有机质浸染砂水泥土的力学特性及本构关系

为研究海南省海湾地区分布的有机质浸染砂水泥土的力学特性,该文首先对有机质浸染砂水泥土和标准砂水泥土进行无侧限抗压强度对比试验(采用配合比均为熟石灰掺入比7.5%、水泥掺入比20%、水灰比0.45),定量分析养护龄期对其无侧限抗压强度及试样破坏形式的影响。然后对有机质浸染砂水泥土进行单轴抗压试验,获得了水泥土材料的应力-应变全过程曲线、刚度变化规律以及改进邓肯-张本构模型。结果表明:1)有机质浸染砂水泥土试样的破坏类型为塑性剪切破坏和脆性剪切破坏;2)有机质浸染砂水泥土抗压强度随着养护龄期的增加基本呈指数形式增长,但在养护龄期14 d后,增长速度逐渐降低并趋于稳定;3)随着养护龄期增长,水泥土刚度增加。在加载初期,水泥土切线模量随着轴向应变增加而增大,呈现刚度硬化现象;4)基于单轴抗压试验得到应力-应变全过程曲线,可分为2个阶段:塑性阶段、软化阶段;5)通过对应力-应变全曲线的描述,得到了修正的邓肯-张模型,确定模型参数后,与实测数据对比发现,该修正模型可以模拟有机质浸染砂水泥土的应力-应变关系。     

施肥对灌漠土作物产量、土壤肥力与重金属含量的影响

有机物还田是提升土壤肥力的主要措施,但也存在造成土壤金属污染的潜在风险。为查明不同有机物还田对土壤质量及作物产量的影响,本文通过长期定位试验,研究了无肥对照、常规施化肥(氮磷配施)以及70%常规化肥与牛粪、沼渣、污泥、鸡粪、菌渣和猪粪配施对土壤理化性状、有机碳和氮的固存率、氮磷钾活化系数、作物产量及重金属含量的影响。结果表明:牛粪、沼渣、污泥、菌渣、鸡粪和猪粪与70%化肥配施虽作物产量与常规施化肥相似,但6种有机物处理土壤有机质、全氮和碱解氮含量都较常规施化肥处理显著增加,污泥、鸡粪和猪粪处理土壤全磷与速效磷含量较常规施化肥处理显著增加,而且牛粪、沼渣、鸡粪和猪粪处理的速效钾、土壤磷活化系数和土壤钾活化系数较常规施化肥处理也显著提升。牛粪、沼渣、污泥、菌渣、鸡粪和猪粪处理土壤有机碳固存率为36.42%～71.61%,较常规施化肥处理都显著提高;而其氮固存率为6.47%～49.44%,仅有菌渣处理与常规施化肥处理差异不显著,而其他处理较常规施化肥处理显著增加。长期施鸡粪和菌渣处理的土壤铜含量较常规施化肥处理显著增加,增加量分别为4.17mg·kg~(-1)和14.2mg·kg~(-1);而污泥、鸡粪和菌渣处理的土壤锌含量较常规施化肥处理显著增加,增加量分别为13.53 mg·kg~(-1)、22.60 mg·kg~(-1)和49.73mg·kg~(-1)。综上,等有机质(4 500kg×hm~(-2))的牛粪、沼渣、污泥、菌渣、鸡粪和猪粪可替代30%氮磷肥,作物产量不受影响;不同有机物培肥土壤效果为污泥、鸡粪和猪粪优于牛粪和沼渣,而沼渣的培肥效果略差。为保证土壤环境质量稳定不恶化,种植小麦时有机物铜和锌的年携入量应分别低于53.01g×hm~(-2)和221.30 g×hm~(-2),而种植玉米时应分别低于153.40 g×hm~(-2)和347.04 g×hm~(-2)。     

炭肥比和膨润土粘结剂对炭基肥颗粒理化及缓释特性的影响

为探究炭肥比和膨润土粘结剂对生物炭基肥理化及缓释特性的影响,以生物炭为基底,分别制备了炭肥比1:4,膨润土粘结剂质量分数为20%、15%、10%、5%和粘结剂质量分数10%,炭肥比为1:6、1:5、1:4、1:3的柱状尿素和氯化钾生物炭基肥颗粒,分析了生物炭基肥颗粒的理化及缓释特性。结果表明,在炭肥比为1:4条件下,膨润土粘结剂质量分数越高,生物炭基肥微观结构越紧密,力学和缓释特性越好,质量分数为20%时,氯化钾和尿素生物炭基肥平均抗压强度分别为286.78和281.27 N,前3天养分淋出率分别为45.53%和36.87%。在膨润土粘结剂质量分数为10%条件下,炭肥比越高,生物炭基肥缓释性能越好,炭肥比为1:3时,氯化钾和尿素生物炭基肥前3天养分淋出率分别为42.06%和40.32%。同时,氯化钾生物炭基肥表面孔隙先增后减,炭肥比为1:6和1:3的平均抗压强度分别为271.25和282.42 N。尿素生物炭基肥内部结构中孔隙变多,炭肥比为1:6时,平均抗压强度为最大值267.84 N。综合考虑,满足中等肥料浓度要求时,膨润土粘结剂质量分数为20%、炭肥比为1:4或膨润土粘结剂质量分数为10%、炭肥比为1:3的生物炭基肥成型配方较优。     

不同太阳能干燥量对对虾干燥品质特性和能耗的影响

以南美白对虾为试材，研究了不同太阳能干燥量（1、2、3、4 kg）对南美白对虾干燥速率、水分活度、硬度、弹性、咀嚼性、色泽、收缩率、复水率等品质特性和干燥能耗的影响。结果表明，干燥量越大，干燥速率越慢，干燥时间越长；不同干燥量干燥初期，南美白对虾的水分活度变化不明显，不同干燥量间差异不明显，当干燥到一定程度（干燥到5 h时），不同干燥量下水分活度出现显著差异（P＜0.05）；干燥量为3 kg与4 kg 时，南美白对虾干燥产品咀嚼性分别为137.41 mJ和131.06 mJ，显著优于其他干燥量（P＜0.05）；不同干燥量条件下，南美白对虾干燥后的色泽变化趋势不明显；干燥量3 kg与4 kg，干燥后的南美白对虾收缩率分别为22%和21.2%，复水率分别为73.0%和76.5%，收缩率显著低于、复水率显著高于其他干燥量（P＜0.05）；干燥量为3 kg，干燥时间为7 h时，总干燥能耗最低，为10.25 kWh，显著低于其他处理（P＜0.05）。干燥量3~4 kg时，南美白对虾干燥产品的咀嚼性、色泽、收缩率、复水率等理化特性优于其他干燥量，干燥能耗低，适于干燥南美白对虾产品。     

广西钦州市菠萝山不同朝向土壤理化性状比较分析

以钦州市钦南区菠萝山为研究对象，采用环刀取土烘干法及混合土样法对不同区域（东南、西南、西北）土壤的理化性状进行分析。结果表明：不同采样区域（东南、西南、西北）土壤含水量和物理性粘粒（＜0.01 mm）差异显著，东南朝向含水量及粘粒含量最高，其次是西南朝向，西北朝向最低；不同采样区域（东南、西南、西北）土壤容重、孔隙度及 pH 值差异不显著。通过该研究表明，山体的不同方向对土壤发育及水土保持有显著影响，人为干扰影响山体土壤良性发展。     

纤维目数对纤维板力学性能和成本的影响研究

采用热磨法研磨纤维,研究不同纤维目数(40~100目,20~120目,10~130目)对纤维板力学性能和成本的影响。在保证制作质量合格的纤维板试件基础上,对其进行力学性能试验,验证确定纤维目数区间的合理性,并利用确定的纤维目数区间进行密度和施胶量的单因素对比分析;分析其对力学性能和成本的影响。研究结果表明:纤维目数在40~100目时,可通过降低试件密度或减小施胶量,在保证制品较好力学性能的前提下降低制备成本,可实现优质优价经济效益最大化;从纤维板制品制备成本分析得出:采用上述三种纤维目数区间,在保证制品质量要求的前提下,可实现纤维目数区间与制品质量等级的合理匹配,达到合理利用原材料降低成本的效果。     

Characteristics of grain quality and starch fine structure of japonica rice kernels following preharvest sprouting

Preharvest sprouting (PHS) is one of the most serious defects that impacts rice production and grain quality. Knowledge about the effects of PHS on the eating and cooking quality (ECQ) of milled rice is limited. Here, we selected four japonica rice varieties to study the influences of PHS on grain quality. The results showed that PHS strongly led to poor grain appearance and the development of small starch granules whose surfaces were eroded. Analysis of starch fine structure revealed that PHS resulted in amylose (AM) degradation; in particular, PHS caused a decrease in the content of long AM chains. Moreover, PHS led to a decrease in the content of short amylopectin (AP) chains in the varieties Yandao 815 (YD815), Wuyugeng 27 (WY27) and Yangeng 13 (YG13), while the variety Sidao 785 (SD785) displayed the opposite trend. We propose that the main reasons for the decrease in starch crystallinity and the pasting profiles of the germinated rice were due to both the tendency of the AM content to decrease and the degree of this decrease in the content of the different AM chains along with changes in AP and other major components. All these changes caused by PHS led to a decrease in both ECQ and palatability of milled rice.     

饲草作物对土壤健康与农业可持续发展的作用

饲草作物是指为增加土壤肥力,防止土壤侵蚀,累积和保护土层,增加土壤养分和含水率以及提高土壤质量而种植的植物。饲草作物为农田土壤提供了诸多益处,其还有助于增加和维持土壤中的微生物多样性。本文对多种饲草作物对土壤特性的作用,如土壤含水量、土壤微生物的活动、土壤碳固存、土壤硝态氮淋失、土壤水分和土壤健康等进行综述。饲草作物的选择通常取决于其自身对土壤的作用,其他考虑因素还包括天气条件,播种时间,是否为豆科植物以及杀灭饲草作物的时间和方法。研究表明,饲草作物也可用于减缓气候变化,抑制作物中的杂草,增加可交换的营养物质如Mg2+和K+,具有一定的经济性。另外,覆盖作物也会存在一些问题,包括杀灭覆盖作物的方法,其可能成为病原体的寄主,饲草作物的再生性以及短期收益不明显。尽管有一些局限,饲草作物仍被认为可以明显改善土壤整体健康状况,为主栽作物提供可持续的生态环境。     

Effect of germination time and temperature on the functionality and protein solubility of sorghum flour

Sorghum was germinated for different time (12, 24, 36 and 48 h) at different temperatures (25, 30 and 35 °C) and the changes in their nutritional and functional properties of germinated sorghum flour were assessed and compared with native sorghum flour. Germination inversely affects the crude protein, fat, fibre and ash content. A decrease in water absorption and swelling power and increase in oil absorption capacity was observed due to enzymatic starch modification as the germination duration progressed. Germination of sorghum increased the gel consistency while paste clarity was decreased as compared to native flour. Proteins were modified by action of enzymes during higher germination time and temperature conditions, which results in significantly higher protein solubility of germinated sorghum flour, which also result in enhancing the foaming and emulsifying properties of the flour. Lowest % synersis value and least gelation concentrations were observed in native sorghum has, which increased during germination and were highest in sorghum germinated for 48 h at 35 °C. Germination in overall can be used as low cost natural bio-processing technique for the preparation of modified flour with enhanced function properties without chemical modification or genetic engineering.     

Urban land-use impacts on composition and spatiotemporal variations in abundance and biomass of earthworm community

Soil fauna can sensitively respond to alterations in soil environment induced by land-use changes.However,little is known about the impact of urban land-use changes on earthworm communities.In this study,three land-use types(i.e.,forest,nursery and abandoned lands)were chosen to identify differences in diversity,abundance and biomass of earthworm community in Kunming City.Urban land-use had a pronounced difference in species composition,evenness and diversity of earthworm communities.Forest land had the highest density,biomass and diversity of the earthworm communities.Total abundance was dominated by endogeic species in nursery land(70%)and abandoned land(80%),whereas in the forest land,the earthworm community comprised epigeic,endogeic and anecic species.Temporal changes in earthworm density and biomass were also significantly affected by land-use change.Total density and biomass of earthworms in the forest and nursery lands were highest in September,but highest in the abandoned land in October.The influence of soil physicochemical properties on the earthworm density and biomass also varied with land-use types.Soil temperature significantly affected earthworm density and biomass in the three land-use types.Soil pH was positively correlated with earthworm biomass in the forest land,but negatively associated with earthworm density in the abandoned land.Soil organic matter was positively correlated only with density and biomass of earthworms in the nursery and abandoned lands.Our results suggest that the species composition,abundance and biomass of earthworm communities can be determined by the modification of soil properties associated with urban land-use type.