长期施用氮磷和有机肥对不同种植体系土壤有效硫累积的影响

以22年定位试验为基础,研究了长期施用氮磷和有机肥（NPM）对不同种植体系土壤有效硫在剖面上分布与累积状况。结果表明,在60–80 cm土层各处理出现第一个累积峰,累积峰值为:粮饲轮作31.3、玉米连作29.2、小麦连作27.9、粮豆轮作25.6、苜蓿连作24.0 mg/kg;在140–180 cm 土层各处理又出现有效硫的第二个累积峰,累积峰值为:粮饲轮作44.7、粮豆轮作43.1、小麦连作41.0、玉米连作39.7、苜蓿连作36.5 mg/kg。第二累积峰值均大于第一累积峰值。0–200 cm土层有效硫总累积量粮饲轮作高达746.3 kg/hm2,其次为玉米连作640.6、粮豆轮作为638.3、小麦连作为622.4、苜蓿连作最小为557.3 kg/hm2。长期施用磷肥和有机肥是有效硫在土壤中累积的主要因素,有效硫在土壤剖面上有向深层迁移的趋势。不同作物对硫的吸收利用差异和不同种植方式对有效硫的累积与分布产生影响。     

Metal contamination in Nullah Dek water and accumulation in rice

Corn field experiments with two treatments, NP and NPK, where N in the form of urea, P in the form of calcium phosphate, and K in the form of KCl were applied at rates of 187.5, 33.3, and 125 kg ha^-1, respectively, on soils derived from Quaternary red clay were conducted in the hilly red soil region of Zhejiang Province, China. Plant grains and stalks were collected for determination of K content. Seven equations were used to describe the kinetics of K release from surface soil samples taken before the corn experiments under electric field strengths of 44.4 and 88.8 V cm^-1 by means of electro-ultrafiltration （EUF） and to determine if their parameters had a practical application. The second-order and Elovich equations excellently described K release; the first-order, power function, and parabolic diffusion equations also described K release well; but the zero-order and exponential equations were not so good at reflecting K release. Five reference standards from the field experiments, including relative grain yield （yield of the NP treatment/yield of the NPK treatment）, relative dry matter yield （dry matter of the NP treatment/dry matter of the NPK treatment）, quantity of K uptake in the NP treatment （no K application）, soil exchangeable K, and soil HNO3-soluble K, were used to test the effectiveness of equation parameters obtained from the slope or intercept of these equations. Correlations of the ymax （the maximum desorbable quantity of K） in the second-order equation and the constant b in the first-order and Elovich equations to all five reference standards were highly significant （P ≤ 0.01）. The constant a in the power function equation was highly significant （P 〈 0.01） for four of the five reference standards with the fifth being significant （P ≤ 0.05）. The constant b in the parabolic equation was also significantly correlated （P ≤ 0.05） to the relative grain yield and soil HNO3-soluble K. These suggested that all of these parameters could be used to estimate the soil K supplying capacity and the crop response to K fertilizer.     

Potentially hazardous element accumulation in rice tissues and their availability in soil systems after biochar amendments

Purpose

Biochar has shown to be a great product to control the bioavailability of potentially hazardous elements (PHE) in contaminated soils. Despite the advantages associated with the application of biochar in agricultural soils, relatively few studies have focused on the effects of biochar amendments on soil chemical properties, accumulation of arsenic, cadmium, zinc, and lead in rice tissues, and their availability in soil systems.

Materials and methods

The field experiment was conducted at the paddy soils in Hunan Province, China. The soil texture was sandy clay loam. Wheat-derived biochar was applied once to the experimental plots at the rates of 0, 10, 20, 30 and 40 t ha^?1, and referenced as A0, A10, A20, A30, and A40, respectively. For PHE determination, soil samples and plant samples were digested with a mixed solution of HCl:HNO₃ (4:1, V:V) and HCl:HClO₄ (4:1, V:V), respectively, and the arsenic, cadmium, zinc, and lead in the digest solution were measured by ICP-MS (Thermo Fisher Scientific, USA). The soil available fraction of PHE (arsenic, cadmium, zinc, and lead) was extracted by diethylenetriamine pentaacetic acid (DTPA) and measured by inductively ICP-MS.

Results and discussion

Biochar amendment increased chemical properties of soil organic matter, pH, electrical conductivity, cation exchange capacity, nitrate nitrogen, and available phosphorus. Soil DTPA extractable arsenic, cadmium, zinc, and lead concentrations were significantly reduced. Arsenic, cadmium, zinc, and lead in rice shoots, and arsenic, cadmium, and zinc in roots significantly decreased after amendment. Concentrations in rice tissues positively and negatively correlated with the soil available fraction of PHE and soil chemical properties, respectively. Soil electrical conductivity negatively correlated with the soil available fraction of PHE. Concentrations of arsenic, zinc, cadmium, and lead in rice roots declined relative to increases of cation exchange capacity (arsenic, zinc), available phosphorus (cadmium), and nitric nitrogen (lead) content. Similar relationships were observed between cation exchange capacity and PHE in shoots.

Conclusions

Biochar creates avoidance of PHE through regulating chemical properties through biochar sorption capacity. Cation exchange capacity, available phosphorus, and nitric nitrogen were the principle factors affecting roots uptake of arsenic, zinc, cadmium, and lead. Biochar soluble salts could decline availability of metals/metalloids in soils through precipitation. Wheat-derived biochar application is an alternative safe product to immobilize PHE in rice paddy soils by restricting the risk of PHE.

     

压力补偿灌水器水力性能影响因素分析

压力补偿灌水器以其补偿性能好、灌水均匀、铺设长度长等优点得到广泛应用。但由于影响压力补偿灌水器水力性能的因素比较复杂,因此造成压力补偿灌水器设计和优化的困难。该文通过理论分析确定影响压力补偿灌水器水力性能的关键因素包括压力调节腔出水口位置、出水口直径、压力调节腔凸台高度、直径、小槽宽度、弹性膜片的材料性能与厚度,并进一步通过水力性能试验研究了这些关键因素对灌水器水力性能的影响。结果表明:压力调节腔出水口距离越远,流量调节性能越差;压力调节腔出口直径增大会导致工作区间减小;凸台高度应该0.3 mm,否则无补偿效果;凸台直径的改变对灌水器性能影响不大;槽宽的增大有利于提高压力补偿过程的平稳性,但减弱流量调节性能;膜片硬度对补偿效果影响很大,硬度为50 HA时补偿效果最优;膜片厚度的增加可减缓高压阶段流量随压力增长而下降的趋势,有利于灌水器在高压工况下保持流量稳定。研究为压力补偿灌水器的设计和优化提供了参考。     

渗灌材料制备及导水性能分析

该文旨在确定渗灌渗水涂层成分的配比方案,制备出渗水性能良好的渗灌滴头。通过对所选用的蒙脱土MMT及聚丙烯酰胺PAM材料的结构和性能进行了分析和比较,设计制备工艺,制备渗灌滴头,在实验室内搭建了渗灌材料的实际渗水的试验平台;采用拉伸强度试验对渗灌导水涂层材料与纤维结合性能进行研究,用电子显微镜对不同配比的渗灌导水材料的形貌进行了观察并对其微观结构和组成进行了分析,在不同环境条件下对渗灌材料的渗水自调节性进行分析。结果表明:PAM/MMT悬浮液的配比为0.20 g/50 m L(1∶250)时导水材料的成膜性较,涂层成膜性较好,分布较均匀。对于以1∶250聚丙烯酰胺和蒙脱石制备的的渗水材料,温度一定时,随着环境土壤含水率的逐渐增加,渗水速率逐渐降低,土壤含水率一定时,随着环境温度的增加,渗水速率逐渐下降。该研究为渗灌材料制备提供参考。     

根土系统中的根系水力提升研究综述

根土系统可看作是土壤-植物-大气连续体(SPAC)系统的子系统, 根土间存在着内在优化协调的动态机制以更大限度地为SPAC 过程提供水分和养分。植物根系的水力提升现象是根土系统对水分分异的根土环境中土壤水资源优化利用的过程, 是植物根系所具有的一种普遍现象。植物根系的水力提升作用利于植物对土壤水分利用最大化, 同时也促进了对土壤养分的吸收利用及对土壤环境的改善。可以从系统优化的观点对这一现象的存在进行理论解释, 其发生受一定的条件制约, 是必然中的偶然。根系水力提升量不容忽视, 在一些环境的植物中, 水力提升提供了很大比例的蒸腾水分, 不仅对植物蒸腾耗水有利, 更存在广泛的生理生态意义。研究根系提水的应用对干旱区农业发展和生态修复有着潜在的价值, 具有广泛的研究前景。     

梯形喉口无喉道量水槽设计及其水力性能模拟与试验

为了解决灌区普遍存在的通过增大水头损失来提高测流精度的问题,该文提出了一种具有梯形喉口的无喉道量水槽,并给出了量水槽参数与渠道尺寸的比例关系。该文在原型试验基础上,通过Flow-3D软件对过槽水流进行了数值模拟,分析了测流过程中水流流态、纵向时均流速分布、水头损失、湍动耗散沿程变化以及测流精度。研究结果表明:纵向时均流速分布和水流流态的模拟值与实测值最大相对误差均不超过10%,其模拟结果与实测结果较为吻和;基于临界流原理和能量守恒推出的水位流量关系式,进一步回归分析得到测流公式,其计算值与实测值最大相对误差为9.21%,满足量水精度要求;水头损失随着流量增大而增大,当流量大于45 L/s时,增大趋势明显变缓;最大水头损失不超过上游总水头10%,相比长喉道、巴歇尔、抛物线形量水槽水头损失较小。该研究可为灌区渠道量水设施设计提供参考。     

拖拉机线控液压转向系统设计及样车性能试验

拖拉机的转向系统是保证行驶安全、高效作业的关键机构,针对传统的全液压转向系统在转向过程中易发生转向沉重,甚至失灵等状况,该文提出一种拖拉机线控液压转向系统。论文首先对拖拉机线控液压转向系统进行总体设计,基于MATLAB软件的Simulink/Simhydraulic模块对线控液压转向系统进行动态建模和仿真分析,根据分析数据完成试验样车改装,利用改装样车分别进行转向系统的静态随机转动试验、蛇形试验、双纽线试验、稳态回转试验以及转向瞬态响应试验。通过试验分析得到线控液压转向系统在5个试验中理论与实际转向轮转角平均误差分别为1.58?,0.79?,1.09?,0.69?,0.47?。试验结果表明线控液压转向系统的理论与实际转角曲线吻合度更高,误差均低于全液压系统,转向误差精度有大幅度提高,性能更理想。拖拉机线控转向系统综合了液压和线控技术优点,在保证大动力输出的同时,又具有转向灵活,方便安装等特点,可为拖拉机线控转向系统推广应用提供参考。     

流道结构形式对滴头水力性能影响的试验研究

对滴灌系统的滴头进行试验研究表明,影响流态指数的主要因素是流道结构形式,包括流道齿形、齿角、齿距、齿高和流道的深度,流态指数基本不随滴头流道长度而变化.通过比较不同滴头流道的流态指数、流道长度及流道断面积,分析了其抗堵塞性能,并建立了描述滴头流量与流道长度及工作压力关系的回归模型.     

流道结构形式对滴头水力性能影响的试验研究

对滴灌系统的滴头进行试验研究表明，影响流态指数的主要因素是流道结构形式，包括流道齿形、齿角、齿距、齿高和流道的深度，流态指数基本不随滴头流道长度而变化。通过比较不同滴头流道的流态指数、流道长度及流道断面积，分析了其抗堵塞性能，并建立了描述滴头流量与流道长度及工作压力关系的回归模型。     

考虑配重的垂直摇臂式喷头摇臂运动规律及水力性能

为了研究摇臂运动规律及配重对喷头水力性能的影响,以垂直摇臂式喷头为研究对象,对垂直摇臂式喷头摇臂的运动特征进行理论分析,推导出摇臂运动周期公式,并在公式中考虑了配重位置变化因素;采用高速摄影对Nelson SR100喷头的摇臂运动情况进行了试验研究,将得出的摇臂运动周期与计算结果进行对比,并通过改变配重安装位置来考察运动周期变化对喷头水力性能的影响。结果表明:通过高速摄影试验得到的摇臂运动周期与理论公式计算值吻合较好,相对误差基本在10%以内,验证了推导公式的正确性,针对理论公式的计算误差,根据试验结果对理论进行了修正,进一步提高了理论公式的计算精度,相对误差都在3%以内;增大喷头工作压力和前移配重安装位置均可使喷头的运动周期减小。配重位置距摇臂旋转轴较近时,喷头近处的喷灌强度明显增加,3~10 m内的水量分布较配重在最远处时增加了40%左右;配重位置距摇臂旋转轴远时,喷头近处的喷灌强度随之降低,射程末端的喷灌强度随之增加。该研究可为垂直摇臂式喷头摇臂设计方法的建立和在喷头运行过程中能合理调节摇臂配重提供参考。     

长期施肥对土壤中硒的累积及其生物有效性的影响

Continuous applications of organic and inorganic fertilizers can affect soil and food quality with respect to selenium(Se) concentrations.A long-term(over 20 years) experimental field study,started in 1989,was conducted to investigate the changes in soil Se fractions and its uptake by crops,as affected by different fertilizer practices,in the North China Plain with an annual crop rotation of winter wheat and summer maize.The long-term experiment was arranged in a complete randomized block design consisting of 4replications with 7 fertilizer treatments:1) organic compost(OC),2) half organic compost plus half N-P-K chemical fertilizers(OC+ NPK),3) N-P-K fertilizers(NPK),4) N-P fertilizers(NP),5) P-K fertilizers(PK),6) N-K fertilizers(NK),and 7) an un-amended control.Soil samples from the surface(20 cm) were collected in 1989,1994,1999,2004 and 2009 to characterize Se and other soil properties.In 2009,the average soil Se concentrations in the treatments(149 ± 8 μg kg~(-1)) were higher than those in the soil samples collected in 1989 at the beginning of the experiment(112 ± 4 μg kg~(-1)),and decreased in the order of OC OC + NPK NPK≈NP PK ≈NK control.Sequential extraction showed the oxidizable fraction(50.06%± 3.94%) was the dominant form of Se in the soil,followed by the residual fraction(24.12%± 2.89%),exchangeable fraction(15.09%± 4.34%) and Fe-Mn oxides fraction(10.73%± 4.04%).With an increase of soil K,the exchangeable Se concentrations in the soil increased.The Se concentrations in the soil tillage layer(0-20 cm) were mainly related to soil organic carbon(SOC),although different contributions came from atmospheric deposition,irrigation and fertilizers.With the accumulation of SOC,the uptakes of soil Se by two crops were inhibited.For the OC and OC + NPK treatments,Se concentrations in wheat grains were lower than the critical standard of Se in stable food(100 μg kg~(-1)).Additionally,Se concentrations in grains were also decreased by the deficiencies of major soil nutrients,especially P.     

射流撞击式低压喷头设计与水力性能试验

为分散喷头主射流,提高喷头的喷洒均匀度,使喷头适用于农业低压喷灌,该研究结合射流与撞击流提出了一种射流撞击式旋转喷头。首先对比了射流撞击喷头与射流不撞击喷头的水力性能,通过正交试验分析了各结构参数值对射程和组合均匀系数的影响,得到副喷嘴结构优化参数,最后将优化后的射流撞击喷头与改进前的传统15PY2喷头进行水力性能及水滴粒径分布对比。研究结果表明,射流撞击使射程末端水量高点降低,同时射程得到提升,射程平均提升4.39%,在相同压力及组合间距下覆盖范围更大。影响喷头工作性能的结构参数依次为副喷管长度、副喷嘴进口锥角、副喷管内径、副喷嘴仰角,而副喷嘴仰角对射程与组合均匀系数影响最大,15型射流撞击喷头最佳结构参数组合为：副喷管长度20 mm、副喷嘴进口锥角55°、副喷管内径6 mm、副喷嘴仰角33°。射流撞击喷头在压力150～300 kPa下组合均匀系数和综合评分均高过传统15PY2喷头,组合均匀系数平均提升4.84%,综合性能平均提升4%,证明了射流撞击应用于旋转式喷头具有优势。在射程前中段,150和250 kPa下射流撞击喷头水滴直径更大;在射程后段,150 kPa下射流撞击喷头水滴直径更大,但在250 kPa下水滴直径更小。研究所得到的喷头结构及结论可为后续研究射流撞击对水力性能的影响提供参考。     

叠片过滤器水力和过滤性能综合评价方法研究

为建立叠片过滤器过滤性能综合评价方法,以5种常见叠片过滤器为研究对象,对不同进水含沙量(0.02%、0.03%和0.04%)与过滤流量(25、30、35 m3/h)条件下叠片过滤器的水力性能和过滤性能开展试验研究。根据不同工况下叠片过滤器的堵塞均匀度、周期拦沙量以及拦截泥沙中值粒径,采用逐步回归分析、主成分分析方法,建立不同单项性能指标与6项叠片结构参数(叠片厚度、叠片片数、叠片沟槽长度、叠片沟槽数、叠片沟槽外截面三角形顶角、叠片沟槽外截面三角形高)间的多元线性回归方程,并采用直接加权法建立叠片过滤器性能的综合评价函数。结果表明,叠片结构尺寸参数均对过滤器性能有一定的影响,所建立的评价函数对叠片过滤器I～V的评价值依次为7.22、7.08、7.88、8.63以及3.11,该评价函数可以全面、合理地对叠片过滤器综合性能进行评价和对比。该评价方法不仅能用于对叠片过滤器性能进行评测,还能为改进叠片结构尺寸、进一步优化过滤器性能提供参考。     

三种水力驱动比例式施肥泵吸肥性能试验

为保障微灌系统首部施肥装置选型的合理性,通过试验研究比较了3种类型水力驱动比例式施肥泵的吸肥性能,分析了影响施肥泵入口流量和吸肥量的因素。结果表明：入口流量受施肥管道两端压差影响,但受进口压力影响不大。建立了各施肥泵入口流量的回归模型,比较得出：3种施肥泵入口流量与压差关系分别符合幂函数、对数函数和二次函数关系,这主要是因为施肥泵最小工作压差和不同压差下运行性能的差异;施肥泵吸肥量受入口流量和压差影响。高压、大流量的运行工况会影响施肥泵施肥效果,施肥泵工作时入口流量最好不要超过设计流量,施肥比例较小时入口流量更不能过大。在分析吸肥量影响因素的基础上,建立了施肥泵吸肥量的回归模型,可用于吸肥量的估算;同时,研究发现3种施肥泵基本按照所设施肥比例施肥,但稍有差异、精度不一。     

Ergonomic evaluation of winegrape trellis systems pruning operation

The winegrape industry suffers from high incidence rates of work-related musculoskeletal disorders. Pruning of dormant vines is a significant task, requiring long periods of highly repetitive and physically demanding work. The purpose of this study is to quantitatively evaluate five commonly used winegrape trellis systems with regard to the risk of developing musculoskeletal injuries to the wrist and lower back while pruning. Eleven subjects participated in this study. Subjects performed a simulated pruning task as wrist and trunk postures were gathered using electrogoniometers. The results showed significant postural differences among the trellis systems. Compared to the other systems, the VSP was determined to be the optimal system in terms of decreasing relative MSD risk. These results will assist vineyards in the selection process of suitable trellis systems that will include the worker health aspect in conjunction with other trellis-related parameters such as grape quality and productivity.     

沙粒粒径对水力机械材料磨蚀性能的影响

对于运行于多泥沙河流的水力机械而言磨蚀问题不可避免,磨蚀会造成水力机械过流部件失重、变形,带来效率下降、维护成本增加等问题。目前针对磨蚀破坏机理的研究尚不完善,该文利用旋转喷射磨蚀试验装置对4种水力机械常用材料进行5种不同沙粒粒径下的磨蚀试验,借助扫描电镜及激光共聚焦扫描电镜对试件磨蚀表面进行二维和三维形貌观察,探究沙粒粒径对水力机械材料磨蚀破坏失效行为的影响规律及作用机理。结果表明:沙粒粒径为0.043、0.147及0.248mm时,试件磨蚀累计质量损失与时间呈线性相关,而粒径为0.349与0.449mm时质量损失与时间满足Gauss函数关系;沙粒粒径会影响试件的磨蚀特征,粒径为0.043 mm时试件表面磨蚀破坏主要为沙粒的垂直冲击磨损与空蚀,无明显水平方向的切削磨损,粒径为0.147、0.248、0.349及0.449mm时试件表面的磨蚀破坏以水平方向的切削磨损和空蚀破坏联合为主,并伴有一定量的垂直冲击磨损;通过分析4种材料的磨蚀特征,发现磨蚀质量损失与粒径大小二者之间存在强相关区与弱相关区的关系。该研究可为合理控制水力机械过流粒径大小及制定抗磨措施提供参考。     

仿自然鱼道水力及过鱼性能物理模型试验

仿自然鱼道是具有一定自然特征的过鱼设施,适用于中低水头工程,是目前鱼道形式研究热点之一。为了获得一种具有综合生态功能的鱼道,该文提出了一种利用芦苇模块构建的植物型鱼道,并通过物理模型试验对其水力特性和过鱼性能进行了研究。结果表明:选取芦苇为基本单元构建植物型鱼道是合适的。植物模块交错布置的植物鱼道内可形成蜿蜒的水流,流态丰富,过鱼通道内流速均小于1.1 m/s,满足过鱼要求。过鱼试验表明,过鱼对象可以在该鱼道内顺利上溯,植物模块下游侧可形成低流速的鱼类休息区,验证了鱼道体型的合理性。该文提出的植物型鱼道丰富了鱼道的形式,具有一定创新性,对今后类似鱼道的设计和建设具有一定的指导意义。     

低速大扭矩水压马达的配流性能分析及试验

为了提高低速大扭矩水压马达的容积效率,以马达的配流副为研究对象,基于力平衡方程及流量方程,建立了配流体端面与转子端面间的泄漏流量损失和功率损失的数学模型。以配流体转子间的水膜厚度、介质温度和马达转速等为性能指标,分析了不同供流方式下间隙、温度和转速对其性能的影响。研究结果表明:间隙越大,配流体转子端面的泄漏流量损失和功率损失越大,温度越高,功率损失越大,同时内环供流时水压马达的性能要优于外环供流。因此,减小水膜厚度,降低水温,可减小配流副的泄漏流量损失和功率损失,提高水压马达的容积效率及马达性能。综合考虑,配流间隙控制在4~5μm较为合适,水温控制在室温(20±5)℃状态下为宜。同时基于上述研究,设计加工出低速大扭矩水压马达物理样机,并对样机的性能进行了加载试验测试,得到了相应的性能曲线,试验结果表明:加工完成的水压马达样机在带载时的容积效率最高可达到90.97%,机械效率最高可达到93.59%,从而验证了所研制的低速大扭矩水压马达原理正确可行,也证明了上述研究结果的正确性,解决了低速大扭矩水压马达的设计理论及关键技术问题。该研究为低速大扭矩水压马达进一步的产品化提供了参考。     

长期施磷稻田土壤磷素累积及其潜在环境风险

应用常规化学分析法和数学统计方法,基于太湖地区13年的长期定位试验,研究长期不同施磷水平下[0(不施磷)、30 kg.hm 2.a 1(低磷)、60 kg.hm 2.a 1(适磷)、90 kg.hm 2.a 1(高磷)]稻麦轮作系统稻田土壤磷素累积规律及磷素流失引发的环境风险。在本试验区土壤环境条件下,可能发生稻田磷素淋溶及径流的土壤耕层(0~15 cm)Olsen-P临界值分别为26.0 mg.kg 1和24.8 mg.kg 1。连续13年适磷、高磷施肥,土壤耕层Olsen-P含量分别达到26.9 mg.kg 1和33.2 mg.kg 1,均高于临界值浓度,且已导致稻田田面水与30 cm渗漏水中总磷浓度显著升高,大大提高了稻田磷素淋溶及径流的风险。低磷施肥土壤Olsen-P长期稳定在(10.1±2.0)mg.kg 1水平,并且每年的稻麦产量与高磷、适磷处理相比并无显著差异,而长期低磷施肥土壤磷的流失风险也较小。因此,在太湖地区稻麦轮作体系下,磷肥不宜以常规适磷水平长期施用,建议以低磷水平(30 kg.hm 2.a 1)长期施用或以适磷水平(60 kg.hm 2.a 1)间歇式施用。