Soil Properties Degradation Assessment Using Infrared Scanning Technique of Soils （Case Study： Eastern of Congo）

Recently, near infrared reflectance （NIR） and mid-infrared （MIR） spectroscopy techniques are increasingly introduced as convenient and simple non-destructive techniques for quantifying several soil properties. This study uses MIR method to predict pH, soil organic C, total N, AI, Ca, Mg and K, CEC and soil texture for soil samples collected in Sud-Kivu, Congo. A total of 536 composite soil samples were taken from two locations （Burhale and Luhihi） at two depths （0-20 cm and 20-40 cm） using a spatially-stratified random sampling design within an area of 200 km2. Differences in characteristics were evaluated between the two locations, land use （cultivated vs. non-cultivated land） with soil depths. A random subset of the samples （10%） were analyzed using standard wet chemistry methods, and calibration models developed by MIR data to estimate soil properties for the full soil sample set. Partial least squares regression （PLS） method gave acceptable coefficients of determination between 0.71 and 0.93 for all parameters. Soil organic matter levels were higher in cultivated plots in Luhihi （3.9% C） than in Burhale （3.0% C）, suggesting lower levels of soil fertility in the later area. This indicates high levels of acidity, which are likely to limit crop production in the area. Phosphorus deficiency is acute in Burhale （2.4 mg P/kg） but less in Luhihi （5.4 mg P/kg）. In both locations, low levels of Ca and Mg indicate that soils may be susceptible to deficiencies in both elements.These findings provide new opportunities for monitoring soil quality in the region which can benefit multiple actors and scientists involved in the agricultural and environmental sectors.     

双掺大流动性混凝土性能研究

研究了不同粉煤灰掺量对双掺大流动性混凝土性能的影响,并结合高效减水剂及粉煤灰的水化机理及混凝土抗压强度、碳化深度对双掺大流动性混凝土作了一定的性能分析论述,总结出其抗压强度及碳化深度之间存在的关系。     

两种模型分析方法下冬小麦根系吸水深度的对比研究

为了研究冬小麦根系吸水深度,应用塑料管土柱法在田间进行冬小麦种植试验,测定了冬小麦越冬期、拔节期、抽穗期、灌浆期和成熟期不同土层深度土壤水稳定同位素值,并应用耦合模型和IsoSource多元线性模型对比分析了水源贡献率。结果表明,冬小麦在越冬期、返青期主要利用0~20 cm土层的土壤水,拔节期主要吸水深度为0~40 cm;抽穗期,基于耦合模型的主要吸水深度为0~40 cm,基于IsoSource多元线性模型的为0~40 cm和80~180 cm;灌浆期,基于耦合模型和IsoSource多元线性模型的主要不同吸水深度为180~200 cm,且基于耦合模型的该层贡献率明显高于IsoSource多元线性模型;成熟期主要利用0~40 cm和80~100 cm土层的土壤水,基于2种模型的分析结果相同。应用耦合模型求解贡献率,当分组较多且组间水稳定同位素差异较小时,应结合其他方法来保证其准确性。     

基于IL-HMMs预测模型的地下水埋深预测研究

以西北干旱典型县域磴口县为研究区,基于增量学习的改进隐马尔可夫预测模型(IL-HMMs),对区域地下水埋深进行了预测研究。为检验IL-HMMs模型预测效果,将模型预测结果与2013年长观井的实测数据进行了比较;同时为检验模型的优劣性,与未经增量学习的隐马尔可夫模型(HMMs)、加权马尔可夫链(WMCP)和BP神经网络(BP neural network,BPNN)预测模型的预测结果进行了比较。结果表明:与其他几种预测模型相比,IL-HMMs模型预测精度显著提高,误差更小,有较好的鲁棒性。并使用IL-HMMs模型对2018年地下水埋深进行了预测,预测结果表明,2018年地下水年平均埋深略有增加、局部区域地下水埋深增量加剧。基于IL-HMMs模型的地下水埋深预测具有很好稳定性的同时对新数据加入又有很好的鲁棒性,可为地下水埋深动态预测提供思路与方法补充,为区域地下水资源开发利用和保护提供重要依据。     

土壤耕层深度和施肥深度对桔梗根部主要农艺性状的影响

[目的]探索优质高产的桔梗栽培方法。[方法]在15、20、30、40cm的耕深和不施肥、全层施肥、深层施肥（30～40cm）的3个施肥深度条件下,调查桔梗根的主要农艺性状。[结果]在耕深试验中,30cm耕深条件下的主根长最长、根粗最粗、单根鲜重最重,但侧根数也最多;施肥效果为深层施肥的效果好于全层施肥和不施肥。[结论]试验结果对山区、半山区桔梗栽培体系的建立有一定的参考价值。     

鄂尔多斯高原地下水浅埋区植被与地下水埋深关系

采用植被样方实地调查结合浅井揭露地下水埋深的方法,建立鄂尔多斯高原苏贝淖周边滩地植被群落总盖度、单物种盖度及物种空间演替与地下水埋深的定量关系。研究表明,群落总盖度与水位埋深在1.6m内有明显相关关系;苔草、碱蓬、芦苇、马兰和芨芨草等低湿地物种存在适生水位,分别为0.4m、0.6m、0.8m、0.8m和1.6m;物种演替与水位埋深关系表明,水位埋深小于0.6m地带,为湿生、盐生植被优势区;大于3.2m地带为旱生、沙生植被优势区。同时,1.6m为生态交错带临界水位,该区域湿生、中生、旱生和沙生等植被类型均有分布,物种数量最多,物种多样性最大。不同水位埋深下的植被分布和演替规律可为预测地下水开发后植被变化演替提供重要科学依据。     

Responses of root growth of Alhagi sparsifolia Shap. (Fabaceae) to different simulated groundwater depths in the southern fringe of the Taklimakan Desert,China

Alhagi sparsifolia Shap. (Fabaceae) is a spiny, perennial herb. The species grows in the salinized, arid regions in North China. This study investigated the response characteristics of the root growth and the distribution of one-year-old A. sparsifolia seedlings to different groundwater depths in controlled plots. The ecological adaptability of the root systems of A. sparsifolia seedlings was examined using the artificial digging method. Results showed that: (1) A. sparsifolia seedlings adapted to an increase in groundwater depth mainly through increasing the penetration depth and growth rate of vertical roots. The vertical roots grew rapidly when soil moisture content reached 3%-9%, but slowly when soil moisture content was 13%-20%. The vertical roots stopped growing when soil moisture content reached 30% (the critical soil moisture point). (2) The morphological plasticity of roots is an important strategy used by A. sparsifolia seedlings to obtain water and adapt to dry soil conditions. When the groundwater table was shallow, horizontal roots quickly expanded and tillering increased in order to compete for light resources, whereas when the groundwater table was deeper, vertical roots developed quickly to exploit space in the deeper soil layers. (3) The decrease in groundwater depth was probably responsible for the root distribution in the shallow soil layers. Root biomass and surface area both decreased with soil depth. One strategy of A. sparsifolia seedlings in dealing with the increase in groundwater depth is to increase root biomass in the deep soil layers. The relationship between the root growth/distribution of A. sparsifolia and the depth of groundwater table can be used as guidance for harvesting A. sparsifolia biomass and managing water resources for forage grasses. It is also of ecological significance as it reveals how desert plants adapt to arid environments.     

油菜秸秆还田腐解变化特征及其培肥土壤的作用

为促进油菜秸秆腐解,推进农村作物秸秆的资源化利用,减少秸秆焚烧对环境的负面影响,培养与提高土壤肥力,采用尼龙网袋和田间试验相结合方法,设置了油菜秸秆不同还田量处理和不同还田深度处理,研究了油菜秸秆腐解百分率和腐解速率变化特征,分析了油菜秸秆还田对土壤性质及作物产量的影响。结果表明,油菜秸秆还田的腐解百分率随时间延长而逐渐增大,秸秆腐解速率则早期快后期慢;随秸秆还田量增加,腐解速率降低,表现为全量还田的秸秆腐解速率<2/3量还田秸秆腐解速率<1/2量还田秸秆腐解速率<1/3量还田秸秆腐解速率;在种植水稻条件下油菜秸秆还田深度在10 cm时腐解速度最慢,在表层还田腐解速度最快,20 cm深还田腐解速度居中。相比对照处理来说,油菜秸秆还田降低了土壤容重,增加了土壤有机质含量,一定程度上提高了土壤氮磷钾含量(P<0.05)。油菜秸秆还田对水稻作物有极显著增产作用(P<0.01),增产幅度在6.02%～21.17%之间。本试验对水稻油菜轮作体系下油菜秸秆还田腐解特征进行的研究可为调控油菜秸秆还田腐解速度,改善农业生态环境提供参数依据。     

近滨海盐碱地暗管排水条件下地下水埋深动态变化模拟

农田暗管排水工程是近滨海地区盐碱地防御涝渍害、降低土壤盐分和促进作物生长的重要措施。本文应用DRAINMOD模型对河北沧州近滨海暗管排水排盐试验区(暗管埋深1.2 m,间距30 m),2011年6—9月的地下水埋深进行了模拟,并对不同控制性排水方案(无强制排水,地下水埋深控制在50 cm、80 cm和100 cm)下地下水埋深的变化进行了预测。模型所需参数(气象数据、作物数据、土壤参数和排水数据)由室内试验、田间试验和实地观测得到。研究结果表明:DRAINMOD在该地区的模拟值与观测值拟合较好,效率系数为0.67,相对误差系数为6.15%,反映出模型良好的模拟性能;农田暗管排水系统能明显降低涝渍害的发生,即使发生强降水,也能在2 d内将地下水埋深控制在60 cm以下,而若无强制排水地下水埋深需在15 d后降至60 cm;对不同排水方案模拟效果的比较表明,试验区在夏季控制性排水中,将地下水埋深控制在80 cm左右较为合适。综上,DRAINMOD模型可以很好地应用于地下水埋深变化的预测中。因此,在未来的研究中,近滨海盐碱区可以通过DRAINMOD模型模拟地下水埋深变化,从而为农田排水系统的设计提供理论依据,为暗管排水管理制度的建立提供科学的选择方法。