scholarly journals Pedotransfer functions to estimate water retention parameters of soils in northeastern Brazil

2013 ◽  
Vol 37 (2) ◽  
pp. 379-391 ◽  
Author(s):  
Alexandre Hugo Cezar Barros ◽  
Quirijn de Jong van Lier ◽  
Aline de Holanda Nunes Maia ◽  
Fábio Vale Scarpare
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Particle Size Distribution ◽  
Water Content ◽  
Size Distribution ◽  
Water Retention ◽  
Northeastern Brazil ◽  
Pedotransfer Functions ◽  
Residual Water ◽  
Specific Pressure

Pedotransfer functions (PTF) were developed to estimate the parameters (α, n, θr and θs) of the van Genuchten model (1980) to describe soil water retention curves. The data came from various sources, mainly from studies conducted by universities in Northeast Brazil, by the Brazilian Agricultural Research Corporation (Embrapa) and by a corporation for the development of the São Francisco and Parnaíba river basins (Codevasf), totaling 786 retention curves, which were divided into two data sets: 85 % for the development of PTFs, and 15 % for testing and validation, considered independent data. Aside from the development of general PTFs for all soils together, specific PTFs were developed for the soil classes Ultisols, Oxisols, Entisols, and Alfisols by multiple regression techniques, using a stepwise procedure (forward and backward) to select the best predictors. Two types of PTFs were developed: the first included all predictors (soil density, proportions of sand, silt, clay, and organic matter), and the second only the proportions of sand, silt and clay. The evaluation of adequacy of the PTFs was based on the correlation coefficient (R) and Willmott index (d). To evaluate the PTF for the moisture content at specific pressure heads, we used the root mean square error (RMSE). The PTF-predicted retention curve is relatively poor, except for the residual water content. The inclusion of organic matter as a PTF predictor improved the prediction of parameter a of van Genuchten. The performance of soil-class-specific PTFs was not better than of the general PTF. Except for the water content of saturated soil estimated by particle size distribution, the tested models for water content prediction at specific pressure heads proved satisfactory. Predictions of water content at pressure heads more negative than -0.6 m, using a PTF considering particle size distribution, are only slightly lower than those obtained by PTFs including bulk density and organic matter content.

The relations between soil water retention characteristics, particle size distributions, bulk densities and calcium carbonate contents for Danish soils

2005 ◽  
Vol 36 (3) ◽  
pp. 235-244 ◽  
Author(s):  
Niels Henrik Jensen ◽  
Thomas Balstrøm ◽  
Henrik Breuning-Madsen
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Particle Size Distribution ◽  
Water Content ◽  
Bulk Density ◽  
Soil Water ◽  
Soil Water Content ◽  
Pressure Head ◽  
Pedotransfer Functions ◽  
Regression Equations

A database containing about 800 soil profiles located in a 7-km grid covering Denmark has been used to develop a set of regression equations of soil water content at pressure heads −1, −10, −100 and −1500 kPa versus particle size distribution, organic matter, CaCO3 and bulk density. One purpose was to elaborate equations based on soil parameters available in the Danish Soil Classification's texture database of particle size distribution and organic matter. It was also tested to see if inclusion of bulk density or CaCO3 content (in CaCO3-containing samples) as predictors or grouping in surface and subsurface horizons or textural classes improved the regression equations. Compared to existing Danish equations based on much fewer observations the accuracies of the new equations were better. The equations also predicted the soil water content at the measured pressure heads more accurately than the pedotransfer functions developed in HYPRES (Hydraulic Properties of European Soils). Introducing bulk density as a predictor improved the equation for the pressure head of −1 kPa but not for the lower ones. The grouping of data sets in surface and subsurface horizons or in textural classes did not improve the equations. Based on the equations a set of van Genuchten parameters for soil types in the Danish Soil Classification was elaborated. The prediction of soil water content, especially at pressure head −1 kPa, is more accurate using these van Genuchten parameters than using the pedotransfer functions developed in relation to the HYPRES database from a broad range of European soils.

scholarly journals Predicting the soil water retention curve from the particle size distribution based on a pore space geometry containing slit-shaped spaces

2018 ◽  
Vol 22 (9) ◽  
pp. 4621-4632
Author(s):  
Chen-Chao Chang ◽  
Dong-Hui Cheng
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Water Content ◽  
Size Distribution ◽  
Soil Water ◽  
Water Retention ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve

Abstract. Traditional models employed to predict the soil water retention curve (SWRC) from the particle size distribution (PSD) always underestimate the water content in the dry range of the SWRC. Using the measured physical parameters of 48 soil samples from the UNSODA unsaturated soil hydraulic property database, these errors were proven to originate from an inaccurate estimation of the pore size distribution. A method was therefore proposed to improve the estimation of the water content at high suction heads using a pore model comprising a circle-shaped central pore connected to slit-shaped spaces. In this model, the pore volume fraction of the minimum pore diameter range and the corresponding water content were accordingly increased. The predicted SWRCs using the improved method reasonably approximated the measured SWRCs, which were more accurate than those obtained using the traditional method and the scaling approach in the dry range of the SWRC.

scholarly journals Physical and Hydraulic Properties of Commercial Pine-bark Substrate Products Used in Production of Containerized Crops

HortScience ◽  
2018 ◽  
Vol 53 (12) ◽  
pp. 1883-1890 ◽  
Author(s):  
James E. Altland ◽  
James S. Owen ◽  
Brian E. Jackson ◽  
Jeb S. Fields
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Water Content ◽  
Size Distribution ◽  
Hydraulic Properties ◽  
Fine Fraction ◽  
Total Porosity ◽  
Pine Bark ◽  
Residual Water ◽  
Eastern United States

Pine bark is the primary constituent of nursery container media (i.e., soilless substrate) in the eastern United States. Pine bark physical and hydraulic properties vary depending on the supplier due to source (e.g., lumber mill type) or methods of additional processing or aging. Pine bark can be processed via hammer milling or grinding before or after being aged from ≤1 month (fresh) to ≥6 month (aged). Additionally, bark is commonly amended with sand to alter physical properties and increase bulk density (Db). Information is limited on physical or hydraulic differences of bark between varying sources or the effect of sand amendments. Pine bark physical and hydraulic properties from six commercial sources were compared as a function of age and amendment with sand. Aging bark, alone, had little effect on total porosity (TP), which remained at ≈80.5% (by volume). However, aging pine bark from ≤1 to ≥6 months shifted particle size from the coarse (>2 mm) to fine fraction (<0.5 mm), which increased container capacity (CC) 21.4% and decreased air space (AS) by 17.2% (by volume) regardless of source. The addition of sand to the substrate had a similar effect on particle size distribution to that of aging, increasing CC and Db while decreasing AS. Total porosity decreased with the addition of sand. The magnitude of change in TP, AS, CC, and Db from a nonamended pine bark substrate was greater with fine vs. coarse sand and varied by bark source. When comparing hydrological properties across three pine bark sources, readily available water content was unaffected; however, moisture characteristic curves (MCC) differed due to particle size distribution affecting the residual water content and subsequent shift from gravitational to either capillary or hygroscopic water. Similarly, hydraulic conductivity (i.e., ability to transfer water within the container) decreased with increasing particle size.

Deriving point and parametric pedotransfer functions of some gypsiferous soils

Soil Research ◽  
2008 ◽  
Vol 46 (3) ◽  
pp. 219 ◽  
Author(s):  
Mehdi Homaee ◽  
Ahmad Farrokhian Firouzi
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Bulk Density ◽  
Size Distribution ◽  
Water Retention ◽  
Pedotransfer Functions ◽  
Water Retention Curve ◽  
Geometric Standard Deviation ◽  
Retention Curve ◽  
Gypsum Content

Parametric description of the soil water retention curve as well as the hydraulic conductivity curve is needed for modelling water movement and solute transport in the vadose zone. The objective of this study was to derive pedotransfer functions (PTFs) to predict the water retention curve and the van Genuchten and the van Genuchten–Mualem parameters of some gypsiferous soils. Consequently, 185 gypsiferous soil samples were collected and their physical properties were measured. The particle size distribution was determined in 2 steps: (i) with gypsum, by covering the particles with barium sulphate; (ii) without gypsum, using the hydrometry method. The easily obtainable variables were grouped as (1) particle size distribution, bulk density, and gypsum content; and (2) bulk density, gypsum content, geometric mean, and geometric standard deviation of the particle diameter. Stepwise multiple linear regression method was used to derive the PTFs. Two types of parametric and point functions were derived using these variables. The first group of variables predicted water retention and the van Genuchten and van Genuchten–Mualem parameters better than the second group. The gypsum content appeared to be the second dominant parameter for predicting water retention at 0, −330, −1000, −3000, −5000, and −15 000 cm. The derived PTFs were compared with the Rosetta database as independent dataset. The validity test indicated that in order to predict the hydraulic properties of gypsiferous soils the derived PTFs are more accurate than what can be obtained from the Rosetta database. Removal of gypsum increased the water retention at pressure heads of 0, –100, –330, –1000, –3000, –5000, and –15 000 cm (P < 0.01). The results also indicated that hydraulic parameters were different for the same soil with and without gypsum.

Impact of Biochar on Water Holding Capacity of Two Chinese Agricultural Soil

2014 ◽  
Vol 941-944 ◽  
pp. 952-955 ◽  
Author(s):  
Dao Yuan Wang ◽  
Deng Hua Yan ◽  
Xin Shan Song ◽  
Hao Wang
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Soil Type ◽  
Agricultural Soil ◽  
Water Retention ◽  
Water Holding Capacity ◽  
Walnut Shell ◽  
Retention Characteristics ◽  
Water Holding

Adding biochar to agricultural soil has been suggested as an approach to enhance soil carbon sequestration. Biochar has also been used as a soil amendment to reduce nutrient leaching, reduce soil acidity and improve water holding capacity. Walnut shells and woody material are waste products of orchards that are cheap, carbon-rich and good feedstock for production of biochar. The effectiveness of biochar as an amendment varies considerably as a function of its feedstock, temperature during pyrolysis, the biochar dose to soil, and mechanical composition. Biochar was produced from pyrolysis of walnut shell at 900 °C and soft wood at 600 to 700 °C. We measured the effect of these different parameters in two types of agricultural soil in Jilin and Beijing, China, a silt clay loam and a sandy loam, on the soils’ particle size distribution and water retention characteristics. Biochars with two different doses were applied to each soil type. Soil field capacity and permanent wilting point were measured using a pressure plate extractor for each combination of biochar and soil type. The results show that the effect of biochar amendment on soil water retention characteristics depend primarily on soil particle size distribution and surface characteristics of biochar. High surface area biochar can help raise the water holding capacity of sandy soil.

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