Soil is alive - Experimental Dataset Collection - Willow pot experiment - Samples index and tests overview

The dataset contained in this repository describes the experimental results obtained from a set of multiple pot experiments run in the period March 31st 2024 to July 31st 2025, at the section for Geotechnics and Geology, Department of Environmental and Resource Engineering, Technical University of Denmark, as part of the Soil is alive (SoIA) project, lead by the principal investigator Associate Professor Irene Rocchi. The complete dataset contains an overview file with the list of specimens and test types performed (this file), selected images of samples, summary files of interpreted data for each test type, individual files with raw data for selected test types. This file contains a combined index of the samples tested and an overview of the test types. The first line reports an incremental integer to identify the columns as follows., followed by headers in the second line and units in the third line. All subsequent lines report data for each of the samples. Column 1 reports the ID of the sample indicating time elapsed in [days] from planting the willow stake into the soil to harvesting the shoot of the plant and perfom testing, followed by the main mechanical or hydraulic test performed on the sample (Pu for pullout, DS for direct shear, Pe for falling head test), followed by a sequential number, followed by N and/or A or B to avoid ID duplicates, followed by -T if roots specimens for tensile shear strength were taken from the sample. Columns 2 to 13 report information about the age of the sample and the testing performed. Column 2 reports the initial ID of the sample reported on the pots. Column 3 reports whether a photo of the sample taken before harvesting the plant's shoot and/or perfoming major testing is available, which are compiled in photos of samples at harvest. In these photos the ID on the pots is that in Column 2. Column 4 reports the time elapsed from planting the willow stake to harvesting the plant's shoot (i.e. the plant age), expressed in [days]. Column 5 reports the main test performed on the sample either mechanical (Pu for pullout or DS for direct shear), hydraulic (Pe for falling head test) or none. Column 6 reports the number of specimens taken for measuring the soil moisture, which are available as raw data in Soil moisture content. Column 7 reports the number of specimens taken for measuring the root tensile strength, which are available in Root tensile strength tests. The subsequent columns report the number of specimens taken for measuring total organic carbon (8), water extractable organic carbon (9), concentration of certain elements (10), DNA extraction (11), DNA sequencing(12), which are available in Microbiological markers and chemistry. Column 13 reports the number of sand agreggates collected for further analysis. When no specimen was taken the value is set to 0. N.R. indicates that no root specimen was available for sampling (i.e. for control pots or the sand as supplied), or that no water stable aggregate was found to be collected. Columns 14 to 22 report the dimensions of the pot and the dry masses (nominal and/or measured) of the sample's components, as well as the total weight at the time when the main mechanical and/or hydraulic tests were performed. Columns 14 and 15 report the internal diameter and length, respectively, of the PVC pipe used as a pot, as calculated based on a minimum of 6 measurements taken by a digital caliper, expressed in [millimeters]. Column 16 column reports the nominal distance between the top extremity of the pipe and the level corresponding to the sample's top surface, expressed in [millimeters], used during the sample preparation to achieve the target dry soil density. Column 17 reports the mass of the pot inclusive of the lid attached to its bottom extremity as a base, , expressed in [grams]. Column 18 reports the nominal mass of dry gravel, expressed in [grams], placed in the lid to provide water drainage (actual values were within 0,1g of the nominal value). Column 19 reports the nominal mass of dry sand added, expressed in [grams], (actual values were within 0,1g of the nominal value). Column 20 reports the total mass of the system in a dry state before planting the stake, expressed in [grams], consisting of the mass of the pot, lid, gravel, geotextile, sand. Discrepancies with the sum of the previous values arise from using two different scales. Column 21 reports the total mass of the system in a moist state before harvesting the plant, expressed in [grams], consisting of the mass of the pot, lid, gravel, geotextile, sand, plant inclusive of shoot root and stake, and water. The additional weight compared to column 20 arises from presence of water and growth of the plant. Column 22 reports the distance between the top extremity of the pipe and the level corresponding to the sample's top surface, expressed in [millimeters], as calculated from the average of 6-10 measurements taken with a steel ruler along the inner perimeter of the pot. Differences from Column 14 arise from compaction of the sand following watering, and changes in density induced by the plant growth. Columns 23 to 27 report the mass and dimensions of the water-stable aggregates, if formed during the plant's growth. Column 23 reports the total mass of aggregates retained on a 1.4 mm mesh following wet sieving, expressed in [grams]. Columns 24 and 25 report the minimum and maximum dimensions of the smallest and largest aggregate, respectively, found within a sample, expressed in [micrometers]. Column 26 and 27 report the average dimension and standard deviation of all the aggregates measured. N.R. stands for not relevant when no water-stable aggregate was observed, also expressed in [micrometers]. Dimensions were taken using a built-in measuring function of the optical microscope used. Columns 28 to 33 report characteristics of the plant. Column 28 the plant species, which was controlled to be clone Inger, Salix triandra × S.viminalis except for a few exceptions. N.R. indicates that the sample is a control and therefore no plant is present. Column 29 reports the status of the plant at the time of harvest, which can be verified in the photos of samples at harvest. Column 30 reports the dry mass of the shoot after cutting all branches from the stake and collecting fallen leaves, following oven drying at 60 degrees Celsius for 48 hours, expressed in [grams]. Column 31 reports the height of the shoot measured by a tape meter from the ground level to the tip of the longest branch when gently straightened by hand, expressed in [mm]. Column 32 reports the average diameter of the stake as measured by an average of minimum 4 measurements by digital calliper. Column 33 reports the dry mass of the stake following oven drying at 60 degrees Celsius for 48 hours. N.R. stands for not relevant, in case of control pots. N.D. stands for not determined and indicates that the measurement was not performed. Columns 34 to 38 report the roots characteristics. Column 34 reports the root dry mass following oven drying at 60 degrees Celsius for 48 hours. When samples were taken for tensile strength testing the moist mass of the specimens taken was measured and its dry mass estimated based on the moisture content of the roots measured on the main sample, roots were tapped dry with a paper tissue after rinsing them from loose sand particle with water. In case of samples were water-stable aggregates formed around roots, the root mass was corrected measuring the difference in dry mass of the aggregates before and after grinding them and separating the roots by decantation. Column 36 reports the number of primary roots stemming from the stake. Column 37 reports the average angle between the roots as branching out from the shoot and a downwards oriented vertical axis, as measured by a protractor on a 360 degrees scale. The angles are reported as absolute values so that two roots branching symmetrically from the stake result in the same angle. Column 38 reports the standard deviation among the angles measured for all primary roots in a plant, which are available in Root architecture. N.R. stands for not relevant, in case of control pots. N.D. stands for not determined and indicates that the measurement was not performed. Columns 39 and 40 summarise the pullout tests as obtained through a universal testing machine. Columns 39 and 40 report the maximum pullout force, expressed in [Newton], and corresponding displacement, expressed in [millimeters], respectively The raw data limited to samples where pullout tests were performed are available in Pullout tests. For all other samples, N.R. stands for not relevant. Columns 41 to 43 columns summarise the results of falling head tests. Column 41 reports the saturated hydraulic conductivity in [meter per second], as measured by falling head tests on samples saturated by capillarity raising the water level from their based to the top sand surface in an external container ahead of testing. Columns 42 and 43 report the distance from the top of the pot to the sand level before and after the falling head test, respectively, expressed in [mm], as calculated based on the average of 6-10 readings taken with a metal ruler. The raw data limited to the samples where falling head tests were performed is available in Falling head tests. For all other samples, N.R. stands for not relevant. Columns 44 to 49 summarise the results for direct shear tests obtained with a customary setup that applied horizontal displacement directly to the two halves of the pot once the tape connecting them was removed and a sub-millimeter gap was formed between them. Column 44 reports the soil moisture, expressed in [percentage], measured after testing at the mid section where shear occured, based on an average of three specimens ovendried at 105 degrees Celsius for at least 24 hours, which are available as raw data in Soil moisture content. Column 45 reports the force at failure measured during direct shear testing, expressed in [kiloNewton] and Column 46 the corresponding displacement at failure, expressed in [millimeters]. Failure was defined as the maximum stress calculated considering area correction, reported in Column 47 in [kiloPascal], unless this was at a significantly different displacement compared to that corresponding to the peak force, which was limited to few cases where strain softening behaviour took place at small displacement and with relatively low forces. In such case the stress at failure was calculated for the maximum force measured. Column 48 reports the stress at the failure displacement assuming constant area, expressed in [kiloPascal]. The raw data limited to the samples where direct shear tests were performed is available in Direct shear tests. For all other samples, N.R. stands for not relevant. Column 49 indicates whether datalogging during the test was reliable.