春季土壤墒情变化与气象条件相关性分析

从农业气象情报服务需求出发,根据近3年土壤墒情实时变化资料和定期测墒数据,分析研究与土壤墒情变化高相关的气象因子。结果表明,通过现有观测资料,可以定量评估局地土壤墒情变化,为预测春旱趋势和程度提供可靠的依据。     

干燥过程中木材温度的变化规律以及与含水率关系的研究

通过对高温和常规温度干燥过程中木材温度及含水率变化与分布的测定,研究木材温度变化的特点和木材温度与含水率的变化关系。分析自由水蒸发面移动、水分状态改变对温度变化的影响。在此基础上,探讨利用木材温度控制干燥过程的可能性和实施方法,     

地膜覆盖栽培甜菜土壤水分状况及节水灌溉方案

在分析地膜甜菜需水量与需水规律试验资料的基础上，探讨了甜菜土壤水分变化规律及各生育时段的需水规律，确定出不同气候类型甜菜一次适宜灌溉定额。根据试验求算实际蒸散量，利用彭曼公式及土壤水分平衡方程，计算求得甜菜各生育阶段的作物需水系数及不同气候年型甜菜全生育期的适宜灌溉定额及最佳节水灌溉方案。     

耕层土壤含水量消长规律的分析

利用濉溪县耕层土壤含水量和同期观测的降水量、蒸发量资料,研究表明:耕层土壤含水量的消长与基期土壤含水量、期间降水量和蒸发量呈多元直线相关关系,其中耕层土壤含水量增加量主要取决于基期土壤含水量和降水量;土壤含水量减少量主要取决于蒸发量和基期土壤含水量。耕层土壤相对含水量在50%~65%,需降水或补充灌溉22.9~49.3 mm的水量。降水效力与基期土壤含水量、降水量呈多元指数曲线关系,蒸发效力与基期土壤含水量呈指数曲线关系。耕层土壤含水量的消退呈"快—缓慢—滞缓"的变化过程。使耕层相对含水量达到80%以上的一次降水(过程)过后,连续11.2~47.1 d无降水,耕层相对含水量尚可维持在60%以上。     

华北高寒区不同潜水位萝卜田耗水特性与覆膜效应研究

 针对华北高寒区蔬菜雨养旱作生产,通过定位观测试验,研究了不同潜水位水平及其地膜覆盖的萝卜田耗水量与耗水组成,菜田耗水的时空特征及覆膜的水分产量效应。结果表明,3 m以下潜水对菜田耗水极少贡献;2 m与1 m潜水位菜田潜蒸水可有25.79 mm与71.78 mm,对萝卜旱作生产具重要作用。萝卜田生育期平均耗水强度2.94 ～3.41 mm·d-1 ,30～60 cm土层是主要供水层次。覆膜萝卜田,较裸地水分蒸失减少15.51～39.19 mm,水分利用效率提高40.00%～81.70%。地膜在萝卜生育期间"前保后供"的土体水分调节效应,成为旱区农作水分时序高效利用的重要机制。     

Soil Management Systems Improve Water Use Efficiency of Rainfed Rice in the Semi-Arid Tropics of Southern Lombok,Eastern Indonesia

Abstract

Rice (Oryza sativa) grown on rainfed Vertisols in the semi-arid tropics of southern Lombok, Eastern Indonesia, is usually flooded in the short wet season, creating a considerable demand for water. However, rice crops and secondary crops frequently suffer from water stress as the soil dries after the wet season. Four systems of soil management for rice were studied at Wakan and Kawo, with average annual rainfalls of 984 mm and 1665 mm respectively. The objective was to improve water use efficiency (grain yield/m³ water consumed). The four systems were unflooded permanent raised beds with tillage (RMT) or without tillage (RNT), and flooded flat land with tillage (FMT, the conventional system, gogorancah), or without tillage (FNT). Water was kept at 0.1 m depth in the furrows (RMT, RNT) or at 0.05 m depth on flat land (FMT, FNT). Excess water was collected in a dam (embung), and used when necessary to keep the water at the desired depth. Compared with FMT, RNT reduced crop water requirement for rice by 50% at Wakan and by 44% at Kawo. Water use efficiency in RNT was increased by 90% at Wakan, and by 56% at Kawo, compared with that in FMT. There were no differences between treatments in the yield of rice at Kawo (4.5 t/ha), but at Wakan yield was better in FMT or FNT (4.2 t/ha) than RMT or RNT (2.8 t/ha). Hence, on rainfed Vertisols of Southern Lombok, rice grown on permanent raised beds, with or without tillage, could successfully replace rice grown under the conventional flooded system with tillage on flat land (gogorancah), where the rainfall is higher. The extra water saved with permanent raised beds could be used to irrigate secondary crops.     

A novel technique for drying soil samples

Abstract

Evaporation rates and drying times of soil samples exposed to high fluxes of unipolar air ions of either polarity, produced by corona electrodes, were studied with a beta‐ray gauge. Ion‐treated soils dried more than three times faster than the control samples under the same laboratory conditions. An analysis of the experimental curves on Rideau clay showed evaporation rates of 2.96 x 10^‐4and 8.84 x 10^‐4g cm^‐2min^‐1for control and treated samples, respectively, when exposed to 4.39 x 10¹²negative air ions cm^‐2s^‐1. An objective criterion was defined for a state of soil dryness when the sample acquired a steady‐state value of transmission of beta particles with time. Electric wind caused by the ionic drag is proposed as the principal driving force for the enhancement of evaporation rates from soil samples used.     

基于SPEI和MI分析陕西省干旱特征及趋势变化

【目的】目前干旱研究多为基于历史干旱事件分析成因与变化趋势,而结合过去与未来长时间序列数据更能揭示干旱变化特点。寻找在基于CMIP5模型输出未来气象数据时模拟干旱指数方法并探究陕西省过去与未来干旱变化特点,为陕西省未来农业水资源管理提供依据。【方法】根据陕西省18个气象站历史数据以及CMIP5模式输出未来气象数据,比较了3种模型模拟参考作物蒸发蒸腾量（ET₀）,并基于参考作物蒸发蒸腾量（ET₀）和降水数据计算标准降水蒸发指数（SPEI）和相对湿润指数（MI）反映干旱程度,比较过去（1958—2018年）与未来（2019—2100年）干旱的时空变化特点。【结果】多元线性回归模型（Multiple Linear Regression, MLR）能较准确的模拟参考作物蒸发蒸腾量（ET₀）（RMSE=0.457 mm·d ^-1）;在RCP2.6和RCP8.5情景下未来干旱指数呈现上升趋势,在RCP8.5情景下,21世纪40年代存在干旱指数的突变年份;陕西省未来干旱程度降低,年内干旱分布更加不均匀;未来时期夏玉米生长季干旱程度减小,冬小麦生长季干旱程度增加。【结论】在不同RCP情景下,未来干旱变化特征存在差异,相同RCP情景下,SPEI和MI反映的干旱特征变化基本一致,但部分时段存在变化差异。为有效应对气候变化对旱作作物产量造成的负面影响,应当增强土壤蓄水保墒能力,尤其加强冬小麦生长季的抗旱工作。     

建昌地区气候变化对蒸发皿蒸发量的影响

采用建昌气象站1960-2014年蒸发皿蒸发量资料,运用相关分析等气候统计诊断分析方法,研究了该地区蒸发量变化特征和主要影响因子,为区域性水平衡研究提供技术支撑。结果表明:建昌地区蒸发量减少趋势明显,气候倾向率为-49.28mm/10a,年蒸发量减少15.2%;地面平均温度、日照时数和风速是影响蒸发皿蒸发量的主要因子;模拟预测蒸发量模式准确率为87.3%。研究成果可为地方水循环水平衡研究提供依据和参考。     

1983～2013年洛宁县蒸发量变化特征及原因分析

利用洛宁县1983 ～2013年小型蒸发皿蒸发量资料,采用气候倾向率及相关分析方法,对蒸发量的年、季、月变化趋势、变化特征等气候变化进行了比较全面的分析.结果表明,近31年洛宁县蒸发量呈总体下降趋势,其中秋季蒸发量的减少对全年蒸发量的下降影响最大;不同季节蒸发皿蒸发量变化趋势不同;影响蒸发量的主要气候因子是云量、日照、风速,其中蒸发量与日照、风速呈正相关,与云量呈负相关.