苗期渍水对直播冬油菜产量和农学利用率的影响及油菜在不同氮肥施用下的响应

在轻简化施肥背景下,为减少渍害损失,解决长江流域冬油菜产区生产面临的重要问题,开展氮肥施用 对油菜渍害的缓解作用研究。设置三因素田间试验,分别为不同氮肥用量（0、60、120、180、240和300 kg N/hm2）、氮 肥类型（油菜专用控释尿素和普通尿素）和水分处理（苗期渍水和正常排水）,测定各处理产量和氮肥农学利用率, 明确苗期渍水对不同氮素供应水平油菜的影响,并比较油菜专用控释尿素一次性施用和普通尿素分次施用下油菜 对苗期渍水的响应。结果表明,直播冬油菜产量随氮肥施用量增加而提高,至240 kg N/hm2时不再增加。油菜专用 控释尿素一次性施用,在氮肥用量为60～180 kg N/hm2时产量高于普通尿素分次施用;在氮肥用量为240～300 kg N/hm2时,两种氮肥类型产量基本相当。氮肥施用通过增加收获密度、单株角果数和每角粒数提高产量。苗期渍水 导致直播冬油菜产量损失1.1%～41.9%,随氮肥用量增加,渍水引起的产量损失率呈先增加后降低趋势。0～60 kg N/hm2处理时,渍水使收获密度显著降低（降幅达29.4%~45.0%）,单株角果数增加;施氮量为120~180 kg N/hm2时, 渍水导致收获密度和单株角果数分别降低19.5%~33.7%和1.4%~17.7%;施氮高于180 kg N/hm2时,收获密度和单 株角果数降幅减小（降幅分别为5%~30.9%和3.6%~9.5%）。普通尿素分次施用和油菜专用控释尿素一次性施用, 分别在施氮量为120和180 kg N/hm2时产量损失率最高,分别达29.8%和41.9%。相同氮肥用量下油菜专用控释尿 素一次性施用的产量损失率大于普通尿素分次施用。渍水显著降低氮肥农学利用率,降幅为8.4%～51.9%,施氮充 足（240～300 kg N/hm2）时氮肥农学利用率降幅低于氮素用量较低处理（120～180 kg N/hm2）,油菜专用控释尿素一 次施用处理的农学利用率平均降幅（36.5%）高于普通尿素分次施用（17.3%）。综上可知,苗期渍水时,油菜专用控 释尿素一次施用,会加重油菜受渍影响;土壤氮素供应能力较低时,渍害逆境解除后,适量追施速效氮肥可有效缓 解产量损失,实现油菜稳产。     

高密度直播油菜氮磷钾肥推荐用量及影响因素

针对我国目前油菜生产上施肥过量与不足并存,肥料利用率低的问题,运用“3414”试验方案进行一年多点田间试验,研究了高密度(375 000株/hm2)直播油菜氮磷钾肥的适宜用量。结果表明,氮磷钾肥不同用量显著影响油菜籽粒产量,通过建立施肥与产量间的效应函数方程,得出供试条件下油菜氮磷钾肥推荐施用量,桂林试验点油菜产量2 416.3kg/hm2,施用量为N 118.5 kg/hm2、P2O5 36.5kg/hm2、K2O 60.6 kg/hm2;枝江试验点油菜产量3 095.1kg/hm2,施用量为N 176.3 kg/hm2、P2O5 73.0kg/hm2、K2O 100.6 kg/hm2;玉龙试验点油菜产量4 474.3kg/hm2,施用量为N 256.7 kg/hm2、P2O5 88.1kg/hm2、K2O 137.7 kg/hm2。结论认为不同地理区域和不同油菜品种在该区域生长发育的生态学特征,以及肥料的边际利润率、肥料和产品价格是油菜推荐施肥的重要依据,不能简单依据供试土壤基础肥力进行油菜推荐施肥。 [     

氮磷钾肥施用对甘蓝型春油菜产量及肥料利用效率的影响

利用大田试验研究了氮、磷、钾肥对青海省互助县种植的甘蓝型春油菜产量、养分吸收量和肥料利用效率等指标的影响。结果表明,氮肥和磷肥对春油菜(甘蓝型杂交油菜青杂2号)籽粒产量的提高有显著作用,钾肥的影响相对较小;与不施肥对照相比,氮、磷、钾肥的施用可显著促进成熟期春油菜地上部N、P、K素累积量(P<0.05);不同肥料的春油菜农学利用率分别为5.3kg/kg N、5.6kg/kg P2O5和1.7kg/kg K2O;肥料表观利用率分别为N 33.6%、P2O5 7.8%和K2O 52.0%, N、P、K肥对油菜籽产量的偏生产力分别为28.0kg/kg N、46.7kg/kg P2O5和26kg/kg K2O。青海省互助县种植条件下,当春油菜产量水平在3 504kg/hm2时,NPK配施条件下每生产100kg籽粒需要吸收N、P2O5、K2O量分别为4.6kg、2.0kg和5.6kg,氮磷钾比为1:0.43:1.21。油菜生产实践中实现高产目标需同时关注地力培肥和平衡施肥两方面。     

Responses of Seed Yield and Quality to Nitrogen Application Levels in Two Oilseed Rape (Brassica napus L.) Varieties Differing in Nitrogen Efficiency

Abstract

The relationship between nitrogen efficiency (NE), defined as seed yield per unit nitrogen (N) application, and seed quality was examined in two oilseed rape (Brassica napus L.) varieties at 5 N application levels, 0.6, 3, 6, 12, 15 mmol L?¹, N₁, N₂, N₃, N₄ and N₅, respectively. Seed yield, oil yield and protein content were increased with the increase in N application level, but NE and oil content were decreased, and the fatty acid composition in seed was hardly changed. Analysis of seven fatty acids revealed aslight decrease in the contents of erucic acid and arachidonic acid with the increase in N application level, but no obvious change in the contents of palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid. Compared with the low NE variety H29, the seed yield and contents of erucic acid and arachidonic acid in the high NE variety bin270 were more markedly increased with the increase in N application level, and the oil content was hardly changed. The seed yield, oilcontent and oil yield were higher in the high NE variety than in the low NE variety at all 5 N application levels. There were no significant differences in protein, palmitic acid, stearic acid and oleic acid contents between the varieties at any of the 5 N application levels, but there were slight differences in the linoleic acid and linolenic acid contents between the two varieties. In brief, N application improved oil yield more greatly in the high NE variety than in the low NE variety, but hardly affected the fatty acid composition. Therefore, the seed quality and oil content of oilseed rape may not be decreased by breeding of a high NE variety with a high N absorption efficiency and high N use efficiency.     

Yield and oil variability in modern varieties of high-erucic winter oilseed rape (Brassica napus L. var. oleifera) and Ethiopian mustard (Brassica carinata A. Braun) under reduced agricultural inputs

Increasing interest in vegetable oils for use in green chemistry has stimulated research into high-erucic Brassicaceae species such as winter oilseed rape (Brassica napus L. var. oleifera) and Ethiopian mustard (Brassica carinata A. Braun). The objective of this study was to determine the yield response of recently released cultivars of these species under high and low production inputs. The varieties Maplus and Hearty of B. napus, and BRK1 of B. carinata were cultivated with autumn sowing in a large-scale field trial at the experimental farm of the University of Padova in Legnaro (NE Italy, 45°21′N). The genotypes were compared under high and low input management systems: high input was characterised by conventional soil tillage, chemical weed control, and high N–P–K fertilization, and low input by minimum tillage, mechanical weed control, and limited N–P–K fertilization.Oilseed rape varieties had greater seed yield than BRK1, and interactions with input level and cultivation year were significant. Maplus yielded most at high input (3.78 vs. 3.31 t ha⁻¹ DM at low; average of two years), whereas Hearty showed no significant differences between inputs (3.49 t ha⁻¹; average of years and inputs), indicating its better adaptability to extensive agricultural management. Yield performance of BRK1 B. carinata was very stable at varying agricultural managements, but not very high (2.73 t ha⁻¹ on average) – a fact that may limit its competitiveness with oilseed rape in autumn sowing, especially at higher latitudes. B. carinata was also more variable across the years than oilseed rape in terms of seed yield, oil content, and percentage of erucic acid. This was mainly due to the particular climatic conditions of the second year of the experiment (mild winter; hot, dry spring) which led to considerable winter elongation and pre-flowering, and later to incomplete seed filling. In these conditions, BRK1 had both lower oil seed content (36.7% vs. 47.1%) and erucic acid (41.3% vs. 49.1%) than oilseed rapes.In general, with few exceptions, the reduction in inputs did not affect either seed oil content or the amount of erucic acid, regardless of variety and year, but seed crude proteins were reduced mainly because of N shortage.     

甘蓝型油菜不同硼效率基因型对硼的吸收、分配的影响

在土培条件下,研究了甘蓝型油菜不同硼效率基因型对硼的吸收、分配和运转。结果表明,甘蓝型油菜硼效率不同基因型的差异首先表现在植株对硼的吸收能力上,特别是缺硼胁迫时高效品种的吸收能力更明显大于低效品种。其次在硼的分配、运转和再利用上,高效品种繁殖器官分配的硼多于低效品种,缺硼时硼的运转和再利用能力高效品种大于低效品种     

氮素营养对油菜成熟期生物产量的调控

通过不同Ｎ肥处理的田间试验,研究Ｎ素营养对油菜成熟期地上部各部位生物产量的调节作用。结果表明,主茎的生物产量随施Ｎ量的增加而明显增加;分枝、果序和果壳重以及籽粒产量随施Ｎ量的增加先增后减。在生物产量中,果壳重与籽粒产量的关系最为密切,生产上保证前期主茎和要枝有一定生长量的基础上,通过合理施Ｎ以促进后期角果的生长,提高果壳的重量可提高籽粒产量。     

不同蛋白质含量大豆品种氮素积累、分配和运转规律研究

以3个籽粒产量相近但蛋白质含量差别较大的大豆品种为材料,分析了分枝期后不同器官的氮素积累、分配和运转规律及其对籽粒蛋白质含量的影响.结果表明:结荚前品种之间氮素含量和积累量差别不大,结荚后高蛋白大豆营养器官(叶片、茎秆和叶柄)的氮素含量除个别时期外(叶柄第7周)都高于普通大豆,说明营养器官较高的氮素含量及长时间保持较高...     

Persistence of an oilseed rape transgene in the environment

Transgenic bromoxynil (BX)-resistant spring oilseed rape (Brassica napus L.) was grown commercially in Canada only for two crop seasons – 2000 and 2001. We investigated the persistence of suspected BX-resistant oilseed rape volunteers in a 64-ha wheat field in Saskatchewan, Canada in 2007, 7 years after the BX-resistant cultivar BX Armor was grown. A small oilseed rape volunteer population, estimated at less than 100 plants, was observed in three main areas or patches in the field. These patches were located in low-lying areas that were too wet to plant or spray with herbicides in 2007. Viable seed was collected from 35 mature volunteers and F₁ progeny screened with BX at 280 g ai/ha in the greenhouse. Progeny of all of the volunteers were visually rated as BX-resistant; the presence of the Oxy 235 transgene in leaf tissue of progeny of all volunteers was confirmed by PCR analysis. This study has documented the longest persistence of oilseed rape volunteers in Canada. Volunteers were not observed in 2008 or 2009, because of drought conditions in spring of both years. Results support the findings from previous studies that persistence of volunteer oilseed rape populations in western Canada is generally ephemeral or transitory in the absence of seed bank immigration. However, this study shows that oilseed rape transgenes can persist in the environment for a number of years even after all cultivars with the conferred trait are removed from the market.     

Impact of Agronomic Strategies (Seed Tuber Pre-sprouting,Cultivar Choice) to Control Late Blight (<Emphasis Type="Italic">Phytophthora infestans</Emphasis>) on Tuber Growth and Yield in Organic Potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.) Crops

In order to optimize potato crop management in organic farming systems, knowledge of crop growth processes in relation to limitations and reductions by nitrogen (N) and disease is necessary. This paper examines the effect of different prevention measures (seed tuber pre-sprouting, choice of cultivars: resistance to Phytophthora infestans; earliness of tuber initiation) against disease-related constraints on yields, depending on the N-mediated growing conditions of organic potato crops. Under conditions of a relatively high N supply, accelerating the early development and tuber initiation of potato crops by seed tuber pre-sprouting (yield increase of c. 18–23%) or the selective choice of cultivars with an earlier tuber initiation (yield increase of c. 0–21%) are the most effective strategies in combating late blight. They bring forward the crop development c. 7–10 days, escaping the negative impact of the fungus on tuber growth. Under conditions of a relatively low N supply, these strategies do not affect final tuber yield. The reason for the differences of the effect depending on N supply of the crops is, that the lower the N supply, the shorter the period of time over which tuber growth takes place, independent of whether P. infestans becomes severe or not. Tuber growth of organic crops low in N has mostly ceased by the time late blight becomes potentially important for limiting yield, with the consequence that preventative measures against P. infestans are meaningless. Surprisingly, the level of cultivar haulm resistance to late blight did not affect tuber yields in years with an early and strong late blight development. Probably, the positive effect of a longer resistance to the fungus (c. 1 week) was counterbalanced by a later tuber initiation (also c. 1 week). In years with a moderate late blight incidence, less susceptible cultivars were able to produce higher tuber yields on fields with a lower N availability (c. 17–20%), probably due to higher N use efficiency and a better match of N mineralization and N uptake. Under conditions of a relatively high N supply, the tested cultivars with a higher haulm resistance to late blight were not able to improve tuber yields.     

油菜品种和资源材料 对芜菁花叶病毒的抗性鉴定

在人工接种高病害压条件下,对当前生产上应用的13个油菜双低和杂交品种及14份资源材料进行了 对芜菁花叶病毒( TuMV)的抗性鉴定。结果表明,参试的13个油菜品种均不抗TuMV,但感病性低于对照品种中油 821。14份油菜资源材料间抗性差异显著,有3份材料表现高抗和中抗。大部分油菜推广品种表现的高发病率和 病情指数表明在病害流行地区和年份,这些品种不足以抵挡病毒病造成的损失。     

选育高含油量双低油菜品种的理论与实践

含油量作为油菜生产最终目标性状产油量的组成因素,与油菜生产效益的提高息息相关。在目前我国 油菜产量水平已得到相当程度提高的前提下,培育高含油量油菜品种是进一步发展油菜产业的必由之路。根据油 菜含油量的遗传特点,结合培育高含油量杂交油菜品种中油杂8号和中油杂11的体会,提出了除了利用黄籽以 外,培育大粒和适宜植株形态性状的品种也是提高油菜含油量的重要途径。初步构建了高含油量油菜品种的形态 组成,并基于近年来参加和通过国家区域试验的冬油菜品种含油量变化情况,展望了我国高含油量油菜育种的发 展前景。     

不同生态条件下品种和施氮量对冬小麦产量及氮肥利用效率的影响

为给河南省不同生态区域小麦氮肥高效利用提供理论依据,于2012-2013年在南阳和信阳2个地点,2013-2014年南阳、信阳和郑州3个地点,通过田间试验研究了施氮量对10个小麦品种产量和氮肥利用效率的影响。结果表明,小麦产量和氮肥利用效率均显著受品种、地点和施氮水平的影响,同时显著存在品种×地点和地点×施氮量的互作效应;其中,品种效应相对较小,地点对产量和氮肥农学利用效率的影响较大,施氮水平对氮肥偏生产力的调控效应最大。10个品种中,周麦28在各地点均获得了较高的产量和氮肥偏生产力,表现出较好的适应性。3个地点中,郑州和南阳的小麦产量和氮肥偏生产力均显著高于信阳,而信阳具有较高的氮肥农学利用效率,说明适量的氮肥供给对于信阳改善小麦生产非常重要。增施氮肥可以显著提高小麦产量,但降低了氮肥偏生产力和氮肥农学利用效率,且不同地点和品种对施氮水平的响应存在差异。综合各品种产量和氮肥利用效率对施氮水平的响应,在3个地点小麦在较低施氮水平(120kg·hm-2)下均可达到高产高效的生产目标,但各地点也存在需要高氮肥投入的小麦品种,如郑州的郑麦3596、南阳的洛麦24及信阳的西农509和宛麦16。     

东北地区玉米氮高效品种筛选及产量组成因素分析

为了筛选适宜农民种植的高产、养分高效玉米品种,提高东北地区的氮肥利用率,在吉林梨树、辽宁铁岭和黑龙江哈尔滨设置高氮与低氮两个氮水平,各选择20个玉米品种,通过两年定位的田间试验,对其产量及其组成因素进行分析。结果表明,在吉林梨树县地区,良玉918和德美1号两年均表现为双高效品种,先玉335和迪锋128均表现为高氮高效型品种。在辽宁铁岭地区双高效品种有宏硕899、锦华299、沈玉21和迪卡159,先玉335表现为高氮高效品种。在黑龙江哈尔滨,京科728、天农9、誉成1、先玉335为双高效品种,高氮高效品种是德育919和益农玉10。与所有供试品种的平均值相比,两年3个地点平均,双高效品种在正常施氮、低氮条件下分别增产12.8%和16.2%。高氮高效型品种在正常施氮条件下的增产率为6.4%。两个氮水平下,双高效品种具有较多的穗数和穗粒数,高氮高效品种仅在高氮水平下具有较多的穗粒数,低氮高效品种仅在低氮水平下具有较高的穗粒数。     

Nitrogen utilization efficiency of safflower hybrids and open-pollinated varieties under Mediterranean conditions

The identification of the factors determining nutrient utilization of safflower (Carthamus tinctorius L.) is useful for the successful introduction of the crop to the cropping system of a region. A field study was conducted to compare and analyze the relative importance of the various component traits causing variation in nitrogen utilization efficiency (NUE) of safflower under Mediterranean conditions. Ten genotypes, four hybrids and six open-pollinated varieties, were grown for two growing seasons without irrigation, on a silty clay (Typic Xerorthent) soil. Seed yield varied greatly among genotypes and ranged from 923 to 3391 kg ha⁻¹. Hybrids showed a mean seed yield superiority of 12.5% against varieties. Seed yield was the most important component of seed N yield and its contribution to the total variation in seed N yield among genotypes was at least 53%. NUE for biomass production during the seed-filling period was lower compared to that during the vegetative period. Genotypes differed in NUE for seed production (NUE_s) and the differences followed those of nitrogen harvest index (NHI). The contribution of NHI to the total variation in NUE_s among genotypes was much greater compared to that of yield per unit seed nitrogen and accounted for more than 79%. NUE_s is positively correlated with seed yield, suggesting that high yield was probably associated with more efficient exploitation of nitrogen. NUE_s is negatively correlated with (leaf + stem) N concentration at maturity, meaning that low straw N concentration may be indication of higher NUE_s. Results indicated that selection for NUE in safflower should be based on multiple criteria rather than just one criterion and also should be accompanied by evaluation for seed yield to ensure an improvement in both traits.     

Effect of winter cover crop species and planting methods on maize yield and N availability under irrigated Mediterranean conditions

Under semiarid Mediterranean conditions irrigated maize has been associated to diffuse nitrate pollution of surface and groundwater. Cover crops grown during winter combined with reduced N fertilization to maize could reduce N leaching risks while maintaining maize productivity. A field experiment was conducted testing two different cover crop planting methods (direct seeding versus seeding after conventional tillage operations) and four different cover crops species (barley, oilseed rape, winter rape, and common vetch), and a control (bare soil). The experiment started in November 2006 after a maize crop fertilized with 300 kg N ha⁻¹ and included two complete cover crop-maize rotations. Maize was fertilized with 300 kg N ha⁻¹ at the control treatment, and this amount was reduced to 250 kg N ha⁻¹ in maize after a cover crop. Direct seeding of the cover crops allowed earlier planting dates than seeding after conventional tillage, producing greater cover crop biomass and N uptake of all species in the first year. In the following year, direct seeding did not increase cover crop biomass due to a poorer plant establishment. Barley produced more biomass than the other species but its N concentration was much lower than in the other cover crops, resulting in higher C:N ratio (>26). Cover crops reduced the N leaching risks as soil N content in spring and at maize harvest was reduced compared to the control treatment. Maize yield was reduced by 4 Mg ha⁻¹ after barley in 2007 and by 1 Mg ha⁻¹ after barley and oilseed rape in 2008. The maize yield reduction was due to an N deficiency caused by insufficient N mineralization from the cover crops due to a high C:N ratio (barley) or low biomass N content (oilseed rape) and/or lack of synchronization with maize N uptake. Indirect chlorophyll measurements in maize leaves were useful to detect N deficiency in maize after cover crops. The use of vetch, winter rape and oilseed rape cover crops combined with a reduced N fertilization to maize was efficient for reducing N leaching risks while maintaining maize productivity. However, the reduction of maize yield after barley makes difficult its use as cover crop.     

Effects of Potato Cultivar on the Components of Nitrogen Use Efficiency

Maximising potato nitrogen use efficiency (NUE) is necessary to combine high yields, market requirements, high economic income and low environmental impact. A 5-year study was conducted to assess the cultivar effect on NUE components in France. Seven trials were carried out in the Beauce, Picardie and Nord-Pas de Calais regions. The protocol combined two factors: cultivar (‘Agata’, ‘Bintje’, ‘Innovator’, ‘Lady Claire’ and ‘Spirit’) and nitrogen application along a complete response curve (six to seven rates). Total tuber yield, 50 mm tuber yield and nitrogen uptake at haulm killing were measured. We demonstrate that the potato cultivar has a clear effect on NUE components. This effect is supported both by nitrogen uptake efficiency (NupE) and by nitrogen utilisation efficiency (NutE). It implies that the potato cultivars tested generate different nitrogen requirements per yield unit to reach the optimum yield. The way to characterise these differences for all cultivars available in registration trials must be considered before taking into account a cultivar effect on NUE in nitrogen recommendations for farmers.     

大田追施硫肥对双低油菜产量与品质的影响

硫酸盐肥料以S10或40kg／hm2分别在油菜的出苗期、莲座期、现蕾期、抽薹期及初花期施入缺硫土壤，并在出苗期结合施用氮肥N80或160kg／hm2。结果表明，对照区植株在抽薹期表现出严重的缺硫症状，特别是单施N160kg／hm2的小区。追施S10kg／hm2可显著提高油菜产量及含油量，但追施时期间差异未达到显著性水准，这一施用量明显不足，油菜籽产量远低于施S40kg／hm2处理。迟于花期追施S40kg／hm2，籽粒产量较前期减少约20％。此外，施S40kg／hm2还可明显提高籽粒的蛋白质含量。对缺硫植株，籽粒N：S比大于10，而供硫适宜植株为7．5。总硫代葡萄糖甙含量随施硫量的增加而提高，且后期追施明显高于前期。     

Varietal Difference in Nitrogen Redistribution from Leaves and Its Contribution to Seed Yield in Soybean

A large amount of nitrogen is redistributed from vegetative organs to the seeds during seed filling in soybean (Glycine max [L.] Merrill). However, the effect of nitrogen redistributed from leaves on the seed yield production is not clear. We evaluated the varietal difference in nitrogen redistribution and its contribution to the seed yield. Ten soybean cultivars were cultivated under conventional conditions in the field in Saga, Japan. The plant samples were collected at various reproductive stages, and then the nitrogen contents in each part were determined. The redistributed nitrogen was estimated by the difference in the nitrogen contents of leaves between the plants at the R5 and R7 stages. The nitrogen content of leaves began decreasing after R5 stage in all cultivars, indicating the start of nitrogen redistribution. About 13.8% to 37.9% of the total nitrogen in the seeds was estimated to have been redistributed from the leaf tissues in the ten cultivars. The seed yield was correlated positively with the amount of redistributed nitrogen from leaves but neither with the nitrogen concentration in the leaves at R5 nor with the proportion of redistributed nitrogen in the seeds. However, in high seed yielding years, 2008 and 2009, the seed yield was not associated with nitrogen redistribution; and the lowest nitrogen redistribution was associated with a relatively high seed yield in Tamahomare. Our results indicated that redistribution of a large amount of nitrogen does not always contribute to high seed yielding, implying the direct nitrogen uptake during seed filling could be more important factor for high seed yielding depending on the cultivars.     

Association of growth dynamics, yield components and seed quality in long-term trials covering rapeseed cultivation history at high latitudes

Brassica oilseed yield trend has declined in Finland by over 20% during the last 15 years. Improved genetic yield potential of turnip rape (B. rapa L.) and oilseed rape (B. napus L.) can be better realised with increased understanding of yield determining processes under northernmost growing conditions. This study aimed at (1) determining the genetic improvements in seed yield, yield components, quality traits and duration of the main growth phases and (2) comparing all these traits in turnip rape and oilseed rape. This work is based on the dataset from long-term Official Variety Trials (1976–2006), covering the entire historically relevant period of rapeseed cultivation in Finland. The results indicated that number of seeds per square metre dominated production of high yields, while single seed weight was not correlated with yield. Over the years, seed yields were produced with very different combinations of seed numbers and weights, differing markedly between the two crops. While high seed numbers were required for production of superior seed yields, single seed weights were not particularly high. Environmental variation markedly affected seed yield, seed number per square metre and duration of flowering compared with its effect on single seed weight. Duration of flowering was, however, negatively associated with seed number. Even though seed weight was largely determined by genotype, no marked plant breeding improvements were identified, contrary to those in number of seeds per square metre, seed yield, oil content and oil yield. For oilseed rape the increase in seed yield (41%) was far higher than for turnip rape (19%) without being associated with a longer seed-filling phase and later ripening, but rather the contrary.