红车轴草异黄酮对肉鸡免疫器官、免疫球蛋白及抗氧化性能的影响

通过在饲料中添加红车轴草(Trifolium pretense L.)异黄酮,研究其对AA肉鸡免疫器官、免疫球蛋白及抗氧化性能的影响。选用180羽1日龄AA肉仔鸡分成3组,即对照组、处理Ⅰ组、处理Ⅱ组,分别饲喂基础日粮、基础日粮+红车轴草异黄酮(10 mg·kg^-1)、基础日粮+红车轴草异黄酮(20 mg·kg^-1)。结果表明:处理组的肉鸡日增重和免疫器官指数均高于对照组,饲喂21 d后,处理组血清IgM的含量显著高于对照组(P<0.05),49 d后,处理Ⅰ组肉鸡血清IgG含量显著高于对照组(P<0.05);红车轴草异黄酮提高了血清中谷胱甘肽过氧化物酶(GSH-PX)活性,降低了丙二醛(MDA)含量,处理Ⅰ组和处理Ⅱ组之间差异不显著。红车轴草异黄酮能够明显改善肉鸡生产性能、调节免疫和提高机体的抗氧化性。     

秦巴山区白三叶引种栽培试验

秦巴山区白三叶引种试验结果表明，春播白三叶出苗快，长势良好，开花期鲜草的平均产量为9000kg/hm^2，茎叶比6．25：1，开花期白三叶的粗蛋白质和粗纤维含量分别为17．3％和14．8％，认为白三叶营养价值高，耐热，抗旱能力强，越夏性能好，是值得在秦巴山区推广的优点豆科牧草品种之一。     

Interaction Effects of Nitrogen and Phosphorus on Nodulation in Red Clover (Trifolium pratense L.)

Red clover (Trifolium pratense L.) is one of the most important plants in forage production, especially in northern areas. Fertilisation practices are focused on high yield and forage quality but effects of nutrients on nodulation and N₂ fixation are poorly understood. The aim of this work was to study how nitrogen (N) and phosphorus (P) separately as well as in combination affected nodulation. Red clover plants were grown in pots with gravel in a greenhouse for 11 weeks. To resemble field conditions the root temperature was kept lower than the shoot temperature. Plants were given five different combinations of N and P concentrations during growth. The result showed that at high N concentrations P had a counteracting effect on the N inhibition. The N₂-fixation parameters, nodule number, nodule dry matter and specific nitrogenase activity, were six times higher in plants grown with high N and high P than in plants with high N and low P. When the N₂-fixation parameters and the dry matter of roots and shoots were related to total plant dry matter, there was a stronger effect of P on nodulation parameters than on roots and shoots. This indicates that P has a direct effect on the N₂-fixation parameters, rather than an indirect effect via increased plant growth. These results demonstrate the importance to studying the effects of more than one nutrient at a time.     

Emissions of N2O and CO2, denitrification measurements and soil properties in red clover and ryegrass stands

The relationships between the fluxes of nitrous oxide (N₂O) and carbon dioxide (CO₂), and their concentrations in the soil air, three different measures of potential denitrification, soil moisture, soil temperature and precipitation were investigated in soils from beneath ryegrass (Lolium multiflorum Lam.), red clover (Trifolium pratense L.) and mixture of ryegrass-red clover stands on a gleic cambisol. Investigations were carried out in order to test the hypothesis that the measure(s) of potential denitrification are good predictor(s) of N₂O fluxes and thus may be used in empirical models of N₂O emission. Potential denitrification characteristics used in this study involved (i) short-term denitrifying enzyme activity (DEA), (ii) long-term denitrification potential (DP), both determined in soils amended with nitrate and glucose, and (iii) denitrification rate (DR) measured using intact soil cores. Flux measurements were made using cylindrical chambers (internal diameter 31 cm, volume 0.015 m³). The fluxes of N₂O and CO₂ and many other characteristics showed large spatial and temporal variability. Emissions of N₂O from the grass plots were closely related to N₂O concentrations in the soil atmosphere at 22.5 cm depth. Most soil properties did not correlate with N₂O fluxes. It was concluded that DP was not a good predictor for N₂O flux. DEA did not show significant relationship with N₂O flux, but it is suggested that if determined in representative, large soil samples, DEA could be a predictor of N₂O fluxes; this assumption needs, however, verification. The only potential denitrification characteristic which was significantly related to N₂O emission both in grass and clover treatments was DR, which was determined in soil cores.     

Influence of pasture botanical composition and fertilization treatments on tree growth

Silvopastoral systems, which combine tree and pasture production, are more complex ecosystems than exclusively agronomic systems. Good silvopasture management should seek to increase positive interactions (or synergies) and reduce negative interactions among system components (soil, trees, grass and cattle) to increase global system productivity. Tree growth and pasture production within such systems can be optimized through appropriate species selection and fertilization. The aim of the present study, carried out over the course of 3 years, was to compare how traditional fertilisation, sewage sludge dose, and potassium affect pasture-tree competition, botanic composition and tree growth in a silvopastoral system located on agricultural land during the early years of system development. The addition of potassium is recommended for improving tree growth in silvopastoral systems with slightly acidic soil, especially if the pasture has high legume content. White clover is a good choice of species for silvopastoral systems because it promotes tree growth. Our study revealed that pasture production improved when sewage sludge was used as a fertiliser, but annual production was still more strongly dependent on weather conditions.     

亚热带黑麦草／三叶草草地牧草与群落中几种元素季节动态及分布

探明了不同季节，供试草种及群落中Ca、K、Mg、Mn、Fe和Na元素的含量、积累和群落中的分布规律，为了解草地的营养状况和元素的输出输入与平衡提供了基础。     

苜蓿多糖提取中适宜品种及工艺的研究

苜蓿含有具有生物活性的食用多糖,本实验对在黑龙江省主栽和试栽的国内外16个苜蓿品种的多糖含量进行了测定比较.对其提取工艺进行研究,利用热水浸提、醇沉等方法可得到粗多糖,采用木瓜蛋白酶和三氯乙酸进一步处理,结果表明浸提3次、木瓜蛋白酶添加0.05％、三氯乙酸终浓度达到6％为宜。     

Interactive effects of biochar and N-fixing companion plants on growth and physiology of Acer saccharinum

The use of biochar with N-fixing species has been shown to enhance productivity of agricultural systems, both in N-fixing crops, as well as in mixed-species systems. Here we investigate the potential for the use of a granulated mixed conifer biochar and a sugar maple biochar in combination with N-fixing companion plants in an urban forestry context. A factorial greenhouse experiment compared growth responses in silver maple (Acer saccharinum L.) saplings planted with two biochar types as soil amendments, alone and in combination with two N-fixing plant companions (Trifolium repens L. and Dalea purpurea Vent.). Both biochar types enhanced tree growth; however, a maple feedstock biochar resulted in greater increases than a granulated conifer-feedstock biochar. N-fixing companion species also increased tree growth, although the faster-growing Trifolium reduced soil moisture content and reduced sapling growth in the absence of biochar. The highest tree growth performance and total N uptake was obtained with a combination of both biochar and N-fixing plants, with a ~30 % increase in biomass compared to controls for the granulated conifer biochar, and a ~55 % increase for the maple biochar. We conclude that biochar additions in combination with N-fixing companion species have considerable promise in an urban forestry context, but that optimization of the system in terms of biochar type and species combination is an important consideration.     

AM菌对三叶草吸收、累积重金属的影响

采用4室根箱培养系统,探讨了Cu、Zn、Pb、Cd 4种重金属复合污染土壤中,丛枝菌根菌对三叶草生长及吸收、累积重金属的作用,结果表明:重金属Cu 100mg/kg、Zn 600mg/kg、Pb 300mg/kg、Cd 10mg/kg的复合污染对三叶草生物量影响较小,但土壤重金属处理使丛枝菌根菌Glomus intraradices和Glomus caledonium对三叶草的侵染率分别降低53%和56%,菌种G.intraradice的菌丝密度降低73%;接种菌根真菌能明显减少重金属复合污染土壤中三叶草对Cu、Cd和Pb的吸收,并强化根系在限制重金属Pb和Cd向地上部运输中的作用,地上部Pb和Cd含量分别下降24.2%~55.3%和65%~97.9%,使三叶草地上部Cd和Pb含量均低于我国牧草重金属安全含量,提高了三叶草可食部分的质量;不同菌根真菌对三叶草吸收、累积及分配重金属的影响有明显差异,Glomus intraradices对减少三叶草对重金属的吸收及其在地上部可食部分的累积的作用大于Glomus caledonium。丛枝菌根菌对于强化三叶草根系对重金属的固持作用,调节生态系统中重金属的生物循环,减轻重金属对食物链的污染风险方面起着重要作用。     

Numbers of clover rhizobia needed for crown nodulation and early growth of clover in soil

Low soil populations of Rhizobium leguminosarum biovar trifolii indicate a need for inoculating clovers (Trifolium sp.) at planting. The number of rhizobia in soil varies considerably from field to field and the number needed for nodulation on the upper taproot and for vigorous seedling development is not known. Two experiments were undertaken using arrowleaf clover (T. vesiculosum Savi) and crimson clover (T. incarnatum L.) grown in pots filled with soil. Two soils were used; one contained 10 indigenous rhizobia g^-1 and the other contained fewer than three. The treatments consisted of amending each soil with two strains of inoculant rhizobia to contain from 10 to approximately 1×10⁶ rhizobia g^-1 followed by planting to clover. The number of nodules near the top of the root increased as the number of rhizobia in the soil increased to the highest inoculum level. A low number (approximately 1×10³ to 1×10⁴) of rhizobia was sufficient for maximal N content of seedlings. It seems that soil containing 100 or fewer rhizobia g^-1 may respond to inoculation with increased crown nodulation and seedling vigor.