Airborne Videography to Identify Spatial Plant Growth Variability for Grain Sorghum

Much research has focused on the use of intensive grid soil sampling and yield monitors to identify within-field spatial variability in precision farming. This paper reports on the use of airborne videography to identify spatial plant growth patterns for grain sorghum. Color-infrared (CIR) digital video images were acquired from two grain sorghum fields in south Texas several times during the 1995 and 1996 growing seasons. The video images were registered, and classified into several zones of homogeneous spectral response using an unsupervised classification procedure. Ground truthing was performed upon a limited number of sites within each zone to determine plant density, plant height, leaf area index, biomass, and grain yield. Results from both years showed that the digital video imagery identified within-field plant growth variability and that classification maps effectively differentiated grain production levels and growth conditions within the two fields. A temporal comparison of the images and classification maps indicated that plant growth patterns differed somewhat between the two successive growing seasons, though areas exhibiting consistently high or low yield were identified within each field.     

湖北省粮食主产区土壤养分的空间变异性研究

利用"网格"取样、土壤养分状况系统研究法和GIS技术探讨了湖北省粮食主产区3个自然村土壤养分的空间变异特性.结果表明,pH值和有机质相对稳定,在整个研究区域其变异较小,近似于正态分布,施肥元素的变异则较大,表现出明显的负偏峰分布特征;土壤有效P、K和Zn等重要施肥元素的空间变异主要是受土壤利用方式和施肥水平等随机因素的影响,同时其缺乏又更多地出现在水田中.     

黑龙江省双城市土壤有机质和速效养分的空间变异特征

采用地理信息系统(G IS)和地统计学相结合的方法研究了黑龙江省双城市土壤表层(0~20 cm)有机质、速效氮、速效磷、速效钾这4种土壤养分指标的空间变异性。结果表明:土壤有机质、速效氮、速效钾的理论模型均为球状模型;速效磷的理论模型为指数模型。速效钾含量的C0/(C0 C)为49.96%,存在中等的空间相关性,说明其空间变异是由随机性因素和结构性因素共同作用的结果;速效氮、有机质、速效磷含量的C0/(C0 C)变化范围是8.10%~14.39%,均表现出强的空间相关性,说明其空间变异均受结构性因素的影响。从总体分布趋势来看,4项养分指标均呈现出由西向东、由西南向东北升高的趋势。     

Spatial Variability of Irrigated Corn Yield in Relation to Field Topography and Soil Chemical Characteristics

Corn yield, topography and soil characteristics were sampled on a 26 ha area of a centre pivot irrigated cropland. The aim of the study was to determine relationships between corn yield, field topography and soil characteristics. The study was carried out in the Alentejo region of Portugal. Corn yield was measured with a combine harvester fitted with a grain-flow sensor and positioned by means of the Global Positioning System (GPS). A grid-based digital elevation model (DEM) with 1-m resolution was constructed and several topographic attributes were calculated from the DEM: the local slope gradient (S), profile curvature (Curv), specific catchments area (SCa), and a steady-state wetness index (W). Yield and topographical attributes were computed for areas of radius 5, 10, 25 and 50 m, being considered its maximum, minimum, range and average values. The soil was systematically sampled with a mechanical probe for a total of 109 soil profiles used for analysis of the following soil superficial (<0.30 m) characteristics: extractable phosphorous (P₂O₅) and extractable potassium (K₂O), soil pH, cation exchange capacity (CEC) and exchangeable bases. With centre pivot irrigation systems, the Wave₅₀ index was shown to be useful for the identification of field areas in which low corn yields may be due to lack of water. At the same time, SCa was found to be useful for the identification of field areas in which low yields are due to excess water and drainage problems. Higher positive correlation between pH, Ca and Curv were observed; calcium concentration was found on the transition areas between flat surfaces to concave ones, while lower values were detected in convex and concave areas. Topographical indexes, namely Wave₅₀, SCa and Curv, can be especially helpful in site-specific management for delineating areas where crop yields are more sensitive to extreme water conditions.     

广西桂林不同植被覆盖下土壤含水量空间变异性研究

以桂林市农业科学院的大豆地、梨树地、甘蔗地为例,分析3个试验区土壤表层0~6cm土壤含水量变化规律以及空间分布特征。结果表明:降雨是影响土壤表层土壤含水量变化的关键因子,耕作方式也在一定程度上影响土壤含水量变化,梨树地土壤含水量是三者之中最高,甘蔗地土壤含水量次之,大豆地土壤含水量最小;3个试验区在3种不同土壤水分状态下的土壤含水量空间分布属于中等程度的空间相关性,受降雨因素和人为因素共同制约,在不同条件下他们各自占有的权重不同;尽管不同的植被覆盖条件以及人为因素干扰会影响土壤含水量空间分布,但是土壤含水量较高的区域相对稳定,表明土壤本身具有恢复其空间分布稳定性能力。     

滴灌条件下核桃土壤水分时间变异性分析

利用地统计学方法,研究了核桃在滴灌条件下田间土壤水分的时间异质性规律,以便为核桃滴灌自动化灌溉系统中的墒情预测提供理论依据。结果表明,在不同的时间尺度上,实验区土壤水分表现出不同程度的时间异质性,15 d尺度总的时间相关性程度远小于1 d尺度。1 d尺度基本可以揭示土壤水分时间上的微观变化结构特征,而15 d尺度不能全面揭示更微观变化的结构特征。     

成都郫县土壤氮素养分在城市化进程中的时空变异特征

利用抽样调查法和地统计学方法,在ArcGIS8.1地理信息系统平台上,对地处成都西郊的郫县耕层土壤1981年93个样点和2002年46个样点氮素含量的时空变异特征进行了研究。结果表明,2002年该县土壤全氮和碱解氮含量平均为1.61g/kg和159mg/kg,分别比1981年下降了8.45%和增加了16.99%。21年间由于受城市化进程的影响,全氮区域变化幅度呈由东向西逐渐减小的趋势;而碱解氮含量同时受施肥水平的影响,区域变化幅度为西部高于东部和中部;并且该县不同水稻土的全氮含量和碱解氮含量变化状况也不尽相同。     

两种植被覆盖度下土壤水分和盐分的空间变异性研究

[目的]裸地和植被覆盖地土壤剖面平均水盐含量的空间变异特征.[方法]应用统计学方法、聚类分析法和相关分析法,以奇台绿洲-荒漠交错带典型盐渍化地为研究区进行对比分析.[结果]裸地和植被地土壤水盐都服从正态分布,土壤盐分均属中等变异性,具有较强的空间自相关性.裸地土壤含水量属弱变异性,具有中等强度的空间自相关性;植被地属中等(偏弱)变异性,具有较强空间自相关性.裸地的相关距离仅是植被覆盖地的1/10左右.随着土层深度的增加,两者土壤盐分活跃程度变化依次为:活跃层、次活跃层和较稳定层.土壤水分的变化及其与盐分的关系则不一致,裸地是以受随机性因素影响较大的表层最为活跃,其与盐分的相关性也较差;而植被地是以中下层(60～80 cm)最为活跃,其与盐分呈极显著正相关性.[结论]由于随机性因素和结构性因素(如植被、微地形等)的影响,两种植被覆盖度下的土壤水盐的空间变异表现出明显的差异性;也反映出植被对土壤水盐分布及影响水盐分布的随机性因素均具有显著的作用力及反作用力.     

乌鲁木齐县蔬菜地土壤养分空间变异研究

以乌鲁木齐县蔬菜主产区的三个乡为例,采用GIS与地统计学相结合的方法对其耕层土壤(0～20 cm)的有机质、全氮、速效氮、速效磷、速效钾等5种养分要素的空间变异特征进行分析.结果表明:全氮变异函数曲线的理论模型能很好地符合球状模型;有机质、碱解氮、速效磷、速效钾的变异函数曲线则符合线性无基台模型.有机质、速效磷和速效钾具有很强的空间相关性,说明受母质、地形、土壤类型等自然的结构性因素影响较大;碱解氮具有中等的空间相关性,说明对施肥、作物、管理水平等随机因素引起的空间相关性起很大作用;全氮的空间相关性很弱,说明人为活动严重削弱了结构性因素造成强的自相关作用.