小麦/蚕豆间作条件下小麦的氮、钾营养对小麦白粉病的影响

通过小麦/蚕豆间作盆栽试验,研究比较了单作和间作条件下不同氮、钾营养水平对小麦氮、钾养分吸收和小麦白粉病发生的影响。结果表明:小麦蚕豆间作提高小麦子粒产量74.7%～133.9%,低氮条件下,间作提高小麦氮吸收量14.7%～169%;在高氮条件下,间作提高氮吸收量的优势降低;间作提高小麦钾吸收量32%～69%,增施钾肥提高小麦钾吸收量25.5%～57.3%。小麦间作蚕豆能明显减轻小麦白粉病的发生,间作平均防效达42.1%～83.1%;小麦白粉病的发生与小麦茎叶的氮吸收量呈显著正相关关系,r=0.623*～0.702*.*。     

木薯间作糯玉米的高产高效模式分析

为研究不同栽种规格的木薯间作糯玉米模式和发掘高产高效间作模式,对木薯净作,糯玉米净作和8种木薯间作糯玉米模式进行了鲜薯产量和经济效益的研究。结果表明：木薯间作糯玉米模式是可行的,体现出明显的间作优势。发现不同间作模式的经济效益不同,其中处理9(大行距100 cm,小行距70 cm)的鲜薯产量(51 274.36 kg/hm2)最高,处理4(行距100 cm)的经济效益(52 794.15元/hm2)最高,处理9的经济效益(46 556.97元/hm2)排第3位。综合评价认为,处理9的木薯间作糯玉米模式最合理。试验结果为进一步推广高产高效木薯间作糯玉米模式提供了有力依据。     

施氮对蚕豆/玉米间作系统蚕豆农艺性状及结瘤特性的影响

 【目的】旨在探明施氮对蚕豆/玉米间作体系蚕豆农艺性状和结瘤特性的影响,为河西走廊灌区豆科/禾本科间作体系氮素管理和高产高效提供科学依据。【方法】于2006-2007年在甘肃省农科院白云试验站分别采用裂区设计和原位根系行分隔法设计了蚕豆/玉米间作体系的氮梯度试验和根系分隔微区试验,研究不同氮水平下蚕豆/玉米种间互作对蚕豆农艺性状和结瘤特性的影响。【结果】施氮对蚕豆地上部生长和产量性状均无显著影响,但显著地抑制了蚕豆结瘤,产生了“氮阻遏”效应,且随着施氮量增加和蚕豆生长,“氮阻遏”效应愈加明显。随着蚕豆与玉米两种作物生长发育,作物根系相互促进作用逐渐增强,显著地促进了根瘤发育,且产生了“减缓效应”,平均为14.4%;根系互作相对于无根系互作处理蚕豆结瘤平均增加10.2%。【结论】蚕豆/玉米种间根系相互作用促进了蚕豆结瘤,减缓了”氮阻遏”效应,显著提高了蚕豆产量性状而实现了蚕豆增产。     

桉-农间作系统小气候特征研究

对桉农间作系统内一年生间作物3个生长阶段的光强、温度以及相对湿度等小气候因子进行观测,结果表明:间作带上的平均光强为42 000～59 000 lx,相对光强达到76.7%～78.8%,减弱幅度＜25%,可以满足一年生间作物生长需求;桉农间作系统在低温天气,间作带可增温12.3%～27.9%;在高温条件下,间作系统降温幅度在2.97%～11.6%;并可降低最高地温7.9%;降低常风39%;白天平均相对湿度比对照农地的相对湿度最大提高4.44%,平均提高1.5%.因此,桉农间作具有明显的防风、降温、增湿和保持土壤湿度作用,这对改善间作区田间小气候,促进农业的高产、稳产具有重要意义.     

The Effects of Intercrop Spacing Patterns on the Silage Yield of Maize and Soybean

The effects of intercrop spacing patterns on the silage yields of both maize (lea mays L.) and soybean (Glycine max [L.] Merr.) were examined from 1985 to 1987. Dwarf maize was intercropped with nonnodulatmg or nodulating soybean in the spacing patterns, S_40same (two crops in the same row, 40 cm row width) and S_20ait or S_40ak (two crops in alternate rows, 20 cm or 40 cm row width, respectively). Tall maize was intercropped with nodulating soybean in S_40sames S_40alt and S_40pair (maize in 40 cm paired rows, soybean rows 20 cm outside each maize row and 80 cm from the next set of four rows) at 0 or 60 kg N ha⁻¹ and at population densities of 67% maize: 67% soybean or 50 % maize: 50% soybean. Maize and soybean were also intercropped and stripcropped on a farm-scale. The only difference between intercrops arranged in the same rows versus those in alternate rows was that the average soybean protein yields were higher in S_40same than in S_40alt. In 1986, the S_40alt maize-soybean intercrops produced higher maize yields, total biomass yields and Land Equivalent Ratios (LERs) than in S_40pirs, and in 1987, these responses were higher in intercrops than in stripcrops. In 1986, at 0 kg N ha⁻¹, the soybean biomass and protein yields were lower in S_40alt, than in S_40pairs and in 1987, these responses were lower in intercrops than in stripcrops.     

棉苜间作棉田天敌群落结构与动态及其对棉蚜的控制效应

采取不同的棉苜间作方式,研究了棉苜间作棉田天敌群落结构及种群动态规律、棉蚜与天敌的消长动态,以及棉苜间作对棉田蚜虫的控制效应。与常规单种棉田相比,间作苜蓿棉田内的瓢虫、蜘蛛、草蛉种群数量大幅度增长,尤以每隔1膜间作75cm苜蓿带处理区为甚,分别增长了318.0%、120.9%和79.6%。间作或邻作苜蓿的棉田天敌群落的物种丰富度、丰富度指数及多样性指数均高于常规单种棉田,表明间作和邻作苜蓿带并适时刈割,可以提高棉田内天敌群落的丰富度和多样性。刈割苜蓿带对棉田棉蚜及瓢虫类、蜘蛛类和草蛉类天敌的数量动态影响较大。在棉蚜上升初期刈割苜蓿带,使棉田内瓢虫类、蜘蛛类和草蛉类天敌数量急剧上升,棉蚜数量大幅下降,从而有效地控制了棉田棉蚜的暴发。     

花生间作大葱条件下氮磷钾肥配施效应的研究

采用"3414"肥料试验,探索花生间作大葱条件下氮磷钾配施效应,经过肥料效应函数拟合,研究了氮磷钾肥不同比例配合施用对花生间作大葱产量的影响,研究结果表明:氮磷钾肥配施能显著提高大葱产量,在一定范围内随着施氮量的增加大葱的产量升高,各施肥处理产量比不施肥处理增产5.50%~82.00%;同时,氮磷钾肥配施能够显著提高花生产量,各施肥处理产量较不施肥处理增产22.83%~48.73%,氮磷钾3种肥料对花生产量的效应函数拟合性较好。综合3类7种肥料效应函数,在花生间作大葱条件下高产推荐施肥量为:N 157.2kg/hm2、P2O5143.1kg/hm2、K2O 125.8kg/hm2,肥料用量比例为N:P2O5:K2O是1.25:1.14:1。     

Dry-season sesbania fallows and their influence on nitrogen availability and maize yields in Malawi

Nitrogen deficiency is widespread in southern Africa, but inorganic fertilizers are often unaffordable for smallholder farmers. Short-duration leguminous fallows are one possible means of soil fertility restoration. We monitored preseason topsoil (0 to 20 cm) ammonium and nitrate, fallow biomass production and grain yields for three years in a relay cropping trial with sesbania [Sesbania sesban (L.) Merr.] and maize (Zea mays L.). Sesbania seedlings were interplanted with maize during maize sowing at 0, 7400 or 14,800 trees ha^–1, in factorial combination with inorganic N fertilizer at 0 or 48 kg N ha^–1 (half the recommended rate). After maize harvest, fallows were allowed to grow during the seven-month dry season, and were cleared before sowing the next maize crop. Both sesbania fallows and inorganic N fertilizer resulted in significantly greater (P < 0.01 to 0.05) preseason topsoil nitrate-N than following unfertilized sole maize. In plots receiving no fertilizer N, preseason topsoil inorganic N correlated with maize yield over all three seasons (r ² = 0.62, P < 0.001). Sesbania fallows gave significantly higher maize yields than unfertilized sole maize in two of three years (P < 0.01 to 0.05). Sesbania biomass yields were extremely variable, were not significantly related to sesbania planting density, and were inconsistently related to soil N fractions and maize yields. Short-duration fallows may offer modest yield increases under conditions where longer duration fallows are not possible. This gain must be considered against the loss of pigeonpea (Cajanus cajan L. Millsp) harvest in the similarly structured maize-pigeonpea intercrop common in the region.This revised version was published online in November 2005 with corrections to the Cover Date.     

窄冠黑杨窄冠黑白杨的选育(I)田间试验及结果分析

通过杂交育种，苗期选择，无性系测定，选出了6个窄冠黑杨，1个窄冠黑白杨无性系。前者生长量接近对照I-69/55和中林46，冠幅比对照小1/2—1/3，耐盐碱能力较强，容易扦插繁殖，造林成活率高。后者生长量与窄冠白杨3号相当，冠幅比窄冠白杨3号更窄，繁殖方式同一般毛白杨。两类品种均为适合于农田林网及农林间作的杨树新品种。     

A conceptual framework and an empirical test of complementarity and facilitation with respect to phosphorous uptake by plant species mixtures

Plant species have different traits for mobilizing sparingly soluble phosphorus (P) resources, which could potentially lead to overyielding in P uptake by plant species mixtures compared to monocultures due to higher P uptake as a result of resource (P) partitioning and facilitation. However, there is circumstantial evidence at best for overyielding as a result of these mechanisms. Overyielding (the outcome) is easily confused with underlying mechanisms because of unclear definitions. We aimed to define a conceptual framework to separate outcome from underlying mechanisms and test it for facilitation and complementarity with respect to P acquisition by three plant species combinations grown on four soils. Our conceptual framework describes both mechanisms of complementarity and facilitation and outcomes (overyielding of mixtures or no overyielding) depending on the competitive ability of the species to uptake the mobilized P. Millet/chickpea mixtures were grown in pots on two calcareous soils mixed with calcium-bound P (CaP) and phytate P (PhyP). Cabbage/faba bean mixtures were grown on both acid and neutral soils mixed with P-coated iron (hydr)oxide (FeP) and PhyP. Wheat/maize mixtures were grown on all four soils. Rhizosphere carboxylate concentration and acid phosphatase activity (mechanisms) as well as plant P uptake and biomass (outcome) were determined for monocultures rhizosphere and species mixtures. Facilitation of P uptake occurred in millet/chickpea mixtures on one calcareous soil. We found no indications for P acquisition from different P sources, neither in millet/chickpea, nor in cabbage/faba bean mixtures. Cabbage and faba bean on the neutral soil differed in rhizosphere acid phosphatase activity and carboxylate concentration, but showed no overyielding. Wheat and maize, with similar root exudates, showed overyielding (the observed P uptake being 22% higher than the expected P uptake) on one calcareous soil. We concluded that although differences in plant physiological traits (root exudates) provide necessary conditions for complementarity and facilitation with respect to P uptake from different P sources, they do not necessarily result in increased P uptake by species mixtures, because of the relative competitive ability of the mixed species.