observed. This result relates to a high content of soil-N. Floranid showed promising results in controlling N-leaching in comparison with urea that exhibited an accelerated rate of N release which finally determines low use of N by the plant and marked NO₃ ^– leaching. Treatment of municipal waste compost showed NO₃ ^– concentrations in the soil water solution of similar values as those of urea at 140 cm. ET-adjusted irrigation showed no drainage during the corn growing season and lower NO₃ ^– concentrations in the soil water solution which could indicate a general lower rate of N solubilization.     

Effects of initial soil calcium content on ammonia losses from surface-applied urea and calcium-urea

Ammonia loss from surface-applied urea occurs because urea hydrolysis increases the pH of the placement site microenvironment. Addition of Ca-salts with urea will control or reduce the microsite pH, thus reducing NH₃ losses. The degree of Ca-saturation of the cation exchange sites may influence the ratio of calcium:urea required to control ammonia loss. A laboratory study was conducted to determine if adsorbed Ca or CaCO₃ additions (acid soils only) had a measureable impact on Ca control of NH₃ loss from surface applied urea at various Ca:urea ratios.With urea alone applied to the soil surface varying the adsorbed Ca content of the treatment soil did not influence NH₃ loss. The addition of CaCl₂ with urea on the same pretreated soils generally resulted in NH₃ losses reflecting the initial pH of the soil. The Ca-saturated acid soils and those acid soils receiving CaCO₃ had higher NH₃ losses than untreated soils in the presence of urea with soluble CaCl₂. It was noted that increasing the calcium:urea ratios progressively depressed the NH₃ loss from all soils. Increasing the percent Na-saturation of the calcareous Harkey soil to 25 and 50% (ESP) reduced Ca control of NH₃ loss due to Ca being exchanged for Na on the cation exchange sites.Inclusion of CaCl₂ with the urea mixture on the surface of the pretreated acid soils resulted in stepwise differences in NH₃ loss concuring with the increases in pretreatment soil pH values (differing exchangeable Ca content). Other parameters that influence the amount of NH₃ loss, such as acidic buffer capacity and CEC, appeared more important than anticipated for control of NH₃ loss with the calcium:urea mixture. On Ca enriched soils the calcium:urea mixture was only slightly less effective in its ability to control NH₃ losses than on untreated soils.Contribution from the Texas Agric. Exp. Sta., Texas A&M University System, College Station, TX 77843, USA     

Effect of amounts and sequence of additions of urea and water on hydrolysis of surface-applied granular urea in unsaturated soils

The hydrolysis of surface-applied granular urea ( 15 mg of urea/particle) in 14 unsaturated soils as influenced by the amounts and the sequence of additions of urea and water and studied using open and covered soil column systems was in the following order: well-mixed surface-applied surface-applied surface-applied urea, granular urea, granular urea, granular urea, water added > water added > water added water added before, after, before, before, no drying no drying no drying drying The retarded hydrolysis' of surface-applied granular urea is attributed to retarded soil urease activity. Under the nondrying and drying conditions, the positive effect of increasing amounts of added water on the hydrolysis was less apparent when water was added 24–48 hours before than when it was added immediately after surface application of granular urea. When an increasing number of urea granules were evenly placed on a finite surface of unsaturated soil, the rate of urea application (quantity factor) increased but the percentage of urea hydrolyzed remained practically unchanged. These results suggest that it is necessary to consider effective urea concentration and effective urease activity for adequate understanding of in situ hydrolysis of broadcast fertilizer urea in unsaturated soil.     

Effects of compositional variations on CO2 foam under miscible conditions

Foam can mitigate the associated problems with the gas injection by reducing the mobility of the injected gas. The presence of an immiscible oleic phase can adversely affect the foam stability. Nevertheless, under miscible conditions gas and oil mix in different proportions forming a phase with a varying composition at the proximity of the displacement front. Therefore, it is important to understand how the compositional variations of the front affect the foam behavior. In this study through several core‐flood experiments under miscible condition, three different regimes were identified based on the effects of the mixed‐phase composition on CO₂ foam‐flow behavior: In Regime 1 the apparent viscosity of the in‐situ fluid was the highest and increased with increasing x_CO2. In Regime 2 the apparent viscosity increased with decreasing x_CO2. In Regime 3 the apparent viscosity of the fluid remained relatively low and insensitive to the value of x_CO2. © 2017 American Institute of Chemical Engineers AIChE J, 64: 758–764, 2018     

The tolerance of a grass forage,grown in pots,to urea applied to calcareous soils under very hot,dry conditions

Proso grass was grown in pots in calcareous soils that received different levels of urea applied at seeding under very hot, dry conditions. Urea applications greater than 83 mg N kg^/1 in one experiment and 130 mg N kg^/1 in another caused severe toxicity to the grass seedlings. The toxicity corresponded to the period of active urea hydrolsis, 3–5 days from germination. At this time detectable NH₄ in a low-and a high carbonate soil was equally far below that applied. A level of 40 mg NH⁴-N per kg soil appeared critical to seedling toxicity.     

Efficiency of fertilizers as nitrogen sources to banana plantations under drip irrigation

In a field experiment with bananas under drip irrigation in the semiarid and warm Jordan Valley, on a highly calcareous soil, application of urea, ammonium nitrate and potassium nitrate were compared. All treatments received equal amounts of N, P and K. The rate of growth and yield were higher on plots receiving urea and ammonium nitrate than on those receiving potassium nitrate. This was explained by a continuous balanced nitrate-ammonium-nitrogen nutrition in the first two treatments, while in the potassium nitrate treatment more nitrate than ammonium was available to the plants during the earlier growth period. Ammonium concentrations found in the soil profile indicate a partial inhibition of nitrification in the drip-irrigated system.     

Nitrogen transformations during hydrolysis and nitrification of urea

Nitrogen transformations occurring in ten soils fertilized with urea were determined during incubation in the laboratory for four weeks. Urea was applied at one rate, but with different placement methods. Urea was applied in solution, as prills with a 1 cm grid spacing and as prills with no spacing. Unfertilized soils and soils amended with KNO₃ solution were included as controls.Nitrite accumulated in the majority of soils treated with urea, and the maximum nitrite concentration measured was directly related to initial soil pH. Cumulative gaseous N losses as percentages of applied N were: NH₃, 0-59.6; N₂, 0-4.9; N₂O, 0-9.9; KMnO₄-N, 0-1.3; CH₃ONO, 0-<0.1. No gaseous N evolution was detected in control treatments. Gaseous N losses were correlated with soil pH (NH₃) maximum NO ₂ ^- concentration (N₂, N₂O, KMnO₄-N) and organic C content (N₂, N₂O). Fertilizer placement effects were generally not significant and were small in comparison with differences between soils.

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Resumo Foram determinadas, durante incubação em laboratório por quatro semanas, as transformações do nitrogênio ocorridas em dez solos fertilizados com uréia. A uréia foi aplicada a um só nivel, mas com diferentes métodos de aplicação: em solução e em grânulos com 1 cm de espaçamento de grade e em grânulos sem espaçamento. Solos não fertilizados e solos corrigidos com solução de KNO₃ foram incluidos como controles.O nitrito acumulado na maioria dos solos tratados com uréia e a concentração máxima de nitrito medido foram diretamente relacionados ao pH inicial do solo. As perdas cumulativas de N gasoso tomadas em percentagens de N aplicado foram: NH₃, 0-59.6; N₂, 0-4.9; N₂O; 0-9.9; KMnO₄-N, 0-1.3; CH₃ONO, 0-<0.1. Não foi detectada liberação de N gasoso nos tratamentos de controle. As perdas de N gasoso foram relacionadas com o pH do solo (NH₃), concentração máxima de NO ₂ ^- (N₂, N₂O, KMnO₄-N) e teor de C orgânico (N₂, N₂O). Efeitos da aplicação de fertilizante não foram de um modo geral significativos e foram pequenos em comparação com as diferenças entre os solos.

     

Release of urea from cellulosic hydrogel coated urea granule: Modeling effect of crosslink density and pH triggering

ABSTRACT

Urea granules were coated with CMC-g-cl-PAA hydrogel by in situ spraying and polymerization technique with mean thickness of 0.24 mm. Water absorption capacity of hydrogel coated urea granules varied from 18.67 to 217.33 g/g depending on pH. Urea release was extended due to hydrogel coating and kinetic analysis at different pH (4.0, 7.0 and 9.2) revealed a sigmoid function as best fit model. The coated urea granules showed pH triggered release property with higher rate in alkaline medium and slower in acidic medium. The prepared hydrogel coated urea granules may find its application in integrated water and nutrient management strategies in agriculture.     

Acid leaching of coal and coal-ashes

Twelve Turkish lignites and the corresponding ashes were leached in sulfuric acid (pH 1.0, 25 °C) for 14 days. Asphaltite from Silopi amended the coals. The conditions mimic treatment in the effluent from bioleaching of sulfidic mineral concentrates, but the results are equally valid for an isolated leaching process. The extended time meant that we approached equilibrium and maximum extraction.The coals have limited neutralizing capacity. H₂SO₄ (1.0-2.0 l, 1 M) was needed to stabilize 1 kg coal at pH 1.0 (liquid:solid ratio 10:1), but the coal-ashes required 18.0-24.0 l/kg dry solid, which is the neutralizing equivalent to CaO.Leaching of dominant inorganic phases consume acid, but our interest is merely to remove trace elements present as dopants. We removed large fractions of Mg and Mn, but Al, K and Na extractions were limited by the presence of stable minerals and bimetallic oxides. The formation of the latter is driven by combustion at high temperatures. Alumina, normally not stable at pH 1.0, was protected from the effluent by the organic phase in coal. Fe leaching varied and appeared to be a marker for different chemical occurrences in the solids.Cd, V, Zn, U and Th were leached to near 80% from the ashes, but considerably less from the coals. Co and Ni extractions were near 60%, but not always higher from the ashes compared with the coals. Cu yields increase following ashing and reached ca. 60%. Ti, Ba, and Cs were not leached.We suggest that direct acid leaching is of interest to limit the deleterious impact of ash deposits and to recirculate metals from the ash. Ash may partly replace limestone in hydrometallurgical processing, but, more importantly, metal ions extracted from ash may be fed into the metal recovery stages of such processes. It is particularly interesting to leach Co, Cu, Ni and Zn, besides Mn, V and the environmentally hazardous Cd, U and Th. Leaching of whole coals is well motivated for domestic use-lump sizes around 18-50 mm, or slightly smaller, 10 mm, if mandated by practical residence times—where generally no other measures are taken to protect the local environment.     

Effect of organic manure and chemical fertilizer on nitrogen uptake and nitrate leaching in a Eum-orthic anthrosols profile

Distribution and accumulation of NO₃-N down to 4 m depth in the soil profile of a long term fertilization experiment with organic manure and N and P chemical fertilizer were studied after 12 years, wheat and corn were planted in each year. The apparent N recovery decreased with increased N and P fertilizer. NO₃-N was mainly accumulated in 0-1.2 m depth of the soil profile with a maximum of 34 mg N kg-¹ for the treatment with 120 kg N and 26 kg P per hectare, a secondary maximum of 7.2 mg N kg-¹ was found at 3.2 m depth in the same treatment. NO₃-N accumulation in the soil profile was minimized in the trials with highest manure application. Nitrogen that was not recovered was leached as NO₃-N deeper than 4 m depth, was immobilized in the profile or was lost by denitrification. This revised version was published online in August 2006 with corrections to the Cover Date.     

论溶浸采矿法现状及发展方向

较系统地介绍了溶浸采矿法的堆置浸矿法，就地破碎溶浸采矿法，原地溶浸采矿法的国内外应用情况，同时分别阐述了它们的发展方向。     

不同控释氮比例的控释氮掺混肥氮素淋失特征研究

采用模拟灌溉和模拟降雨方法,研究不同控释氮比例的控释氮掺混肥在原状土柱土壤中养分的淋失特征。研究结果表明,控释氮掺混肥显著降低了土壤中铵态氮、硝态氮的淋失,增强了土壤pH值缓冲性,提高了后期土壤溶液电导率;控释氮占59％的控释掺混肥具有“前控后保”的特点,适于推广应用。     

硫酸烧渣中铁浸取条件的研究及应用

以硫酸烧渣、废酸为原料制取铁系化工产品。通过硫酸烧渣的活化焙烧及硫酸浓度、固液比、浸取时间等关键工艺条件的研究，得到最佳浸取条件：即烧渣与活化剂质量配比4：1，固液比0．25～0．30g／mL，反应时间40～50min，酸度50％～60％。渣中铁浸取率达到95％以上，浸取液可以直接用于制备铁系产品。     

Compositions and leaching behaviours of combustion residues

Combustion residues generated from different incineration processes create major environmental problems because these materials contain high amounts of toxic substances. In this communication, we report the leaching behaviours of three residues along with their mineralogical compositions. Column leaching experiments at two different pH values were conducted to study the leaching behaviours. Leachants were analyzed to determine the pH, the concentrations of some toxic elements like Pb, Cr, As, Cd, Se, B, Mo and the volume of leachants passing through the columns. Raw and some treated residues were also characterized by XRD and SEM-EPMA techniques. We found that the concentrations of some toxic elements present in the residues as well as in the leachant fractions collected at different time intervals after leaching were very high. The amounts of soluble salts and toxic elements in the municipal solid waste incinerator (MSWI) ash were higher than those in the other two residues. The order of alkalinities of the three residues was: fly ash (FA)>MSWI ash>sewage sludge ash (SS ash). The final pH of the leachant was related to the volume of leachant passing through the column. Some leachant properties were related to the mineralogical compositions of the residues and to the secondary minerals formed during the leaching period.     

Nitrogen leaching and uptake from calcium cyanamide in comparison to urea and calcium ammonium nitrate in an ultisol from the humid tropics

Leaching loss of N applied as calcium cyanamide (CaCN₂ — 19% N), urea and calcium ammonium nitrate (CAN — 26% N) to a coarse textured, kaolinitic ultisol profile was studied in the laboratory using undisturbed soil columns. The soil columns were leached with an amount of water equivalent to the annual rainfall of the sampling site (2420mm) using a rainfall simulator over a period of 42 days. The leachability of the three N fertilizers differed greatly and followed the order of CAN > urea > CaCN₂. Most of the N lost through leaching was in NO₃ form. Calcium cyanamide lost only 3% of applied N. Breakdown of CaCN₂ to NH₄ was incomplete (64%) and nitrification in the soil was inhibited resulting in negligible leaching loss. Nitrogen retained in the soil columns after the leaching cycle was mainly in ammoniacal form irrespective of source of N used.Effectiveness of CaCN₂ as a N source was also studied in a greenhouse experiment with maize (Zea mays) and upland rice (Oryza sativa) as testing crops. Calcium cyanamide applied one week before sowing of crops was as effective as CAN and urea under conditions of no N leaching. When applied at the time of planting and two or more weeks before planting gave lower dry matter yields and N uptake than CAN and urea.IITA Journal Paper no. 351     

Optimal design and planning of heap leaching process. Application to copper oxide leaching

Although the process of heap leaching is an established technology for treating minerals, such as copper, gold, silver, uranium and saltpeter, as well as remediating soil, no studies to date have investigated process optimization. This work presents a methodology for the design and planning of heap leaching systems to optimize the process. This methodology consists of the creation of a superstructure that represents a set of alternatives to search for the optimal solution; from this superstructure, a mixed integer nonlinear programming (MINLP) model was generated, and a BARON-GAMS solver was used to find the optimal solution. This method was applied to the extraction of copper from systems with one, two and three heaps, and the effects of copper price, ore grade and other variables were analyzed for each system. From the results, it can be concluded that this methodology can be used to optimize heap leaching processes, including planning and design issues.     

Synthesis and characterization of urea bridged hybrid periodic mesoporous organosilica materials

Urea bridged organic–inorganic hybrid mesoporous SiO₂ materials (U-BSQMs) were synthesized through a sol–gel procedure by co-condensation of bis(triethoxysilyl propyl) urea (BSPU) under basic conditions using cetyltrimethylammonium bromide (CTAB) as organic template. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the mesoporous structure of the sample. Fourier-transform infrared spectroscopy (FT-IR), solid state CP-MAS NMR spectroscopy of ²⁹Si (²⁹Si CP-MAS NMR) and ¹³C (¹³C CP NMR) indicated that most of the Si–C bonds are unbroken during the synthesis process. The N₂ adsorption–desorption results revealed that these hybrid mesoporous SiO₂ materials have bimodal distribution of pores with pore diameters of 2.4 and 3.8 nm, respectively. Thermogravimetric analysis (TG) demonstrated that about 16% Si–C bonds have been broke during the synthesis progress. This kind of material is expected to find possible application in ion supporting, drug delivery and catalysis.