Maize-bean Intercropping Research Articles

Land use practices and their implications on soil macro-fauna in Maasai Mara ecosystem

The composition, abundance, diversity and species richness of soil macro-fauna communities were assessed in four major land use types present within protected and agricultural landscapes in Maasai Mara savannah ecosystem (MME), Kenya. The four land uses were: natural grassland; woodland, inside and outside protected area; maize mono-cropping and maize-bean intercropping systems in adjacent agricultural farms. Sampling of soil macro-fauna was carried out in November, 2009 (short rain), April 2010 (wet rainy season) and September 2010 (dry season). Hand sorting of soil taken from 25 × 25 × 30 cm monoliths was used to extract all soil macro fauna greater than 2 mm body length. A total of 3,658 individuals comprising of 128 species mainly belonging to Phylum Arthropoda distributed across 3 classes and 13 orders, and Phylum Annelida with one order were collected across the four different land use systems. Termites and ants, and to a lesser extent coleopteran and earthworms were the most abundant groups. Significant effects of land use on macro-fauna abundance and species richness in all cases (p 50% and eliminating some Orders/Species. Human related disturbances outside protected area network declined macro-fauna density in grassland and woodland in dry region (65.07 vs. 39.74%) but increased the density by 107 vs. 340% in wet region. The study highlights the important effect of agriculture on macro-fauna communities and the need for conservation alternatives in unprotected areas. This study supports conservation of biodiversity beyond protected area network. Key words: Macro-fauna, grassland, woodland, agriculture, Maasai Mara, land use.

Maize–Bean Intercrop Weed Suppression and Profitability in Southern Ethiopia

Cereal–legume intercropping often results in increased productivity, weed suppression, and N supply. The agronomic and economic benefits of maize–bean (Zea mays L. –Phaseolus vulgaris L.) intercropping were studied for 5 yr in a complete factorial with: 0, 1, and 2 weedings (W0, W1, W2); and single (MB) and double (MBB) rows of bean alternated with one row of maize. Sole crop maize and bean were included. Weed infestation in intercrop was 30% less compared with sole crop bean but with inconsistent differences across years. Weed biomass was 13% less with MBB compared with sole‐cropped maize. Ears m−2 were 55% more in seasons with better rainfall compared with 1999 and 16% more with W1 or W2 compared W0. Mean maize grain yield was 3.74 Mg ha−1. Weeding frequency (WF) effect on maize grain yield was inconsistent across years but yield was 75% more with W2 compared with W0. Overall, maize grain yield was 19% more with MB compared with MBB but the effect was significant in 1997 only. Mean bean yield was 1.07 Mg ha−1 and was inconsistently affected by treatments across years. Bean yield was on average 52 and 67% more with W1 and W2, respectively, compared with W0, and 35% more with MB compared with MBB. Intercropping resulted in land equivalent ratios (LER) of 1.0 to 2.4 with a WF effect. Mean net income (NI) was greatest with MB and W1. Overall, intercropping suppressed weeds and was more productive and economical than sole crop production.

Integration of edible beans ( Phaseolus vulgaris L.) into the push–pull technology developed for stemborer and Striga control in maize-based cropping systems

Smallholder farming systems in eastern Africa are characterized by cereal/edible legume intercrops in fields severely constrained by parasitic weed, Striga hermonthica, cereal stemborers and declining soil fertility. The push–pull technology concurrently addresses these constraints. It involves intercropping maize with stemborer repellent fodder legume, Desmodium spp. (push), with an attractant crop, Napier grass, Pennisetum purpureum (pull), planted around this intercrop, thus making it difficult to interplant edible legumes. We assessed farmers' practice and perceptions on intercropping and willingness to integrate beans in their push–pull plots from a sample of 300 farmers in six districts in western Kenya. All the respondents traditionally intercropped maize with beans, planted either between the rows of maize, in the same holes with maize or in between maize plants within a row. The majority (92%) were willing to integrate beans in their push–pull plots. We, therefore, evaluated effects of integrating beans in the maize–desmodium intercrops. Treatments comprised a maize monocrop, maize–bean intercrop and three maize–desmodium intercrops, two of which were integrated with beans, either in the same holes with maize or in between maize plants in a row (bean integration plots). On-farm trials were similarly established among 56 farmers in four districts in western Kenya to assess the two integration methods. S. hermonthica counts and stemborer damage to maize were significantly lower and maize yields significantly higher in the maize–desmodium and bean integration plots than in the other systems. Overall, integration of beans in the maize–desmodium intercrops and the planting arrangement did not compromise the S. hermonthica and stemborer control efficacy of desmodium. Integration of beans significantly increased labour and total variable costs, with these being significantly higher in plots with both crops in different holes than in the same hole. Total revenue, gross benefits and benefit cost ratios did not significantly differ between the bean integration and maize–desmodium intercrops. Furthermore, these parameters were for most part not affected by the planting arrangements, both on-station and on-farm. These results show that integration of beans in the maize–desmodium and indeed push–pull technology while guaranteeing an additional crop, a protein source, to the farmers does not compromise the observed benefits of the technology but yields same economic benefits. Where labour is easily available, farmers are, however, advised to plant maize and beans in separate holes to avoid the risk of competition for moisture and nutrients where these might be limiting.

Economic performance of the ‘push–pull’ technology for stemborer and Striga control in smallholder farming systems in western Kenya

The ‘push–pull’ technology (PPT), developed in Africa, offers effective control of cereal stemborers and Striga weed in maize-based cropping systems. It involves intercropping maize with desmodium, Desmodium uncinatum, with Napier grass, Pennisetum purpureum, planted as border around this intercrop. Desmodium repels the stemborer moths (push) that are subsequently attracted to the Napier grass (pull). Desmodium also suppresses and eliminates Striga. We assessed economic performance of this technology compared to the conventional maize mono- and maize–bean intercropping systems in six districts in western Kenya over 4–7 years. Ten farmers were randomly recruited in each district and each planted three plots representing the three cropping systems. The cost–benefit analyses were carried out, together with the systems’ net returns to land and labour and their discounted net present values (NPV). Maize grain yields and associated gross margins from the PPT system were significantly higher than those in the other two systems. Although the production costs were significantly higher in the PPT than in the two cropping systems in the first cropping year, these reduced to either the same level or significantly lower than in the maize–bean intercrop from the second year onwards in most of the districts. Similarly, the net returns to land and labour with the PPT were significantly higher than with the other two systems. The PPT consistently produced positive NPV when the incremental flows of its benefits compared to those of the two conventional systems were discounted at 10–30%, indicating that PPT is more profitable than the other two systems under realistic production assumptions. PPT is thus a viable option for enhancing productivity and diversification for smallholder farmers who largely depend on limited land resource. Hence, enhancing farmers’ access to less costly planting materials and promoting quality education and training in the use of this knowledge-intensive technology could stimulate its successful adoption.

Integrated management of Striga hermonthica, stemborers, and declining soil fertility in western Kenya

Striga hermonthica (Delile) Benth., stemborers, and declining soil fertility are serious threats to sustainable food production in the Lake Victoria zone of Kenya. To address these constraints, promising integrated crop management technologies were evaluated, using a multi-locational design in four sub-locations in Siaya and Vihiga district (western Kenya) for six cropping seasons. Technologies evaluated consisted of the traditional maize ( Zea mays L.) – bean ( Phaseolus vulgaris L.) intercrop, maize – Desmodium (Desmodium uncinatum (Jacq.) DC.) push–pull intercrop, Crotalaria ( Crotalaria ochroleuca G. Don) – maize rotation, and soybean ( Glycine max (L.) Merr) – maize rotation. Within each of these systems, imazapyr-coated herbicide-resistant maize (IR-maize) and fertilizer were super-imposed as sub-plot factors. The push–pull system was observed to significantly reduce Striga emergence and stemborer damage from the second season onwards. IR-maize reduced and delayed Striga emergence from the first cropping season. Differences in Striga emergence and stemborer damage between the other systems were not significantly different. After five cropping seasons, the Striga seedbank was significantly higher in the maize-bean intercrop system than in the push–pull system under both maize varieties while the rotational systems had intermediate values not different from the day zero values. Under IR-maize, the Striga seedbank was significantly lower than under local maize for all cropping systems. Maize yields varied between seasons, districts, and cropping systems. Yields in the push–pull system were higher than in the maize-bean intercrop after two seasons and in the absence of mid-season drought stress. Both maize and soybean responded significantly to fertilizer application for both districts and for most seasons. The various interventions did not substantially affect various soil fertility-related parameters after five seasons. In the short term, IR-maize integrated in a push–pull system is the most promising option to reduce Striga while the rotational systems may need a longer timeframe to reduce the Striga seedbank. Finally, farmer-led evaluation of the various technologies will determine which of those is really most acceptable under the prevailing farming conditions.

Optimum plant population for maize-bean intercropping system in the Brazilian semi-arid region

Establishment of the ideal number of plant is a crucial point for obtaining maximum profits while cropping different species together. The main objective of the study was to investigate the effect of different plant populations of maize and beans, at two nitrogen levels, on the performance of the component crops. Two maize (20,000 and 40,000 plants ha¹) and three bean (30,000; 60,000 and 90,000 plants ha¹) populations were tested in a randomized complete block design with tree replicates. Grain yields of maize and beans were affected by intercropping and the effect was more detrimental to the legume mainly at the highest maize plant population. The application of nitrogen fertilizer to maize rows mitigated intercropping effect on maize at higher population (40,000 plants ha¹) and, at lower maize plant population (20,000 plants ha¹), benefited the associated beans by increasing grain yields. Land Equivalent Ratio values for grain yields of maize and beans showed that intercropping compared to sole cropping is advantageous and best indices were obtained at a bean plant population of 60,000 plants ha¹.

Profitability of agro-forestry based soil fertility management technologies: the case of small holder food production in Western Kenya

Persistent food insecurity accompanied by low and declining farm household incomes are a common feature of many small holder maize and bean producers in western Kenya. This has been largely attributed to soil nutrient depletion, among other factors. One way of addressing soil fertility problems in many maize-based cropping systems is the use of agro-forestry based technologies. We carried out a survey in western Kenya (Vihiga and Siaya districts) aimed at analyzing the financial and social profitability of use of agroforestry based (improved tree fallows) and other soil fertility management technologies among smallholder farmers. The Policy Analysis Matrix (PAM) was used to determine the financial and social profitability of different production systems, which were categorized on the basis of the technology used to address soil fertility. Farm budgets were first prepared and in turn used to construct the PAMs for six production systems namely: maize–bean intercrop without any soil fertility management inputs; maize–bean intercrop with chemical fertilizers only; maize–bean intercrop with a combination of chemical fertilizers and improved fallows; maize–bean intercrop with improved fallows only; maize–bean intercrop with a combination of improved fallows and rock phosphate; and maize–bean intercrop with Farm Yard Manure (FYM) only. Results revealed that use of chemical fertilizers with improved fallows was the most profitable technology and thus the study recommended that farmers be encouraged to intensify the use of chemical fertilizers. To make chemical fertilizers more accessible to farmers, the study also recommended that good linkages be made between farmers and micro credit institutions so that small scale farmers are not actually biased against due to lack of collateral when credit is being advanced to clients.

Yield evaluation of maize-bean intercropping in a semi-arid region of South Africa

Information on the effect of row orientation on land productivity of intercropping systems, especially in a semi-arid environment is limited. Field trials were, therefore, carried out under full irrigation and rainfed conditions in a semi-arid region of South Africa (Bloemfontein, Free State) during 1998-2002. The trials evaluated the intercrop yield advantage in terms of land equivalent ratio (LER), energy value (EV) and monetary value (MV). Treatments included three cropping systems (sole maize, sole bean, and the intercrop) and two cultural practices, namely, row orientation (north-south row vs east-west row) and sowing date (November/December and January). Intercropping showed a higher yield advantage in terms of LER and EV compared to sole cropping. Therefore, intercropping has potential for increasing yields in the semi-arid regions of South Africa. Monetary value is influenced by fluctuations of the price ratio of crops, so it is not always a useful factor for evaluating the yield advantage. Key words : Land equivalent ratio, Phaseolus vulgaris, row orientation, Zea mays RESUME L\'information sur l\'effet de l\'orientation en range sur la productive des terres des systemes d\'intercultures, specialement dams un environnement semi-aride est limite. Les essais sur le terrain etaient par consequent menes sous une irrigation complete et conditions de pluie dans une region semi-aride de l\'Afrique du sud [Bloemfontein, /etat libre] on cours de 1998-2002. Les essais evaluaient l\'avantage de la production d\'interculture en termes de proportion equivalente de terre [LER], la valeur d\'energie [EV] et la valeur monetaire [VM]. Les traitements avaient inclus trois systemes de cultures [mais seul, haricot seul et une combinaison mais-haricot] et deux pratiques culturales, a savoir, l\'orientation en range nord-sud contre range Est-ouest] et la date des semailles [Novembre/Decembre et Janvier]. L\'inter-culture a monte un avantage superieur en terme de LER et EV, comparer aux cultures seules. Par consequent, les cultures en combinaison ont une potentialite d'augmenter les rendements en region semi-aride de L\'Afrique du sud. La valeur monetaire est influencee par les fluctuations de la proportion des prix de recoltes, donc n\'est pas toujours un facteur utile pour l\'evaluation de l\'avantage du rendement. Mots cles : Proportion equivalente de terre, Phaseolus vulgaris, orientation en range, Zea mays African Crop Science Journal Vol.12(4) 2004: 351-358

Comparison of measured changes in seasonal soil water content by rainfed maize-bean intercrop and component cropping systems in a semi-arid region of southern Africa

Seasonal water content fluctuation within the effective root zone was monitored during the growing season for a maize-bean intercrop (IMB), sole maize (SM) and sole bean (SB) in Free State Province, Republic of South Africa. Comparisons were undertaken for progressive depths of extraction 0–300 mm; 300–600 mm and 600–900 mm respectively. These enabled the understanding of water extraction behavior of the cropping systems within the different soil layers including the topsoil surface normally influenced by soil surface evaporation. Additive intercrops have been known to conserve water, largely due to the early high leaf area index and the higher total leaf area. In this study, the combined effect of the intercrop components seemed to lower the total water demand by the intercrop compared to the sole crops. During the two seasons (2000/2001 and 2001/2002) the drained upper limit (DUL) and crop lower limits (CLL) were determined. The maize-bean intercrop, sole maize and sole bean had CLL of 141 mm/m, 149 mm/m and 159 mm/m respectively. The DUL was 262 mm/m for the site and therefore the potential plant extractable soil water for the cropping systems were: 121 mm/m (IMB); 114 mm/m (SM) and 103 mm/m (SB). Overall, the intercrop did not have significantly different total soil water extraction during both seasons, although it was additive, showing that it had higher water to biomass conversion.

A simulation model of cereal–legume intercropping systems for semi-arid regions: II. Model application

Smallholder farmers in Africa practice traditional cropping techniques such as intercropping. Intercropping is thought to offer higher productivity and resource utilisation than sole cropping. In this study, risk associated with maize–bean intercropping was evaluated by quantifying long-term yield in both intercropping and sole cropping in a semi-arid region of South Africa (Bloemfontein, Free State) with reference to rainfall variability. The crop simulation model was run with different cultural practices (planting date and plant density) for 52 summer crop growing seasons (1950/1951–2001/2002). Eighty-one scenarios, consisted of three levels of initial soil water, planting date, maize population, and bean population, were simulated. From the simulation outputs, the total land equivalent ratio (LER) was greater than one. The intercrop (equivalent to sole maize) had greater energy value (EV) than sole beans, and the intercrop (equivalent to sole beans) had greater monetary value (MV) than sole maize. From these results, it can be concluded that maize–bean intercropping is advantageous for this semi-arid region. Soil water at planting was the most important factor of all scenario factors, followed by planting date. Irrigation application at planting, November/December planting and high plant density of maize for EV and beans for MV can be one of the most effective cultural practices in the study region. With regard to rainfall variability, seasonal (October–April) rainfall positively affected EV and MV, but not LER. There was more intercrop production in La Niña years than in El Niño years. Thus, better cultural practices may be selected to maximize maize–bean intercrop yields for specific seasons in the semi-arid region based on the global seasonal outlook.

A simulation model of cereal–legume intercropping systems for semi-arid regions: I. Model development

Cereal–legume intercropping plays an important role in subsistence food production in developing countries, especially in situations of limited water resources. Crop simulation can be used to assess risk for intercrop productivity over time and space. In this study, a simple model for intercropping was developed for cereal and legume growth and yield, under semi-arid conditions. The model is based on radiation interception and use, and incorporates a water stress factor. Total dry matter and yield are functions of photosynthetically active radiation (PAR), the fraction of radiation intercepted and radiation use efficiency (RUE). One of two PAR sub-models was used to estimate PAR from solar radiation; either PAR is 50% of solar radiation or the ratio of PAR to solar radiation (PAR/SR) is a function of the clearness index ( K T). The fraction of radiation intercepted was calculated either based on Beer's Law with crop extinction coefficients ( K) from field experiments or from previous reports. RUE was calculated as a function of available soil water to a depth of 900 mm (ASW). Either the soil water balance method or the decay curve approach was used to determine ASW. Thus, two alternatives for each of three factors, i.e., PAR/SR, K and ASW, were considered, giving eight possible models (2 methods × 3 factors). The model calibration and validation were carried out with maize–bean intercropping systems using data collected in a semi-arid region (Bloemfontein, Free State, South Africa) during seven growing seasons (1996/1997–2002/2003). The combination of PAR estimated from the clearness index, a crop extinction coefficient from the field experiment and the decay curve model gave the most reasonable and acceptable result. The intercrop model developed in this study is simple, so this modelling approach can be employed to develop other cereal–legume intercrop models for semi-arid regions.

Productivity of maize-bean intercropping in a semi-arid region of South Africa

Food shortage is known to have been caused by overpopulation, natural disasters and poor food distribution. In areas facing food insecurity, such as Africa, peasants or small-scale farmers have practised intercropping since old times. In this study, an investigation was carried out to determine whether intercropping increased production for small-scale farming in a semi-arid region (Free State, South Africa). Crop productivity of maize and bean intercropping systems was evaluated in terms of crop yield and growth. The effect of radiation and water utilisation by these systems was measured to determine their productivity. Field trials were carried out during three summer crop growing seasons (plant densities, row orientation and sowing date trials. In all growing seasons, rainfall was below normal, and air temperatures were normal. The total land equivalent ratios for yield and growth ranged between 1.06 to 1.58 and 1.38 to 1.86 respectively, showing yield and growth advantage of intercropping. Concerning radiation and water use, the intercropping of maize and beans had both radiation and water use efficiencies (RUE and WUE, respectively) as high as maize sole cropping, and intercropping RUE and WUE were greater than bean sole cropping. >From these results, it has been concluded that maize-bean intercropping can be recommended to small-scale farmers in this semi-arid region. Water SA Vol.29(4): 381-388

Effects of plant population and nitrogen fertilizer on yield and efficiency of maize-bean intercropping

Nitrogen supply and plant population are basic parameters for cereal-legume intercropping. In order to study plant population and nitrogen fertilizer effects on yield and yield efficiency of maize-bean intercropping, a field experiment was established. Three bean plant populations and three nitrogen levels were used. Maize dry matter accumulation decreased with increases in bean plant population. Competitive effect of intercrop beans on maize yields was high at higher plant populations, being decreased by nitrogen fertilizer; application of 50 kg ha-1 N was very efficient in increasing maize cob yield. Intercropping significantly decreased harvest index of beans in all plant population and nitrogen fertilizer situations. The efficiency of intercropping, compared to sole cropping, was evidenced by the values obtained for Land Equivalent Ratio (LER) for biomass, cob and pod yields that increased with increases in bean plant populations and nitrogen fertilizer levels.

A model of radiation interception and use by a maize–bean intercrop canopy

A modelling study on intercropping was carried out to understand the radiation interception and use. The radiation transmission models on both instantaneous and daily bases were described and validated. For testing the model, photosynthetically active radiation was measured above and beneath a maize–bean intercrop canopy in both north–south (NS) and east–west (EW) rows at Bloemfontein, Free State, South Africa. Both models accurately predicted radiation transmitted through the intercrop canopy throughout the vegetative stage. For the instantaneous model, two methods were compared, namely, the geometrical method versus the statistical method. The geometrical method was equal in radiation transmitted per unit row to the statistical method. The daily amount of radiation intercepted and used by each component crop was estimated. Concerning the radiation utilisation, the intercropping was equivalent in growth efficiency of maize to the sole cropping whereas beans had greater radiation use efficiency in intercropping than in sole cropping, which might explain the intercrop yield advantage.

Interactions of bush bean intercropped with field and sweet maize

Common bean, Phaseolus vulgaris L., is traditionally intercropped with maize by small-scale farmers in northwest Spain. Interactions of genotypes of beans with cropping systems and seasons were studied to determine if selection of bean in sole cropping would be a valid approach to genetic improvement for intercropping. In this experiment, 10 dry bush bean varieties were evaluated in sole cropping and intercropping with two types of maize (field and sweet maize) at two locations for 2 years. The performance of bean genotypes in each cropping system was compared with respect to developmental plant characteristics, seed yield and yield components and food quality traits. A significant bean genotype×cropping system interaction was found for period of flowering and seed yield, and there were significant differences between cropping systems for pods per plant, seed length and seed coat proportion. Intercropping with field maize reduced bean yield by 55% and intercropping with sweet maize reduced bean yield by 44%. Significant and high correlations of bean yields were obtained between sole cropping and intercropping with maize. Mean yields were used to calculate the land equivalent ratios (LERs), which averaged 1.12 for intercropping with field maize and 0.93 for intercropping with sweet maize. Specific variety combinations reached LER values greater than one. Net income was higher for some intercrop patterns than for bush bean sole crop. The most competitive bean varieties yielded the most when intercropped with maize but those varieties were not necessarily the highest yielding in sole cropping. The most competitive bean varieties were the latest to flower. The evaluation of bush bean genotypes for agronomic and food quality traits under sole cropping provides sufficient information to select varieties efficiently for the field maize-bean and sweet maize-bean intercropping systems. Greatest net income was realized when bush beans intercropped with sweet maize, provided a system with higher added value compared to intercropping with field maize.

Association of maize rust and leaf blight epidemics with cropping systems in Hararghe highlands, eastern Ethiopia

Two hundred and eight fields in the Hararghe highlands (Habro, Chercher and Wobera areas), Ethiopia were surveyed during the 1998 and 1999 cropping seasons to determine the occurrence, distribution and importance of maize rust and leaf blight (LB) in five types of maize cropping systems. Sixty four percent of the surveyed fields were intercropped with the proportion of maize ranging from 24% to 68%. Rust incidence and severity among the areas and between years varied. Logistic regression was used to analyse the association of the diseases with cropping systems and practices, geographic area, season and altitude. Crop density, sowing date, variety, area, cropping system and year were significantly associated with rust incidence in a multiple variable model. Low rust incidence had a high probability of association to low crop density, early and optimum sowing, maize–bean intercropping and the 1998 cropping season. High rust incidence had a high probability of association to the Habro area, hybrid varieties and maize–sorghum intercropping. Cropping year and proportion of maize in intercrops were significantly associated with rust severity in a multiple variable model. The severity of rust was higher where the proportion of maize in the intercrop was 25–50%. The Habro area and the 1998 season had a high probability of association with high rust severity. Crop density, altitude and sowing date were significantly associated with LB incidence in a multiple variable model. Sowing at an optimum time had a high probability of association with low (<25%) LB incidence. At low crop density and lower altitude LB was increased.

Comparisons of radiation use efficiency of mono-/inter-cropping systems with different row orientations

Intercropping may be helpful to solve future food problem in developing countries. The aim of this study was to compare production efficiency in intercropping with sole cropping in terms of radiant energy use. For analysing crop radiation capture and utilisation, three indices are often used: the fraction of radiation intercepted (F), radiation use efficiency (RUE) and harvest index (HI). Using those indices, maize–bean intercropping was evaluated and compared with maize and bean sole cropping systems. The findings were as follows: the intercrop F was higher than the sole crop F, the sole maize RUE was higher than the others, and there was no difference in HI among cropping systems. From those results, the intercropping may be equivalent to maize sole cropping in the overall efficiency of radiation interception and use. Therefore, when it is considered that both maize and beans would be planted in a given area of land, intercropping has more efficient radiation harvests than sole cropping. No effect of row orientation was found on F, RUE and HI.

Effect of plant arrangement pattern and irrigation on efficiency of maize (Zea mays) and bean (Phaseolus vulgaris) intercropping system

A field study was conducted on an experimental field of the Maize Research Institute Zemun Polje- Belgrade (latitude: 44° 49′ N), Yugoslavia over a 3 year period (1994–1996). The objective of this study was to find the optimal spatial arrangement of a maize–beans intercrop in irrigated and rainfed farming systems.Plant arrangement patterns in an intercropping system did not significantly affect LAI values in maize compared with a sole crop, while irrigation had a greater positive influence on it. Leaf area values of beans were more sensitive to the same treatments. Microenvironmental conditions in maize–bean mixtures were more favourable for bean crop than for sole beans.An intercropping system had a greater influence on yield components of maize. Component combination 1/2[ratio ]1/2 (maize[ratio ]bean) was most effective in all yield components of maize. Intraspecific competition appears to be more intense than interspecific competition in both crops. Yield component of bean was more sensitive to water regime of the site than to planting pattern in an intercrop. Irrigation increased all yield components of bean (especially pod number). The intercropping system decreased harvest index in both crops compared with monocrops. Maximum total grain yield was in 1994 in irrigated maize–bean intercrop 1/2[ratio ]1/2, with highest efficiency being in an intercrop in irrigation in 1995. The Land Equivalent Ratio (LER), based on grain yield, was consistently greater than 1·0 in an irrigation water regime in 1995. Proportion of maize[ratio ]bean = 1/2[ratio ]1/2 gave the highest increase of yield (LER = 1·54). Under conditions of chernozem soil type in Zemun Polje, with often-expressed dry periods, irrigation is a very important measure for increasing maize–beans intercrop productivity.

Annual soil improving legumes: agronomic effectiveness, nutrient uptake, nitrogen fixation and water use

Annual soil improving legumes have a role in the management of soil fertility under the low-input management conditions of resource poor farmers. Several species have been identified as promising for the sub-humid tropical areas of eastern Africa having bi-modal rainfall. Most of these can be intercropped with species used for food and/or have alternative uses for food, forage or weed suppression. We compared five annual legumes for fixation of atmospheric nitrogen, soil water uptake, soil P and nitrate recovery, effects on subsequent crops and for phosphorus recovery from Busumbu P rock. Canavalia [ Canavalia ensiformis (L.) DC] produced the most biomass, fixed the most N, was most efficient in extraction of soil nitrate, and supplied the most N to subsequent food crops. Not unexpectedly, it was also most effective in improving soil productivity. Mucuna [ Mucuna pruriens (L.) DC var. utilis] produced less biomass than canavalia but derived a greater proportion of plant N from the atmosphere, while crotalaria [ Crotalaria ochroleuca G. Don.] and lablab [ Lablab purpureus (L.) cv. Rongai] fixed little nitrogen. Lablab and soybean [ Glycine max (L.)] produced the least biomass. All legumes and food crops failed to acquire significant amounts of P from Busumbu soft rock on this moderately acidic soil. The ratios of C:P in the legume biomass were high enough to cause an early net immobilization of P. Profile soil water status was highest under soybean and lowest under canavalia, reflecting differences in biomass production by the legumes and the subsequent maize–bean intercrop. Surface soil water was similar for all species, but differences were evident at depth. All legumes except soybean extracted water below 1.3-m depth.