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1.
温室动态星型无线传感器网络通信方法研究 总被引：8，自引：2，他引：6
针对温室测控系统信息传输技术存在的一些问题,根据温室结构特征提出一种动态星型无线传感器网络的框架,从低成本低功耗角度出发,移动的汇聚节点采用定时跳频方法与子节点形成子网,以尽量缩短点对点之间的通信距离。利用帧扩展的方法实现了以低功耗芯片nRF2401A构成复杂的通信网络,并给出了传感器节点、控制节点和汇聚节点的通信算法。在汇聚节点不同的工作状态下,对网络子节点进行能耗分析,结果表明,动态星型无线传感器网络的通信方法具有很好的节能效果,对温室中数据的传输是有效的。 相似文献
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农田信息采集无线传感器网络节点设计 总被引：26，自引：12，他引：14
农田信息的及时准确获取是精准农业实施的基础。该文分析了几种典型无线传感器网络技术应用实例,基于当前无线传感器网络在农田信息采集中的应用现状,提出了设计体积小、工作持续时间长的农田信息采集无线传感器网络节点的必要性。基于ATmega128L单片机和CC1000射频芯片设计了无线传感器网络节点通信电路,并给出了土壤温湿度、电导率传感器、空气温湿度传感器及光照度传感器的选型和指标参数。设计了节点软件系统,描述了一种基于优先级的静态任务调度机制的实现方法,将S-MAC中的SYNC帧和RTS/CTS帧融合并加入了睡眠周期动态调度机制,并实现了全网的长周期睡眠。最后对节点进行了验证试验,给出了节点吞吐能力曲线和系统电压变化曲线,并进行了分析。试验表明,在论文给出的低功耗机制控制下,节点每秒具有6个数据包处理能力;在20个节点容量的全覆盖网络中,10 min采样周期下,节点可有效持续工作150 d以上,可以满足精准农业信息采集需求。 相似文献
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基于发射功率自适应的稻田无线传感器网络节点设计 总被引：1，自引：1，他引：0
针对水稻生长过程环境因素变化较大以及传感器节点的能量大部分被无线射频阶段所消耗,设计了发射功率自适应的无线传感器节点,建立了长时间、稳定、高可靠性的稻田无线传感器网络。试验测试了水稻的株高、叶面积与生长天数的关系以及对无线信道的影响,结果表明水稻株高和叶面积的增加会降低无线信号强度和通信成功率;通过增大发射功率可以提高通信质量克服由于水稻生长因数对无线信道的影响。在软件设计方面,传感器节点采用睡眠、苏醒工作机制来降低功耗。同时为了延长工作时间、提高通信质量,提出了根据水稻生长周期、通信距离、接收信号强度、平均丢包率等因素自动调整节点发射功率的能量自适应功耗调整机制。田间试验结果表明,水稻田节点发射功率越大,有效通信距离越远,且水稻的密度和高度等对通信有重要的影响;节点发射功率在5 dBm以下时,发射功率的改变对节点工作电流影响较小,节点工作电流均小于40 mA;采用该机制对发射功率进行调整,增大节点发射功率可使通信成功率有大幅的提升;降低节点发射功率仍然保持良好的通信效果。水稻分蘖和抽穗2个生长时期的田间试验结果表明,采用发射功率自适应策略,提高了通信质量,平均丢包率在5%以下,通信成功率大于97%,达到了预期设计目的。 相似文献
5.
大面积水稻田无线传感器网络组网设计与优化 总被引：1，自引：1，他引：0
为解决大面积水稻田无线传感器网络能量消耗过快和丢包率严重等问题,该文提出了不同天线模式下的3种组网方案:配备全向天线的分环多跳网络、配备定向天线的多跳网络和配备混合天线的分簇多跳网络。第一组网络,处于不同环中配备全向天线节点采用多跳传输模式将数据包传输到基站;第二组网络,各级配备定向天线节点采用多跳传输模式将数据包传输至第一级节点;最后一组网络,借助于双簇头分簇思想,主簇头接受副簇头汇聚于成员节点的数据包与基站多跳通信。首先,介绍了3种网络拓扑结构间的差异;然后,从网络能耗角度,理论上分别计算了3组网络的能量消耗;仿真试验表明,混合天线分簇多跳组网方案相比定向天线多跳方案数据包个数提升了近10倍;相比全向天线分环多跳方案网络稳定周期延长了24.3%,网络寿命延长了28.2%;最后,采用无线通信模块nRF905射频芯片和TDJ-0825BKM1定向天线进行了水稻田组网试验,结果表明混合天线分簇多跳网络相比全向天线分环多跳网络丢包率降低了8.11%,平均存活时间效率提高了8.66%。该研究可为大面积水稻田无线传感器网络组网方案的设计提供参考。 相似文献
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基于3S技术联合的农田墒情远程监测系统开发 总被引：14，自引：8，他引：6
农田墒情信息是现代农业实施精准施肥、精确灌溉的重要科学依据。为了实现快速准确地采集墒情信息,研究开发了基于3S（GPS/GIS/GPRS）技术联合的农田墒情远程监测系统。该系统主要由农田信息监测网络节点和远程服务器组成,在小范围内由传感器节点基于ZigBee通讯协议组成无线传感器网络,在大尺度上通过网关节点集成GPS网络,利用GSM/GPRS网络实现与Internet的信息交互,完成了墒情数据的自动采集、无线传输和准确定位。设计了太阳能自供电的长寿命无线传感器节点和网关节点,开发了服务器端农田墒情信息管理系统软件,实现了Web方式下的参数远程设置和信息实时监测。该系统的设计开发为农田墒情信息监测和分析决策提供了有效的工具。 相似文献
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基于ZigBee和PDA的农田信息无线传感器网络 总被引：7，自引：4，他引：3
为了实现农田信息的实时采集、处理与可视化,缩短数据采集和处理间的时差,开发了基于ZigBee和PDA的农田信息无线传感器网络。系统由集成ZigBee协调器的PDA和带传感器的路由节点组成。通过无线传感器网络,用户手持PDA可实时动态访问田间信息,并控制传感器的供电电源开关,以节省功耗。采集的田间信息包括土壤水分、土壤温度、土壤电导率、空气温湿度。其中土壤温度、空气温湿度传感器为数字式传感器,土壤水分、土壤电导率传感器为模拟传感器。节点通信距离试验表明,正常工作条件下,40 m距离的丢包率只有0.092,满 相似文献
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稻田水分监测无线传感器网络优化设计与试验 总被引：4，自引：4，他引：0
传感器网络技术为大范围稻田水分信息采集提供了一种新技术手段。利用测量稻田水分含量和水层深度测量的无线传感器WFDMS,探讨了构建稻田水分传感器网络PMSN的关键技术：设计了大面积、大范围应用体系结构模型;提出了一种满足稻田水分采样频率和数据业务需求的低功耗传输控制协议LPTP-PMSN;开发了水分信息监测信息管理系统,实现了完整运行的稻田水分传感器网络整套系统。试验表明,PMSN网络在稻田中的可靠通信距离达60 m,在 3.6 V/2 100 mAh电池供电下,4 h周期采样试验中,在传输协议LPTP-PMSN控制下,传感器、簇首、基站、短信网关、计算机间能够协同工作,整个稻田水分传感器网络可以较可靠运行,节点生命期超过190 d。该研究可为农用信息监控无线传输网络的其他应用提供参考。 相似文献
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基于无线传感器网络的无人机农田信息监测系统 总被引：2，自引：7，他引：2
移动无线传感器网络技术为农田信息监测提供了高效可行的技术手段。该研究根据南方农田地块相对分散、丘陵山地多,农情信息获取环境恶劣、采集数据时间周期长、网络分割成块的特点,利用UAV(unmanned aerial vehicle)具有的高效、灵活的特性,结合低功耗无线传感器网络,提出一种满足南方农田信息获取采样和数据业务需求的三层架构的无线传感器网络体系结构TUFSN(three-tire unmanned aerial vehicle farmland sensor network),其由数据采集层、中继传输层和移动汇聚层组成,该体系结构具有系统结构合理、可扩展性好、系统整体能耗低等特点。通过仿真可得中继节点RN（relay node）的缓存大小范围为3～13kB,系统试验中携带移动节点的UAV以1m/s的速度、15 m的高度在农田上空飞过,飞行过程中与地面中继节点通信并采集农田信息,UAV与地面中继节点的平均通信时长为26 s,仿真和试验表明,基于UAV的三层架构农田信息采集无线传感器网络很好地满足了南方地区农田信息数据采集和监控的生命周期长、传输数据可靠、覆盖面积广的要求。 相似文献
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基于低功耗传输方法的设施花卉环境监测系统 总被引：2，自引：2，他引：0
为了降低现有设施环境监测系统中传感节点的能耗,延长无线传感网络的生存周期,该文提出了节点动态组包主动传输和多种环境变量加权控制传输2种低功耗机制,减少了大量重复冗余数据的传输,并实现了基于Zigbee的设施花卉环境监测及其低功耗传输系统。节点以CC2430芯片为核心,并根据影响花卉生长的环境参数,同时装载SHT10温湿度传感器、BH1750FVI光照传感器以及COZIR二氧化碳传感器,因此节点可同时采集传输多种环境参数,降低了硬件成本。在南农大园艺试验基地进行组网测试,试验结果表明,系统比传统周期传输节点(周期1min)的能耗减少85.97%,测量精度在98.5%以上,网络平均丢包率为0.84%,满足了对设施花卉环境的有效监测及低功耗传输的要求。 相似文献
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低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响 总被引：2，自引：2，他引：0
【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。 相似文献
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Kyle Devey Michael Mucalo Gordon Rajendram Joseph Lane 《Communications in Soil Science and Plant Analysis》2015,46(4):72-80
Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing. 相似文献
13.
《中国生态农业学报》2014,(8)
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology, 相似文献
14.
I.L. Boyd 《Biological conservation》2010,143(7):1664-1674
“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options. 相似文献
15.
Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage 总被引：1，自引：0，他引：1
Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate. 相似文献
16.
M.A. Callaham Jr. J.M. BlairT.C. Todd D.J. KitchenM.R. Whiles 《Soil biology & biochemistry》2003,35(8):1079-1093
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils. 相似文献
17.
Grete Skrede Berit Karoline Martinsen Anne-Berit Wold Stein-Erik Birkeland Kjersti Aaby 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):193-208
Abstract A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species. 相似文献
18.
Yoav Bashan Bernardo Salazar Ma. Esther Puente Macario Bacilio Robert Linderman 《Biology and Fertility of Soils》2009,45(6):585-594
To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse
trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus
were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB;
the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons
reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened
later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons
growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants,
no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi,
enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant.
In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after
30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination
only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity
to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as
compost or PGPB can either amplify the effect or else attenuate it. 相似文献
19.
Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value. 相似文献
20.
《Communications in Soil Science and Plant Analysis》2012,43(7):865-877
Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L?1 nitric acid (HNO3) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L?1 ammonium acetate (NH4OAc) and 1.0 mol L?1 HNO3 extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils. 相似文献