油菜地鼬瓣花的生物学特性

鼬瓣花(Galeopsis bifidaBoenn)为一年生双子叶杂草,种子繁殖。全生育期135 d左右。出苗期约40d,5月上中旬出土的苗占总数的76.7%,最适出苗深度为1.0~3.0 cm;花期54 d左右,果期60 d左右。单株结籽量平均约322粒。种子有休眠习性。鼬瓣花在油菜4叶期至结角期与油菜竞争强烈。植株的N、P2O5、K2O含量比油菜高3.41%~94.08%。     

酸模叶蓼的生物学特性与危害初步研究

酸模叶蓼（Polygonum lapathifolium）为一年生双子叶杂草，种子繁植。在西宁地区全生育期138d左右，出苗期53d，4月中旬为第一出草高峰，出草量占出草总数的14.8%，5月上旬为第二出草高峰，出草量占出草总数的31.4%。出草最适深度1993年为1.0-3.0cm，1999年为2.0-3.0cm。花期45d左右，结果期50d左右，单株结籽量平均2618.8粒。种了有休眠习性。酸模叶蓼在油菜4叶期至结角期与油菜竞争强烈，表现N、P、K含量比油菜高1.17%-55.78%。酸模叶蓼鲜重与油菜单株角果数呈极显著负相关关系，酸模叶蓼鲜重与油菜产量有显著负相关关系，回归方程分别为y1=241.38-0.0138x1(r1=-0.9726^**),y2=2407.1-0.1413x2(r2=-0.9303^*）。     

气候变暖对天水市作物生长的影响——以冬油菜为例

利用天水市1968-2009年间的气温变化资料,分析近几十年来天水市气温的变化趋势及特点;结合天水市农业科学研究所1980-2010年的油菜生育期资料,通过分析油菜生育期与温度的关系及变化趋势,建立回归模拟方程,揭示油菜对气候变暖的响应,为种植业结构调整和粮食安全提供理论依据.结果表明,天水市冬油菜播种期、出苗期有推迟趋势,现蕾期、抽薹期、初花期、盛花期及成熟期随时间的推移均呈现提前的交化趋势.冬油菜生育期间隔天数均表现为缩短趋势,成熟期提前10.1 d/10a.在油菜生育期各阶段中,播种～出苗期、抽薹～初花期、初花～盛花期间隔天数有延长的趋势,而出苗～现蕾期、现蕾～抽薹期、盛花～成熟期间隔天数均呈缩短趋势.油菜1980-2010年间千粒重总体呈现增加趋势,拟合方程为:y=0.0135x+ 2.5825,R2=0.0941.油菜全生育期与5、10、15、20 cm平均地温均呈极显著负相关.     

不同程度干旱胁迫对油菜种子萌发及幼苗生长特性的影响

采用不同渗透势聚乙二醇(PEG 6000)模拟干旱胁迫处理,观察油菜种子的萌发及生长状况.结果表明,干旱胁迫不同程度降低了油菜种子的萌发速率和出苗速率,-0.5～-1.0 MPa处理的最终发芽率随着渗透势的降低而显著降低,较对照降低了3.9%～86.9%,在-0.6～-1.0 MPa渗透势范围内不能成苗.试验7 d后将...     

湖北移栽油菜田牛繁缕的发生规律及防除策略

牛繁缕Malachium aquaticum（L．）Fries是油菜田恶性杂草。采用固定样方和随机样方法研究了移栽油菜田牛繁缕的出苗规律及在田间的种群动态，结合除草3,1筛选进一步探讨了其控制策略。结果表明，牛繁缕在田间的出苗高峰在油菜移栽后3周左右，出苗量达117．0株／m^2。占整个生育期出苗数量539．0株/m^2的21．71％。其种群数量在12月中旬左右达到最大值407．8株／m^2，累计出苗数量占全生育期的82．19％，这段时期是控制牛繁缕发生危害的关键时期。茎叶处理荆高特克和土壤处理荆高渗异丙隆对牛繁缕均具有较好的防除效果，施药后第60天的防效仍维持在95％以上，并且对油菜株高、角果数及产量无不良影响。     

藏蓟的生物学特性、危害损失与防治

在青海海南州共和县对藏蓟生物学特性和危害损失进行调查研究明确,藏蓟株高100-150 cm,多分枝,每株藏蓟开花9-30朵,平均每朵结种籽79粒。种子于室内存放225 d,仅7％-15.0％发芽。气温达0-12℃时藏蓟根茎萌发出苗,高峰期为5月上旬,全生育期约142 d。1 m²内有藏蓟8-10株时,青稞产量损失达30.3％-32.8％。     

移栽油菜田杂草防除临界期初步研究

油菜移栽后不同时间除草的试验表明,油菜移栽后的有草天数与油菜籽产量损失率之间是logistic曲线关系。曲线的两个拐点为t1=39.7d,t2=92.3d。在t1之后和t2之前,损失率增长迅速。因此,t1=39.7d可作为杂草与油菜的竞争临界期。应用时,可掌握为油菜移栽后40～45d。因此,油菜田除草应掌握在油菜移栽后45d之前。     

迈舒平包衣油菜籽防病治蚜虫试验初报

迈舒平(cruiserplus)是由噻虫嗪、咯菌腈和精甲霜灵三元科学复配而成,油菜种子进行包衣处理后播种,出苗率最低达81.8%,比对照高23.2%,苗后70d调查,对蚜虫的防效仍保持63.9%~86.9%,产量也与对照存在显著差异,全生育期油菜均无药害症状。     

油菜终花期摘除3叶防治菌核病效果好

油菜菌核病一直是陕西汉中盆地油菜高产的主要限制因素,80年代至今,曾出现过多次大流行年份,发病面积达2.67万hm~2以上,占油菜面积50％左右。一般田块病株率20％～30％,病指15～19,每667hm~2损失约10％,常年全区发病1.3—2万hm~2,年均损失1300t以上油菜籽。     

麦田野芥菜生物学特性及防除技术

小叶芥油菜俗名野芥菜,又名麻菜,十字花科芸薹属。原为油料作物,60年代初引种作绿肥,种子侵入麦田造成为害。 (一)主要形态特征与生物学特性野芥菜为越年生直立草本,直根系,主根圆锥形,高70～110厘米,长角果,易裂。种子萌发最适温度为16～20℃,土壤含水量为30～35％。如温湿度适宜,小麦播后3～4天野芥菜即出苗;日均温12℃,播后7～8天出苗;日均温8℃,播后10天出苗。冬季生长很慢,3月下旬返青抽薹,3月下旬至4月上中旬开花结籽,5月中旬末角果成熟,金生育期180～200天,     

Effect of burial depth and soil water regime on the fate of Lithospermum arvense seeds in relation to burial time

Lithospermum arvense is an increasing annual weed in winter crops of the semiarid region of southern Argentina under low impact tillage systems, an agricultural practice that has become popular in recent years. Seed distribution in the soil profile under conventional tillage will change when reduced tillage is implemented, thus affecting the germination microenvironment. The effect of seed burial depth and soil water regime on field germination, enforced dormancy, innate dormancy and seed decay was studied in relation to burial time in a field experiment. In addition, the effect of burial depth on seed germination and seedling emergence was examined under laboratory controlled conditions. Field germination of buried seed ranged from 55% to 65% for shallow (2 cm) and from 5% to 30% for greater depths (20 cm). Enforced dormancy levels were significantly higher among deeper seeds. The amount of innate dormant seeds was reduced to <10% after a year of burial. Lithospermum arvense seedbanks can be classified as short-term persistent. Germination in the laboratory was unaffected by burial depth, while seedling emergence reduction was adequately described by a sigmoidal model. Results indicate that agricultural practices that accumulate L. arvense seeds near the soil surface enhance seedling recruitment.     

EMERGENCE AND LONGEVITY IN CULTIVATED SOIL OF SEEDS OF SOME ANNUAL WEEDS

Summary. Four replicated experiments were begun in successive years to study the behaviour of viable seeds of eleven species of annual weeds when mixed with a 3 in. layer of cultivated soil. The soil was confined in pots sunk in the ground outdoors, seedling emergence was recorded, and the numbers of viable seeds remaining at the end of the experiments were assessed. One experiment was continued for 3 years, the others for 5 lull calendar years after the freshly collected seeds had been sown.
Initial emergence was greatest with Stellaria media, Senecio vulgaris and Poa annua , and least with Chenopodium album and Thlaspi arvense . Subsequently, the numbers of seedlings which emerged each year declined at a rate which was constant for each species. In the fifth year after sowing, the number of seedlings of Senecio vulgaris was only 0.3% of the initial number of viable seeds, while for Thlaspi arvense and Veronica hederifolia the figure was 3.2%.
The proportions of viable seeds which produced seedlings ranged from 37 to 86%, while from 0 to 11% were still present in the dormant state after 5 years. Most species showed marked patterns in the seasonal distribution of emergence which were modified by variations in weather from year to year, but in any one year, the distribution of emergence was not influenced by the length of time the seeds had been in the soil.
Germination et longévité dans des sots cultivés de semences de quelques mauvaises herbes annuelles     

Etude de la dynamique d'une communaute adventice: I — Evolution de la flore adventice au cours du cycle vegetatif d'une culture

Study of the dynamics of a weed community. I: Evolution of the weed flora during the growth cycle of a crop An experiment was laid out to compare the effects of soil working and chemical weed control on the dynamics of a weed community (agrophytocenosis). The authors describe the methodology of study and present the weed flora of this experiment. During the crop cycle, weed density reached a peak, which occurred in April in winter barley and in May in spring barley. The stock of viable seeds in the soil amounted to about 7000 seeds/m² over a depth of 30 cm and weed emergence from sowing to harvesting the barley was higher between 0 and 10 cm and 10 and 20 cm than between 20 and 30cm; for most species viability was more than 80% and was independent of the depth of burial.     

Role of temperature in regulating timing of germination in soil seed reserves of Thlaspi arvense L.

Summary. Most freshly-matured seeds of Thlaspi arvense L. (Brassicaceae) were dormant at maturity in May. Seeds sown on soil germinated in autumn and spring, but mostly in autumn. Buried seeds exhumed at monthly intervals and tested in light and darkness over a range of thermoperiods exhibited annual dormancy/non-dormancy cycles. However, the dormant period was short, usually only in April, but sometimes May, and in some years 1–6% of the seeds remained conditionally dormant. After-ripening occurred during summer, and seeds were non-dormant during autumn. Seeds entered conditional dormancy in winter and dormancy in late winter or early spring. When buried dormant seeds were kept at 25/15, 30/15 or 35/20°C for 12 weeks, they gained the ability to germinate to 95–100% at 15/6, 20/10, 25/15, 30/15 and 35/20°C. After burial for 12 weeks at 15/6 and 20/10°C, seeds germinated to 80–100% at 15/6, 20/10 and 25/15°C. but to only 11–64% at 30/15 and 35/20°C. After 4 weeks at 5°C, initially-dormant seeds germinated to 100% at all thermoperiods except 35/20°C, where only 15% of them germinated. However, after 18 weeks at 5°C, only 0–1% of the seeds germinated at all thermoperiods. Most non-dormant seeds exposed to 1, 5 and 15/6°C for 16 weeks were induced into dormancy; 1–15% entered conditional dormancy and thus germinated only at 15/6, 20/10 and 25/15°C. This study indicates that seeds of winter annual plants of T. arvense are non-dormant in autumn and enter dormancy in winter, while those from summer annuals are dormant in autumn and become non-dormant during winter.     

Weed seedling herbivory by field cricket Teleogryllus emma (Orthoptera: Gryllidae) in relation to the depth of seedling emergence

This study aimed to determine whether seedling herbivory by the field cricket, Teleogryllus emma (Ohmachi et Matsuura), promoted the mortality of Italian ryegrass (Lolium multiflorum Lam.), a non‐native grass weed in Japan, whether the impact of seedling herbivory differed depending on the depth of seedling emergence and the influence of cricket density on seedling mortality. First, the seedlings at emergence depths of 0, 1 and 2 cm were exposed to the cricket for 2 days in plastic cups and the amount of seedling mortality by herbivory was calculated. The level of mortality of 60 seedlings that emerged from seeds on the soil surface was 92.4%, significantly higher than that of the seedlings that emerged from seeds at depths of 1 cm (10.8%) and 2 cm (9.6%). Second, the seedlings at the emergence depths of 0 and 1 cm were exposed to the crickets at four different densities (zero, one, two and three individuals per 5700 cm²) for 5 days in plastic containers and the amount of seedling mortality by herbivory was calculated. The level of mortality by herbivory of the seedlings that emerged from 100 seeds on the soil surface was higher (33.3–61.3%) than that of the seedlings that emerged from seeds at a depth of 1 cm (4.7–13.1%) in the containers with one‐to‐three crickets. The level of seedling mortality tended to increase with an increasing cricket density. These results suggest that seedling herbivory by crickets is an important factor in weed mortality, particularly in no‐till fields and in field margins, where the seeds are more prevalent near the soil surface.     

Biology and management of Phalaris minor in wheat under a rice/wheat system

Summary Germination of Phalaris minor declined with the increase in duration of imbibition in water from 30 min to 72 h at temperatures above 22 °C . Germination was reduced down to 10 cm and 2 cm soil depth by wheat straw burning in puddled and non-puddled soil, respectively, with maximum reduction near the soil surface. The dormancy of P . minor seed was not more than 60 days under field conditions. In puddled soil, 38–60% of the viable seeds of P. minor remained concentrated in the upper 5-cm layer. Germination decreased with an increase in soil depth. In total, 15% of seeds stored in the laboratory emerged from 10-cm depth, whereas seeds did not germinate below 4.2-cm depth under field conditions. Depth of emergence of P . minor was shallower in zero tillage compared with the conventional method of wheat sowing. The seeds retrieved from rice soils kept under continuous submergence for 60 days exhibited 26% and 57% loss of germination over semi-submergence and semi-wet conditions respectively. There was 100% loss of germination in 10-month-old seeds retrieved from the soil under rice-growing conditions. Plant density of P. minor was lower in zero tillage than with the conventional method of wheat sowing. Cross-ploughing in the upper 2–5 cm of soil (shallow tillage) and drill-sowing of wheat 1 week after shallow tillage reduced germination of P. minor by 44% and 37% and increased grain yield by 21% and 47% over zero-tillage and conventional methods respectively.     

马唐生物学特性初步研究

通过室内试验研究温度、土壤含水量、水层和土层深度对马唐萌发和生长的影响。结果表明,马唐最适萌发温度为25-35℃,最低萌发温度为10-15℃,最高萌发温度为40～45℃;马唐萌发最适土壤含水量为40％,土壤含水量低于10％、大于50％时,萌发率显著降低;水层对马唐影响较大,水层处理可显著降低马唐的出苗率;随着土层深度的增加,马唐出苗率逐渐降低,土层深度〉7cm则马唐不能出苗。     

Dependence of weed flora on the active soil seedbank

Previous studies have shown that reliable predictions of the above-ground weed flora may not be obtainable by using the total number of seeds in the seedbank. The purpose of this study was to determine if the actual weed flora depends on the active soil seedbank (seeds that are germinable in the spring). In the 1995 growing season, seedling emergence was monitored within permanent quadrats established in a field. Soil cores taken from the same field were also monitored for seedling emergence in a greenhouse to estimate the number of seeds in the active soil seedbank. Significant positive relationships were observed between the above two variables based on either total weed flora or individual weed species commonly found in south-western Ontario, Canada. For relatively large-seeded species, the relationship held with a sampling depth up to 15 cm below the soil surface. For small-seeded species, a shallow sampling depth (0–7·5 cm) generated better results than deeper sampling (0–15 cm). In general, 3–7% of the seeds in the active soil seedbank were capable of producing seedlings in the field. The results suggest that the level of weed infestation in a growing season may be predicted using seeds in the active soil seedbank.     

秸秆还田及施肥对小麦复种油菜农田土壤呼吸的影响

在甘肃省石羊河绿洲灌区连续3 a的小麦复种油菜田间定位试验的基础上,采用EGM-4密闭式土壤呼吸测量系统,测定了不同施肥水平和不同秸秆还田方式下小麦复种油菜农田的土壤呼吸速率。结果表明：在整个观测期内, 土壤呼吸速率最高值出现在8月下旬（152.06~199.58 mg•m^-2•h^-1）,最低值出现在10月中旬（12.67~19.01 mg•m^-2•h^-1）。土壤呼吸速率日变化呈单峰曲线,最高值出现在12:00-14:00, 4:00左右达最低值;不同秸秆还田方式下, 高茬收割免耕播种油菜的处理明显降低了土壤呼吸速率,且在秸秆处理后的油菜生育期内降低效果更加明显;不同施肥水平下,在N、P减量15%的情况下,土壤呼吸速率显著下降;各试验处理措施下, 土壤呼吸速率与5 cm和10 cm土壤温度、30 cm各层土壤含水量均呈极显著正相关,并且土壤呼吸速率与0~30 cm土壤水分的相关性较土壤温度高;不同处理下土壤呼吸速率与土壤孔隙度基本上呈负相关,但是两者之间相关性并不显著。     

Effect of rhizome fragment length and burial depth on emergence of Tussilago farfara

Mechanical control of Tussilago farfara is carried out mainly by soil cultivation. The aim is to deplete the energy stored in the rhizomes. The treatment includes cutting the rhizomes, to stimulate increased shooting, followed by renewed soil cultivation to destroy the shoots and incorporate them into the soil. Factors generally regarded as important in the control of perennial weeds are extent of fragmentation and burial depth. In this study, the importance of these two factors on T. farfara emergence was studied in detail in two pot experiments. Rhizomes were cut into different lengths (5–25 cm) and buried at various depths (1–42 cm) in pots filled with peat soil or clay loam. Shoot germination, emergence and early plant performance were studied. Intensive fragmentation and deep burial (possible to achieve using conventional tillage) are not enough to completely hinder emergence of T. farfara; 6‐cm fragments emerged and developed normal leaves from 42 cm depth, regardless of soil type. However, there were higher total emergence and emergence rates in peat soil than in clay soil. Burial depth was correlated with time to emergence; burying rhizome fragments, not longer than 25 cm, to at least 20 cm depth gave a time to emergence of at least 20 days. The delay of weed emergence should allow good establishment of a crop and ensure a significant competitive effect against T. farfara.