Field changes in germination requirements: effect of natural rainfall on potential germination speed and light requirement of Stylosanthes humilis, Stylosanthes hamata and Digitaria ciliaris

1984 ◽  
Vol 35 (6) ◽  
pp. 807 ◽  
Author(s):  
GM McKeon
Keyword(s):  
Surface Soil ◽  
Soil Surface ◽  
Light Requirement ◽  
Rainfall Events ◽  
Surface Moisture ◽  
Natural Rainfall ◽  
Stylosanthes Hamata ◽  
Stylosanthes Humilis ◽  
Germination Speed ◽  
Field Germination

The effect of isolated rainfall events on germination speed and light requirement was studied for different seed populations of Stylosanthes humilis, Stylosanthes hamata and Digitaria ciliaris. Initial germination, measured as the proportion of seeds germinating within 12 or 18 h under optimal laboratory conditions, was an important determinant of field germination where surface soil moisture is available for only short durations (12-18 h). Seeds were placed on the soil surface prior to rainfall, usually in the late afternoon, were resampled the following day when dry, and then stored in the laboratory before standard germination tests. The seed populations were exposed to 20 different rainfall events. Compared with unexposed seeds the seeds of all species germinated faster after exposure to rainfall, even a few mm, provided the rainfall was insufficient to cause field germination, e.g. germination of S. humilis increased from 46 to 70% in 12 h. Field germination was common in S. humilis, but little field germination of S. hamata and D. ciliaris occurred because of their slow germination. Initial germination of resampled seed was correlated with duration of surface moisture, whether this was received over one or two rainfall cycles. Seeds of S. hamata and S. humilis with the greatest increases in initial germination had a shorter imbibition time. The light requirement for rapid germination of S. humilis was not changed by rainfall, but the light-requiring fraction of D. ciliaris was reduced by exposure to rainfall (the reduction was positively correlated with duration of surface moisture) and high temperature (>50�C).

The nature of the perennial response in Mediterranean grasses. I. Water relations and summer survival in Phalaris

1968 ◽  
Vol 19 (3) ◽  
pp. 381 ◽  
Author(s):  
JR McWilliam ◽  
PJ Kramer
Keyword(s):  
Surface Soil ◽  
Perennial Grass ◽  
Soil Surface ◽  
Water Source ◽  
Perennial Grasses ◽  
Natural Conditions ◽  
Deep Roots ◽  
Surface Moisture ◽  
Summer Stress ◽  
Controlled Environments

An important factor in the survival of Phalaris tuberosa, a typical Mediterranean perennial grass, is the ability of its deep root system to supply water during the summer to the dormant culms at the soil surface. This behaviour contrasts with that of the related annual P. minor, which is unable to exploit subsoil moisture, and dies as soon as the surface moisture is exhausted. The volume of water supplied by the perennial roots is sufficient to offset transpiration losses and maintain a favourable water balance in the dormant culms during the summer stress. The importance of this water source for survival is indicated by the death of plants whenever this supply is interrupted by severing deep roots. In field soils under drought conditions roots of the perennial have been followed to a depth of 7 ft in subsoil containing available moisture. The large metaxylem vessels and heavily suberized endodermis which are a feature of these roots suggest that they are well adapted to transport water up through the dry surface soil to the base of the dormant culms. The culms also show typical xerophytic characteristics which help to minimize water loss during the summer, and maintain favourable conditions for the survival of the dormant buds which develop at the basal nodes. These conclusions concerning the survival of the perennial have been drawn from plants growing under natural conditions, and also from more detailed studies under controlled environments. They appear to be of general significance for the perennial grasses adapted to the drier Mediterranean environments and form the basis of the perennial response found in this group.

MEASUREMENT OF NEAR-SURFACE SOIL MOISTURE WITH A HYDROGENOUSLY SHIELDED NEUTRON PROBE

1988 ◽  
Vol 68 (1) ◽  
pp. 171-176 ◽  
Author(s):  
D. S. CHANASYK ◽  
M. A. NAETH
Keyword(s):  
Soil Moisture ◽  
Key Words ◽  
Surface Soil ◽  
Ground Surface ◽  
Soil Surface ◽  
Surface Soil Moisture ◽  
Near Surface ◽  
Surface Moisture ◽  
Neutron Probe

Numerous techniques for measuring near-surface soil moisture with a neutron probe have been reported. Placing the neutron probe horizontally on the ground surface within a hydrogenous shield has been discussed theoretically, but field adaptations have not. Such a shield was designed and used, yielding measurements of near-surface soil moisture quickly and accurately. Key words: Neutron probe, soil surface moisture, calibration

scholarly journals Effect of tillage, slope, and rainfall on soil surface microtopography quantified by geostatistical and fractal indices during sheet erosion

2020 ◽  
Vol 12 (1) ◽  
pp. 232-241
Author(s):  
Na Ta ◽  
Chutian Zhang ◽  
Hongru Ding ◽  
Qingfeng Zhang
Keyword(s):  
Surface Roughness ◽  
Fractal Dimension ◽  
Soil Surface ◽  
Rainfall Events ◽  
Tillage Practices ◽  
Surface Microtopography ◽  
Artificial Rainfall ◽  
Soil Surface Roughness ◽  
The Difference ◽  
Sheet Erosion

AbstractTillage and slope will influence soil surface roughness that changes during rainfall events. This study tests this effect under controlled conditions quantified by geostatistical and fractal indices. When four commonly adopted tillage practices, namely, artificial backhoe (AB), artificial digging (AD), contour tillage (CT), and linear slope (CK), were prepared on soil surfaces at 2 × 1 × 0.5 m soil pans at 5°, 10°, or 20° slope gradients, artificial rainfall with an intensity of 60 or 90 mm h−1 was applied to it. Measurements of the difference in elevation points of the surface profiles were taken before rainfall and after rainfall events for sheet erosion. Tillage practices had a relationship with fractal indices that the surface treated with CT exhibited the biggest fractal dimension D value, followed by the surfaces AD, AB, and CK. Surfaces under a stronger rainfall tended to have a greater D value. Tillage treatments affected anisotropy differently and the surface CT had the strongest effect on anisotropy, followed by the surfaces AD, AB, and CK. A steeper surface would have less effect on anisotropy. Since the surface CT had the strongest effect on spatial variability or the weakest spatial autocorrelation, it had the smallest effect on runoff and sediment yield. Therefore, tillage CT could make a better tillage practice of conserving water and soil. Simultaneously, changes in semivariogram and fractal parameters for surface roughness were examined and evaluated. Fractal parameter – crossover length l – is more sensitive than fractal dimension D to rainfall action to describe vertical differences in soil surface roughness evolution.

Estimating storm erosion with a rainfall simulator

1997 ◽  
Vol 77 (4) ◽  
pp. 669-676 ◽  
Author(s):  
S. C. Nolan ◽  
L. J. P. van Vliet ◽  
T. W. Goddard ◽  
T. K. Flesch
Keyword(s):  
Soil Loss ◽  
Conventional Tillage ◽  
Reduced Tillage ◽  
Natural Soil ◽  
Rainfall Erosivity ◽  
Slope Length ◽  
Rainfall Simulator ◽  
Rainfall Events ◽  
Plot Size ◽  
Natural Rainfall

Interpreting soil loss from rainfall simulators is complicated by the uncertain relationship between simulated and natural rainstorms. Our objective was to develop and test a method for estimating soil loss from natural rainfall using a portable rainfall simulator (1 m2 plot size). Soil loss from 12 rainstorms was measured on 144-m2 plots with barley residue in conventional tillage (CT), reduced tillage (RT) and zero tillage (ZT) conditions. A corresponding "simulated" soil loss was calculated by matching the simulator erosivity to each storm's erosivity. High (140 mm h−1) and low (60 mm h−1) simulation intensities were examined. The best agreement between simulated and natural soil loss occurred using the low intensity, after making three adjustments. The first was to compensate for the 38% lower kinetic energy of the simulator compared with natural rain. The second was for the smaller slope length of the simulator plot. The third was to begin calculating simulator erosivity only after runoff began. After these adjustments, the simulated soil loss over all storms was 99% of the natural soil loss for CT, 112% for RT and 95% for ZT. Our results show that rainfall simulators can successfully estimate soil loss from natural rainfall events. Key words: Natural rainfall events, simulated rainfall, erosivity, tillage

Using soil surface gray level to determine surface soil water content

2010 ◽  
Vol 53 (10) ◽  
pp. 1527-1532 ◽  
Author(s):  
YuanJun Zhu ◽  
YunQiang Wang ◽  
MingAn Shao
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Surface Soil ◽  
Soil Surface ◽  
Gray Level

Mapping of tank silt application using Sentinel-2 images over the Berambadi catchment (India).

2021 ◽  
Author(s):  
Cécile Gomez ◽  
Dharumarajan Subramanian ◽  
Philippe Lagacherie ◽  
Jean Riotte ◽  
Sylvain Ferrant ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Soil Properties ◽  
South India ◽  
Surface Soil ◽  
Soil Surface ◽  
Calibration Data ◽  
Surface Soil Moisture ◽  
Soil Color ◽  
Color Changes ◽  
Sentinel 2

<p>Mapping soil properties is becoming more and more challenging due to the increase in anthropogenic modification of the landscape, calling for new methods to identify these changes. A striking example of anthropogenic modifications of soil properties is the widespread practice in South India of applying large quantities of silt from dry river dams (or “tanks”) to agricultural fields. Whereas several studies have demonstrated the interest of tank silt for soil fertility, no assessment of the actual extent of this age-old traditional practice exists. Over pedological contexts characterized by Vertisol, Ferralsols and Chromic Luvisols in sub-humid and semi-arid Tropical climate, this practice is characterized by an application of black-colored tank silt providing from Vertisol, to red-colored soils such as Ferralsols. The objective of this work was to evaluate the usefulness of Sentinel-2 images for mapping tank silt applications, hypothesizing that observed changes in soil surface color can be a proxy for tank silt application.</p><p>We used data collected in a cultivated watershed (Berambadi, Karnataka state, South India) including 217 soil surface samples characterized in terms of Munsell color. We used two Sentinel-2 images acquired on February 2017 and April 2017. The surface soil color over each Sentinel-2 image was classified into two-class (“Black” and “Red” soils). A change of soil color from “Red” in February 2017 to “Black” in April 2017 was attributed to tank silt application. Soil color changes were analyzed accounting for possible surface soil moisture changes. The proposed methodology was based on a well-balanced Calibration data created from the initial imbalanced Calibration dataset thanks to the Synthetic Minority Over-sampling Technique (SMOTE) methodology, coupled to the Cost-Sensitive Classification And Regression Trees (Cost-Sensitive CART) algorithm. To estimate the uncertainties of i) the two-class classification at each date and ii) the change of soil color from “Red” to “Black”, a bootstrap procedure was used providing fifty two-class classifications for each Sentinel-2 image.</p><p>The results showed that 1) the CART method allowed to classify the “Red” and “Black” soil with overall accuracy around 0.81 and 0.76 from the Sentinel-2 image acquired on February and April 2017, respectively, 2) a tank silt application was identified over 97 fields with high confidence and over 107 fields with medium confidence, based on the bootstrap results and 3) the identified soil color changes are not related to a surface soil moisture change between both dates. With the actual availability of the Sentinel-2 and the past availability of the LANDSAT satellite imageries, this study may open a way toward a simple and accurate method for delivering tank silt application mapping and so to study and possibly quantify retroactively this farmer practice.</p>

A synecological account of the Suikerbosrand Nature Reserve. II. The phytosociology of the Ventersdorp Geological System

Bothalia ◽  
1980 ◽  
Vol 13 (1/2) ◽  
pp. 199-216 ◽  
Author(s):  
G. J. Bredenkamp ◽  
G. K. Theron
Keyword(s):  
Plant Communities ◽  
Soil Texture ◽  
Nature Reserve ◽  
Surface Soil ◽  
Soil Depth ◽  
Soil Surface ◽  
Habitat Features ◽  
Species Groups

The vegetation of the Ventersdorp Geological System of the Suikerbosrand Nature Reserve is analysed and classified according to the Braun-Blanquet method. Descriptions of the plant communities include description of habitat features, the identification of differentiating species groups as well as the listing of prominent and less conspicuous species for the tree, shrub and herbaceous layers. The habitat features that are associated with differences in vegetation include altitude, aspect, slope, rockiness of soil surface, soil depth and soil texture.

Dissipation and Water Activation of UCC-C4243

Weed Science ◽  
1995 ◽  
Vol 43 (1) ◽  
pp. 149-155 ◽  
Author(s):  
Terry R. Wright ◽  
Alex G. Ogg ◽  
E. Patrick Fuerst
Keyword(s):  
Field Experiments ◽  
Soil Surface ◽  
Simulated Rainfall ◽  
Herbicide Application ◽  
Weed Species ◽  
Natural Rainfall ◽  
Near Ultraviolet ◽  
Glass Slides ◽  
Water Activation ◽  
Herbicide Activity

Field experiments were conducted in 1992 and 1993 to determine the timing and amount of rainfall required to activate UCC-C4243 applied preemergence. UCC-C4243 at 0, 70, and 140 g ai ha−1was applied 1, 7, 14, and 21 d before 0.5 or 2 cm of simulated rainfall. Temporary rainshelters protected field plots from natural rainfall during the 21 d dry period. Herbicide activity was determined in the field by seeding lentil, wheat, common lambsquarters, and field pennycress and in the greenhouse by a sugarbeet bioassay of soil samples (0 to 3 cm depth) taken from all plots immediately before irrigation. UCC-C4243 did not injure wheat; however, lentil population was reduced when simulated rainfall occurred within 7 d after application. Lentil injury was greater with higher herbicide rate and higher water level. UCC-C4243 at 70 and 140 g ha−1reduced populations of both weed species by 75 and 90%, respectively, when either 0.5 or 2 cm simulated rainfall was received within 1 d after herbicide application. Weed control was reduced with a 21 d delay between herbicide application and water activation. The sugarbeet bioassay showed a linear decrease of herbicide activity over time and also with accumulated photosynthetically active radiation. After 17.9 d, herbicide activity on a dry soil surface decreased 50%. Laboratory investigations show that [14C]-UCC-C4243 on glass slides was photodegraded by near ultraviolet light (290 to 400 nm). Volatilization of14C-labeled herbicide from glass slides was less than 5% after exposure to turbulent air for 48 h.

Effects of Age, Burial, and Region on Germination and Viability of Halogeton Seed

Weed Science ◽  
1969 ◽  
Vol 17 (1) ◽  
pp. 63-65 ◽  
Author(s):  
W. C. Robocker ◽  
M. C. Williams ◽  
R. A. Evans ◽  
P. J. Torell
Keyword(s):  
Seed Germination ◽  
Soil Surface ◽  
First Year ◽  
Laboratory Conditions ◽  
Winter Conditions ◽  
Field Germination ◽  
Field And Laboratory Conditions ◽  
Halogeton Glomeratus

The longevity of brown and black forms of seed of halogeton (Halogeton glomeratus (M. Bieb.) C. A. Mey.), buried at four depths, was determined for a 10-year period in Nevada, Idaho, Utah, and Washington. The black form of seed had almost 100% field germination at all depths by the end of the first year and had completely germinated or was nonviable by the end of the second. Brown seed on the soil surface began field germination the first year at all locations and had germinated or become nonviable at the end of 6 years. Burial at 1, 3, and 6 inches delayed the peak of viability and tended to increase longevity of brown seed. Germination was less than 0.5% at the end of 10 years, and viability was near zero under both field and laboratory conditions. Seed germinated and lost viability most rapidly in Washington, the location where most favorable winter conditions for germination occurred.

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