不同阶段猪用颗粒饲料物理性能的对比分析

对某饲料厂不同阶段猪用4种颗粒饲料的物理性能包括直径、长度、硬度、容重、含粉率和耐久性指数（Pellet Durability Index, PDI）等进行测定,对结果进行归类总结并采用统计学的方法参照有关标准进行分析。结果表明,4种颗粒饲料直径在2.87~3.94 mm之间,母猪料直径最大,小猪料最小,两两之间差异显著（P<0.05）,而且随着猪只年龄的增加,颗粒饲料的直径呈递增趋势。颗粒长度在8.62~11.94 mm之间,以大猪料最长,小猪料最短,长径比偏高。颗粒硬度在3.86~6.47 kg之间,以大猪料最大,小猪料最小,中小猪料显著低于大猪料和母猪料（P<0.05）,只有小猪料符合有关要求。颗粒容重在576.7~614.6 g/L之间,母猪料最大,小猪料最小,两两之间差异显著（P<0.05）,与直径呈相同的增减趋势。含粉率以小猪料最大,且只有小猪料与大猪料之间差异显著（P<0.05）。颗粒PDI以大猪料最大,小猪料最小,各阶段猪料的含粉率和PDI均符合有关要求。建议饲料厂家注重颗粒饲料物理性能指标的控制,调整饲料配方和工艺参数,不断改进颗粒饲料的质量。     

水流冲击多段滞留气团的三维数值模拟

针对水气两相瞬变现象,充分考虑了水体弹性、气体可压缩性、水-气交界面的动态运动以及多段气团间相互作用,采用三维CFD方法对起伏管道内含多段滞留气团的水气两相作用进行建模和模拟,选择Standard k-ε湍流模型进行模拟研究,将三维计算结果、现有一维模型计算结果与试验结果进行对比分析,并通过水气两相分布图展现动态变化过程.结果表明:与一维模型相比,三维CFD模型能够更为准确地模拟起伏管道内瞬变压力波动,并且能够清楚描述水气掺混、耦合的动态变化.水流冲击初始两段滞留气团压力波动曲线显示,多气团间的瞬变压力并非同步变化,可能呈现多气团峰值压力交替出现的情况,这与初始气团长度密切相关.水气交界面自由变化,阻断水体长度时刻发生变化,当水体运动到管道弯曲处时会产生新的阻断水体,将气团分成若干部分.     

基于准静态同轴探头模型的土壤复介电测量方法

末端开路同轴探头法测量土壤复介电值用于表征土壤含水率具有准确、快捷的优点。针对目前土壤介电同轴探头集总测量模型没有充分考虑探头的参数以及土壤体积对测量结果影响等问题，基于电磁场理论，对末端开路同轴探头建立了准静态数学模型，适用于土壤的复介电常数准确测量。通过全波软件仿真和模型计算结果对比，以无水乙醇介电实测值和理论值对比，验证模型的准确性。采用本文介电测量模型对不同含水率的黄绵土进行测量计算，复介电常数实部与实测土壤含水率二阶多项式拟合决定系数大于0.965，表明本文所提土壤介电测量方法适用于土壤复介电常数和含水率的测量。     

滴灌下生物质改良材料对盐渍土水盐氮运移的调控效应

为探究生物质改良材料对滴灌盐渍土水、盐、肥运移过程的调控效应，采用土箱模拟试验，研究了水肥一体化滴灌条件下，生物炭和腐殖酸两种改良材料对盐渍土水、盐、氮运移和再分布过程及其时空分布特征的影响规律。结果表明：在滴灌条件下，盐渍土壤水盐的时空动态变化表现出明显的水分入渗驱动的盐分运移过程和蒸发扩散驱动的水盐再分布过程；铵态氮含量在时间上表现出先增大、后减小的变化趋势，在空间上的运移再分布特征较弱；硝态氮含量初始时空分布表现出与水盐相似的运移特征，受铵态氮硝化作用的多重影响，后期空间分布与铵态氮空间分布相似；生物炭通过提高土壤饱和导水率，增大了入渗阶段土壤水、盐、氮的运移速率和分布范围；腐殖酸通过提高土壤田间持水率增大了再分布过程土壤水、盐、氮的分布范围和强度，同时其对尿素的水解和硝化过程表现出更强的抑制效果。应用生物质改良材料在改变土壤物理性状进而调控滴灌土壤水盐运移的同时，还影响土壤氮素转化运移过程及其分布，这为水肥一体化滴灌盐渍农田的节水、控盐、减肥治理提供了理论基础。     

基于"量-质-域-流"四维指标体系的水资源荷载状况评价——以黑河流域三地市为例

随着社会经济用水不断增加，水资源供需矛盾加剧，水资源系统出现荷载不均衡现象，制约了区域发展，危及生态环境良性循环。本文从水资源系统的负荷需求和承载能力出发，基于“量、质、域、流”四个维度构建水资源荷载均衡评价指标体系，采用指标规范化的正态云模型，评价2015年黑河流域张掖市、酒泉市、阿拉善盟水资源配置方案的荷载均衡状况，并依据负荷与承载能力评分二维坐标，分出低负荷-高承载能力、低负荷-低承载能力、高负荷-高承载能力和高负荷-低承载能力四个分区。评价结果表明：2015年三地水资源荷载状况均为Ⅳ级，张掖市综合评分为3.697，酒泉市为3.657，阿拉善盟为3.901，三地均处于高负荷-低承载能力区域；三地在水质维度上处于低负荷-高承载能力区间，水质维度评分均处于Ⅱ级，酒泉市水质评分优于张掖市，张掖市水质评分优于阿拉善盟；在水量、水域、水流维度上均处于高负荷-低承载能力区间，水量方面三地处于Ⅳ级，张掖市优于酒泉市，酒泉市优于阿拉善盟；水域方面张掖和阿拉善盟评分均处于Ⅴ级，酒泉评分处于Ⅳ级；水流方面三地均处于Ⅴ级。需要采取调控手段在水量、水域、水流方面上进行“增强承载”和“卸荷”。     

Poorly crystalline iron and aluminium oxides contribute to the carbon saturation and sorption of dissolved organic carbon in the soil

Soil carbon (C) saturation implies an upper limit to a soil's capacity to store C depending on the contents of silt + clay and poorly crystalline Fe and Al oxides. We hypothesized that the poorly crystalline Fe and Al oxides in silt + clay fraction increased the C saturation and thus reduced the capacity of the soil to sorb additional C input. To test the hypothesis, we studied the sorption of dissolved organic carbon (DOC) on silt + clay fractions (<53 µm) of highly weathered oxic soils, collected from three different land uses (i.e., improved pasture, cropping and forest). Soils with high carbon saturation desorbed 38% more C than soils with low C saturation upon addition of DOC, whereas adsorption of DOC was only observed at higher concentration (>15 g kg^?1). While high Al oxide concentration significantly increased both the saturation and desorption of DOC, the high Fe oxide concentration significantly increased the desorption of DOC, supporting the proposition that both oxides have influence on the DOC sorption in soil. Our findings provide a new insight into the chemical control of stabilization and destabilization of DOC in soil.     

岩溶流域典型农业区水体氢氧同位素的空间异质性及形成机制

分别于平水期和枯水期采集了花溪河流域典型农业区地表水和地下水样品。利用氢氧同位素示踪技术,结合土地利用类型对研究区不同水体的补给来源、季节变化及主要影响过程进行了分析,并对不同水体氢氧同位素值进行了空间插值分析,同时对其形成机制进行了分析,阐明了不同土地利用类型影响下的主要水文过程。结果表明:(1)研究区不同水体的主要补给来源为当地大气降水,月亮湖水库受蒸发作用影响明显,地表水和地下水的δD和δ~(18)O整体上呈现平水期高于枯水期的特征。(2)地下水的δD和δ~(18)O在枯水期与平水期均呈现明显的空间分异性特征,西部水田/水库集中区富集,东部旱地集中区贫化,土地利用对研究区环境水文过程影响明显。该研究结果有助于了解不同土地利用方式下地表水对地下水的影响,为流域管理提供科学依据。     

Cultivation effects on soil texture and fertility in an arid desert region of northwestern China

In arid desert regions of northwestern China, reclamation and subsequent irrigated cultivation have become effective ways to prevent desertification, expand arable croplands, and develop sustainable agricultural production. Improvement in soil texture and fertility is crucial to high soil quality and stable crop yield. However, knowledge on the long-term effects of the conversion of desert lands into arable croplands is very limited. To address this problem, we conducted this study in an arid desert region of northwestern China to understand the changes in soil physical-chemical properties after 0, 2, 5, 10, 17, and 24 years of cultivation. Our results showed that silt and clay contents at the 17-year-old sites increased 17.5 and 152.3 folds, respectively, compared with that at the 0-year-old sites. The soil aggregate size fraction and its stability exhibited an exponential growth trend with increasing cultivation ages, but no significant change was found for the proportion of soil macroaggregates (>5.00 mm) during the 17 years of cultivation. The soil organic carbon (SOC) content at the 24-year-old sites was 6.86 g/kg and increased 8.8 folds compared with that at the 0-year-old sites. The total (or available) nitrogen, phosphorus, and potassium contents showed significant increasing trends and reached higher values after 17 (or 24) years of cultivation. Changes in soil physical-chemical properties successively experienced slow, rapid, and stable development stages, but some key properties (such as soil aggregate stability and SOC) were still too low to meet the sustainable agricultural production. The results of this long-term study indicated that reasonable agricultural management, such as expanding no-tillage land area, returning straw to the fields, applying organic fertilizer, reducing chemical fertilizer application, and carrying out soil testing for formula fertilization, is urgently needed in arid desert regions.     

Quantitative trait loci responsible for the difference in γ-oryzanol content in brown rice between japonica-type and indica-type rice cultivars

γ-Oryzanol is a main oleophilic component in rice bran oil and has been well recognized as a good dietary supplement for human health, as well as having uses in industrial materials. japonica-type rice cultivars generally showed significantly higher contents of total γ-oryzanol in brown rice compared with indica-type cultivars, although within-group variation was significant. The objective of this study was to explore quantitative trait loci (QTLs) responsible for the difference in the γ-oryzanol content between japonica-type and indica-type rice cultivars, using recombinant inbred lines (RILs), backcross inbred lines (BILs), and corresponding chromosome segment substitution lines (CSSLs) derived from crosses between japonica-type and indica-type. Results from RILs and BILs showed that eight QTLs were detected with R² from .09 to .16. Nine candidate regions for QTL were also suggested from corresponding CSSLs. These QTLs from RILs and BILs and the candidate regions from CSSLs were not overlapped, although one QTLs was mapped near the boundaries of the respective candidate region. At four QTLs and three candidate regions, alleles or segments from japonica-type caused higher contents than those from indica-type. On the other hand, at the other four QTLs and six candidate regions, alleles or segments from indica-type caused higher contents than those from japonica-type, which is a reverse result to the parental differences. This result strongly suggested that alleles with increasing effects on γ-oryzanol content could be accumulated not only from japonica-type but also from indica-type, leading to a potential for increase in γ-oryzanol content in future breeding programs.     

Changes in photosynthesis,growth, and sugar content of commercial sugarcane cultivars and Erianthus under flood conditions

Sugarcane (Saccharum spp.) is an economical crop in the tropical and subtropical countries. However, because of global climate change, flooding has become problematic, particularly during the rainy season, in Thailand. We investigated the effects of floods on three commercial sugarcane cultivars, namely NiF8, U-thong 6 (UT6), and U-thong 9 (UT9), as well as Erianthus spp. Growth was assessed using a pot experiment in a glasshouse with two treatments: (1) control and (2) 60 d of flooding followed by 30 d of normal conditions. In comparison with control, during prolonged flooding, Erianthus showed greatly decreased CO₂ assimilation, whereas NiF8, UT6, and UT9 showed slightly declined CO₂ assimilation. Growth in plants subjected to 60 d of flooding was less influenced by floods while sucrose content was not affected except in UT6. During flooding, some roots died, resulting in plants compensating adventitious roots to offset the negative effects of root death and to assist them in maintaining their growth, which appeared from the submerged nodes, with different characteristics for each cultivar. However, 30 d after draining, roots remained damaged, while adventitious roots died, resulting in lesser growth as compared with the control, but it did not significantly affect sucrose content and sugar yield. This study suggests that sugarcane plants need to produce the adventitious roots to compensate their roots’ death during flooding and require time to recover their root system after flooding for obtaining the optimum yield and quality at harvest.