Improved fallows or the rotation of fast growing nitrogen-fixing legume species with cereals have been shown to accumulate nitrogen and organic matter, recycle nutrients in the soil and improve soil physical and chemical properties, and increase crop yield compared to traditional fallows. However, the effect of soil nutrients added by fallow species on the incidence of pests, weeds and pathogens in the subsequent crop has not been assessed in southern Africa. In this study, we assessed the relationships between nutrients in the soil after fallows of crotalaria (Crotalaria grahamiana), pigeon pea (Cajanus cajan), sesbania (Sesbania sesban), tephrosia (Tephrosia vogelii), and their mixtures, and the incidence of soil insects, namely, snout beetles (Diaecoderus sp.) and termites, and weeds in eastern Zambia. Rotational fallows of sesbania+crotalaria, sesbania+tephrosia, sesbania+pigeon pea and tephrosia+pigeon pea increased infestation of maize by snout beetles as compared to the natural fallow or unfertilised maize grown continuously in monoculture. The beetles showed aggregated spatial distribution, influenced mainly by the nitrate and total inorganic nitrogen content of the soil. Termite incidence was higher in maize after a natural fallow and pure crotalaria, which had 11 and 7 times as much damage as maize planted after pigeon pea+tephrosia mixture. Total weed biomass in maize grown after a natural fallow was six times higher than in maize planted after pure sesbania fallows. The weed biomass was correlated positively with the potassium content of the top 20 cm soil and negatively with plant litter on the soil surface. It is concluded that organic inputs from pure sesbania, sesbania+pigeon pea, sesbania+tephrosia and tephrosia+pigeon pea reduce infestation by termites and weeds, and give maize grain yield comparable with the recommended rates of inorganic fertilisers. However, these fallows have the potential to increase infestation by snout beetles. This is the first study on the snout beetle in Africa, and we recommend more systematic investigation on its ecology in agroforestry systems.
Tag: crop yield
Legumes for improving maize yields and income in semi-arid Kenya
An experiment was conducted at the research station of the International Centre for Research in Agroforestry (ICRAF) at Machakos, Kenya from November 1989 to February 1996 to evaluate the effect of annual and perennial legumes on soil fertility, cereal yields and economic returns. The study evaluated six cropping systems: (1) continuous sole maize, (2) maize rotated with short-duration legume, cowpea (Vigna unguiculata L. Walp.), (3) maize rotated with long-duration legume, pigeonpea (Cajanus cajan L. Millsp.), (4) maize intercropped with pigeonpea, (5) hedgerow intercropping of maize and a perennial legume, gliricidia (Gliricidia sepium), and (6) continuous sole maize, green-manured with gliricidia prunings produced from an equivalent area outside the cropped field (‘biomass transfer technology’). Maize–cowpea sequential and pigeonpea/maize intercropping systems produced, respectively, 17 and 24% higher maize yields than continuous sole maize, but maize–pigeonpea rotation yielded only marginally better. Hedgerow intercropping did not increase maize yields because increased yields during the few high rainfall seasons did not compensate the yield losses in other seasons due to the competition of hedgerows for water with crop. Green manuring with gliricidia prunings increased maize production by 27%, but this technology was not economical because of high labour costs for production and application of prunings to the crop. The annual grain legume-based cropping systems were 32–49% more profitable than continuous sole maize, making them attractive to small farmers in semi-arid tropics. Both cowpea and pigeonpea were affected by pests and diseases, which indicated the need for integrated pest management for realising the potential benefits of these legume-based systems.
Agroforestry Interactions in Rainfed Agriculture: Can Hedgerow Intercropping Systems Sustain Crop Yield on an Ultisol in Lampung (Indonesia)?
The productivity of rainfed agriculture land developed on Ultisols is limited by physical and chemical constraints. These problems can be solved and consistently high yields obtained only by the development of comprehensive manage-ment systems. In the 1980s, hedgerow inter-cropping was promoted initially for improving soil fertility and sustainability of crop production on nutrient-depleted soils. However the previous enthusiasm for hedgerow intercropping is unsupported by scientific evidence and its labour demand too high. The question remains, is there a window of opportunity where the biophysical principle of hedgerow intercropping is sound Research to compare the long-term performance of crops and trees in hedgerow intercropping and monocluture cropping is needed. This research has been conducted at long-term field experiment station at the BMSF-Project, Lampung, Indone-sia. The experiment site had non-nitrogen-fixing peltophorum (PP), nitrogen-fixing gliricidia (GG) and alternate peltophorum and gliricidia (PG) hedgerow intercropping and maize / groundnut monoculture (C) treatments. We concluded that the net interactions related to soil fertility and competition for growth resources in peltophroum were positive for crop yield in PP and PG but negative for GG. Even so, the PP and PG sys-tems resulted in similar yields as monocropping; however, hedgerow intercropping considerably improved soil fertility attributes.
Ant-mediated ecosystem services and disservices on marketable yield in cocoa agroforestry systems
The impact of complex direct and indirect interactions between multiple functional groups on plants is poorly documented. In tropical agroecosystems, ants interact with crop mutualists and antagonists, however, little is known about effects of dominants ant community properties on the consequence of such cascading interactions which can be measured through final ecosystem service, crop yield. Here, we present a replicated ant fauna manipulation experiment in cocoa agroecosystems, where we used ant exclusion treatments to test the economic importance of the presence of ants, and two additional treatments where we experimentally introduced one of two common dominant ant species which allowed comparing their effects with those of the naturally occurring ant fauna. The proximate aim was to assess the impact of ants Crematogaster sp., Camponotus brutus Auguste-Henri Forel and Oecophylla longinoda Latreille on cacao yield, which is known to depend on several, cascading intermediate ecosystem services (e.g. control of specific pests). Ants provided ecosystem services in term of reduced pest damage caused by Salhbergella singularis Hagh (Hemiptera: Miridae) and Characoma stictigrapta Hmps (Lepidoptera: Noctuidae) but also disservices such as increased pathogen disease caused by Phyphthora megakarya Brasier and Griffin dissemination and indirectly enhanced damage of other pest species. Yields were highest in non-manipulated and species-rich ant communities, whereas ant exclusion and communities dominated by a single species decreased yield by more than 30%. Associated ant communities between dominant and non-dominant species resulted in the same yields as in non-manipulated controls. Dominant ant communities maximized the control of a particular pest species, but not cacao yield. We show a positive relationship between ant species rich communities and financial performance and we postulate that complex agroecosystems can offer competitive business opportunities for small-scale farmers, while contributing to biodiversity conservation. However, more interdisciplinary studies are needed to quantify financial and biodiversity performance opportunities to allow up-scaling of these findings. © 2017 Elsevier B.V.
The effect of cattle grazing on soil physical and chemical properties in a silvopastoral system in the Peruvian Amazon
In a six-year-old peach palm (Bactris gasipaes) plantation, centrosema (Centrosema macrocarpum), a leguminous forage plant, was established as a cover crop which was eventually grazed. This experiment was designed to monitor probable changes in soil physical and chemical properties and measure peach palm fruit production and live-weight gain of cattle grazing this silvopastoral system. The experiment was installed on land that was previously cleared by a D7 bulldozer having a straight blade that mixed the thin layer of topsoil with the acid subsoil (20–40 cm) and severely compacted the soil. The results demonstrated that the centrosema cover crop reduced soil bulk density, increased water infiltration rates and reduced mechanical resistance. In general soil physical properties were improved with the use of Centrosema as forage and cover crop. Soil acidity and aluminum saturation decreased considerably, while potassium concentrations increased. Calcium and magnesium concentrations decreased over time as these minerals were stored in the pasture biomass, translocated to fresh peach palm fruits and/or exported to animals. A strong competition for nutrients was observed between the peach palm plants and Centrosema. The low production of peach palm fruits was in response to mechanized land clearing during initial establishment of the plantation, and also probably due to deficits of N, P, K, Ca and Mg in the soil instead of being a consequence to the presence of cattle. The average increase in live-weight gains of the cattle was at a rate of 445 g/animal/day during the four-years of the study. Such an increase is substantially greater than those registered in the area under traditional grazing systems used in the region.
Productivity of intensified crop-fallow rotations in the Trenbath model
Management of crop—fallow rotations should strike a balance between exploitation, during cropping, and restoration of soil fertility during the fallow period. The ‘Trenbath’ model describes build-up of soil fertility during a fallow period by two parameters (a maximum level and a half-recovery time) and decline during cropping as a simple proportion. The model can be used to predict potential crop production for a large number of management options consisting of length of cropping period and duration of fallow. In solving the equations, the model can be restricted to ‘sustainable’ systems, where fallow length is sufficient to restore soil fertility to its value at the start of the previous cropping period. The model outcome suggests that the highest yields per unit of land can be obtained by starting a new cropping period after soil fertility has recovered to 50–60% of its maximum value. This prediction is virtually independent of the growth rate of the fallow vegetation. The nature of the fallow vegetation (natural regrowth, planted trees, or cover crops) mainly influences the crop yield by modifying the required duration of fallow periods. Intensification of land use by shortening fallow periods will initially increase returns per unit land at the likely costs of returns per unit labor. When fallows no longer restore soil fertility to 50% of the maximum, overall productivity will decline both per unit land and per unit labor, unless external inputs replace the soil fertility restoring functions of a fallow
Market analysis of selected agroforestry products in the Vision for Change Project intervention zone, Côte d’Ivoire
Cocoa yield per hectare in Côte d`Ivoire is among the lowest in the world, ranging from 0.2 to 0.5 tons/ha per year. This figure continues to decline each season due to decreased soil fertility, increased disease pressure, the aging of cocoa orchards, and low use of inputs (Assiri et al. 2012, FLA 2012). Yields could be increased if farmers were able to apply fertilizer in recommended quantities, replant old orchards (especially with improved cocoa varieties), and control diseases with f ungicides and other methods. However, for various reasons such as lack of financial means, low levels of technical training and reduced incentives to invest in cocoa because of low prices, the majority of Ivorian cocoa farmers are not implementing these so il and crop improvement management methods (Nkamleau et al. 2007, FLA 2012). In view of this , Mars I ncorporated , in col labo r ation with the Ivorian Government , embarked on the Vision for Change (V4C) project as a means of addressing the problem of low prod uctivity of cocoa. This project is being implemented by the World Agroforestry Centre (ICRAF) . The initiative is currently setting up a network of Cocoa Development Centre s (CDCs) throughout the region of Soubré, the most productive cocoa region in Côte d` Ivoire, and conducting on – farm research into different cocoa cultivars, rehabilitation of old orchards by grafting, and the effect of fertilizer application and other management practices ( ICRAF 2012 ) . In future the project will enter the extension stage, and the best methods of increasing cocoa yields, plus affordable inputs to accomplish them, will be made accessible to farmers throughout the region. This initiative is designed on the same model as a successful project initiated in Indonesia by Mars in 20 03, which increased cocoa yields from 0.5 to 2.5 tons/ha per year, on average (Pye – Smith 2011). Initial studies of the effects of rehabilitation methods in field trials in Côte d’Ivoire are encouraging, showing an 83% average increase in yields and an aver age profitability rate of 377% (Assiri et al. 2012).
Crop productivity and tree growth in intercropped agroforestry systems in semi-arid and sub-humid regions of Ethiopia
Agroforestry has been practiced traditionally by smallholder farmers in tropical countries, including Ethiopia. However, scientific information on tree-crop interactions isn’t widely available. Long-term agroforestry field experiments were conducted, in sub-humid and semi-arid regions of Ethiopia, to explore the impacts of intercropping on crop yield and tree growth. The treatments in the sub-humid areas were; tree alone (Cordia, Grevillea, Croton, and Acacia abyssinica), (2) crop alone, teff (Eragrostis tef), maize (Zea mays) and finger millet (Eleusine coracana), (3) tree + crop, (4) mix of four tree species and (5) mix of tree species + crops. The treatments in the semi-arid area included (1) tree + crop (teff with Faidherbia, Moringa, Acacia nilotica and Cordia, (2) crop alone, and (3) mix of trees + crops. The species choice was determined by suitability to local contexts and from farmer prioritisation participatory design workshops. Crop yield, tree height, and diameter were measured from each treatment. Crop yields under tree + crop treatments were not significantly different (α = 0.05) from crop yield in the sole crop treatments (in both areas), except crop yields under Acacia abyssinia, which had the lowest crop yields compared to the rest of the treatments in the sub-humid areas. In the semi-arid area, teff yield under Faidherbia in 2019, has increased by 64%, compared to the yield in 2017. The best growth performance was attained by Grevillea and Cordia in the sub-humid areas, whereas Acacia nilotica performed well in the semi-arid areas. These results suggest that the selection of appropriate tree and crop species can enhances crop and tree production in agroforestry systems of Ethiopia.
Phosphorus acquisition by wheat from organic and inorganic sources labelled with 32P and 33P radioisotopes
Investment in soil phosphorus (P) capital in the tropics is often constrained by poor availability of mineral fertiliser to small-scale farmers. Consequently, new sustainable agricultural cropping strategies are required to maintain fertility and maximise crop yields. The co-application of Tithonia diversifolia (Tithonia) green manure and mineral fertiliser (KH2PO4) together (integrated nutrient management) in comparison to the addition of one or the other alone has been hypothesized to promote crop P uptake. The aim of this study was to critically evaluate the benefits of integrated nutrient management practices in laboratory experiments. Wheat was grown as a test crop in microcosms to which either 32P-labelled mineral fertiliser or 33P-labelled Tithonia was added either singly or in combination. Exclusion meshes were used to determine the role of arbuscular mycorrhizal (AM) fungi in P uptake from the different P sources. The rate of uptake of both 32P and 33P by mycorrhizas was similar, and the rate of mycorrhizal P capture was comparable to that of roots. Generally, there was little difference in wheat P acquisition under integrated nutrient management treatments in comparison to P acquisition from 32P-mineral fertiliser or the addition of 33P-Tithonia alone. Overall, Tithonia residues were not very effective in supplying P to wheat over a short time evaluation period, suggesting that mineral fertilisers will still be required to satisfy crop demand.