Comparison of field and laboratory measurement of denitrification and N2O production in the saturated zone of hydromorphic soils

We evaluated a new method to measure in situ denitrification under field conditions in a number of water-saturated subsoils that had a broad range of biogeochemical properties. A test solution containing ¹⁵NO₃⁻ and/or C₂H₂ was introduced to the subsoil and the subsequent production of dissolved denitrification products was measured to quantify denitrification activity. The method showed a clear production of denitrification products over time. Results were compared to laboratory-based measurements from the same soil incubated as anaerobic slurries with added ¹⁵NO₃⁻. Rates of denitrification with the in situ and the laboratory methods ranged from 1-2800 and 1-1700 μg N kg⁻¹ d⁻¹, respectively. Generally the methods gave good agreement and we consider both to be valid. However, there were some significant deviations, which we attribute to spatial heterogeneity and laboratory effects. Because the laboratory method is so much easier to perform, we suggest it should be the preferred method for large-scale studies of denitrification from the soil types we investigated. However, the two methods showed poor agreement in determining the proportion of N₂O in the total denitrification output. This was because this proportion is subject to delicate and complex control. We conclude that neither method was suitable for quantifying N₂O emission from the denitrification measurements.     

区分土壤中硝化与反硝化对N2O产生贡献的方法

土壤是产生N2O的最主要来源之一。硝化和反硝化反应是产生N2O的主要机理,由于硝化和反硝化微生物同时存在于土壤中,因而硝化和反硝化作用能同时产生N2O。N2O的来源可通过使用选择性抑制剂,杀菌剂以及加入的标记底物确定。通过对生成N2O反应的每一步分析,主要从抑制反应发生的催化酶和细菌着手,总结了测量区分硝化、反硝化和DNRA反应对N2O产生的贡献方法。并对15N标记底物法,乙炔抑制法和环境因子抑制法作了详细介绍。     

The effect of soil texture and soil drainage on emissions of nitric oxide and nitrous oxide

Abstract. Agricultural soils are important sources of the tropospheric ozone precursor NO and the greenhouse gas N₂O. Emissions are controlled primarily by parameters that vary the soil mineral N supply, temperature and soil aeration. In this field experiment, the importance of soil physical properties on emissions of NO and N₂O are identified. Fluxes were measured from 13 soils which belonged to 11 different soil series, ranging from poorly drained silty clay loams to freely drained sandy loams. All soils were under the same soil management regime and crop type (winter barley) and in the same maritime climate zone. Despite this, emissions of NO and N₂O ranged over two orders of magnitude on all three measurement occasions, in spring before and after fertilizer application, and in autumn after harvest. NO emissions ranged from 0.3 to 215 μg NO-N m^–2 h^–1, with maximum emissions always from the most sandy, freely drained soil. Nitrous oxide emissions ranged from 0 to 193 μg N₂O-N m^–2 h^–1. Seasonal shifts in soil aeration caused maximum N₂O emissions to switch from freely drained sandy soils in spring to imperfectly drained soils with high clay contents in autumn. Although effects of soil type on emissions were not consistent, N₂O emission was best related to a combination of bulk density and clay content and the NO/N₂O ratio decreased logarithmically with increasing water filled pore space.     

Mitigation of greenhouse gas emissions from soil under silage production by use of organic manures or slow-release fertilizer

Abstract. Grassland is a major source of nitrous oxide (N₂O) and methane (CH₄) emissions in the UK, resulting from high rates of fertilizer application. We studied the effects of substituting mineral fertilizer by organic manures and a slow-release fertilizer in silage grass production on greenhouse gas emissions and soil mineral N content in a three-year field experiment. The organic manures investigated were sewage sludge pellets and composted sewage sludge (dry materials), and digested sewage sludge and cattle slurry (liquid materials). The organic manures produced N₂O and carbon dioxide (CO₂) consistently from time of application up to harvest. However, they mitigated N₂O emissions by around 90% when aggregate emissions of 15.7 kg N ha⁻¹ from NPK fertilizer were caused by a flux of up to 4.9 kg N ha⁻¹ d⁻¹ during the first 4 days after heavy rainfall subsequent to the NPK fertilizer application. CH₄ was emitted only for 2 or 3 days after application of the liquid manures. CH₄ and CO₂ fluxes were not significantly mitigated. Composting and dried pellets were useful methods of conserving nutrients in organic wastes, enabling slow and sustained release of nitrogen. NPK slow-release fertilizer also maintained grass yields and was the most effective substitute for the conventional NPK fertilizer for mitigation of N₂O fluxes.     

长期施肥对土nirS型反硝化细菌的影响及其与N2O排放的关系

土壤反硝化作用是土壤N₂O产生的重要过程,亚硝酸盐还原酶(NIR)催化的亚硝态氮(NO^-₂)还原为一氧化氮(NO)是反硝化作用的关键环节,研究长期施肥对反硝化微生物的影响及其与N₂O排放的关系对于全面理解土壤反硝化过程具有重要意义。基于28年的旱作雨养长期施肥试验,通过常规监测、定量PCR和高通量测序等探讨了长期不同施肥(不施肥CK、偏施肥的单施氮肥N和氮钾配施NK、以及氮磷钾平衡施肥NPK)下■土N₂O排放和nirS反硝化细菌群落特征及两者之间的关系。结果表明:长期化肥施用(N,NK和NPK)均显著提高了N₂O累积排放量,其中平衡施肥(NPK)最高。长期化肥施用对nirS基因丰度和nirS型反硝化细菌的α-多样性无显著影响,但长期平衡施用化肥提高了uncultured_bacterium₂303和Rhodanobacter_sp._D206a的相对丰度,降低了unclass...     

一氧化氮在植物中的生理作用

一氧化氮(NO)不仅是一种易扩散的生物活性分子,而且是生物体内重要的信号分子。植物细胞通过NO合酶、硝酸还原酶,或非生化反应途径产生NO。NO参与植物生长发育调控和对生物、非生物胁迫的应答反应。通过讨论NO的产生,对植物生长发育的影响及在抗逆反应中的信号调节来阐述NO在植物中的生理作用。     

壳聚糖对异育银鲫生长及抗菌能力的影响

在基础饲料中分别添加0.0%(对照组)、0.3%、0.5%、1.0%、2.0%壳聚糖,饲喂异育银鲫(体重46.20±3.56 g)二个月,测定鱼的生长与成活,进行嗜水气单胞菌的感染试验,并计算半致死量LD50。结果表明,不同浓度的壳聚糖均能极显著地提高鱼的增重,其中0.5%壳聚糖组增重率比对照组提高33.90%(P<0.01)。壳聚糖对鱼的成活率无显著影响。0.5%、1%壳聚糖组的异育银鲫对嗜水气单胞菌的抵抗能力显著高于对照组(P<0.05)。壳聚糖在异育银鲫饲料的适宜添加量为0.5%。     

Exogenous Nitric Oxide Alleviated the Inhibition of Photosynthesis and Antioxidant Enzyme Activities in Iron-Deficient Chinese Cabbage （Brassica chinensis L.）

The effects of exogenous nitric oxide （NO） on plant growth, chlorophyll contents, photosynthetic and chlorophyll fluorescence parameters as well as lipid peroxidation and activities of antioxidant enzymes were investigated in Chinese cabbage plants exposed to iron （Fe） deficiency. Iron deficiency led to serious chlorosis in Chinese cabbage leaves, and resulted in significant decrease in plant growth, photosynthetic pigments, net photosynthetic rate, Fv/Fm, Ф ps Ⅱ and activities of antioxidant enzymes, and increase in lipid peroxidation. While treatment with SNP, a NO donor, it could revert the iron deficiency symptoms, increased photosynthetic rate as well as activities of antioxidant enzymes, and protected membrane from lipid peroxidation, as a result, the growth inhibition of Chinese cabbage by Fe deficiency was alleviated.     

纳米氧化锌对肉鸡生长性能和屠宰性能的影响

【研究目的】本试验研究了纳米氧化锌对肉鸡生长性能和屠宰性能的影响。【方法】选用1日龄AA肉鸡192只,随机分为4个处理组,每组设4个重复,每重复12只鸡。在玉米-豆粕型日粮基础上添加纳米氧化锌0（对照）、40、80、120mg/kg,试验期6周。【结果】试验结果表明：整个试验期内,添加纳米氧化锌的试验组平均增重与对照组差异不显著（P＞0.05）。1~21d,纳米氧化锌在40mg/kg的添加水平肉鸡的饲料消耗显著低于对照组(P＜0.05）;料重比差异极显著(P＜0.01）;22~42d,纳米氧化锌在40mg/kg的添加水平肉鸡料重比显著低于对照组（P＜0.05）。于21、42日龄,每处理随机抽取12只,每重复3只,屠宰测定屠宰指标。结果表明：21d时试验组对肉鸡屠宰性能未产生显著影响（P＞0.05）,但所有测定指标中试验组均高于对照组（P＞0.05）;42d时纳米氧化锌在40mg/kg的添加水平肉鸡的屠宰率极显著高于对照组(P＜0.01）,肉鸡半净膛率显著高于对照组(P＜0.05）;添加纳米氧化锌的试验组肉鸡全净膛率、腹脂率、腿肌率、胸肌率与对照组差异不显著（P＞0.05）。【结论】因此,纳米氧化锌在40mg/kg的添加水平对提高肉鸡生长性能和屠宰性能效果最佳。     

淡水鱼丸的加工工艺研究

以白鲢为主要原料,研制和加工鱼丸产品。通过对鱼丸的感官特性综合评定,初步确定了鱼丸的最佳加工工艺和配方。