Principally caused by soil water stress and declining soil fertility, low crop productivity results in both food and income insecurity. The effects of nitrogen and phosphorus fertilizer micro-dosing with inter-row rainwater harvesting practices for maize and pigeon-pea inter-cropping on yield and land use efficiency are inadequately documented in sub humid tropics. A field experiment on sandy loam soils in sub humid conditions using a split-split plot design was conducted. Plots used in situ rainwater harvesting practices of tied ridges, open ridges, and flat cultivation. Sub-plots were sole maize, sole pigeon-pea, and 1:1 maize-pigeon pea inter-cropping. The sub-sub plots were control, fertilizer (N and P) application at the micro-dose level, and recommended rates. Tied ridges significantly (p < 0.001) conserved more soil moisture than flat cultivation at 30 cm depth after ten days of rainfall. Ridges increased maize yield by 0.3 t ha−1 over flat cultivation. Fertilizer application significantly (p < 0.001) increased maize yield by 1.12 t ha−1 with micro-dosing and by 1.60 t ha−1 with recommended rates over the control. Combining tied ridges and fertilizer significantly (p < 0.040) increased maize yield by 132–156% compared to flat cultivation without fertilizer. Reflecting a land equivalent ratio, land use efficiency was 67–122% higher in inter-cropping than sole crop. Tied ridges conserved more soil moisture than flat cultivation, enhancing fertilizer use efficiency that improved crop yields and land equivalent ratio under inter-cropping. This strategy could increase food availability and income generation under smallholder farming systems in sub-humid tropic areas.
Tag: legume
Can Integration of Legume Trees Increase Yield Stability in Rainfed Maize Cropping Systems in Southern Africa?
Growing maize (Zea mays L.) in association with legume trees in agroforestry arrangements has been shown to increase yields in many parts of sub-Saharan Africa; however, the stability of crop yields has not been critically analyzed in the various cropping systems that integrate leguminous trees. The objective of this analysis was to compare yield stability in improved cropping systems, namely maize–gliricidia [Gliricidia sepium (Jacq.) Kunth] intercropping and fertilized monoculture maize, with the de facto practice of resource-poor farmers who grow maize continuously without any external input. Yield stability was determined for three long-term field trials (12–13 consecutive yr) conducted at Makoka Research Station in southern Malawi and Msekera Research Station in eastern Zambia. At Makoka, the most stable yield was recorded in maize–gliricidia intercrops. Average yield was highest for maize–gliricidia intercropping amended with 50% of the recommended N and P fertilizer, and this was comparable with the yield recorded in monoculture maize that received inorganic fertilizer. On the two sites at Msekera, the highest yield was recorded in fertilized monoculture maize, followed by maize–gliricidia intercrops. Yields were more stable, however, in maize–gliricidia intercropping than fertilized maize on both sites at Msekera. It was concluded that maize yields remain more stable in maize–gliricidia intercropping than in fertilized maize monoculture in the long term, although average yields may be higher with full fertilization.
Quantity and quality of organic inputs from coppicing leguminous trees influence abundance of soil macrofauna in maize crops in eastern Zambia
Soil invertebrates are the major determinants of soil processes such as organic matter decomposition and nutrient cycling. However, the effect of quantity and quality of organic inputs on soil biota has not been studied in agroforestry systems in southern Africa. Variations in soil macrofauna abundance under maize grown in fallows of Gliricidia sepium, Acacia anguistissima, Leucaena collinsii, Leucaena diversifolia, Leucaena esculenta, Leucaena pallida, Senna siamea, Calliandra calothyrsus and monoculture maize were assessed at three sites with contrasting agro-ecological conditions in eastern Zambia. It was hypothesised that spatial variations in soil macrofauna abundance under maize crops are mediated by heterogeneity in the quality and quantity of organic inputs produced by these legumes. The relationships between the abundance of macrofauna groups and litter, leaf, stump re-sprout and recycled biomass, stump survival and the quality index lignin (L)+polyphenol (P) to nitrogen (N) ratio were assessed using generalised linear models assuming spatial randomness (Poisson distribution) and aggregation (negative binomial distribution). Earthworms, beetles and millipedes showed spatial aggregation, which was partly explained by the heterogeneity in organic resource quantity and quality. Earthworms and beetles were more abundant under legumes that produced high quantities of biomass with low (L + P) to N ratios and species that have high stump survival after coppicing. Millipedes were favoured by species which produced high quantities of biomass with high (L + P) to N ratios. Although ants and termites showed spatial aggregation, their distributions were not influenced by the quantity or quality of biomass produced by the legumes. Centipedes and Arachnida showed spatial randomness, and their distribution was not influenced by any of the organic quality and quantity variables.
Simple solutions for complex problems? What is missing in agriculture for nutrition interventions
Within the nutritionism paradigm, in this article we critically review the marketization and medicalization logics which aim to address the pressing issue of malnutrition in low- and middle-income countries. Drawing from political economy and food system transformation discourses, we are using the popular intervention types of nutrition-sensitive value chains (marketization logic) and biofortification exemplified through orange-fleshed sweet potato (medicalization logic) to assess their outcomes and underlying logics. We demonstrate that there is insufficient evidence of the positive impact of these interventions on nutritional outcomes, and that their underlying theories of change and impact logics do not deal with the inherent complexity of nutritional challenges. We show that nutrition-sensitive value chain approaches are unable to leverage or enhance the functioning of value chains to improve nutritional outcomes, especially in light of the disproportionate power of some food companies. We further demonstrate that orange-fleshed sweet potato interventions and biofortification more broadly adopt a narrow approach to malnutrition, disregarding the interactions between food components and broader value chain and food system dynamics. We argue that both intervention types focus solely on increasing the intake of specific nutrients without incorporating their embeddedness in the wider food systems and the relevant political-economic and social relations that influence the production and consumption of food. We conclude that the systemic nature of malnutrition requires to be understood and addressed as part of the food system transformation challenge in order to move towards solving it. To do so, new evaluation frameworks along with new approaches to solutions are necessary that support multiple and diverse development pathways, which are able to acknowledge the social, political-economic, and environmental factors and drivers of malnutrition and poverty.
Conservation agriculture improves adaptive capacity of cropping systems to climate stress in Malawi
Context: Adaptation to climate stress is an unprecedented challenge facing cropping systems. Most adaptation assessments focus on how adaptation options affect yields of a single crop under different weather or climate conditions. Yet, cropping systems often comprise more than one crop, and holistic assessments should consider all crops grown in a cropping system. One adaptation option is Conservation Agriculture that is commonly defined around a set of three principles: minimum mechanical soil disturbance, permanent soil organic cover, and crop species diversification. Objective: Here we estimated the statistical effect of Conservation Agriculture on cropping-system yields under historical climate conditions. Methods: The cropping-system yields considered all crops grown including maize (Zea mays L.) and legumes in intercropping or rotation, or both. The climate conditions included conditions of heat stress for maize and precipitation balances during the maize growing season. Heat stress for maize was studied using growing degree days over 30 °C. Precipitation balance was the difference between precipitation and reference evapotranspiration. Data included 6296 yield observations from on-farm trials in farmer plots conducted over 14 seasons (2005–2006 to 2018–2019) in ten communities in Malawi. These yield data were coupled with daily weather data. We studied three treatments: (1) a Control Practice treatment where the soil was tilled, crop residues were removed, and there was no crop species diversification, (2) a No-Tillage treatment where the soil was not tilled, crop residues were retained, and there was no crop species diversification, and (3) a Conservation Agriculture treatment where the soil was not tilled, crop residues were retained, and there was crop species diversification through legume intercropping. The use of maize varieties and legume rotation changed over time; however, the treatments studied remained the same over the entire length of the on-farm trials period in all individual communities. Results and conclusions: Results of our study showed that heat stress for maize had a negative effect on cropping-system yields for non-stress-tolerant maize varieties and no legume rotation, although the Conservation Agriculture treatment reduced this negative effect compared with the Control Practice treatment. With the use of stress-tolerant maize varieties and legume rotation and Conservation Agriculture, our results suggest that heat stress for maize did not have a negative effect on cropping-system yields. Significance: Our results demonstrate how Conservation Agriculture can improve the adaptive capacity of cropping systems and this provides urgently needed evidence on how farmers can adapt to climate stress.
Measuring household legume cultivation intensity in sub-Saharan Africa
Legumes form part of an ecological-based solution to intensification in areas with limited access to external inputs. Despite a number of decades of intervention, uptake of legumes has been slow within smallholder farming systems in sub-Saharan Africa. We explore the drivers behind the adoption of legumes by developing an indicator of household legume cultivation (HLC) from a bespoke survey of small-scale farm households in Kenya and the Democratic Republic of the Congo. A beta regression framework identifies the range of intensities across sites and farms, indicating a limited influence of agro-ecological zones and formal institutions on uptake. Age, income and gender have positive but very marginal effects. Intensive legume cultivations were less driven by commercial growth objectives or access to market oppourtunities indicating lack of legume markets to incentivize production. There was little interest in expanding farm area, which reflects the lack of assets available to these farmers and leads to the use of legumes for providing home nutrition, or supporting farm fertility and livestock feed. Further development of this HLC metric would be enabled by consistent data gathering across regions, or at least equally detailed studies of legume uptake. © 2021 Informa UK Limited, trading as Taylor & Francis Group.
Gliricidia intercropping supports soil organic matter stabilization at Makoka Research Station, Malawi
Intercropping agriculture with legume trees is a promising strategy to improve soils with low soil organic matter (SOM) and nitrogen (N) contents, which is a common problem in many Southern African regions. Objective of this research was to explore long-term effects of legume-intercropping on SOM pools and soil fertility. We examined a maize-based cropping system with gliricidia (Gliricidia sepium) as intercropping legume tree on a Ferric Lixisol in Southern Malawi. The experimental trial at Makoka Research Station was in its 29th year of management with leaf biomass incorporated into the soil regularly. We determined concentrations of organic carbon (C) and N, exchangeable cations, and available phosphorus (P) of topsoil samples (0–20 cm). We used density fractionation of SOM to gain fractions that roughly approximate SOM pools with fast turnover (not associated to soil minerals), intermediate turnover (occluded within soil aggregates) and slow turnover (mineral associated SOM). We further determined water dispersible clay (WDC) and pedogenic oxides, as these are often involved in the C-stabilization process in tropical soils. Maize-gliricidia intercropping plots showed higher soil pH-values, and higher concentrations of exchangeable Mg and Ca than plots with maize monoculture. In addition, significantly higher contents of C (17.3 vs. 7.03 g kg−1) and N (1.51 vs. 0.7 g kg−1) were found at intercropping plots indicating a C-sequestration rate of 0.3 g C kg−1 a−1, while monoculture induced the loss of SOM with a rate of −0.1 g C kg−1 a−1. C and N contents doubled in pools with fast and with slow turnover and increased by >300% in SOM pool where C and N is bound in soil aggregates. Concomitantly, WDC was significantly lower in intercropping plots than in monoculture plots. Our data emphasize the fast turnover of SOM in subtropical soils and indicate that SOM in arable soils decreases continuously without suitable C-input strategy. Maize-gliricidia intercropping had positive effects on biomass production and C-input at Makoka Research Station and improved soil fertility. In addition, aggregate formation was enhanced and storage of SOM within aggregates and at mineral surfaces increased. Our results indicate a great potential of maize-gliricidia intercropping for improved C management in subtropical Lixisols. Intensive monitoring seems to be promising to validate and quantify the impacts of this measure.
Innovative agronomic practices for sustainable intensification in sub-Saharan Africa. A review
Africa’s need to double food production and feed the burgeoning human population, without compromising its natural resource base, has raised the momentum for sustainable agricultural intensification on the continent. Many studies describe agronomic practices that can increase productivity on existing agricultural land without damaging the environment and without increasing the agricultural carbon footprint. However, there is limited information on specific practices with the greatest potential to contribute to sustainable intensification on smallholder farms in sub-Saharan Africa, while simultaneously keeping the carbon footprint low. The objectives of this review were to (1) identify good agronomic practices with potential for contributing to sustainable intensification across sub-Saharan Africa, (2) synthesize available information on benefits and synergies from these technologies, and (3) discuss bottlenecks in their adoption in order to obtain insights that inform the formulation of supportive policies. Agroforestry, cereal-legume intercropping, conservation agriculture, doubled-up legume cropping, fertilizer micro-dosing, planting basins, and push-pull technology were identified as key agronomic innovations widely promoted in sub-Saharan Africa. We show that these innovations can build synergies and increase resource use efficiency while reducing agricultural carbon footprint. We outline the benefits, trade-offs, and limitations of these practices and discuss their potential role in strengthening food sovereignty and climate change adaptation and mitigation.