University of Hohenheim

About: University of Hohenheim is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Population & Soil water. The organization has 8585 authors who have published 16406 publications receiving 567377 citations.

Latitudinal differentiated water table control of carbon dioxide, methane and nitrous oxide fluxes from hydromorphic soils: feedbacks to climate change

Abstract: The possibility of carbon (C) being locked away from the atmosphere for millennia is given in hydromorphic soils. However, the water-table-dependent feedback from soil organic matter (SOM) decomposition to the climate system is less clear. At least three greenhouse gases are produced: carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). These gases show emission peaks at different water table positions and have different global warming potentials (GWP), for example a factor of 23 for CH4 and 296 for N2O as compared with the equivalent mass of CO2 on a 100-year time horizon. This review of available annual data on all three gases revealed that the radiative forcing effect of SOM decomposition is principally dictated by CO2 despite its low GWP. Anaerobic SOM decomposition generally has a lower potential feedback to the climatic system than aerobic SOM decomposition. Concrete values are constrained by a lack of data from tropical and subarctic regions. Furthermore, data on N2O and on plant effects are generally rare. However, there is a clear latitudinal differentiation for the GWP of soils under anaerobic conditions compared with aerobic conditions when looking at CO2 and CH4: in the tropical and temperate regions, the anaerobic GWP showed a range of 25‐60% of the aerobic value, but values varied between 80% and 110% in the boreal zone. Hence, particularly in the vulnerable boreal zone, the feedback from ecosystems to climate change will highly depend on plant responses to changing water tables at elevated temperatures.

Effects of mycorrhizae and phosphorus on growth and nutrient uptake of millet, cowpea and sorghum on a West African soil

Abstract: Despite numerous reports on the positive effects of vesicular arbuscular mycorrhizae (VAM) on plant growth in temperate soils, surprisingly little data exist on the importance of VAM for crop growth on acid sandy soils of West Africa. A pot experiment conducted with local genotypes of pearl millet (Pennisetum glaucum L.), sorghum (Sorghum bicolor L. Moench) and cowpea (Vigna unguiculata) with and without phosphorus (P) application in a sterilized sandy soil from a farmer's field in Niger showed large growth-enhancing effects of VAM. Phosphorus application led to 18- and 24-fold increases in pearl millet root and shoot dry matter independently of VAM, whereas the shoot and root dry matter of sorghum and cowpea depended largely on the interaction between P application and VAM. With P, VAM increased total uptake of P, K, Ca, Mg and Zn by 2·5- to 6-fold in sorghum and cowpea. On severely P deficient West African soils P application can lead to large increases in early root growth, a prerequisite for early mycorrhizal infection and a subsequent significant contribution of VAM to enhanced plant growth and nutrient uptake.

Hybrid wheat: quantitative genetic parameters and consequences for the design of breeding programs

Abstract: Commercial heterosis for grain yield is present in hybrid wheat but long-term competiveness of hybrid versus line breeding depends on the development of heterotic groups to improve hybrid prediction. Detailed knowledge of the amount of heterosis and quantitative genetic parameters are of paramount importance to assess the potential of hybrid breeding. Our objectives were to (1) examine the extent of midparent, better-parent and commercial heterosis in a vast population of 1,604 wheat (Triticum aestivum L.) hybrids and their parental elite inbred lines and (2) discuss the consequences of relevant quantitative parameters for the design of hybrid wheat breeding programs. Fifteen male lines were crossed in a factorial mating design with 120 female lines, resulting in 1,604 of the 1,800 potential single-cross hybrid combinations. The hybrids, their parents, and ten commercial wheat varieties were evaluated in multi-location field experiments for grain yield, plant height, heading time and susceptibility to frost, lodging, septoria tritici blotch, yellow rust, leaf rust, and powdery mildew at up to five locations. We observed that hybrids were superior to the mean of their parents for grain yield (10.7 %) and susceptibility to frost (−7.2 %), leaf rust (−8.4 %) and septoria tritici blotch (−9.3 %). Moreover, 69 hybrids significantly (P < 0.05) outyielded the best commercial inbred line variety underlining the potential of hybrid wheat breeding. The estimated quantitative genetic parameters suggest that the establishment of reciprocal recurrent selection programs is pivotal for a successful long-term hybrid wheat breeding.

15 – The Soil–Root Interface (Rhizosphere) in Relation to Mineral Nutrition

Abstract: The chapter explains how in the past decade much progress has been made to gain a better understanding of rhizosphere processes. As used for calcium and magnesium, a similar technique can be used to measure the accumulation of ions in the rhizosphere. Marked differences in redox potential in the rhizosphere occur between plants grown in aerated soils and those grown in submerged soils. The first part of the chapter describes the sources of nitrogen supply and rhizosphere pH, the nutritional status of plants and rhizosphere pH, and the redox potential and reducing processes. The section on rhizodeposition and root exudates covers rhizodeposition and root exudates separately and elaborates the actual process taking place in each case. Mucilage may have a diversity of biological functions, including protection of root apical zones from desiccation, lubrication of the root as it moves through the soil, ion uptake (facilitation or restriction), interaction with soil particles and improving the soil–root contact, especially in dry soil, and causing aggregation of soil in the rhizosphere. The main constituents of the low-molecular-weight root exudates are sugars, organic acids, amino acids, and phenolics. Noninfecting rhizosphere microorganisms cover root colonization and phytohormone precursors. Mycorrhizas have also been explained in detail. Mycorrhizal colonization per se, and any marked change in vesicular-arbuscular mycorrhiza (VAM) root colonization of field-grown plants have implications on soil testing and on simulation models for plant-available mineral nutrients, and phosphorus in particular.