Einfluss variierender Kaliumdüngung auf interpartikuläre Wechselwirkungen in unterschiedlich texturierten Böden

Die Zufuhr von Nährstoffen in Form von Dünger resultiert in einer Änderung der Ionenkonzentration in der Bodenlösung. Art und Menge der in der Bodenlösung enthaltenen Ionen beeinflussen das Gleichgewicht abstoßender und anziehender Kräfte zwischen Tonpartikeln. Monovalente Kationen wirken in Abhängigkeit ihrer Größe und damit der Dicke ihrer Hydrathülle mehr oder weniger dispergierend. Während eine gesteigerte Kaliumdüngung für Kulturpflanzen eine Verbesserung der Wachstumsbedingungen mit sich bringt, kann also die Bodenstruktur durch Zunahme dispergierend wirkender Ionen geschwächt werden. Zur Charakterisierung interpartikulärer Wechselwirkungen wurden an gestörtem luftgetrockneten sowie feldfeuchtem Bodenmaterial unterschiedlicher Textur Zetapotenzial- und Trübungsmessungen durchgeführt. Während das Zetapotenzial ein Maß für anziehende und abstoßende Kräfte darstellt, macht die Trübungsmessung eine Aussage über die Menge leicht dispergierbaren Tons in der Bodenprobe möglich. Für alle untersuchten Bodenmaterialien konnte bisher eine Zunahme abstoßender Kräfte bei mittlerer im Vergleich zu sowohl hoher als auch niedriger Düngeintensität festgestellt werden. Je tonhaltiger das Bodenmaterial ist, desto mehr leicht dispergierbarer Ton liegt erwartungsgemäß vor und desto besser stimmen die Ergebnisse der Trübungsmessung mit den gemessenen Zetapotenzialen überein; eine Zunahme abstoßender Kräfte führt dann zu einer Zunahme leicht dispergierbaren Tons. Die Ergebnisse deuten somit auf eine Schwächung der Bodenstruktur durch mittlere K-Düngungsintentitäten hin

Quantity of hydrophobic functional CH-groups - decisive for soil water repellency caused by digestate amendment

Anaerobic digestates are used as organic fertilizers; however, they are suspected to interfere negatively with soils.To investigate the relevance of the anaerobic digestates composition on potential wettability and contact angle of the soil, we mixed in a laboratory experiment 30 m³ ha-1 of anaerobic digesta-tes derived from mechanically pre-treated substrates from maizeand sugar beet with a homogenized Cambic Luvisol. Fourier trans-form infrared-spectra and diffuse reflectance infrared Fouriertransform-spectra of particle intact and finely ground soil-anaerobic digestates-mixtures were analyzed to determine the quantities of hydrophobic functional groups in the soil-anaerobic digestates-mixtures that are used here as an indicator for the potential hydrophobicity. The anaerobic digestates application increased the amount of hydrophobic functional groups of the mixtures and reduced the wettability of the soil. However, for intact particle samples an up to threefold higher amount of hydrophobic groups was found as compared to the finely ground ones, indicating a dilution effect of mechanical grinding on the effectivity of the organic matter that is presumably located as a coating on mineral soil particles. For the particle intact samples, the intensity of hydrophobic functional groups bands denoting hydrophobic brickstones in organic matter is indicative for the actual wettability of the soil-anaerobic digestates-mixtures

Quantity of Hydrophobic Functional CH-Groups – Decisive for Soil Water Repellency Caused by Digestate Amendment

Anaerobic digestates are used as organic fertilizers; however, they are suspected to interfere negatively with soils.To investigate the relevance of the anaerobic digestates composition on potential wettability and contact angle of the soil, we mixed in a laboratory experiment 30 m³ ha-1 of anaerobic digesta-tes derived from mechanically pre-treated substrates from maizeand sugar beet with a homogenized Cambic Luvisol. Fourier trans-form infrared-spectra and diffuse reflectance infrared Fouriertransform-spectra of particle intact and finely ground soil-anaerobic digestates-mixtures were analyzed to determine the quantities of hydrophobic functional groups in the soil-anaerobic digestates-mixtures that are used here as an indicator for the potential hydrophobicity. The anaerobic digestates application increased the amount of hydrophobic functional groups of the mixtures and reduced the wettability of the soil. However, for intact particle samples an up to threefold higher amount of hydrophobic groups was found as compared to the finely ground ones, indicating a dilution effect of mechanical grinding on the effectivity of the organic matter that is presumably located as a coating on mineral soil particles. For the particle intact samples, the intensity of hydrophobic functional groups bands denoting hydrophobic brickstones in organic matter is indicative for the actual wettability of the soil-anaerobic digestates-mixtures

Elastic and plastic soil deformation and its influence on emission of greenhouse gases

Abstract Soil management alters physical, chemical and biological soil properties. Stress application affects microbiological activity and habitats for microorganisms in the root zone and causes soil degradation. We hypothesized that stress application results in altered greenhouse gas emissions if soil strength is exceeded. In the experiments, soil management dependent greenhouse gas emissions of intact soil cores (no, reduced, conventional tillages) were determined using two experimental setups; CO2 emissions were determined with: a dynamic measurement system, and a static chamber method before and after a vertical soil stress had been applied. For the latter CH4 and N2O emissions were analyzed additionally. Stress dependent effects can be summed as follows: In the elastic deformation range microbiological activity increased in conventional tillage soil and decreased in reduced tillage and no tillage. Beyond the precompression stress a release of formerly protected soil organic carbon and an almost total loss of CH4 oxidizability occurred. Only swelling and shrinkage of no tillage and reduced tillage regenerated their microhabitat function. Thus, the direct link between soil strength and microbial activity can be applied as a marker for soil rigidity and the transition to new disequilibria concerning microbial activity and composition.</jats:p