Development of Unstable Flow and Reduced Hydraulic Conductivity due to Water Repellence and Restricted Drainage

2012 ◽  
Vol 11 (4) ◽  
pp. vzj2011.0099 ◽  
Author(s):  
Marcus Hardie ◽  
Markus Deurer ◽  
Richard B. Doyle ◽  
Shaun Lisson ◽  
William E. Cotching ◽  
...  
Soil Research ◽  
1980 ◽  
Vol 18 (3) ◽  
pp. 299 ◽  
Author(s):  
DA Mcghie

Severe erosion in the Great Southern area of Western Australia has long been associated with the land class known locally as the 'mallet hill'. This association was confirmed by means of an aerial photograph survey of a representative part of the area. Use of a recycling rainfall simulator showed the mallet hill land class to yield far higher runoff than any of four adjacent upper landscape surfaces. Several factors were thought to contribute to the higher runoff from the mallet hill surface. Among these were steeper slopes, a heavier texture and water repellence of the surface soil which varied from severe in the virgin and freshly cleared state to slight or non existent in soils, which had been cleared for many years. No assessment of the relative contributions of the various factors was made, although it appeared likely that water repellence would be more important in the early years after clearing. Removal of the topsoil by sheet erosion would increase the importance of the low hydraulic conductivity of the heavy-textured subsoil in causing runoff.


Soil Research ◽  
1993 ◽  
Vol 31 (1) ◽  
pp. 13 ◽  
Author(s):  
KY Chan ◽  
DP Heenan

Differences in surface soil hydraulic properties after 10 years of different tillage (direct drilled (DD) versus conventional tillage (CT)) and stubble management practices (stubble retained (SR) versus stubble burnt (SB)) were measured in a lupin/wheat rotation on a red earth at Wagga Wagga, NSW. Sorptivity and hydraulic conductivity measurements using a disk permeameter under negative matric potential (-40 mrn) was complicated by water repellence found under SR as compared to SB treatments. Using water, K-40 of SR/DD was only 40% of SB/CT. However, using a wetting agent instead of water increased K-40 of SR/DD by >400% but did not significantly change that of SB/CT such that K-40 was similar for the two treatments. Despite similar bulk density, hydraulic conductivity under ponded infiltration of SR/DD was 4.1 times that of SB/CT. Differences in hydraulic conductivity between -40 mm and under ponded conditions suggest the presence of significantly more transmitting macropores >1.5 mm in diameter under direct drilling. Dye infiltration results indicated that tillage significantly reduced the number of transmitting macropores (>1 mm) even though the total number of macropores remained similar amongst the different treatments. 65% of the macropores were transmitting under SR/DD compared to 1% under SB/CT. A significant correlation (r2=0.82**) was found between transmitting pores (>1.0 mm) and the earthworm population. Tillage but not stubble burning significantly reduced earthworm population.


2019 ◽  
pp. 27-34

The effect of different rates of poultry manure application on water characteris- tics of Oforola soils was studied. The different poultry manure rates were 0, 10, 20, and 30 t/ha, while the soil properties studied were particle size distribution, bulk density, porosity, organic matter, saturated hydraulic conductivity, volumet- ric water content, volumetric infiltration rate, sorptivity and water repellence in- dex. Data were subjected to multiple correlation (p = 0.05 and p = 0.01) and anal- ysis of variance (p = 0.05) using RCBD. The results show that the particle size distribution and water repellence index did not differ significantly among the different treatment rates. Soil porosity and organic matter were observed to in- crease with increasing treatment rate but were not significantly influenced by the different treatment rates. Bulk density was significantly influenced in the 30 t/ha treated plot. Both the saturated hydraulic conductivity and volumetric water con- tent were significantly influenced in the 20 and 30 t/ha treated plots, while both volumetric infiltration rate and sorptivity were significantly influenced in all the treated plots. The result of the correlation analysis showed that the treatments had positive influence (p = 0.01) on porosity (r = 0.982), organic matter (r = 0.967) and volumetric water content (r = 0.976) but negatively influenced (p = 0.01) bulk density (r = -0.982), saturated hydraulic conductivity (r = -0.989), volumet- ric infiltration rate (r = -0.990) and sorptivity (r = -0.994). Also, the treatments correlated positively but non-significantly with water repellence index (r value), which correlated negatively and significantly with the percent clay content (r value). Based on the findings, a further study is recommended to establish a standard and beneficial poultry manure rate that would enhance soil water char- acteristics for sustainable productivity. o improve the soil constraints to maintain and sustain the productivity of the soils.


2015 ◽  
Vol 9 (3) ◽  
pp. 2487-2502 ◽  
Author(s):  
Igor V. Lebed

Scenario of appearance and development of instability in problem of a flow around a solid sphere at rest is discussed. The scenario was created by solutions to the multimoment hydrodynamics equations, which were applied to investigate the unstable phenomena. These solutions allow interpreting Stokes flow, periodic pulsations of the recirculating zone in the wake behind the sphere, the phenomenon of vortex shedding observed experimentally. In accordance with the scenario, system loses its stability when entropy outflow through surface confining the system cannot be compensated by entropy produced within the system. The system does not find a new stable position after losing its stability, that is, the system remains further unstable. As Reynolds number grows, one unstable flow regime is replaced by another. The replacement is governed tendency of the system to discover fastest path to depart from the state of statistical equilibrium. This striving, however, does not lead the system to disintegration. Periodically, reverse solutions to the multimoment hydrodynamics equations change the nature of evolution and guide the unstable system in a highly unlikely direction. In case of unstable system, unlikely path meets the direction of approaching the state of statistical equilibrium. Such behavior of the system contradicts the scenario created by solutions to the classic hydrodynamics equations. Unstable solutions to the classic hydrodynamics equations are not fairly prolonged along time to interpret experiment. Stable solutions satisfactorily reproduce all observed stable medium states. As Reynolds number grows one stable solution is replaced by another. They are, however, incapable of reproducing any of unstable regimes recorded experimentally. In particular, stable solutions to the classic hydrodynamics equations cannot put anything in correspondence to any of observed vortex shedding modes. In accordance with our interpretation, the reason for this isthe classic hydrodynamics equations themselves.


2020 ◽  
Vol 53 (2) ◽  
Author(s):  
Guanglong Zhu ◽  
Lifeng Gu ◽  
Yu Shi ◽  
Huize Chen ◽  
Yuqian Liu ◽  
...  

Soil Horizons ◽  
1986 ◽  
Vol 27 (2) ◽  
pp. 32
Author(s):  
Thomas A. Peragallo ◽  
Steven P. Schertzer

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