Maize-based Cropping Research Articles

Effect of Tank Silt Application on Productivity and Economics of Maize-Based Production System in Southern Rajasthan

Field experiments were carried out during 2008–09 to 2009–10 on farmers’ field in the Operational Research Project area of Bhilwara district of Rajasthan to evaluate the effect of tank silt on productivity and economics of maize based cropping systems. The experiments were conducted at 10 farmers’ field from five villages in one hectare with or without tank silt. Results revealed that application of tank silt with improved management practices recorded an increase of 36.6% in grain yield of maize over non-application of tank silt which was only 24.9% in case of farmers’ practice. Application of tank silt benefited subsequent crop grown during rabi and produced a significant residual response in maize-wheat, maize-mustard and maize-taramira cropping systems. Application of tank silt brought out an increase of 18 to 32% in the productivity of different maize-based cropping systems under improved practice. Application of tank silt with improved and farmers’ practice increased the WUE of maize by 24 and 21% over the non-application of tank silt, respectively.

Maize cropping (Zea mays L.) assessment by simple performance-based index

A simple performance-based index was used to test performance among maize cropping systems referring to the food and raw material production, nutrient cycling and greenhouse gases regulation. Those indices are tools for aggregating and simplifying agroecosystem impact on the environment. The data were acquired from a long-term experiment at the Rimski Šančevi experimental station of the Institute of Field and Vegetable Crops, Novi Sad, Serbia. Observed indicators were compared by using datasets from 2001 to 2010, across five maize cropping systems. Maize continuous cropping resulted with decrease in the utilization of the agroecological potential compared with the fertilized crop rotation. Long term maize-based cropping resulted with differences in soil organic carbon content, soil pH and temporal soil NO3. However, recommended fertilizers application and crop rotation contributed to the overall agroecosystems ability to decrease the anthropogenic pressure. Accordingly, it was found that yield decrease resulted mostly from inability of the cropping systems to utilize agricultural management (tillage, fertilization, etc.) in variable environmental conditions. For the investigated trial the performance based index showed that a 2-year maize cropping had the highest capacity for sustainable maize growing.

Options to improve family income, labor input and soil organic matter balances by soil management and maize–livestock interactions. Exploration of farm-specific options for a region in Southwest Mexico

AbstractFarming systems in the Costa Chica region in Mexico face limitations linked to low yields and soil fertility degradation. Several alternative maize-based cropping systems have been proposed to improve current limitations. These field-level options need to be evaluated at farm level in order to assess their feasibility, taking into account input requirements, contributions to self-sufficiency in food and long-term soil fertility, and the availability of labor. In this study, we defined four scenarios to explore consequences of changes in current farming systems for eight typical farms in the region; the first two scenarios comprised redressing current imbalances in crop nutrition and organic matter (OM) supply, respectively, and the last two scenarios explored high fertilizer input and animal husbandry. Farms responded in different ways to the various options depending on available land, current soil quality, current cropping systems and presence of livestock. Improvements in crop nutrition based on mineral fertilizers increased family income but only had substantial effects on soil OM (SOM) balances when fertilizer rates were double the amount currently subsidized. Addition of organic fertilizers resulted in positive effects on SOM balance, but with often strong trade-offs with family income due to costs of acquisition, transport and application. Animals played an important role in increasing SOM balances, but had relatively little effect on improving family income. The results demonstrated that improvements in family income and SOM balance at farm scale were feasible but that without more fundamental system changes trade-offs between short-term yield increases and longer-term soil fertility increases should be expected. The results highlight the need for policies that take into account farm-specific differences in crop and livestock intensification opportunities.

Assessment of the Profitability and the Effects of Three Maize-Based Cropping Systems on Soil Health in Western Africa

Enhanced livelihoods for populations, especially smallholder farmers in sub-Saharan Africa may be achieved through improved cropping systems. We assessed the economic returns from maize grain yield and the effects of three cropping systems on soil properties in an eight-year study segmented in cycles of two years each: continuous maize (Zea mays L.), maize-mucuna (Mucuna pruriens var. utilis), and maize-pigeon pea (Cajanus cajan). The rainfall pattern in the study region allows for two growing seasons per year, leading to four growing seasons per cycle. Nitrogen (N) and phosphorus (P) fertilizer rates were imposed on maize in each system and maize grain yields and associated cash values as well as soil properties were measured. Seeding mucuna and pigeon pea crops into maize crop in the first year did not result in maize grain yield increases from N and P fertilizers in the subsequent year. Continuous maize system increased mean maize grain yields by 6.2 to 60.3% in the fallow year of the 2002-2003 and 2006-2007 cycles and by 5.1 to 8.2% on a cycle basis in the 2002-2003 cycles. For the remaining periods of the study, mucuna and pigeon pea based maize cropping increased grain yields by 28.6 to 47.6%, 22 to 260% and 28.3 to 136.1% in fallow year, non-fallow years and on a cycle basis, respectively, compared to yields under continuous maize. On a cycle basis, economic returns for maize-mucuna and maize-pigeon pea based systems were 105.1 and 66.5%, respectively, higher than that for continuous maize. The mucuna and pigeon pea based systems increased the initial soil total carbon (C) content by 55 and 69%, respectively, resulted in increases of 110 to117%, 33 to 63%, 29%, and 16-17% for exchangeable Ca2+, Mg2+, K+ and total cation exchange capacity (CEC), respectively, and enhanced water stable macroaggregates stability, compared to continuous maize. Maize mucuna and pigeon pea-based maize cropping systems with mucuna and pigeon crops in alternate years should be advised towards sustaining enhanced profitability and improved soil physical and chemical properties.

Phosphorus agronomic efficiency in maize-based cropping systems: A focus on western Kenya

Phosphorus (P) is facing a quantity and quality supply issue and increasing its use efficiency is important for its continued use and profitability in crop production. The objective of this study was to determine how agronomic efficiency of P (PAE) in different environments and management systems in western Kenya is affected by N application, inherent soil fertility and organic resources. We used data constituting over 2700 data points from 126 farm fields of 25 different studies conducted from 1996 to 2009. Potassium (K) deficiency is negligible in western Kenya while ommission of P and N result in a 50% and 43% reduction in yield, respectively, relative to a full NPK treatment. In poor fields (low control yields) PAE was low in the absence of fertilizer N. Overall, lack of N application decreased PAE from 29 to 19kg grain kg−1P. Boundary analysis indicate that maximum yields are reached at about 50kgPha−1. Using a marginal rate of return of 100%, maximum P application rate for western Kenya should be 38kgPha−1. Without chemical N fertilizer application, organic resources increased PAE by 60–100% compared to continuous maize system without organic resources. Maximum PAE decreased at increased plant-available soil P and soil coarsiness. Our analysis represents best management practices and PAE may be lower than the reported values under farmer's conditions.

Sustainability of European maize-based cropping systems: Economic, environmental and social assessment of current and proposed innovative IPM-based systems

There is strong social and political pressure to reduce pesticide use in European agriculture. Evaluating the sustainability of cropping systems is a complex task due to the conflicting objectives underlying its economic, social and environmental dimensions. Multi-criteria assessment of different Integrated Pest Management (IPM) scenarios and evaluation of the most sustainable options at regional, national and European level is essential. Within the EU Network of Excellence ENDURE, two expert-based surveys were conducted (i.e. interviews), where experts from four European regions (northern region, Denmark and The Netherlands; central-eastern, Tolna and Békés counties in Hungary; south-western, Ebro Valley in Spain; southern, Po Valley in Italy) determined which are the main current maize-based cropping systems (MBCSs) in their region and proposed innovative IPM-based systems. The DEXiPM® (DEXi Pest Management) model for arable cropping systems was used to evaluate and compare the economic and environmental sustainability of these systems. The social sustainability was evaluated by adapting indicators of this model to the specificities of maize systems. The assessments showed that all innovative rotated MBCSs proposed in the four regions can have a higher environmental sustainability than and maintain the same economic sustainability as current rotated systems. These cropping systems are thus acceptable for testing under “real” field conditions. Only the innovative continuous maize system proposed in the central-eastern region was both economically and environmentally more sustainable than the current system. All innovative systems had a positive impact on work safety but according to local expert opinion producers and consumers are not ready to implement them or to accept their higher-priced products, with the exception of consumers in the northern region. These results suggest the need for European and regional policies to encourage the adoption of innovative rotated MBCSs that have positive agronomic and environmental impact through IPM implementation. The major constraints that inhibit this adoption were predominantly relating to (1) the lack of access that farmers have to the practical knowledge needed to effectively manage these systems and (2) the insufficient consumer awareness and acceptance of product improvements associated with IPM. To overcome these constraints supportive policy environments, well-functioning knowledge management systems (including good farmer support networks) and effective marketing is required.

Eucalyptus globulus Leaves Incorporated as Green Manure for Weed Control in Maize

The use of eucalyptus leaves for weed control in maize-based cropping systems is proposed. Aqueous extracts of eucalyptus are known to exert phytotoxicity on many weeds and crops, but there is also experimental evidence of the relative tolerance of maize. Based on in vitro dose-response bioassays of leaf aqueous extracts, we conducted greenhouse pot experiments testing incorporated eucalyptus leaves as green manure. The phytotoxic effects were tested on the germination, establishment and growth of maize and some representative accompanying weeds, in comparison to the PRE herbicide metolachlor. Eucalyptus fresh leaves incorporated into the soil as green manure at 1 and 2% w/w reduced the emergence of the dicot weed species redroot pigweed and black nightshade. After one month of incorporation, both doses reduced aerial biomass >94% two monocot weed species (barnyardgrass + large crabgrass) with respect to the eucalyptus-free pots, and around 80% for the small seeded dicots. Although the aerial biomass of maize was reduced by 33%, the final relative yield of maize biomass with respect to the untreated control increased by 37%. On the assessment of the temporal phytotoxic effects, the reduction of aerial biomass in maize could be overcome by adopting a relay-planting of maize after 12 to 15 days from eucalyptus incorporation. Our results constitute evidence that the incorporation of E. globulus residues to soil could be a feasible practice to reduce the reliance on synthetic herbicides in maize-based cropping systems.

Long-term effect of pulses and nutrient management on soil carbon sequestration in Indo-Gangetic plains of India

Venkatesh, M. S., Hazra, K. K., Ghosh, P. K., Praharaj, C. S. and Kumar, N. 2013. Long-term effect of pulses and nutrient management on soil carbon sequestration in Indo-Gangetic plains of India. Can. J. Soil Sci. 93: 127–136. As an important component of crop diversification, pulses/legumes are known to improve soil quality through their unique characteristics of biological N2 fixation, root exudates, leaf litter fall and deep root system. Changes in the soil organic carbon pool due to the inclusion of pulses in an upland maize-based cropping system were evaluated after seven cropping cycles. The results indicate that inclusion of pulses in an upland maize-based cropping system improved the total soil organic carbon content, being greater in surface soil (0–0.2 m) and declining with soil depth. Of the four carbon fractions of total soil organic carbon (C frac 1 –C frac 4 ) measured in the upland maize-based system, the most labile C fraction (C frac 1 ) was dominant. Distribution of the carbon pool varie...

Short-term crop and soil response to C-friendly strategies in two contrasting environments

In southern Europe (Italy), a two-site field experiment with contrasting soil conditions (high clay—SOC-protecting soil near Napoli versus low clay—non-SOC-protecting soil near Torino) was conducted to evaluate the short-term potential of a carbon (C) friendly management to sustain and possibly increase both crop yields and soil organic C (SOC). Compost distribution (COM1, COM2) and minimum tillage (MT) were compared to conventional management (CONV) in a maize-based cropping system. COM1, MT, and CONV each received 130kgNha−1 in compost or urea form. A double dose was applied to COM2 while the plowed control plots (0N) were not fertilized. Fertilizers were applied for three years (from 2006 to 2008); residual soil fertility was assessed during the fourth year (2009).Results suggested that only the SOC protection strategy via MT could be agronomically sustainable in the high clay content soil near Napoli. There, a short-term SOC increase was recorded with either compost or MT application. In fact, in the same soil, compost use depressed both yield and N availability for maize, which we attribute to the reduction of SOM mineralization due to hydrophobic protection by added humified organic matter coupled with soil physical protection. Compost addition increased SOC (55.1% of added C) in the soil near Torino, where high native N availability buffered its low mineralization and allowed high yields. Alternatively, MT showed no effect on short-term C dynamics, probably because the low organic matter protection favored oxidation and mineralization of root-derived C.

Options to reduce N loss from maize in intensive cropping systems in Northern Italy

Maize ( Zea mays, L.) is not only the main crop in the intensively cultivated Po Plain (Northern Italy), but also the one that produces the largest N Surplus. This study is based on experimental data from the Tetto Frati long-term trial (Turin, NW Italy) to demonstrate that the impact on soil and water quality of high-yielding, maize-based cropping systems can be reduced through proper management. Nitrogen use efficiency and loss indicators were calculated and compared among various management options: (i) maize monoculture at high N fertilizer rates for grain production (most widespread management), (ii) entire plant (with straw) harvest, (iii) double-cropping system with a winter crop, (iv) maize–grass ley rotation, and (v) change in fertilizer type. The entire maize plant removal reduced N leaching by 10–20%; however, carbon sequestration was also reduced. A maize–Italian ryegrass double cropping system improved the efficiency of organic fertilizers, and reduced leaching by 25–40% relative to monoculture. A rotation with grass ley reduced N impact only when fertilized with urea, and not when organic fertilizers were used. Urea, slurry, and farmyard manure were equally utilized by the crop; if distributed and incorporated just before sowing, both organic fertilizers built up the soil organic matter content and reduced N leaching by 20–50% with respect to urea. This study has shown that farmers in NW Italy have several opportunities to continue cultivate maize thus accomplishing agri-environmental legislation.

Integration of legume trees in maize-based cropping systems improves rain use efficiency and yield stability under rain-fed agriculture

Water availability is a major constraint to crop production in sub-Saharan Africa (SSA) where agriculture is predominantly rain-fed. This study aimed to investigate the effect of the nitrogen-fixing legume tree Leucaena (Leucaena leucocephala) and inorganic fertilizer on rain use efficiency (RUE), a robust measure of productivity and land degradation, in three long-term (11–12 years) experiments conducted in Zambia and Nigeria. On the two Zambian sites, sole maize (Zea mays) grown continuously (for 11–12 years) with the recommended fertilizer achieved the highest RUE (3.9–4.6 kg ha−1 mm−1) followed by maize intercropped with Leucaena (2.5–3.4 kg ha−1 mm−1). This translated to 192–383% increase in RUE over the control (maize grown without nutrient inputs), which is the de facto resource-poor farmers’ practice. RUE was more stable in fully fertilized sole maize on the first Zambian site and not statistically different from the maize–Leucaena associations on the second site. On the Nigerian site, RUE was higher in maize planted between Leucaena hedgerows supplemented with 50% of the recommended fertilizer (3.9 kg ha−1 mm−1), maize grown between Leucaena hedgerows without fertilizer (3.0 kg ha−1 mm−1) and sole maize receiving the recommended fertilizer (2.8 kg ha−1 mm−1), which translated to increases in RUE of 202%, 139% and 85%, respectively, over the control. RUE was more stable in the maize grown between Leucaena hedgerows than in the fully fertilized maize. On all sites RUE was least stable in the control. Yield stability in the maize–Leucaena association was not significantly different from the fully fertilized maize on the Zambian sites. On the Nigerian site, maize yields were more stable in maize grown in Leucaena hedgerows than in fully fertilized sole maize. Supplementation of maize grown in Leucaena hedgerows with 50% of the recommended fertilizers resulted in greater yield stability. It is concluded that intercropping cereals with legume trees and supplementation with inorganic fertilizer can increase rain use efficiency and yield stability in rain-fed agriculture in SSA.

Crop protection in European maize-based cropping systems: Current practices and recommendations for innovative Integrated Pest Management

Maize-based cropping systems (MBCSs), with different frequency of maize in the crop sequence, are common in European arable systems. Pesticide use differs according to the type of active ingredients and target organisms in different regions. Within the EU Network of Excellence ENDURE, two expert-based surveys were conducted focusing on four European study regions where experts were asked to identify MBCSs in their region, determine the current crop protection practices, propose advanced practices against major pests, weeds and diseases, and evaluate the potential agronomic, environmental, economic and social impact of innovative Integrated Pest Management (IPM) tools on the sustainability of MBCSs. In the northern region (Denmark and The Netherlands), maize is mostly cultivated as non-irrigated continuous silage maize or rotated with grass, while in the central-eastern region the major systems are non-irrigated continuous grain maize (Tolna county, Hungary) or grain maize grown in rotation with winter wheat, oilseed rape and sunflower (Békés county, Hungary). In the south-western (Ebro Valley, Spain) and southern (Po Valley, Italy) regions, continuous and irrigated grain maize, as well as irrigated grain and silage maize/winter wheat rotations are prevalent. Differences in current and proposed advanced crop protection practices for MBCSs were identified between regions due to specific pest, weed and disease problems. The tolerant/resistant non-GM maize cultivars, early detection methods, pest and disease forecasting models, precision/patch spraying using GPS spray maps and the community-based decisions through information sharing were commonly recommended for innovative IPM implementation in all regions. Deviations in the recommendations between regions were mainly caused by differences in the evaluation of economic or social impact of some tools (i.e. innovative mechanical weeding). Applied multi-disciplinary research and farmer incentives to encourage the adoption of innovative IPM strategies are essential for sustainable MBCSs development in Europe. The introduction of innovative tools into IPM strategies can contribute significantly to addressing the EU’s strategic commitment to the sustainable use of pesticides and, consequently, more environmentally sustainable MBCSs.

Sustainability of maize-based cropping systems in rural areas of Zimbabwe: an assessment of the residual soil fertility effects of grain legumes on maize (<I>Zea mays</I> [L.]) under field conditions

The residual soil fertility benefits of the preceding legumes to the following maize crop were demonstrated in the study. Incorporating stover of Bambara nut, cowpea, groundnut dry bean and soyabean gave higher maize yields compared to plots where the stover was removed. Total maize dry matter yield increases of 1.30 tha-¹ to 5.19 ha-¹ were recordedfollowing legume stover incorporation compared to stover removal. Even removal of stover of these same legumes gave significant maize yield increases compared to those from the maize after maize or after fallow plots. The total maize dry matter yield was greater after legumes with stover removed (ranging from 4.41 to 9.91 tha-¹) than after maize (2.16 to 2.26 tha-¹) or one season fallow (1.57 to 1.84 tha-¹). So farmers who keep livestock can still remove legume residues as fodder to supplement grazing in the dry winter period and still benefit from improved maize yields. International Journal of Engineering, Science and Technology, Vol. 2, No. 7, 2010, pp. 141-148

Use of life cycle assessment methodology for determining phytoremediation potentials of maize-based cropping systems in fields with nitrogen fertilizer over-dose

Using the life cycle assessment (LCA) method, we analyzed the effects of different cropping systems (sole maize (CK), maize + soybean (CST) and maize + groundnut (CGT)) on the environment. The comprehensive index of environmental impacts varied in the order, sole maize > maize + groundnut > maize + soybean, with corresponding intercropping values of 0.1295, 0.1229 and 0.0945, respectively. The results showed that intercropping maize with suitable plants (e.g., groundnut and soybean) could reduce the adverse effects of over-application of nitrogen fertilizer on the environment. The study further showed that the LCA method may be a convenient and effective approach for analyzing the environmental impact of fertilizer management in agricultural fields.

Impact of Gliricidia sepium intercropping on soil organic matter fractions in a maize-based cropping system

The gliricidia ( Gliricidia sepium)/maize intercropping system holds promise for increasing productivity in maize-based cropping systems on depleted soils in Southern Africa. The effect of the intercrop on soil properties was investigated to better understand soil processes underlying maize yield response, soil nutrient recapitalization and soil carbon sequestration. Soil organic matter (SOM) fractions, particulate organic matter (POM), POM-carbon, POM-nitrogen, soil nutrient status and underlying soil characteristics were quantified on the 14th year of a gliricidia/maize intercrop establish in 1991 on a Ferric Lixisol in southern Malawi. A factorial design compared the intercrop and a sole maize crop at three rates of added inorganic nitrogen (N) and phosphorus (P). Gliricidia leaf biomass was incorporated into the maize three times per year. Soil was sampled to a 20 cm depth, post-harvest to analyze biophysical and chemical characteristics of soil organic matter, POM, POM-C and POM-N, as well as inorganic N, available P, exchangeable K + and particle size distribution. The gliricidia/maize intercrop had a significant and positive effect on SOM, POM, and SOM fractions: SOM was 12% higher, POM 40%, POM-C 62%, and POM-N 86% higher in the gliricidia intercrop compared to sole maize, indicating nitrogen enrichment of POM. Nitrogen fertilizer was associated with modest increases in POM, 15% in gliricidia and 27% in sole maize. The impacts of these changes were directed mostly at increasing maize yields and increasing storage of soil nutrients over the short term, while decreasing the proportion of organic matter stored over the long term. Both the gliricidia/maize intercrop and increasing soil clay content were associated with significantly increased soil CEC. The gliricidia intercrop maintained CEC in coarse-textured soils over a 14-year time span, indicating a role for legume trees in intensified cropping of coarse-textured soils.

Assessment of Rice and Maize Based Cropping Systems For Rural Livelihood Improvement in Nepal

This paper explores the assessment of rice and maize base cropping system in agro-ecological regions for sustainable rural livelihood development in Nepal. Analysis of 1994-2007 data showed rice-dominated cropping systems in the Plain region, as opposed to maize-dominated cropping systems in the Mountain and the Hill regions. The production increase was achieved mainly through increases in area. The growth in the yield of crops was very minimal in all three regions. During the last fifteen years, the cropping pattern changed slightly from Maize-Wheat to Maize-Paddy in the Mountain region, but no significant change was observed in the other two regions. The current rate of fertilizer application is lower than the recommended rate. Improved access to and availability of agricultural inputs is key to improve the production and yield of major food crops to achieve sustainable rural livelihood in the country. Key words: Agro-ecological-region; Cropping system; Farm income; Rural livelihood; sustainable livelihood The Journal of Agriculture and Environment Vol:10, Jun.2009 page: 67-75

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.

Nitrogen budgets in crop sequences with or without phosphorus-fertilised cowpea in the maize-based cropping systems of semi-arid eastern Africa

Advantages of cowpea were tested in terms of net N-input by cowpea mono- or intercropped with maize in a crop sequence where sparingly soluble P sources were added to the first year crop. The grain yield of maize grown after cowpea monocrop was doubled and the N uptake increased by 60% compared to maize following maize. The N-value of growing cowpea monocropped prior to maize monocrop was equivalent to the application of 50 kg N ha-1 as mineral fertiliser. When maize followed a maize-cowpea intercrop, grain yield was increased by 67%. Around 34% of the N contained in cowpea residues was recovered in the following maize as estimated by 15N. There was however no benefit on the second season maize of applying sparingly soluble P sources to the first season legume. Key words: Cowpea, crop sequences, maize, nitrogen budgets, sparingly soluble phosphorus.

Does the enhanced P acquisition by maize following legumes in a rotation result from improved soil P availability?

Field data have suggested that under P-deficient conditions, legumes supplied with phosphate rock (PR) increase P acquisition by a subsequent maize crop compared to direct application of PR to maize. This study assessed the mechanism of this positive rotational effect in terms of soil P availability using a greenhouse trial with large volume (74 l) containers. The rotation effect was analysed in relation to PR application, previous legume growth and incorporation of the legume residues. Velvet bean ( Mucuna pruriens) and maize were grown in a representative Acrisol from the Nigerian Northern Guinea savannah (NGS). All soils were applied with sufficient urea to exclude N-effects in the rotations. In a first season, velvet bean and maize responded similarly to PR application, and P uptake by both crops increased by 45%. The soil total labile P quantity ( E-value) and P concentration in soil solution ( P solution 31 ) after plant growth were increased by PR-application only in soils previously grown by velvet bean, suggesting enhanced PR solubilisation in the legume-grown soils. In the subsequent season, grain yields and P uptake of a maize crop following velvet bean were twice as large compared to maize following a first maize crop. This residual effect of velvet bean was even significant in treatments without PR-application, although both maize and velvet bean withdrew similar amounts of P during the first season and no differences in soil P availability were observed. Furthermore, legume residue incorporation in soils previously grown by maize did not affect yields or P uptake of the subsequent maize crop, while it significantly increased the E-value and P solution 31 during the first 7 weeks in the second season. As such, the positive rotational effects of velvet bean were larger than predicted by soil P availability measures. Maize yield significantly increased with increasing plant P concentration among all treatments. However, the rotational effect was unrelated to internal P concentration: significantly larger yields were obtained for maize following velvet bean than for maize following maize at identical internal P. This suggested the presence of another growth-limiting which is counteracted by the previous velvet bean growth. In conclusion, our results confirmed that the introduction of a legume supplied with PR into a maize-based cropping system increases yield and P-uptake by a subsequent maize crop, compared to maize following a first maize crop supplied with PR. These stimulations, however, went beyond improved P nutrition. Results strongly suggested that the legume in the rotation system has other positive, possibly soil-microbiological effects which enhance maize growth and production.