基于EM38的土壤剖面电导率预测研究

【目的】以海涂围垦区盐碱土为研究对象,利用EM38大地电导率仪在地表不同高度测量的土壤表征电导率预测土壤不同深度土层剖面的电导率。【方法】利用EM38电导率线性响应模型结合Tikhonov正则化能较好解决病态矩阵的线性反演问题。利用该方法来预测土壤剖面电导率,并对预测结果进行误差分析,最后通过偏差变化法增加噪声利用局部灵敏度分析法来评价模型的灵敏度。【结果】研究发现,土壤剖面平均电导率和地表不同高度平均表征电导率具有极显著相关性,能利用表征电导率较好的预测剖面平均盐分。线性模型不仅能较好的预测土壤剖面电导率的变化趋势,而且在数值上也能较好的预测电导率的大小,平均预测误差在40%左右。相对预测误差较大的土层,模型灵敏度越大,因此可通过提高EM38数据测量的稳定性来提高预测精度。【结论】利用EM38表征电导率采用线性模型结合Tikhonov正则化的方法能够较好的反演土壤剖面电导率,预测结果可以为样区土壤管理提供科学的决策依据。     

基于电磁感应仪的田间土壤盐渍度及其空间分布定量评估

 【目的】阐明黄河三角洲地区土壤盐渍化空间变异特征,探讨利用电磁感应仪定量评估田间土壤盐渍化的空间分布。【方法】运用电磁感应仪(EM38和EM31)及其移动测定系统,结合GIS和地统计学方法, 研究了该地区典型地块土壤盐分与磁感表观电导率间的响应关系,分析了表观电导率的空间变异特征,并对土壤盐分空间分布进行了定量评价。【结果】土壤表观电导率与盐分含量具有良好的相关性,采用EM38h＋EM31h的优化测定组合可以提高土壤盐分的解译精度;表观电导率EM38h、EM31h的空间变异结构都表现出复合的尺度效应,较好地符合球状套合模型;EM31h的空间自相关程度强于EM38h,短程变异是构成EM38h、EM31h空间异质性的最主要部分;结构性因素是主导土壤盐分空间分布格局的最直接因素,随机性因素是加快盐分分布格局形成的重要因素。由盐渍化分级可知：研究区总体属于重度盐化土类型,且呈现一定的盐分表聚趋势;各土层中几乎不存在非盐化土,盐土与重度盐化土是最主要的土壤类型。【结论】该研究结果为不同尺度(从农田到区域)土壤属性调查与质量评价提供参考依据,并为农业水土资源的高效利用提供指导。     

EM38在土壤盐渍化快速检测中的应用研究

以渭干河-库车河绿洲地区典型样区为研究对象,电磁感应仪EM38检测与田间采样相结合,针对其存在的土壤盐渍障碍问题,分析土壤电导率的剖面分布特征,建立磁感应表现电导率与土壤电导率之间的回归模型,并对运用电磁感应仪EM38划分土壤盐渍剖面类型进行探讨。结果表明:研究区表层土壤盐分具有较强的表聚性与变异强度,土壤电导率与磁感表观电导率呈极显著的相关关系,EMh对浅层土壤电导率的解译精度较高,而EMv对深层土壤电导率的解译精度要高于EMh。利用电磁感应仪EM38对研究区进行土壤盐渍剖面类型划分,表聚型与底聚型是研究区最主要的盐渍剖面类型。该结果对研究土壤盐渍化的发生机制、预测与评估该地区土壤盐渍化的发生发展具有重要参考意义。     

测土配方施肥在水稻生产上的应用研究

水稻是无为市主要的粮食作物之一.该研究通过测试土壤肥力以及水稻生产中所需的氮、磷、钾等元素,根据实际需求进行配方施肥统筹肥料、田间茎蘖动态调查、示范田块水稻产量以及肥料成本效益分析,确定配土测方施肥的实际效益.结果表明,实施测土配方施肥的田块比常规施肥的增产6.8％,增收755元/hm2,效果显著.     

水稻锌肥应用效果研究

在张家港市开展6组水稻不同用量锌肥试验。结果表明:增施锌肥能显著提高水稻产量,且对穗数、结实率、千粒重等产量构成要素均有显著效果。增产效果水稻土高于潮土、低有效锌含量田块高于高有效锌含量田块。锌肥适宜用量为22.50~30.00 kg/hm~2,水稻产量8 890~8 988 kg/hm~2,水稻效益7 282.5~7 589.0元/hm~2。     

2011-2019年江苏省水稻主产区规模连片水稻时空动态分析

选择农田防护林作为界定田块是否连片的标准,分析了水稻规模连片种植的时空格局及变化特征.结果表明,①2011-2019年,研究区内0.67×103 hm2以上规模连片水稻种植面积逐年减少.其中,6.67×103 hm2以上连片水稻种植面积平均减少7.38％,3.34×103～6.67×103 hm2连片水稻种植面积平均减少2.40％,0.67×103～3.33×103 hm2连片水稻种植面积平均减少0.76％.②位于洪泽县,东海县、灌云县、连云港城区交界处,东海县的大于6.67×103 hm2连片水稻种植面积持续保持稳定;位于淮安市楚州区,滨海县、射阳县、阜宁县交界处,盐城市盐都区的大于6.67×103 hm2水稻连片区从大到小或从有到无,变化幅度较大.③随着水稻规模连片区的缩小,连片区内水稻种植逐步单一化、水稻田块空间分布紧密度提高.本研究提出的用田块间间距来界定田块是否连片的方法,能够有效解决区域性农作物规模连片种植的量化问题.     

宝应县水稻精确施氮技术研究

宝应县水稻精确施氮技术研究结果表明,不同土壤肥力条件下水稻产量差异较大,高肥力田块精确施氮区产量最高,达9 173.25 kg/hm2,其产量构成也有相应的变化趋势,表现为精确施氮区最高,常规施肥区次之,无氮空白区最低。不同土壤肥力条件下,水稻对氮肥的吸收利用率,高肥力田块高于中肥力田块,中肥力田块高于低肥力田块,精确施氮区高于常规施肥区,又都高于无氮空白区。根据斯坦福公式计算出合理的施氮量,宝应地区适宜的施氮量为210~285 kg/hm2。     

2005年江苏里下河地区褐飞虱大发生的特点及其原因分析

兴化市地处江苏省里下河地区,2005年褐飞虱7(4)、8(5)代(7、8为全国划分代次,4、5为江苏划分代次,以下简称4代、5代)连续大发生,虫量之大、范围之广、危害之重,是10年以来所未见.据统计,全市9.33万hm2水稻,4、5代累计防治27.06hm2次,(其中4代平均防治1.8次,5代平均防治1.1次).经全力防治,大面积水稻危害损失控制在经济允许水平以下,产量损失在3%以下的田块,有7.2万hm2水稻(占水稻面积的77.2%),产量损失在3%～10%的田块,有14万hm2水稻(占水稻面积的15%),更有少数不用药田块产量损失高达20%～30%.     

不同田块类型垄作栽培对水稻农艺性状及产量的影响研究

本文首先介绍不同种类型田块的基本情况,在此基础上重点探讨田块类型及水稻栽培技术对农艺形状与产量的影响,帮助选择更高效的种植方法,提升水稻栽培产量,为种植区域创造更大的经济效益。     

两系杂交粳稻保粳杂2号在不同肥力田块下密度效应试验研究

以保粳杂2号为研究对象,在气候和生产技术基本一致的条件下,研究在高、中等2种不同肥力田块条件下栽插密度的效应。结果表明,不同肥力田块栽培密度对水稻产量的影响不同,中肥力田块所要求的栽插密度比高肥力田块高,其中高肥试点产量最高的密度处理是28.5万丛/hm2,中肥试点产量最高的密度是33.0万丛/hm2;通过密度与产量构成因素的相关性分析可知,栽培密度与有效穗、成穗率、穗粒数、结实率、总茎蘖数、生物产量、经济系数、株高、播始历期、全生育期等有关,且有规律性变化,与千粒重关系不密切。     

Spatial assessment of the correlation of seeding depth with emergence and yield of corn

Germination conditions are determined by hydraulic, thermal and mechanical properties of the soils. In heterogeneous fields, the most favourable seeding depth varies spatially. To investigate the influence of seeding depth on emergence and grain yield of corn, corn was planted in depths of 40, 50, 60, 70, 80 and 90 mm in three experimental years (2006–2008). The apparent soil electrical conductivity was measured with an EM38. The apparent electrical conductivity was used as a proxy for soil texture, top-soil thickness, effective root zone thickness, soil water content and soil structure. The spatial dependencies among emergence, yield and apparent electrical conductivity were considered by including spatial models into the statistical analysis. The results showed significant correlations of the apparent soil electrical conductivity, of the experimental year, and of the seeding depth with the emergence of corn. Deeper planted corn (80 or 90 mm) resulted in more emergence than shallow planted corn (+4.4% in 2006, +1.2% in 2007 and +1.5% in 2008). The emergence decreased with increasing apparent soil electrical conductivity values. The corn grain yield was significantly affected by the soil electrical conductivity, by emergence and by the experimental year. Increasing apparent soil electrical conductivity values were correlated with decreasing yield (from 7.5 to 3.4 Mg ha⁻¹ in 2006, from 10.8 to 5.3 Mg ha⁻¹ in 2007 and from 8.4 to 2.9 Mg ha⁻¹ in 2008). Increasing emergence resulted in increasing yield.     

A floating sensing system to evaluate soil and crop variability within flooded paddy rice fields

Continuous paddy rice cultivation requires fields to be flooded most of the time limiting seriously the collection of detailed soil information. So far, no appropriate soil sensor technology for identifying soil variability of flooded fields has been reported. Therefore, the primary objective was the development of a sensing system that can float, acquire and process detailed geo-referenced soil information within flooded fields. An additional objective was to determine whether the collected apparent electrical conductivity (EC_a) information could be used to support soil management at a within-field level. A floating sensing system (FloSSy) was built to record EC_a using the electromagnetic induction sensor EM38, which does not require physical contact with the soil. Its feasibility was tested in an alluvial paddy field of 2.7 ha located in the Brahmaputra floodplain of Bangladesh. The high-resolution (1 × 1 m) EC_a data were classified into three classes using the fuzzy k-means classification method. The variation among the classes could be attributed to differences in subsoil (0.15–0.30 m below soil surface) bulk density, with the smallest EC_a values representing the lowest bulk density. This effect was attributed to differences in compaction of the plough pan due to differential puddling. There was also a significant difference in rice yield among the EC_a classes, with the smallest EC_a values representing the lowest yield. It was concluded that the floating sensing system allowed the collection of relevant soil information, opening potential for precision agriculture practices in flooded crop fields.     

Mapping subsoil acidity and shallow soil across a field with information from yield maps, geophysical sensing and the grower

Management decisions, such as subsoil liming or varying fertilizer inputs to take account of soil depth and anticipated yields require knowledge of where subsoil constraints to root growth occur across the field. We used selected yield maps based on criteria derived from crop simulation, apparent soil electrical conductivity (EC_a), gamma-ray emission maps and a soil type map drawn by the grower to predict the spatial distribution of subsoil acidity and shallow soil across a field. Yield maps integrate the effects of variation in soil and climate, and it was only under specific seasonal conditions that subsoil constraints depressed yields. We used crop simulation modelling to select yield maps with a large information content on the spatial distribution of these constraints and to omit those with potentially misleading information. Yield and other spatial data layers were used alone or in combination to develop subsoil mapping options to accommodate differences in data availability, access to precision agriculture techniques and the grower’s aptitude and preference. One option used gamma-ray spectrometry and EM38 survey as a dual-sensing system to improve data interpretation. Gamma-ray spectrometry helped to overcome the inability of current EC_a-based methods to sense soil depth in highly weathered sandy soil over cemented gravel. A feature of the approaches presented here is the use of grower and agronomist knowledge, and experience to help interpret the spatial data layers and to evaluate which approach is most suitable and likely to be adopted to suit an individual.     

Underlying causes of yield spatial variability and potential for precision management in rice systems

Our current understanding of the mechanisms driving spatiotemporal yield variability in rice systems is insufficient for effective management at the sub-field scale. The overall objective of this study was to evaluate the potential of precision management for rice production. The spatiotemporal properties of multiyear yield monitor data from four rice fields, representing varying soil types and locations within the primary rice growing region in California, were quantified and characterized. The role of water management, land-leveling, and the spatial distribution of soil properties in driving yield heterogeneity was explored. Mean yield and coefficient of variation at the sampling points within each field ranged from 9.2 to 12.1 Mg ha^?1 and from 7.1 to 14.5 %, respectively. Using a k-means clustering and randomization method, temporally stable yield patterns were identified in three of the four fields. Redistribution of dissolved organic carbon, nitrogen, potassium and salts by lateral flood water movement was observed across all fields, but was only related to yield variability via exacerbating areas with high soil salinity. The effects of cold water temperature and land-leveling on yield variability were not observed. Soil electrical conductivity and/or plant available phosphorus were identified as the underlying causes of the within-field yield patterns using classification and regression trees. Our results demonstrate that while the high temporal yield variability in some rice fields does not permit precision management, in other fields exhibiting stable yield patterns with identifiable causes, precision management and modified water management may improve the profitability and resource-use efficiency of rice production systems.     

干湿季节下基于遥感和电磁感应技术的塔里木盆地北缘绿洲土壤盐分的空间变异性

土壤盐渍化问题是制约干旱半干旱区植被生长最主要的生态环境地质问题,也是影响绿洲农业生产的障碍性问题。而将遥感与近感技术相结合,是当前评价、监测及预报土壤盐渍化程度的先进方法。以新疆塔里木盆地北缘的渭干河-库车河三角洲绿洲为例,以遥感数据和解译后的电磁感应数据为基础数据源,利用解译后的数据结合GIS和地统计学知识以及野外实测所得到的土壤电导率和盐分资料,分别采用泛克里格(Universal Kriging)、光谱指数回归(Spectral Index Regression)和回归残差泛克里格(Regression-Universal Kriging)3种方法研究了该地区两个关键季节(干季和湿季)土壤盐分的空间变异特征。研究结果表明:研究区的土壤浸提液电导率EC_1:5和土壤盐分呈现显著相关,可以用EC_1:5来代替土壤的全盐量进行分析;电磁感应仪(EM38)所测各季节土壤表观电导率与EC_1:5的相关系数均达到1%显著水平,以表观电导率垂直读数(EM_V) 和水平读数(EM_H)为自变量的多元回归模型拟合效果较好;研究区各季节的表层土壤电导率的空间分布均表现为强相关性,说明土壤采样点间的内部结构性良好,采用能够充分考虑到干旱区表层土壤电导率空间变异的尺度依赖性的球状套合模型,能够更好的拟合土壤表观电导率的空间结构;经过精度比较,回归残差泛克里格法为最优预测方法,这表明将遥感和电磁感应技术相结合,能够有效的提高预测与评估土壤盐分空间分布的精度,为精确地进行土壤盐分预测以及土壤次生盐渍化的防控提供了一定的依据。     

Integrating Remote Sensing and Proximal Sensors for the Detection of Soil Moisture and Salinity Variability in Coastal Areas

Soil moisture and salinity are two crucial coastal saline soil variables, which influence the soil quality and agricultural productivity in the reclaimed coastal region. Accurately characterizing the spatial variability of these soil parameters is critical for the rational development and utilization of tideland resources. In the present study, the spatial variability of soil moisture and salinity in the reclaimed area of Hangzhou gulf, Shangyu City, Zhejiang Province, China, was detected using the data acquired from radar image and the proximal sensor EM38. Soil moisture closely correlates radar scattering coefficient, and a simplified inversion model was built based on a backscattering coefficient extracted from multi-polarization data of ALOS/PALSAR and in situ soil moisture measured by a time domain reflectometer to detect soil moisture variations. The result indicated a higher accuracy of soil moisture inversion by the HH polarization mode than those by the HV mode. Soil salinity is reflected by soil apparent electrical conductivity (ECa). Further, ECa can be rapidly detected by EM38 equipment in situ linked with GPS for characterizing the spatial variability of soil salinity. Based on the strong spatial variability and interactions of soil moisture and salinity, a cokriging interpolation method with auxiliary variable of backscattering coefficient was adopted to map the spatial variability of ECa. When compared with a map of ECa interpolated by the ordinary kriging method, detail was revealed and the accuracy was increased by 15.3%. The results conclude that the integrating active remote sensing and proximal sensors EM38 are effective and acceptable approaches for rapidly and accurately detecting soil moisture and salinity variability in coastal areas, especially in the subtropical coastal zones of China with frequent heavy cloud cover.     

有效微生物活菌制剂在水稻栽培上的应用效果

用有效微生物（ＥＭ）活菌制剂进行水稻栽培试验，结果表明：施用ＥＭ堆肥的小区，水稻植株根系发达，株高增加，有效分蘖多，经ＥＭ浸各上并在大田施ＥＭ堆肥的小区稻谷产量比对照增加２１．１７％。     

A flexible approach to managing variability in grain yield and nitrate leaching at within-field to farm scales

We up-scaled the APSIM simulation model of crop growth, water and nitrogen dynamics to interpret and respond to spatial and temporal variations in soil, season and crop performance and improve yield and decrease nitrate leaching. Grain yields, drainage below the maximum root depth and nitrate leaching are strongly governed by interaction of plant available soil water storage capacity (PAWC), seasonal rainfall and nitrogen supply in the water-limited Mediterranean-type environment of Western Australia (WA). APSIM simulates the interaction of these key system parameters and the robustness of its simulations has been rigorously tested with the results of several field experiments covering a range of soil types and seasonal conditions in WA. We used yield maps, soil and weather data for farms at two locations in WA to determine spatial and temporal patterns of grain yield, drainage below the maximum root depth and nitrate leaching under a range of weather, soil and nitrogen management scenarios. On one farm, we up-scaled APSIM simulations across the whole farm using local weather and fertiliser use data and the average PAWC values of soil type polygons. On a 70 ha field on another farm, we used a linear regression of apparent soil electrical conductivity (EC_a) measured by EM38 against PAWC to transform an EC_a map of the field into a high resolution (5 m grid) PAWC map. We then used regressions of simulated yields, drainage below the maximum root depth and nitrate leaching on PAWC to upscale the APSIM simulations for a range of weather and fertiliser management scenarios. This continuous mapping approach overcame the weakness of the soil polygons approach, which assumed uniformity in soil properties and processes within soil type polygons. It identified areas at greatest financial and environmental risks across the field, which required focused management and simulated their response to management interventions. Splitting nitrogen applications increased simulated wheat yields at all sites across the field and decreased nitrate leaching particularly where the water storage capacity of the soil was small. Low water storage capacity resulted in both low wheat yields and large leaching loss. Another management option to decrease leaching may be to grow perennial vegetation that uses more water and loses less by drainage.Paper from the 5th European Conference on Precision Agriculture (5ECPA), Uppsala, Sweden, 2005