Browsing by Subject "Crop rotation"

Now showing 1 - 4 of 4

Carry‐over effect of leguminous winter cover crops and living mulches on winter wheat as a second main crop following white cabbage
(2024) Stein, Sophie; Zikeli, Sabine; Möller, Kurt
Background: The direct effect of winter cover crops (WCCs) or living mulches (LMs) on a first vegetable crop has already been investigated. However, little is known about the effect on growth and yield of a second cash crop in the rotation. Aims: The aim of the study was to assess the carry‐over effect of legumes grown as WCC or LM on winter wheat as a second crop after cabbage, measured in yield and nitrogen release. Methods: Two field trials were carried out in Germany between 2019 and 2022. In the WCC trial, rye, rye with vetch, vetch, pea, and faba bean were used as WCC and compared to bare soil. The WCC biomass was incorporated before cabbage planting in late spring. For the LM trial, perennial ryegrass or white clover was used as LM during cabbage cultivation and compared to bare soil. The LM biomass was incorporated with the cabbage residues and compared to an early incorporation of LM biomass before cabbage planting. In both trials, winter wheat was sown in the fall as the second following main crop in the rotation. Results: Leguminous WCC species had significant higher wheat yield compared to non‐legumes but not compared to the control without WCC. Late incorporation of LM biomass resulted in increased wheat yield at 10.1–10.4 Mg ha −1 compared to an early incorporation before cabbage planting at 9.35 Mg ha −1 . Net N releases show that for WCC, the main effect of legume nitrogen fixation is achieved in the first crop cabbage immediately after incorporation of WCC biomass. In the case of leguminous LM, the effects of legume nitrogen fixation are of much higher relevance in the second main crop, winter wheat, due to LM biomass incorporation after cabbage cultivation. Conclusion: Therefore, we suggest to consider not only the direct but also the carry‐over effects of leguminous cover cropping in vegetable crop rotations.
Integrating perennial biomass crops into crop rotations: How to remove miscanthus and switchgrass without glyphosate
(2023) Lewin, Eva; Kiesel, Andreas; Magenau, Elena; Lewandowski, Iris
Perennial energy grasses have gained attention in recent years as a promising resource for the bioeconomy because of their benign environmental profile, high stress tolerance, high biomass yields and low input requirements. Currently, strong breeding efforts are being made to extend the range of commercially available miscanthus and switchgrass genotypes. In order to foster farmers' acceptance of these crops, and especially of novel hybrids, more information is required about how they can be efficiently integrated into cropping rotations, how they can be removed at the end of their productive lifespan, and what effect they have on subsequently grown crops. Farmers in Europe are meanwhile increasingly constrained in the methods available to them to remove these crops, and there is a risk that the herbicide glyphosate, which has been used in many studies to remove them, will be banned in coming years. This study looks at the removal of seven‐year‐old stands of miscanthus and switchgrass over 1 year at an experimental site in Southern‐Germany. Three novel miscanthus genotypes were studied, alongside one variety of switchgrass, and the impact of each crop's removal on the yield of maize grown as a follow‐on crop was examined. A combination of soil tillage and grass herbicides for maize cultivation was successful in controlling miscanthus regrowth, such that yields of maize grown after miscanthus did not differ significantly from yields of maize grown in monoculture rotation (18.1 t dry biomass ha−1). Yields of maize grown after switchgrass (14.4 t dry biomass ha−1) were significantly lower than maize in monoculture rotation caused by insufficient control of switchgrass regrowth by the applied maize herbicide. Although some regrowth of miscanthus and switchgrass was observed in the follow‐on crop maize, complete eradication of both crops was achieved by subsequent winter wheat cultivation.
Technology adoption and farm performance in sub-Saharan Africa: evidence from Mozambique and Ghana
(2025) Asravor, Jacob; Zeller, Manfred
Increasing the productivity of agriculture in sub-Saharan Africa (SSA) is fundamental to achieving many of the Sustainable Development Goals (SDGs) in the region and, by extension, in the world. Given its importance to rural livelihoods and national economies in SSA, productivity growth in this crucial sector has the potential to stimulate broad-based poverty reduction (SGD 1) and further address the persistent food insecurity and malnutrition challenges (SDG 2) faced by the region. However, despite its potential for growth and importance to the region, productivity growth in agriculture has either stagnated or declined in SSA over the years. Efforts to tackle this persistent challenge have been focused on the promotion of improved technological packages and modern farming practices in various parts of the region. Nonetheless, adoption has mostly remained sluggish across SSA, stressing the continuing need for a deeper understanding of the underlying barriers to sustained adoption, as well as the effects of adopted technologies and farming practices on farm performance, particularly in terms of technical efficiency and technological gains. The smallholder farming contexts of Mozambique and Ghana offer distinct cases for gaining useful insights into the underlying barriers to sustained adoption of modern technologies and farming practices, as well as their effects on farm performance. Specifically, despite ongoing efforts by the Mozambican government and development partners to promote sustainable intensification practices, such as integrated soil fertility management (ISFM) practices (including mineral fertilizer, improved seeds and depending on the location, organic inputs such as manure and compost), adoption remains low among farm households. As a result, resource-poor farmers often resort to unsustainable land use practices, such as shifting cultivation, slash-and-burn agriculture, deforestation and forest degradation, along with low-cost agronomic practices like crop rotation, crop residue retention and intercropping to safeguard soil fertility. However, evidence is scarcely available on the underlying barriers to sustained adoption of promoted ISFM practices, along with the technological and technical efficiency gains associated with integrating improved versus recycled seeds with agronomic practices in Mozambique. Furthermore, one of the key challenges to technology adoption, as well as to farm performance and the long-term sustainability of agriculture, is the issue of aging farming population. This issue is particularly pressing in Ghana, where, in addition to the growing disinterest of young people in farming and an estimated life expectancy ranging from 55 – 65 years, the average age of farmers is reported to be 55. Given that the majority (73.5%) of Ghana’s population is below the age of 36, an improved understanding of how farm operators’ age influences their managerial performance and technology adoption is crucial for shaping evidence-informed policies aimed at attracting, retaining and leveraging this demographic dividend within the Ghanaian agricultural sector. From the foregoing, this thesis has three key objectives: (1) to explore context-specific evidence on the systemic barriers to sustained adoption of integrated soil fertility management (ISFM) practices by Mozambican smallholder farmers; (2) to examine the technological and technical efficiency gains associated with integrating improved versus recycled seeds with agronomic practices such as crop rotation, intercropping and crop residue management by Mozambican smallholder farmers; and (3) to assess how the age of farm operators – disaggregated into the youth, middle-aged and aged – influences their managerial performance and farm technology adoption in Ghana. The objectives of this thesis were achieved using data from both primary and secondary sources. Relying on mixed-methods research design, qualitative data were drawn using key informant interviews (KIIs) and focus group discussions (FGDs), and quantitative data via a household survey in the Central and Northern zones of Mozambique. These primary data were used to address the first and second objectives of the thesis. Overall, 32 qualitative interviews, consisting of 8 FGDs, 5 medium- and large-scale farmer KIIs and 19 expert KIIs were conducted in Mozambique. This was followed by a household survey which was conducted in the Central and Northern zones of Mozambique, involving 607 farming households who were selected through a multi-stage sampling technique. Both datasets were collected in 2022. To address the third objective of the thesis, secondary data from two nationally representative surveys in Ghana were used. These include all seven waves of the Ghana Living Standards Survey (GLSS) which were conducted from 1987/88 – 2016/17 and the two waves of the Ghana Socio-economic Panel Survey (GSPS) conducted between 2009/10 and 2014/15. While the GLSS was implemented using a repeated cross-sectional design, the GSPS followed a panel design. Overall, 24,596 farm households across Ghana were included in the sample for analysis. This thesis is organized into five chapters. Chapter 1 introduces the research topic by providing a general overview of the study within the global and sub-Saharan African contexts, followed by background information on agriculture and technology adoption in both Mozambique and Ghana. Chapter 2 explores the systemic barriers that continue to impede the sustained uptake of ISFM practices among Mozambican smallholder farmers. Chapter 3 evaluates the technological and technical efficiency gains associated with existing farmer practices of integrating improved versus recycled seeds with agronomic practices in Mozambique. Chapter 4 examines the relationship between farm operators’ age, technology adoption and managerial performance in Ghana. Finally, chapter 5 presents the conclusion of the thesis, outlines its limitations and makes recommendations for policy and future studies. Chapter 2 relies on mixed-methods research design to explore the systemic barriers to sustained adoption of ISFM practices among Mozambican resource-poor farmers. Complementing content analysis of qualitative data with descriptive analysis of data from a household survey, the findings indicate that whereas Mozambican smallholder farmers have generally recognized the compelling need for ISFM practices in high-value crop production systems such as vegetables, cotton, sugarcane and tobacco, they are reluctant to make similar investments in food crops. Instead, they adopt low-cost agronomic practices such as crop residue management, intercropping, crop rotation and shifting cultivation to safeguard soil fertility in food crop systems. Evidence further shows that the use of improved seeds, mineral fertilizers and depending on the location, external organic inputs such as manure and compost, is more prevalent among three groups of Mozambican smallholder farmers: independent vegetable producers, farmers participating in contract farming schemes and those residing in districts bordering Malawi, Zambia and Zimbabwe. Additionally, despite expressing strong willingness to invest in these inputs, farmers’ access to and use of these inputs are hindered by a complex set of systemic barriers, including unfavorable market conditions which limit profitability and intensify risk; institutional limitations such as credit constraints and human capital limitations; liquidity constraints; challenges associated with key ISFM components; an existing culture of dependency shaped by past experiences of farmers with free inputs; and entrenched perceptions among both farmers and professionals that Mozambican soils are inherently “fertile” or “virgins” and “fertilizers destroy the soil”. Given these findings, the study recommends that interventions aiming to promote sustainable land use practices like ISFM in land-abundant contexts of SSA like Mozambique, should prioritize addressing these systemic barriers to ensure sustained adoption of these practices. For instance, to raise productivity in food crop systems, agrarian interventions should adopt a holistic value chain approach which goes beyond the production phase to strengthen other critical segments of the value chain, such as extending agro-dealer networks to major production areas, as well as enhancing access of smallholder farmers to output markets that offer stable and fair prices. Again, there is the urgent need to intensify education and raise awareness among both farmers and professionals to dispel the widespread misconception that fertilizers damage the soil and on the need for farmers to implement ISFM as a package rather than in isolation. Addressing these systemic constraints holds an enormous prospect for fostering the sustained uptake of sustainable intensification practices like ISFM in Mozambique. Drawing on the findings from chapter 2, which indicates that Mozambican smallholder farmers seldom invest in purchased inputs for food crops, chapter 3 utilizes the same data to assess the technological and technical efficiency gains associated with existing farmer practices of integrating improved versus recycled seeds with agronomic practices, including crop rotation, intercropping and crop residue management in food crop systems. Relying on an endogeneity-corrected stochastic frontier and metafrontier functions to analyze the quantitative data, results from this first-stage analysis were contextualized and reinforced with evidence from the qualitative data. The findings suggest that farm households who integrated improved seeds with agronomic practices achieve a modest technological advantage (4%) relative to their peers who integrated recycled seeds with these same practices. Nonetheless, the results reveal no significant difference in technical efficiency between both groups. Instead, farm households in both groups performed these agronomic practices so poorly, such that each group could expand its total farm production by more than 50% simply by implementing these existing agronomic practices more efficiently. Consequently, the greatest potential for raising farm output in food crop systems in Mozambique lies in the capacity of resource-poor households to effectively implement these existing agronomic practices. Based on the findings, it is recommended that programs aiming to boost productivity in food crop systems in Mozambique should prioritize building the capacity of farm households to enable them implement these agronomic practices more efficiently. Encouraging resource-poor farmers to strictly adhere to recommended agronomic protocols, such as selecting the right crop mixes for intercropping and rotation, retaining crop residues on the field and using inoculants to boost nitrogen fixation in legumes can considerably enhance soil fertility and support productivity in subsequent crops. Given the increasingly aging farming population in Ghana and the urgent need for evidence-informed policies aimed at attracting and retaining the country’s growing youth population in agriculture, chapter 4 of the thesis relies on a nationally representative data from the GLSS and GSPS to evaluate how the age of resource-poor farmers influence their farm-level decision-making in terms of technology adoption and managerial performance. Drawing on a three-decade dataset from cereal-producing households and guided by the definitions of youth provided by the African Youth Charter and Ghana’s National Youth Policy, farm households were categorized into three age-based groups: youth (15–35 years), middle-aged (36–59 years) and aged (60 years and above). The findings indicate that farm operator age does not have a statistically significant effect on the type or level of agricultural technology adopted by farming households in Ghana. This finding remains robust even when the analysis is disaggregated by cereal type (i.e., maize, rice, millet and sorghum). However, the findings reveal marked differences in managerial performance between younger and older farmers, with the youth exhibiting greater managerial proficiency relative to their older peers. These findings suggest that when offered equal access to productive resources, younger farmers are better equipped to drive agricultural productivity growth in Ghana, thereby significantly contributing to the sector’s growth in the country. The study recommends for policymakers to pursue youth-focused agrarian initiatives that ensure easy access of the youth to productive resources such as land, credit and improved technologies, aimed at enabling younger farmers to leverage their potential in driving agricultural productivity gains. Overall, the findings of this thesis bring to the fore the existing systemic barriers that continue to obstruct smallholder investment decisions in sustainable land use practices like ISFM in land-abundant contexts like Mozambique and further underscore the urgent need for policy measures aimed at addressing them. It further stresses that the greatest potential for sustainably raising farm performance in low-input food crop systems in Mozambique lies in the ability of resource-poor farmers to implement these low-cost agronomic practices more efficiently. Finally, the findings highlight the need to focus on enhancing the managerial skillsets of farm operators across all age groups, especially the younger ones, rather than just concentrating on technological advancements.
Turbulent exchange of energy, water and carbon between crop canopies and the atmosphere
an evaluation of multi-year, multi-site eddy covariance data
(2019) Eshonkulov, Ravshan; Streck, Thilo
The increase of anthropogenic CO2 emissions and other greenhouse gases has raised concern about climate change. Climate change has manifold impacts on yield and yield quality, crop rotations, carbon and nitrogen cycling, water regime and agricultural production systems. To understand its consequences on environmental systems, measuring the matter and energy exchange at the land surface provides data to help validate and inform a wide range of process models. Such flux measurements at the land-surface provide an opportunity to test simulations of processes in the soil-plant-atmosphere continuum. Currently, such measurements are mainly based on the eddy covariance (EC) method, for the quality of which the energy balance closure (EBC) is a problem. The EBC significantly influences the calibration and validity of land-surface models, especially in regard to the energy and water balance at the Earth’s surface. The EBC quantifies the deviation between turbulent fluxes and available energy. It is crucial to obtain high-quality EC measurements to determine the reasons for the EBC. The research aims of this dissertation were: 1) to clarify the role of minor storage and flux terms in the energy balance, 2) to determine the possible reasons for the energy imbalance using a long-term dataset (2010-2017) from agricultural croplands, and 3) to investigate the effects of region, site, year and crop type on carbon fluxes and budgets. In the first study (Chapter 2) the contribution of minor storage terms to the EBC were investigated. I also determined the contribution of ground heat fluxes calculated by different methods. A harmonic analysis method was used to calculate ground heat fluxes from measurements of heat flux plates and soil temperature sensors. Soil heat storage and enthalpy change in the plant canopy were determined at different locations within the EC footprint. Considering minor storage terms improved the energy balance closure on average by 5.0 % in 2015 and by 6.8 % in 2016. The greatest energy balance closure improvement occurred in May of both study years. The dominant fraction of minor energy storage was energy uptake and release through photosynthesis and respiration. Additionally, the energy fluxes related to soil temperature change were also observed. The ground heat flux calculated by harmonic analysis from soil heat flux plates narrowed the EBC by 3 % compared to the calorimetric method. The results indicated that the typical correction approach to achieve energy balance closure, i.e. the Bowen-ratio method, overestimated the turbulent fluxes. The second study (Chapter 3) investigated the effects of crop type, site characteristics, wind directions, atmospheric conditions and footprint on the EBC. The long-term evaluation of EC measurements showed that, with the EC method, 25 % of the available energy could not be detected. Decreasing the flux footprint area increases the chance of a more homogeneous area. Homogeneity plays an important role in achieving a better energy balance closure. The synthesis of long-term EC data indicated that the sonic anemometer is very sensitive to orientation, not allowing accurate measurements from all wind directions. Discarding the measurements from wind directions 0° and 90° at EC4 improved the EBC from 80 to 84 %. In the third study, presented in Chapter 4, a long-term and multi-site experiment was evaluated to clarify the effects of site, year and region on the CO2 fluxes and budgets in agroecosystems. The net ecosystem exchange of CO2 fluxes – measured on six sites during eight years – was comprehensively examined. Winter rapeseed had the lowest CO2 uptake, cropping of silage maize resulted in the highest C losses. The management of harvest residues was the most effective means of controlling the C budgets. Comparing the CO2 fluxes processed with the recently developed ogive optimization method versus the conventional calculation showed that eliminating low-frequency contributions had a considerable effect. On average, the ogive optimization method delivered 6.9 % higher net ecosystem exchange rates than the conventional method. This dissertation provides new insights into how to obtain better measurements of matter and energy fluxes from EC measurements by a) considering storage terms otherwise neglected, b) using harmonic analysis for calculating ground heat fluxes, c) discarding fluxes from behind the anemometer and d) applying the ogive optimization method.