Intercropped Wheat Research Articles

Nitrogen and phosphorus economy of a legume tree-cereal intercropping system under controlled conditions

Considerable amounts of nitrogen (N) and phosphorus (P) fertilizers have been mis-used in agroecosystems, with profound alteration to the biogeochemical cycles of these two major nutrients. To reduce excess fertilizer use, plant-mediated nutrient supply through N2-fixation, transfer of fixed N and mobilization of soil P may be important processes for the nutrient economy of low-input tree-based intercropping systems. In this study, we quantified plant performance, P acquisition and belowground N transfer from the N2-fixing tree to the cereal crop under varying root contact intensity and P supplies. We cultivated Acacia senegal var senegal in pot-culture containing 90% sand and 10% vermiculite under 3 levels of exponentially supplied P. Acacia plants were then intercropped with durum wheat (Triticum turgidum durum) in the same pots with variable levels of adsorbed P or transplanted and intercropped with durum wheat in rhizoboxes excluding direct root contact on P-poor red Mediterranean soils. In pot-culture, wheat biomass and P content increased in relation to the P gradient. Strong isotopic evidence of belowground N transfer, based on the isotopic signature (δ15N) of tree foliage and wheat shoots, was systematically found under high P in pot-culture, with an average N transfer value of 14.0% of wheat total N after 21days of contact between the two species. In the rhizoboxes, we observed limitations on growth and P uptake of intercropped wheat due to competitive effects on soil resources and minimal evidence of belowground N transfer of N from acacia to wheat. In this intercrop, specifically in pot-culture, facilitation for N transfer from the legume tree to the crop showed to be effective especially when crop N uptake was increased (or stimulated) as occurred under high P conditions and when competition was low. Understanding these processes is important to the nutrient economy and appropriate management of legume-based agroforestry systems.

Pea–wheat intercrops in low-input conditions combine high economic performances and low environmental impacts

Intensive agriculture ensures high yields but can cause serious environmental damages. The optimal use of soil and atmospheric sources of nitrogen in cereal–legume mixtures may allow farmers to maintain high production levels and good quality with low external N inputs, and could potentially decrease environmental impacts, particularly through a more efficient energy use. These potential advantages are presented in an overall assessment of cereal–legume systems, accounting for the agronomic, environmental, energetic, and economic performances. Based on a low-input experimental field network including 16 site-years, we found that yields of pea–wheat intercrops (about 4.5Mgha−1 whatever the amount of applied fertiliser) were higher than sole pea and close to conventionally managed wheat yields (5.4Mgha−1 on average), the intercrop requiring less than half of the nitrogen fertiliser per ton of grain compared to the sole wheat. The land equivalent ratio and a statistical analysis based on the Price's equation showed that the crop mixture was more efficient than sole crops particularly under unfertilised situations. The estimated amount of energy consumed per ton of harvested grains was two to three times higher with conventionally managed wheat than with pea–wheat mixtures (fertilised or not). The intercrops allowed (i) maintaining wheat grain protein concentration and gross margin compared to wheat sole crop and (ii) increased the contribution of N2 fixation to total N accumulation of pea crop in the mixture compared to pea sole crop. They also led to a reduction of (i) pesticide use compared to sole crops and (ii) soil mineral nitrogen after harvest compared to pea sole crop. Our results demonstrate that pea–wheat intercropping is a promising way to produce cereal grains in an efficient, economically sustainable and environmentally friendly way.

Water use efficiency of winter wheat in ridge cultured wheat||spinach-tomato cropping system

垄作小麦(<i>Triticum aestivum</i> L.)和间套作技术是我国华北地区农业生产中的重要种植模式之一。本研究结合华北地区严重缺水的实际, 以平作小麦、垄作小麦作为复种模式中冬小麦的对照, 平作菠菜(<i>Spinaciaoleracea</i> L.)复种番茄(<i>Lycopersicon esculentum</i> Miller)为复种模式中菠菜和番茄的对照(平作采用漫灌, 起垄栽培作物均采用沟内灌水), 研究了垄作小麦间作菠菜复种1 季番茄这一间套模式中冬小麦的产量和水分利用效率。结果表明, 垄作小麦及垄作小麦间作菠菜复种番茄比平作小麦减产11%, 减产是由于没能充分发挥边际效应而使得穗数降低。3 种模式的水分利用效率比较表明, 平作小麦水分利用效率最高, 其次是垄作小麦, 间套作条件下的垄作小麦水分利用效率最低。垄作小麦的水分利用效率低于平作小麦, 是因为冬小麦对沟内水分利用不充分, 而试验中降水、灌溉水主要存留于沟内。在垄作小麦沟内套种菠菜, 获得了与单作菠菜相同的产量, 说明冬小麦不影响菠菜产量。收获菠菜后接茬移栽番茄, 移栽时间应尽量后移, 可减少共生期, 便于田间管理和番茄生长。小麦、菠菜、番茄间作套种, 如果品种选择合理、时机恰当, 可以在小麦等粮食作物不减产的情况下, 增收2 茬蔬菜。

Ground Beetle (Coleoptera: Carabidae) Diversity, Activity Density, and Community Structure in a Diversified Agroecosystem

Diversity and abundance of ground beetles (Coleoptera: Carabidae) can be enhanced in vegetable and field intercropping systems, but the complexity of polycultures precludes the application of generalized assumptions of effects for novel intercropping combinations. In a field experiment conducted at Lacombe and Ellerslie, Alberta, Canada, in 2005 and 2006, we investigated the effects of intercropping canola (Brassica napus L.) with wheat (Triticum aestivum L.) on the diversity and community structure of carabid beetles, and on the activity density responses of individual carabid species. Shannon-Wiener diversity index scores and species evenness increased significantly as the proportion of wheat comprising total crop plant populations increased in one site-year of the study, indicating a positive response to enhanced crop plant species evenness in the intercrops, and in that same site-year, ground beetle communities in intercrops shifted to more closely approximate those in wheat monocultures as the percentage of wheat in the intercrops increased. Individual carabid species activity densities showed differing responses to intercropping, although activity densities of some potential root maggot (Delia spp.) (Diptera: Anthomyiidae) predators were greater in intercrops with high proportions of wheat than in canola monocultures. The activity density of Pterostichus melanarius (Illiger), the most abundant species collected, tended to be greater in canola monocultures than high-wheat intercrops or wheat monocultures. We conclude that intercrops of canola and wheat have the potential to enhance populations of some carabid species, therefore possibly exerting increased pressure on some canola insect pests.

Relative Effectiveness of Various Amendments in Improving Yield and Nutrient Uptake under Organic Crop Production

In organic farming, artificial/synthetic inorganic fertilizers/chemicals are not applied to increase crop yields, but adequate amounts of nutrients are essential for sustainable high production from agricultural crops. Two 3-year (2008 - wheat, 2009 – pea, and 2010 - barley) field experiments were conducted on certified organic farms near Spalding (Dark Brown Chernozem – Typic Haploboroll) and Star City (Gray Luvisol – Typic Haplocryalf) in northeastern Saskatche-wan to determine the relative effectiveness of various organic amendments (compost, alfalfa pellets, wood ash, rock phosphate, Penicillium bilaiae, MykePro, or gypsum), and intercropping of non-legume (wheat, barley) and legume (pea) annual crops on seed yield, total biomass yield (TBY) and nutrient uptake in seed + straw of wheat, pea and barley. In 2008, seed yield, TBY and nutrient uptake of wheat increased (but small) with compost and alfalfa pellets. In 2010, seed yield, TBY and nutrient uptake of barley increased substantially with compost and alfalfa pellets and moderately with wood ash. Other amendments had little or no effect on crop yield and nutrient uptake. In 2009, there was no beneficial effect of any amendment on yield and nutrient uptake of pea, most likely due to fixation of N which is the most limiting nutrient in these soils. Intercropping of wheat or barley with pea produced greater seed yield and nutrient uptake per unit land area basis compared to wheat or barley grown as sole crops in most cases. In conclusion, our results suggest potential benefits in improving yield and nutrient uptake of wheat and barley from compost, alfalfa pellets and possibly wood ash, most likely by preventing deficiencies of some nutrients, especially N, lacking in these soils under organic farming. Our findings also suggest the need for future research to determine the feasibility of rock phosphate, Penicillium bilaiae, MykePro, gypsum or other amendments in preventing P and/or S deficiency in organic crops using soils extremely deficient in these nutrients.

施氮量对小麦/玉米带田土壤水分及硝态氮的影响

The purpose of the study was to analyze the dynamic impacts of vary amount of N-fertilization(0、210、420and 630 kg /hm2) on the soil water content and NO-3-N content from the field of wheat-corn intercrop field.The data showed that the total kernel yield of intercropping wheat and maize increased with the increase of nitrogen supply,it could reach as high as 13661—14668 kg /hm2 when 420 kg /hm2 of N-fertilizer applied.When the nitrogen supply is 420 kg/hm2,the water use efficiency of the filed can reach 21.25 kg · hm-2 · mm-1.After wheat was harvested,the soil water content in the layer of 0—120cm depth decreased with the increased amount of nitrogen supply,while the content of nitrate nitrogen increased with the increased amount of nitrogen supply.Moreover,the soil nitrate nitrogen content of the topsoil(0—60cm) was significantly higher than that of the soil layer at the depth of 60—200cm.The dynamic changes of soil nitrate content during the whole growth season of intercropped wheat and maize could be summarized into a double-peaked curve.When the 0 and 210 kg/hm2 nitrogen supply were applied,the first and second peaks appeared at the wheat trefoil stage and the maize large bell stage,respectively.However,the first peak appeared at the wheat flagging stage when 420 and 630 kg /hm2 nitrogen supply applied;and the second peak appeared at the maize large bell stage and the grain-filling stage when 420 and 630 kg/hm2 nitrogen supply applied,respectively.Therefore,the results suggested that the high-yield nitrogen supply was 420 kg/hm2 for the wheat and maize intercropping cultivation mode,With this amount of nitrogen supply,the accumulation and transformation of the soil nitrate nitrogen could be reduced,and therefore fulfill the purpose of the efficiency and environmental safety.

Intercropping of wheat (Triticum aestivum) and bean (Vicia faba): Effects of complementarity and competi-tion of intercrop components in resource con-sumption on dry matter production and weed growth

Wheat ( Triticum aestivum ) and bean ( Vicia faba L.) sole crops and their mixture in three planting pattern (M 1: alternate-row intercrop, M 2: within-row intercrop, M 3: mixed intercrop) were used to investigate the amount of resource consumption in terms of photosynthetically active radiation (PAR) interception, water and nutrient uptake. The experiment was carried out as randomized complete block design with four replications. The results show that intercropping systems had a significant effect on environmental resources consumption, where intercropping systems had more light interception and water, and nutrient uptake compared to sole crops, suggesting the complementarity effect of intercropping components in resources consumption. The ability of wheat and bean was different in intercropping systems in absorbing nutrients because of their differences in root morphology and cation exchange capacity. Regarding weed suppressions, intercrops were more effective than wheat sole crops, which were related to lower availability of environmental resources for weeds in intercropping systems.

Effect of phosphorus application and strip-intercropping on yield and some wheat- grain components in a wheat/maize/potato intercropping system

Intercropping of bread wheat (Triticum aestivum L.), maize (Zea mays L.) and potato (Solanum tuberosum)has been practiced in North-West China in the last several decades; however, the effects of this intercropping and phosphorus addition on crop yield and some wheat-grain components have not been adequately investigated. A 2-year field experiment was conducted from 2002 to 2003 in irrigated areas in North-West of China to investigate how phosphorus fertilizer application and intercropping of wheat/maize/potato impact on the crop yield and wheat-grain components such as protein content, wet gluten and sodium dodecyl sulphate (SDS) sedimentation. The results indicated that bread wheat and maize achieved higher yields in the intercropping system than in the monoculture system over the 2 years, and the wheat-grain had higher protein content, wet gluten and sodium dodecyl sulphate (SDS) sedimentation in the intercropping system than in the monoculture system. Better utilization of resources through border row effect and preventing competition between species over growing period have been indicated as the major factors contributing to the increased crop yield and wheat-grain components. Phosphorus application significantly increased crop yields and improved wheat-grain components; however, the optimal application rate for achieving highest protein content was at 150 kg ha-1. The practical implication of the present study was that to obtain good yield and better wheat-grain components, a combination of intercropping and application of phosphorus fertilizer at a rate of approximately 150 kg ha-1 was found as one of the most practical options. Key words: Border-row effect, intercropping, phosphorus, wheat-grain components, wheat/maize/potato, yield.

Yield and competitive response of intercropped wheat and faba-bean to water and allelochemical dose

Academic evidence showing negatively effects of allelochemicals on optimized intercropping systems are largely lacking.To that end,a pot experiment was conducted to study the mechanism of allelopathy in intercropping systems.Three modes of crop-ping systems(monocropped wheat,monocropped faba-bean and intercropped wheat/faba-bean) were designed with three irrigation rates(45%,60% and 75% of field capacity).The effects of irrigation rates and 3-methyl-phenol on yields of the different cropping systems were analyzed.Competition between wheat and faba-bean in the wheat/faba-bean intercropping system was also determined.Results indicated that intercropping significantly influenced the biological and economic yields of wheat.Compared with mono-cropped wheat,yield of intercropped wheat increased under irrigation rates of 60% and 75% filed capacity.However,the reverse was noted in economic yield under irrigation rate of 45% filed capacity.The yield of intercropped faba-bean was significant higher than that of the monocropped faba-bean under different irrigation rates.Allelopathic effects of 3-methyl-phenol on the yield of wheat and faba-bean were negative.Intercropping mitigated the degree of negative allelopathic effect on faba-bean.3-methyl-phenol signifi-cantly enhanced the competitive capacity of wheat over faba-bean in intercropped systems.The competitive capacities of wheat over faba-bean in intercropping system with 3-methyl-phenol were 24.82%,19.26% and 79.30% higher than those of intercropping sys-tems without 3-methyl-phenol under irrigation rates of 45%,60% and 75% of field capacity,respectively.On the other hand,in-creasing irrigation rate weakened the competitive capacity of wheat in intercropping systems.The competitive capacities of wheat over faba-bean in their intercropping systems with and without 3-methyl-phenol under 75% irrigation rates were 158.08% and 79.67% lower than that under 45% irrigation rate,respectively.

Water use and yield of wheat/maize intercropping under alternate irrigation in the oasis field of northwest China

A field experiment was carried out to investigate the effects of alternate irrigation (AI) on the yield, water use and water use efficiency (WUE) of wheat ( Triticum aestivum L.)/maize ( Zea mays L.) intercropping system in an oasis region of northwest China in 2006–2008. Three planting patterns, i.e., sole wheat, sole maize and wheat/maize intercropping. Three irrigation levels were applied for each treatment during 3 years. Results showed that land use efficiency of wheat and maize was significantly enhanced by intercropping system; land equivalent ratio (LER) of wheat/maize intercropping system in different treatments was all greater than 1.0. Moreover, significant difference in grain yield was observed between intercropping treatment and sole cropping treatment, in which the yield of intercropped wheat was 55.37–74.88% of sole wheat, and intercropped maize was 66.63–78.87% of sole maize. Wheat/maize intercropping treatments increased water use by 1.8–16.4% than half of the total water use of sole-cropping wheat and maize. Compared to sole cropping wheat treatments, wheat/maize intercropping with alternate irrigation significantly improved water use efficiency (WUE) by 30.5–57.7%, 55.5–71.4% and 12.0–19.8%, and increased by 32.7–37.8%, 9.5–15.8% and 4.0–20.8% than sole cropping maize treatments in 2006–2008, respectively. Our results suggest that AI should be a useful water-saving irrigation method on wheat/maize intercropping in arid oasis field where intercropping planting is decreased because of limited water resource.

Combining intercropping with semiochemical releases: optimization of alternative control of Sitobion avenae in wheat crops in China

Overreliance on pesticides has large environmental and human health costs that compel researchers and farmers to seek alternative management tactics for crop pests. For insect pests, increasing crop species diversity via intercropping and using semiochemicals to alter local arthropod populations have separately proven effective at reducing pest densities. Here, we combine these two tactics in an effort to gain better control of Sitobion avenae (Fabricius) (Hemiptera: Aphididae), the English grain aphid, a major pest of cereal production worldwide. We conducted field experiments over 2 years testing the effectiveness of combining intercropping of wheat and oilseed rape with release of methyl salicylate (MeSA). We found that maximum and mean aphid densities were highest in wheat monocultures, significantly lower in intercropped plots and MeSA plots, and lowest when intercropping and MeSA release were combined by obtaining highest densities of predatory lady beetles and parasitoids rates. Importantly, grain yield and quality showed a similar pattern: they were highest for combined intercropped/MeSA plots, intermediate in plots with intercropping or MeSA alone, and lowest in control monoculture plots. Our results suggest that combining these two tactics holds significant promise for improved management of aphid populations and emphasize the need to integrate alternative pest control approaches to optimize sustainable insect pest management.

Effects of crop mixtures on chocolate spot development on faba bean grown in mediterranean climates

Chocolate spot incited by Botrytis fabae is a serious faba bean disease of worldwide distribution. The increasing interest in sustainable tools for disease control, together with the lack of sufficient levels of genetic resistance triggered our interest in the use of intercropping as a tool for the management of this disease. The effect of intercropping on chocolate spot severity was studied in field experiments performed in Egypt, the Palestinian Territories, Spain and Tunisia, in which a susceptible faba bean cultivar was grown as a monocrop or with two mixed species intercrops of either barley, oat, triticale, wheat, pea or common vetch, or with three mixed species intercrops of wheat and berseem clover. Chocolate spot was significantly reduced when faba bean was intercropped with cereals, but not when intercropped with legumes. Suppressive effects can be ascribed to a combination of host biomass reduction, altered microclimate and physical barriers to spore dispersal.

Nutrição e produtividade da cultura do milho em sistemas de culturas e fontes de adubação

A utilização de esterco animal na agricultura, aliada ao cultivo de plantas de cobertura, pode conferir sustentabilidade ao sistema agrícola. Com o objetivo de avaliar o efeito de dois sistemas de culturas e de três fontes de nutrientes, na cultura do milho, conduziu-se um experimento, em Latossolo Vermelho, no município de Marechal Cândido Rondon (PR). O delineamento experimental utilizado foi de blocos casualizados, com quatro repetições, e, os tratamentos, dispostos em esquema fatorial 2 x 3, compostos por dois sistemas de culturas (sucessão trigo/milho e consórcio aveia+ervilhaca+nabo/milho) e três fontes de nutrientes (mineral, orgânica e organomineral). Em junho de 2006, implantou-se a cultura do trigo e o consórcio de plantas de cobertura. Em outubro de 2006, semeou-se milho sob os dois sistemas. As adubações orgânica e organomineral consistiram na aplicação de dejetos de suínos, unicamente, e combinada com fertilizante mineral, respectivamente. O consórcio de aveia preta, ervilhaca peluda e nabo forrageiro mostrou-se capaz de fornecer a quantidade adequada de biomassa, concretizando sua viabilidade para produção de cobertura vegetal ao solo, durante o inverno. O cultivo de milho em sucessão ao trigo proporcionou a maior absorção de N e K e a maior produtividade. A adubação mineral proporcionou maior absorção de N e maior produtividade de milho, em comparação com as adubações orgânica e organomineral com dejetos de suínos.

Integrating a simple shading algorithm into CERES-wheat and CERES-maize with particular regard to a changing microclimate within a relay-intercropping system

Wheat/maize related multi-cropping systems are the dominant cropping systems in North China. To improve and adjust those systems, and to study competition effects within intercropping, extended field experiments are necessary. As field experiments are time consuming, laborious and expensive, a viable alternative is the use of crop growth models that can quantify the effects of management practices on crop growth and productivity. Field experiments showed that intercropped maize yielded as high as monocropped maize, and grain yield of intercropped wheat increased by up to 32%. Based on a process-oriented modeling approach, this study focuses on analyzing and modeling competitive relationships in a wheat/maize relay intercropping system with regard to yield, solar radiation and microclimate effects. A simple shading algorithm was applied and integrated into the CERES models, which are part of the DSSAT software shell vs. 4.5. The algorithm developed estimates the proportion of shading as affected by neighbouring plant height. The model was tested to investigate the applicability of this shading algorithm within the CERES models in the simulation of grain yield and dry matter yield of wheat and maize. Model error of grain and dry matter yield for both species was below 10%. There was a tendency for grain yield to be simulated adequately but for dry matter yield to be slightly underestimated. Increased top soil temperature in intercropped wheat increased the mineralization of nitrogen and improved N supply. The wheat/maize system was N efficient. Thus, N dynamics were taken into account for simulation as well as CO 2 dynamics based upon modified wind speed. Wheat border rows were exposed to a higher wind speed until mid-June and to reduced wind speed thereafter. As a result, solar radiation, soil temperature and wind speed differed between monocropping and intercropping and could provide a starting point for simulating intercropping. Microclimate effects are often small, subtle or non-existent, while spatial and climate variability and the heterogeneity of plant populations can be considerable. Quantifying microclimatic effects may prove difficult but should not be neglected when simulating intercropping systems.

Damage Degularity and Control Techniques of Eulecaium gigantean Around Tarim Basin in Xinjiang

Eulecaium gigantean (Shinji) has entered Xinjiang since the 1970s and mainly spread in the areas such as Haotan, Kashgar as well as Aksu. Eulecaium gigantean (Shinji) has one generation each year in Tarim Basin,two-year nymphae settle on the tree trunk to pass winter and start to absorb food from the trunk by pricking in the late March and the middle of April. Covering an area of 0.0666×104 hm2 in 1986 to that of 3.5747×104hm2 in 2010.The area inflicted by the insects has been on the rise dramatically, reaching 0.9300×104hm2 in 2004,declining in 2008, arriving at 60hm2 in 2010. Among the eleven types of trees investigated,P.bolleana,with 3.3% of plants indlicted, is listed as the least inflicted trees and the most seriously damaged is Robinia pseudoacacia, followed by red dates, white wax, almond, white elm,apricot, peach, Juglans regia L.peach, apple tree and P.bolleana.The investigation also shows that intercropping wheat and corn among apricot trees is helpful for its natural enemy,blastothrix sericea to parasite in Eulecaium gigantean. Both biopesticides and chemical pesticides are effective in preventing and controlling the damage caused by the insects with effect from 85 to 90% and from 73 to 87% respectively.

Environmental Resource Consumption in Wheat (Triticum aestivum) and Bean (Vicia faba) Intercropping: Comparison of Nutrient Uptake and Light Interception

Wheat (Triticum aestivum) and bean (Vicia faba L.) sole crops and their mixture in three planting pattern (M1: alternate-row intercrop, M2: within-row intercrop, M3: mixed intercrop) were used to investigate the amount of resource consumption in terms of PAR interception and nutrient uptake. The experiment was carried out as randomized complete block design with four replications. The results showed that intercropping systems had a significant effect on environmental resources consumption, where intercropping systems had more nutrient uptake and light interception compared to sole crops, suggesting the complementarity effect of intercropping components in resources consumption. The ability of wheat and bean was different in intercropping systems in absorbing nutrients because of their differences in root morphology and cation exchange capacity.

Responses of the parasitoids of Delia radicum (Diptera: Anthomyiidae) to the vegetational diversity of intercrops

Several natural enemies regulate populations of root maggots ( Delia spp.) (Diptera: Anthomyiidae) in canola ( Brassica napus L.) in western Canada, among them the rove beetles Aleochara bilineata Gyllenhal and Aleochara verna Say (Coleoptera: Staphylinidae) and the hymenopteran Trybliographa rapae Westwood (Hymenoptera: Figitidae). Intercrops of canola and wheat ( Triticum aestivum L.) can be part of an integrated pest management strategy to reduce damage by Delia spp. to canola. We investigated several intercropping regimes of canola and wheat to determine effects on parasitism of Delia radicum (L.) and activity densities of adult A. bilineata and A. verna. Studies were conducted over four site-years in central Alberta, Canada in 2005 and 2006. Mean parasitism rates of D. radicum puparia by A. bilineata ranged from 7.27% to 81.69%. Increasing proportions of wheat in intercrops significantly reduced parasitism by A. bilineata in one site-year. Parasitism of D. radicum by T. rapae was not affected by intercropping; mean parasitism rates were between 2.17% and 14.55%. In one site-year combined parasitism by all parasitoids significantly increased with increasing canola as a proportion of total crop plant populations. Pitfall trap collections of adult A. bilineata increased with increasing proportions of canola in some site-years. Collections of A. verna adults were low relative to A. bilineata and were largely unaffected by intercropping. Although canola–wheat intercrops do not appear to favour parasitism of D. radicum, reductions in canola root damage by Delia larvae in intercrops, reported previously, suggest that canola–wheat intercrops may nevertheless be favourable as a crop protection strategy.

The effect of various dynamics of N availability on winter pea–wheat intercrops: Crop growth, N partitioning and symbiotic N 2 fixation

Cereal–legume intercrops are a promising way to combine high productivity and several ecological benefits in temperate agro-ecosystems. However, the proportion of each species in the mixture at harvest is highly variable. The aim of this study was to test whether the timing of small application of N fertilizer is an effective way of influencing the dynamic interactions between species during crop growth and affecting the percentage of each species in the biomass of the mixture without greatly disturbing N 2 fixation. The influence of timing of nitrogen fertilization in pea–wheat intercrops was studied as regards (i) the dynamics of crop growth, (ii) nitrogen acquisition of each species, (iii) the inhibition and recovery of symbiotic N 2 fixation (SNF) after N application and (iv) final performance (yield, % of wheat, grain protein content). This was assessed in winter pea–wheat ( Pisum sativum L.– Triticum aestivum L.) intercrops in 2007 and 2008 at two locations in France. Whatever the stage of application, N fertilizer tended to increase wheat growth and to decrease pea growth. N fertilization (applied once at different dates from tillering to the end of stem elongation) delayed the decrease in the contribution of wheat to total biomass and maintained the competitive ability of wheat over pea for longer than in unfertilized intercrops. N acquisition dynamics and N sharing between the two species were modified by N fertilization and its timing. Crop conditions at the time of N application (growth and phenology of each species, and their proportions in the intercrop biomass) greatly influenced intercrop response to N fertilization. Partitioning between species of soil and fertilizer N was correlated with the proportion of wheat in the total intercrop biomass observed at the date of N application. Short-term inhibition of nitrates on SNF was shown during the few days after N application, whatever its date. SNF recovery after N applications was observed only until pea flowering, but was prematurely stopped by N fertilization after this stage. The effect of N fertilization on the amount of fixed N 2 at harvest was correlated with pea biomass. N fertilization affects N 2 fixation mainly by affecting crop growth rather than %Ndfa in pea–wheat intercrops. In conclusion, N fertilization could be used as a tool to enhance the contribution of wheat in the intercrop biomass but may reduce the amount of fixed N 2 in the intercrop by decreasing pea biomass.

Effect of N supply and wheat/faba bean intercropping on N uptake and accumulation of wheat

田间试验研究了小麦蚕豆间作及4种施氮水平(0、90 kg·hm^-2、180 kg·hm^-2和270 kg·hm^-2)对小麦植株体内氮含量、小麦地上部氮素累积及氮素养分吸收速率的影响。结果表明: 间作显著增加了小麦地上部植株的氮含量, 与单作相比, 分蘖期、拔节期、抽穗期和成熟期不同施氮处理间作小麦植株的氮含量平均比单作提高20.0%、21.9%、21.4%和17.1%; 抽穗期和成熟期间作小麦叶、茎和穗中的氮含量均高于单作; 间作显著提高了小麦植株的氮素累积量和氮素吸收速率, 与单作相比整个生育期间作小麦氮素累积量增幅为15.5%~30.4%。无论单作还是间作, 小麦植株氮含量和氮素累积量随氮肥用量的增加而增加, 施氮对单作小麦植株氮含量、氮素累积量和氮素吸收速率的影响大于间作, 随着氮肥用量的增加, 间作优势逐渐减弱; 单作小麦植株的氮素吸收速率随氮肥用量的增加而增加, 间作小麦植株的氮素吸收速率随氮肥用量的增加呈先增后降的趋势。本研究表明, 间作和施氮促进了小麦对氮素的吸收利用, 间作优势与施氮水平密切相关, 间作体系中氮素养分的合理投入是发挥间作优势的关键。

Suitability of legume cover crop-winter wheat intercrops on the semi-arid Canadian Prairies

Farmers on the Canadian prairies are interested in including legume cover crops in their cropping systems to reduce fertilizer inputs and improve farm sustainability. A field study was conducted to determine the merits of establishing alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.) or Austrian winter pea (Pisum sativum L.) cover crops in fall or in spring with winter wheat (Triticum aestivum L.). Spring-planted legumes emerged well within the winter wheat crop, but their growth was limited under these semi-arid conditions. Fall-planted red clover had low plant densities following winter in two of three experiments and fall-planted winter pea reduced winter wheat yield by 23 to 37% compared with the no cover crop control. In contrast, fall-planted alfalfa exhibited good winterhardiness, provided some weed suppression without reducing winter wheat yield, caused only a slight reduction in soil water content, and contributed an extra 18 to 20 kg ha-1 of available soil N at the time of seeding the following spring crop. Additionally, fall-planted alfalfa increased the yield of succeeding canola (Brassica napus L.) in unfertilized plots in two of three experiments. Further research is warranted to better understand the agronomic and economic benefits of alfalfa-winter wheat intercrops under a wider range of environmental conditions.Key words: Cover crops, intercropping, relay crops, soil nitrogen, soil conservation