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101.
This experiment quantified the effects of: (i) heading date of perennial ryegrass, (ii) grazing frequency in spring and (iii) date of silage harvest, on the ensilability of herbages harvested for silage, and on the conservation and estimated nutritive value of the resultant silages. Replicated field plots with two perennial ryegrass mixtures (intermediate‐ and late‐heading cultivars) were subjected to three spring‐grazing regimes (no grazing, grazing in late March and grazing in both late March and late April) and were harvested on four first‐cut harvest dates between 20 May and 21 June. Herbage from each of the four replicates of these 24 treatments was precision‐chopped and ensiled unwilted and with no additive in laboratory silos. Herbage from the sward with the intermediate‐heading cultivar had a higher (P < 0·001) dry‐matter (DM) content and buffering capacity than that from the late‐heading cultivar, whereas water‐soluble carbohydrate concentrations increased (P < 0·001) with more frequent grazing in spring. Later harvesting enhanced herbage ensilability through an increased (P < 0·001) DM content and reduced (P < 0·001) buffering capacity and pH. Fermentation profiles of the silage were not markedly influenced by the cultivar mixture used but grazing in both late March and late April resulted in a more extensive fermentation with the acids produced increasingly dominated by lactic acid. The concentrations of acetic acid, and to a lesser extent, ethanol declined as silage harvest date was delayed. Overall, the relative effects of grass cultivar mixture were smaller than those of spring‐grazing treatment or silage‐harvesting date although on any given harvest date the herbage from the intermediate‐heading cultivar mixture was easier to preserve as silage than herbage from the late‐heading cultivar mixture. Delaying the harvesting of the late‐heading swards by 8 d removed the differences related to growth stage in buffering capacity, pH and DM content. 相似文献
102.
103.
A field-study was undertaken in Hamilton, New Zealand to determine if there was an interaction between water-soluble carbohydrate (WSC) reserve content and defoliation severity on the regrowth of perennial ryegrass-dominant swards during winter. Perennial ryegrass plants with either low or high WSC content were obtained by varying the defoliation frequency. At the third defoliation at the one-leaf stage and at the first defoliation at the three-leaf stage (harvest H1 ), swards were mown with a rotary lawnmower to residual stubble heights of 20, 40 or 60 mm. All swards were then allowed to regrow to the three-leaf stage before again defoliating to their treatment residual stubble heights (H2 ). Frequently defoliated plants contained proportionately between 0·37 and 0·48 less WSC in the stubble after defoliation, depending on the severity of defoliation. There was no interaction between WSC content and defoliation severity for herbage regrowth between harvests H1 and H2 . Herbage regrowth was lower from swards containing low WSC plants compared with high WSC plants (2279 vs. 2007 kg DM ha−1 ). Furthermore, swards defoliated to 20 or 40 mm had greater herbage regrowth compared with those defoliated to 60 mm (2266, 2249 and 1914 kg DM ha−1 for swards defoliated to residual stubble heights of 20, 40 and 60 mm, respectively). Regrowth of perennial ryegrass was positively correlated with post-defoliation stubble WSC content within defoliation severity treatment, implying that WSC contributed to the defoliation frequency-derived difference in herbage yield. However, the effect of defoliation severity on herbage regrowth was not associated with post-defoliation stubble WSC content. 相似文献
104.
105.
Quantifying spatial variability in forage grass yield within individual fields is hampered by the lack of accurate yield monitoring equipment. Here, it is shown how dry matter (DM) yield of silage swards can be predicted on the basis of their mineral composition. This empirical method of predicting yield enables diagnoses of sward nutrient status to be made simultaneously from the tissue test information, and provides a unique opportunity for identifying the nutritional and non-nutritional factors responsible for variability in sward productivity at sub-field scales. Maps of sward DM yield at first, second and third cut silage stages in 1999, and at first cut silage stage in 2000, on a large (7.9 ha) grassland field were produced using two different yield models: one model for first cut and a separate model for second and third cuts. The maps indicated that DM production varied considerably across the field, particularly at first cut, but that the pattern of yield variability at this cut was consistent from 1999 to 2000. The results of the plant tissue tests suggested that N deficiency had been responsible for limiting DM production on the lower yielding parts of the field. 相似文献
106.
常年性变应性鼻炎手术疗法探讨 总被引:2,自引:0,他引:2
探索常年性变应性鼻炎的治疗新方法,方法选择各种非手术疗法不佳的常年性变应性鼻炎患者36例为手术组(6例伴有支气管哮喘),病程1.5-20a局麻下行双侧蝶腭,筛前神经电灼加下鼻甲部切除切;另选31例未行手术首作为对照组。结论蝶腭,筛前神经电灼加下鼻部分切除的新方法为治疗常年性变性鼻炎之有效的方法之一。 相似文献
107.
108.
F.R. McKenzie J.L. Jacobs P. Riffkin G. Kearney 《African Journal of Range and Forage Science》2013,30(1-2):1-6
Abstract Effects of nitrogen (N) (0, 15, 30, 45 and 60 kg N ha?1) applied at five different times during autumn and early winter on the N fixation of Trifolium repens L. (white clover) in Lolium perenne L. (perennial ryegrass) / white clover pastures were examined (Experiment 1). Effects of applying different N fertilisers (e.g. urea and ammonium nitrate) at 45 kg N ha?1 in autumn, with and without phosphorus (P), potassium (K) and sulphur (S) on N fixation were also tested (Experiment 2). In Experiment 1, percentage N derived from the atmosphere (percent Ndfa) by white clover varied between 87% and 91% in the period after (24 to 36 days) N application. Increasing rates of N and time of application did not influence percent Ndfa. The amount of N fixed by white clover ranged from 0.8 to 3.7 kg N ha?1 in the period after N application. Increasing rates of applied N produced a significant (P<0.05) linear increase in the amount of N fixed. In Experiment 2, percent Ndfa and amount of N fixed (1.9 to 4.1 kg N ha?1) were unaffected by different N fertilisers, with and without P, K and S, in the period after (37 days) fertiliser application. For both experiments, fertiliser N increased dry matter yield while having no effect on white clover composition. It is concluded that single applications of N during the autumn and early winter benefit pasture growth without adversely affecting white clover N fixation or clover composition. This finding, however, will require further investigation. 相似文献
109.
在江河源区2龄混播禾草草地(垂穗披碱草 星星草)上牦牛放牧试验结果表明: 随着放牧率的增加,在生长期内不同功能群地上净初级生产量和总地上初级生产量均出现了单峰曲线变化,即“S”型变化趋势; 总的地上净初级生产量和垂穗披碱草地上净初级生产量对放牧率的变化很敏感, 且随着放牧率的增加, 峰值出现日期提前; 其它禾草和星星草的峰值对放牧率的变化不很敏感;莎草类和杂草类对放牧率的变化比较敏感。随放牧率的增加, 地上现存量和总地上初级生产量的峰值下降, 且达到峰值的时间提前。在整个放牧期(植物生长期),重度放牧的RYT值均小于1,表明重度放牧使垂穗披碱草和星星草一直处于拮抗状态,其它各处理组在生长中后期也处于拮抗状态; 不同放牧率(包括对照)下垂穗披碱草的竞争力强于星星草, 垂穗披碱草因其高度和发达而较深的根系成为竞争的优胜者。 相似文献
110.
为筛选出适宜云南迪庆高寒地区种植的多年生牧草品种,本研究开展了12个多年生牧草品种引种适应性的比较,并采用灰色关联度综合评价法对其生产性能进行了综合评价。结果表明,12种牧草生产性能的高低顺序为紫花苜蓿牧歌401+Z(Medicago sativa cv.Amerigraze401+Z)菊苣将军(Cichorium intybus cv.Commander)鸭茅安巴(Dactylis glomerata cv.Anmba)多年生黑麦草雅晴(Lolium perenne cv.Yatsyn)白三叶铺地(Trifolium repens cv.Prop)红三叶(T.pratense)白三叶海法(T.repens cv.Haifa)紫花苜蓿游客(Medicago sativacv.Eureka)紫花苜蓿WL-525(Medicago sativacv.WL-525)扁穗雀麦草地麦特(Bromus catharticus cv.Grasslands Matua)紫花苜蓿猎人河(M.sativacv.Hunterriver)老芒麦同德(Elymus sibiricus cv.Tongde)。其中,牧歌401+Z紫花苜蓿、将军菊苣、安巴鸭茅、雅晴多年生黑麦草、铺地白三叶、普通红三叶、海法白三叶在当地适应性较好,生产性能相对较高,可作为当地建植栽培草地及改良天然草地的优选品种。研究结果对解决当地饲草匮乏、促进当地草地畜牧业的可持续发展具有重要的意义。 相似文献