Treatment of solid animal manures: identification of low NH3 emission practices

Cattle and pig dung and poultry excreta were used in laboratory experiments to study the effect of different solid manure treatments concerning NH₃ losses during storage and after application to soil. Aerobic decomposition (composting) during incubation (storage) resulted in drastically higher NH₃ emissions compared with anaerobic decomposition conditions. Application of the aerobically treated materials to soil resulted in low NH₃ losses, as NH₄-N concentrations were low in these materials. Anaerobically treated materials and non-decomposed poultry excreta gave rise to significant NH₃-N emissions as a result of highly increased ammoniacal N concentrations in soil, if applied on the soil surface. Rates of NH₃-N volatilization from soil surface-applied manures were closely related to the pH changes taking place on the surface. Maximum pH values attained explained 79% of the variance in the extent of NH₃ volatilization. Incorporation of animal dung into soil to 5 cm depth or below reduced ammonia volatilization by 80% compared with surface application.Ammonia emissions of both events were combined. Total losses of NH₃-N from animal manures were low throughout if anaerobically stored and thereafter incorporated into soil. The largest reduction in NH₃ losses from poultry excreta was achieved if the excreta were dried prior to storage and incorporated into soil. In contrast aerobic decomposition or composting of animal manures caused much higher NH₃ emissions. Composting of animal wastes should be restricted to those that need to be hygienized.     

Effects of nitrogen source,rate and application time on boronia (Boronia megastigma Nees) leaf nitrogen and flower production

Nitrogen was supplied from two fast release sources, ammonium sulfate ((NH₄)₂SO₄) and calcium nitrate (Ca(NO₃)₂) and a slow release source, isobutylidene diurea (IBDU) to boronia, a new flower crop native to Australia. At lower rates (25 kg per ha), N availability from different sources, as indicated by the leaf N concentration, did not differ within a month after application but three months after application, N availability was higher from IBDU than from (NH₄)₂SO₄ or Ca(NO₃)₂. At 50 or 100 kg per ha, N availability was higher throughout the year from (NH₄)₂SO₄ or Ca(NO₃)₂ than from IBDU, thereby allowing luxury consumption and causing toxicity. The flower yield increased with increasing N rates. Complete doses of all N rates which were applied early during the vegetative growth gave the highest yields and the same N rates applied in split doses at different phases of plant growth decreased the yields. In addition, high N availability during flowering (caused by a split dose) further decreased the yield. At all application times, IBDU gave the highest yield and the differences in yields with (NH₄)₂SO₄ and Ca(NO₃)₂ were not significant. The leaf N concentration associated with maximum yield declined as the plant advanced towards flowering.     

Environmental factors and cultural measures affecting the nitrate content in spinach

Environmental factors and cultural measures affecting the NO₃-content in spinach were studied indoors, in water-, sand- and soil-culture experiments. In the field, the influences of variations in N-fertilizing practices and in spinach varieties were also tested.High NO₃-contents in spinach were found with low light intensities, with low soil-moisture contents, and with high temperatures. NO₃-contents increased with increasing K-dressing (less so with KCl than with K₂SO₄), but decreased with increasing soil pH. In pot experiments, positive results were obtained with sulphur-coated urea, with farmyard manure and with pigmanure slurry.Application of Mo as a spray onto spinach leaves, and variations in P-dressings and in soil P-status were found not to affect the NO₃-content in spinach.In pot experiments, NO₃-contents decreased with progressing plant age (in autumn less so than in spring). Within spinach plants, NO₃-contents were highest in petioles and older leaves. Varietal differences in NO₃-contents were observed in a pot- and a field experiment.In pot- and field experiments, partial or complete replacement of NO₃-N by NH₄-N in general caused the NO₃-content in spinach to decrease. However, such a replacement was shown not always to result in lower NO₃-contents. Additional factors involved are e.g. the use and effectiveness of nitrification inhibitors, the soil type and the amount of available N.The amount of N added and, in the field, the amount of N available in the soil before sowing, strongly affected the NO₃-content in spinach. Under field conditions, nitrogen appeared to be taken up from the top 60 cm of the soil profile.The effects of variations in timing of nitrogen applications were absent in a pot experiment and not consistent in field experiments.List of abbreviations A = sum of inorganic anions (Cl + H₂PO₄ + SO₄ + NO₃) in meq per kg DM (H₂PO₄ stands for total P) - ADI = acceptable daily intake - C = sum of inorganic cations (Ca + Mg + Na + K) in meq per kg DM - C-A = excess of inorganic cations over inorganic anions in plants, meq per kg DM; NH₄-ions are not included - CEC = cation exchange capacity - DCD = dicyandiamide (C₂H₄N₄) - DM = dry matter - FW = fresh weight - FYM = farmyard manure - JECFA = Joint FAO/WHO Expert Committee on Food Additives - N-serve = nitrification inhibitor, containing 2-chloro-6-(trichloromethyl) pyridine (C₆H₃NCl₄), known as nitrapyrin, as active compound - org N = organic nitrogen (= total N — NO₃-N) - PMS = pig-manure slurry - SCU = sulphur-coated urea - WHC = water-holding capacity - WHO = World Health Organization     

Effect of poultry litter and composts on soil nitrogen and phosphorus availability and corn production

Environmental problems associated with raw manure application might bemitigated by chemically or biologically immobilizing and stabilizing solublephosphorus (P) forms. Composting poultry litter has been suggested as a means tostabilize soluble P biologically. The objectives of this study were to assessthe nutrient (N, P) value of different-age poultry litter (PL) compostsrelativeto raw poultry litter and commercial fertilizer and determine effects ofpoultrylitter and composts on corn (Zea mays) grain yield andnutrient uptake. The research was conducted for two years on Maryland'sEastern Shore. Six soil fertility treatments were applied annually to aMatapeake silt loam soil (Typic Hapludult): (1) a check without fertilizer, (2)NH₄NO₃ fertilizer control (168 kg Nha^–1), (3) raw poultry litter (8.9 Mgha^–1), (4) 15-month old poultry litter compost (68.7Mg ha^–1), (5) 4-month old poultry litter compost(59 Mg ha^–1) and (6) 1-month old poultry littercompost (64 Mg ha^–1). We monitored changes inavailable soil NO₃-N and P over the growing season and post harvest.We measured total aboveground biomass at tasseling and harvest and corn yield.We determined corn N and P uptake at tasseling.Patterns of available soil NO₃-N were similar between raw PL-and NH₄NO₃ fertilizer-amended soils. LittleNO₃-N was released from any of the PL composts in the first year ofstudy. The mature 15-month old compost mineralized significant NO₃-Nonly after the second year of application. In contrast, available soil P washighest in plots amended with 15-month old compost, followed by raw PL-amendedplots. Immature composts immobilized soil P in the first year of study. Cornbiomass and yields were 30% higher in fertilizer and raw PL amendedplotscompared to yields in compost-amended treatments. Yields in compost-amendedplots were greater than those in the no-amendment control plots. Corn N and Puptake mirrored patterns of available soil NO₃-N and P. Corn Puptakewas highest in plots amended with 15-month old compost and raw PL, even thoughother composts contained 1.5–2 times more total P than raw PL. There wasalinear relationship between amount of P added and available soil P, regardlessof source. The similar P availabilities from either raw or composted PL,coupledwith limited crop P uptake at high soil P concentrations, suggest that raw andcomposted PL should be applied to soils based on crop P requirements to avoidbuild-up of available soil P.     

Uptake and apparent utilization of urea and ammonium nitrate in wheat seedlings

Intact wheat (Triticum aestivum cv. Quern) seedlings that were grown in presence or absence of NH₄NO₃ were exposed to solutions containing CO(NH₂)₂, NH₄NO₃, CO(NH₂)₂ + NH₄NO₃, CO(NH₂)₂ + KNO₃ and CO(NH₂)₂ + (NH₄)₂SO₄ for consecutive periods of 3, 3, 6, 12 and 24h and N uptake determined by solution depletion measurements. Differences in ethanol-soluble N and ethanol-insoluble N content of roots and shoots of control (zero time) seedlings and seedlings exposed to CO(NH₂)₂, NH₄NO₃ and CO(NH₂)₂ + NH₄NO₃ for 48 h were used to characterize N utilization during/following uptake.Regardless of initial N status, uptake of N from CO(NH₂)₂ was less than one-third of that from NH₄NO₃. Relative absorption of the CO(NH₂)₂ and NH₄NO₃ was not substantially altered by acidity control of the uptake solutions. There was a reciprocal antagonism between uptake of CO(NH₂)₂ and uptake of NH₄NO₃. Whereas CO(NH₂)₂ inhibited NH₄ absorption in each set of seedlings, it decreased NO₃ uptake only in seedlings that had been pretreated with N. Simultaneous presence of KNO₃ enhanced CO(NH₂)₂ uptake but presence of (NH₄)₂SO₄ decreased it to the same extent as NH₄NO₃. All absorption processes involving CO(NH₂)₂ and NH₄ were substantially restricted by pretreatment of the seedlings with NH₄NO₃. The results suggest that apparent utilization of ambient N was dependent on initial N status of the seedlings and on the nature of the N species to which they were exposed.     

Laboratory and greenhouse assessment of plant availability of organic N in animal manure

Laboratory data (thermal fractionation, pepsin extraction, C:N_o ratio) of dung and manure were mutually compared and contrasted with plant-availability of organic N (N_o) as found in a greenhouse experiment according to the double-pot technique. Two types of fresh cow dung (one with a relatively wide and the other with a relatively narrow C:N_o ratio) and four types of manure (from poultry, sheep, pigs and cow) were compared with ammonium nitrate as chemical reference fertilizer. Relative effectiveness of organic N (RE_o) was used as characteristic; it was calculated as the fraction of organic N that has the same availability to plants as inorganic N. RE_o for poultry and sheep manure could not be assessed, probably because of NH₃ volatilization causing direct damage to plants and N losses. RE_o values decreased in the order: dung with narrow C:N_o > dung with wide C:N_o > pig manure > cow manure. Thermal fractionation did not provide a suitable index of plant-availability of organic N. Pepsin extracted organic N gave a positive, and C:N_o ratio a negative relationship with RE_o. Also between pepsin extracted organic N and C:N_o ratio a negative relationship was found. As C:N_o ratio is relatively easy to determine, it is considered the most practical laboratory index for plant availability of organic N in animal manures low in ammonia. When using the double-pot technique, application rates of manure types high in ammonia should be restricted.     

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.     

Guayule seedling response to nitrogen fertilizers

Slow growth and high seedling mortality limit direct seeding establishment of guayule (Parthenium argentatum G.). This study was conducted to assess seedling growth enhancement by the addition of different rates and forms of N fertilizers and Ca salts. Experiments were conducted in a greenhouse with cultivar 593 under both surface and subirrigated conditions using water low in salts (salinity of 0.8 dSm^–1, SAR of 5.0 and 10 mg Ca L^–1). Under surface-irrigated conditions, seedling height and fresh plant weight increased with N application to the irrigation water to 70 mg L^–1. The best seedling growth was observed when (NH₄)₂SO₄ was added in combination with CaCl₂ or CaSO₄. Progressively less growth was observed by addition of (NH₄)₂SO₄ alone, CO(NH₂)₂ plus CaSO₄, CO(NH₂)₂ alone and Ca(NO₃)₂. When seedlings were subirrigated, however, the best growth was observed with Ca(NO₃)₂. Intermediate growth was obtained with (NH₄)₂SO₄ plus CaSO₄ and lowest growth rates with (NH₄)₂SO₄ alone. These differential responses may be explained by the differences in leaching and volatile characteristics of the N forms. Growth enhancement from N and Ca additions increased with time with significant increases 45 days after seeding. Nitrogen application with Ca may be effective amendment in promoting subsequent growth of direct seeded guayule.     

The effect of biological oxygen demand of cattle slurry and soil moisture on nitrous oxide emissions

The application of animal manure slurries to soils may cause high short-term emissions of nitrous oxide (N₂O). We performed studies on N₂O emissions varying the contents of NH₄-N and microbial available organic carbon (measured as biological oxygen demand, BOD) of cattle slurry. Additionally the effect of slurry BOD on N₂O emissions at different soil water contents (35, 54, 71% water filled pore space, WFPS) was studied. Slurries from an anaerobic digestion plant (digested slurry, BOD: 1.2 g O₂ l⁻¹) or untreated slurry (BOD: 6.8 g O₂ l⁻¹) were applied at 30 m³ ha⁻¹ and incubated at 20°C. The higher the WFPS the more N₂O was emitted independent from the type of slurry applied. At low and medium soil water contents, the digested slurry induced significantly lower N₂O emissions than the untreated slurry. The N₂O emissions were directly correlated with the BOD content of the slurry (R ²=0.61, P≤0.001). We also compared the effect of NH₄-N concentration and BOD on emissions from the slurries at 54% WFPS. Again the BOD had a significant influence on N₂O emissions but a reduction of NH₄-N had no effect on the amount of N₂O emitted. The microbially available organic carbon seems to determine the amount of N₂O emitted shortly after slurry application. This revised version was published online in June 2006 with corrections to the Cover Date.     

Transformations and losses of fertilizer nitrogen on no-till and conventional till soils

A field study was conducted in 1982 to measure the effect of no-till (NT) and conventional till (CT) systems on N transformation after surface and subsurface applications of N fertilizers. Urea, urea-ammonium nitrate (UAN) solution, (NH₄)₂SO₄ (AS), and CA(NO₃)₂ were applied to NT and CT plots (5.95 m²) at a rate of 448 kg N ha^–1. A comparison of fertilizer N recovered in soils receiving incorporated or surface applied N was used to estimate NH₃ volatilization while denitrification was estimated from fertilizer N recovered in the presence and absence of nitrapyrin with incorporated N. Immobilization was assessed in microplots (0.37 m²) after surface application of (¹⁵NH₄)₂SO₄ to NT and CT systems at a rate of 220 kg N ha^–1.The results indicate little difference between NT and CT systems on urea hydrolysis rates and immobilization of surface applied fertilizer N. Approximately 50% and 10% of the surface applied N was recovered in the inorganic and organic fractions, respectively, on both tillage systems. The N not recovered was likely lost from plot areas through soil runoff. Incorporation of UAN, urea and AS resulted in 20 to 40% greater inorganic N recovery than from surface application. Nitrification rates were greater under the NT than the CT system. The similarities in concentration in the various N pools observed between the two tillage systems may be partially due to the short length of time that NT was imposed in this field study (<1 year) since other researchers using established tillage systems (>5 y) indicate that NT tends to promote decreased efficiency of fertilizer N.     

Ammonia loss from surface applied urea-acid products

Ammonia (NH₃) losses from soils occur only under alkaline conditions; therefore, adequate acidification could prevent NH₃ loss. In acid soils this alkaline condition will exist only as a micro-environment around the decomposing CO(NH₂)₂ granule. The objective of this experiment was to examine the degree of NH₃ loss reduction that occurs when acids are placed with surface applied CO(NH₂)₂. Phosphoric acid, H₂SO₄, HCl and HNO₃ were used with surface applied CO(NH₂)₂ in a laboratory experiment to examine resultant NH₃ loss under very extreme NH₃ loss conditions. Calcium and magnesium chloride salts were added to urea:phosphoric acid to compare the relative effectiveness of acid and Ca + Mg salts for control of NH₃ loss.Little depression of NH₃-N loss was found from CO(NH₂)₂ containing H₃PO₄ and H₂SO₄ when the sand contained free CaCO₃. However, when CO(NH₂)₂:H₃PO₄ (UP) mixtures were applied as 17-19-0 on neutral and acid sands, NH₃ losses were reduced. Molar ratios less than 1:1 (28-12-0, 35-7-0) resulted in NH₃ losses similar to those from CO(NH₂)₂ alone even in acid soils. The 110 g N m^–2 as 17-19-0 reduced relative NH₃-N loss and pH in acidified and neutral soils more effectively than 11 g N m^–2. Ammonia losses are determined by chemical reactions occurring under the individual CO(NH₂)₂ granules; therefore, the use of the high 110 g N m^–2 rates in this research. The 17-19-0 reduced soil pH and retarded the rate of CO(NH₂)₂ hydrolysis with consequent reduction in NH₃ loss. Ammonia loss was reduced only slightly at 11 g N m^–2 from 17-19-0 even in acid soils. Ammonia loss was reduced from 70 to 30% of applied N by applications of HNO₃ and HCl with the CO(NH₂)₂. The HNO₃ and HCl react with CaCO₃ in a calcareous soil to produce CaCl₂ and Ca(NO₃)₂ which are known to reduce NH₃ loss from surface applied CO(NH₂)₂. However, a dry product of HNO₃ · CO(NH₂)₂ is explosive and can not be used as a general fertilizer.Calcium chloride or MgCl₂ combined with CO(NH₂)₂:H₃PO₄ reduced NH₃ loss more at 110 g N m^–2 than at 11 g N m^–2. Calcium chloride reduced NH₃ loss more effectively than MgCl₂. The CaCl₂ and MgCl₂ salts were more effective than H₂SO₄ or H₃PO₄ in reducing NH₃ losses except when (e.g., 17-19-0) mixtures were added to neutral or acidic sands.Contribution from Texas Agric. Exp. Stn., Texas A & M University, College Station, TX 77843.     

Nitrogen balance and accumulation pattern in three contrasting prairie soils receiving repeated applications of liquid swine and solid cattle manure

The expansion of intensive livestock operations in western Canada has increased concerns about overloading of nutrients in manured lands. The magnitude of nutrient accumulation and its distribution in the soil profile varies with soil-climatic conditions. The objective of this study was to determine loading and distribution of manure-derived nitrogen (N) in the soil profile as influenced by repeated manure applications. Four field experiments were conducted at three sites (Dixon, Melfort and Plenty) in Saskatchewan under longer-term manure management. The four field experiments provide contrasts in soil type, climatic conditions, manure type, application and cropping history to enable the effect of these factors to be evaluated. Liquid hog manure (LHM—Experiment 1) and solid cattle manure (SCM—Experiment 2) treatments were applied annually over 8 years at Dixon (Black Chernozemic loam soil—Udic Boroll in sub-humid climate), while only LHM was applied at Plenty (Dark Brown Chernozemic heavy clay soil—Typic Boroll in semi-arid climate) over 6 years (Experiment 3), and at Melfort (Dark Gray Luvisol silty clay loam soil—Mollic Cryoboralf in humid climate) over 5 years (Experiment 4). Soil samples were collected in the spring and autumn of 2003 and 2004, and were analyzed for organic N, ammonium-N (NH₄⁺-N) and nitrate-N (NO₃⁻-N) concentrations. Plant samples were collected to determine the impact of manure application rate on plant N uptake and crop N removal. The annual application of LHM (37,000 L ha⁻¹ yr⁻¹) and SCM (7.6 Mg ha⁻¹ yr⁻¹) at agronomic rates at Dixon (added N balances crop demand for that year), or larger rates of LHM (111,000 L ha⁻¹) applied once every 3 years (Melfort) did not significantly elevate NO₃⁻-N in soil compared to the unfertilized control. Lower crop removal and reduced leaching of NO₃⁻-N due to drier conditions as occurred at the Plenty site contributed to greater accumulation of nitrate in the top 60 cm at equivalent rates compared to the other two sites. At large manure rates, excess N from the balance estimates could not be accounted for in soil organic N and was assumed to be lost from the soil-plant system. At the Dixon LHM site, deep leaching of NO₃⁻-N was observed at the excessive rate (148,000 L ha⁻¹ yr⁻¹) up to the 150 cm depth, compared to the control. At Dixon, the large annual application rate of SCM (30.4 Mg ha⁻¹ yr⁻¹) did not significantly increase NO₃⁻-N in the 0–60 cm soil compared to the control, which was attributed to lower mineralization of organic N from the SCM. Over the short and medium term, LHM application at large rates every year poses a greater risk for loading and deep migration of NO₃⁻-N in soil than large rates of SCM. Larger single applications made once every 3 years were not associated with accumulation or deep leaching. To prevent loading, rates of applied manure nitrogen should be reduced when crop N removal potential is diminished by high frequency of drought.     

The measurement of15N in soil and plant material

A complete procedure for analysing soil and plant samples for total N and atom % excess¹⁵N is described. The salicylic acid version of the Kjeldahl method for measuring total N was modified for use in a digestion block, giving quantitative reduction of nitrate in both soil and plant material. Procedures for minimising cross-contamination between samples are specified, including a double-distillation procedure that eliminates memory effects when distilling NH₃ from Kjeldahl digests. A simple and robust apparatus for converting (NH₄)₂SO₄ to N₂ gas for mass spectrometric determination of atom % excess¹⁵N is described. The coefficient of variation for replicate measurements of total N in soil and plant material over the range 0.1–2.2% N was 1.0%. The coefficient of variation for measurements of¹⁵N in plant material over the range 0.4–2.9 atom % excess¹⁵N was 0.2%.     

Gas emissions from liquid dairy manure: complete versus partial storage emptying

When manure slurry is removed from storages for land application, there is often ‘aged’ manure that remains because the storages are not completely emptied. Aged manure may act as an inoculum and alter subsequent methane (CH₄), nitrous oxide (N₂O) and ammonia (NH₃) emissions when fresh manure is added to the system, compared to an empty storage that is filled with fresh manure. Completely emptying manure storages may be a practice to decrease gas emissions, however, little pilot-scale research has been conducted to directly quantify the inoculum effect. Therefore, we compared CH₄, N₂O, and NH₃ emissions from three pilot-scale slurry tanks (~10.5 m³ each) filled with a mixture of fresh manure and an inoculum of previously stored manure (i.e., partial emptying) to three tanks that contained only fresh manure (i.e., complete emptying). Gas fluxes were continuously measured over 155 d of warm season storage using flow-through steady-state chambers. The absence of an inoculum significantly reduced CH₄ emissions by 56 % compared to partially emptied (inoculated) tanks, while there was no difference in N₂O emissions. There was a significant 49 % reduction in greenhouse gas (GHG) emissions because the overall budget (as CO₂-eq) was dominated by CH₄. Complete manure storage emptying could be an effective GHG mitigation strategy; however, NH₃ emissions were significantly higher from un-inoculated tanks due to slower crust formation. Therefore additional NH₃ abatement should be considered.     

Evaluation of an Integrated System for Pig Slurry Treatment

A system for pig slurry treatment, where anaerobic digestion, nitrification and denitrification have been integrated in a unique process treatment, has been investigated. This configuration allowed both removal of Chemical Oxygen Demand (COD) and a decrease in nitrogen content. Strategies are reported to bring enough COD to the denitrification system. Results (90% reduction in COD, 99·8% reduction in NH₄⁺-N and 98·8% reduction in NO₃⁻N) show this process could be considered a good alternative to treat these wastes. © 1997 SCI.     

Kinetic Studies on NO2 Absorption into Ammonium Sulfite Solutions

The absorption reactions of NO₂ into (NH₄)₂SO₃ solution were investigated in a stirred tank reactor. The kinetic regime of the absorption reaction was identified and the effects of various experimental parameters were studied. The experimental results indicated that the absorption of NO₂ into (NH₄)₂SO₃ solution is accompanied by a fast pseudo-first-order reaction. It was found that the NO₂ absorption rates were enhanced by the increasing concentration of (NH₄)₂SO₃ but nearly remained constant if the concentration is greater than 0.1 mol/L. The absorption rates also increased with increasing the reaction temperature and the concentration of NO₂ in inlet gas, but decreased as the oxygen concentration increased.     

Effects of N management on N2O and CH4 fluxes and15N

Forage production in irrigated mountain meadows plays a vital role in the livestock industry in Colorado and Wyoming. Mountain meadows are areas of intensive fertilization and irrigation which may impact regional CH₄ and N₂O fluxes. Nitrogen fertilization typically increases yields, but N-use efficiency is generally low. Neither the amount of fertilizer-N recovered by the forage nor the effect on N₂O and CH₄ emissions were known. These trace gases are long-lived in the atmosphere and contribute to global warming potential and stratospheric ozone depletion. From 1991 through 1993 studies were conducted to determine the effect of N source, and timing of N-fertilization on forage yield, N-uptake, and trace gas fluxes at the CSU Beef Improvement Center near Saratoga, Wyoming. Plots were fertilized with 168 kg N ha^-1. Microplots labeled with¹⁵N-fertilizer were established to trace the fate of the added N. Weekly fluxes of N₂O and CH₄ were measured during the snow-free periods of the year. Although CH₄ was consumed when soils were drying, flood irrigation converted the meadow into a net source of CH₄. Nitrogen fertilization did not affect CH₄ flux but increased N₂O emissions. About 5% of the applied N was lost as N₂O from spring applied NH₄NO₃, far greater than the amount lost as N₂O from urea or fall applied NH₄NO₃. Fertilizer N additions increased forage biomass to a maximum of 14.6 Mg ha^-1 with spring applied NH₄NO₃. Plant uptake of N-fertilizer was greater with spring applications (42%), than with fall applications (22%).     

Nitrogen Cycling with Respect to Environmental Load in Farm Systems in Southwest China

In Qibainong, a steep-mountainous karst region in southwestern China, self-sustaining societies have long existed, but increasing socioeconomic liberation has fuelled the recent rapid structural change of its economy. Consequently, environmental deterioration and exhaustion of resources have become problematic issues. We carried out a field survey in Qibainong in southwestern China and used both estimated and measured N flows and N balances from obtained results. Our results are summarized as follows (1) farmers used large amounts of chemical N fertilizers at intensities of 113–1124 kg N ha⁻¹; (2) substantial application of chemical fertilizer in Qibainong has contributed to an increase in potential NO₃-N leaching of 6–511 kg N ha⁻¹, followed by NH₃ volatilization; (3) crop products are largely distributed to feed livestock, the products of which are a major income source; (4) this area has a great requirement for imported food; (5) in addition, unused manure N (up to 191 kg N ha⁻¹) is generated by the increase in manure N production. Chemical fertilizer application, in addition to unused manure can be regarded as a major source of environmental damage. Based on the relationship between the N application rate and the NO₃-N leaching potential, we estimated the critical limit of the N application rate of chemical fertilizer + manure to be 297 kg N ha⁻¹. In Qibainong, unused manure, which is an important nutrient resource, was applicable within the critical limit. We recommend that all manure N produced within the village be used effectively on arable land, and that any shortages be supplemented by chemical N fertilizer up to 297 kg N ha⁻¹ to maintain water resource quality. Further improvement might be achieved through incorporating chemical fertilizers, P and K supplemented manure, and so on.     

Nitrogen fertigation of greenhouse-grown strawberries

Two greenhouse experiments were conducted with strawberries (Fragaria ananassa) grown in plastic pots filled with 12 kg of soil, and irrigated by drip to evaluate the effect of 3 N levels and 3 N sources. The N levels were 3.6, 7.2 or 10.8 mmol Nl^–1 and the N sources were urea, ammonium nitrate and potassium nitrate for supplying NH₄/NO₃ in mmol Nl^–1 ratios of 7/0, 3.5/3.5 or 0/7, respectively. Both experiments were uniformly supplied with micronutrients and 1.7 and 5.0 mmoll^–1 of P and K, respectively. The fertilizers were supplied through the irrigation stream with every irrigation. The highest yield was obtained with the 7.2 mmol Nl^–1 due to increase in both weight and number of fruits per plant. With this N concentration soil ECe and NO₃-N concentration were kept at low levels. Total N and NO₃-N in laminae and petioles increased with increasing N level. With the N sources the highest yield was obtained with urea due to better fruit setting. The N source had no effect on soil salinity and residual soil NO₃-N; residual NH₄-N in the soils receiving urea and ammonium nitrate were at low levels.     

Displacement of Ammonium from Aerosol Particles by Uptake of Triethylamine

The displacement of ammonium by triethylammonium (TEAH) in aerosol particles of about 15–35 μm in diameter was investigated using an electrodynamic balance (EDB) coupled with in situ Raman spectroscopy. The phase state of particles played a crucial role in the extent of triethylamine (TEA) uptake. At 50 or 75% relative humidity (RH), the heterogenous uptake of about 40-ppm TEA by aqueous ammonium salts of sulfate [(NH₄)₂SO₄], bisulfate (NH₄HSO₄), nitrate (NH₄NO₃), chloride (NH₄Cl), and oxalate [(NH₄)₂C₂O₄] led to increases in particle mass of over 90%. A complete displacement of ammonium by TEAH was confirmed by direct EDB mass measurements and the Raman spectra obtained. TEAH sulfate was formed during the exposure of aqueous droplets of (NH₄)₂SO₄ and NH₄HSO₄ to TEA vapor at 50% RH; but a fraction of it decomposed to TEAH bisulfate when the TEA supply was removed. Crystalline solid particles of (NH₄)₂SO₄ and (NH₄)₂C₂O₄ experienced small mass increases of <5%, both of which were attributed to the hindered mass transfer of TEA in crystalline solids. However, TEA reacted with the amorphous solid NH₄NO₃ particle at <3% RH as effectively as if it was in the aqueous NH₄NO₃ droplet (50% RH) and formed TEAH nitrate. On the other hand, the amorphous NH₄HSO₄ solid particle reacted with TEA at <3% RH to form crystalline (NH₄)₂SO₄ and liquid TEAH bisulfate and sulfate. The formation of rather inert crystalline (NH₄)₂SO₄ suppressed the ammonium exchange.

Copyright 2012 American Association for Aerosol Research