不同水淹下狗牙根-牛鞭草混作对植株生物量的影响

了解狗牙根(Cynodon dactylon)和牛鞭草(Hemarthria altissima)在不同水淹地区较优的种植方式对退化湿地的植被修复具有重要意义。设置4种不同水分条件,即对照组(CK)、水淹与干旱交替组(FD)、土壤表面水淹组(FL)和全淹组(SM),4种不同的植株密度(每盆分别种植1,2,4株或12株)和2种不同的种植方式(单作和混作),研究两物种在不同水淹条件下以不同方式和密度种植时的生物量变化。结果表明,水分、种植密度和种植方式均显著影响两物种的地上生物量和总生物量(P0.05)。CK和FD条件下,以中、高密度混作的狗牙根地上生物量和总生物量与单作相比显著下降(P0.05),牛鞭草在混作方式下的生物量与单作相比有了一定提高,其中在高密度混作情况下其生物量得到显著提高(P0.05)。在FL条件下,与单作相比,中、低密度混作的狗牙根和牛鞭草生物量均具有一定的上升。全淹条件下以中、低密度混作对狗牙根地上生物量和总生物量具有显著的促进作用(P0.05),对牛鞭草无显著差异(P0.05),高密度混作方式则对两物种生物量均无显著影响(P0.05)。随着水淹程度的增加,混作对狗牙根产生的生长抑制影响逐渐减弱。在长期浅水淹的地区,采取中、低密度混作将更有利于牛鞭草和狗牙根的长期共存。在较低海拔的全淹地区,采取高密度的牛鞭草-狗牙根混作方式将是更为理想的选择。     

间作植物和茬口对连作党参生长和品质产量的影响

选择两种茬口(轮作茬、连作茬)和6种植物材料(党参、大蒜、玉米、黄芪、苦参、向日葵),组成党参单作和间作6种种植模式,设置茬口和间作模式两因素田间随机区组试验,通过监测不同生长时期党参的生长指标(蔓长、主根长、主根直径、地下部分鲜干重)、根部产量及品质指标(根部多糖含量、炔苷含量、醇溶性浸出物含量和灰分含量)的变化衡量不同茬口和间作植物对党参连作障碍的缓解效应。结果表明：(1)轮作茬口下党参单作及各间作处理对党参生长、品质和产量的改善效果都较连作茬口下明显,且两茬口下各间作处理的改善效果都较党参单作明显。(2)与向日葵、大蒜和玉米间作处理对两茬口党参的主根长、主根直径、地下部分鲜干重的提升效果比党参单作和其余间作处理(与黄芪、苦参间作)更显著。(3)大蒜和向日葵间作处理能够显著提高两茬口党参根部产量,尤其大蒜表现最优,与其间作的轮作茬和连作茬党参分别较各自对照增产49.92%和22.55%。(4)与大蒜间作能有效提升两茬口党参根部多糖含量、炔苷含量和醇溶性浸出物的含量,党参单作和其余间作处理对两茬口连作党参的品质提升效果不及大蒜间作处理理想。研究发现,从党参长势及根部产量和品质综合分析,两茬口下党参与大蒜间作最有利于党参植株生长,能有效缓解党参连作障碍,并显著提高其药用部位的产量和品质,且轮作茬口下的提高效应更明显。     

Spatial ecology and conservation of two sloth species in a cacao landscape in limón,Costa Rica

The spatial ecology of sloths was studied in an agricultural landscape in Limón Province, Costa Rica. Two sloth species, the three-toed sloth (Bradypus variegatus) and the two-toed sloth (Choloepus hoffmanni), actively used and traveled through a cacao agroforest and its contiguous living fence rows and riparian forests. This agroecosystem was embedded in an agricultural landscape dominated by banana and pineapple plantations and pastures with dispersed trees. The two-toed sloth (C. hoffmanni) was found in 101 tree species and used 34 for food; the three-toed sloth (B. variegatus) was found in 71 tree species and used 15 for food. Choice of preferred species differed between the two sloth species. Trees commonly used by sloths for food and/or refuge in the cacao agroforest included Erythrina poeppigiana, Cecropia obtusifolia, Leucaena leucocephala; in the living fence rows, Cordia alliodora, Erythrina poeppigiana, Ocotea sinuata and Trophis racemosa; in the riparian forests, Coussapoa villosa, Cecropia obtusifolia, Hura crepitans, Pterocarpus officinalis and Spondias mombin; and in the pastures with dispersed trees, Cordia alliodora, Coussapoa villosa, Erythrina poeppigiana, Ocotea sinuata and Hura crepitans. This study demonstrates the importance of the cacao agroforest as well as arboreal elements in other land uses in providing resources for sloth conservation in a larger agricultural landscape.     

Temporal and spatial distribution of roots and competition for nitrogen in pea-barley intercrops – a field study employing 32P technique

Root system dynamics, productivity and N use were studied in inter- and sole crops of field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.) on a temperate sandy loam. A ³²P tracer placed at a depth of 12.5, 37.5, 62.5 or 87.5 cm was employed to determine root system dynamics by sampling crop leaves at 0, 15, 30 and 45 cm lateral distance. ¹⁵N addition was used to estimate N₂ fixation by pea, using sole cropped barley as reference crop. The Land Equivalent Ratio (LER), which is defined as the relative land area under sole crops that is required to produce the yields achieved in intercropping, were used to compare the crop growth in intercrops relative to the respective sole crops.The ³²P appearance in leaves revealed that the barley root system grows faster than that of pea. P uptake by the barley root system during early growth stages was approximately 10 days ahead of that of the pea root system in root depth and lateral root distribution. More than 90% of the P uptake by the pea root system was confined to the top 12.5 cm of soil, whereas barley had about 25–30% of tracer P uptake in the 12.5 – 62.5 cm soil layer. Judging from this P uptake, intercropping caused the barley root system to grow deeper and faster lateral root development of both species was observed. Barley accumulated similar amounts of aboveground N when grown as inter- and sole crop, whereas the total aboveground N acquired by pea in the intercrop was only 16% of that acquired in the pea sole crop. The percentage of total aboveground N derived from N₂ fixation in sole cropped pea increased from 40% to 80% during the growth period, whereas it was almost constant at 85% in intercropped pea. The total amounts of N₂ fixed were 95 and 15 kg N ha^–1 in sole cropped and intercropped pea, respectively. Barley was the dominant component of the pea-barley intercrop, obtaining 90% of its sole crop yield, while pea produced only 15% of the grains of a sole crop pea. Intercropping of pea and barley improved the utilization of plant growth resources (LER > 1) as compared to sole crops. Root system distribution in time and space can partly explain interspecific competition. The ³²P methodology proved to be a valuable tool for determining root dynamics in intercropping systems.     

果园间作模式下杏树与苜蓿的根系分布特征及其土壤理化性质研究

该研究采用田间小区试验,设计杏树(Prunus armeniaca)下清耕(CK)和杏树间作紫花苜蓿(T)2个处理,实地采集测定各样地不同土层紫花苜蓿的根系生物量以及杏树的侧根系生物量,并测定土壤pH、电导率及其土壤有机质和速效氮含量,分析果园间作模式下紫花苜蓿对果树侧根系垂直分布特征及其土壤理化性质的影响,为果园间作苜蓿模式的推广提供理论依据。结果表明:(1)CK与T处理下的杏树侧根生物量在土壤中的垂直分布都主要集中在20~60cm土层,其生物量分别为750.8g和737.6g,分别占总侧根生物量的64.4%和64.5%;紫花苜蓿根系生物量分布呈倒金字塔型,且主要分布在0~40cm土层(166.3g),其中0~20cm土层的根系生物量最高(97.4g),占根系总生物量的35.8%。(2)与CK处理相比,T处理可有效增加果园表层土壤的有机质含量、速效态氮含量、硝态氮含量和铵态氮含量,其中,在0~20cm土层分别显著增加17.1%、40.8%、28.5%和40.8%,在20~40cm土层分别显著增加36.1%、23.1%、60.2%和23.8%,并显著降低了表层土壤电导率,但对土壤pH无显著影响。研究认为,杏园间作牧草紫花苜蓿虽然杏树与苜蓿根系会发生较小资源的竞争,但有利于改善林下土壤的理化性质和养分状况,能够有效促进果树的生长发育。     

桐-药复合经营模式下泡桐丛枝菌根真菌群落结构特征

采用Illumina MiSeq高通量测序技术,研究江西鄱阳湖周边平原岗地的泡桐纯林及桐-药复合经营模式(泡桐-玉竹、泡桐-麦冬和泡桐-射干)下泡桐丛枝菌根真菌(arbuscular mycorrhizae fungi, AMF)群落结构特征。研究发现,泡桐AMF群落主要由球囊霉科、巨孢囊霉科、无梗囊霉科和多孢囊霉科组成,其中球囊霉科真菌占绝对优势,但不同科的相对丰度在不同经营模式下仍存在差异。与泡桐纯林相比,桐-药复合经营模式会降低泡桐菌根侵染率及AMF群落多样性。只有泡桐-射干经营模式中的泡桐含有多孢囊霉科真菌,且相对多度占2.73%。研究结果表明桐-药复合经营模式下中药材种类的差异会不同程度地改变泡桐AMF的群落结构。这为进一步研究桐-药复合经营模式下泡桐AMF的生态功能和资源利用提供了科学依据。     

Effects of intercropping white cabbage with clovers on pest infestation and yield

During two consecutive years the effects of intercropping fresh market white cabbage with two species of clover on pest populations and yield were studied. White cabbage cv. Minicole was intercropped withTrifolium repens (white clover) andTrifolium subterraneum (subterranean clover) as compared to the monocrop. During the season observations were made on pest population developments, especially ofMamestra brassicae L. (cabbage moth),Brevicoryne brassicae L. (cabbage aphid),Delia brassicae L. (cabbage root fly), and evaluation of caterpillar feeding injury. At harvest the yield in quantity and quality was determined to be able to assess the gross financial result. Intercropping effects in terms of suppression of oviposition and larval populations of various pests were found. Although no pesticides were used and competition reduced the weight, the quality of the intercropped cabbages lead to a better financial result compared to the monocropped cabbage crop. The results are discussed in the perspective of the practical implications in the context of IPM.     

Reduction of insect pest attack on sorghum and cowpea by intercropping

Two experiments to establish the relationship between insect suppression by intercropping and grain yield in sorghum and cowpea were conducted under field conditions. Treatments consisted of monocrops and intercrops of sorghum and cowpea and an additional pair of monocultures and mixtures protected by insecticides. Intercropping reduced the numbers of stem borer,Chilo partellus in sorghum and thrips,Megalurothrips sjostedti in cowpea. In the monocropped, unprotected sorghum, yield was reduced by 28% compared to the protected monocrop, while reduction in the unprotected intercropped sorghum was 15% compared to the protected intercrop. Similarly, in the unprotected cowpea, monocrop yield was reduced by 94% and intercrop yield was reduced by 51%. Thus, there are yield advantages under conditions where intercropping reduces insect pest density. Intercropping can form a component of an integrated pest management programme.     

Indigenous Knowledge and Management of Araucaria Araucana Forest in the Chilean Andes: Implications for Native Forest Conservation

Southern Chile experienced serious deforestation during the past century and it is projected that by the year 2025 Chile will be devoid of native forests. One of the most important endemic tree species of the country and at the same time one of the most endangered ones is Araucaria araucana (Mol.) C. Koch, the monkey-puzzle tree. It grows in the Andes Mountains, homeland of the indigenous Mapuche Pewenche people who depend on this tree. This paper is based on participatory field research with a Mapuche Pewenche community in the southern Chilean Andes on their ecological knowledge, values, use and management of the Araucaria araucana forest. It attempts to reveal how indigenous people and their knowledge contribute to the sustainable management of these forests. The paper (1) illustrates the complexity of indigenous ecological knowledge of Araucaria araucana and its efficacy in native forest management, (2) explores the link between the conservation and use of biodiversity by the indigenous people, and (3) provides answers relevant to native forest management and conservation strategies ex-situ and in-situ incorporating indigenous and scientific knowledge, thus providing a contribution towards integrated natural resource management.     

The system management approach of biological weed control: Some theoretical considerations and aspects of application

Theoretical considerations behind the system management approach of biological weed control are presented. These include, a part describing and explaining the effects of parasitic fungi on crop – weed competition, a part describing and explaining the epidemic spread of parasitic fungi on weeds, and a part relating crop – weed competition at the population level to epidemics. The theoretical framework developed may also provide a basis for the use of other natural enemies, like insects, for biological weed control following the system management approach. Aspects of application are discussed using data of the interaction between the annual weed Senecio vulgaris and the rust fungusPuccinia lagenophorae.     

Mangrove litter dynamics in La Mancha Lagoon,Veracruz, Mexico

In the mangrove surrounding the coastal lagoon of La Mancha, Veracruz, Mexico, we studied litter fall, litter standing crop, and turnover rates in four different mangrove settings, based on the ecological classification of Lugo and Snedaker (1974). We studied those three prominent ecological processes at the basin, fringe and riverine mangrove settings, being the last one a relict riverine stand. The aim was to describe and compare litter dynamics among mangrove types in a lagoon with an ephemeral inlet, as a way of understanding functional heterogeneity within this coastal ecosystem. The daily average values of litter fall were different (P < 0.01) among mangrove site basin I, formed by Avicennia germinans and Rhizophora mangle (2.35 g/m²/day); basin II, formed by Laguncularia racemosa, Avicennia germinans, and Rhizophora mangle (2.93 g/m²/day); fringe with Rhizophora mangle (2.13 g/m²/day); and relic riverine, also with R. mangle (4.70 g/m²/day). The amount of litter standing crop was different among sites (P < 0.001), and also between the dry and rainy season, for each mangrove type (P < 0.001). Turnover ratios were higher in basin I and basin II sites (6.34 and 7.44 times per year) than in relic riverine and fringe mangroves (1.49 and 2.39 times per year). Interstitial salinity and sediment nutrients varied among mangrove types and could influence litter production. Since this lagoon has an ephemeral inlet, continuous inundation throughout 7–8 months per year has an important effect on litter dynamics.     

The practical reason of weeds in Indonesia: Peasant vs. state views ofImperata andChromolaena

Peasant and state perceptions of two common weeds, Imperata cylindricaand Chromolaena odorata,are compared in four case study areas in Indonesia. Peasant perceptions are found to vary according to the similarity between these weeds plants and the fallow period vegetation in any given system of cultivation. All peasants attribute the origins of these weeds to external political authorities. State perceptions of both weeds are unvaryingly negative, based on its generally negative perception of systems of cultivation that employ fallow periods, and on its self-interest in expensive eradication programs and the alternate use of weed-covered lands. Both peasant and state perceptions of the two weeds are seen to be part of a broader structure of beliefs concerning not only plants and land, but also the relations between peasants and states themselves. This analysis demonstration that functional/ecological analysis is not restricted to local level relations, but can with equal validity be applied at the level of the state.     

Nitrogen fixation and N transfer from peanut to rice cultivated in aerobic soil in an intercropping system and its effect on soil N fertility

The novel cultivation of paddy rice in aerobic soil reveals the great potential not only for water-saving agriculture, but also for rice intercropping with legumes and both are important for the development of sustainable agriculture. A two-year field experiment was carried out to investigate the yield advantage of intercropping peanut (Arachis hypogaea L., Zhenyuanza 9102) and rice (Oryza sativa L., Wuyujing 99-15) in aerobic soil, and its effect on soil nitrogen (N) fertility. A pot experiment was also conducted to examine the N₂-fixation by peanut and N transfer from peanut to rice at three N fertilizer application rates, i.e., 15, 75 and 150 kg N ha^–1 using a ¹⁵N isotope dilution method. The results showed that the relative advantage of intercropping, expressed as land equivalent ratio (LER), was 1.41 in 2001 and 1.36 in 2002. Both area-adjusted yield and N content of rice were significantly increased in the intercropping system while those of peanut were not significantly different between intercropping and monocropping systems. The yields of rice grain and peanut, for example, were increased by 29–37% and 4–7% in the intercropping system when compared to the crop grown in the monocropping system. The intercropping advantage was mainly due to the sparing effect of soil inorganic N contributed by the peanut. This result was proved by the higher soil mineral N concentration under peanut monocropping and intercropping than under the rice monocropping system.%Ndfa (nitrogen derived from atmosphere) by peanut was 72.8, 56.5 and 35.4% under monocropping and 76.1, 53.3 and 50.7% under the intercropping system at N fertilizer application rates of 15, 75 and 150 kg ha^–1, respectively. The ¹⁵N-based estimates of N transfer from peanut (%NTFL) was 12.2, 9.2 and 6.2% at the three N fertilizer application rates. N transferred from peanut accounted for 11.9, 6.4 and 5.5% of the total N accumulated in the rice plants in intercropping at the same three N fertilizer application rates, suggesting that the transferred N from peanut in the intercropping system made a contribution to the N nutrition of rice, especially in low-N soil.     

Impact of habitat manipulation on mycopathogen, <Emphasis Type="Italic">Fusarium semitectum</Emphasis> to control <Emphasis Type="Italic">Scirtothrips dorsalis</Emphasis> and <Emphasis Type="Italic">Polyphagotarsonemus latus</Emphasis> of chilli

Environmental manipulation or conservation is one among several approaches evolved for harnessing the potentiality of entomopathogens in an integrated pest management. Cultural manipulation can permit the pathogen to reproduce more than usual or can preserve or enhance those already present. Among the key pest of chilli thrips, Scirtothrips dorsalis Hood (Thripidae: Thysanoptera) and broad mite, Polyphagotarsonemus latus [Banks] (Tarsonemoidea: Acari) are reported to cause the leaf curl in the leaves of chilli. Fusarium semitectum has infected the thrips and mites. The effectiveness of the mycopathogen, F. semitectum is chiefly influenced by the environmental conditions. Enhancing the microclimate the mycopathogen can be able to develop and buildup further. Chilli has been grown as sole crop, however companion crops such as sorghum, cotton, red gram, castor and maize were grown to understand the cropping system effect. Chilli-sorghum, chilli-cotton-chilli and chilli-red gram were the best cropping systems in terms of total chilli yield. The chilli-cotton-chilli cropping system ranked second with respect to benefit-cost ratio of 1:1 where as chilli-sorghum cropping system claimed the highest as 1.125:1. Interestingly, sorghum is not grown as a companion crop with chilli in Karnataka under rain fed conditions, where as chilli-cotton combination is a practice in many places of the state.     

Effect of five tree crops and a cover crop in multi-strata agroforestry at two fertilization levels on soil fertility and soil solution chemistry in central Amazonia

The spatio-temporal patterns of soil fertility and soil solution chemistry in a multi-strata agroforestry system with perennial crops were analysed as indicators for the effects of crop species and management measures on soil conditions under permanent agriculture in central Amazonia. The study was carried out in a plantation with locally important tree crop species and a leguminous cover crop at two fertilization levels on a xanthic Ferralsol. Soil fertility to 2 m soil depth was evaluated 3.5 years after the establishment of the plantation, and soil solution chemistry at 10, 60 and 200 cm soil depth was monitored over 2 years. Several soil fertility characteristics exhibited spatial patterns within the multi-strata plots which reflected the differing properties of the plant species and their management, including the fertilizer input. Significant differences between species could be detected to 150 cm depth, and between fertilization treatments to 200 cm depth. Favourable effects on nutrient availability in the soil were found for annatto (Bixa orellana) (P, K) and cupuaçu (Theobroma grandiflorum) (Ca, Mg) in comparison with peach palm (Bactris gasipaes) and Brazil nut (Bertholletia excelsa). Nutrient concentrations of the soil solution showed pronounced fluctuations in the topsoil, corresponding to fertilizer applications. Large nutrient concentrations in the soil solution were accompanied by increased concentrations of aluminium and low pH values, caused by exchange reactions between fertilizer and sorbed acidity and reinforced by the acidifying effect of nitrification. The soil solution under the leguminous cover crop Pueraria phaseoloides had relatively large N concentrations during periods when those under the tree crops were small, and this could partly explain why no yield responses to N fertilization were observed at this site.     

生态产品价值实现关键问题解决路径

量化、抵押、交易、变现是贯穿于生态产品价值实现全过程的重要环节，而难量化、难抵押、难交易、难变现（简称"四难"）是生态产品价值实现、生态文明建设亟待解决的关键问题。研究深入分析了"四难"问题的具体表征，包括产权界定不清、方法学研究不足、软硬件条件缺失、机制之间缺少联动等。为加强生态产品价值实现工作的统领作用，打通"绿水青山"同"金山银山"的双向转化通道，从整体布局、系统谋划角度出发，研究提出解决"四难"问题的基本路径：（1）通过构建"1+2+N"的政策框架体系，加强顶层设计，为生态产品价值实现试点奠定制度基础；（2）加强农特产品、资产权益类产品两类平台搭建，规范交易流程，健全交易网络，实现供需精准对接；（3）依据产权界定、可验证、可转让、可执行、政策连续性5项准则科学设计生态产品市场，实现生态产品交易市场化。此外，研究提出基于产业链金融链数据链协同深化生态产品价值实现问题研究。     

Mycotrophy of Annona cherimola and the morphology of its mycorrhizae

The mycotrophic character of Annona cherimola (Magnoliales), a tropical/subtropical plantation crop of interest, is described for the first time. This crop seems to depend on mycorrhizae (arbuscular) for optimal growth, with Glomus deserticola being the most effective endophyte tested. Study of the morphology of the arbuscular mycorrhizae in Annona roots showed exclusively intracellular hyphal development, with cell-to-cell fungal passage and an abundance of arbuscules and coiled hyphae within cells. Intercellular distributive hyphae were not observed. The morphology and the pattern of spread of the mycorrhizal colonization were similar for the different endophytes involved and appeared to be dependent on the host root. Such features of mycorrhizal colonization are characteristic of host species lacking intercellular air channels and have been described for some species of ecological interest, but they are not commonly noted in the mycorrhizal literature, especially that dealing with crop species. Some ecophysiological consequences of this pattern of colonization are discussed.     

Relative uptake of32P by cassava,banana, elephant foot yam and groundnut in intercropping systems

Absorption of applied³²P by the treated as well as neighbouring plants in two- and three-crop intercropping systems involving cassava (Manihot esculenta Crantz), banana (Musa (AAB) Mysore), elephant foot yam (Amorphophallus campanulatus Blume) and groundnut (Arachis hypogaea L.) was studied in field trials. Radiophosphorus applied to the root zone of one of the component species in the mixed systems was found to be absorbed not only by the treated plant but also by the neighbouring plants. Banana was the most dominant species in the cassava-banana-elephant foot yam intercropping system and accumulated the major portion of the radioactivity recovered in the whole system. Cassava planted on raised mounds absorbed³²P from the root zones of elephant foot yam and banana growing in the interspaces. Absorption of³²P from cassava mounds by elephant foot yam was negligible.In cassava-groundnut intercropping system, cassava was the dominant component accumulating about 96 to 99 per cent of the total³²P recovery in the system when the radiolabel was applied to cassava and about 48 to 88 per cent when applied to the intercrops depending on whether cassava was planted on paired row-ridge, mound or flat bed. The groundnut was able to absorb only negligible quantity of³²P from cassava root zone. The absorption of³²P by treated groundnut was highest in paired-row ridge method of planting and lowest in flat bed method of planting.     

福建山区混农林业的传统知识

前言本研究旨在探讨中国的杉农们进行杉农间作时做各项决策的传统依据。认识生态人类学的理论文化观点是本研究的理论基础。基于这一观点,人类面临生存环境挑战时,具有前科学的本领。前科学即由可见结果推理不可见原因的能力及综合推测自然界明确构序的能力(Bloom,1987)。前科学先于科学方法的形成,也许是现代人类必不可少甚至明显的特征。根据上述观点和生态人类学家所创立的三     

Nitrogen Fixation of Faba Bean (Vicia faba L.) Interacting with a Non-legume in Two Contrasting Intercropping Systems

A field experiment was carried out to quantify biological nitrogen fixation (BNF) using the ¹⁵N isotope natural abundance method in maize (Zea mays L.)/faba bean (Vicia faba L.) and wheat (Triticum aestivum L.)/faba bean intercropping systems. Faba bean was yielding more in the maize/faba bean intercropping, but not in the wheat/faba bean intercropping. Biomass, grain yield and N acquisition of faba bean were significantly increased when intercropped with maize, and decreased significantly with wheat, irrespective of N-fertilizer application, indicating that the legume could gain or lose productivity in an intercropping situation. There was yield advantage of maize/faba bean intercropping, but no in wheat/faba bean intercropping. The grain yield of the faba bean intercropped with maize was greater than that of faba bean monoculture due to increases of the stems per plant and the pods per stem of faba bean. N fertilization inhibited N fixation of faba bean in maize/faba bean and wheat/faba bean intercropping and faba bean monoculture. The responses of different cropping systems to N-fertilizer application, however, were not identical, with competitive intercropping (wheat/faba bean) being more sensitive than facilitative intercropping (maize/faba bean). Intercropping increased the percentage of N derived from air (%Ndfa) of the wheat/faba bean system, but not that of the maize/faba bean system when no N fertilizer was applied. When receiving 120 kg N/ha, however, intercropping did not significantly increase %Ndfa either in the wheat/faba bean system or in the maize/faba bean system in comparison with faba bean in monoculture. The amount of shoot N derived from air (Ndfa), however, increased significantly when intercropped with maize, irrespective of N-fertilizer application. Ndfa decreased when intercropped with wheat, albeit not significantly at 120 kg N/ha. Ndfa was correlated more closely with dry matter yield, grain yield and competitive ratio, than with %Ndfa. This indicates that that total dry matter yield (sink strength), not %Ndfa, was more critical for the legume to increase Ndfa. The results suggested that N fixation could be improved by yield maximization in an intercropping system.