Changes in soil properties with long-term organic inputs due to distance from homestead and farm characteristics in southern Ethiopian farmlands

Open access via the Elsevier Agreement This original data was collected as part of the project ‘Alternative Carbon Investments in Ecosystems for Poverty Alleviation –below ground versus above ground opportunities for restoration of ecosystem services’ (ALTER), funded with support from the Ecosystem Services for Poverty Alleviation (ESPA) programme (grant no. NE/K010441/1). The analysis of the data and preparation of this paper was undertaken as part of the RALENTIR (Reducing land degradation and carbon loss from Ethiopia's soils to strengthen livelihoods and resilience) project, funded by GCRF (Global Challenges Research Fund) and University of Aberdeen (grant number ES/T003073/1).Peer reviewedPublisher PD

Rhizosphere-scale quantification of hydraulic and mechanical properties of soil impacted by root and seed exudates

Using rhizosphere-scale physical measurements we test the hypothesis that plant exudates gel together soil particles and on drying they enhance soil water repellency. Barley and maize root exudates were compared with chia seed exudate, a commonly used root exudate analogue. Sandy loam and clay loam soils were treated with root exudates at 0.46 and 4.6 mg exudate g-1 dry soil, and chia seed exudate at 0.046, 0.46, 0.92, 2.3 and 4.6 mg exudate g-1 dry soil. Soil hardness and modulus of elasticity were measured at -10 kPa matric potential using a 3 mm diameter spherical indenter. Water sorptivity and repellency index of air-dry soil were measured using a miniaturized infiltrometer device with a 1 mm tip radius. Soil hardness increased by 28% for barley root exudate, 62% for maize root exudate, and 86% for chia seed exudate at 4.6 mg g-1 concentration for sandy loam soil. For a clay loam soil, root exudates did not affect soil hardness, whereas chia seed exudate increased soil hardness by 48% at 4.6 mg g-1concentration. Soil water repellency increased by 48% for chia seed exudate and 23% for maize root exudate, but not for barley root exudate at 4.6 mg g-1 concentration for sandy loam soil. For clay loam soil, chia seed exudate increased water repellency by 45%, whereas root exudates did not affect water repellency at 4.6 mg g-1concentration. Water sorptivity and repellency were both correlated with hardness, presumably due to the combined influence of exudates on hydrological and mechanical properties of soils

Scaling of the reinforcement of soil slopes by living plants in a geotechnical centrifuge

The research described here in was funded by a EPSRC (EP/M020355/1) project in collaboration with the University of Dundee, the University of Southampton, the University of Aberdeen, the Durham University and The James Hutton Institute. The authors thank Professor Mike Humphreys (IBERS, Aberystwyth University) and Scotia seeds for providing seeds used in this study and Dr Gary Callon (University of Dundee) for arranging indoor growing area. The James Hutton Institute receives funding from the Scottish Government (Rural & Environmental Services & Analytical Services Division).Peer reviewedPublisher PD

Residues with varying decomposability interact differently with seed or root exudate compounds to affect the biophysical behaviour of soil

Plants have a large impact on the physical behaviour of soil, partly due to seed and root exudates that alter mineral:organic matter associations. In this study we explored how the decomposability of residues in soil interacts with seed or root exudate compounds to influence microbial respiration, mechanical behaviour and hydrological properties. Sandy loam and clay loam soils were amended at a rate of 40 t ha−1 with ground green barley (7.13 mg C g−1), barley straw (7.26 mg C g−1) or poultry manure (5.22 mg C g−1), and either chia seed exudate at 1.84 mg C g−1 soil or root exudate compounds at 14.4 mg C g−1 soil. On cores packed to 1.3 g cm−3, uniaxial compression, penetration resistance, water sorptivity, water retention and porosity were measured at time 0, after 14 days of incubation at 20 °C, and then after subjecting incubated soils to three cycles of wetting and drying to simulate weathering. These time increments and weathering were intended to simulate a newly germinated seed or tip of a root, through to a more mature system. Application of seed and root exudate increased carbon dioxide (CO2) emissions from 0.31 ± 0.01 to 15.11 ± 0.71 μg C-CO2 g soil−1 h−1 for the sandy loam soil and from 0.171 ± 0.01 to 10.56 ± 0.78 C-CO2 g soil−1 h−1 for the clay loam soil. There were large changes in soil physical properties caused by seed or root exudate amendment coupled with residues, their decomposition and weathering. After incubation and weathering, soils with added seed or root exudates and their interactions with organic residues were more mechanically stable, as measured by penetration resistance (22 to 58% increase) and compression index (25 to 43% decrease) compared to soils amended only with organic residue. Water sorptivity and porosity diminished with the addition of the exudate. Exudates in combination with organic residues better-protected soils against structural destabilization by increasing particle cementation, and decreasing rapid wetting and porosity