Population dynamics of volunteer oilseed rape (Brassica napus L.) affected by tillage

Volunteer plants of oilseed rape (Brassica napus L.) from persistent seeds in soil can affect subsequent crops. Apart from the agricultural disadvantages, the environment and the marketing of the seeds may also be affected, particularly if plants with special ingredients or genetically modified (gm) plants are grown. In order to investigate the influence of soil cultivation and genotype on seed persistence and gene flow via volunteers, a field experiment was set up testing four tillage treatments and two cultivars in a split-plot design. The cultivars tested were near-isogenic to two gm cultivars. To simulate harvesting losses, 10 000 seeds m⁻² were broadcast on a soil in July. The subsequent tillage treatments were combinations of immediate or delayed stubble tillage by a rotary tiller, primary tillage with plough or cultivator, or zero tillage. Over the following year, the fate of the seeds was determined. Immediate stubble tillage with following cultivator or plough resulted in 586 resp. 246 seeds m⁻² in the soil seed bank. After delayed stubble tillage with following plough, 76 seeds m⁻² were found, and no soil seed bank was built up in the zero tillage treatment. Nevertheless, in the zero tillage treatment, several robust volunteer plants survived the herbicide application before the direct drilling in autumn until following spring. In the zero tillage treatment and in the cultivator treatment, 0.19 volunteers m⁻² resp. 0.06 volunteers m⁻² flowered simultaneously to ordinarily sown oilseed rape in the following crop of winter wheat and produced 73 resp. 18 seeds m⁻². Delayed stubble tillage reduced the risk of gene escape via the soil seed bank, while zero tillage resulted in the highest risk of gene escape by pollen and by production of a new generation of seeds. In terms of a labelling threshold for gm food this number of seeds would be below the threshold of 0.9% of transgenic parts in conventially bred food or feed.     

Stickstoffdüngung und chemischer Pflanzenschutz in einem Dauerfeldversuch und die Ertragsgesetze von Liebig, L.iebscher, WOLLNY und MITSCHERLICH

Nitrogen fertilization and chemical plant protection in a long-term field experiment and the yield response laws of L iebig , L iebscher , W ollny and M itscherlich
An interpretation of L iebig 's "law of the minimum", L iebscher 's and W ollny 's "law of the optimum" and M itscherlich 's "law of constant activity" for two growth factors is presented. With three-quadrant diagrams (crop yield vs. N fertilization, crop yield vs. N uptake, N uptake vs. N fertilization) a long-term field experiment in Göttingen (Ackerbau-Systemversuch) is analyzed. This experiment started 1981 with the following treatments: 1. crop rotation (a: short rotation, sugar-beet, winter-wheat, winter-barley/vetch-green-manure; b: long rotation, sugar-beet, winter-wheat, winter-barley, lucerne, maize, faba beans); 2. chemical plant protection (a: with; b: without); 3. mineral nitrogen fertilization procedure (a: N-fixed, cumulative effects; b: N-rotating, one year's effects of different N fertilization); 4. mineral nitrogen fertilization (a: nil; b: suboptimal; c: optimal; d: hyper-optimal doses).
Without chemical plant protection resource use efficiency of applied nitrogen decreased according to L iebscher 's and W ollny 's "law of the optimum". In most cases this "law of the optimum" was applicable to the empirical data. L iebig 's "law of the minimum" and M itscherlich 's "law of constant activity" are exceptional cases, whereas L iebscher 's and W ollny 's "law of the optimum" has more general validity. For maximal resource use efficiency the growth factors have to be combined in optimal amounts.     

Auswirkungen von Weiden (Salix spp.) und Pappeln (Populus spp.) im Kurzumtrieb auf die biologische Vielfalt am Beispiel von Laufk?fern (Carabidae)

The increasing cultivation of energy crops in the last few years may have an impact on changes in the environment, biodiversity and the landscape. Due to a longer rest of soil and reduced application of pesticides, perennial crops such as short rotation coppice (SRC) offer benefits that can have a positive effect on the biodiversity. However, to assess the overall impact of SRC on biodiversity, information on the quality of SRC as a habitat for animals and plants, depending on the woody species over several years and the management is required. In the years 2010 and 2011, the diversity of ground beetles of willow and poplar in SRC were examined using pitfall traps at three sites in southwestern Germany. It was distinguished between species, variety and age of the SRC. At all sites ground beetle diversity was significantly higher in the studied poplar stands than in those of the willows. In addition, significant differences between the varieties could be observed depending on the location and the year of examination. The older stands of the SRC showed in general a higher level of diversity. Due to the different variety preference of ground beetles it is recommended to plant a mixture of varieties. Furthermore, SRC of different ages should be established side by side, as with increasing tree age species of the open area decrease and forest species settle. Overall, SRC offer the potential to increase biodiversity in natural landscapes.     

Sprouting Ability and Seasonal Changes of Sugar Concentrations in Rhizomes of Calystegia sepium and Roots of Convolvulus arvensis

Journal of Plant Diseases and Protection - Factors influencing the sprouting ability of rhizome pieces of Calystegia sepium and root pieces of Convolvulus arvensis were analyzed in four...     

Effect of tillage intensity on weed infestation in organic farming

Conservation tillage is not yet widely accepted by organic farmers because inversion tillage is considered to be necessary for weed control. Three long-term experiments were established with combinations of reduced and conventional plough tillage and stubble tillage to determine weed infestation levels in organic farming, i.e. herbicide application being excluded. Experiment 1 (with very low stocking density of perennial weeds) showed that in presence of primary tillage by mouldboard ploughing the number of annual weeds was nearly unaffected by the mode of stubble tillage. In experiment 2, however, with Canada thistle (Cirsium arvense) being artificially established, thistle density was significantly affected by stubble tillage and by a perennial grass–clover forage crop. Experiment 3 combined two levels of stubble tillage (skimmer plough, no stubble tillage = control) with four implements of primary tillage in the order of decreasing operation depth (deep mouldboard plough, double-layer plough, shallow mouldboard plough or chisel plough). Primary tillage by chisel plough resulted in significantly highest annual weed density compared to all other treatments. The natural C. arvense infestation in experiment 3 showed highest shoot density in the “skimmer plough/chisel plough” treatment compared to the lowest infestation in the “skimmer plough/double-layer plough” treatment. The poor capacity of the chisel plough for weed control was also reflected by the soil seed bank (5500 m⁻² C. arvense seeds for chisel plough, <300 seeds for all other primary tillage). A reduced operation depth of the mouldboard plough (“shallow mouldboard plough”) seemed to have an insufficient effect in controlling C. arvense infestation as well. Stubble tillage by the skimmer plough in addition to nearly any primary tillage operation largely reduced both annual weeds and thistle shoots. Most effective in controlling C. arvense was also a biennial grass–clover mixture as part of the crop rotation.Double-layer ploughing is a compromise between soil inversion and soil loosening/cutting and can be regarded as a step towards conservation tillage. In terms of controlling annual weeds and C. arvense, the double-layer plough was not inferior to a deep mouldboard plough and seems to be suitable for weed control in organic farming. Tilling the stubble shallowly after harvest can support weed control in organic farming remarkably, particularly in reducing C. arvense. If no noxious, perennial weeds occur and primary tillage is done by soil inversion, an omission of stubble tillage can be taken into consideration.     

Natural variation and morpho-physiological traits associated with water-soluble carbohydrate concentration in wheat under different nitrogen levels

Stem water-soluble carbohydrates (WSCs) are important plant traits influencing grain yields in wheat. However, the traits regulating WSCs storage, particularly under different nitrogen (N) levels are poorly addressed. This study investigated 35 morpho-physiological traits associated with the variation in WSC concentration (WSCc) in the main stem of eight wheat genotypes including two primitive genotypes under three N levels (0, 100, and 200 kg N ha⁻¹). 28 traits were significantly, positively or negatively, correlated with the WSCc in all N levels, and 22 of them were consistent across N levels. Majority of the traits were positively correlated with WSCc suggesting that multiple traits regulate WSCc in wheat plants. However, few traits such as root:shoot ratio (RS_R), stem nitrogen (S_N), leaf nitrogen (L_N), nitrogen per unit leaf area (N_LA), total vegetative mass (V_MASS), cellulose (C_L), and hemicellulose (H_C), were negatively correlated with WSCc. This suggests that plant N concentration was an important selective force driving WSCc in wheat. Indeed, a percent increase in leaf N concentration resulted in 28% lower WSCc. Direct selection estimated that higher V_MASS, flag-leaf width (FL_W), but lower RS_R was adaptive and resulted in higher WSCc in low N level. In contrast, lower V_MASS and FL_W were adaptive and resulted in higher WSCc in high N level. Higher cellulose and hemicellulose were associated with lower WSCc suggesting that a reduced carbon flux to stem structural compounds may improve WSCc in wheat plants. Together, these results demonstrate that a specific suit of trait changes that evolve under N-specific selection increase main stem WSCc but the adaptive value of these changes varies among traits and N levels.     

优化灌溉与施肥对冬小麦冠层结构的影响研究

试验研究优化灌溉与施肥对冬小麦冠层结构的影响结果表明,与限量灌溉处理相比,优化灌溉和传统灌溉处理小麦最上部3个节间明显伸长,导致株高增高10cm,旗叶叶面积减小7%,但倒2叶和倒3叶叶面积分别增加7%和20%;优化灌溉处理小麦旗叶茎叶夹角明显减小。与未施N肥处理相比,施用N肥有增大小麦株高、叶面积和茎叶夹角的趋势,且传统施N比优化施N更加明显。优化水N管理麦田各层次透光率与传统处理差异较小,但它们均显著低于限量灌溉和未施N处理。     

Einfluß langjähriger Winterweizen-Monokultur auf Ertragsbildung, Krankheitsbefall und Nematodenbesatz im Vergleich zum Winterweizenanbau in der Fruchtfolge

Influence of winter wheat grown continuously on grain yield, foot rot infection and nematodes compared with winter wheat in rotation
The field trial, started in 1968 at the experimental-station in Rauischholzhausen, was intended to give informations about winter wheat in continuous cultivation. The question was if intensification of growing culture enables monoculture wheat to yield as high as winter wheat in rotation (sugar-beet, winter wheat, spring barley). Influence of green manuring with additional nitrogen, straw manuring with additional nitrogen, straw burning and fungicid treatment against eyespot was investigated.
The following results have been obtained in the years 1969 to 1985:
1. In the 17 years average winter wheat in rotation yielded with 50.1 dt/ha a higher amount of grain dry weight than wheat in monoculture (43.6 dt/ha). Only in 3 years wheat in monoculture reaches the grain yield level of wheat in rotation.
2. The incidence of Pseudocercosporella herpotrichoides was in wheat after wheat about 10% higher than in wheat after sugar-beets.
3. The use of fungicides against culm base diseases caused in monoculture an increase in yield of about 2.7 dt/ha which was not higher than in rotation (+2.5 dt/ha).
4. The first 12 years indicated a decline-effect with continuously decreasing differences in the yield of wheat in monoculture compared with rotation. But until the 17th year of the trial grain yield differences were as high as in the beginning.
It is not possible either by means of intensification of fertilizing or chemical plant protection treatment to reach the grain yield level of winter wheat in rotation with winter wheat in monoculture. Even the use of modern agronomical methodes remains crop rotation as a central part of an effective plant culture.     

优化灌溉与施肥对冬小麦冠层结构的影响研究

盆栽试验研究连作对茄子苗期生长的影响结果表明 ,生长初期 4 5d内重茬茄苗株高、叶面积、主根长和总根长明显低于正茬 ,导致茄苗地上部、地下部鲜物质量分别比正茬减少 33 2 %和 30 2 % ,且重茬茄苗随苗龄的增加其根结线虫危害加重。对重茬土壤消毒虽消除线虫的危害 ,但未完全改善重茬茄苗生长状况 ,且播种后 7d重茬土壤茄子出苗率比正茬低 15 % ,表明茄子连作障碍是土传病虫害和化感物质共同作用的结果。通过水培收集的根系分泌物 ,随添加量的增加而对茄子胚根、胚芽生长的抑制作用增强 ,表明化感作用是茄子连作障碍的重要因子之一。     

优化灌溉和施肥对冬小麦产量的影响

为了探讨传统水氮管理和优化水氮管理对冬小麦产量的影响，于1999～2000年在中国农业大学中德合作项目北京试验基地进行了包括灌溉、氮肥和秸秆3因素共18个处理组合的田间试验。传统水氮管理尽量模仿当地农民的生产实际，优化水氮管理以冬小麦生长发育的需要为原则，结合土壤水分和土壤养分的实测值来具体确定。结果表明，优化灌溉在节水11mm的情况下，小麦产量与传统灌溉无显著性差异；优化施氮与传统施氮相比，氮肥用量降低了75％，但产量并不降低；秸秆还田与秸秆不还田相比，冬小麦产量无明显变化。上述结果表明，在保持产量不降低的前提下，华北平原小麦生产中节水的空间相对较小，而节肥(指氮肥)的空间相对较大，优化施氮管理值得大力推广。