放牧因子与VA菌根的相互作用对鸭茅养分吸收和生长发育的影响

探讨了放牧因子与VA菌根的相互作用对鸭茅(Dactylis glomerataL.)养分吸收和生长发育的影响。菌根效应表现在不施磷肥条件下的鸭茅地上部生育与地上、地下部的磷素营养上,但对地上部生育的效应因刈割次数的增加而降低,对地上、地下部磷素营养的效应因土壤镇压而降低。菌根对鸭茅钙素营养的效应只见于不施磷肥条件下的土壤镇压处理,而在相同条件下菌根却降低了鸭茅的镁含量。说明VA菌根对鸭茅磷素营养和生长发育的效应与土壤磷营养有关,而且因地上部的过度采食和土壤镇压而降低。     

Can the occurrence of Senecio jacobaea be influenced by management practice?

Senecio jacobaea is a poisonous weed in grasslands of various countries (e.g. Great Britain, New Zealand, Central European states) and the further spread of the species into farmland must be prevented. To assess the influence of management practice and site conditions on the occurrence of S. jacobaea, we conducted a survey in the northern and central part of Switzerland. Botanical assessments were carried out on grassland plots with S. jacobaea occurrence and on neighbour plots without S. jacobaea. For these plots, we analysed the soil nutrients and the details of management practice, such as type and intensity of management and fertiliser application. The most important factors influencing the occurrence of S. jacobaea were related to management: There was a high risk for the occurrence of the species on parcels with low nitrogen fertilisation, continuous‐extensive grazing (set stocking) and a very open sward. Senecio jacobaea was not present in intensively managed meadows cut more than twice per year. As an exception, with a high propagule pressure from the vicinity, S. jacobaea was also found in intensively grazed pastures and in meadows of moderate management intensity (two cuts). We conclude that long‐term control of S. jacobaea can best be achieved by avoiding sward damage and by preventing the species’ seed formation in the pasture and local vicinity.     

高山草原绵羊放牧生态及消化代谢的研究：Ⅰ放牧绵羊嗜食性研究

利用植物显微技术镜检法和食道瘘管法对放牧绵羊采食的高山草原植物成分与嗜食性指数进行分析。结果表明，绵羊在黄草期采食植物成分比青草期多，其嗜食性指数在不同时期变幅较大，随着冬季来临，绵羊对草地植物的嗜食性不如青草期强烈，至某些植物嗜食性是相对稳定的。     

Vegetation,Wildlife, and Livestock Responses to Planned Grazing Management in an African Pastoral Landscape

Rangelands are vital for wildlife conservation and socio‐economic well‐being, but many face widespread degradation because in part of poor grazing management practices. Planned grazing management, typically involving time‐controlled rotational livestock grazing, is widely touted as a tool for promoting sustainable rangelands. However, real‐world assessments of its efficacy have been lacking in communal pastoral landscapes globally, and especially in Africa. We performed landscape‐scale assessment of the effects of planned grazing on selected vegetation, wildlife, and cattle attributes across wide‐ranging communally managed pastoral rangelands in northern Kenya. We found that planned grazing enhanced vegetation condition through a 17% increase in normalized difference vegetation index, 45–234% increases in herbaceous vegetation foliar cover, species richness and diversity, and a 70% reduction in plant basal gap. In addition, planned grazing increased the presence (44%) and species richness (53%) of wild ungulates and improved cattle weight gain (>71%) during dry periods when cattle were in relatively poor condition. These changes occurred relatively rapidly (within 5 years) and despite grazing incursion incidents and higher livestock stocking rates in planned grazing areas. These results demonstrate, for the first time in Africa, the positive effects of planned grazing implementation in communal pastoral rangelands. These improvements can have broad implications for biodiversity conservation and pastoral livelihoods. Copyright © 2017 John Wiley & Sons, Ltd.     

人工草地绵羊系统优化研究Ⅳ人工草地划区轮牧罗姆尼怀孕母羊群体采食量研究

人工草地划区轮牧条件下,牧草生长旺季罗姆尼(Romney)怀孕母羊羊群采食量与怀孕日龄间呈显著正相关,回归方程Y=0.003 2X+0.853 7,r=0.949 5;但霜冻到来后采食量与怀孕日龄间呈显著负相关,回归方程Y=-0.007 3X+1.784 1,r=-0.985 1.     

Soil physical fertility, soil structure and rooting conditions after ploughing organically managed grass/clover swards

Effective management of soil structure and organic matter are essential in organic cropping to ensure good rooting conditions and to optimize the production of mineralized N and thus minimize greenhouse gas emissions. We investigated how mid‐winter or early spring ploughing and three grazing duration treatments prior to ploughing influenced soil structure, soil organic matter and plant root growth under the first spring barley crop after a grass–clover ley. The experiment was carried out over two seasons. We also studied the soil under first‐year oats in a long‐term rotations experiment where 2 or 3 years of arable crops followed 3 or 4 years of grass. Pore size distribution and pore continuity, bulk density, particulate (light fraction) organic matter, readily oxidizable organic matter (ROM), aggregate size distribution and root length densities were measured. Macroporosity appeared to be the best indicator of soil physical fertility; it was sensitive to changes in soil structure arising from compaction and root growth. This, along with visual examination, revealed the loosening resulting from ploughing. The generally favourable macroporosity amongst small, stable aggregates reduced the likelihood of development of anaerobism. Macroporosity and aggregate size can be estimated from visual examination of the soil, a method that offers the advantage of being quick and of sampling a large volume. The content of ROM was high 6.1–6.4 g 100 g^?1 whole soil. However, particulates formed only a small fraction (6–9%) of the ROM. Despite the favourable ROM and structure, the soil was susceptible to compaction damage during seedbed preparation in wet soil after ploughing which reduced grain yield in some plots. Grazing by sheep before ploughing and date of ploughing had minor effects on soil quality. Grazing for 2 months prior to ploughing increased root length density in the upper topsoil in the following arable crop, possibly because of the higher quality of the animal and grass–clover residues. Conservation of soil quality was related more to secondary tillage and sowing operations after ploughing than to duration and timing of grazing.     

广西草食动物现状及发展潜力

从广西草食动物存栏量大、优良品种多、农作物秸杆和牧草资源丰富的实际出发，提出充分利用这些资源优势，加快我区草食动物发展步伐的建议和策略。     

不同载牧量对苜蓿放牧地植被的影响

研究于１９９２年在甘肃河西半荒漠地区杂花苜蓿型人工草地进行，试验采用单因子设计，衣载牧量分轻牧、中牧、重牧３个处理６个重分区轮牧。结果表明，试验当年，草地类型未发生演变，披碱草随放牧加强而衰退，无芒雀麦和红豆草在中牧下得到促进，紫羊茅在重牧下受抑。由牧草产量和质量的分析表明，在西北干旱地区，苜蓿型草地可于６月初刈草后，连续放牧３次，且载牧量以中等为宜。     

Phosphorus losses in surface run-off from grazed permanent pastures on a volcanic soil from Chile

Reactive (RP) and organic phosphorus (OP) losses from grazed paddocks were determined on a volcanic soil during 2004 and 2005. Paddocks were grazed by Holstein Friesian steers (3.5 steers ha^?1) and received N (67.5 kg ha^?1) and P fertilizer (30 kg P ha^?1). Total losses ranged between 4 and 15 g P ha^?1 year^?1 and were greatly affected by incidental P losses associated with spring P fertilizer application. Reactive P constituted 90% of the total losses on average. Due to the high water infiltration capacity of the soil, run‐off was <1% of total drainage, therefore, phosphorus losses in run‐off were small.     

Contribution of White Clover Varieties in High-Productivity Systems under Grazing and Cutting

Two medium leaf size varieties of white clover (Trifolium repens L.) were grown in mixture with a range of grass species and varieties in a field experiment conducted over 4 years. The clovers were grown singly or as a blend in swards with a tetraploid perennial ryegrass (Lolium perenne L.), a diploid Italian ryegrass (Lolium multiflorum L.) or tetraploid hybrids between these two species (Lolium x boucheanum Kunth). These grasses were also grown in monoculture. Swards were managed in a regime involving two periods of sheep grazing, two periods of cattle grazing and a silage cut in the same year for 4 years. The objectives of this experiment were 3‐fold: (1) to examine the yield and persistency of white clover in highly productive systems with modern perennial, hybrid and Italian ryegrasses; (2) to compare the performance of white clover varieties grown singly in mixture with grasses with their performance together as a blend, and (3) to examine the persistency of new Italian ryegrass varieties, exemplified by AberComo. The clover content of the sward remained high throughout the experiment, with a mean of 31 % overall. Differences in clover yield between plots were largely attributable to the effects of companion grasses. Total yields were very similar in plots containing different clover varieties and in plots where these varieties had been grown singly or as a blend. Grass yields in mixture were greater than those in monoculture but showed similar relative rankings. The diploid Italian ryegrass variety AberComo showed an unexpectedly high yield in the 4th year of the experiment. The implications of these results for strategies for productive, sustainable agriculture using modern white clover and ryegrass varieties are discussed.