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1.
高标准农田建设是我国“藏粮于地”战略的重要抓手,是确保粮食产能的重要支撑。在梳理大量参考文献、政策文件和标准规范的基础上,针对现阶段高标准农田建设存在管理体制不完善、空间潜力不足、投资标准偏低、建设质量不高等问题,总结归纳高标准农田建设模式总体构架,通过对我国高标准农田建设综合评价结果排名靠前和提升较快的省份开展高标准农田建设模式调查研究,围绕管理体制、规划布局、建设标准、资金保障以及实施管理方面,提出系统构建高标准农田建设模式的对策建议,为提高高标准农田建设质量作有益参考。 相似文献
2.
指出了人口老龄化是社会发展的必然趋势,也是当前中国面临的重要社会问题之一,国家和地方各级政府出台了一系列政策,切实保障老年人的权益。森林公园除保护其范围内自然环境和自然资源外,为人们的游憩、疗养、避暑和文化娱乐等提供了良好的环境,逐渐成为老年人休闲娱乐生活的选择。选取浙江丽水白云国家森林公园为研究对象,通过实地踏查、问卷调查和随机访谈等方法,深入调查了老年人个人基本资料及背景、活动状况和使用情况,对3类典型空间和4类景观元素进行了详细地分析,针对不足之处提出了相应的优化建议,以期为相关公园绿地的适老性规划设计提供建设思路。 相似文献
3.
Utilizing a DUALEM‐421 and inversion modelling to map baseline soil salinity along toposequences in the Hunter Valley Wine district
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In the oldest commercial wine district of Australia, the Hunter Valley, there is the threat of soil salinization because marine sediments underlie the area. To understand the risk requires information about the spatial distribution of soil properties. Electromagnetic (EM) induction instruments have been used to identify and map the spatial variation of average soil salinity to a certain depth. However, soils vary with depth dependent on soil forming factors. We collected data from a single‐frequency and multiple‐coil DUALEM‐421 along a toposequence. We inverted this data using EM4Soil software and evaluated the resultant 2‐dimensional model of true electrical conductivity (σ – mS/m) with depth against electrical conductivity of saturated soil pastes (ECp – dS/m). Using a fitted linear regression (LR) model calibration approach and by varying the forward model (cumulative function‐CF and full solution‐FS), inversion algorithm (S1 and S2), damping factor (λ) and number of arrays, we determined a suitable electromagnetic conductivity image (EMCI), which was optimal (R2 = 0.82) when using the full solution, S2, λ = 3.6 and all six coil arrays. We conducted an uncertainty analysis of the LR model used to estimate the electrical conductivity of the saturated soil‐paste extract (ECe – dS/m). Our interpretation based on estimates of ECe suggests the approach can identify differences in salinity, how these vary with parent material and how topography influences salt distribution. The results provide information leading to insights into how soil forming factors and agricultural practices influence salinity down a toposequence and how this can guide soil management practices. 相似文献
4.
Romi Novriadi Elizabeth Spangler D. Allen Davis 《Journal of the World Aquaculture Society》2019,50(2):433-447
The present study was designed to investigate the effects of diets containing advanced soy products (enzyme‐treated soy and fermented soy) or corn protein concentrate (CPC) in combination with porcine meal (PM) to completely replace poultry byproduct meal (PBM) on growth performance, body composition, and distal intestine histology of Florida pompano, Trachinotus carolinus. Four experimental diets were formulated to be isonitrogenous and isolipidic, to contain 400 g/kg crude protein and 80 g/kg lipid. A reference diet (PBM diet [PBMD]) contained 150 g/kg PBM and 495 g/kg soybean meal (SBM), and three test diets were formulated replacing PBM with 15 g/kg of CPC (CPC diet [CPCD]) or replacing all SBM and PBM with 535 g/kg fermented soy (fermented soybean meal diet [FSBMD]) or 451.3 g/kg enzyme‐treated soy (enzyme‐treated soybean meal diet [ESBMD]). All three test diets were supplemented with 38 g/kg of PM. Diets were fed based on a percentage of bodyweight adjusted after sampling the fish every 2 weeks to triplicate groups of Florida pompano juveniles (mean weight 8.06 ± 0.22 g). After 8 weeks of feeding, fish fed CPCD and ESBMD performed equally well in terms of final body weight, thermal growth coefficient, and percentage weight gain in comparison to fish fed PBMD. In all cases, feeding FSBMD resulted in poor feed conversion and lower feed intake compared to other treatments. Protein retention efficiency, whole‐body proximate composition, phosphorus, sulfur, potassium, magnesium, calcium, sodium, and zinc contents were not significantly influenced by the dietary treatments. The results obtained in the present histological study showed no significant differences in the thickness of serous layer, muscular layer, and submucosal layer of the intestine among treatments. Fish fed CPCD showed a significant widening of the lamina propria with an increase of cellular infiltration and higher presence of goblet cells compared to other dietary treatment. Based on these results, 451 g/kg ESBM or combination of 150 g/kg of CPC and 495 g/kg SBM supplemented with 38 g/kg PM can be utilized to develop a practical diet for juvenile Florida pompano without impacting growth, nutritive parameters, and several distal intestine health parameters. 相似文献
5.
Fabio Soller Luke A. Roy D. Allen Davis 《Journal of the World Aquaculture Society》2019,50(1):186-203
Stearine fish oil (SFO) and palm oil (PO) have emerged as promising alternatives for the replacement of fish oil (FO) in aquafeeds. This study evaluated the replacement of FO with alternative oils in practical diets for Litopenaeus vannamei. In a clear brackish water study (14.1 g/L) utilizing shrimp (0.29 ± 0.02 g, initial weight), FO was replaced by SFO at inclusion ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 (FO:SFO) and PO as 90% of FO. After 55 days, no significant differences (p < 0.05) in final weight, growth, or survival of shrimp were observed. A second trial (8 weeks) in low‐salinity water (2.1 g/L) with shrimp (0.92 ± 0.02 g, initial weight) evaluated diets with 100% FO, 100% SFO, 90% PO, 90% soybean oil (SO), or 90% flaxseed oil (FXO) as a replacement for FO and four commercially produced diets with 2% of FO, SO, PO, or FXO. One treatment received half rations of the commercial FO diet, and one treatment was based entirely on natural productivity. Results show that the fatty acid profiles of the tail muscle conformed to the lipids of the feed, and highly unsaturated fatty acids (HUFAs) were preserved. Following 8 weeks of culture, there were no significant differences in production performance. 相似文献
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7.
《Soil Use and Management》2018,34(1):1-8
Cost‐effective strategies for using chemically amended organic fertilizers need to be developed to minimize nutrient losses in surface and groundwater. Coupling specific soil physical and chemical characteristics with amendment type could increase their effectiveness. This study investigated how water‐extractable phosphorus (P) was affected by chemical amendments added to pig slurry and how this effect varied with soil properties. A 3‐month incubation study was conducted on 18 different mineral soils, stored at 10 °C and 75% humidity and treated with unamended and amended slurry which was incorporated at a rate equivalent to 19 kg total P (TP )/ha. The amendments examined were commercial‐grade liquid alum, applied at a rate of 0.88:1 [Al:TP ], and commercial‐grade liquid poly‐aluminium chloride (PAC ), applied at a rate of 0.72:1 [Al:TP ]. These amendments were previously identified by the authors as being effective in reducing incidental losses of P. The efficacy of the amendments varied with the soil test P, the degree of P saturation (DPS ) and the Mehlich aluminium, iron and calcium, but not soil texture. Chemical amendments were most effective in soils with DPS over approximately 20%. Due to their high cost, the incorporation of amendments into existing management practices can only be justified as part of a holistic management plan where soils have high DPS . 相似文献
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9.
卿平勇 《中南林业调查规划》2005,24(3):21-24
探讨了西北工业大学金叶信息技术学院中心绿地的景观设计方案,本着生态可持续发展、以人为本和浓郁文化内涵的原则,创造一个以自然景观和人文景观相结合的优美环境,为师生提供具有园林艺术氛围的学习、交流、休闲、娱乐和生活的场所. 相似文献
10.
目的:比较多层螺旋CT(multi-slice spiral CT,MSCT)与核磁共振血管成像(MRA)、数字减影(DSA)对主动脉夹层(aortic dissection,AD)的诊断价值。方法:对17例AD患者行MSCT检查,并与MRA、DSA的检查结果进行比较。结果:对17例AD患者用MSCT、MRA、DSA都能作出诊断(按DeBakey分型,Ⅰ型有4例,Ⅱ型有1例,Ⅲ型有12例),但只有MSCT能明确显示夹层的范围和分支的受累情况,以及剥离内膜瓣、裂口及主动脉的周围情况。而MRA对裂口的检出率只有21.74%,DSA可达87.0%。结论:MSCT对AD的分型以及破裂口的定位诊断更具准确性,对动脉分支显示更清晰。 相似文献