Effects of benlate on leatherleaf fern growth,root morphology and rhizosphere bacteria

Reduced frond production as well as foliar disorders and root damage to leatherleaf fern (Rumohra adiantiformis [Forst.] Ching) coincided with the widespread use of Benlate fungicide in grower operations. These symptoms could not be explained by environmental conditions or the presence of new pathogens. The objective of this study was to examine the effects of Benlate at labeled rates on frond production, root morphology, and soil microbial characteristics of leatherleaf ferns. A separate experiment was conducted by adding Benlate at labeled drench rate to previously untreated soil to evaluate the promotion of soil bacteria. Benlate was applied to leatherleaf fern plants in the greenhouse at labeled foliar and drench rates for 17 months. Fronds were harvested during the last nine months. Roots of the ferns were examined using electron microscopy at termination of the experiment to determine physical and microbial characteristics of the roots. Rhizosphere bacteria were evaluated to determine counts and types. Lettuce seedling bioassays were conducted to evaluate bacterial isolates for possible deleterious effects on plants. Over the nine‐month harvest period, 181 fronds were harvested per pot from the control treatments, 162 for the Benlate foliar treatment, and 113 for the drench treatment. The Benlate drench rate resulted in significant reduction of frond production. However, the Benlate foliar rate was not significantly different from the control. Benlate application resulted in a reduction of root hairs and disruption of the root surfaces, especially at the drench rate. Total bacterial counts were not significantly different among Benlate treatments; however, the biodiversity of these populations was reduced with 46, 36, and 22 individual isolates identified for control, foliar, and drench rate treatments, respectively. Using a lettuce bioassay, compared to seedlings grown on sterile medium, the average seedling growth in the presence of isolates from the control treatment was 83%, 73% from the foliar rate treatment, and 60% from the drench rate treatment. The predominant deleterious isolates include Pseudomonas fluorescens, Ps. putida, and Ps. cepacia. In a laboratory experiment, these bacteria were shown to be promoted within the soil by Benlate application. These results indicate that Benlate has the potential to reduce yields of leatherleaf ferns. This reduction may be caused by direct action of the chemicals within the Benlate formulations or by the promotion of deleterious bacteria within the growing media.     

Promotion of phytotoxic bacteria in rhizospheres of leatherleaf fern by benlate DF

Foliar damage symptoms to leatherleaf fern (Rumohra adiantiformis [Forst] Ching) in Florida during widespread use of the fungicide Benlate DF could not be attributed to nutrition, cultural practices, environmental conditions, or new pathogens developing on the crop. The objective of this study was to assess the involvement of rhizosphere bacteria in the damage symptoms using bioassays to detect phytotoxic activity. Rhizosphere bacteria were cultured from rhizospheres of leatherleaf ferns sampled from ferneries where Benlate DF was routinely applied and from check ferneries not receiving the fungicide. Using a lettuce seedling bioassay, the proportion of rhizosphere bacteria that was plant growth‐inhibitory ranged from 7.5% and 11% for isolates from two check ferneries to 70% for those from a fernery previously treated with Benlate DF. Rhizosphere bacteria originating from Benlate DF‐treated leatherleaf ferns caused most severe damage on seedlings with some isolates reducing root growth 70% compared to control seedlings. Other symptoms induced by these bacteria, which were mainly fluorescent and nonfluorescent pseudomonads, included necroses and inhibition of root hair development. Results suggested that Benlate DF affected the composition of bacteria in leatherleaf fern rhizospheres by promoting a bacterial component with phytotoxic properties toward plant growth.     

A simple process-based model for estimating ammonia emissions from agricultural land after fertilizer applications

Abstract. Fertilizer applications to agricultural land are a significant source of ammonia (NH₃) emission to the atmosphere, accounting for approximately 10% of the total emissions from agriculture. Current estimates of emissions from fertilizer applications use 'fixed' emission factors. This paper describes a model in which the emission factors are expressed as a function of the important influencing variables: fertilizer type, soil pH, land use, application rate, rainfall and temperature. Total emission in 2002 for the UK were estimated by running the model for a 'standard UK' scenario, viz. 28.7 kt NH₃-N, which compares well with the UK inventory estimate of 30.4 kt NH₃-N. Differences exist in the estimates for specific fertilizer types, with the mean emission factor for urea applications to grassland, in particular, being lower by use of this model (13% compared with 23% of applied N for the UK inventory). Emission estimates were most sensitive to temperature and fertilizer type. Scenario testing showed that significant reductions in emission could be achieved by replacing urea with other forms of N fertilizer, by combining urea use with a urease inhibitor, or by modifying some management practices.     

不同施肥方式下土壤氨氧化细菌的群落特征

为了研究长期定位施肥对棕壤中氨氧化细菌（ammonia-oxidizing bacteria,AOB）种群结构多样性和垂直分布特征的影响,本研究采用化学分析、荧光定量PCR（qPCR）和变性梯度凝胶电泳（PCR-DGGE）技术,针对沈阳农业大学试验区不同施肥方式（不施肥、低量无机氮肥、高量无机氮肥、无机氮肥与有机肥配施）下不同土壤深度（0~20 cm、20~40 cm、40~60 cm）的土壤理化性质、AOB丰度及种群多样性进行分析,比较不同施肥方式对土壤AOB种群的影响。结果显示,与不施肥相比,施肥会降低土壤pH,增加土壤铵态氮（70.5%~939.21%）和硝态氮（253.20%~625.48%）含量。随土壤深度增加,土壤pH升高,铵态氮和硝态氮含量除低量无机氮肥处理外,多呈降低趋势。土壤增施氮肥可提高AOB丰度,降低总细菌丰度。其中,0~20 cm土层中AOB丰度较高,且高量无机氮肥处理的AOB数量最高,为9.65×10⁵拷贝数·g^-1（干土）。DGGE图谱分析显示,不同处理下,AOB群落结构多样性指数存在明显差异（P<0.05）,各多样性指数均在表层（0~20 cm）最高,增施氮肥则显著降低AOB的多样性。聚类分析表明,4个施肥处理中,高量无机氮肥处理聚为一类,其他处理则因土壤深度不同而异;3个土壤深度中,除不施肥处理外,所有施肥处理均表现为0~20 cm、20~40 cm土层发生聚类,40~60 cm则明显与其他两层分开。冗余梯度分析（RDA）显示,硝态氮（P=0.027）是造成影响AOB群落结构差异的主要原因。上述研究结果表明,长期定位施肥土壤AOB的数量和群落结构多样性受施肥方式显著影响,并表现出明显的垂直分布特征。与无机氮肥相比,有机无机配施处理有助于改善土壤pH,维持不同土壤深度下AOB群落结构多样性。     

氮钾化肥减施和有机肥增施对番茄果实品质及矿质元素含量的影响

以‘天禧三号’和‘必抗T608号’番茄为试材,采用垄下覆膜栽培,设置有机肥正常用量(60 t/hm²,4M)、有机肥增施(120 t/hm²,8M)和氮钾化肥推荐用量(225 kg/hm²,N1)、氮钾化肥减施15%(191.25 kg/hm²,N2)、氮钾化肥减施30%(157.5 kg/hm²,N3),随机组合,共6个处理(4MN1、4MN2、4MN3、8MN1、8MN2、8MN3),探究氮钾化肥减量及有机肥增施对设施番茄品质的影响,进一步量化适宜的施肥梯度。结果表明：(1)增施有机肥后,两个品种番茄的单果重均有所增加。(2)正常有机肥处理后,两个番茄品种果实品质指标随氮钾化肥减施变化趋势不一,说明氮和钾在不同品质指标中发挥的作用不同;增施有机肥后,两个番茄品种品质指标(番茄红素、维生素C、可溶性糖等)随氮钾化肥减施占比增大基本均呈先升高后降低的趋势。(3)‘天禧三号’番茄在相同用量有机肥处理下减施氮钾化肥使果实中氮和钾含量均增加,磷含量呈先降低后升高的趋势;‘必抗T608...     

西红柿对聚烯烃控释肥这种新的施肥方法的反应

The response of tomato （Lycopersicon esculentum） plants basically fertilized with 0.3 g N per plant of compound fertilizer with a N：P2O5：K2O ratio of 20：10：20 to sticks of polyolefin-coated fertilizer （POCF） （LongT0 with a N：P2Os：K2O ratio of 14：12：14） applied 23 d after transplanting was investigated using rooting boxes in the greenhouse. The results at 26 and 40 d after stick fertilizer treatment showed that the use of the stick fertilizer greatly increased the production of many new fine roots from the tomato plants. Compared to the unfertilized control, root length and root length density in the stick fertilizer treatment increased by 3.6-6.7 fold. In the soil zones near the stick fertilizer, root weight and root mass density were also significantly higher for the stick fertilizer treatment. Additionally, the use of the stick fertilizer increased the N, P and K concentrations in the leaves and stems of the tomato plants. The new fine roots growing near the stick fertilizer not only absorbed more nutrients and translocated them to the shoots, but also contained more nutrients within themselves. The soil ammonium and nitrate N data showed that N released from the stick fertilizer played a major role in inducing the production of new fine roots. These results indicated that stick fertilizer could be used as an alternative to the co-situs application technique to change and control the root distribution of crops as well as to increase the potential capacity of roots for water and nutrient absorption.     

Effects of rate and depth of fertilizer application on emission of nitrous oxide from soil fertilized with anhydrous ammonia

Summary Field studies to determine the effect of different rates of fertilization on emission of nitrous oxide (N₂O) from soil fertilized with anhydrous ammonia showed that the fertilizer-induced emission of N₂O-N in 116 days increased from 1.22 to 4.09 kg ha^–1 as the rate of anhydrous ammonia N application was increased from 75 to 450 kg ha^–1. When expressed as a percentage of the N applied, the fertilizer-induced emission of N₂O-N in 116 days decreased from 1.6% to 0.9% as the rate of fertilizer N application was increased from 75 to 450 kg N ha^–1. The data obtained showed that a 100% increase in the rate of application of anhydrous ammonia led to about a 60% increase in the fertilizer-induced emission of N₂O.Field studies to determine the effect of depth of fertilizer injection on emission of N₂O from soil fertilized with anhydrous ammonia showed that the emission of N₂O-N in 156 days induced by injection of 112 kg anhydrous ammonia N ha^–1 at a depth of 30 cm was 107% and 21 % greater than those induced by injection of the same amount of N at depths of 10 cm and 20 cm, respectively. The effect of depth of application of anhydrous ammonia on emission of N₂O was less when this fertilizer was applied at a rate of 225 kg N ha^–1.     

长期施用含氯化肥对棕壤硝化作用及氨氧化微生物的影响

【目的】氨氧化微生物是氨氧化过程的主要驱动者,氨氧化过程作为硝化作用的限速步骤对氮循环具有重要作用。本研究以沈阳农业大学棕壤含氯化肥长期定位试验的土壤为研究对象,探讨了连续34年施用高氯和低氯化肥对棕壤硝化作用及氨氧化微生物的影响。【方法】该长期试验在等量氮、磷、钾条件下,设置高氯和低氯处理,共8个处理:T1(不施肥);T2(单施尿素);T3(尿素+氯化钾);T4(尿素+过磷酸钙);T5(尿素+过磷酸钙+氯化钾);T6(尿素+磷酸一铵+氯化钾);T7(尿素+氯磷铵+氯化钾);T8(硝酸磷肥+过磷酸钙+氯化钾),T7为高氯处理。采集0—20cm土壤样品,利用荧光定量PCR技术测定氨氧化细菌(AOB)和古菌(AOA)丰度,并结合土壤硝化潜势和基本化学性质,分析长期施用含氯化肥对棕壤硝化作用及氨氧化微生物丰度的影响及影响氨氧化微生物丰度的主要环境因素。【结果】长期施肥降低了土壤pH值,高氯处理降低得最多,显著低于其他处理;高氯处理的土壤硝化潜势也显著低于其他处理,且除高氯处理外,配施磷肥的处理土壤硝化潜势显著高于不施磷处理。各处理土壤中AOA丰度均显著高于AOB,高氯处理土壤中AOA、AOB丰度均显著低于其他处理,土壤硝化潜势与AOA和AOB均呈显著正相关关系。【结论】连续施用高氯化肥34年显著降低了棕壤AOA和AOB丰度,抑制了硝化潜势。该结果可为通过含氯化肥的合理施用来调节土壤AOA和AOB,进而调控土壤氮素循环提供参考。     

减量施肥对保护地土壤养分淋失及番茄产量的影响

田间试验研究了减量施肥对巢湖沿岸的保护地土壤养分淋失及番茄产量的影响。结果表明,习惯施肥用量高,氮、磷、钾施用量分别为番茄养分吸收量的6.41、11.01、3.31倍,导致土壤中一些中微量元素供应不足;减量施肥能提高番茄产量,而添加硫、硼、锌的改进减量施肥技术增产效果较好,分别比不施肥、习惯施肥、减量施肥增产20.0%、10.3%、8.9%。习惯施肥养分淋失明显,20—80 cm土层NO3--N和有效磷含量分别比对照高498.9、52.4 kg/hm2;改进减量施肥技术可使土壤NO3--N淋失量减少65.7%,有效磷并未向深层移动。因此,改进减量施肥技术是提高巢湖蔬菜生产基地的番茄产量,增加收入,减少氮、磷养分淋失,防止面源污染的平衡施肥技术。     

生物有机肥和有机无机复混肥的研制及应用

介绍了利用麦草、鸡粪生产生物有机肥、有机无机复混肥的方法,并在多种农作物上进行了应用效果试验。结果表明,生物有机肥和有机无机复混肥不仅可以提高果品品质,而且在多种作物上具有明显的增产作用。因此,利用麦草、鸡粪等农业废弃物生产的生物有机肥、有机无机复混肥的应用能够减少目前我国农业生产对化肥的过度依赖,有助于我国绿色农业产业的发展。     

Growth and nutrient uptake of tomato in response to application of saline water,biological fertilizer,and surfactant

The importance of using low-quality water, such as saline waters, for food production has been increased in the recent decades. An experiment was conducted to evaluate the effect of diluted seawater (electrical conductivity (EC) of 6 dS m^?1) on growth and nutrient uptake of tomato. We examined if surfactant (0, 1, 2, 4 mg L^?1) and biological fertilizer (compost tea + arbuscular mycorrhizal fungi propagules) have potential to alleviate the adverse effects of salinity on tomato plant. Salinity stress significantly reduced all plant growth parameters. Under salinity stress, nitrogen (N) and potassium (K) contents in tomato shoot were lower, while phosphorus (P), sodium (Na), and calcium (Ca) contents were higher than non-salinized plants; showing ionic imbalance in this condition. Biological fertilizer improved root weight in saline condition. Under salinity stress surfactant application at the rate of 1 mg L^?1 helped tomato plants to maintain their ionic balance, especially declining Na uptake, and improved plant growth.     

Sources and rates of nitrous oxide emissions from grazed grassland after application of N-labelled mineral fertilizer and slurry

Nitrogen (N) fertilizer application and grazing are known to induce nitrous oxide (N₂O) emissions from grassland soils. In a field study, general information on rates of N₂O emission, the effect of cattle grazing and the type (mineral fertilizer, cattle slurry) and amount of N supply on the flux of N₂O from a sandy soil were investigated. N₂O emissions from permanent grassland managed as a mixed system (two cuts followed by two grazing cycles) were monitored over 11 months during 2001-2002 in northern Germany using the closed chamber method. The field experiment consisted of four regionally relevant fertilizer combinations, i.e. two mineral N application rates (0 and 100 kg N ha⁻¹ yr⁻¹) and two slurry levels (0 and 74 kg N ha⁻¹ yr⁻¹).Mean cumulative N₂O-N loss was 3.0 kg ha⁻¹ yr⁻¹, and the cumulative ¹⁵N-labelled N₂O emissions varied from 0.03% to 0.19% of the ¹⁵N applied. ¹⁵N labelling indicated that more N₂O was emitted from mineral N than from slurry treated plots, and in all treatments the soil N pool was always clearly the major source of N₂O. Regarding the total cumulative N₂O losses, differences among treatments were not significant, which was caused by: (i) a high variance in emissions during and after cattle grazing due to the random distribution of excrements and by (ii) high N₂ fixation of white clover in the 0 kg N ha⁻¹ treatments, which resulted in similar N status of all treatments. However before grazing started, treatments showed significant differences. After cattle grazing in summer, N₂O emission rates were higher than around the time of spring fertilizer application, or in winter. Grazing resulted in N₂O flux rates up to 489 μg N₂O-N m⁻² h⁻¹ and the grazing period contributed 31-57% to the cumulative N₂O emission. During freeze-thaw cycles in winter (December-February) N₂O emission rates of up to 147 μg N₂O-N m⁻² h⁻¹ were measured, which contributed up to 26% to the annual N₂O flux. The results suggest that N fertilizer application and grazing caused only short-term increases of N₂O flux rates whereas the major share of annual N₂O emission emitted from the soil N pool. The significantly increased N₂O fluxes during freeze-thaw cycles show the importance of emission events in winter which need to be covered by measurements for obtaining reliable estimates of annual N₂O emissions.     

Wheat straw biochar application increases ammonia volatilization from an urban compacted soil giving a short-term reduction in fertilizer nitrogen use efficiency

Journal of Soils and Sediments - The potential for using biochar to reclaim degraded urban land into productive land needs to be verified to address the incipient loss of agricultural land. A pot...     

Potential phosphorus leaching from sandy topsoils with different fertilizer histories before and after application of pig slurry

This study investigated the effects of historical long‐term and recent single applications of pig slurry on phosphorus (P) leaching from intact columns of two sandy topsoils (Mellby and Böslid). The soils had similar physical properties, but different soil P status (ammonium lactate‐extractable P; P‐AL) and degree of P saturation (DPS‐AL). Mellby had P‐AL of 220–280 mg/kg and DPS‐AL of 32–42%, which was higher than for Böslid (P‐AL 140 mg/kg and DPS 21%). The study investigated the effects since 1983 of four treatments with different fertilizer histories, in summary high (HighSlurryMellby) and low (LowSlurryMellby) rates of pig slurry and mineral P (MinMellby) applications at Mellby and mineral P application at Böslid (MinBöslid). The columns were irrigated in the laboratory five times before and five times after a single application of pig slurry (22 kg P/ha). Concentrations of dissolved reactive P (DRP), dissolved organic P and total‐P (TP) in leachate and loads were significantly higher (P < 0.005) from the treatments at Mellby than those at Böslid. TP concentrations followed the trend: HighSlurryMellby (0.57–0.59 mg/L) > MinMellby (0.41–0.49 mg/L) > LowSlurryMellby (0.31–0.36 mg/L) > MinBöslid (0.14–0.15 mg/L), both before and after the single slurry application. DRP concentrations in leachate were positively correlated with DPS‐AL values in the topsoil (R² = 0.95, P < 0.0001) and increased with greater DPS‐AL values after the single slurry application (R² = 0.79, P < 0.0001). Thus, DPS‐AL can be an appropriate indicator of P leaching risk from sandy soils. Moreover, the build‐up of soil P because of long‐term repeated manure applications seems to be more important for potential P losses than a single manure application.     

不同浓度CO2与化肥配施对番茄生长和养分吸收的影响

为阐明CO_2气肥在番茄种植中的最佳施用浓度,本试验通过在不同CO_2浓度(300、600、800、1 000、1 200、1 400μL/L)处理下配施不同浓度化肥[不施肥(CK),常规施肥,常规施肥基础上减施20%,常规施肥基础上增施20%]来探究CO_2气肥对番茄生长和养分吸收的影响。结果表明,CO_2浓度在800μL/L时,4种化肥处理下的番茄产量提高9. 11%～67. 76%,Vc含量增加12. 52%～38. 60%,可溶性糖含量增加45. 77%～85. 92%,硝酸盐含量下降7. 78%～38. 18%,并且CO_2浓度在800μL/L时,CK与减施化肥处理的番茄产量高于常规施肥处理与增施化肥处理,具有明显的减肥增效效应。因此,施用800μL/L的CO_2气肥能显著增加番茄产量,促进N、P、K养分的积累,同时对改善番茄品质,以及提高矿质元素的吸收利用有良好的促进作用。     

Nonlinear response of soil ammonia emissions to fertilizer nitrogen

Ammonia (NH₃) is an important atmospheric pollutant that threatens ecosystem and human health. Synthetic nitrogen (N) fertilizer applications are a major source of atmospheric NH₃. Most of current bottom-up estimates assume that the NH₃ emission response to increasing N application rates is linear, and thus constant emission factors (EFs) are used. However, increasing evidence suggests that NH₃ emissions increase exponentially with increasing N inputs. In the present study, we conducted a meta-analysis to generalize the relationship between N inputs and NH₃ emissions. Overall, the change in EF per unit of additional N fertilizer input (ΔEF) was positive from 70 experiments with at least three N application rates, suggesting that NH₃ emissions in response to increasing N additions grow at a rate higher than linear. Compared to our ΔEF model, the 10% EF model used by Intergovernmental Panel on Climate Change overestimated NH₃ emissions when fertilizer N is applied at low levels, but underestimated NH₃ emissions when N is applied in excess. Therefore, our results suggest that replacing the constant EF with the N-rate-dependent EF could improve the accuracy of NH₃ emission estimates.     

滴灌水肥一体化条件下番茄氮肥适宜用量探讨

利用田间小区7年定位试验,研究了滴灌水肥一体化条件下,不同化肥施氮量结合基施有机肥对番茄产量、品质、硝态氮累积、土壤电导率及土壤p H值的影响。结果表明:1)与不施氮相比,施肥可显著提高番茄产量,但过量施肥不仅不会提高番茄产量,还会降低番茄品质; 2)施氮量对土壤硝态氮的累积有较大的影响,随施氮量的增加,土壤剖面硝态氮累积量增加,其中对0～20 cm土层硝态氮累积量的影响最为显著; 3)土壤硝态氮含量与土壤电导率呈极显著相关关系,表明施氮量越高,电导率随之增加越显著,土壤的次生盐渍化风险越高; 4)除CK处理外,其它处理土壤硝态氮含量与p H值呈极显著负相关关系。综合考虑产量、品质与土壤环境质量,推荐华北温室秋冬茬番茄施用200 kg/hm~2有机N+250 kg/hm~2无机N,P2O575 kg/hm~2,K2O 450 kg/hm~2为宜。     

不同量化肥与有机肥配施对设施番茄栽培土壤硝化潜势和pH的影响

【目的】利用9年设施番茄定位试验,研究施氮量以及有机无机肥配施对土壤硝化潜势和pH的影响,为提高设施土壤供氮能力和减缓设施土壤酸化的施肥管理提供理论依据。【方法】设施番茄栽培定位施肥田间试验位于辽宁沈阳,始于2013年,每年种植一季番茄。设置施用尿素N 0、187.5、375.0、562.5 kg/hm² 4个水平(N0、N1、N2、N3),在每个氮水平下又设置施有机肥75000 kg/hm²处理(MN0、MN1、MN2、MN3),共8个处理。2021年,于番茄第一穗果膨大期(S1)、第二穗果膨大期(S2)、收获期(S3)和休耕期(S4),采集0—10和10—20 cm土层土壤样品,测定土壤硝化潜势(NP)、pH、铵态氮(NH₄⁺-N)和硝态氮(NO₃^--N)含量,以及休耕期土壤有机碳(SOC)和全氮(TN)含量,计算矿质氮(N_min)占TN的比例(N_min/TN)。【结果】化学氮肥施用量、施用有机肥及二者交互作...     

控释氮肥与水溶肥配施对设施番茄生理特征的影响

探究控释氮肥与水溶肥配施对番茄生理特征的影响,为设施番茄种植过程中合理的氮肥管理提供参考。采用盆栽试验研究设施番茄产量、品质与生理特征的变化。试验共设5个处理,分别为不施氮对照(CK)、常规施肥(尿素+水溶肥,U100)、常规总氮减20%(尿素+水溶肥,U80)、控释肥(控释氮肥+水溶肥,PCU100)和控释肥总氮减20%(控释氮肥+水溶肥,PCU80)。结果表明:与CK相比,施氮显著增加了番茄产量,但施氮处理间差异不大;与尿素相比,控释氮肥显著降低了番茄硝酸盐含量、盛果期净光合速率和硝酸还原酶活性(P0.05)。相比尿素,控释氮肥对谷氨酰胺合成酶和谷氨酸合成酶活性影响不明显。综上所述,控释氮肥与水溶肥配施较常规施肥能提高番茄盛果期净光合速率、硝酸还原酶活性,改善番茄品质。控释氮肥与水溶肥配施通过调控叶绿素、光合作用、氮代谢来影响番茄生理特征,进而影响产量和品质。     

Estimation of ammonia losses after application of liquid cattle manure on grassland

Field experiments under various conditions were carried out in Hohenheim and the Allgäu to measure the effects of liquid manure properties and meteorological factors on ammonia losses. The micrometeorological method (IHF) and the wind tunnel method were used. Depending on the prevailing conditions the ammonia losses varied between 14 and 99% of the applied ammonium nitrogen. The relationship between the ammonia loss and the logarithm of the dry matter content of liquid manure was highly significant. The dry matter content also influenced the time course of the ammonia loss. Solar radiation was the other major factor affecting ammonia loss. Compared to dry matter content and-solar radiation, effects of other factors such as ammonium content and pH of liquid manure, air temperature, relative humidity and wind speed were small in the given range tested. Based on the relationships between the various parameters a simple model for estimation of ammonia loss was developed.