广东地区冬种多花黑麦草的生产特性

对在广东地区引种的国外20个优良多花黑麦草(Lolium multiflorum L.)品种的产量和品质等进行了分析.结果表明,刈割3茬的鲜草中,第2茬的产量最高,与总产量存在极显著正相关(P<0.01).各品种间前3茬鲜草产量、绝对干物质产量存在显著差异;所有品种绝对干物质率为8.4%~12.7%,其中各品种间前3茬刈割的干物质率存在极显著差异(P<0.01).品种01-Lm-1、LMT 1107、Common 1、Archie和LWD 8181-2的鲜草产量较高,达10.17 kg/m2以上,品种01-Lm-1、LWD 8181-2、BAR 9 TAM、Barprisma和LMT 9034的绝对干物质产量较高,达1.01 kg/m2以上.平均粗蛋白含量在16.05%~24.56%之间,品种间有极显著差异(P<0.01),其中品种Common 1、LWD 8115、LWT 8140的粗蛋白含量达23.52%以上.     

东北地区活动积温和极端持续低温的时空分布特征及其对粮食产量的影响

低温冷害是制约东北地区粮食产量的主要气象因素,了解低温冷害的演变规律及其对粮食产量的影响对于防灾减灾、合理搭配农作物品种熟期具有重要的指导意义。应用东北地区73个气象站1960—2004年温度资料以及ArcGIS地理信息系统技术和谐波分析方法,分析了≥10℃活动积温和持续低温指数的时空分布特征,评价了其对粮食和水稻产量的影响。结果表明,活动积温表现出由南向北、由西向东减少的趋势,持续低温指数表现出由南向北、由西向东增加的趋势。谐波分析表明,东北地区活动积温存在着明显的2.5~4a的周期振荡,持续低温指数主要表现为2.5~5a和10a左右的周期振荡。粮食产量的波动带有明显的活动积温和持续低温指数的信息,纬度越高,粮食产量受活动积温的影响越大,受持续低温指数的影响越小。活动积温是制约东北地区粮食和水稻产量的最主要因素,但持续低温指数的影响也不容忽视,持续低温指数每增加1d,会导致辽宁、吉林、黑龙江水稻平均单产分别下降6.2%、5.8%和2.1%。     

粗厚山羊草细胞质小麦核代换系育性差异

研究1996至1997年用D2类山羊草的粗厚山羊草4X,6X种细胞质小麦核代换系及其核亲本在我国北纬25°01′至47°08′的5个地点种植。调查了各点各期的自交结实率,结合各点、各期试验材料拔节至抽穗的日长、旬平均气温分析试验材料与日长、温度的关系。结果为(1)粗厚山羊草(6X,4X),随日长的增加,育性下降。其中,粗厚山羊草细胞质某些核代换系在我国适宜光、温条件下可出现完全雄性不育。(2)粗厚山羊草4X种细胞质和6X种细胞质的光温反应存在差异。（3）6X种细胞质的光温敏感性高于4X种细胞质。(4)粗厚山羊草细胞质核代换系的育性在日长相近条件下,温度升高,育性有提高。     

Weed-Suppressive Bacteria Have No Effect on Exotic or Native Plants in Sagebrush-Steppe

Approaches and techniques for control of exotic annual grasses are a high priority in rangelands including sagebrush steppe. Strains of the soil bacterium Pseudomonas fluorescens have been proposed to be selectively pathogenic to multiple species of exotic annual grasses (“Pf,” weed-suppressive bacteria, “WSB”). However, defensible tests of the target and nontarget effects of these WSB strains in the field are needed. We evaluated the effects of D7 and MB906 strains of Pf WSB in sagebrush steppe invaded by cheatgrass (Bromus tectorum L), medusahead (Taeniatherum caput-medusae L. Nevski), and other exotic annual grasses. We evaluated the WSB strains with and without herbicides (imazapic, rimsulfuron) or discing to mix surface-spray of the WSB into deeper soils, and we replicated these tests in three ecoregions that differed in soils and climate. Over 3 yr after treatment, neither WSB strain affected cover of exotic annual grasses, perennial bunchgrasses, or the total community, either with WSB alone or in combination with herbicides or discing. WSB has received considerable attention and is being applied across large rangeland areas, but the WSB strains and methods applied here were ineffective. We recommend any future use of WSB be applied in an experimental fashion, with experimental design and measurement of responses, until its effects can be proven.     

通过地形解析推定年降水量的分布

本文利用地形解析法对三明市六县的年降水量分布进行推定。结果表明,当年降水量资料以气象观察点的背后高度<100m和≥100m分组时,年降水量与经山体平均化后得到的高度示度之间有显著的线性相关,在此基础上进行的年降水量推定精度达91.8％,并制作了该六县的年降水量分布图。在该图上可以判读任意地点的年降水量值,可以为林业区划、立地质量评价、立地类型划分及农林生产等提供科学依据。     

复播大豆土壤微生物区系对麦–豆轮作体系周年施氮量的响应

为了揭示周年施氮对复播大豆土壤微生物区系的后效及叠加效应,于2017—2019年采用裂区试验设计,在麦–豆周年轮作体系下,设置不同施氮组合(麦季施氮0、104、173、242 kg/hm²,分别标记为N0、N1、N2、N3;复播大豆施氮0、69、138 kg/hm²,分别标记为S0、S1、S2),探究豆茬土壤细菌、真菌和放线菌数量,土壤菌群结构和氮素生理群数量的变化规律。结果表明：前茬麦季施氮对复播大豆土壤微生物数量具有显著的后效;复播大豆不施氮条件下,麦季N2～N3施氮范围有利于增加豆茬土壤细菌、真菌、放线菌和氮素生理群数量。在冬小麦不施氮条件下,当季豆茬施氮较不施氮处理能显著增加土壤3大类微生物和氮素生理群数量,但豆茬施氮量较高反而显著降低氨化细菌和好气性自生固氮菌数量。麦季各施氮处理与豆茬S1处理组合下土壤3大类微生物数量,细菌与真菌比值(B/F)及放线菌与真菌比值(A/F),氨化细菌、固氮菌和硝化细菌数量基本均高于与S2处理组合,其中N1S1施氮组合下豆茬土壤放线菌数量、好气性自生固氮菌数量、B/F和A/F值达到最高,N2S1施氮组合...     

近51a来额济纳旗绿洲胡杨年生长期对气候变化的响应

利用额济纳旗绿洲胡杨林分布区内的气象站点1960—2010年的日平均气温和日平均最低、最高气温的数据,采用气候倾向率和相关分析等方法,研究了胡杨年生长期开始日、终止日、生长期天数、展叶始期、叶黄始日的变化特征及其对气候变化的响应。结果表明,近51a来研究区胡杨年生长期有开始日提早,终止日推后,年生长期延长,展叶始期提前,叶黄始日微推后的变化趋势。相关分析结果显示,胡杨年生长期开始日受3月平均气温影响最大,终止日受10月平均气温影响最大,胡杨生长期与3—11月平均气温呈显著正相关关系。4月平均气温对胡杨展叶始期的影响最大,且展叶始期与4月平均温度的负相关关系最显著,相关系数达0.678 2(α=0.001)。胡杨叶黄始日受9月平均气温的影响最大,且平均气温越高,胡杨叶黄始日越推迟。可见,研究区内胡杨对气候变化的响应比较明显。     

Soil quality effects on regeneration of annual Medicago pastures in the Swartland of South Africa

Annual medic (Medicago spp.) pastures are widely used as the forage component of crop rotation systems in the Mediterranean region of South Africa. Reliable establishment of medics can be challenging. This may be related to poor soil quality, an inherent problem of soils in the region often aggravated by poor management. The aim of this study was to determine the underlying soil quality factors that result in classifying soils as having low, medium and high medic pasture production potential. The study was carried out on two farms that have followed crop/pasture rotation systems for the past 20 years. Two growing seasons (2015 and 2016) were evaluated on areas within fields that were identified to have poor, medium and high production potential. Soil samples were taken to evaluate soil quality and to determine the medic seed density in soil. Above-ground seed production and herbage production were monitored during the growing season. The low productivity soils had the lowest below-and above-ground seed density, medic seedlings establishment and medic herbage yield. Soil sodicity was one of the main factors decreasing pasture productivity. In a production system where medics need to regenerate effectively following good seed production, soil sodicity may be especially detrimental.     

利用SSR标记分析一年生黑麦草遗传多样性的取样策略

一年生黑麦草(Lolium multiflorum)为异花授粉植物,其DNA多态性研究的取样策略与遗传多样性分析的可靠性和效率直接相关。从一年生黑麦草国家审定品种“长江2号”和“特高”中,分别提取50个单株DNA,同时提取5、10、15、20、25和30个单株叶片混合样本的DNA,利用SSR标记进行遗传多态性分析。研究结果表明,取样梯度间多态性信息含量指数(PIC)差异不显著(P>0.05),但当混合单株样本为20株时,PIC达到最高值;SSR平均等位基因数和单个SSR座位上等位基因种类随样品内单株混合数目增加而增加,当取样量在20株及以上时,等位基因数和等位基因种类趋于稳定,电泳图谱表现基本一致;不考虑稀有等位基因（基因频率≤10%）的漏检,采用20株混合样本能够最大限度保持检出较高频率（＞10%）等位基因,且重演性较好。鉴于此,利用SSR标记分析一年生黑麦草遗传多样性时采用20个单株混合样提取的DNA样本能够有效反映群体间差异。     

Seed variation among annual ryegrass cultivars in south-eastern USA and the relationship with seedling vigour and forage production

Abstract Annual ryegrass (Lolium multiflorum Lam.) is grown on more than one million ha in the south‐eastern USA each year. Recommended and actual seeding rates vary substantially within the region. The objective of this study was to evaluate variation in seed weight, germination, seedling vigour and seasonal yield performance among annual ryegrass cultivars. During 1997, 1998 and 1999, seed from fourteen commercial cultivars was weighed and germinated to determine numbers of pure live seed (PLS) m^?2 before yield evaluation at four locations. Seed from ten cultivars was planted at 0·7 and 2·0 cm depth in a greenhouse study to evaluate relative seedling vigour. Cultivar mean single‐seed weight ranged from 2·4 to 4·8 mg in 1997, 1·8 to 4·5 mg in 1998, and 2·6 to 4·6 mg in 1999. Seed germination ranged from 78·8% to 98·0% in 1997, 82·3 to 98·3% in 1998 and 77·8 to 98·3% in 1999. Seed number, PLS m^?2, ranged from 675 to 1289 in 1997, 710 to 1550 in 1998, and 717 to 1179 in 1999. Among the ten cultivars evaluated for seedling vigour, seedling weight differed between planting depths and a significant cultivar by year interaction was observed. Seedling weight was highly correlated with seed weight at each seeding depth. The effect of increasing number of PLS m^?2 on subsequent yield performance, although small, was consistently negative. These results indicate that target plant populations may be obtained more economically by adjusting seeding rates for seed size differences among cultivars and seed lots of annual ryegrass.