Maize Monocrop Research Articles

Efficacy of intercropping and harvest time modification for reducing field infestation of maize by Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

Most management practices of Sitophilus zeamais Motschulsky, a field-to-post-harvest insect pest of cereals, have focused on post harvest control methods. This experiment was designed to investigate the potential of cropping system and modification of time of harvest to control S. zeamais. Intercropping and harvest time modification had significant (P < 0.05) effect on the number of S. zeamais emerging 42 days post-harvest. For the early harvest (15 weeks after planting (WAP)), the mean number of S. zeamais recorded from a maize monoculture (7.39) was significantly (P < 0.05) higher than the mean numbers of weevils emerging from a maize–soybean intercrop (2.31), but not significantly higher than the number recorded in maize–groundnut (3.87) intercrop. For the late harvest (18 WAP), the mean number of emerged adult observed in the maize–soybean intercrop (6.13) was significantly lower than the mean number of adult emerging from the monocrop maize (13.24). Maize–groundnut intercrop did not significantly reduce field infestation of S. zeamais compared with monocrop maize. Percentage weight loss observed in early harvested maize was significantly (P < 0.0001) lower than what was observed in late-harvested maize. Percentage weight loss was highest in stored maize harvested from monocrop maize plots for the early harvest, whereas intercropping maize with soybean reduced percentage weight loss when harvest was delayed.

Long-term fertilization effects on carbon and nitrogen in particle-size fractions of a Chinese Mollisol

Yan, Y., He, H., Zhang, X., Chen, Y., Xie, H., Bai, Z., Zhu, P., Ren, J. and Wang, L. 2012. Long-term fertilization effects on carbon and nitrogen in particle-size fractions of a Chinese Mollisol. Can. J. Soil Sci. 92: 509� 519. The response of soil organic matter (SOM) dynamics to long-term fertilization may be deduced from changes in the accumulation and distribution of different soil organic carbon (SOC) and nitrogen (N) pools. The SOC and N in particle-size fractions were therefore measured to assess the influences of pig manure and synthetic fertilizer application on the characteristics of these pools. A long-term fertilization experiment, established in 1979 in the Mollisol area (Gongzhuling, China) was used for this study. Composite soil samples (0� 20 cm) were collected in 2005 from 12 treatment plots that had received annual applications of pig manure, synthetic fertilizers or combinations of both. Soils were fractionated into fine clay (B0.2 mm), coarse clay (0.2� 2 mm), silt (2� 50 mm), fine sand (50� 250 mm) and coarse sand (250� 2000 mm) and then SOC and N contents in each particle-size fraction were measured. Although most of the SOC and N were associated with clay and silt fractions, the large proportion of silt in the soil mass played a key role in the retention of SOC and N. The application of pig manure alone increased accumulation of SOC and N in each particle-size fraction, but preferential enrichment was found in the coarse sand fraction. This indicates that pig manure is efficient in restoring SOM in the temperate Chinese Mollisol under a tilled maize (Zea mays L.) monocropping system and having a long frozen period in winter. The application of synthetic fertilizers had no clear effect on SOC and N accumulation or their distribution in particle-size fractions. However, the combined application of pig manure and synthetic fertilizers enhanced the accumulation of SOC and N in all particle-size fractions, and led to a shift of SOC and N from fine to coarse particles. We extended the hierarchy model for SOC protection to consider a shift in SOC accumulation from fine to coarse particles, depending on the initial SOC content of the specific soil. The findings reveal a clear positive interaction between pig manure and synthetic fertilizers that may improve the quantity of SOM in the temperate Chinese Mollisol.

Long-term fertilization effects on carbon and nitrogen in particle-size fractions of a Chinese Mollisol

Yan, Y., He, H., Zhang, X., Chen, Y., Xie, H., Bai, Z., Zhu, P., Ren, J. and Wang, L. 2012. Long-term fertilization effects on carbon and nitrogen in particle-size fractions of a Chinese Mollisol. Can. J. Soil Sci. 92: 509–519. The response of soil organic matter (SOM) dynamics to long-term fertilization may be deduced from changes in the accumulation and distribution of different soil organic carbon (SOC) and nitrogen (N) pools. The SOC and N in particle-size fractions were therefore measured to assess the influences of pig manure and synthetic fertilizer application on the characteristics of these pools. A long-term fertilization experiment, established in 1979 in the Mollisol area (Gongzhuling, China) was used for this study. Composite soil samples (0–20cm) were collected in 2005 from 12 treatment plots that had received annual applications of pig manure, synthetic fertilizers or combinations of both. Soils were fractionated into fine clay (&lt;0.2 µm), coarse clay (0.2–2 µm), silt (2–50 µm), fine sand (50–250 µm) and coarse sand (250–2000 µm) and then SOC and N contents in each particle-size fraction were measured. Although most of the SOC and N were associated with clay and silt fractions, the large proportion of silt in the soil mass played a key role in the retention of SOC and N. The application of pig manure alone increased accumulation of SOC and N in each particle-size fraction, but preferential enrichment was found in the coarse sand fraction. This indicates that pig manure is efficient in restoring SOM in the temperate Chinese Mollisol under a tilled maize (Zea mays L.) monocropping system and having a long frozen period in winter. The application of synthetic fertilizers had no clear effect on SOC and N accumulation or their distribution in particle-size fractions. However, the combined application of pig manure and synthetic fertilizers enhanced the accumulation of SOC and N in all particle-size fractions, and led to a shift of SOC and N from fine to coarse particles. We extended the hierarchy model for SOC protection to consider a shift in SOC accumulation from fine to coarse particles, depending on the initial SOC content of the specific soil. The findings reveal a clear positive interaction between pig manure and synthetic fertilizers that may improve the quantity of SOM in the temperate Chinese Mollisol.

On-farm evaluation of yield and economic benefit of short term maize legume intercropping systems under conservation agriculture in Malawi

Low crop yields due to continuous monocropping and deteriorating soil health in smallholder farmers’ fields of sub-Saharan Africa have led to a quest for sustainable production practices with greater resource use efficiency. The aim of the study was to elucidate the short term effects of conservation agriculture (CA) systems on soil quality, crop productivity and profitability. In Balaka market and Ntonda sections of Manjawira Extension Planning Area (EPA), in Ntcheu district, central Malawi, we compared continuous monocropped maize (Zea mays) under conventional tillage practice (CP) with different CA systems in continuous monocropped maize (CAM) and intercropping with pigeonpea (Cajanus cajan) (CAMP), Mucuna pruriens (CAMM), and Lablab purpureus (L.) (Sweet) (CAML). The study was conducted from 2008 to 2011 in 72 plots in 24 farmers’ fields. In Balaka market section CA plots with maize+legumes produced up to 4.3Mgha−1 of vegetative biomass against 3.5Mgha−1 for maize alone in CP. In Ntonda section CA plots with maize+legumes produced up to 4.6Mgha−1 of vegetative biomass against 2.4Mgha−1 for maize alone in CP. In both sections, during the entire study period, CA did not have a negative effect on crop yields. During the drier seasons of 2009/10 and 2010/11, CA had a positive effect on maize grain yield at both sites (average yield of 4.4 and 3.3Mgha−1 in CA and CP respectively). However, associating maize with legumes reduced maize yields compared to CAM particularly in drier years of 2009–10 and 2010–11. Farmers spent at most 47daysha−1 producing maize under CA systems compared to 65daysha−1 spent under conventional tillage practices. However, total variable costs were higher in CA systems compared to conventional practice (at most US$416 versus US$344ha−1). CAMP resulted in more than double gross margin compared to CPM (US$705 versus US$344ha−1). Infiltration estimated as time to pond was highest in CA maize legume intercrops (8.1s) than CP (6.8s). Although it was not feasible to directly estimate effects on water balances of these farmer-managed experiments, it can be assumed that the yield differences between CA and CP could be attributed to tillage and crop residue cover since other farm operations were generally the same. Intercropping maize and pigeonpea under CA presents a win-win scenario due to crop yield improvement and attractive economic returns provided future prices of maize and pigeonpea grain remain favourable.

Growth and yield of maize and timber trees in smallholder agroforestry systems in Claveria, northern Mindanao, Philippines

On-farm experiments were conducted in the Philippines to study over a 4-year period the growth of two timber trees, gmelina (Gmelina arborea R. Br.) and bagras (Eucalyptus deglupta Blume), and their impact on the grain yield of intercropped maize. The experiment consisted of maize monocropping plots (control) and maize intercropped between trees planted in block (2 × 2.5 m), and hedgerow arrangement (1 × 10 m). Three maize crops were planted in the block plots before canopy closure, and seven maize crops were planted in the hedgerow and monocropping plots. Maize grain yield in the hedgerow and in the block arrangement with gmelina were respectively 37% (16.58 tons ha−1) and 68% (8.3 tons ha−1) lower than in monocropping (26.21 tons ha−1). In the plots with bagras, maize grain yield in hedgerow and in block arrangement were respectively 19% (24.8 tons ha−1) and 66% (10.4 tons ha−1) lower than in monocropping (30.6 tons ha−1). For both tree species, the diameter at breast height (dbh) was greater in hedgerow than in block arrangement, with the difference being more pronounced with age. It was estimated that gmelina planted in hedgerows would produce 6–8 m3 ha−1 of merchantable volume more than if planted in block. The study verifies the hypothesis that intercropping between widely-spaced trees rows (planted at 10 m or more) is more profitable and feasible to smallholders than either maize monocropping or woodlots, and concludes with recommendations on how to further improve the productivity of tree-intercropping systems.

EFFECT OF REDUCED TILLAGE AND MINERAL FERTILIZER APPLICATION ON MAIZE AND SOYBEAN PRODUCTIVITY

SUMMARYReduced tillage is said to be one of the potential ways to reverse land degradation and ultimately increase the productivity of degrading soils of Africa. We hypothesised that crop yield following a modest application of 2 t ha−1 of crop residue in a reduced tillage system is similar to the yield obtained from a conventional tillage system, and that incorporation of legumes in a cropping system leads to greater economic benefits as opposed to a cropping system involving continuous maize. Three cropping systems (continuous maize monocropping, legume/maize intercropping and rotation) under different tillage and residue management systems were tested in sub-humid western Kenya over 10 seasons. While soybean performed equally well in both tillage systems throughout, maize yield was lower in reduced than conventional tillage during the first five seasons but no significant differences were observed after season 6. Likewise, with crop residue application, yields in conventional and reduced tillage systems are comparable after season 6. Nitrogen and phosphorus increased yield by up to 100% compared with control. Gross margins were not significantly different among the cropping systems being only 6 to 39% more in the legume–cereal systems relative to similar treatments in continuous cereal monocropping system. After 10 seasons of reduced tillage production, the economic benefits for our cropping systems are still not attractive for a switch from the conventional to reduced tillage.

Crop production versus surface-water regulation: assessing tradeoffs for land-use scenarios in the Tat Hamlet Watershed, Vietnam

Local land uses play a critically important role in regulating hydrological services like surface-water runoff. This runoff influences the supply of water to streams and lowland agriculture. Land-use management decisions, in turn, are influenced by economic return. This article examines the tradeoffs between surface-water runoff regulation and income from crop production by using the land-use change impact assessment model and an economic analysis for a case study in Tat Hamlet Watershed, north Vietnam. The traditional composite swidden agriculture was used as baseline scenario, since it has been practised by farmers in the study area for decades. Two alternative scenarios were tested and compared with the composite swidden agriculture: expansion of maize monoculture and introduction of rubber plantations in the uplands. Among the land-use scenarios tested, rubber plantations appear to be better alternatives than maize monocropping in terms of surface-water regulation and improving economic return. However, implementation should consider the interests of local stakeholders as well as an analysis of possible risks and uncertainties involved.

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.

Evaluation participative &lt;em&gt;ex ante&lt;/em&gt; de propositions de la recherche. Cas d’application dans le sud du Togo

L’objectif de cette étude a été d’expérimenter une méthode d’évaluation participative d’options techniques au sud du Togo. Pour répondre aux besoins face aux problèmes de fertilité des sols dans un contexte de systèmes mixtes agriculture élevage, des chercheurs ont évalué avec les diverses catégories d’acteurs le potentiel d’adoption de l’association du maïs, plante à fonction mixte alimentaire (grain) et fourragère (paille), et du Mucuna pruriens, légumineuse à cycle long employée comme fourrage et pour améliorer la fertilité des sols. L’association fertilisée avec des engrais chimiques a été dénommée MME ci-après. La méthode utilisée a mobilisé des outils d’analyse de la méthode active de recherche participative (MARP) et a compris quatre phases. La première correspondait à la description générale de l’ensemble de la région d’étude pour identifier des sites représentatifs à partir de la littérature et d’entretiens exploratoires. La seconde phase a permis la caractérisation de la diversité des producteurs à partir d’entretiens auprès des personnes ressources des sites retenus. La troisième phase a concerné la sélection participative d’un éventail d’options techniques comprenant l’association MME mais aussi des pratiques locales présentant des similitudes avec l’association MME, ainsi que d’autres propositions alternatives de la recherche pour améliorer la fertilité des sols et assurer l’alimentation fourragère des animaux. Cette sélection a été réalisée par un échantillon de producteurs représentatifs de leur diversité. Il leur a été demandé de hiérarchiser les différentes options techniques présentées lors de visites de parcelles expérimentales ou à l’aide de supports visuels. Ils ont utilisé des notes ou des cailloux compte tenu de la forte proportion d’illettrisme. La quatrième phase a été celle de l’évaluation aux dires de producteurs des effets perçus des différentes options sur la gestion des ressources agropastorales (eau, sol, biodiversité), leur acceptabilité ou leur rentabilité en fonction du coût de la main d’oeuvre. Cette méthode a été appliquée dans trois villages du sud du Togo. Dans ces villages, six principales catégories de producteurs ont été identifiées : les propriétaires terriens, les locataires de terres, les membres d’organisations paysannes, les producteurs lettrés, les producteurs illettrés, et les femmes. En plus du MME, six options ont été retenues dont l’association MME avec des variantes issues de pratiques locales, soit l’association maïs et Mucuna à cycle long mais sans l’usage d’engrais (MM), l’association maïs et Mucuna à cycle court et à base d’engrais (MMCE), l’association maïs et Mucuna à cycle court sans l’usage d’engrais (MMC), et maïs en culture seul avec apport massif d’engrais (ME). Les deux autres options ont été proposées par la recherche : maïs entouré de haies vives de légumineuses fourragères destinées à du bétail en stabulation contrôlée et dont le fumier était ensuite épandu au champ (MHF), et culture en couloirs de maïs et de Cajanus cajan. L’association MME a été l’option préférée des propriétaires terriens, des lettrés et des membres d’organisations paysannes. Chez les femmes, l’option privilégiée a été l’association MM compte tenu de leurs faibles ressources financières mais aussi de leur insécurité foncière. Chez les locataires des terres et les producteurs illettrés, l’option favorite a été l’association MMCE qui permettait le maintien de la seconde saison de culture. L’évaluation des différentes options a montré que l’association MME et l’option MHF ont été jugées par la majorité des catégories de producteurs comme ayant les effets les plus positifs sur les ressources agropastorales. Les associations MME et MMCE ont été considérées comme étant les plus acceptables socialement, notamment chez les propriétaires terriens mais aussi chez les vulgarisateurs, les consommateurs et les commerçants également interrogés ; venait ensuite l’option MHF. La rentabilité a été la meilleure pour les associations MM et MME et la plus faible pour les deux autres alternatives proposées par la recherche. Cette méthode d’évaluation permet de valoriser l’expertise des producteurs. Elle repose sur la perception que les producteurs ont des effets des technologies. Une perception positive constitue un des premiers facteurs d’adoption d’une proposition de la recherche. Mais pour cela du temps et des outils appropriés doivent être consacrés à l’étape de formation des producteurs sur les différentes options pour que cette perception ne soit pas biaisée par la qualité de l’information donnée par le chercheur. Cette évaluation permet en outre d’identifier ou d’adapter des variantes locales aux options pré-identifiées par les chercheurs. Les efforts de recherche-développement doivent se concentrer sur les processus de ces adaptations participatives.

Effect of different plant densities on the diversity of arbuscular mycorrhizal fungi community in a long-term maize monocrop system

The association between terrestrial plants and arbuscular mycorrhizal (AM) fungi is one of the most widespread mutualistic plant-fungus interactions in natural and cropping systems. We studied the effect of different plant densities (70,000 and 100,000 plant ha-1) on species diversity and community structure of AM fungi associated with maize (Zea mays L.) in a long-term crop production experiment established in Martonvásár, Hungary. Based on the differences in small subunit (SSU)/18S ribosomal genes nested-PCR procedure was used to identify groups of AM fungi that are active in the colonization of maize roots. Shannon-Wiener diversity index of AM fungi were 1.43 ± 0.37 and 1.31 ± 0.50 at 70,000 plant ha-1 and 100,000 plant ha-1 respectively. All of sequence types we found belonging to the Glomus clade. Besides Glomus A fungi, only the members of the Glomus B group occurred, however at significantly lower frequency. There were differences in the phylogenetic group composition of AM fungi demonstrating the effect of different plant densities on the diversity of arbuscular mycorrhizal fungi.

ROTATION IN CONSERVATION AGRICULTURE SYSTEMS OF ZAMBIA: EFFECTS ON SOIL QUALITY AND WATER RELATIONS

SUMMARYConservation agriculture (CA) systems are based on minimal soil disturbance, crop residue retention and crop rotation. Although the capacity of rotations to break pest and disease cycles is generally recognized, other benefits of crop rotations in CA systems are seldom acknowledged and little understood. We monitored different conventional and CA cropping systems over the period from 2005 to 2009 in a multi-seasonal trial in Monze, southern Zambia. Both monocropped maize and different maize rotations including cotton and the green manure cover crop sunnhemp (Crotalaria juncea) were compared under CA conditions, with the aim of elucidating the effects of crop rotations on soil quality, soil moisture relations and maize productivity. Infiltration, a sensitive indicator of soil quality, was significantly lower on conventionally ploughed plots in all cropping seasons compared to CA plots. Higher water infiltration rate led to greater soil moisture content in CA maize treatments seeded after cotton. Earthworm populations, total carbon and aggregate stability were also significantly higher on CA plots. Improvements in soil quality resulted in higher rainfall use efficiency and higher maize grain yield on CA plots especially those in a two- or three-year rotation. In the 2007/08 and 2008/2009 season, highest yields were obtained from direct-seeded maize after sunnhemp, which yielded 74% and 136% more than maize in the conventionally ploughed control treatment with a continuous maize crop. Even in a two-year rotation (maize-cotton), without a legume green manure cover crop, 47% and 38% higher maize yields were recorded compared to maize in the conventionally ploughed control in the two years, respectively. This suggests that there are positive effects from crop rotations even in the absence of disease and pest problems. The overall profitability of each system will, however, depend on markets and prices, which will guide the farmer's decision on which, if any, rotation to choose.

Non-target effects of the ‘push–pull’ habitat management strategy: Parasitoid activity and soil fauna abundance

We assessed the non-target effects of a habitat management system (‘push–pull’) on maize stemborer specialist natural enemy activity and soil Collembola. Two study sites in western Kenya were sampled. There were two treatments at each site, maize monocrop and ‘push–pull’. The latter comprised an intercrop of maize and Desmodium, Desmodium uncinatum Jacq., with Napier grass, Pennisetum purpureum (Schumach), as a trap crop planted around the edge of the plot (spaced 1 m from main crop). Trichogramma spp. were recovered from stemborer eggs while Cotesia sesamiae and Cotesia flavipes were recovered from stemborer larvae, and Dentichasmias busseolae from pupae. Mean number of eggs parasitized was significantly higher in the maize monocrop than in the ‘push–pull’ plots however proportions parasitized did not differ between the two systems. The number of larvae and pupae parasitized and dead from causes other than parasitism similarly did not differ between cropping systems. Proportions of larvae and pupae parasitized were significantly higher in the ‘push–pull’ than in the monocrop plots, indicating that the activity of larval and pupal parasitoids was enhanced. C. sesamiae female wasps were attracted to the volatiles from Desmodium flowers but not those from the leaves in a four-arm olfactometer bioassay. A total of 1530 individual Collembola in seven families were recovered from the plots. The ‘push-pull’ strategy did not have any significant effect on Collembola abundance and dominance. The factors underlying these observations and their implications are discussed.

Carbon and nitrogen pools in different aggregates of a Chinese Mollisol as influenced by long-term fertilization

Purpose It is known that soil organic matter (SOM) dynamics are sensitive to fertilizations, but it is different from soil to soil. It is unclear how the long-term applications of organic manure and mineral fertilizers impact the accumulation and distribution of soil organic carbon (SOC) and total nitrogen (TN) especially in soil aggregate fractions of Chinese Mollisols, which have been intensively cultivated for decades under maize monocropping and conventional tillage ways. Thereby, the research of this kind is very important for the sustainable use of agricultural land in China, where land resources are extremely limited for its huge population. The objectives of this study were to identify how the long-term fertilization treatments would affect the aggregate, SOC and TN distribution pattern in the Chinese Mollisol, and how soil aggregation contribute to the storage and stabilization process of SOC and TN.

Distinct sporulation dynamics of arbuscular mycorrhizal fungal communities from different agroecosystems in long-term microcosms

The aim of this study was to investigate sporulation dynamics of arbuscular mycorrhizal fungal (AMF) communities from agroecosystems differing in land use intensity in long-term experimental microcosms. These were set up with characteristic grassland plants ( Lolium perenne, Trifolium pratense, Plantago lanceolata), and inoculated with soils from several grasslands and arable lands subjected to crop rotation or continuous monocropping. The microcosms were maintained under ambient light and temperature conditions over 3 years. A novel, localized sampling scheme was applied for attaining exclusively the newly formed spores at bimonthly intervals. Overall, 39 AMF species were detected by morphological spore identification. Some species were recovered from all sites, others exclusively from arable lands, or grasslands, or from all sites except under maize monocropping. Clear seasonal and successional AMF sporulation dynamics were revealed, implying different life strategies of different AMF species. A first group of Glomus spp., including G. mosseae, sporulated rapidly during the first season. A second group, including G. constrictum and G. fasciculatum, sporulated late in the first season and replaced the first group during subsequent seasons. A large third group, including G. invermaium, G. macrocarpum and G. sinuosum, sporulated much later, in the second or third season. Acaulospora, Archaeospora and Ambispora spp. sporulated mainly during spring and early summer, Scutellospora and Cetraspora spp. only in fall. While in the microcosms derived from arable lands, cumulative species numbers did not increase anymore after 2 years, the numbers still increased significantly in the microcosms from the grasslands indicating longer lasting periods of sporulation cycles. Remarkably, the arable land under organic farming produced the highest AMF species richness, even higher than the grasslands. In conclusion, AMF communities from distinct agro-ecosystems differed in species composition and seasonal and successional sporulation dynamics.

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.

Regulation of AhFRO1, an Fe(III)‐chelate reductase of peanut, during iron deficiency stress and intercropping with maize

Iron deficiency-induced chlorosis in peanut during anthesis was alleviated when peanut was intercropped with maize in field and pot experiments. Iron acquisition of graminaceous plants is characterized by the synthesis and secretion of the iron-chelating phytosiderophores. Compared to the roots of monocropped maize, the roots of maize intercropped with peanut always secreted higher amounts of phytosiderophores during peanut anthesis. For non-graminaceous plants, reduction of ferric to ferrous iron on the root surface is the rate-limiting step for mobilizing iron from soil. The full-length cDNA, AhFRO1, which is encoding an Fe(III)-chelate reductase, was isolated from peanut. AhFRO1 expression in yeast conferred Fe(III)-chelate reductase activity to the cells. Consistent with its function in iron uptake, AhFRO1 was determined to be a membrane protein by transient expression analysis. AhFRO1 mRNA accumulated under iron deficiency conditions. During pre-anthesis, the Fe(III)-chelate reductase activity and the transcript levels of AhFRO1 were similar in monocropped and intercropped peanut. When the iron deficiency-induced chlorosis developed in the monocropped peanuts, both the Fe(III)-chelate reductase activity of peanut and the transcript levels of AhFRO1 were higher in intercropped than in monocropped peanuts, which is consistent with the secretion of phytosiderophores by maize roots. We conclude that AhFRO1 in peanut and phytosiderophores from maize co-operate to improve the iron nutrition of peanut when intercropped with maize.

Crop sequences in no-tillage system: effects on soil fertility and soybean, maize and rice yield

Decomposing crop residues in no-tillage system can alter soil chemical properties, which may consequently influence the productivity of succession crops. The objective of this study was to evaluate soil chemical properties and soybean, maize and rice yield, grown in the summer, after winter crops in a no-tillage system. The experiment was carried out in Jaboticabal, SP, Brazil (21 ° 15 ' 22 '' S; 48 ° 18 ' 58 '' W) on a Red Latosol (Oxisol), in a completely randomized block design, in strip plots with three replications. The treatments consisted of four summer crop sequences (maize monocrop, soybean monocrop, soybean/maize rotation and rice/bean/cotton rotation) combined with seven winter crops (maize, sunflower, oilseed radish, pearl millet, pigeon pea, grain sorghum and sunn hemp). The experiment began in September 2002. After the winter crops in the 2005/2006 growing season and before the sowing of summer crops in the 2006/2007 season, soil samples were collected in the layers 0-2.5; 2.5-5.0; 5-10; 10-20; and 20-30 cm. Organic matter, pH, P, K+, Ca2+, Mg2+, and H + Al were determined in each soil sample. In the summer soybean/maize rotation and in maize the organic matter contents and P levels were lower, in the layers 0-10 cm and 0-20 cm, respectively. Summer rice/bean/cotton rotation increased soil K levels at 0-10 cm depth when sunn hemp and oilseed radish had previously been grown in the winter, and in the 0-2.5 cm layer for millet. Sunn hemp, millet, oilseed radish and sorghum grown in the winter increased organic matter contents in the soil down to 30 cm. Higher P levels were found at the depths 0-2.5 cm and 0-5 cm, respectively, when sunn hemp and oilseed radish were grown in the winter. Highest grain yields for soybean in monoculture were obtained in succession to winter oilseed radish and sunn hemp and in rotation with maize, after oilseed radish, sunn hemp and millet. Maize yields were highest in succession to winter oilseed radish, millet and pigeon pea. Rice yields were lowest when grown after sorghum.

Crop type influences soil aggregation and organic matter under no-tillage

The adaptation of no-tillage system in tropical regions depends on the suitable choice of summer and winter crops which should contribute to improvement of soil properties. The aim of the present study was to determine the effect of crop sequences on soil aggregation and contents of organic C and polysaccharides in aggregates of a Rhodic Eutrudox under no-tillage. The treatments consisted of the combination of four summer crop sequences and seven winter crop sequences. The summer crop sequences were: maize monocrop ( Zea mays L.) (MM); soybean monocrop ( Glycine max (L.) Merrill) (SS); crop sequence of soybean/maize/soybean/maize (SM); crop sequence of rice ( Oryza sativa L.)/bean ( Phaseolus vulgaris L.)/cotton ( Gossypium hirsutum L.)/bean (RB). The winter crops were: maize, sunflower ( Helianthus annuus L.), radish ( Raphanus sativus L.), pearl millet ( Pennisetum americanum (L.) Leeke), pigeon pea ( Cajanus cajan (L.) Millsp), grain sorghum ( Sorghum bicolor (L.) Moench) and sunn hemp ( Crotalaria juncea L.). The highest total organic C, total polysaccharides and dilute acid-extracted polysaccharides contents were found in 2.00–1.00 mm water-stable aggregates and the lowest contents were found in <0.25 mm aggregates. The maize monocrop provided the highest water-stability of soil aggregates. This crop sequence provided the highest content of total organic C and dilute acid-extracted polysaccharides in aggregates with diameter of 6.30–2.00 mm. This indicates that the influence of crops on the stability of aggregates is mediated by total organic C and easily hydrolysable polysaccharides (polysaccharides other than cellulose) in the soil. There were no differences among effects of the winter crops (maize, sunflower, oilseed radish, pearl millet, pigeon pea, grain sorghum and sunn hemp) on the soil aggregation.

Interactions between plants in intercropped maize and common bean

AbstractBACKGROUND: Intercropping maize (Zea mays L.) with common bean (Phaseolus vulgaris L.) can give silage yields that are as high as with monocropped maize, but with more crude protein. Interactions between maize and common bean intercropped in the UK were assessed at a range of plant densities (maize 100 000, 75 000 and 50 000 plants ha−1 and beans at a fixed density of 50 000 plants ha−1).RESULTS: In monoculture, maize yield per plant increased as planting density decreased from 100 000 to 50 000 plants ha−1. At a density of 50 000 maize plants ha−1, both dry weight yield per plant and shoot N concentrations of maize were greater when intercropped with 50 000 Type III (bush‐type) bean plants ha−1 than in monoculture (196.4 g plant−1 and 167.0 g plant−1; 21.6 g N kg−1 dry mass and 17.4 g N kg−1 dry mass, respectively), but intercropping Type IV (climbing) beans at this density combination had no effects on either maize plant weight or shoot N concentration. Invariably, however, the beans grown at 50 000 plants ha−1 were adversely affected by competition with maize at all densities. Weight per plant of both Type III (bush‐type) and Type IV (climbing) beans grown in competition with 50 000 maize plants ha−1 was only about half that of when grown alone. Intercropping gave increased mycorrhizal colonization of both species, especially in unfertilized plots, and gave a higher shoot N concentration in the maize. The beans had more nodules in the intercrop than in the monocrop.CONCLUSIONS: Intercropping maize with Type III common bean at 50 000 plants of each species ha−1 increases yield per maize plant above that of monoculture maize at 50 000 plants ha−1, despite plant density being doubled. This increase is brought about by increased maize shoot N concentration. Mycorrhizal infection of both species, and bean plant nodulation, are stimulated, and N moves from the beans to the maize. Copyright © 2008 Society of Chemical Industry

The Potential of Cowpea, Pigeonpea and Greengram to Supply Mineral Nitrogen to Maize under Intercropping on Ferralsol in Muheza-Tanga Tanzania

An incubation experiment was carried out at Mlingano Agricultural Research Institute, Tanga-Tanzania, to study the nitrogen mineralization in the Ferralsol under maize- cowpea, pigeonpea and greengram intercropping systems. Top soil (0 – 20 cm) samples were collected from previously maize intercropped and monocropped plots before the onset of rains in subsequent seasons. The fresh soil samples were sieved through a 6 mm screen, 250 g portions placed in 500 ml capacity volumetric flasks, then incubated at 60% field capacity for 42 days in a glasshouse. Destructive samplings were done at 14 day intervals and analysed for mineral N. The N mineralization increased with incubation time, with cowpea and pigeonpea having significantly higher quantities at the 42nd day sampling compared to the maize monocropped plots. The proportions of the mineral N at 14th day where maize stover was removed were 77%, 55%, 92% and 90% of that at the 42nd day for soil from the cowpea, pigeonpea, greengram and monocropped maize treatments, respectively. The respective proportions where the stover was incorporated were 81%, 53%, 96% and 77%. Such high proportions coupled with low maize N demand indicated possibilities of the N being leached, leading to maize plants ’ N deficiency symptoms. It was concluded that the N mineralization in this cropping system is not in synchrony with the maize N demand, necessitating top dressing of N fertilizers. Keywords : Ferralsol; Incubation; Intercropping; Mineral N East African Journal of Sciences Vol. 2 (2) 2008: pp. 119-123