Effect of urea supplementation on performance and safety in diets of Dorper crossbred sheep

This study was conducted to evaluate the efficacy and safety of dietary urea in sheep rations having a 50:50 concentrate:roughage ratio. Sixty‐four Dorper × thin‐tailed Han crossbred ram lambs with an average body weight of 30.8 (±0.02) kg were randomly divided into four groups of 16 sheep each, and each group was fed one of the following diets: a basal diet (CON), or CON supplemented with 0.5% (0.5UTM), 1.5% (1.5UTM) or 2.5% (2.5UTM) urea. Growth performance, carcass characteristics, non‐carcass offals, meat quality and peptic tissue lesions were assayed. The average daily weight gains for CON, 0.5UTM, 1.5UTM and 2.5UTM were 216, 218, 200 and 170 g, respectively, with the CON and 0.5UTM groups higher than 2.5UTM group (p < 0.05). Sheep from the 2.5UTM treatment had a significantly lower dry matter intake (1.29 kg/day) than those from the CON and 0.5UTM treatments (1.42 and 1.43 kg/day, p < 0.05), and the feed conversion ratio in the 2.5UTM group was the highest (p < 0.05). Carcass characteristics, including shrunk body weight, empty body weight, hot carcass weight, dress percentage, and the absolute or relative weight (% body weight) of heart, liver, spleen, lung and kidney, were not altered by the treatments (p > 0.05). The muscular pH of 2.5UTM was higher than that of CON (5.68 vs. 5.52, p < 0.05), and shear force in 0.5UTM was lower compared with CON and 2.5UTM (p < 0.05). The anatomical structure lesions in kidneys became more serious with the increasing dietary urea concentrations, with the 2.5UTM animals showing the most severe lesions compared with CON animals. Therefore, supplementary urea as a non‐protein nitrogen source for sheep should not exceed 1.5% of ration having a 50:50 concentrate:roughage ratio to ensure efficacy and safety.     

控释氮肥和尿素配比对不同品种夏玉米氮素累积、转移及其利用效率的影响

在黄淮海夏玉米生产区,不同控释氮肥和尿素的配比下,研究不同氮效率玉米品种的产量及其花前花后干物质和氮素累积分配规律,以及相应的氮素利用效率与经济效益,为该区域夏玉米氮肥高效施用提供理论与技术依据.试验采用裂区设计,周期为两年,以施氮处理为主区,设置0、180、300 kg·hm-23个施氮水平,并在180 kg·hm-...     

葡萄糖和尿素对新鲜水稻秸秆氨化品质的影响

为研究葡萄糖和尿素对新鲜水稻秸秆氨化品质的影响,采用不同质量分数的葡萄糖(0、4 g/kg)和尿素(0、2、4和6 g/kg)对水稻卓两优141的新鲜秸秆进行氨化处理,常温氨化50 d后开包取样分析各项指标。结果表明:氨化饲料中黄曲霉毒素、伏马毒素、玉米赤酶烯酮含量检测结果符合饲料卫生标准;尿素和葡萄糖的交互作用对氨态氮、可溶性碳水化合物和半纤维素含量有显著作用。随着尿素浓度的增加,各处理的pH值显著升高,氨态氮和粗蛋白(CP)含量显著增加,6 g/kg尿素处理组的中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)、酸性洗涤木质素(ADL)降解效果最好;4 g/kg葡萄糖处理显著降低了秸秆NDF、ADF、ADL和氨态氮含量,显著增加了秸秆可溶性碳水化合物(WSC)和粗蛋白(CP)的含量。综合分析,添加葡萄糖可以提高水稻秸秆的营养价值,4 g/kg葡萄糖+6 g/kg尿素处理组的氨化效果最佳。     

生物基包膜抑制型尿素对土壤温室气体排放及小青菜产量的影响

为研究生物基包膜氮肥对土壤温室气体排放及小青菜(Brassica chinensis)产量的影响,采用密闭式静态箱-气相色谱法测定盆栽试验条件下施用不同类型包膜尿素对土壤温室气体的排放特征,探究不同类型包膜尿素对土壤温室气体排放综合增温潜势(GWP)、排放强度(GHGI)及小青菜产量的影响。结果表明:抑制型尿素(I)、生物基包膜尿素(CRU)、生物基包膜抑制型尿素(CIRU)能够显著降低N_2O、CO_2、CH_4 3种温室气体的累积排放量。与普通尿素(U)相比,处理I、CRU和CIRU的N2O累积排放量显著降低了20.79%～79.52%,CO_2的累积排放量显著降低了46.53%～62.24%,CH4的累积排放量显著降低了25.38%～30.11%。与处理U相比,处理I、CRU和CIRU的GWP分别显著降低了40.44%、60.66%和65.02%;温室气体GHGI与GWP呈现出同样的趋势,处理I、CRU和CIRU分别显著降低了26.32%、70.53%和78.95%。与其他处理相比,处理CIRU具有最优的温室气体减排效果。处理CIRU的小青菜产量最高,为1 960.00 kg·hm~(-2),较处理U显著增产68.00%。研究表明,生物基包膜抑制型尿素在提高小青菜产量的同时还可以减少菜地温室气体排放及氮素气态损失。     

分析技术在土壤微塑料研究中的应用现状

微塑料污染已成为环境领域研究的热点问题。受采样、前处理和分析技术的限制,现有研究中检测到的微塑料尺寸普遍较大。定量分析技术不够成熟,文献数据之间的可比性较差。复杂组分和表面附着物导致土壤微塑料的分析检测存在更大的挑战。为更好地掌握研究现状与发展趋势,本文从光谱分析、热分析、显微分析等角度分类,对土壤微塑料研究中的分析技术进行了解析、对比和总结。光谱分析对微塑料进行定性和数量统计,常见的有傅里叶变换红外光谱法和拉曼光谱法。热分析用于组分鉴定和质量分析,具体分为裂解气质联用和热重波谱联用。显微分析则对形貌和尺寸进行表征,包括光学显微镜和电子显微镜两种。提出微塑料分析技术越来越丰富,但是针对土壤微塑料的分析是一项复杂的工作。分析技术的标准化是评价和治理微塑料污染的关键;现有的土壤微塑料检测方法各有利弊。组合或联用技术的使用有望更高效、精准地实现对土壤微塑料定性定量分析;应从需要解决的科学问题出发,根据研究目的合理选择分析技术;部分分析技术在土壤微塑料的实际测定有待于进一步的探索与验证。     

炭肥比和膨润土粘结剂对炭基肥颗粒理化及缓释特性的影响

为探究炭肥比和膨润土粘结剂对生物炭基肥理化及缓释特性的影响,以生物炭为基底,分别制备了炭肥比1:4,膨润土粘结剂质量分数为20%、15%、10%、5%和粘结剂质量分数10%,炭肥比为1:6、1:5、1:4、1:3的柱状尿素和氯化钾生物炭基肥颗粒,分析了生物炭基肥颗粒的理化及缓释特性。结果表明,在炭肥比为1:4条件下,膨润土粘结剂质量分数越高,生物炭基肥微观结构越紧密,力学和缓释特性越好,质量分数为20%时,氯化钾和尿素生物炭基肥平均抗压强度分别为286.78和281.27 N,前3天养分淋出率分别为45.53%和36.87%。在膨润土粘结剂质量分数为10%条件下,炭肥比越高,生物炭基肥缓释性能越好,炭肥比为1:3时,氯化钾和尿素生物炭基肥前3天养分淋出率分别为42.06%和40.32%。同时,氯化钾生物炭基肥表面孔隙先增后减,炭肥比为1:6和1:3的平均抗压强度分别为271.25和282.42 N。尿素生物炭基肥内部结构中孔隙变多,炭肥比为1:6时,平均抗压强度为最大值267.84 N。综合考虑,满足中等肥料浓度要求时,膨润土粘结剂质量分数为20%、炭肥比为1:4或膨润土粘结剂质量分数为10%、炭肥比为1:3的生物炭基肥成型配方较优。     

Application of urease inhibitor improves protein composition and bread‐baking quality of urea fertilized winter wheat

Background: Nitrogen losses is an economic problem for wheat production and a high risk to the environment. Therefore, improved N fertilizer management is a key to increasing the N efficiency and minimizing N losses. To increase N efficiency, enhanced fertilizers such as urea combined with urease inhibitor can be used. Aims: The aim of present study was to evaluate the effects of different N forms on grain storage protein subunits in winter wheat and to examine whether the observed changes correlate with parameters of baking quality. Methods: The investigation was performed over two consecutive years at two locations in Germany. Protein subunits were analyzed by SDS‐PAGE. Results: Protein concentrations were similarly increased after fertilization with ammonium nitrate and urea + urease inhibitor. Analysis of the individual storage protein fractions indicated that both fertilizers specifically enhanced ω‐gliadins and HMW glutenins, but the effect was more pronounced in the ammonium nitrate treatment. Application of urea + urease inhibitor had greater influence on the protein composition and resulted in higher specific baking volume as well as the best fresh keeping ability, in comparison with urea treatment. Conclusion: Considering that the urea + urease inhibitor treatment resulted in almost comparable improvements of NUE and baking quality, with the additional benefit of reduced N losses in combination with easy handling, urea + urease inhibitor can be recommended as a viable alternative to both urea alone and ammonium nitrate treatments. This opens up an opportunity for the reduction of N loss in wheat production when use of urea is preferred.     

日本包膜缓释肥料养分释放及微结构研究

采用恒温水培试验,研究了日本生产的五种包膜肥料(LP40、LPS40、SC60、LPSS和LPSS100)氮素释放特性,用一级反应动力学方程进行拟合,并用扫描电镜观察了包膜肥料水培前后膜的微观结构。结果表明,包膜肥料的膜材料不同,氮素释放量也不同;包膜肥料的氮素释放率随着时间的延长而增加;这五种包膜肥料的氮素释放特征均可用一级反应动力学方程来描述,氮素释放速率常数与氮素释放率成正比,与氮素溶出的半时值成反比;扫描电镜的图像分析结果显示,水培后LPSS、SC60的膜外表面完整性要好于LP40,LPSS的膜剖面结构很紧实,阻水性能好。     

含DMPP抑制剂尿素的氨挥发特性及阻控对策研究

采用原状土柱模拟方法,探讨了施肥水平、添加不同碳氮比（C／N）有机物、不同类型土壤、土壤水分含量及温度对含3,4-二甲基吡唑磷酸盐（3,4－dimethyl pyrazole phosphate,DMPP）硝化抑制剂的尿素（DMPP尿素）氨挥发损失的影响。结果表明,施肥水平对DMPP尿素的氨挥发损失有显著影响,随着DMPP尿素施用量的增加,土壤氨挥发损失量呈显著上升的趋势;DMPP尿素配施低C／N比的有机物鸡粪,氨挥发损失增加6．0％;而配施高C／N比的生物秸秆,则表现为可抑制78．2％的氨挥发损失;DMPP尿素的氨挥发损失受土壤理化性质影响很大,在肥力高的碱性土壤中氨挥发损失严重,而在酸性红壤和阳离子交换量高的青紫泥中挥发损失量较低;在土壤含水量为田间饱和持水量时,氨挥发损失表现为急剧增加;随着土壤温度的升高,氨挥发损失的量快速递增。合理控制施肥量、选择配施高C／N比的生物秸秆和适宜的水分管理方式是减少农田氨挥发损失的重要对策。     

醋酸棉酚对土壤脲酶活性的抑制作用

采用实验室模拟培养、测定剩余尿素量的方法,对醋酸棉酚作为一种新型脲酶抑制剂进行初步研究,并探讨醋酸棉酚对红壤脲酶活性抑制作用的影响因素。结果表明,醋酸棉酚与尿素混合施用,培养2d,1%醋酸棉酚(相对于尿素质量)的脲酶抑制率为53.57%。土壤持水量对脲酶活性有较大影响,且在脲酶活性高时,醋酸棉酚的脲酶抑制作用更强。随着温度的升高,醋酸棉酚对土壤脲酶的抑制作用越来越明显,且表现出混合性抑制的特征。醋酸棉酚提前施用7d,尿素回收率从混合施用的73.64%增加到99.00%,说明改进施用方式可大幅度提高醋酸棉酚的脲酶抑制效果。