Institut für Kulturpflanzenwissenschaften

Permanent URI for this collectionhttps://hohpublica.uni-hohenheim.de/handle/123456789/12

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Improving cover crop mixtures to increase soil carbon inputs and weed suppression as a tool to promote yield potential
(2024) Groß, Jonas; Müller, Torsten
Arable cropping systems are facing challenges imposed by climate change and are, at the same time, a tool to mitigate climate change. Soils are essential in securing yield potential and acting as a carbon sink. Recognizing small-scale site-specific differences in crop management and integrating cover crops, which provide ecosystem services such as carbon sequestration and weed suppression, are two approaches to climate-smart agriculture. To investigate site-specific soil heterogeneity, soil properties were analyzed in a field trial, measuring at three soil depths in 42 plots to determine their influence on yield measures. Soil organic carbon, silt, and clay contents in both topsoil and subsoil explained 45-46% of the variability in grain yield. Additionally, a positive correlation was found between increasing clay content in the topsoil and grain yield and tiller density. A higher clay content in the subsoil resulted in a decrease in grain yield. Soil organic carbon was identified as a soil property that positively influences yield and yield formation at any soil depth through multiple regressions and cluster analysis. Soil organic carbon is a critical soil measure that can significantly improve yield potential and can be manipulated by crop management practices like cover cropping. In a second field experiment, the impacts of increasing plant diversity of cover crop mixtures on rhizosphere carbon input and microbial utilization were investigated. A comparison was made between Mustard (Sinapis alba L.) planted as a sole crop and diversified cover crop mixtures of four (Mix4) or twelve (Mix12) species. A 13C-pulse labeling field experiment traced C transfer from shoots to roots to the soil microbial community. Mix 4 doubled the net CO2-C removal from the atmosphere, while Mix 12 more than tripled it, indicating that plant diversity positively impacts carbon cycling. This is reflected in higher atmospheric C uptake, higher transport rates to the rhizosphere, higher microbial incorporation, and longer residence time in the soil environment, improving the efficiency of C cycling in cropping systems. Root C-transfer could be identified as a fast pathway for C to reach soil C-compartments, but a substantial share of atmospheric C-catch comes from shoot biomass. In a third field experiment, the influence of species combination on shoot biomass formation was systematically assessed by investigating species interactions in dual cover crop mixtures and their competitiveness to suppress weeds before winter under different growing conditions. The shoot biomass share of a cover crop species in a dual-species mixture was found to be directly linked to its shoot biomass in a pure stand. Mustard and phacelia had similar effects on the shoot biomass production of the second species added to the mixture. Cruciferous species were more competitive against weeds than other cover crop species and could suppress weeds even when mixed with a less competitive partner. Weed suppression in mixtures with phacelia depended on the second component. Our results indicate that dual mixtures containing one competitive species reduce weed shoot biomass before winter, comparable to competitive pure stands. The research in this thesis shows that C content in the soil plays a crucial role in yield formation in arable cropping systems in Germany. Finally, the study has demonstrated that implementing cover crop mixtures can enhance soil C input and represent a valuable method for preserving yield potential. It was also shown that an intelligent combination of cover crop species can determine successful development and weed suppression.
Local and systemic metabolic adjustments to drought in maize: hydraulic redistribution in a split‐root system
(2022) Werner, Lena Maria; Hartwig, Roman Paul; Engel, Isabelle; Franzisky, Bastian Leander; Wienkoop, Stefanie; Brenner, Martin; Preiner, Julian; Repper, Dagmar; Hartung, Jens; Zörb, Christian; Wimmer, Monika Andrea
Background: It is yet unknown how maize plants respond to a partial root drying under conditions of a limited total water supply, and which adaptation mechanisms are triggered under these conditions. Aims: The aims of this study were to assess whether partial root drying results in distinguishable local and systemic physiological and metabolic drought responses, and whether compensatory water uptake and/or alteration of root architecture occurs under these conditions. Methods: Maize plants were grown in a split-root system. When plants were 20 days old, the treatments ‘well-watered’, ‘local drought’ and ‘full drought’ were established for a period of 10 days. Shoot length and gas exchange were measured non-destructively, root exudates were collected using a filter system and biomass, relative water content, osmolality and proline content were determined destructively at final harvest. Results: Local drought triggered stress responses such as reduced biomass, shoot length, relative water content and increased osmolality. Maintained root growth was systemically achieved by hydraulic redistribution rather than by altering root architecture. Local and systemic osmolyte adjustments contributed to this hydraulic redistribution. Conclusions: Both local and systemic metabolic responses helped the plants to induce hydraulic redistribution, enhance water availability and in consequence plant water relations. This resulted in a surprisingly well-maintained root growth even in the drought stressed root compartment.
Long-term breeding progress of yield, yield-related, and disease resistance traits in five cereal crops of German variety trials
(2021) Laidig, Friedrich; Feike, T.; Klocke, B.; Macholdt, J.; Miedaner, Thomas; Rentel, D.; Piepho, Hans-Peter
Plant breeding and improved crop management generated considerable progress in cereal performance over the last decades. Climate change, as well as the political and social demand for more environmentally friendly production, require ongoing breeding progress. This study quantified long-term trends for breeding progress and ageing effects of yield, yield-related traits, and disease resistance traits from German variety trials for five cereal crops with a broad spectrum of genotypes. The varieties were grown over a wide range of environmental conditions during 1988–2019 under two intensity levels, without (I1) and with (I2) fungicides and growth regulators. Breeding progress regarding yield increase was the highest in winter barley followed by winter rye hybrid and the lowest in winter rye population varieties. Yield gaps between I2 and I1 widened for barleys, while they shrank for the other crops. A notable decrease in stem stability became apparent in I1 in most crops, while for diseases generally a decrasing susceptibility was found, especially for mildew, brown rust, scald, and dwarf leaf rust. The reduction in disease susceptibility in I2 (treated) was considerably higher than in I1. Our results revealed that yield performance and disease resistance of varieties were subject to considerable ageing effects, reducing yield and increasing disease susceptibility. Nevertheless, we quantified notable achievements in breeding progress for most disease resistances. This study indicated an urgent and continues need for new improved varieties, not only to combat ageing effects and generate higher yield potential, but also to offset future reduction in plant protection intensity.

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