Lithologic Control on the Scaling Properties of the First-Order Streams of Drainage Networks: A Monofractal Analysis

The movement of water through the landscape can be investigated at different scales. This study dealt with the interrelation between bedrock lithology and the geometry of the overlying drainage systems. Parameters of fractal analysis, such as fractal dimension and lacunarity, were used to measure and quantify this relationship. The interrelation between bedrock lithology and the geometry of the drainage systems has been widely studied in the last decades. The quantification of this linkage has not yet been clearly established. Several studies have selected river basins or regularly shaped areas as study units, assuming them to be lithologically homogeneous. This study considered irregular distributions of rock types, establishing areas of the soil map (1:25,000) with the same lithologic information as study units. The tectonic stability and the low climatic variability of the study region allowed effective investigation of the lithologic controls on the drainage networks developed on the plutonic rocks, the metamorphic rocks, and the sedimentary materials existing in the study area. To exclude the effect of multiple in- and outflows in the lithologically homogeneous units, we focused this study on the first-order streams of the drainage networks. The geometry of the hydrologic features was quantified through traditional metrics of fluvial geomorphology and scaling parameters of fractal analysis, such as the fractal dimension, the reference density, and the lacunarity. The results demonstrate the scale invariance of both the drainage networks and the set of first-order streams at the study scale and a relationship between scaling in the lithology and the drainage network

Drop impact behaviour on alternately hydrophobic and hydrophilic layered bead packs

A high level of water repellency in soils has an impact on soil hydrology, plant growth and soil erosion. Studies have been performed previously on model soils; consisting of close packed layers of glass spheres (140–400 μm in diameter), to mimic the behaviour of rain water on water repellent soils. In this study measurements were performed on multi-layered bead packs, to assess the interaction of water drops impacting layers consisting of different hydrophobic and hydrophilic layers. A high speed video camera was used to record the impact behaviour of water droplets on the bead packs focussing on the spreading of the droplet and the subsequent rebound behaviour of the droplet. Observations were made from the videos of the liquid marble effect on the droplet, whereby hydrophobic particles form a coating around the droplet, and how it differed depending on the arrangement of hydrophobic and hydrophilic layers within the bead pack. The droplet release height was varied in order to establish a relationship between impact velocity and the degree to which liquid marbling occurs, with higher impact speeds leading to a greater degree of liquid marbling. Measurements were also made to find the transition speeds between the three rebound conditions; rebound, pinning and fragmentation, showing an overall decrease in pinning velocity as the bead size increased

Soil-landscape model helps predict potassium supply in vineyards

The Lodi Winegrape District is one of the largest in California and encompasses a wide diversity of wine-grape varieties, production systems and soils, which complicates grape nutrient management To identify regions within this district that have similar nutrient-management needs, we are developing a soil-landscape model based on soil survey information. Our current model identifies five regions within the Lodi district with presumed relationships between soil properties and potassium-supplying ability. Region 1 has weakly developed, clay-rich soils in basin alluvium; region 2 has weakly developed, coarser-textured soils on recent alluvial fans, flood plains and stream terraces; region 3 has moderately developed soils on low terraces derived from granitic alluvium; region 4 has highly developed soils on high terraces derived from mixed alluvium; and region 5 has weakly developed soils formed on undulating volcanic terrain. Field and lab studies of soils in these regions show that our model is reasonable in concept, but that it must be fine-tuned to account for differing degrees of soil variability within each region in order to make realistic nutrient-management predictions

Model comparison and quantification of nitrous oxide emission and mitigation potential from maize and wheat fields at a global scale

This work was carried out by the International Maize and Wheat Improvement Center (CIMMYT) in collaboration with farmers and funded by the CGIAR research programs (CRPs) on Climate Change, Agriculture and Food Security (CCAFS). CCAFS' work is supported by CGIAR Fund Donors and through bilateral funding agreements. For details, please visit https://ccafs.cgiar.org/donors. The views expressed in this paper cannot be taken to reflect the official opinions of these organizations. The dataset associated with this manuscript will be available together with the supplementary materials of this manuscript.Peer reviewedPublisher PD

Evaluating the long-term effects of tillage systems on soil structural quality using visual assessment and classical methods

Current agricultural practices and their impacts on the sustainability of crop productioncan be evaluated by simple and reliable soil structure assessment tools. Thestudy was conducted to determine the effects of long-term(2006–2017) tillage systemson structural quality of a clayey soil using the visual evaluation of soil structure(VESS) and classical field and laboratory measurements. A field experiment withseven tillage systems, representing both traditional and conservation tillage methods,was conducted on a clayey soil in the Cukurova region, Turkey. Soil samplesfrom 0–10, 10–20 and 20–25 cm depths were analysed for mean weight diameter(MWD), porosity and organic carbon. Penetration resistance (PR) was determinedin each treatment plot. The VESS scores (<2) of upper 0–5 cm indicated a goodstructural quality for all tillage systems. The VESS scores were positively related toPR and MWD and negatively to macroporosity (MaP) and total porosity. In reducedand no-tillsystems, poorer soil structures were observed in subsurface layers wherefirm platy and angular blocky structures were defined. Mean VESS score (3.29) in20–25 cm depth where PR was 3.01 MPa under no-tillindicated a deterioration of soilstructural quality; thus, immediate physical interventions would be needed. LowerVESS scores and PR values under strategic tillage which was created by ploughinghalf of no-tillplots in November 2015 indicated successful correction of compactioncaused by long-termno-till.The results suggest that the VESS approach is sensitiveand useful in distinguishing compacted layers within the topsoil