不同比例猪粪有机肥配施对稻穗不同部位氮含量分布的影响

[目的]探讨施用猪粪有机肥对稻穗不同部位籽粒氮素积累的影响,为提高水稻肥料利用率和畜禽粪便的资源化利用提供参考依据.[方法]以赣晚籼37号为材料,在水稻施纯N 180 kg/ha,N:P2O5:K2O=3:1:2.5的情况下,比较并分析全施化肥(NPK)、低量猪粪配施化肥(F7M3,即70%化肥配施30%猪粪)、中量猪粪配施化肥(F5M5,即50%化肥配施50%猪粪)和高量猪粪配施化肥(F3M7,即30%化肥配施70%猪粪)等处理的枝梗籽粒氮含量、穗位籽粒氮含量、稻穗氮含量、水稻籽粒吸氮量及其与水稻产量的关系.[结果]配施猪粪有机肥能有效降低水稻一次、二次枝梗籽粒氮含量,且随猪粪有机肥配施量的增加,穗位籽粒氮含量也呈降低趋势,其中F3M7处理上、中、下部的籽粒氮含量较NPK处理分别显著降低11.6%、11.9%和9.1%(P<0.05,下同).增施猪粪有机肥能促进水稻产量增加与稻穗氮含量下降,与NPK处理相比,猪粪配施处理的稻穗氮含量显著下降5.7%~10.1%,水稻产量增加4.3%~14.1%,但猪粪有机肥配施处理的水稻籽粒吸氮量与NPK处理无明显差异,均在92.0 kg/ha左右.[结论]猪粪有机肥与化肥配施能有效影响稻穗不同部位的氮含量,合理利用有机肥资源有利于水稻的高产稳产.     

2011~2016年广西罗非鱼源无乳链球菌的耐药谱型分析

[目的]了解广西罗非鱼源无乳链球菌耐药谱的变迁规律,为罗非鱼无乳链球菌病的有效防控和科学用药提供参考.[方法]采用K-B纸片扩散法对分离自广西南宁、玉林、柳州、河池、北海和百色等市养殖患病罗非鱼的48株无乳链球菌株进行抗生素耐药性分析;并以抗生素的抑菌圈直径为变量,采用SPSS 18.0对无乳链球菌株进行聚类分析,以平方Euclidean距离表示菌株间的耐药性同类关系.[结果]48株广西罗非鱼源无乳链球菌的耐药谱型共有19种,谱型丰富度为39.6%.所有耐药谱型均为多重耐药谱型,耐药种数至少有3种.从采样地点来看,南宁市、玉林市、柳州市、河池市、北海市和百色市的分离株分别包含5、9、8、2、1和2种耐药谱型.2011~2016年各年份的菌株耐药谱型为:2011年10种(A、B、F、J、K、N、O、P、Q和S耐药谱型),2012年4种(B、H、N和S耐药谱型),2013年2种(L和M耐药谱型),2014年3种(B、D和S耐药谱型),2015年9种(B、C、D、E、G、H、J、R和S耐药谱型),2016年3种(B、I和J耐药谱型).聚类分析将48株广西罗非鱼源无乳链球菌分成2个组群(Group I和Group II)和6个亚群(i~vi),其中Group I和Group II组群均含有11种耐药谱型,耐药谱型丰富度分别为37.9%和57.9%;Group I和Group II两组群无乳链球菌株的抗生素敏感性差异主要取决于其对恩诺沙星、氟苯尼考和环丙沙星的敏感率或耐药率.[结论]2011~2016年广西罗非鱼源无乳链球菌的耐药谱型呈多样性,谱型丰富度较高,且因来源地不同和年际变化存在一定差异性.此外,通过聚类分析可根据无乳链球菌的耐药情况对其进行有效分型,建议作为无乳链球菌流行病学分型方法给予推广应用.     

桔梗与大葱间作对土壤养分、微生物区系和酶活性的影响

【目的】 分析桔梗大葱间作对土壤特性的影响,明确桔梗大葱间作消减桔梗连作障碍的效果。 【方法】 在桔梗连作3年的地块进行大田试验。设桔梗单作、桔梗大葱行比2∶1、3∶1、4∶1三种间作,移栽后15天开始,每隔30天取一次0—20 cm土壤样品,测定了土壤微生物区系、土壤脲酶、磷酸酶、转化酶和多酚氧化酶活性及土壤有效养分的含量。 【结果】 与桔梗单作相比,间作大葱土壤有效氮含量增加了22.3%～50.0%,提高幅度随着桔梗大葱间作行比的增加呈下降趋势。5～8月 (移栽后105天内) 桔梗大葱间作土壤有效磷含量高于桔梗单作,8月后低于桔梗单作。间作大葱对土壤速效钾含量的影响不显著。桔梗大葱间作提高了土壤碱性磷酸酶、土壤多酚氧化酶活性,且在桔梗生长后期的作用效果优于前期,但对土壤脲酶和转化酶的活性及变化趋势没有显著影响。桔梗大葱间作增加了土壤微生物总量和细菌数量,降低真菌数量,提高了土壤细菌/真菌比值。 【结论】 土壤细菌数量和细菌/真菌比值随桔梗大葱间作行比的增加而降低,而真菌数量反之。桔梗间作大葱是消减桔梗连作障碍的一种新型种植模式。      

Climate change and Chinese farmers: Perceptions and determinants of adaptive strategies

Farmers' perceptions, beliefs, adaptive strategies, and barriers regarding climate change are critical to promoting sustainable ecosystems and societal stability. This paper is based on an extensive survey of 1 500 farmers and their households in Henan Province in China during 2013–2014. Henan is the largest agricultural province in China with over 51 million farmers. The survey results showed that approximately 57% of the respondents perceived the direct impact of climate change during the past 10 years, with 70.3% believing that climate change posed a risk to their livelihood. Not surprisingly, most farmers reported that they have adopted new measures to mitigate the negative impacts of climate change. The main barriers hindering farmers' adopting adaptation measures were lack of funds and timely information. A multinomial logit model revealed that land ownership, knowledge of crop variety and the causes of climate change, as well as the belief of climate change, were all positively related to the likelihood of employing adaptive strategies. Moreover, the percentage of households engaging in agriculture activity, and years of engaging in farming were both negatively correlated with famer's likelihood of adopting adaptation strategies. More importantly, farmers with high incomes were less likely to adopt adaptive strategies and more willing to engage in other business activities. In conclusion, it is important to communicate climate change related information and government policies in rural areas, promote farmer associations and other educational outreach efforts to assist Chinese farmers to deal with climate change.     

Effects of UV-B radiation intensity and timing on epidemiological components of wheat stripe rust

Stripe rust caused by Puccinia striiformis f. sp. tritici is an important wheat disease worldwide that is greatly influenced by environmental conditions. Ultraviolet B (UV-B) radiation is one important environmental factor affecting the occurrence and epidemiology of wheat stripe rust. Investigating UV-B radiation effects on the epidemiology of stripe rust may be conducive to monitoring and predicting this disease. In this study, wheat seedlings were exposed to UV-B radiation during different periods under laboratory conditions and radiation effects on epidemiological components of wheat stripe rust were investigated. Results showed that incubation period was shortened, and the infection efficiency, sporulation quantity and disease index increased when UV-B radiation was performed only pre-inoculation. When the UV-B radiation was performed only post-inoculation or both pre- and post-inoculation, the incubation period was prolonged, and the infection efficiency, sporulation quantity and disease index were reduced. When healthy wheat seedlings were inoculated using urediospores collected from wheat leaves irradiated by UV-B only post-inoculation or both pre- and post-inoculation, infection efficiency, sporulation quantity and disease index were also reduced. However, in the latter, the disease incubation period did not differ under varying UV-B radiation intensities compared to that when wheat leaves were not treated with UV-B radiation. Overall, the effects of direct exposure of wheat plants to UV-B radiation with different intensities in different periods on epidemiological components of wheat stripe rust were systematically explored, and the results suggest that the effects of UV-B radiation increased gradually with the increase of UV-B radiation intensity. This information provides a basis for monitoring and predicting this disease as well as for conducting further studies on pathogen virulence variation.     

Potato yield gaps across the rainfed Yin-mountain Hilly Area of China

Yin-mountain Hilly Area is one of the ideal regions for potato (Solanum tuberosum) production in China. However, potato yield is severely limited as a result of rain-fed crop mode due to water deficiency, as well as an inadequate farming practices. In this study, yield gaps were determined by using attainable yield (Ya) as a benchmark under optimized management practices, i.e., micro-ridge and side planting with plastic-mulching (MS), and flat planting with plastic-mulching (PM). The yields under MS and PM modes are defined as Ya1 and Ya2, respectively. Under the same field with MS and PM modes but different densities and fertilizer usages and so on, it was defined as simulated farmers' practices. The yield of simulated farmers' practices (Yf1) reached 57.3 and 69.6% of Ya1 and Ya2, respectively, while the average yield of 298 randomly surveyed farmers (Yf2) reached only 37.0 and 47.8% of Ya1 and Ya2 for rain-fed potato, respectively. The gaps of water use efficiency exhibited similar pattern. Further analysis shows that improper measures in rainwater conservation and accumulation, and other management practices contributed to 18.5, 18.2, and 42.6% of yield gap between Ya1 and Yf2. Improper nutrition management, including overuse of nitrogen and the deficiency of phosphorus and potassium supplication, was one of the important reasons of yield gap. The results indicate the possibilities of increasing rain-fed potato yields by optimized water and fertilizer managements in the Yin-mountain Hilly Area.     

Mass loss and nutrient dynamics during litter decomposition in response to warming and nitrogen addition in a desert steppe

Plant litter decomposition has been studied extensively in the context of both warming and increased atmospheric nitrogen deposition. However, the temporal patterns of mass loss and nutrient release in response to warming and nitrogen addition remain unclear. A 2-year decomposition experiment aimed to examine the effects of warming and nitrogen addition on decomposition rate, and nitrogen and phosphorus dynamics. The effects of warming and nitrogen addition on decomposition of litter of Stipa breviflora, a dominant species in a desert steppe of northern China, were studied. Warming and nitrogen addition significantly enhanced litter mass loss by 10% and 16%, respectively, and moreover promoted nitrogen and phosphorus release from the litter in the first year of decomposition, followed by an immobilization period. The interactive effects of warming and nitrogen addition on mass loss, nitrogen and phosphorus concentrations of litter were also found during the decomposition. This study indicates that warming and nitrogen addition increased litter mass loss through altering litter quality. These findings highlight that interactions between climate change and other global change factors could be highly important in driving decomposition responses.     

亚热带农业小流域水体氮素及其稳定同位素分布特征

为控制流域氮素养分流失、改善流域水体环境,以亚热带典型农业小流域脱甲河为研究对象,对表层水体铵态氮(NH_4~+-N)、硝态氮(NO_3--N)浓度和水体硝态氮δ~(15)N(δ~(15)N-NO_3-)、沉积物有机质δ~(15)N(δ~(15)N-Org)浓度进行了连续试验观测,分析氮素浓度及其稳定同位素值的时空特征,探讨影响氮素分布的环境因子及水体NO_3-和沉积物有机质氮素的可能来源。结果表明:水体NO_3--N浓度明显高于NH_4~+-N,均值分别为1.62 mg·L~(-1)和0.90mg·L~(-1),并且分别在6月、8月及冬季较高;城镇区和农田区水体NH_4~+-N浓度与其他类型区差异显著(P0.05),并且显著高于其他水体;NO_3--N浓度在城镇区、农田区及山间林地区较高,水库区较低。支流NH_4~+-N浓度高于干流,均表现为冬季春季夏季秋季;干流、支流NO_3--N浓度分别表现为冬季夏季秋季春季、秋季冬季夏季春季。源头和出口处水体均表现为NO_3--N浓度高于NH_4~+-N,源头处氮素浓度低于出口处。水体δ~(15)N-NO_3-及底泥δ~(15)N-Org值分布范围分别为-19.87‰~8.11‰和-0.69‰~6.51‰,水体δ~(15)N-NO_3-最高值在Ⅲ级河段,最低值出现于Ⅳ级河段,各级河段间水体δ~(15)N-NO_3-11月差异较小,而1、2月差异明显;河流底泥δ~(15)N-Org最高值也位于Ⅲ级河段,而最低值则在Ⅰ级河段,Ⅲ、Ⅳ级河段δ~(15)N-Org值随时间变化趋势较为一致,Ⅰ、Ⅱ级河段δ~(15)N-Org最小值出现于1月。总之,脱甲河水体存在氮素污染现象且以外源输入为主,水体氮素来源主要为土壤有机质、人工合成肥料及陆源有机质,开展流域氮素分布及来源研究对认识流域尺度氮污染物的源解析具有一定科学意义。     

中国夏玉米和冬小麦近年生育期变化及其与气候的关系

作物物候期受气候条件和人为耕作的共同影响,而水热气候条件又直接影响着人为耕作时间。全球变暖背景下温度增加的趋势在近年来出现了停滞现象,针对这一新的气候变化特征,本研究选取作物物候观测和气象观测的站点数据,利用经典的统计学方法分析2000—2013年中国夏玉米和冬小麦主要物候期的变化趋势和空间分布,及作物生育期与对应水热条件的相关关系。研究发现:夏玉米和冬小麦各主要物候期均呈现一定程度的延后,其中64%的站点显示夏玉米成熟期延后,冬小麦成熟期延后的站点数比例达78%。研究期间,夏玉米和冬小麦的生育期历时对温度和降水变化均比较敏感,88%和64%的站点分别显示出夏玉米和冬小麦的生育期历时与平均温度之间呈负相关关系,而71%和77%的站点显示夏玉米和冬小麦生育期历时与年均降水量呈正相关关系。本研究时段内的气温变化也不同于一般性认为的单调升温,夏玉米生育期对应的平均温度呈增加和降低趋势的站点数基本相同,但显示降水量增加的站点较多,达到总站点数的68%;而冬小麦整个生育期显示冷干化趋势的站点居多,显示温度降低和降水量下降的站点数均占总站点数的60%以上。此外,本研究还用轮作站点探讨说明了可以利用年值气候数据替代生育期气候数据分析夏玉米和冬小麦轮作的物候和生育期特征。本研究通过站点数据证实了作物生长发育过程对气候变化的敏感性,新的气候条件下我国夏玉米和冬小麦的物候也对应产生了新的特征。     

湖北省潜江地区克氏原螯虾(procambarus clarkii)白斑综合征(White Spot Syndrome)PCR诊断及组织病理学观察

近年来在湖北省范围内人工养殖的克氏原螯虾暴发了严重的疾病,其中白斑综合征病毒（WSSV）已成为危害克氏原螯虾健康养殖的重要病原。2016年5月湖北省潜江市养殖区暴发了一种传染性疾病,为探究此次疾病病因和流行规律,将染病虾进行临床症状观察、对病料进行PCR检测、系统发育树分析、人工感染和组织病理学观察。结果显示,发病克氏原螯虾临床症状主要表现为摄食减少,活力下降,反应迟钝;组织病理学观察结果显示,克氏原螯虾的肝胰腺、肠、肌肉、鳃组织均出现不同程度变性和坏死以及炎性细胞浸润等典型病理学变化,与WSSV感染克氏原螯虾出现的病变相似;PCR检测患病克氏原螯虾样品,结果显示WSSV呈阳性,阳性检出率为55.56%（15/27）,未检测到斑节对虾杆状病毒（MBV）和传染性皮下及造血组织坏死病毒（IHHNV）;检测产物测序并进行系统发育树分析,结果显示,该基因序列与WSSV的EG3株（KR083866.1）核苷酸序列同源性为100%。将病虾的肝胰腺、肠和肌肉组织投喂健康克氏原螯虾,投喂组均表现为急性死亡（累积死亡率为100%）,并出现与自然发病虾相同的症状。WSSV的巢式PCR检测结果显示,人工感染病虾为WSSV阳性。根据以上显示,本次养殖克氏原螯虾大规模死亡的病原是WSSV。