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1.
绿僵菌防治草原蝗虫效果显著,其在草原田间的存活能力影响其持续控害效果。除了侵染昆虫,绿僵菌还具有在植物根际宿存和根内生的生活方式,但相关宿存规律和内生性的研究报道很少。本文研究了绿僵菌在内蒙古草原两种优势种植物羊草和克氏针茅根际的种群数量变化并对其在这两种草的根内宿存进行了鉴定。结果表明,在干旱的内蒙古草原,绿僵菌施用后种群数量在30 d内快速下降,但能够以低密度在羊草、克氏针茅根际土壤中至少延续宿存75 d,羊草根际环境比较利于绿僵菌生存。对菌株egfp基因标记的特异PCR检测证明了绿僵菌在羊草和克氏针茅根内宿存。试验数据为指导植保生物防治中充分利用绿僵菌的昆虫病原性和植物内生特性提供理论基础,也将成为绿僵菌物种生活方式多样性、与植物互作及共进化研究的重要基础。  相似文献   
2.
Two short-term grazing experiments were conducted with Norwegian Red cows. In Exp 1, 24 cows were randomly assigned to one of the following three pasture allocation methods (PAM): weekly pasture allowance (7RG), grazing 1/7 of 7RG each day (1SG), or grazing as 1SG but had access to grazed part of the paddock within one week (1FG). In Exp 2, 7RG was shortened to 5 days (5RG). We hypothesized that PAM will affect sward quality, quantity, intake and production differently. Pasture chemical composition changed with advancing grazing days but were not different between treatments. Pasture intake, milk yield, and methane emission were not affected by PAM. In Exp 1, 7RG cows spent less time on grazing, whereas in Exp 2, 1FG cows spent longer on grazing than others. Patterns observed in sward quality, and behavioural and physiological adaptations of cows to short-term changes in nutrient supply may explain the observed effects.  相似文献   
3.
Rotational stocking theoretically enables regrazing of regrowth, but regrowth may be limited in xerophytic vegetation. We tested the hypothesis that regrowth would be slow and fixed in Hesperostipa comata (a caespitose, drought‐tolerant grass), while growth would be flexible in Pascopyrum smithii (a rhizomatous, less drought‐tolerant grass) under increasing defoliation and moisture, by assessing tiller growth rates, population dynamics and plant yield on marked plants in a Dry Mixed Grass prairie. Plots were clipped in late summer to simulate a deferred control, or intermittently during the growing season (May–August) at high intensity–low frequency (HILF), low intensity–high frequency (LIHF) or high intensity–high frequency and crossed with two water treatments (ambient and addition) in both a xeric upland and a mesic lowland. Growing season defoliation increased tiller growth rates of P. smithii in the upland, whereas HILF and LIHF reduced growth in the lowland. All defoliation regimes increased tiller growth for H. comata. Tiller populations of H. comata increased with frequent defoliation, while tiller populations of P. smithii decreased regardless of defoliation regime. Frequent defoliation, regardless of intensity, reduced yield relative to the deferred control for both grasses. While water addition consistently increased growth rates and reduced differences in tiller number among defoliation treatments, the regrowth of both grasses remained similar under varied defoliation with ambient moisture. High moisture conditions also promoted regrowth more in P. smithii compared to H. comata. In summary, neither grass species displayed an inherently fixed or flexible tiller or plant yield response in response to defoliation or moisture.  相似文献   
4.
The assessment of rangeland productivity in semi-extensively grazed arid rangelands is a prerequisite for livestock management in relation to sustainable use of pastoral resources. The objective of this study was to assess rangeland productivity based on normalised difference vegetation index (NDVI) images. Data on phytomass were measured on 61 field samples in arid rangelands of Morocco, covering various rangeland categories during autumn (November) and spring (April), i.e. when phytomass is at low and high levels, respectively, for two consecutive years (2008 and 2009). Dekadal EROS Moderate Resolution Imaging Spectroradiometer (eMODIS) NDVI data were linearly regressed to field measurements for these four periods. Results show that phytomass values were correlated with NDVI during spring, with R2 and RMSE values of 0.82 and 0.3 t ha?1, respectively. This study indicates there is a high potential for operational use of remotely sensed data to estimate rangeland phytomass of semi-extensively grazed rangelands.  相似文献   
5.

近红外光谱技术(NIRS)是近几十年迅速发展的测试分析技术,由于准确、高效、无损等检测优势,在牧草营养价值评价领域得到广泛应用,但是在天然草地牧草方面应用较少。快速、实时评价天然草地牧草营养价值,为研究天然草地营养供给和营养载畜量提供基础数据,对草地畜牧业生产具有重要意义。文章阐述了近红外光谱技术的基本原理和特点,介绍了直接法和间接法评价牧草营养价值,分别从常规营养成分、矿物元素、抗营养成分、营养物质消化率4个层次综述近红外光谱技术在2个方法中的应用,并做出展望,以期建立基于NIRS技术的天然草地牧草营养价值数据库,为天然草地的科学管理和合理利用发挥重要作用。

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Our hypothesis suggests an improvement in carcass and meat quality of pasture‐finished animals by introducing concentrate feed into diets. This study aimed to evaluate the effect of different levels of protein‐energy supplementation on carcass and meat characteristics of Texel lambs raised on Brachiaria pastures, and compare the results with those obtained from confined animals. Thirty 2‐month‐old intact lambs were divided into five treatments: pasture with mineral supplementation, pasture containing daily supplies of 0.8, 1.6, and 2.4% BW protein‐energy supplementation, and confinement (reference treatment). All animals were slaughtered 104 days after the beginning of the experiment. Lambs submitted to 1.6% and 2.4% BW supplementation presented similar characteristics to animals kept in confinement and were superior to animals treated with 0 or 0.8% of BW supplementation levels (p < .05). Increases of subcutaneous fat thickness were verified for 0.0, 0.8, 1.6, 2.4% BW, and confinement treatments, being respectively of 0.25, 0.74, 1.61, 1.69, and 1.98. Conversely, treatments had no influence on meat physical‐chemical characteristics, being all considered moderately soft, juicy (tender), and with mild tastes and odors. Lambs raised on Brachiaria pastures have high‐quality meat, but more protein‐energy supplementation is needed to be an alternative for the feedlots for young animals.  相似文献   
8.
杨庆  王义祥  李欣欣  翁伯琦  廖红 《草地学报》2020,28(6):1519-1526
为提高豆科决明属(Chamaecrista spp.)牧草的结瘤能力和固氮效率,促进决明属牧草在酸性土壤中的应用及推广,本研究以圆叶决明(Chamaecrista rotundifolia)和羽叶决明(Chamaecrasta nictitans)为试验材料,通过分离、纯化、nodA基因鉴定等方法,从酸性土壤里决明属牧草的根瘤中分离到10株候选根瘤菌株系。16S rDNA测序及系统发育树分析表明,这10株根瘤菌均属于慢生型根瘤菌。回接试验表明,上述10株根瘤菌均能与圆叶决明共生,形成根瘤。与不接种的对照相比,其固氮酶活性为0.08~4.65 μmol·g-1·h-1,植株干重、SPAD值和氮含量分别提高了99.17%~372.14%,399.27%~789.05%,235.00%~1043.33%。其中,4株根瘤菌TXR2,TXN1,WYSR1,JYN6对圆叶决明氮营养贡献最大,并且TXN1与宿主共生形成的根瘤数目最多,而JYN6的固氮酶活性最高。说明本研究分离鉴定到4株决明高效根瘤菌,具有较好的应用前景。  相似文献   
9.
What occurs when virus infection is spreading within a mixed plant species population? This question is important not only for economically significant, mixed species managed systems but also for environmentally significant mixed wild species populations. It received attention in recently published ecological studies on wild plant species, but these, and recent general pasture research publications, rarely mention earlier virus studies involving mixed species managed pasture. This review seeks to rectify that situation. It describes 10 diverse examples of past research on mixed species managed pasture done over two decades on three continents that demonstrated plant species balance changes arising from virus infection. These examples showed that plants belonging to susceptible pasture cultivars sensitive to systemic virus infection are sufficiently weakened that their ability to withstand competition from nonhost plants of other pasture species, or weed species, was diminished sufficiently to alter the plant species balance. Also, a similar alteration occurred when they were competing with virus-resistant or virus-tolerant host plants of the same or other pasture species, or a virus-resistant weed species. Such competition also diminished seed production, which decreased their ability to regenerate. Notably, as reported subsequently with wild plant species populations, when two different pasture species infected by the same virus compete with each other, growth of the more sensitive species is suppressed. Because managed mixed species pastures constitute an important component of regenerative agriculture, retaining an optimal balance of pasture species and delaying pasture decline from weed invasion both require effective management of virus diseases.  相似文献   
10.
The patterns and extent of hard seed breakdown of dormant seeds and pods following burial in the soil in February (summer) varied for up to 19 accessions of 12 species of annual forage legumes. The experiments, at six sites across southern Australia, were designed to identify legumes whose patterns of hard seed breakdown would suit them to agronomic evaluation in a summer sowing research program. For a subset of accessions, sufficient hard seed breakdown was demonstrated between February and April to allow a high proportion of seed to germinate in late autumn—a desirable pattern for summer sowing. Although there was a large G x E interaction, some cultivars of Ornithopus sativus Brot., O. compressus L. and Trifolium spumosum L. had a pattern that was reproducible at all sites. The experiments also identified accessions of Biserrula pelecinus L. and T. glanduliferum Boiss., which had the desirable pattern in regions of south‐eastern Australia, but not Western Australia. A pragmatic approach for selection of forage legume accessions in situ for evaluation within a summer sowing program was demonstrated.  相似文献   
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