Leguminous cover crops can be used in the humid tropics to increase the production of subsequent food crops, through effects on nitrogen availability in the soil, suppression of weeds and/or changes in soil physical conditions. Nodulation, total root and shoot mass and depth of root development are important characteristics of cover crops. Root development of several cover crops is described here for two sites with acid soils, in S.E. Nigeria and S. Sumatera, Indonesia. Short-lived annual species have a higher shoot: root ratio than perennial species. Mucuna pruriens utilis had the most shallow root system, but good nudulation and, through its fast growth, it was best insuppressing weeds (in a 4-month period). Mucuna and Crotalaria juncea gave the best effect on a subsequent maize crop in an experiment on a dark grey alluvial soil in Malang, E. Java, Indonesia. Apart from being a source of N, the cover crops also had a positive effect on subsequent maize growth by increasing water storage in the soil and by improving root development of maize.
Tag: legumes
The utility of process-based models for simulating N2O emissions from soils: A case study based on Costa Rican coffee plantations
Soil moisture and gaseous N-flux (N2O, N-2) dynamics in Costa Rican coffee plantations were successively simulated using a mechanistic model (PASTIS) and two process-based models (NGAS and NOE). Two fertilized (250 kg N ha(-1) y(-1)) coffee plantations were considered, namely a monoculture and a system shaded by the N-2 fixing legume species Inga densiflora. In situ N2O fluxes were previously measured in these plantations. NGAS and NOE used specific microbial activities for the soils. To parameterize NGAS, we estimated N mineralization via in situ incubations and the contribution of heterotrophic soil respiration to total soil respiration. Potential denitrification rates and the proportion of denitrified N emitted as N2O were measured in the laboratory to define the values of NOE parameters, as well as nitrification rates and related N2O production rates for parameterizing both models. Soil moisture and both NGAS and NOE N2O fluxes were best modelled on an hourly time step. Soil moisture dynamics were satisfactorily simulated by PASTIS. Simulated N2O fluxes by both NGAS and NOE (3.2 and 2.1 kg N ha(-1) y(-1) for NGAS; 7.1 and 3.7 kg N ha(-1) y(-1) for NOE, for the monoculture and shaded plantations respectively) were within a factor of about 2 of the observed annual fluxes (4.3 and 5.8 kg N ha(-1) y(-1), for the monoculture and shaded plantations respectively). Statistical indicators of association and coincidence between simulated and measured values were satisfactory for both models. Nevertheless, the two models differed greatly in describing the nitrification and denitrification processes. Some of the algorithms in the model NGAS were apparently not applicable to these tropical acidic Andosols. Therefore, more detailed information about microbial processes in different agroecosystems would be needed, notably if process-oriented models were to be used for testing strategies for mitigating N2O emissions. (C) 2009 Elsevier Ltd. All rights reserved.
Effect of legume-crop mixtures on runoff and soil loss in Africa
Blood amino acids profile responding to heat stress in dairy cows
Nitrogen dynamics of grain legume-weedy fallow-flooded rice sequences in the tropics
Dry-season (DS) grain legume-weedy fallow-wet-season (WS) flooded rice is a common cropping sequence in the rainfed lowlands of tropical Asia. To better manage N in this cropping system, we need to understand N dynamics and balances as influenced by the aerobic-anaerobic soil aeration sequence, legume cropping, biological N2 fixation (BNF), and recycling of legume residues. To understand N dynamics under a range of N derived from BNF (15N-estimated), harvested in pods and left in residues, we conducted a 2-yr experiment on a Philippine Alfisol using cowpea [Vigna unguiculata (L.) Walp.], mungbean [V. radiata (L.) Wilcz.], nodulating and nonnodulating soybean [Glycine max (L.) Merr.], and weeds. The main portion of soil mineral N (0 to 60 cm) was NO3 in the dry season and NH4 in the wet season. The sum of soil NO3 and soil N uptake at legume harvest exceeded the decrease in soil NO3 from legume seeding to harvest by 81 kg ha -1, indicating the continued production and legume uptake of soil NO3. The large differences in total N of legumes (46 to 238 kg N ha-1), however, were associated with differences in N derived from BNF (0 to 176 kg N ha-1). When pod N was excluded, legume N balance was, in most cases, negative. The average soil N depletion was 40 kg ha-1 from nonnodulating soybean, compared with 8 kg ha-1 from N2-fixing legumes. In terms of WS rice grain and N yields, legume cropping did not differ from weedy fallowing, despite greater (by up to 46 kg N
Weed suppression in legumes for stress management
Worldwide, weeds constitute a major constraint to the production of food legumes. Weeds can reduce crop yields more than 50% through competition for moisture, and this can be aggravated under the anticipated climate change scenarios. In the future, the spread of invasive alien species of weeds and herbicide resistance, which are partly aggravated by increased global trade and climate change, are likely to pose challenges to weed management and water conservation. In this chapter we will synthesize the state-of-art knowledge on weed management in legume production systems with a major emphasis on anticipated impacts of climate change and alien invasive species on weed management and water conservation. We provide a brief review of the types of weeds and weed effects followed by review of recent developments in the management of weeds in legume cropping systems. We also assess the strength and limitations of each practice and suggest the need for emphasis on the integration of different environmentally friendly control measures that are economically feasible to smallholder farmer
In Kenya, farmers see early rewards from adding legumes and trees to their farms
[No abstract available]
Fertiliser trees for sustainable food security in the maize-based production systems of East and Southern Africa. A review
The negative effects of soil fertility depletion on food security, especially among smallholder farmers in Africa, is of economic importance, and may be worsened by climate change and rising global fertiliser prices. Substantial efforts and investment have gone into development of alternative soil fertility management options. These include vigorous research and development of N-fixing plants or “fertiliser trees”, that has been on-going in the last two decades in East and Southern Africa. In this paper, we review several studies conducted both on-station and on-farm and synthesise the results in terms of improvements in soil physical, chemical and biological properties, and crop yield in response to fertiliser trees. Our major findings are that (1) fertiliser trees add more than 60 kg N ha-1 per year through biological nitrogen fixation (BNF); (2) nutrient contributions from fertiliser tree biomass can reduce the requirement for mineral N fertiliser by 75%, translating to huge savings on mineral fertilisers; (3) fertiliser trees were also shown to substantially increase crop yield. A meta-analysis has further provided conclusive evidence that with good management, fertiliser trees can double maize yields compared with local farmer practices of maize cultivation without addition of external fertilisation. (4) Financial analyses showed that fertiliser tree systems are profitable and also have higher net returns than the farmers’ de facto practice, i.e. continuous maize cropping without fertiliser. We conclude that widespread adoption and scaling up of fertiliser trees can reduce the amount of mineral fertiliser needed, maintain the soil ecosystem, and positively impact on the livelihoods of farm households in southern Africa.
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.
Availability and use of dry season feed resources on smallholder dairy farms in central Kenya
A cross-sectional survey on 41 farms followed by six weeks monitoring of dairy cattle feeding on ten smallholder dairy farms in central Kenya was conducted to investigate the use, availability and quality of dry season feed resources. Fodder production was largely from Napier grass (Pennisetum purpureum) grown on small plots and contour strips where it acts both as a fodder source as well as a biological barrier to soil erosion. There is a need to broaden the choice of fodder crops on such farms to provide a wide range of harvesting management options and to avoid total loss in case of pest or disease outbreaks. Intercropping of Napier grass with leguminous fodder trees could boost the quantity and quality of herbage production especially during the dry season. Roughage from a variety of sources was utilised during the dry season in addition to Napier grass. Among the herbages, leguminous feeds had the lowest potential dry matter degradability while weeds harvested from cropland and roadsides had the highest. Energy and protein intake from the roughage fed to grade dairy cattle during the dry season may be insufficient to meet the requirements of these animals due to the high levels of fibre concentration (acid detergent fibre and neutral detergent fibre (ADF and NDF)) in them. It is recommended that the scope for alternative sources of improved roughage such as Napier/calliandra mixtures, to boost the energy, protein and overall dry matter provision on the farms should be investigated further.