Cereal Intercropping Research Articles

Can positive interactions between cultivated species help to sustain modern agriculture?

The importance of positive interactions between species within natural ecosystems and species associated with traditional agriculture is well recognized. However, modern agriculture generally depends on monocultures, where positive interactions between cultivated species (ie in which the presence of one species facilitates the survival, growth, or reproduction of other species) are largely ignored. Here, we review recent studies focused on the positive interactions between cultivated species, consider how three traditional agricultural systems (legume–cereal intercropping, rice–fish co‐culture, and agroforestry) have benefited from such interactions, and examine how these benefits are affected by climate, planting patterns, and field management. Finally, we propose a framework to illustrate how these interactions may improve modern agriculture through: the selection of species–species partnerships; the development of specialized field machinery (in each case); field structure and configuration; field management; and farmer and societal acceptance.

Soybean–Cereal Intercropping Systems as Influenced by Nitrogen Nutrition

Little is known how to optimize N supply of cereal components in an intercropping system that considers biological nitrogen fixation (BNF) from soybean [Glycine max (L.) Merr.]. A 2‐yr field experiment was conducted to study the compatibility of soybean–cereals intercropping as influenced by varying N levels to intercropped cereals as per recommended dose of nitrogen (RDN) for respective cereals. Soybean was grown as the main crop with 100% plant population and cereals were intercropped at 2:1 ratio in additive series (without sacrificing main crop population). While the yield of intercropped maize (Zea mays L.) significantly increased up to 100% RDN, the yield of intercropped sorghum [Sorghum bicolor (L.) Moench.] and pearl millet [Pennisetum typhoides (Burm.f.) Stapf & C.E. Hubb.] increased only up to 75 and 50% RDN, respectively. The soybean yield reduced by 33.6, 37.9 and 58.3% due to intercropping with maize, sorghum and pearl millet, respectively. The soybean equivalent yield, net return, benefit cost ratio and monetary advantage index were maximum in soybean+maize intercropping provided with 100% RDN to maize. Land equivalent ratio, relative crowding coefficient and intercropping advantage were the greatest with soybean+maize intercropping proving that there was an advantage of intercropping with maize. The aggressivity and competitive ratio were higher for pearl millet and sorghum as compared to maize indicating that pearl millet and sorghum were more competitive to soybean than maize. The study indicated the possibility to reduce N fertilizer requirement by 25 and 50% in case of sorghum and pearl millet as intercrop with soybean, respectively.

Refining Dryland Farming Systems as a Means of Enhancing Agrodiversity and Food Security in Eastern Kenya: A review.

Drylands which cover one third of the earth’s land surface and almost 80% of Kenya’s land surface are being used to grow dryland crops such as maize, beans, sorghum, millets and livestock. Studies show that refined farming systems can be used in enhancing ecosystem sustainability, through the promotion of species and crop diversity. For example, cropping patterns involving intercropping legumes and cereals have demonstrated varying success in maintenance of crop diversity in the Kenyan drylands showing land equivalent ratios (LER) > 1.0, although such benefits are often lost during low rainfall seasons. Research show that some genotypes can be used to reduce soil erosion, enhance nutrient availability, soil moisture retention, microbial earthworm activities and land use efficiency. Thus critical examination of farming systems for dryland areas suggests that long term multiple effects of the ecosystem, rather than the short term benefits not only increases yields but sustains the life of ecosystems. In this reveiw we submit that monocropping systems should be modified to include varieties that are suitable for different plots in the same site to enhance efficient utilization of underground diversity. In developing farming systems modelling approaches utilizing plant genotypic and epigenetic variations, ecological, edaphic and microbial cycles should be evaluated for dryland ecosystems.

Suppression of Annual Weeds in Pea and Cereal Intercrops

Experiments were constructed to investigate effects of pea [Pisum sativum L. (Partim)] and spring cereal intercrops on annual weed suppression and grain yield in an organic farming system. Pea, spring wheat (Triticum aestivum L. emend. Fiori et Paol.), barley (Hordeum vulgare L.), oat (Avena sativa L.), and triticale (× Triticosecale Wittm.) were sown as sole crops and as intercrops at a 50:50 proportion of grain legume and spring cereal seeds relative to sole crop rates. The density of wheat, oat, and triticale sole crops was significantly higher compared with intercrops with pea. All investigated intercrops were significantly denser than the sole pea crop. Low height was observed in pea and barley sole crops and intercrops. Mostly weed number and mass were not significantly different between sole cereal and intercrops. Crop density was more effected by suppression than weed height. Where crops were sparser, increases in weed density and mass corresponded to a significant decline in grain yield. In the pea–cereal intercrop, where pea accounted for 20.3 to 35.2% of the total plant number, cereals exhibited the greatest weed suppression ability, productive stem number and height being the main factors responsible for this.

Meta‐Analysis of the Effect of Nitrogen Fertilization on Annual Cereal–Legume Intercrop Production

Numerous studies have been performed to study the effect of N fertilization on cereal–legume intercrops, and their results are sometimes conflicting. Our objective was to do a meta‐analysis on cereal–legume intercrops testing the effects of N fertilization on land equivalent ration (LER; partial and total LER), yield ratio, and proportion of legume in the mixture of crop grains. This analysis was based on 17 published studies reporting the results of experiments performed in 15 countries on six species of cereals and 10 species of legumes. Experiments were generally based on replacement (50–50, i.e., in the intercrop, each species is sown at half the sowing rate used for the sole crop) or full substitutive (100–100, i.e., the sowing rate for each crop in the intercrop is identical to that for sole crops) designs. Nitrogen fertilization rates ranged from 0 to 180 kg N ha−1. The effect of N fertilization and its inter‐study variability were analyzed with mixed‐effect statistical models, including study as a random effect. Results showed that N fertilization had non‐significant effects on average LER and average yield ratio but that the inter‐study variability of these effects was large. Nitrogen fertilization was found to significantly decrease the grain proportion of the legume in the mixture and the partial LER of the legume in studies based on C3 cereal intercrops. The database used for the meta‐analysis is freely available (http://www6.versailles‐grignon.inra.fr/agronomie/Meta‐analysis‐in‐agronomy/Datasets/Dataset‐Intercrop).

Potential of legume-cereal intercropping for increasing yields and yield stability for self-sufficiency with animal fodder in organic farming

Intercropping of grain legumes and cereals is a promising theme in organic farming for its potential for increasing and stabilizing yields, reducing weed pressure and sustaining plant health. On animal husbandry farms, pea-cereal mixtures may be an interesting crop harvested for green fodder as well as for feed concentrates. Increasing self-sufficiency with fodder is in agreement with the principles of organic agriculture, and it reduces the risks related to the import of soy protein that may be admixed with GM soya. In 2008–2011, plot trials (PT) with intercropped peas and spring cereals (wheat, barley) were conducted. Varieties and pea-cereal combinations were examined to find suitable varieties for intercropping, and the best pea to cereal ratio in the seed intercrop (pea to cereal ratios 80:20, 60:40, 40:60, 20:80). Results show that intercropping peas and spring cereals may be advantageous compared to monocultures. Pea-cereal intercrops produce high yields of green matter and concentrates especially when intercropped at the pea to cereal ratio of 60:40 and 40:60. In 2009, on five certified organic farms, controlled field trials (FT) were conducted with field pea (leaf type), spring barley and spring wheat in monocultures and intercrops (pea to cereal ratio 60:40). Forage yields were evaluated at pea growth phases BBCH-scale 79 and 83. Fresh yields of monocultures and intercrops were evaluated at grain harvest.

Influence of Small Cereal Intercropping and Additive Series of Seed Proportion on the Yield and Yield Component of Lupine (Lupinus Spp.) in North Western Ethiopia

Small cereals as a main crop and lupine as a minor crop are food crops often traditionally grown in association in North Western Ethiopia. The experiment was conducted on intercropping of lupine (Lupinus albus L.) with wheat (Triticum aestivum), barley (Hordeum vulgar) and finger millet (Eleusine coracana) in 2009 at Adet Agricultural research station. The treatments were sole wheat at a seed rate of 175 kg/ ha, sole barley at a seed rate of 125 kg/ ha, sole finger millet at a seed rate of 30 kg/ ha, sole lupine at a seed rate of 90 kg/ ha, and an additive series of 25, 50 and 75 % of the sole lupine seed rate combined with the full cereal seed rate to determine the effect of small cereal intercropping in additive series on the yield and yield component of lupine. The experimental design was a completely randomized block with nine intercropping and four sole cropping systems in three replications. Lupine was planted in rows after establishment of main crops. SAS software’s were used to compute the analysis of variance. Maximum lupine seed proportion was superior to the lowest when intercropped with wheat and finger millet. The lowest population density resulted in reduced agronomic attributes of lupine. Intercropping higher proportion of lupine with wheat and finger millet did help much in increasing grain yield and biomass yield of lupine without affecting cereal crop yield. However, nearly complete dominance of barley over lupine at all seeding ratios leads to absolute reduction in grain yield. The lupine-finger millet mixture at the 50:100 and 75:100 seeding ratio and lupine-wheat mixture at the 75:100 seeding ratio had a higher yield advantage of intercropping for exploiting the resources of the environment compared with the other intercropping systems.

Cumulative effects and economic benefits of intercropping maize with food legumes on Striga hermonthica infestation

The parasitic weed Striga hermonthica, commonly known as striga, is a major biotic constraint to maize production in sub-Saharan Africa (SSA) where it causes serious food insecurity and poverty in smallholder farming communities. We previously discovered an effective control method for it involving intercropping cereals with fodder legumes in the genus Desmodium, commonly known as desmodium. The objectives of the current study were to evaluate cumulative effects of intercropping maize with the commonly grown food legumes on striga infestation, and to establish any economic benefits of the same. Treatments comprised maize plots planted in monocrop stands or intercropped with five different food legume species or desmodium. Intercropping maize with desmodium gave the most consistent and significant suppression of striga. Out of the food legume intercrops, only crotalaria, groundnut and greengram intercrops had significantly lower striga counts and only in some of the cropping seasons. Grain yields were consistently and significantly higher with desmodium intercrop, although they were also increased with food legume intercrops compared to maize monocrop, thus confirming superiority of intercropping with legumes over maize monocrop. Although production costs in terms of total labor and variable costs were significantly higher for the intercrops than for the maize monocrop, total revenue and net benefits were significantly higher in the former, especially for desmodium. The desmodium intercrop gave the highest economic benefits followed by crotalaria and greengram intercrops. These results confirmed the effectiveness of desmodium in suppressing striga and improving yields and economic returns to smallholder farmers. They also showed that it is profitable to invest in food legume intercrop systems, especially the crotalaria and greengram systems, and indicate that intensifying maize cropping systems through integration of these food legumes in combination with other approaches can contribute to an integrated management of striga and provide a more sustainable and profitable productive system to smallholder farmers.

Effects of mulching, N-fertilization and intercropping with Desmodium uncinatum on Striga hermonthica infestation in maize

The parasitic weed Striga hermonthica is a major constraint to maize production in sub-Saharan Africa and causes serious food insecurity. We discovered serendipitously an effective control method for the weed that involves intercropping cereals with the fodder legume, silverleaf desmodium, Desmodium uncinatum (Jacq.) DC., through mechanisms that involve soil shading and nitrogen fixation. In the current study we investigated long-term effects of inorganic nitrogen (N), mulching and D. uncinatum, singly and in combinations, on S. hermonthica infestation, maize plant growth and grain yields. Treatments comprised sole maize with and without 120 kg N/ha; sole maize plots covered with maize straw (i.e. mulching), with and without N; and maize–D. uncinatum intercrop, with and without N. Intercropping maize with D. uncinatum gave the most significant suppression of S. hermonthica, with addition of N only minimally enhancing its effect. Similarly, mulching significantly suppressed S. hermonthica, although to a much less extent. Application of N both to sole maize and mulched plots reduced seasonal S. hermonthica infestations but the effect was largely insignificant. The effect of D. uncinatum was again notable as it dramatically increased maize plant height and grain yields, with the addition of N only minimally improving both effects. Application of N and mulch, singly and in combination, to the sole maize crop generally enhanced plant height and grain yields, although to a less extent, with the effect of N on grain yields being statistically insignificant during most of the cropping seasons. These results confirm the efficacy of D. uncinatum in S. hermonthica suppression leading to better growth and yields of maize. The effects of N application, mulching and a combination of both treatments in S. hermonthica control in maize were also observed, although these effects were much weaker. The results and their implications are discussed in the context of smallholder cropping systems in the region.

Allelopathy as protectant, defence and growth stimulants in legume cereal mixed culture systems

In Africa, yield loss and low income to farmers is exacerbated by pests and notorious weeds manifested in different cropping systems. The fact that crop species may be allelopathic to common weeds, pathogens and insect pests has attracted considerable attention as an alternative strategy for weed and pest management in small-scale and low-input mixed culture systems. The use of crop plants with greater allelochemical production could limit the need for agrochemicals and conventional herbicides for plant protection and defence. As a result, plant growth and grain yield will be increased, leading to greater profit margins for farmers. This review discusses the possible role(s) of allelopathy as a key player in protection, defence and growth stimulants in legume cereal intercropping systems.

Economic evaluation and applications of the policy analysis matrix of sole and intercropping of leguminous and cereals in Shirvan city, Iran

Economic evaluation and applications of the policy analysis matrix of sole and intercropping of leguminous and cereals in Shirvan city, Iran

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.

Dry matter yield, nitrogen content, and competition in pea–cereal intercropping systems

Intercrops of pea ( Pisum arvense L.), a popular legume used in intercropping systems with winter cereals for forage and silage production, with wheat ( Triticum aestivum L.), rye ( Secale cereale L.), and triticale (× Triticosecale Wittmack) in two seeding ratios (60:40 and 80:20) were compared with monocrops of pea and cereals for two growing seasons. Growth rate, dry matter yield, and N uptake were determined in each intercropping system. Furthermore, several indices were used to evaluate the intercropping systems and analyze the competition and the interrelationships between mixture components. Growth rate of cereals was lower in the mixtures than in the monocrops. Dry matter yield was higher in triticale monocrop, followed by its two intercrops, and the pea–wheat 80:20 intercrop. Moreover, triticale monocrop, pea–triticale intercrops, and pea–wheat 80:20 intercrop showed the highest crude protein yield and N uptake. The land equivalent ratio (LER), relative crowding coefficient (K), actual yield loss (AYL), and system productivity index (SPI) values were greater for the pea–triticale mixtures and the pea–wheat and pea–rye mixtures (80:20), indicating an advantage of intercropping. In most intercrops, the values of partial K, AYL, aggressivity, and competitive ratio (CR) indicated that the cereal was more competitive than pea. The highest values of monetary advantage index (MAI) and intercropping advantage (IA) were recorded for the pea–triticale and the pea–wheat mixtures (80:20). Overall, pea–triticale and pea–wheat mixtures (80:20) were more productive and produced better forage quality than the other mixtures and thus could be adopted by the farmers as alternative options for forage production.

Durum wheat–faba bean temporary intercropping: Effects on nitrogen supply and wheat quality

Intercropping cereals and grain legumes is a common practice because of the advantages in N use, in pest and volunteer plant smothering, but when the grains need to be separated, there are several technical difficulties. These problems may be overcome by adopting a particular form of intercropping (termed “temporary intercropping”) where the coexistence of the crops is limited to a portion of their life cycles. In a cereal–legume temporary row-intercropping, the legume component is ploughed into the soil before cereal shooting; thus the legume is used with a mere fertility purpose in order to improve N availability for the cereal component. The presence of such a positive effect, already confirmed in permanent intercropping, needs to be verified in temporary intercropping systems. In an organic farming system, a field experiment was carried out in two consecutive years (2005 and 2006) to evaluate the technical feasibility of a temporary intercropping between three varieties of durum wheat ( Triticum durum Desf.) and faba bean ( Vicia faba L. var. minor Beck.) and to test the effects on interspecific competition for light, N availability, cereal grain yield and quality. The species were temporarily intercropped following an additive design, and there was no fertilisation or crop protection. The N incorporated into the soil by the faba bean biomass was rather stable across years. The competitive effect of the legume reduced the biomass accumulation of the intercropped wheat, but the cereal N status was considerably improved. After the faba bean incorporation into the soil, the marked asymmetry of the temporary intercropped wheat (i.e. large inter-row space coupled with high plant density in the row) affected the radiation balance, nevertheless the yield was positively affected and the wheat grain protein content was increased to an excellent (from 12.0 to 13.9% in 2005) or a good (from 10.2 to 11.5% in 2006) level. Temporary intercropping was shown to be excellent method to improve the quality of organic durum wheat in the Mediterranean environmental conditions.

Intercropping of Cereals and Legumes for Forage Production

Cereals are high important in feeding ruminant animals for their high dry matter production and low cost. However, cereals forage is poor in protein content which shows their low quality and nutritive value. Regarding to high feed costs of protein supplementations, legumes can be used in livestock nutrition for their high protein content and, thus, providing cost saving. Since legumes have low dry matter yield, acceptable forage yield and quality can obtained from intercropping of cereals and legumes compared with their sole crops. In this paper, forage quality indicators and different factors affecting forage quality are discussed. Forage production and quality of different cereals-legumes intercropping are also reviewed, where; different legumes had different effect on forage quality when intercropped with specific cereal. Regarding to forage quality and quantity, different cereals also led to different production of forage. A number of factors which must be noticified in selecting cereal-legume intercropping compositions, especially for forage production, were considered.

COMPETITIVE ABILITY OF WINTER CEREAL–COMMON VETCH INTERCROPS AGAINST STERILE OAT

SUMMARYIntercropping cereals with legumes for forage or food production is extensively used as a cropping practice in many parts of the world. A 2-year field study was conducted using common vetch (Vicia sativa), winter wheat (Triticum aestivum), triticale (× Triticosecale), barley (Hordeum vulgare) and oat (Avena sativa) sole crops as well as common vetch intercrops with each of these cereals in a 35:65 cereal:common vetch ratio based on seed numbers, to determine their ability to compete with sterile oat (Avena sterilis spp. sterilis). At nine weeks after planting, fewer sterile oat plants emerged in common vetch sole crop than in cereal sole crops. Intercropping of cereals with common vetch generally did not affect sterile oat stem number and biomass compared with cereal sole crops. At harvest, cereal sole crops provided greater total dry biomass (DB) than the common vetch sole crop. However, triticale and oat produced more DB than winter wheat and barley. In most cases intercropping reduced total DB compared with cereal sole crops. The results of this study indicated that intercropping of the four winter cereals with common vetch did not provide any significant competitive advantage against sterile oat. However, common vetch sole crop showed the greatest suppressive ability against sterile oat among the sole crops or intercrops studied.

Yield potential and land-use efficiency of wheat and faba bean mixed intercropping

In Ethiopia, food production for a rapidly growing population from a continually shrinking farm size is a prime developmental challenge. Rising input costs, decline in soil quality, and buildup of insect pests, diseases and weeds have threatened the ecological and economic sustainability of crop production. To address those issues, intercropping of cereals with pulse crops could increase total grain production, provide diversity of products, stabilize yield over seasons, reduce economic and environmental risks common in monoculture systems, and thereby enhance sustainability. Here, mixed intercropping of wheat (Triticum aestivum L.) with faba bean (Vicia faba L.) was compared with sole culture of each species in 2002 and 2003 at Holetta Agricultural Research Center, in the central highlands of Ethiopia. The treatments were sole wheat at a seed rate of 175 kg ha −1 , sole faba bean at a seed rate of 200 kg ha −1 , and an additive series of 12.5, 25, 37.5, 50 and 62.5% of the sole faba bean seed rate mixed with the full sole wheat seed rate. Our results showed that mixed intercropping increased the land equivalent ratio by +3% to +22% over sole cropping. Increasing the faba bean seed rate in the mixture from 12.5 to 62.5% reduced wheat grain yield from 3601 kg ha −1 to 3039 kg ha −1 but increased faba bean grain yield from 141 kg ha −1 to 667 kg ha −1 . Sole culture grain yield exceeded mixed culture grain yield by + 5t o+25% for wheat and by +172 to +1190% for faba bean. Nonetheless, we obtained the highest total grain yield of 4031 kg ha −1 , gross monetary value of US$ 823, system productivity index of 4629 and crowding coefficient of 4.70 when wheat at its full seed rate was intercropped with faba bean at a rate of 37.5%. On average, weed biomass was reduced from 40.4 g m −2 in sole wheat to 31.1 g m −2 in mixed culture and the chocolate spot disease score was reduced from 5.1 in sole faba bean to 3.4 in mixed culture. In conclusion, intercropping of wheat with faba bean may increase total yield and revenue, reduce weed and disease pressure, increase land-use efficiency, and thereby enhance sustainability of crop production in Ethiopian highlands. aggressivity / crowding coefficient / faba bean / land-use efficiency / intercropping / wheat

Grain legume–cereal intercropping: The practical application of diversity, competition and facilitation in arable and organic cropping systems

AbstractIntercropping is the simultaneous cultivation of more than one crop species on the same piece of land and is regarded as the practical application of basic ecological principles such as diversity, competition and facilitation. Field experiments were carried out on a sandy loam soil and a sandy soil in Denmark over three consecutive cropping seasons including dual grain legume (pea, faba bean and lupin)–barley intercropping as compared to the respective sole crops (SC). Yield stability of intercrops (IC) was not greater than that of grain legume SC, with the exception of the IC containing faba bean. Faba bean and lupin had lower yield stability than pea and fertilized barley. However, the different IC used environmental resources for plant growth up to 50% (LER=0.91–1.51) more effectively as compared to the respective SC, but with considerable variation over location, years and crops. The SC performance supported the interspecific interactions within the IC stand. On the sandy loam 13% greater grain yield of pea cv. Agadir (520 g m−2) was observed as compared to cv. Bohatyr. Faba bean and lupin yielded similarly (340 g m−2) in the sandy loam soil, with decreasing yields on the sandy soil (320–270 g m−2). Nitrogen fixation was very constant in grain legume SC over species and location, varying from 13.2 to 15.8 g N m−2, being lowest in peas and highest in faba bean and lupin. The intercropped grain legumes increased the proportion of plant N derived from N2-fixation by on average 10–15% compared to the corresponding SC. However, especially lupin was suppressed when intercropping, with a reduced N2-fixation from 15 to 5–6 g N m−2. The IC were particularly effective at suppressing weeds, capturing a greater share of available resources than SC. Weed infestation in the different crops was comparable; however, it tended to be the highest in sole cropped faba bean, lupin and unfertilized barley, where the application of urea to barley reduced the weed infestation by around 50%. Reduction in disease was observed in all IC systems compared to the corresponding SC, with a general disease reduction in the range of 20–40%. For one disease in particular (brown spot on lupin) disease reduction was almost 80% in the IC. Intercropping practices offer many advantages but improved understanding of the ecological mechanisms associated with planned spatial diversity, including additional benefits with associated diversity, is needed to enhance the benefits achieved.

A critical analysis of challenges and opportunities for soil fertility restoration in Sudano-Sahelian West Africa

Since the 1970s, research throughout West Africa showed that low soil organic matter and limited availability of plant nutrients, in particular phosphorus and nitrogen, are major bottlenecks to agricultural productivity, which is further hampered by substantial topsoil losses through wind and water erosion. A few widely recognized publications pointing to massive nutrient mining of the existing crop–livestock production systems triggered numerous studies on a wide array of management strategies and policies suited to improve soil fertility. Throughout Sudano-Sahelian West Africa, the application of crop residue mulch, animal manure, rockphosphates and soluble mineral fertilizers have been shown to enhance crop yields, whereby yield increases varied with the agro-ecological setting and the rates of amendments applied. In more humid areas of Western Africa, the intercropping of cereals with herbaceous or ligneous leguminous species, the installation of fodder banks for increased livestock and manure production, and composting of organic material also proved beneficial to crop production. However, there is evidence that the low adoption of improved management strategies and the lack of long-term investments in soil fertility can be ascribed to low product prices for agricultural commodities, immediate cash needs, risk aversion and labour shortage of small-scale farmers across the region. The wealth of knowledge gathered during several decades of on-station and on-farm experimentation calls for an integration of these data into a database to serve as input variables for models geared towards ex-ante assessment of the suitability of technologies and policies at the scale of farms, communities and regions. Several modelling approaches exist that can be exploited in this sense. Yet, they have to be improved in their ability to account for agro-ecological and socio-economic differences at various geographical scales and for residual effects of management options, thereby allowing scenario analysis and guiding further fundamental and participatory research, extension and political counselling.

Competition indices of common vetch and cereal intercrops in two seeding ratio

A 2-year field study was conducted using common vetch ( Vicia sativa L.), wheat ( Triticum aestivum L.), triticale (x Triticosecale Wittmack), barley ( Hordeum vulgare L.), and oat ( Avena sativa L.) pure stands as well as two common vetch–cereal mixtures for silage with each of the above four cereals in two seeding ratios (i.e., vetch:cereal 55:45 and 65:35, based on seed numbers) to determine the competition among the different species and the economics of each intercropping system. Intercropping systems were assessed on the basis of several existing intercropping indices such as land equivalent ratio (LER), relative crowding coefficient (RCC or K), aggressivity ( A), competitive ratio (CR), actual yield loss (AYL), monetary advantage index (MAI), and intercropping advantage (IA). The LER and K values were greater for the common vetch–wheat (55:45) and the common vetch–oat (65:35) mixtures indicating that in these systems, there was an advantage of intercropping for exploiting the resources of the environment. A similar trend to that of LER and K was also observed for AYL. The aggressivity, CR and partial AYL values were greater for barley and oat than for wheat and triticale, whereas the corresponding values for common vetch were lower in mixtures with barley and oat than in mixtures with wheat and triticale. These findings indicate that barley and oat were more competitive partners than wheat and triticale as common vetch was affected more in mixtures with these two crops. The highest MAI and IA values were recorded for the common vetch–wheat (55:45) and the common vetch–oat (65:35) mixtures indicating that these intercropping systems were the most profitable.