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.     

Planting density and sowing proportions of maize–soybean intercrops affected competitive interactions and water-use efficiencies on the Loess Plateau,China

In field trials on the Loess Plateau, China, in 2012–13, maize (Zea mays L.) and soybean (Glycine max L.) were sole cropped and intercropped at three densities and with three sowing proportions. Maize was generally more growth efficient for biomass accumulation than soybean during the entire growth interval, as assessed using the relative efficiency index (REI_c). However, most of sowing proportion at each density displayed a trend of decreased growth with development. Throughout the growth period, the dry matter production and leaf area index (LAI) of maize increased as the plant density increased irrespective of whether it was grown as a sole crop or as an intercrop. However, the effect of increasing cropping density was less obvious for soybean. The LAI values of the sole crop treatment for both maize and soybean were greater than that of the intercropping system, indicating that the presence of maize and soybean together suppressed the respective growth of the two crops. At the final harvest, land equivalent ratios (LER) of 0.84–1.35 indicated resource complementarity in most of the studied intercrops. Complementarity was directly affected by changes in plant densities; the greatest LER were observed in 2 rows maize and 2 rows soybean intercrops at low density. The water equivalent ratio (WER), which characterized the efficiency of water resource use in intercropping, ranged from 0.84 to 1.68, indicating variability in the effect of intercropping on water-use efficiency (WUE).     

Effect of Drought Stress on Yield and Quality of Maize/Sunflower and Maize/Sorghum Intercrops for Biogas Production

Intercropping represents an alternative to maize (Zea mays L.) monoculture to provide substrate for agricultural biogas production. Maize was intercropped with either sunflower (Helianthus annuus L.) or forage sorghum [Sorghum bicolor (L.) Moench] to determine the effect of seasonal water supply on yield and quality of the above‐ground biomass as a fermentation substrate. The two intercrop partners were grown in alternating double rows at plant available soil water levels of 60–80 %, 40–50 % and 15–30 % under a foil tunnel during the years 2006 and 2007 at Braunschweig, Germany. Although the intercrop dry matter yields in each year increased with increasing soil moisture, the partner crops responded quite differently. While maize produced significantly greater biomass under high rather than low water supply in each year, forage sorghum exhibited a significant yield response only in 2006, and sunflower in none of the 2 years. Despite greatly different soil moisture contents, the contribution of sorghum to the intercrop dry matter yield was similar, averaging 43 % in 2006 and 40 % in 2007. Under conditions of moderate and no drought stress, sunflower had a dry matter yield proportion of roughly one‐third in both years. In the severe drought treatment, however, sunflower contributed 37 % in 2006 and 54 % in 2007 to the total intercrop dry matter yield. The comparatively good performance of sunflower under conditions of low water supply is attributable to a fast early growth, which allows this crop to exploit the residual winter soil moisture. While the calculated methane‐producing potential of the maize/sorghum intercrop was not affected by the level of water supply, the maize/sunflower intercrop in 2006 had a higher theoretically attainable specific methane yield under low and medium than under high water supply. Nevertheless, the effect of water regime on substrate composition within the intercrops was small in comparison with the large differences between the intercrops.     

Effects of Bean Population and Row Arrangement on the Productivity of Chilli/Dwarf Bean (Capsicum annuum/Phaseolus vulgaris L.) Intercropping in Sri Lanka

Intercropping of chilli ( Capsicum annuum ) and dwarf bean ( Phaseolus vulgaris ) is a recently adopted practice by farmers in Sri Lanka. As chilli fetches a higher market price, the bean population which could be incorporated into a 100% population of chilli has to be found. In the present experiment, effects of three bean populations (100, 75 and 50% of sole crop population 250 000 pl ha⁻¹) and four row arrangements (1:1, 1:2, 2:1 and 2:2) were tested at Kundasale, Sri Lanka. The land equivalent ratio (LER) of all intercrops were significantly greater than one, indicating a greater productivity per unit land area in intercropping than sole cropping. At 100% and 75% bean populations, LER and intercrop yields of bean were significantly greater than at 50%. Row arrangement did not have a significant effect on either LER or bean yield in intercrops. Intercrop bean yields were lower than sole bean yields indicating significant competition from chilli. Chilli yields were not affected by either bean population or row arrangement. Intercrop chilli yields were greater than the sole chilli yield indicating significant positive effects from bean. Greater radiation interception and lower weed growth and the absence of overlap between yield formation periods of the two component crops were probably responsible for the greater productivity (LER) of intercrops.     

Intercropping and Poultry Manure Effects on Yields of Corn, Watermelon and Soybean Grown in a Calcareous Soil in the Jordan Valley

This study was conducted at the University of Jordan Research Station in the central Jordan Valley during 1988 and 1989 summer growing seasons, to determine the potential and response of summer crops to intercropping system and to poultry manure addition. Corn, soybean and watermelon were grown as sole crops and as intercrops in three paired combinations (corn: watermelon, corn: soybean, watermelon: soybean) with three levels of poultry manure (0, 20, 40 t/ha). The crop yields and land equivalent ratios (LERs) were determined for all treatments. The highest yields for the two cropping systems were obtained in response to the highest poultry manure addition. Corn gave the highest yield when intercropped with soybean, where increases in yield of 45 % and 66 % were obtained over those of corn sole crop at the same level of poultry manure (40 t/ha), in 1988 and 1989 seasons, respectively. Soybean gave the highest yield when grown with corn leading to an increase of 35 % and 34 % over soybean sole crop grown at the same level of poultry manure (40 t/ha) in 1988 and 1989, respectively. Watermelon gave the highest yield when grown with soybean, giving an increase which ranged from 390 to 920 kg ha⁻¹ over the yield of sole cropping system under the same level of poultry manure (40 t/ha). The LER values for all intercrop treatments were greater than 1.0 which gave clearly an indication for the superiority of the intercropping over the sole cropping system especially when 40 t ha⁻¹ poultry manure was added.     

玉米–大豆带状套作行距配置对作物生物量、根系形态及产量的影响

空间配置是影响间作套种作物生长和产量构成的关键因素之一。本研究固定玉米–大豆套作带宽200 cm,玉米采用宽窄行种植,设置4个玉米窄行行距为20 cm(A1)、40 cm(A2)、60 cm(A3)和80 cm(A4)套作处理,2个玉米和大豆净作对照处理,研究行距配置对套作系统中玉米和大豆生物量、根系及产量的影响。结果表明,套作大豆冠层光合有效辐射和红光/远红光比值均低于净作,且随着玉米窄行的增加而降低。套作系统中大豆地上地下生物量、总根长、根表面积和根体积从第三节龄期(V3)到盛花期(R2)逐渐增加,但随着玉米窄行的增加而降低。套作玉米地上地下生物量从抽雄期到成熟期逐渐增加,根体积却逐渐降低,但这些参数随玉米窄行的变宽而增加。玉米和大豆在带状套作系统中产量均低于净作,且随玉米窄行的变宽,玉米产量逐渐增加,2012和2013两年最大值平均为6181 kg hm–2,而大豆产量逐渐降低,两年最大值平均为1434 kg hm–2,产量变化与有效株数和粒数变化密切相关。此外,玉米–大豆带状套作群体土地当量比(LER)大于1.3,最大值出现在A2处理,分别为1.59(2012年)和1.61(2013年),且最大经济收益也出现在A2处理(2年每公顷平均收益为1.93万元)。因此,合理的行距配置对玉米–大豆带状套作系统中作物的生长、产量构成和群体效益具有重要的作用。     

N and P Fertilizer Use in Soybean/Maize Mixture

Field experiments were conducted to investigate into the N and P fertilizer use in soybean/maize mixture during the wet seasons of 1985 and 1986 at Yandev Agricultural Experiment Station. Soybean/maize mixtures with 2/3 of the respective plant population of both crops in pure stands were raised at factorial combinations of four rates of N, 0, 40, 80, and 120 kg N/ha and four rates of P, 0, 13.2, 26.4 and 39.6 kg P/ha in a randomized complete block design with three replications.
The grain yield of maize cv. TZB (a pure line variety) in mixture and land equivalent ratio (LER) increased linearly up to 120 kg N/ha in 1985 as against significant increase in the grain yield of maize cv. 8322–3 (a hybrid variety) and LER up to 40 kg N/ha only in 1986 primarily due to greater fertilizer N recovery by the latter. Significant enhancement in LER was also recorded up to 26.4 kg P/ha in both years. The yield of soybean in mixture remained unaffected by N or P rates.
Total N uptake by shoots of soybean/maize mixture was significantly and linearly increased up to the application of 120 kg N/ha in 1985 as against significant increase in total N uptake by soybean/maize mixture only up to 40 kg N/ha in 1986 owing to the greater fertilizer N recovery by maize (69%) in the latter than the one (29.75—31.75%) in the former. Total N uptake by shoots of soybean/maize was also increased significantly due to the application of 26.4 kg P/ha.
Application of N and P also significantly enhanced P uptake by shoots of soybean/maize mixture and fertilizer P recovered by mixture was less (3.99—12.95%) in 1985 than the one (19.95—32.12%) in 1986.     

Cassava and Maize Intercropping Systems — The Effects of Varieties and Plant Populations

Maize dominated cassava irrespective of cassava or maize growth habit and the optimum maize population giving the highest production based on relative yield total or land equivalent ratio varied with maize variety in a tropical Alfisol at Ibadan, transition humid/subhumid zone in West Africa. The sparsely vegetative, early maize supported higher intercrop maize population (up to 80,000 ha⁻¹) than the late maturing, highly vegetative TZSRW. Because there is a compensatory relationship in the yields of the two crop components, the choice of an appropriate crop type and maize population in cassava + maize intercrop system will depend on the relative economic importance of each crop component.     

Yield and Yield Components from Intercropping Improved Bush Bean Cultivars with Maize

Bush bean ( Phaseolus vulgaris L.) is widely intercropped with maize ( Zea mays L.) in North-west Spain. Little information is available on the relative performance of elite bush bean cultivars when intercropped or on the effect of bush bean on performance of the maize crop. This two-environment study presents the interactions between improved bush bean cultivars and maize on yield and yield components. Eight treatments (four bean/maize intercrops and four sole crops, two of bean and two of maize) were tested using a randomized complete block design with four replications in two environments. Bean and maize were planted simultaneously in alternate rows when intercropped. Significant treatment differences were observed for bean and maize moisture, pod and cob percentage, bean and maize yield, ears per plant and ear length. Location effects were significant for bean and maize moisture and pod percentage. Significant treatment by location interactions occurred for pod percentage and ear length. Intercropping reduced yield by between 40 and 60 % for bush bean cultivars, and by 45 % for both maize cultivars. Mean yields were used to calculate the land equivalent ratio (LER), which averaged 1.01 in Pontevedra but 0.93 in La Coruña. Intercropping of bush bean with maize did not make better use of land than conventional sole cropping under these environmental conditions. It is suggested that this was probably due to the amount and distribution of rain in relation to crop growth. Approaches that might be expected to result in improved land usage are presented.     

Yield and yield components of wheat and maize in wheat–maize intercropping in the Netherlands

Intercropping is widely used by smallholder farmers in developing countries, and attracting attention in the context of ecological intensification of agriculture in developed countries. There is little experience with intercropping of food crops in Western Europe. Yields in intercrops depend on planting patterns of the mixed species in interaction with local growing conditions. Here we present data of two years field experimentation on yield and yield components of a wheat–maize intercrop system in different planting configurations in the Netherlands. Treatments included sole crops of wheat (SW) and maize (SM), a replacement intercrop consisting of strips of six wheat rows alternating with two maize rows (6:2WM), as well as subtractive or additive designs, based on skip-row (6:0WM, 0:2WM) and add-row (8:2WM, 6:3WM) configurations. The land equivalent ratio (LER) of intercrops varied from 1.18 to 1.30 in 2013 and from 0.97 to 1.08 in 2014. Wheat grown in the border rows of wheat strips had higher ear number per meter row, greater kernel number per ear, and greater yield per meter row than wheat in inner rows and sole wheat, indicating reduced competition. Wheat in the border rows in the intercrops had, however, reduced thousand kernel weight and harvest index, indicating that competition in border rows intensified over time. Intercropping negatively affected maize biomass and thousand kernel weight, especially in add-row treatments. This study indicates that there is a potential yield benefit for the wheat–maize intercropping system under Western European growing conditions. However, the LER was affected by yearly variation in weather conditions and significantly greater than one in only one of the two years of the study.     

Effect of Population Levels of Soybean on Physiological Growth Parameters of Sorghum CO 24 in Sole and Intercropped Stand

A field experiment was conducted during kharif, 1985 and summer, 1986 in sandy clay loam soil under irrigated condition at Tamil Nadu Agricultural University, Coimbature, with a view (i) to assess the suitable method of planting of sorghum CO 24 when intercropped with soybean, (ii) to evaluate the suitable planting ratio of sorghum - soybean intercropping system, (iii) to find out the compatible population level of soybean when intercropped with sorghum CO 24.
Direct sown sorghum at 4: 2 and 2: 2 recorded grater leaf area (LA) compared to transplanted sorghum in both kharif and summer. Sorghum transplanted with 14 days old seedlings recorded higher Crop Growth Rate (CGR) compared to 21 days old seedlings. Increased Net Assimilation Rate (NAR) were recorded in sorghum transplanted with 14 days old seedlings as compared to direct sown and 21 days old transplanted crop. Transplanted sorghum recorded higher Relative Growth Rate (RGR) as compared to direct sown sorghum. Summer sorghum recorded higher Relative Growth Rate (RGR) as compared to kharif season.     

Direct and Residual Contributions of Symbiotic Nitrogen Fixation by Legumes to the Yield and Nitrogen Uptake of Maize (Zea mays L.) in the Nigerian Savannah

Field experiments were conducted to determine the direct and residual contributions of legumes to the yield and nitrogen (N) uptake of maize during the wet seasons of 1994 and 1995 at the University Farm, Abubakar Tafawa Balewa University, Bauchi, Nigeria, located in the Northern Guinea savannah of Nigeria. Nodulating soybean, lablab, green gram and black gram contributed to the yield and N uptake of maize either intercropped with the legumes or grown after legumes as a sole crop. Direct transfer of N from the nodulating soybean, lablab, green gram and black gram to the intercropped maize was 24.9–28.1, 23.8–29.2, 19.7–22.1 and 18.4–18.6 kg N ha^–1, respectively. However, the transfer of residual N from these legumes to the succeeding maize crop was 18.4–20.0, 19.5–29.9, 12.0–13.7 and 9.3–10.3 kg N ha^–1, respectively. Four years of continuous lablab cropping resulted in yields and N uptake of the succeeding maize crop grown without fertilizer N that were comparable to the yields and N uptake of the succeeding maize crop supplied with 40–45 kg N ha^–1 and grown after 4 years of continuous sorghum cropping. It may therefore be concluded that nodulating soybean, lablab, green gram and black gram may be either intercropped or grown in rotation with cereals in order to economize the use of fertilizer N for maize production in the Nigerian savannah.     

施磷对不同间作体系间作优势与磷肥利用的影响

为了探明施磷水平对不同间作体系产量间作优势和磷肥利用的影响,在河北曲周主要研究了施磷对玉米‖蚕豆、玉米‖大豆和玉米‖油菜3种间作体系土地当量比(LER)、磷吸收量、磷肥吸收效率和磷间作优势的影响。结果表明：玉米‖蚕豆的LER是1.24~1.31,玉米‖油菜的LER是1.20~1.24,玉米‖大豆的LER是1.11~1.15,均大于1,具有明显的间作优势;3个磷水平下,吸磷量表现为玉米‖大豆>玉米‖蚕豆>玉米‖油菜,除玉米‖油菜间作体系外,比单作玉米分别高21.5%%~40.2%和13.3%~22.9%,且均随着施磷量的增加而增加,但增加幅度降低;3种间作体系均具有明显的磷间作优势,除玉米‖大豆间作体系外,施磷后均降低;磷肥吸收效率除玉米‖蚕豆在施磷90 kg/hm²外均低于单作玉米,并且随着施磷量的增加而降低。这表明,通过活化磷能力强的作物与玉米间作可以提高土壤难溶性磷的利用,玉米‖大豆和玉米‖蚕豆比玉米‖油菜效果好,适宜的施磷量为90 kg/hm²。     

Effect of Okra Planting Density and Spatial Arrangement in Intercrop with Maize on the Growth and Yield of the Component Species

The effects of three okra planting densities (28 000; 56 000 and 111 000 plants ha¹) intercropped within or between maize rows were investigated in two field trials during the 1990 and 1991 wet seasons at Nsukka. The plant height and the leaf area index (LAI) increased as the planting density increased in sole or intercropped okra while the number of branches per plant decreased with increasing okra planting density. The height of maize plants also increased as okra planting density increased but the LAI decreased. Intercropping reduced the yield and yield components (number and weight of pods per plant) of okra and maize (number of cobs, cob length and 100-grain weight). Increasing okra planting density reduced the sole and the intercropped okra and also the maize intercrop yield by reducing the number of pods and grains as well as the pod and grain size, respectively. Assessment of the productivity ofthe mixtures showed that the highest yield advantage (35%) of growing okra and maize together was obtained at 28000 okra plants ha¹ while the highest monetary return was realized at the highest okra planting density of 111000 plants ha¹ intercropped between maize rows. The patterns of row arrangement did not have effect on the growth, yield and yield components of the mixtures.     

西南地区不同套种模式对土壤肥力及经济效益的影响

为探讨不同作物组合的种植模式对土壤肥力及经济效益的影响,寻找作物搭配合理、低投入高产出的套作模式。采用单因素随机区组试验,研究比较了4种套作模式(小麦/玉米/大豆、小麦/玉米/甘薯、小麦/高粱/大豆、马铃薯/玉米/大豆)的土壤肥力、产量及经济效益的差异。连续种植3年后,各种植模式的土壤养分含量基本维持或得到提升(速效钾除外)。甘薯茬口对全钾、速效钾消耗均较大,需适当提高钾肥用量。小麦/玉米/甘薯的总产量最高,小麦/玉米/大豆模式的大豆单产量最高,小麦的单产各模式无显著差异。不同模式收益表现为,小麦/玉米/大豆马铃薯/玉米/大豆小麦/玉米/甘薯小麦/高粱/大豆;产投比表现为,小麦/玉米/大豆马铃薯/玉米/大豆小麦/玉米/甘薯小麦/高粱/大豆。小麦/玉米/大豆收益为14196.41元/hm~2,产投比为3.69:1,均为所有模式中最高,加之大豆茬口可以活化土壤养分,是相对理想的套作模式。     

Agronomic Performance of Sorghum and Groundnut Cultivars in Sole and Intercrop Cultivation under Semiarid Conditions

The performance of sorghum and groundnut cultivars was studied in sole cropping and intercropping systems at Babile in the semiarid area of eastern Ethiopia in 1996, 1997 and 1999. On average, late-maturing cultivars of groundnut and sorghum gave higher dry pod yield and grain yield, respectively, when intercropped with early-maturing cultivars of the associated crops. The significant variation among groundnut cultivars in yield and yield components under intercropping with sorghum cultivars revealed that sole cropping may not provide the appropriate environment for selecting varieties intended for use in intercropping. The productivity of intercropped groundnut and sorghum cultivars, as determined by total land equivalent ratios (LER), was higher than sole cropping, indicating the presence of temporal complementarity in the use of growth resources. A mean yield advantage of 32 % was obtained under intercropping.     

根间作用与密度协同作用对小麦间作玉米产量及产量构成的影响

密植是间作模式下重要的增产增效技术措施,本研究旨在探讨间作适应密植的产量构成响应机制。2014—2015年连续两年在河西绿洲灌区进行田间试验,设计不隔根、尼龙网隔根(阻断根系交叉,仅有水分养分的交流)和塑料布隔根(完全阻断)3种根间作用方式,及2个玉米种植密度(9.0万株hm~(-2)和10.5万株hm~(-2)),测定地上、地下部互作对小麦间作玉米产量及产量构成因素的影响。与单作相比,地上、地下部完全作用时间作优势提高48.3%,密度增加使其间作优势增加9.7%,地下部互作对间作优势的贡献率为21.0%,增加密度使其贡献率提高5.0%,根系交叉叠加对间作优势产生的补偿效应为9.0%,地下部水养分交流互补效应为11.1%。地上、地下部完全互作下混合籽粒产量相对于单作增幅最大,高、低密度下增幅分别达58.8%~62.2%和36.1%~36.8%;间作中地下部分对小麦组分籽粒产量的贡献率为26.5%~31.5%,其中根系穿叉产生的补偿效应为12.9%~13.2%,地下部水分养分交流互补效应为12.2%~16.0%;地下互作对玉米组分籽粒产量的贡献率为9.7%~22.6%,增加密度使地下互作贡献率提高7.0%~11.0%;密度提高对不隔根和尼龙网隔根产量的贡献率分别18.1%~23.3%和12.5%~21.5%,说明根间完全作用有利于密度正效应的发挥。地下互作对小麦穗数贡献率为5.5%~11.4%,密度对小麦地下部贡献率影响差异不显著,地下互作对玉米穗数的贡献率为12.5%~16.3%,增加密度使地下互作贡献率增加3.6%~14.1%。通径分析进一步表明,不同根间作用及密植效应下间作小麦、玉米主要通过提高单位面积穗数来提高籽粒产量。本研究表明,增加密度可显著增加间作优势和地下部贡献率,地上地下完全互作有利于密植效应充分发挥,可为进一步发掘密植条件下的间作优势机理提供理论依据。     

Annual Medicago as a Smother Crop in Soybean

Use of conservation tillage and narrow row spacing in soybean [Glycine max (L.) Merr.] production has led to increased use of herbicides for weed control. Some producers are seeking alternative weed control methods, such as smother crops, that would reduce dependence on chemical weed control. A successful smother crop must compete strongly with weeds but minimally with the crop. In four environments, we intercropped three annual Medicago spp. (medics) with soybean to test their utility as a smother crop for weed control. Annual medics were intercropped with soybean at rates of 0, 85, 258, or 775 seeds m^?2, and the intercrops were grown with and without weed control. Increasing medic seeding rate decreased weed yields but also reduced soybean herbage and grain yields. For the weed‐controlled treatment, average soybean grain yields declined 7 kg ha^?1 for every 10 seeds m^?2 increase in medic seeding rate. Soybean grain yield was lower when grown with Medicago scutellata L. cv. Sava than when grown with Medicago polymorpha L. cv. Santiago or Medicago lupilina L. cv. George. Soybean grain yield was negatively related (r=?81) to medic herbage production. In the autumn following soybean harvest, medic residue ranged from 200 to 3700 kg ha^?1 depending on the location and seeding rate. Medics provided residue for soil protection, suppressed weeds, but also reduced soybean yields.     

A Multivariate Analysis of Soybean Genotypes Grown Under Different Cropping Systems

Nature and magnitude of genetic diversity was assessed using Mahalanobis's D² statistics and canonical analysis in 50 genotypes of soybean grown in monoculture and in association with maize. All the genotypes were grouped in 10 clusters in case of monoculture, while 8 clusters were formed for intercropping. Monoculture was more suitable environment for expressing the genetic diversity than intercrop. Some genotypes had consistently the similar clustering pattern in both the cropping systems, while others were affected by the cropping system in expressing the genetic diversity. This was confirmed by the canonical analysis. Days to flowering and maturity, seed yield/plant, plant height and 100-seed weight were mainly responsible for genetic diversity in monoculture. Besides phenological traits, pod length and width, and seed yield/plant exerted marked influence on the genetic diversity of soybean genotypes grown in association with maize. Geographical distribution was not necessarily reflected by the genetic divergence, though some degree of relationship between geographic diversity and genetic diversity was evident under both the cropping systems. The performance of some genotypes varied from cropping system to another, while that of others remained unaffected. Breeding programmes to develop varieties suitable for sole crop, intercrop and both the cropping systems have been suggested.     

Effect of density,cultivar and irrigation on spring sown monocrops and intercrops of wheat (Triticum aestivum L.) and faba beans (Vicia faba L.)

Spring-sown intercrops of wheat (Triticum aestivum L.) and faba beans (Vicia faba L.) were grown in three experiments at the University of Reading, UK. One wheat cultivar, Axona, and one (experiment 1) or two bean cultivars (experiments 2 and 3) Scirocco and Maris Bead, were grown as sole crops and intercrops at 50%, 75% and 100% recommended density. Experiments were rainfed but irrigation was an additional treatment in experiment 3. Biomass and seed yields of both wheat and faba beans were greater when monocropped than when intercropped. There was no evidence that radiation use efficiency (RUE) of intercrops was significantly different from sole crops. In all intercrops there was no significant effect of density on biomass, RUE or seed yield, though there were compensating changes in yield components. Seed yields of Maris Bead were significantly greater than Scirocco in experiment 3 but not experiment 2. There was no significant effect of irrigation on RUE or on wheat biomass and seed yield, but there was a trend for irrigation to increase faba bean biomass (P = 0.07) and seed yield (P = 0.06). With later sowing in experiments 2 and 3, time to harvest was shorter and wheat and bean biomass, seed yield and RUE were reduced. All land equivalent ratio (LER) values for both biomass (maximum 1.23) and seed yield (maximum 1.44) were greater than 1, with one exception in experiment 3, indicating that intercrops of wheat and faba beans make more effective use of land than equivalent sole crops. Partial LERs for faba beans were always lower than those of wheat. The tendency was for highest LERs to occur at 75% recommended density.