Browsing by Subject "Cropping system"

Now showing 1 - 4 of 4

Agricultural diversification of biogas crop cultivation
(2018) von Cossel, Moritz; Lewandowski, Iris
For all types of agricultural land-use, more diverse cropping systems are required, with respect to the maintenance of ecosystem values such as biodiversity conservation and climate change adaptation. This need for greater agricultural diversity is clearly illustrated by biogas crop cultivation. In Germany, maize currently dominates biogas crop cultivation due to its outstanding methane yield performance. However, the ecosystem value of maize cultivation decreases if good agricultural practices are ignored. Additionally, the poor aesthetical value of maize has led to biogas production gaining a negative reputation in society. To increase the diversity of biogas crop cultivation, alternative biogas crops such as amaranth and wild plant mixtures need to be investigated with respect to both yield performance and biogas substrate quality. The research objective of this study was the development of strategies for agricultural diversification of biogas crop cultivation. For this purpose, the following research questions were formulated: 1. How does amaranth perform as a biogas crop compared to maize and what are the major opportunities for and obstacles to the large-scale implementation of amaranth cultivation? 2. How does the spatial diversification ‘legume intercropping’ perform in amaranth compared to maize and what are the major opportunities for and obstacles to its practical implementation? 3. How do perennial wild plant mixtures perform in biomass production with respect to yield, quality and species diversity in the long term and what are the relevant agronomic factors? 4. How do available models perform in the prediction of specific methane yield of different crops based on their lignocellulosic biomass composition and how could they be improved? To address research questions 1 and 2, field trials with amaranth and maize were conducted in southwest Germany in the years 2014 and 2015. Amaranth established well in both years. Its dark red inflorescences attracted many insects such as honeybees, wild bees and bumble bees. Therefore, a systematic implementation of amaranth into biogas crop rotations could significantly improve their socio-ecological value in terms of biodiversity conservation and landscape beauty. However, amaranth showed significantly lower dry matter yields (DMY) and specific methane yields (SMY), together resulting in lower methane yields than maize in both years. Therefore, breeding and an optimization of agricultural practices such as sowing density, planting geometry and fertilization management are required to make amaranth more competitive in comparison to maize. To address research question 2, the amaranth field trials mentioned above also included treatments of legume intercropping with runner bean (RB, Phaseolus vulgaris L.) and white clover (WC, Trifolium repens, L.). The RB and WC developed equally well in amaranth and maize each year. For both amaranth and maize, the RB share of total DMY was low (5-10%) and did not significantly affect the total DMY. By contrast, WC had a significant negative effect on the DMY. Overall, the spatial diversification ‘legume intercropping’ could considerably improve the socio-ecological value of amaranth cultivation in terms of biodiversity conservation, greenhouse gas (GHG) mitigation and soil protection. For research question 3, two different wild plant mixtures (WPM) were cultivated on three sites in southwest Germany from the years 2011 to 2015. At each location, the WPM showed great potential for both biodiversity conservation and ecosystem resilience. Numerous insect species were observed in the WPM stands each year, indicating WPM as a relevant cropping system for habitat networking. Furthermore, the aesthetic appearance of the WPM stands over the years demonstrated the potential positive effect WPM cultivation could have on the public perception of biogas production. The DMY of the WPM varied strongly depending on (i) the initial composition of species sown, (ii) the establishment procedure, (iii) the environmental conditions, (iv) the pre-crop, and (v) the number of predominant species. WPM were found to have low demands for fertilization and crop protection. Thus, WPM appear a promising low-input cropping system for the promotion of biodiversity conservation, habitat networking, soil and water protection, GHG mitigation and climate change adaptation. However, high DMY gaps remain a challenge for the practical inclusion of WPM in existing biogas cropping systems. With respect to research question 4, a meta-analysis revealed that available models proved to be much less precise than expected. Although outperforming all available models, the correlation of the new models was still low (up to r = 0.66). It was also found that non-linear terms are of less importance than crop-specific regressors including the intercept. This indicates that across-crop models including crop-specific configurations could help to improve the identification of alternative crops and cropping systems for a more diverse biogas crop cultivation in the future.
Agronomic strategies to reduce potential precursors of acrylamide formation in cereals
(2020) Stockmann, Falko; Graeff-Hönninger, Simone
Food safety is of great importance as harmful substances formed during food processing can negatively affect human health. When the carcinogenic food ingredient acrylamide (AA) accidentally appeared in 2002, it was not expected that AA would take this much attention during the next years. Yet, after around 15 years of research, AA has finally been recognized as being harmful. In a first step, research focussed on food processing implications on AA formation. The impact of heat treatment, time of heating, baking agents, fermentation time, additives and enzymes were reported in several studies. Nevertheless, since 2011 food AA levels seem to stagnate or even increase in some years. Thus, the food industry did not show sufficient progress in reducing AA. Reducing sugars and amino acid free asparagine (Asn) are the main AA precursors. They can fluctuate in their content for instance in grain flour or potatoes shifting the focus of AA origin to the raw material. Thus, the production of raw material low in AA precursors seems important. However, lowering precursors of AA in the raw material necessitates suitable agronomic strategies to grow cereal species and cultivars low, especially in free Asn. Hence, the major goal of this thesis was to investigate the following questions concerning their impact on free Asn formation in cereals: 1. Which role does the management system plays, as organic vs. conventional farming systems highly differ in their cropping strategies? 2. What is the best nitrogen fertilization strategy when comparing organic vs. conventionally cropping systems? 3. Is there an impact of sulphur fertilization concerning sulphur amount and sulphur type? 4. Can expanding row distance and lowering seed density in low-input farming systems positively influence baking quality while keeping free Asn amounts low? 5. For organically grown cereals no level of free Asn was available. Thus, the question came up to which extent organically grown cereal species and cultivars including ancient grains like einkorn and emmer differ in free Asn. 6. Should free Asn be implemented in breeding programs if heritability is high? 7. Is there an impact of harvest timing on free Asn formation? Out of several field trials the following results were obtained: • The cropping system had a significant impact on grain yield, the level of free Asn and quality traits. Across all species, free Asn contents in flour were 26% lower under organic conditions compared to conventional farming. For wheat a maximum reduction of 50% in free Asn content was possible if organically produced. Spelt and rye were affected to a minor extend as only in single years organically grown cultivars showed up to 33% lower Asn contents. • Nitrogen (N) fertilization significantly influenced grain yield and baking quality in both cropping systems. In contrast, up to a certain amount of N free Asn was only affected to a minor extend. In particular, within the organic farming samples no significantly higher free Asn amounts were determined even if N fertilizer was raised or the N form was changed. A late N fertilization within the conventional cropping system increased crude protein content, while no clear effect was found on free Asn. Also, cultivars affected free Asn level significantly. Wheat cultivar Capo exhibited the lowest AA formation potential at a N supply of 180 kg N ha−1 while simultaneously reaching a crude protein content > 15% (conventional) and > 12% (organic). Thus, lowering free Asn by adjusting N treatments should not necessarily affect baking quality. In general, free Asn amounts in wheat varied widely both within cultivars and between cropping systems. Besides N, neither type nor amount of sulphur fertilization influenced free Asn significantly. • Extending row distance can increase quality traits protein and sedimentation value. Seed density was highly related to grain yield and test weight. Most importantly, free Asn was only minor affected by both treatments. Thus, larger row distances can be recommended to raise baking quality in organic farming systems without simultaneously affecting free Asn. Number of grains spike-1 seems to be related to free Asn (R2=0.72). This provides new insights on Asn synthesis during grain development and offers the opportunity to predict free Asn formation without expensive chemical analyzes. In contrast Asn and protein content did not show any relation while high protein contents in grain seem to lower AA amount in heated flour samples. • The impact of organically grown cereal species and cultivars in combination with marginal N supply on free Asn was clearly shown. A reduction potential of 85% was reached if rye was replaced by spelt. Surprisingly, the ancient species einkorn and emmer reached a very high free Asn content similar to rye. Heritability was high for wheat and spelt concerning locations, while regarding years, heritability was low for wheat but high for spelt and rye. For organically grown cereals, the relation between free Asn and AA formation was proven. Across species and years free Asn can serve as an indicator for AA formation (R2 of 0.69). • Harvest timing affects free Asn levels. In this context a delayed harvest can increase Asn significantly while shifting harvest 1-2 weeks earlier decreased Asn by up to 60% depending on cereal species and cropping system. After summarizing and stating the most promising steps in the frame of agronomic strategies to lower free Asn, a prediction tool for free Asn should be implemented that classifies the impact of agronomic strategies and leads to recommendations to farmers. Finally, the main riddle, that should be solved during the next studies is the question, why cereal species and cultivars differ in their Asn formation. This thesis gives some preliminary ideas but a much deeper insight is essential to establish long-term strategies to lower free Asn content.
Developing cropping systems for the ancient grain chia (Salvia hispanica L.) in two contrasting environments in Egypt and Germany
(2020) Mack, Laura; Graeff-Hönninger, Simone
Chia (Salvia hispanica L.) seeds have been revived as functional “superfood” for human nourishment especially for vegan and vegetarian diets and are becoming increasingly widespread and present in new food products in Europe. The seeds are beneficial because of being gluten-free, containing antioxidants and a high concentration of α-linolenic acid, and having a high content of dietary fiber and high-quality protein. Chia is originally adapted to short-day conditions and grows naturally in tropical and subtropical environments. Nevertheless, it can survive under water stress and could, therefore, be cultivated in arid regions. Egypt has been classified as a water-scarce state. Due to its drought tolerance, chia might contribute to saving the scarce source “water” in Egypt and offer the chance to export these high value seeds, generating foreign exchange for reimporting e.g. wheat characterized by a higher water demand. Worldwide, the biggest problems and key challenges under climate change (CC) are water and food security in arid and semiarid regions. In the future, CC and water scarcity will significantly threaten agriculture and sustainable development. A rising population requires on the one hand an increase in food grain production, but also a change toward environmentally sound sustainable agriculture. Chia has been suggested as a favorably economic alternative for common field crops sustaining diversification and stabilization of the local agricultural economy. However, broad experience in growing chia in new environments is missing. The agronomic management has not been improved from formerly small-scale production systems. Most of the previous studies focused on seed characteristics. Information on fertilization, plant protection, and improved varieties is scarce, which are reasons for its low productivity in the countries of origin. Field experiments were conducted at the experimental station “Ihinger Hof” of the University of Hohenheim in southwestern Germany from 2015 to 2017 and in Egypt during the cropping season 2015 to 2016 at SEKEM’s experimental station located 50 km Northeast of Cairo. The present doctoral thesis was based on a project embedded in the graduate school Water-People-Agriculture (WPA) at the University of Hohenheim funded by the Anton-&-Petra-Ehrmann foundation that focuses on key water issues and water related challenges of todays society. On a final note, the main results of this thesis provide further information and expanded knowledge on chia cultivation in two contrasting environments (including a desert region) out of its center of origin. Overall, the current doctoral thesis presents a combined approach of experimental field research and crop modeling to support the optimization of farming practices of chia in new environments. A universal and nondestructive LA estimation model for chia was developed. Further, the CROPGRO model was adapted for chia to provide a preliminary model for a realistic simulation of crop growth variables. The approaches presented in this thesis may contribute to testing new environments for chia cultivation and to improving its production. Moreover, this study helped to develop further general model source codes to simulate the growth of tiny seeds. The adaptation to other Salvias should be much easier with this developed model. Future research requirements and issues requiring model improvement such as N-response and the development of code relationships that can simulate parameters of seed quality could improve the plant growth model for chia.
Sustainable bioenergy cropping concepts : optimizing biomass provision for different conversion routes
(2014) Mast, Benjamin; Claupein, Wilhelm
Today energy from biomass already contributes to a considerable share to the global energy consumption. In particular, certain modern bioenergy streams like biogas, biofuels for transportation etc., are of increasing relevance. However, several of the beneficial aspects, which were initially attributed to the utilization of today’s bioenergy, had to be relativized and the controversies regarding environmental and socio-economic drawbacks have, in the meanwhile, been on the rise. Alongside a shift to advanced conversion technologies, the improvement of bioenergy cropping systems towards a sustainable biomass provision is a key element of future bioenergy production. Against this background, the present thesis assessed various aspects in terms of biomass production, biomass provision and biomass conversion mainly addressing the two bioenergy streams – 2nd generation biofuels and biogas. For biogas, the thesis addresses aspects regarding the development of alternative cropping systems, the evaluation of novel crops for biogas purpose, and the assessment of regional biogas potentials using a crop growth model. The second focus of the thesis was set on biofuels while special attention was given to the production of microbial biodiesel, and the characterization and evaluation of potential feedstocks for this purpose.