关中棉区棉铃虫测报资料统计标准的初步研究

以1971～1987年陕西关中主要产棉县一类棉田棉铃虫系统观测资料为依据,对影响其发生的主要因素进行分析,提出将关中棉区棉铃虫发生期统计标准分为渭、洛河下游早发区和泾、渭、沣河迟发区两个类型,并分别制定了棉铃虫发生期、发生程度、为害损失的统计标准。经对大荔、泾阳棉铃虫测报资料检验,历史符合率为97.6％,与发生实际相吻合。     

马铃薯大西洋组培苗的生根诱导及移栽

对马铃薯大西洋组培苗进行壮苗,在1/2M S培养基中添加不同浓度IAA、IBA对大西洋进行生根诱导和移栽研究。结果表明,大西洋组培苗壮苗后,在生根诱导培养时添加IBA的效果较好;最低生根培养浓度为0.4mg/L IBA;以东北土∶(花土 炉渣)=2∶1为移栽基质,在灭菌条件下,1/2M S 0.6mg/L IBA培养基中组培苗移栽的成活率最高,可达87.61%,而1/2M S 0.4mg/L IAA的移栽成活率仅为41.23%。因此,在生产中,推荐使用0.6mg/L IBA,有利于大西洋组培苗生根诱导和移栽。     

播期对不同专用型小麦籽粒灌浆特征参数和产量的影响

以3个不同专用型小麦品种为材料,研究了不同播期条件下籽粒灌浆特征参数、粒重和产量的差异。结果表明:3个专用型小麦品种平均灌浆速率(V)均以中播为最高,灌浆持续期(S)和有效灌浆持续期(Se)以早播最长;平均灌浆速率与最大百粒重之间呈显著正相关;3个不同专用型小麦品种最大百粒重和产量均以中播为最高,晚播最低。     

杂交水稻两优培九安全齐穗期和适宜播种期的研究

以协优9308和汕优63为对照，研究两优培九在浙南作连作晚稻栽培的安全齐穗期和适宜播种期。两年的试验表明，两优培九6月21日之前为适宜播种期，能达到安全齐穗，产量稳定，每穗总粒数和结实率高；6月21日以后播种，每穗总粒数和结实率下降；6月27日以后播种，结实率急剧下降。两优培九感温性强、感光性弱，6月12日至6月27日播种播始历期仅相差2d。6月27日以后播种，由于幼穗分化期低温，两优培九的播始历期反而延长。试验还发现抽穗期低温会延长水稻始穗至齐穗期，相对于对照协优9308和汕优63，两优培九对抽穗期低温不敏感。两优培九在浙南的光温条件下作连作晚稻栽培是安全的。     

关中灌区夏播陕单8806玉米密度与播期耦合技术研究

【研究目的】为了明确陕单8806玉米在关中灌区种植的适宜播期和合理密度,从而使优良品种与地区生态环境相适应,发挥群体优势而夺取高产。【方法】采用二次饱和-D最优试验设计,研究了密度与播期对陕单8806玉米籽粒产量和生物学产量及农艺性状的影响。【结果】明确了在关中灌区夏播条件下,播期对玉米的影响效应显著大于密度,关中灌区夏玉米生产应力争早播。【结论】通过对玉米产量及农艺性状与密度和播期二因素建立的数学模型的回归分析,筛选确定了陕单8806玉米在关中灌区夏播的适宜播期为6月11日—18日,合理种植密度为60494￣70442株/hm2。     

Influence of species, cutting date and cutting interval on the fatty acid composition of grasses

Two experiments were conducted to evaluate the effects of species, cutting date and cutting interval on the concentration of fatty acids in temperate grasses. The first experiment compared eight species, harvested in late autumn and summer. Levels of individual fatty acids were distinctive for some species, with low levels of C18:1 in Dactylis glomerata L. and high levels of C18:2 in Phleum pratense L. Differences in individual fatty acids could not be used to differentiate fescues and ryegrasses. However, fatty acid profiles could be used to differentiate species when material was managed similarly (i.e. at the same cut). There were large species × cut interaction effects, showing that management factors will be as important as plant breeding in manipulating fatty acid levels. Cultivars belonging to one Lolium perenne L. gene pool were identified as having significantly higher α-linolenic acid and total fatty acids in late-season (November) material.
The second experiment compared three ryegrass species over a growing season, with three or five cuts. All species had high concentrations of fatty acids and a high proportion of α-linolenic acid during vegetative growth (late April). Fatty acid levels declined markedly in all species after this date, recovering by autumn. Kunth Lolium multiflorum Lam. and Lolium  ×  boucheanum had higher levels of total fatty acids and α-linolenic acid in the early and late season when compared with perennial ryegrass. Fatty acid levels (particularly C18:2 and C18:3) declined when the regrowth interval was extended from 20 to 38 d.
These studies demonstrate opportunities to change the composition of ruminant products through breeding and management of grasses for altered levels of fatty acids.     

播种期和某些质量遗传基因对大豆籽粒斑驳形成的影响

以25份克拉克和6份哈罗索近等基因系为试材,研究了播种时期,成熟期,结荚习性,抑制褐斑形成,抗病毒病及某些控制种皮颜色基因对大豆籽粒斑驳形成的影响。采用完全随机区组裂区设计。研究结果表明,播种时期对大豆的成熟期,大豆花叶病毒病及籽粒斑驳的严重度具有很大的影响。随着播期的推迟,从苗期到成熟所需要的日数明显减少,病毒病、斑驳粒率(PMS)和斑驳指数(MI)明显减轻。基因替换效应分析表明,tE1,E2,E3,Im和Rsv1对减轻籽粒斑驳症状具有显著的效应。当上述基因被其隐性等位基因替换时,斑驳粒率和斑驳指数分别减少32.1％和0.205,8.8％和0.043,6.3％和0.031,27.1％和0.212,25.3％和0.156。TE1,i—k和iR对加重籽粒斑驳的形成具有显著的效应,当这几个基因或基因组合被tel,i—i和Ir所替换时斑驳粒率和斑驳指数分别降低13.8％和0.126,28.7％和0.449,6.43％和0.115。虽然R和Dtl对大豆花叶病毒病症状表现有较大的影响,但是对籽粒斑驳的形成影响不大。     

Amount and quality of grass harvested for first-cut silage for differing spring-grazing frequencies of two mixtures of perennial ryegrass cultivars with contrasting heading date

There are potential advantages and disadvantages associated with grazing spring perennial ryegrass swards designated for first‐cut silage. These may differ for intermediate‐heading (0·50 ear emergence in the second half of May) and late‐heading (0·50 ear emergence in the first half of June) cultivars. The interactions between cultivar type, spring‐grazing frequency, silage‐harvest date and year were examined in an experiment with a randomized complete block (n = 4) design with a factorial arrangement of treatments, conducted in Ireland. The factors were (i) two perennial ryegrass mixtures: intermediate‐ vs. late‐heading cultivars, (ii) three spring‐grazing regimes: no grazing, grazing in mid‐March or grazing in both mid‐March and mid‐April, (iii) four first‐cut silage‐harvest dates that were at c. 10‐d intervals from 19 May and (iv) 2 years (1998 and 1999). The effects of cultivar mixture on herbage mass of the swards in spring were small and not statistically significant. The late‐heading cultivars provided lower amounts of herbage dry matter for harvesting for first‐cut silage but herbage with higher in vitro organic digestibility values compared with intermediate‐heading cultivars. To achieve the same amount of herbage for silage, the late‐heading cultivars needed to be harvested 8 d later than the intermediate‐heading cultivars. Even with this delay in harvest date, the late‐heading cultivars had higher in vitro organic digestibility values than the intermediate‐heading cultivars. The late‐heading cultivars could be harvested up to 30 d later and produce a higher amount of herbage for first‐cut silage with similar digestibility values compared with the intermediate‐heading cultivars.     

Spring and autumn establishment of Caucasian and white clovers with different sowing rates of perennial ryegrass

The effect of sowing date (SD) and sowing rate of perennial ryegrass (PRG) on the establishment of Caucasian and white clovers in New Zealand was assessed. Clovers were sown in spring on 24 September (SD1) and 9 November (SD2) 1999, and in autumn on 4 February (SD3) and 31 March (SD4) 2000. On each date, clovers were sown with 0, 3, 6 or 12 kg ha^?1 of PRG. Total herbage dry matter (DM) production up to 6 November 2000 was 13–16 t DM ha^?1 for SD1 and SD2 when sown with 3–12 kg ha^?1 of PRG, and 7–10 t DM ha^?1 for sown clover monocultures. For SD3 and SD4, total herbage production was 6–9 t DM ha^?1 with PRG, while total herbage production of clover monocultures was 5·4 t DM ha^?1 for SD3 and 2·6 t DM ha^?1 for SD4. By 6 November 2000, white clover contributed proportionately more than 0·15 of herbage mass when sown with 3–12 kg ha^?1 of PRG on SD1, SD2 or SD3, but less than 0·09 when sown on SD4. The proportion of Caucasian clover never exceeded 0·09 of herbage mass in any of the swards. White clover was successfully established in spring and in autumn with 3–12 kg ha^?1 of PRG provided the 15‐mm soil temperature was above 14 °C. None of the combinations of Caucasian clover and PRG provided an adequate proportion of legumes during the establishment year. This unsuccessful establishment of Caucasian clover with PRG was attributed to its inability to compete for available light as a seedling due to slow leaf area expansion from secondary shoot development and a high root:shoot ratio. Alternative establishment strategies for Caucasian clover may include the use of slow establishing grasses, cover crops and temporal species separation.     

Remote sensing assessment of regional yield losses due to sub-optimal planting dates and fallow period weed management

New tools in agricultural research are needed for improved assessment of agronomic practices and their impacts on crop production. Remote sensing data acquired by satellite sensors offers great promise to complement field-based approaches, which generally suffer from small sample sizes. In this study, we used Landsat data from the Yaqui Valley, a prominent spring wheat (Triticum aestivum L.) growing region in Northwest Mexico, to investigate the effect of planting date and fallow period weeds on wheat yields. Three crops cycles were analyzed for the planting date study, while 2 years were investigated for the weed study.