石河子地区冬小麦生育期需水量变化特征及其气候成因

[目的]探究作物生育期需水量的变化趋势及其与气象因子的关系,为气候变化下农作物灌溉排水决策提供理论基础。[方法]基于联合国粮农组织(FAO)推荐的参考作物蒸散计算方法和相关作物系数,利用石河子地区1954—2012年逐日气温、降水、日照时数、风速、相对湿度等资料,计算石河子地区冬小麦近59a作物需水量和灌溉需水量,并探究其气候趋势变化的影响。[结果](1)过去50a,石河子垦区冬小麦需水量总体呈增加趋势,越冬—返青期增势最为明显(气候倾向率为2.65mm/10a);拔节—抽穗期冬小麦需水量最大,为130.23mm。(2)灌溉需水量总体呈减少趋势,其中拔节—抽穗期灌溉需水量最大(平均值为88.65mm)且减少趋势最为明显(气候倾向率为-3.11mm/10a)。(3)气象因子对冬小麦不同生育期的需水量和灌溉需水量有很强的相关性,其中冬小麦生育后期需水量与气象因子有极强的相关性;气象因子中,降水对于灌溉需水量影响最大。[结论]气候变化下,石河子地区冬小麦作物需水量呈增加趋势,但降雨量的增加趋势下,灌溉需水量总体呈减少趋势。     

气候变化对河南省主要农作物生育期的影响

利用河南省7个农业气象观测站1981-2004年冬小麦、夏玉米的生育期观测资料和同期的气象资料,分析了这两种作物主要生育期的变化趋势及对气候变化的响应。结果表明:河南省冬小麦自返青到成熟的各生育期均表现出提前的趋势,其中以拔节期提前最明显;冬小麦全生育期缩短,存在1.3d/10a的总减少趋势;相关分析显示导致冬小麦生育期提前的主要原因是2-5月平均气温的上升和3月日照时数的增加。夏玉米所有生育期都表现出延迟的趋势,以成熟期延迟程度最大;夏玉米全生育期天数呈现出显著增加的趋势,增加速率为2.1d/10a;6-9月总降水量减少是造成夏玉米生育期延迟的主要原因。     

过去30年气候变化对华北平原冬小麦物候的影响研究

全球变暖已成为全球共同关注的问题。作物物候对气候变化的响应是研究气候变化对农业生产影响的重要内容。本文选用1981—2009年华北平原16个农业气象观测站的冬小麦物候资料,利用统计方法分析了冬小麦物候的变化趋势。结果表明,过去30年华北平原冬小麦播种期、出苗期和越冬开始期推迟,而返青期、开花期和成熟期呈提前趋势。物候期的提前或推迟促使小麦不同生长发育阶段历时发生变化,出苗—越冬开始、越冬开始—返青、返青—开花等阶段呈缩短趋势,但开花—成熟阶段生育期却延长0.9 d.10a 1,整个生育期历时呈减少趋势,平均减少3.4 d.10a 1。本文采用作物模型(CERES-Wheat)模拟固定小麦品种在气候变化背景下的物候变化趋势,以探讨冬小麦物候变化的主要驱动因子。模拟结果表明,过去30年小麦开花期和成熟期提前的主要驱动因素为气候变化,品种变换在一定程度上可减缓气候变化对物候的影响。     

淮河流域冬小麦主要生育期旱涝时空特征及对产量的影响

旱涝灾害在淮河流域发生频繁,对农作物产量影响较大。该文基于淮河流域1961-2014年140个气象站逐日降水、气温数据,利用标准化降水指数(standardized precipitation index,SPI)和标准化降水蒸散指数(standardized precipitation evapotranspiration index,SPEI)定量分析冬小麦各生育期气候特征,结合1961-2012年20个站点冬小麦单产数据计算标准化产量残差(standardized yield residuals,SYR),探讨冬小麦主要生育期旱涝灾害对其产量的影响。结果表明:1)冬小麦各生育期气温均呈显著上升趋势(P0.05),气温呈南高北低、西高东低的格局,东部趋势高于西部且返青抽穗期大部分站点趋势值最高,而降水量沿纬度变化与气温一致,其变化趋势在冬小麦各生育期差异明显。2)冬小麦返青抽穗期干旱增加趋势最大(P0.05),旱涝灾害在全生育期、返青抽穗期和灌浆成熟期主要受气温影响,在冬前生长期和越冬期主要受降水量影响,同时冬小麦各生育期SPEI干旱化趋势大于SPI。3)除冬前生长期外,SYR与SPI和SPEI均呈负相关关系,以返青抽穗期相关性最高,在返青抽穗期达到中度干旱或中度湿润时产量减少。该研究尝试明晰淮河流域发生在冬小麦生育期的旱涝灾害对其产量的影响,为冬小麦生育期防灾减灾提供基础支撑。     

豫西烟区烤烟生育期35年日照时数的变化特征

利用豫西烟区(包括三门峡市和洛阳市)10个气象基准站1971-2005年烤烟生育期(5-9月)逐旬日照时数资料,分析了该区域烤烟生育期日照时数的气候变化趋势,同时利用累计距平法和滑动t检验法进行突变检验。结果表明:35a内豫西烟区日照时数变幅较大,并呈逐年下降的趋势,其趋势系数为-25.4h/10a;整个生育期内5月和6月的日照时数最多,9月最少;伸根期日照时数的下降趋势显著(P0.05),其趋势系数(-11.5h/10a)成熟期(-11.3h/10a)旺长期(-2.6h/10a)。三门峡地区烤烟生育期的日照时数大于洛阳地区。突变分析表明,豫西烟区烤烟生育期的日照时数在1981年发生突变。     

伊犁地区酿酒葡萄农业气候特征分析

利用新疆维吾尔自治区伊犁哈萨克自治州酿酒葡萄可种植区10个气象站点逐日气象和酿酒葡萄生育期数据,通过M-K检验、趋势检验等统计方法,结合ArcGIS空间表达,分析了1961-2020年研究区酿酒葡萄气候资源和农业气象灾害的时空变化特征,为高效合理利用当地积雪资源,缓解干旱及冻害,优化酿酒葡萄越冬方式,选择成本较低的积雪覆盖方式提供科学依据。结果表明：(1)1961-2020年伊犁地区除昭苏及尼勒克部分区域外光热资源丰富,年均降水量空间分布不均且低于455mm,全区年均降水量以5.1mm·10a^-1趋势增加,总体满足酿酒葡萄生长发育需求;全区酿酒葡萄越冬期(11月-翌年3月)降雪每10a增加7.4mm,且被0-10cm积雪覆盖的概率大于90%;(2)1961-2020年全区越冬期冻害频次、强度均有所下降,潜在生长季(4-10月)中7月和9月旱情较严重。     

近54年内蒙古自治区西部沙尘暴的变化趋势

[目的]研究近54 a内蒙古自治区西部沙尘暴天气发生频次的变化特征,为该区沙尘暴天气的科学预测和防治提供理论依据。[方法]采用线性回归、5 a滑动平均、小波分析、滑动t检验、Mann-Kendall检验方法分析内蒙古自治区西部24个气象站点沙尘暴日数的变化趋势、周期性、突变性等特征。[结果]①近54 a来沙尘暴天气发生频次可分为高频期(1960—1975年)、快速减少期(1976—1992年)和低频期(1993—2013年)。沙尘暴发生的频次分别为17,9和4 d/a;发生频次的周期性存在31,22,13 a三个长周期和5,8,1.5 a三个短周期的波动变化。②1986年前后沙尘暴发生频次出现了明显的突变现象,1976—1986年的线性递减率为0.76 d/a,1987—1992年的线性递减率为1.4 d/a。[结论]近54 a内蒙古自治区西部沙尘暴日数变化呈波动下降趋势,且存在明显的周期性和突变性特征。     

气候变化对安徽省两熟制粮食作物物候期及周年气候资源分配与利用的影响

为了进一步明确江淮区域气候变化对两熟制粮食作物物候期及周年光温水资源分配与利用的影响,以安徽省12个农业气象观察站1992—2013年气象数据、作物生长发育期数据与产量数据为基础,采用线性趋势、相关分析、回归分析等方法,分析不同区域不同熟制作物物侯期变化趋势,以及气候变化对积温、辐射和降水资源分配与利用的影响。结果表明,1992—2013年沿淮淮北冬小麦-大豆种植模式,冬小麦播种期提前趋势显著(P0.05),平均每10a提前3.03d,成熟期变化不显著,全生育期平均每10a增加3.54d;大豆播种期和开花期则显著推迟(P0.05),平均每10 a推迟3.06 d和0.86 d,全生育期平均每10 a减少3.65 d。江淮冬小麦-一季稻模式,水稻播种期、抽穗期和成熟期均显著提前(P0.05),平均每10 a分别提前5.12 d、3.87 d和2.92 d,全生育增加2.2 d;小麦有同样的变化趋势,全生育期表现为每10 a缩短0.8 d。沿江江南双季早稻物候期变化不明显,全生育期每10 a缩短0.6 d;晚稻平均每10 a播种期推迟1.14 d,抽穗期与成熟期分别提前0.71d和6.85 d,成熟期提前趋势显著(P0.01),全生育期每10 a缩短5.17 d。沿淮淮北冬小麦与江淮一季稻以及沿江早稻和晚稻生长季积温呈增加趋势,大豆与江淮冬小麦积温减少。沿淮淮北与江淮冬小麦及沿江早稻和晚稻生长季辐射呈增加趋势,大豆与一季稻则表现为减少。不同种植模式第1季作物冬小麦和早稻的降水均有减少趋势,而第2季作物大豆、一季稻和晚稻则呈增加趋势。冬小麦-一季稻种植模式周年光温水生产效率最高。线性回归分析表明,积温和辐射与沿淮淮北冬小麦和沿江双季稻的产量均呈显著线性正相关(P0.05),光温是提高其产量的主要限制因子。江淮一季稻积温过高和降水过多也限制产量提升。气候变化改变了两熟制粮食作物物侯期,进一步影响了光温水气候资源的分配与利用效率。通过改良品种、改变播栽时间、提高抗逆性等适应措施,可以在一定程度上抵消气候变化对作物生长的不利影响。     

贵州西部马铃薯生育期气候因子变化规律及其影响分析

利用贵州西部14县(市)1978-2009年连续32a的马铃薯生育期(3-9月)的定位观测和加密观测资料、1960-2009年3-9月地面平行观测气象资料,采用气候变化倾向率、Morlet小波分析、Cubic函数以及积分回归等方法,对贵州西部马铃薯生育期主要气候因子变化规律及其对马铃薯生长的影响进行分析,以期为马铃薯产业发展提供依据。结果表明,研究区马铃薯生育期平均气温年际变化呈极显著上升趋势,倾向率为1.96℃/10a(P<0.01),马铃薯块茎膨大期(7-8月)气温日较差呈显著下降趋势,倾向率为-1.82℃/10a(P<0.05);马铃薯生育期降水量年际变化呈显著下降趋势,倾向率为-50.26mm/10a(P<0.05),日照时数年际变化呈显著下降趋势,倾向率为-0.62h/10a(P<0.05)。同时降水量存在3a和9a的周期变化,日照时数存在3a、8a和48a的周期变化。马铃薯播种到收获需历时155～175d,>10℃积温达2100～3800℃.d,降水量730～1300mm,日照时数820～1100h。气温对马铃薯产量形成为负效应,但块茎膨大期气温日较差对其为正效应,且该期对气温变化十分敏感;降水量对马铃薯产量形成除开花期(5月中旬-6月下旬)为负效应外,其余时段均为正效应,马铃薯开花期到块茎膨大期(5月中旬-8月下旬)对降水量变化十分敏感;日照时数对马铃薯产量形成除苗期(3月下旬-5月中旬)为负效应外,其余时段均为正效应,马铃薯开花前期(5月中旬-下旬)和块茎膨大期对日照时数变化十分敏感。     

近20年来陕西中部地区主要农作物生育期变化趋势分析

利用陕西省中部地区8个农业气象观测站1992-2010年冬小麦、夏玉米的生育期观测资料,分析了这两种作物主要生育期的变化趋势。结果表明：该地区冬小麦全生育期有不断缩短趋势,变化速率约为每10a缩短2.96d,各个站点变化趋势基本一致,但减少的速度不尽相同,其中凤翔站变化趋势较为显著（显著性达0.05水平）;冬小麦其它各生育阶段也都呈现出比较一致的变化趋势,其中播种-出苗、返青-拔节、拔节-抽穗、返青-成熟阶段呈缩短趋势,抽穗-乳熟、乳熟-成熟、播种-越冬阶段呈延长趋势,其余生育阶段变化趋势不明显。该地区夏玉米全生育期呈较一致的延长趋势（显著性超过0.05）,增加速率约为4.29d/10a,延长的时间主要在播种-三叶、七叶-拔节、乳熟-成熟阶段,其余生育阶段变化趋势不明显。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【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。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

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.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

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,     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

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.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

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,     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

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,     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

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.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

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.