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排序方式: 共有334条查询结果,搜索用时 390 毫秒
1.
在牧草生长季节(5~9月)对小哨牧场放牧演替形成的5个草地型草地的牧草进行生长速率、牧草产量及养分的逐月观测,生长速率测定显示,白三叶+东非狼尾草和东非狼尾草+非洲狗尾草两个草地型草地均出现两个生长峰值,分别在6月和9月,其余3个草地型草地只有一个生长高峰。干物质产量和牧草养分测定结果表明,白三叶+东非狼尾草和白三叶+非洲狗尾草+画眉草两种草地型草地表现最好,可以在气候环境条件类似的地区推广种植利用;白三叶+画眉草和白三叶+非洲狗尾草两种草地型草地表现优良,可以在草地改良中,根据当地实际情况选择性地加以种植;东非狼尾草+非洲狗尾草型草地表现较差,不提倡种植。 相似文献
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Janaina Braga do Carmo Marisa de Cssia Piccolo Cristiano Alberto de Andrade Carlos Eduardo Pellegrino Cerri Brigitte Josefine Feigl Erclito Sousa Neto Carlos Clemente Cerri 《Soil & Tillage Research》2007,96(1-2):250-259
Anthropogenic conversion of primary forest to pasture for cattle production is still frequent in the Amazon Basin. Practices adopted by ranchers to restore productivity to degraded pasture have the potential to alter soil N availability and N gas losses from soils. We examined short-term (35 days) effects of tillage prior to pasture re-establishment on soil N availability, CO2, NO and N2O fluxes and microbial biomass C and N under degraded pasture at Nova Vida ranch, Rondônia, Brazilian Amazon. We collected soil samples and measured gas fluxes in tilled and control (non tilled pasture) 12 times at equally spaced intervals during October 2001 to quantify the effect of tillage. Maximum soil NH4+ and NO3− pools were 13.2 and 6.3 kg N ha−1 respectively after tillage compared to 0.24 and 6.3 kg N ha−1 in the control. Carbon dioxide flux ranged from 118 to 181 mg C–CO2 m2 h−1 in the control (non-tilled) and from 110 to 235 mg C–CO2 m2 h−1 when tilled. Microbial biomass C varied from 365 to 461 μg g−1 in the control and from 248 to 535 μg g−1 when tilled. The values for N2O fluxes ranged from 1.22 to 96.9 μg N m−2 h−1 in the tilled plots with a maximum 3 days after the second tilling. Variability in NO flux in the control and when tilled was consistent with previous measures of NO emissions from pasture at Nova Vida. When tilled, the NO/N2O ratio remained <1 after the first tilling suggesting that denitrification dominated N cycling. The effects of tilling on microbial parameters were less clear, except for a decrease in qCO2 and an increase in microbial biomass C/N immediately after tilling. Our results suggest that restoration of degraded pastures with tillage will lead to less C matter, at least initially. Further long-term research is needed. 相似文献
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通过研究固始鸡、罗曼蛋雏鸡和艾维茵肉仔鸡生长、养分沉积、肉质特性的差异,探讨品种与生长、代谢和肉质间的关系。选用1日龄雄性固始鸡、艾维茵肉仔鸡、罗曼蛋雏鸡各120只,按体重随机分为6个重复,每重复20只,在相同日粮条件下进行8周的生长试验,并进行屠宰试验和肉质测定。结果表明:(1)3种鸡在体重、日增重、采食量、饲料转化率间存在极显著差异(P<0.01),固始鸡低于罗曼蛋雏鸡,罗曼蛋雏鸡低于艾维茵肉仔鸡;(2)固始鸡和罗曼蛋雏鸡的代谢能和粗蛋白质沉积效率显著低于艾维茵肉仔鸡(P<0.05);(3)固始鸡和罗曼蛋雏鸡的肌肉滴水损失、肌纤维直径、羟脯氨酸含量显著低于艾维茵肉仔鸡(P<0.05),固始鸡胸肌和腿肌中超氧化物歧化酶活性则极显著高于蛋鸡(P<0.01),蛋鸡极显著高于肉鸡(P<0.01)。与快速生长的鸡品种相比,慢速生长的固始鸡具有较低的代谢能和粗蛋白质沉积效率,具有较低的肌肉滴水损失、羟脯氨酸含量及较细的肌纤维,并具有较高的肌肉抗氧化水平。 相似文献
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Soil chemical, biochemical, biological and structural properties were measured in two New Zealand loessial soils that were topsoil-mined 10 and 25 years ago respectively. Measurements at the 10-year site were compared to some earlier measurements made at this site and the data combined in a chronological sequence for analysis. Topsoil mining had a large, detrimental impact on the soil microbial biomass, the earthworm populations, easily mineralizable N and soil enzyme activities. However, most of these properties substantially recovered, to 80-90 per cent of the levels in unmined soils, within 10-25 years of restoration under pasture. In contrast, while total soil C and N were less affected by topsoil mining, their recovery was much slower. Stabilities of macro-aggregates of soil had fully recovered within 10-25 years after topsoil mining. The apparent changes in all the measured properties between 10 and 25 years of restoration were small in comparison with changes between 0-10 years of restoration after topsoil mining. The total C content of both soils under pasture appeared unlikely to attain the levels present in unmined soils. In soils undergoing restoration, the ratio of microbial C/total soil C may be a useful index of soil ‘biological stability’. Sulphatase activity may reflect the recovery of pasture production. 相似文献
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利用最小二乘法拟合线性模型,探索了与鸡体型参数和屠体性状紧密相关的10个微卫星座位与商品代固始鸡体型参数和屠体性状的关系。用变性聚丙烯酰胺凝胶电泳法,分析了这10个微卫星位点在100只商品代固始鸡中的遗传变异,计算了微卫星位点的等位基因频率、杂合度、多态信息含量和有效等位基因数。结果表明,其中8对微卫星引物表现出多态,平均每个座位检测到3.625个等位基因(3~4个),平均多态信息含量为0.520 3,平均杂合度为0.626 0。通过最小二乘分析,检测到MCW0295、MCW0006、MCW0185、ADL0192位点与体型参数中的5种性状间存在不同程度的关联性;MCW0006、MCW0185、ADL0105位点与商品代固始鸡6个屠体性状中的4个性状显著连锁。MCW0295位点的AC基因型有望作为质量的早期选择辅助标记,MCW0006和MCW0185位点的CC基因型有望作为质量、胸宽、胸深、胫长、体斜长的早期选择辅助标记,ADL0192位点的AB基因型有望作为质量、胸宽的早期选择辅助标记;MCW0006位点的CC基因型有望作为全净膛率的选择辅助标记,MCW0185位点的AD基因型有望作为胸肌率和腿肌率的选择辅助标记,ADL0105位点的CC基因型有望作为腹脂率的选择辅助标记。 相似文献
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The objectives of this study were to characterize the glycemic and insulinemic responses of Thoroughbred broodmares fed late spring pasture only or a mixture of pasture and a high starch or low starch feed and to test hypotheses about differences in the glycemic and insulinemic effects of these dietary regimes. A group of 15 mares were divided into three treatment groups; pasture and high starch feed (PHS), pasture and low starch feed (PLS), and pasture only (PO) and maintained in these groups for 4.5 months prior to this study. These groups were maintained on a single pasture that was temporarily divided into three sections. The study protocol was conducted over two days. On day 1 the mares were fed their respective treatments and on day 2 all mares were allowed access to pasture only. On both days plasma glucose and insulin were measured in samples taken over a 7.5 h period. Baseline measurements for glucose and insulin were not different between any of the treatment groups on either day (P > 0.05). The baseline insulin concentrations of these pasture-kept mares (26.7 ± 8.3 mIU/L) were high compared to those reported from stall-kept horses. Plasma glucose and insulin on day 1 were influenced by treatment group, sample time, and an interaction between treatment and time (P < 0.05). On day 2 there was no significant influence of treatment group (P > 0.05). Glucose and insulin rose to higher (P < 0.01) peak concentrations in the PHS group on day 1 when compared to the PLS and PO groups, with no difference (P > 0.05) detected between the PLS and PO groups. These results are reflected in greater areas under the concentration-time curves for glucose and insulin in the PHS group on day 1 (P < 0.05). On day 2 there were no differences in any of the glucose and insulin characteristics for any of the treatment groups (P > 0.05). These results indicate a clear difference in the glycemic and insulinemic effect of the PHS feed compared to the PLS and PO groups. Of further interest are the glucose and insulin characteristics of these pasture-kept mares that indicate a low insulin sensitivity and high insulin secretory response. This study provides further information on factors influencing glycemic and insulinemic responses in horses. 相似文献
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A. E. Smith 《Crop Protection》1990,9(6):410-414
Laboratory and growth chamber research was conducted to determine the potential allelopathy of tissue harvested from certain weeds commonly found in pastures. Results of bioassays indicated that the weeds dogfennel and mayweed chamomile are potentially allelopathic to alfalfa and Italian ryegrass seedlings. Leaf-tissue extracts from the two weed species reduced seedling growth more than stem and root extracts. In most experiments alfalfa seedlings were influenced more than Italian ryegrass seedlings and seedling growth was influenced more than seed germination. Leaf tissue from the weed species mixed into potting soil at a concentration as low as 0.25% (w/w) significantly reduced alfalfa and Italian ryegrass plant development and foliage production. Extract and tissue concentration used in this research were estimated to be similar to concentrations expected to occur within the pasture ecosystem and below concentrations that would result in hypertonicity in the bioassays. 相似文献