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1.
为研究灌水量、施氮量和缩节胺用量对棉花籽棉产量、纤维品质和水肥利用效率的交互影响,于2020年和2021年在南疆库尔勒地区开展大田试验,设置3个灌水量（W1：60%ETc,W2：80% ETc,W3：100% ETc,ETc为作物蒸发蒸腾量）,4个施氮量（N0：0 kg/hm2,N200：200 kg/hm2,N300：300 kg/hm2,N400：400 kg/hm2）和2个缩节胺用量（D1：120 g/hm2,D2：240 g/hm2）。结果表明：灌水量、施氮量和缩节胺用量对籽棉产量、水分利用效率、肥料偏生产力和部分纤维品质指标影响显著（P<0.05）。灌水量、施氮量和缩节胺用量三者交互作用对肥料偏生产力和纤维品质影响显著（P<0.05）。株高、叶面积指数和干物质量也受灌水量、施氮量和缩节胺用量三者交互作用影响。W3N300D2处理籽棉产量最高（2020年为7 578 kg/hm2,2021年为7 173 kg/hm2）,W1N400D1处理水分利用效率和W3N0D2处理肥料偏生产力最高,W3N400D1处理的纤维长度、纤维强度和马克隆值均获得较大值,纤维品质最佳。基于TOPSIS综合评价方法对棉花产量品质和水肥利用效率进行综合评价,100%ETc灌水量、300 kg/hm2施氮量和240 g/hm2缩节胺用量组合最优,可作为南疆棉花适宜的水氮和化控管理模式。研究结果可为南疆棉花水肥高效利用提供理论依据和科学指导。 相似文献
2.
根据2009—2014年在长江中下游薯区实施的68个氮、磷、钾肥料用量田间试验结果，建立了基于养分丰缺指标法——肥料效应函数的甘薯氮、磷、钾施肥指标体系。结果表明：施用氮肥、磷肥、钾肥均对甘薯具有极显著的增产效果(P<0.01)；植薯土壤水解性氮含量的“高”、“低”指标分别为170 mg/kg和100 mg/kg，有效磷含量的临界指标为17 mg/kg，土壤速效钾含量“高”、“低”的指标分别为110 mg/kg和30 mg/kg；高产田块甘薯的氮、磷、钾肥最佳经济推荐施用量分别为N 125 kg/hm2、P2O5160 kg/hm2和K2O 182 kg/hm2，中低产田块的氮、磷、钾肥最佳经济推荐施用量分别为N 155 kg/hm2、P2O5120 kg/hm2和K2O 220 kg/hm2。 相似文献
3.
华北平原小麦-玉米农田生态系统服务评价 总被引：8，自引：1，他引：7
本研究于2006 年和2007 年在中国科学院栾城农业生态系统试验站田间试验基础上, 评价了华北平原小麦-玉米农田的初级产品生产、气体调节、土壤有机质累积、水调节和氮素转化等5 项生态系统服务。研究表明, 华北平原小麦-玉米农田初级产品量包括籽粒产量5.04~5.71 t·hm-2·a-1(小麦)和6.69~8.24t·hm-2·a-1(玉米), 秸秆量8.58~9.72 t·hm-2·a-1(小麦)和6.97~8.58 t·hm-2·a-1 (玉米); 农田气体调节包括释放O2 24.99~28.64 t·hm-2·a-1, 固定CO2 34.23~39.22 t·hm-2·a-1, 排放N2O 0.72~1.13 kg·hm-2·a-1, 吸收CH4 3.39~5.70 kg·hm-2·a-1; 农田耕层土壤有机质累积量为1.13~2.39 t·hm-2·a-1; 水资源消耗量为2 890~3 830 m3·hm-2·a-1; 农田土壤氮素几乎都处于亏缺状态, 变化范围为-107.73~5.33 kg(N)·hm-2·a-1, 不施氮肥农田亏缺较多。综合评价发现, 小麦-玉米农田提供生态服务的经济价值为5.48~6.25 万元·hm-2·a-1, 是粮食生产价值的3 倍左右。氮肥施用对农田生态系统服务及其产生福利的影响较为复杂, 这主要是由于施加氮肥明显增加了氮素转化功能导致的经济损失, 而同时可能会增加初级产品生产、气体调节中作物固定CO2 和释放O2 功能的经济价值。尽管目前有关生态系统服务评价研究主要关注生态系统产生的正效应, 但仍有必要对农田产生的负效应做出评价, 以便客观看待农田生态系统价值, 正确认识农田生态系统对人类福利的影响。 相似文献
4.
施氮水平对太行山前平原冬小麦-夏玉米轮作体系土壤温室气体通量的影响 总被引：10，自引：4，他引：6
应用静态明箱-气相色谱法对4 个施氮肥水平N0 [0 kg(N)·hm-2]、N200 [200 kg(N)·hm-2]、N400 [400kg(N)·hm-2]、N600 [600 kg(N)·hm-2]的夏玉米-冬小麦季轮作体系2008~2010 年的土壤温室气体(CH4、CO2 和N2O)排放通量进行研究, 同时观测5 cm 土层土壤温度并记录降水量。结果表明: 太行山前平原冬小麦-夏玉米轮作农田生态系统为CH4 吸收汇, CO2 和N2O 排放源。随着氮肥施入量的增加土壤对CH4 的吸收速率降低, 而CO2 和N2O 的排放速率增加。冬小麦季施氮处理土壤对CH4 的吸收速率显著低于无氮肥的N0 处理, 而N600处理土壤CO2 和N2O 排放速率显著高于N0 处理(P<0.05)。施肥和灌溉会直接导致土壤CO2 和N2O 的排放通量增加, 同时土壤对CH4 的吸收峰值减小。土壤温度升高和降水量增加以及干湿交替加剧均会造成N2O 和CO2排放速率增加。同时在持续干燥和低温条件的冬季不施氮处理观测到土壤对N2O 的吸收现象。N0、N200、N400 和N600 处理土壤CH4 年排放总量(kg·hm-2·a-1)分别为-1.42、-0.75、-0.82、-0.92(2008~2009 年)和-2.60、-1.47、-1.35、-1.76(2009~2010 年), N0、N200、N400 和N600 处理土壤CO2 年排放总量(kg·hm-2·a-1)分别为15 597.6、19 345.6、21 455.9、29 012.5(2008~2009 年)和10 317.7、11 474.0、13 983.5、20 639.3(2009~2010年), N0、N200、N400 和N600 处理土壤N2O 年排放总量(kg·hm-2·a-1)分别为1.05、2.16、5.27、6.98(2008~2009年)和1.49、2.31、4.42、5.81(2009~2010 年)。 相似文献
5.
灌溉对大麦/玉米带田土壤硝态氮累积和淋失的影响 总被引：7，自引：3，他引：7
以甘肃省河西走廊灌区为试验地点，分别在0、150、300 kg/hm2氮水平和816、1632 m3/hm2灌水量下，对3次灌水前、后大麦/玉米带田0～200 cm土壤NO-3-N含量变化和灌水后135 cm处渗漏液NO-3-N浓度进行了测定。结果表明：灌水明显影响土壤硝态氮累积量，随灌水次数增加，土壤硝态氮累积量降低，而且在高灌水条件下土壤硝态氮累积量变化比低灌水量时大。从渗漏液硝态氮浓度来看，大麦带和玉米带都是以第1次灌水最高，浓度分别为8.04～17.21和3.30～14.57 mg/L。3次灌水土壤硝态氮淋失量，玉米带以N 150 kg/hm2和灌水量1632 m3/hm2最高，平均为4.31 kg/hm2；大麦带以N 150 kg/hm2及灌水量1632 m3/hm2和N 150 kg/hm2及灌水量816 m3/hm2比较高，平均为6.82 kg/hm2。 相似文献
6.
华北山前平原农田生态系统氮通量与调控 总被引：4，自引：2，他引：2
针对华北太行山前平原冬小麦-夏玉米轮作农田, 研究农田常规施肥[400 kg(N)·hm-2·a-1]条件下作物氮素吸收与损失通量过程, 并根据各氮素输出通量特征开展管理调控。研究结果表明, 全年小麦-玉米轮作农田系统氮输入总量为561~580 kg(N)·hm-2, 输出量468~494 kg(N)·hm-2, 两季作物总盈余86~93 kg(N)·hm-2, 其中有机氮为24~36 kg·hm-2。氨挥发和NO3--N 淋溶损失是该区域农田氮素损失的主要途径, 是氮肥利用率低的重要原因。平均每年因氨挥发而造成的肥料氮损失量为60 kg(N)·hm-2, NO3--N 淋溶损失量为47~84kg(N)·hm-2, 两者占施肥总量的30%。每年因硝化-反硝化过程造成的肥料损失很小, 仅为5.0~8.7 kg(N)·hm-2。通过施肥后适时灌水、合理调控灌水时间与用量, 以及利用秸秆还田与肥料混合施用等管理措施可改善氮素的迁移和转化规律, 有效减少氨挥发和NO3--N 淋溶损失, 并结合缓/控释肥与精准施肥技术, 充分利用土壤本身矿质氮素, 可有效提高养分利用效率和作物产量, 改善农田生态环境与促进农业持续和谐发展。 相似文献
7.
通过评价多种生态系统总初级生产力(gross primary productivity,GPP)和蒸散(evapotranspiration,ET)遥感数据产品,构建了适用于我国秦岭区域的GPP和ET组合数据集,并计算分析了秦岭区域生态系统水分利用效率(water use efficiency,WUE)的时空变化规律。结果表明:不同产品对于不同植被类型GPP和ET的估算效果差异较大,其中VPM GPP和RF GPP这2种GPP产品,China ET和PML-V2 ET这2种ET产品的总体表现较好。秦岭区域的多年平均GPPyear为1 489.95 g C/m2,ETyear为588.49 mm,WUEyear为2.56 g C/kg H2O,多年平均WUEyear的变化率为0.156 g C/(kg H2O·10 a)。秦岭区域WUEyear总体呈现出不显著的上升趋势(p>0.05);秦岭区域不同植被覆盖下的多年平均WUEyear数值差异不大,但WUEyear的变化趋势略有不同,部分植被类型呈现上升趋势,而其他植被类型呈现下降趋势;多年平均逐月WUEmonth变化多呈现较为明显的"双峰"模式。研究结果为不同类型生态系统水碳关系研究中获取和选择数据提供了依据和途径,加深了对秦岭区域生态系统WUE时空变化规律的认识,从而为研究气候变化对秦岭地区生态系统的影响提供了数据支持和科学参考。 相似文献
8.
为明确干旱区最优覆盖地膜类型和施氮制度，于内蒙古河套灌区木垒滩节水试验站进行为期2年的不同类型地膜覆盖农田不同施氮量试验。在高氮水平（传统施氮336 kg/hm2）下设置3种覆膜处理，包括塑料地膜（PFM3）、生物降解地膜（BFM3）和无膜覆盖处理（NFM3）；同时在生物降解地膜覆盖下设立3个施氮水平，包括中氮（BFM2，276 kg/hm2）、低氮（BFM1，216 kg/hm2）和不施氮（BFM0，0 kg/hm2），共6个处理。利用2年观测的产量、吸氮量和氮淋失量对DNDC模型进行率定和验证，并基于改进的TOPSIS方法对地膜类型和施肥制度进行优化。结果表明：DNDC模型对地膜覆盖及氮肥调控下作物生长与氮素迁移较为敏感，产量、吸氮量与氮淋失量模拟的EF与R2均大于0.83，NRMSE均小于20%，能够为作物生产力与资源利用进行预测和评估。随施氮量增加，所有覆膜处理的氮淋失量呈线性增加，当施氮量增加至106 kg/hm2时，氮肥利用率达到峰值；当施氮量增加至256 kg/hm2时，覆膜处理的产量不再发生明显变化，同时生物降解地膜的净收益也达到最大值；但其成本高，导致净收益比塑料地膜降低6.84%，比无膜覆盖处理提高3.17%。塑料地膜和生物降解地膜覆盖下的氮淋失量、氮肥利用率和产量无明显差异，均大于无膜覆盖处理，平均提高8.22%~26.69%。利用改进的TOPSIS法对产量、氮淋失量、残膜量、氮肥利用率和净收益5个方面进行综合评价，选出在生物降解地膜覆盖下施用氮肥231~256 kg/hm2是干旱地区较合理的覆膜施氮制度。 相似文献
9.
为系统研究硝态氮、铵态氮及二者不同配施比例对土壤养分供应与水稻生长情况的影响，通过田间小区试验，在相同施氮量条件下，研究了单施硝态氮(N)，单施铵态氮(A)，硝态氮、铵态氮按1:3(N1A3)、2:2(N2A2)、3:1(N3A1)比例配施对水稻产量、田间养分和氮素利用率的影响，并与农民习惯性施肥方式(U)作比较。研究结果表明：整个生育期内铵态氮对水稻的生长都起着主要作用，铵态氮通过提高水稻氮素利用率和促进水稻有效分蘖的方式提高了水稻产量。随着铵态氮的配施比例由25% 提高到75%，水稻的产量提高了35.18%、氮素利用率提高了46.67%，每公顷产生的经济收益增加了6 820.15元。A处理土壤中硝态氮、铵态氮和碱解氮的含量较N处理显著增加36.41%、30.30% 和8.42%，水稻产量提高了60.11%，氮素利用率提高了171.31%，有效穗数增加了52.31%，相较农民习惯性施肥，单施铵态氮处理每公顷还能增收522.91元。在0 ~ 180 kg/hm2的施氮量范围内，水稻产量(y)与铵态氮施用量(x2)呈显著正相关，二者之间关系为y = 18.044x2 + 4943.4(R2 = 0.975 3)。 相似文献
10.
探讨有机物料还田对冬小麦田温室气体排放特性的影响,对提高经济效应和环境效应有积极意义。本研究应用静态箱-气相色谱法对秸秆还田（J）、秸秆还田+牛粪（JF）和秸秆还田+菌渣（JZ）3种有机物料还田下分别施氮肥243 kg （N）·hm-2（减氮10%,N1）、216 kg （N）·hm-2（减氮20%,N2）对冬小麦农田N2O、CO2和CH4的排放通量进行监测,探讨了不同施肥措施对麦田温室气体累积排放量、增温潜势的影响。试验期间同步记录每项农事活动机械燃油量、施肥量和灌溉量,测定产量,地上部生物量,估算农田碳截留。结果表明,冬小麦农田土壤N2O和CO2是排放源,是CH4的吸收汇,氮肥施入、灌溉以及强降水促进了土壤N2O和CO2的生成,却弱化了CH4作为大气吸收汇的特征。牛粪+秸秆（JF）处理N2O和CO2排放总量最高,分别为3.5 kg （N2O-N）·hm-2和19 689.67 kg （CO2-C）·hm-2,但CH4的吸收值最大,为5.33 kg （CH4-C）·hm-2,均显著高于菌渣+秸秆（JZ）和秸秆（J）处理（P<0.05）;各处理N2O和CO2的总量随施氮量的增加呈升高趋势,CH4的总量随施氮量的增加而呈降低趋势。JFN2、JN2和JZN2处理农田综合增温潜势（GWP）均为负值,表明有机物料还田且减氮20%条件下农田生态系统为大气的碳汇,麦季净截留碳1 038~2 024 kg·hm-2,其他处理GWP值均为正。JZN2处理小麦产量为8 061 kg·hm-2,显著高于JFN2处理（P<0.05）。综上所述,JZN2处理不仅能够保证小麦产量,且对环境效应最有利,为本区域冬小麦较优的施肥管理模式。 相似文献
11.
In order to identify key adaptive traits which affect productivity in Mediterranean grain and forage legumes and simultaneously determine the agricultural potential of a wide range of Vicia species, germplasm collected from the wild throughout the eastern Mediterranean was grown under semi-arid conditions in Tel Hadya, Syria (313 mm growing season rainfall). These included species currently in use in Mediterranean agriculture, such as V. sativa L., as well as those more widely used in the past-such as V. ervilia L., but also a broad selection from Section Narbonensis (B. Fedtsch. ex Radzhi) Maxted, including V. narbonensis L, V. johannis Tamamsch., V. hyaeniscyamus Mout., V. serratifolia Jacq., and V. kalakhensis Khattab et al. V. faba, a near relative of the taxa in Section Narbonensis, was included as a domesticated control. Where applicable, a representative range of subspecies was used. Accessions were chosen from a wide range of habitats in terms of latitude (31.02–40.72 decimalo), longitude (27.1–43.17 decimalo), altitude (20–1510 m), rainfall (180–1700 mm/yr) and soil depth (5–50 cm) in order to maximise diversity within species. Agricultural potential was determined by measuring seed, hay and biological yield, as well as agronomic traits such as harvest index, standing crop height, and seed size. The comparative influence of phenology and key agronomic traits such as plant habit and seed size on productivity varied tremendously between species, depending on their reproductive strategies. In V. sativa and V. ervilia, the smaller seed species which rely on long vegetative phases and growing seasons to accumulate sufficient biomass to set seed, and in which there was comparatively little agronomic variation, phenology had a large impact on yield. In early emerging taxa such as V. ervilia and V. s. subsp. sativa, with built-in long vegetative phases and growing seasons, seed yield was negatively correlated with flower ing (r = –0.86 to –0.88), whereas the opposite was the case for later emerging taxa such as V. s. subsp. nigra (L.) Ehrh. (r = 0.95). Within V. narbonensis and relatives, the larger seeded Vicia species which rely on more conservative reproductive strategies where high seedling vigour associated with large seeds enables the species to enter reproductive phases relatively early, phenology had a much smaller impact on yield than did variation of key traits such as seed weight, plant habit and pod shattering. Among the undomesticated germplasm harvest indices ranged from 0.09–0.31, hay yields from 0.1–3.4 t/ha, seed yield from 0–2.0 t/ha, and dry matter at maturity from 1.6–6.5 t/ha. Sub-specific taxonomy was crucial in determining agronomic potential. V. narbonensis var. aegyptiaca Kornhuber ex Asch. et Schweinf. showed the most potential, combining an upright habit, large seeds (212 mg) and tendency to retain intact pods after maturity, with the highest yield, harvest index and crop height of all the wild Vicia species. V. sativa subsp. sativa, V. ervilia and V. narbonensis var. narbonensis were less productive, but still showed agricultural potential. The smaller seeded V. narbonensis, var. affinis, var. jordanica H. Schäf. and var. salmonea (Mout.) H. Schäf., and their close relatives V. johannis, V. hyaeniscyamus, V. serratifolia and V. kalakhensis have little to offer Mediterranean agriculture on the basis of poor agronomy. 相似文献
12.
I. V. Rodushkin T. I. Moiseenko L. P. Kudryavtseva 《Water, air, and soil pollution》1995,85(2):731-736
The powerful mass-flow of melt water during the brief period of spring thaw provides a surge of pollutants and causes extremely toxic short term conditions. Together with the increase in total metal concentrations during this period, a redistribution in metal speciation occurs that increases the proportion of more toxic forms. Concentrations of ion-exchangeable fractions of nickel (Ni), copper (Cu), aluminium (Al), and manganese (Mn) show strong negative correlations with pH. The sum of complex metal species shows a strong positive correlation with total organic carbon (TOC). A data analysis model based on relationships observed between key parameters and metal behaviour together with gidrological data allowed an assessmrnt of the metal impact on waterbodies from accumulated airborne pollution (Ni, Cu) as well as from accelerated leaching from watersheds (Al, Mn). 相似文献
13.
The difficulty and problems encountered in the study of cultivated plants, in general and sugarcane, in particular has been
indicated. In order to understand these problems, a brief review on the taxonomy of Saccharum and closely related taxa, namely, Erianthus, Sclerostachya, Narenga and Miscanthus (generally known as ‘Saccharum complex’) has been given. A short account on the important morphological features that are specific to sugarcane has also
been stated as classification is commonly based on such morphological characters. A note has been added on the chromosome
number, origin, and distribution of the species of ‘Saccharum complex’ members. Taxonomic keys have been devised for identification of the genera of Saccharinae and for the species of
Saccharum and Erianthus occurring in India. A new combination, Sclerostachya fallax (Balansa) Amalraj et Balasundaram, has also been proposed. 相似文献
14.
15.
16.
J. K. Leary N. V. Hue P. W. Singleton D. Borthakur 《Biology and Fertility of Soils》2006,42(3):215-223
Gorse (Ulex europaeus) infestation occupies over 4,000 ha of agriculture and conservation lands on the southeastern slope of Mauna Kea on the Island
of Hawaii. The aim of this investigation is to identify ecological features associated with this weed invasion by comparing
the gorse-infested areas to the surrounding uninfested areas of this landscape. The soils within the gorse infestation are
more acidic, resulting in higher levels of KCl-extractable Al and lower levels of Mehlich III-extractable Ca, Mg, Mn, and
Zn. Yet, gorse accumulates higher concentrations of Ca, Zn and, Cu than the kikuyu grass (Pennesitum clandestinum), which is ubiquitous throughout the site. The Ca:Al and Mg:Al molar charge ratios of the soils are lowest within the epicenter
of the gorse infestation, while the molar ratios are highest in the gorse apical stem tissues. All gorse plants are nodulated
and have higher nitrogen contents than the surrounding kikuyu grass. Furthermore, the δ15N of the gorse stem tissues approaches 0‰, suggesting that nitrogen is being symbiotically fixed from the atmosphere. Characterization
of the Bradyrhizobium isolated from gorse nodules shows similarities and distinctions to Bradyrhizobium isolated from the endemic legume koa (Acacia koa) within the same location. Population densities of the indigenous Bradyrhizobium are higher within the gorse rhizosphere than the kikuyu grass. Soil acidification, nutrient depletion, and symbiotic nitrogen
fixation distinguish gorse-infested areas from the surrounding uninfested areas. These observations suggest that gorse has
a competitive advantage over kikuyu grass under conditions of soil nutrient deficiency. 相似文献
17.
M. Rodríguez-Quijano M.T. Nieto-Taladriz J.M. Carrillo 《Genetic Resources and Crop Evolution》2001,48(6):599-607
A collection of 136 accessions of Aegilops umbellulata (39), Ae. comosa (75) and Ae. markgrafii (22) was analysed for high-molecular-weight (HMW) glutenin subunits composition. The homogeneity of the accessions was studied and 55.1% of the collection was homogeneous for HMW glutenin subunits (29 Ae. umbellulata, 33 Ae. comosa and 14 Ae. markgrafii). The HMW glutenin subunits of Ae. umbellulata are encoded by the Glu-U1 locus; in Ae. comosa results showed that this proteins are encoded at the 1M chromosome, and the locus was named Glu-M1. In Ae. markgrafii it was assumed that HMW glutenin subunits were encoded by an homoeologous locus and it was named Glu-C1. All the accessions of Ae. umbellulata and Ae. markgrafii expressed both, x-type and y-type subunits. Among the Ae. comosa accessions, only one expressed an x-type subunit alone. All the accessions of Ae. umbellulata and some of Ae. comosa had x-type glutenins of higher molecular weights than those commonly present in bread wheat. A total of 8 alleles were detected at the Glu-U1 locus, 11 at the Glu-M1 and 4 at the Glu-C1. The new HMW glutenin variation found in this work suggests their possible utilisation in breeding for wheat quality. 相似文献
18.
Ten leguminous trees, four exotic species (Australian Acacia) and six indigenous species (three Sahelian Acacia spp. and three Sesbania spp.), were grown for 4 months in a natural Sahelian soil inoculated with or without the endomycorrhizal fungus, Glomus intraradices. In control trials, the determinant factor structuring the soil nematode fauna was the plant species, related plants having a similar influence on the nematode community in the soil. Soil nematode abundance increased from exotic acacias (3.3 g-1 dry soil) to native acacias (11.5 g-1 dry soil) and Sesbania species (17.6 g-1 dry soil). Plant feeding nematodes (mainly Scutellonema and Tylenchorhynchus) were significantly less abundant under exotic acacias (1.4 g-1 dry soil) than under native acacias (7.2 g-1 dry soil) or Sesbania species (7.3 g-1 dry soil). Bacterial feeding nematode density increased from exotic acacias (1.2 g-1 dry soil) to native acacias (3.0 g-1 dry soil) and Sesbania species (7.7 g-1 dry soil) as total densities. However, the differences in the structure of the nematode communities between plant groups were suppressed in the presence of the mycorrhizal fungus. In fact, no difference in nematode densities remained between plant groups when G. intraradices developed in several dominant taxa belonging to different trophic groups, particularly: Tylenchorhynchus, Apelenchina, Cephalobus and Dorylaimoidea. This study clearly indicated that inoculation with the arbuscular mycorrhizal fungus G. intraradices diminished the plant-specific effect on the structure of the soil nematode community. 相似文献
19.
One hundred and forty-seven Chinese barley varieties maintained at the Gene Bank of the National Barley Improvement Centre,
Zhejiang, and 84 progenies from these varieties were tested at the seedling stage for their reaction to 32 selected pathotypes
of Blumeria graminis f. sp. hordei. Eighteen resistance spectra were identified comprising single or combined resistances from eight known (Ml(Bw), Ml(Ch), Mla7, Mla8, Mla9, Mla13, MlaRu4 and Mlg) and six unknown resistance genes. The most frequent gene was Ml(Bw), which was found in 69 varieties and previously detected in only a few European winter barley varieties. The genes Mla8 and Ml(Ch) were also often present, but other resistance genes were rare. After inoculation, considerably fewer pathogen colonies were
observed in ‘Aiganqi’ and one line of ‘Tong5’. Twenty varieties were composed of lines with different resistance genes. China
is likely to be a region of origin of the genes Ml(Bw), Mla7, as well as three unknown genes found in original landraces and perhaps another three unknown genes detected in cultivars
bred in China. The resistances of varieties from the Zhejiang province and those originating from 11 other Chinese provinces
were quite different. Unfortunately, none of the varieties are promising sources of resistance to powdery mildew and China
does not seem to be a region suitable for identifying such sources. 相似文献
20.
The effects of five agroforestry woody species (Dactyladenia barteri, Gliricidia sepium, Leucaena leucocephala, Senna siamea andTreculia africana) on the surface aasting activity ofHyperiodrilus africanus were studied in an Alfisol (Oxic Paleustalf) in southwestern Nigeria. Casting activity under the woody species decreased in the following order:Dactyladenia sp. (26.4 Mg ha-1 year-1)>Gliricidia sp. (24.4 Mg ha-1 year-1)>Treculia sp. (22.9 Mg ha-1 year-1)>Leucaena sp. (18.6 Mg ha-1 year-1)>Senna sp. (18.3 Mg ha-1 year-1). These differences in casting activity were partly explained by microclimatic effects. Irrespective of the woody species, the worm casts were higher in clay and silt contents, bulk density, water-stable aggregates, pH, organic C, exchangeable cations, effective cation exchange capacity, and extractable P levels than the corresponding surface soils. The woody species did affect the physicochemical properties and P sorption of the worm casts. The content of water-stable aggregates of worm casts decreased in the following order:Dactyladenia sp.>Treculia sp.>Senna sp.>Leucaena sp.>Gliricidia sp. Large differences in extractable P levels were observed.Senna sp. was associated with the highest extractable P level (11.5 mg kg-1) andTreculia sp. the lowest (4.9 mg kg-1). P sorption was highest on worm casts underDactyladenia sp. and lowest on those underTreculia sp. Without fertilizer application, there were no significant differences in the dry weight of maize grown in the different worm casts. With NPK applications, the dry weight of maize grown in worm casts associated withTreculia sp. was significantly lower than that of maize grown in the other worm casts, mainly due to the low extractable P level. Despite a high organic C and exchangeable K status, maize grown in the worm casts still responded significantly to N and K applications. The N uptake by maize grown in worm casts associated withTreculia sp. was lower than that in the other treatments. 相似文献