EFFECT OF CANOPY AND INCORPORATION ON METRIBUZIN PERSISTENCE IN SOILS

1989 ◽  
Vol 69 (3) ◽  
pp. 711-714 ◽  
Author(s):  
K. I. N. JENSEN ◽  
E. R. KIMBALL ◽  
J. A. IVANY
Keyword(s):  
Key Words ◽  
Half Life ◽  
Field Tests ◽  
Soil Surface ◽  
Bare Soil ◽  
Field Conditions ◽  
Row Width ◽  
Sampling Zone

The half-life of metribuzin applied to a bare soil surface was calculated to be 3–7 d over four field tests. An artificial cover erected after application or a shallow incorporation increased the half-life of metribuzin approximately 2.5- to 3-fold. Leaching out of the 0- to 5-cm-deep sampling zone could not account for loss of metribuzin. It was concluded that metribuzin persistence may be affected by volatility and/or photodecomposition losses under field conditions, especially shortly after application. Key words: Metribuzin half-life, volatility, photodecomposition, row width

The physical environment of two semi-arid tropical soils with partial surface mulch cover

Soil Research ◽  
1989 ◽  
Vol 27 (3) ◽  
pp. 577 ◽  
Author(s):  
KL Bristow ◽  
DG Abrecht
Keyword(s):  
Soil Surface ◽  
Tropical Soils ◽  
Bare Soil ◽  
Loamy Sand ◽  
Maximum Temperature ◽  
Clay Loam ◽  
Row Width ◽  
Dry Conditions ◽  
Mulch Cover ◽  
Semi Arid

The seedbed microenvironment in soils with partial surface mulch cover will be affected by the width of the bare row zones. In this paper we compare seedbed conditions under four bare row widths [0 cm (completely mulched), 5 cm, 15 cm and completely bare] during a drying cycle in a loamy sand and clay loam soil in a semi-arid, tropical environment. It is shown that for both soils the rates of drying were greatest in the bare soil and least in the mulched soil, with the 5 and 15 cm bare row width treatments showing trends which were intermediate between the two extremes. Although soil surface temperatures were not noticeably different between the two soils, differences at depth became substantial as the soils dried, with the maximum temperature at 5 cm depth in the loamy sand exceeding that in the clay loam. There was also a steepening in the temperature gradient with depth as the soils dried. Under both wet and dry conditions, maximum temperature at 5 cm depth increased significantly with bare row width up to a width of about 25 cm which, for mulch of negligible height, approximates a bare soil. Results of this work demonstrate the benefits of maximizing surface mulch cover in the semi-arid tropics.

scholarly journals The effect of maternally derived antibodies on the response of calves to vaccination against foot and mouth disease

1984 ◽  
Vol 92 (1) ◽  
pp. 105-116 ◽  
Author(s):  
M. J. Nicholls ◽  
L. Black ◽  
M. M. Rweyemamu ◽  
J. Genovese ◽  
R. Ferrari ◽  
...  
Keyword(s):  
South America ◽  
Half Life ◽  
Foot And Mouth Disease ◽  
Primary Vaccination ◽  
Mouth Disease ◽  
Field Conditions ◽  
Satisfactory Response ◽  
Foot And Mouth

SUMMARYStudies were carried out in South America to assess the effect of maternally derived antibody (MDA) on the responsiveness of calves to FMD vaccination. It was found that calves with MDA did not merely fail to respond to vaccination, but that their serum titres were depressed. This depression was proportional to the level of pre-existing MDA at the time of vaccination and following primary vaccination it persisted for a least 60 days. High MDA titres interfered with both primary and secondary responses. Animals with relatively low MDA titres were able to respond to vaccination, or at least to be sensitized so that on revaccination they showed a satisfactory response. The half-life of MDA was shown to be approximately 22 days, suggesting that under field conditions significant MDA titres are likely to persist for 4–5 months. A trial carried out in Brazil in which the primary course of two inoculations, 4 weeks apart, was initiated when the calves were 5–6 months of age, resulted in the reduction of FMD in the calf population from 11% to 0·9% over a 12-month period. The use of vaccination programmes of this type to lessen the incidence of FMD in young bovines is discussed.

Residual Large Trees Influence Short-term Succession Following a Volcanic Eruption in a Valdivian Temperate Rainforest

2021 ◽  
Author(s):  
Lisa Hintz ◽  
Dylan Fischer ◽  
Nina Ferrari ◽  
Charlie M.S. Crisafulli
Keyword(s):  
Soil Surface ◽  
Bare Soil ◽  
Understory Vegetation ◽  
Percent Cover ◽  
Vegetative Cover ◽  
Vegetation Response ◽  
Temperate Rainforest ◽  
Large Trees ◽  
Close Proximity ◽  
Disturbed Forest

Abstract Airborne volcanic ejecta (tephra) can strongly influence forest ecosystems through initial disturbance processes and subsequent ecological response. Within a tephra-disturbed forest, large trees may promote plant growth and create favorable sites for colonization. Three primary ways trees can influence post-eruption vegetation response include: 1) amelioration of volcanic substrates, 2) as source propagules from the tree or from associated epiphytes, and 3) by sheltering understory vegetation, thereby increasing rate of recovery near tree bases. Here, we evaluate Valdivian temperate rainforest understory vegetation response and soil characteristics in close proximity to large trees that survived the 2015 eruption of Calbuco Volcano. Understory vegetative cover was higher near the base of trees for mosses, many epiphytes, and some herbaceous, shrub, and trees species. However, significant interactions with year of measurement, and individualistic responses by many species made generalizations more difficult. Small shrubs and trees in particular demonstrated patterns of recovery that were frequently independent of distance. In some cases, percent cover of colonizing vegetation actually increased far from trees by 2019. The soil surface was similarly variable where bare soil cover was associated with locations proximal to tree bases, but material shed from living and dead standing vegetation increased wood and litter abundances on the soil surface away from the base of trees. Soils near trees had lower pH, elevated organic matter, and higher nitrogen and carbon. Our results support the assertion that in this temperate rainforest ecosystem, large trees can modify edaphic conditions and provide important early refugia for vegetative regrowth following a tephra fall event. Nevertheless, complex interactions through time with species and growth form, suggest the influence of large trees on plant establishment and growth with close proximity tree boles is more complex than a simple facilitative model might suggest.

A physically-based soil surface model and its combination with numerical models for predicting bare-soil evaporation rates

2021 ◽  
Author(s):  
Xiaocheng Liu ◽  
Chenming Zhang ◽  
Yue Liu ◽  
David Lockington ◽  
Ling Li
Keyword(s):  
Numerical Model ◽  
Surface Resistance ◽  
Numerical Models ◽  
Soil Column ◽  
Soil Surface ◽  
Bare Soil ◽  
Water Vapor Transport ◽  
Surface Model ◽  
Vapor Flow ◽  
Physically Based

<p>Estimation of evaporation rates from soils is significant for environmental, hydrological, and agricultural purposes. Modeling of the soil surface resistance is essential to estimate the evaporation rates from bare soil. Empirical surface resistance models may cause large deviations when applied to different soils. A physically-based soil surface model is developed to calculate the surface resistance, which can consider evaporation on the soil surface when soil is fully saturated and the vapor flow below the soil surface after dry layer forming on the top. Furthermore, this physically-based expression of the surface resistance is added into a numerical model that considers the liquid water transport, water vapor transport, and heat transport during evaporation. The simulation results are in good agreement with the results from six soil column drying experiments.  This numerical model can be applied to predict or estimate the evaporation rate of different soil and saturation at different depths during evaporation.</p>

scholarly journals Assessment of the Accuracy of a Multi-Beam LED Scanner Sensor for Measuring Olive Canopies

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4406 ◽  
Author(s):  
Rafael Sola-Guirado ◽  
Sergio Bayano-Tejero ◽  
Antonio Rodríguez-Lizana ◽  
Jesús Gil-Ribes ◽  
Antonio Miranda-Fuentes
Keyword(s):  
Laboratory Test ◽  
Real Time ◽  
Relative Error ◽  
Laser Scanner ◽  
Field Tests ◽  
High Accuracy ◽  
Field Conditions ◽  
Canopy Trees ◽  
Canopy Volume

Canopy characterization has become important when trying to optimize any kind of agricultural operation in high-growing crops, such as olive. Many sensors and techniques have reported satisfactory results in these approaches and in this work a 2D laser scanner was explored for measuring canopy trees in real-time conditions. The sensor was tested in both laboratory and field conditions to check its accuracy, its cone width, and its ability to characterize olive canopies in situ. The sensor was mounted on a mast and tested in laboratory conditions to check: (i) its accuracy at different measurement distances; (ii) its measurement cone width with different reflectivity targets; and (iii) the influence of the target’s density on its accuracy. The field tests involved both isolated and hedgerow orchards, in which the measurements were taken manually and with the sensor. The canopy volume was estimated with a methodology consisting of revolving or extruding the canopy contour. The sensor showed high accuracy in the laboratory test, except for the measurements performed at 1.0 m distance, with 60 mm error (6%). Otherwise, error remained below 20 mm (1% relative error). The cone width depended on the target reflectivity. The accuracy decreased with the target density.

scholarly journals The method for recalibration of thoron concentration reading of RAD7 and obtaining the thoron exhalation rate from soil surface

2013 ◽  
Vol 28 (1) ◽  
pp. 92-96 ◽  
Author(s):  
Yanliang Tan ◽  
Detao Xiao
Keyword(s):  
Flow Rate ◽  
South China ◽  
Soil Surface ◽  
Field Conditions ◽  
Radon Exhalation Rate ◽  
Exhalation Rate ◽  
Air Flow Rate ◽  
Rapid Decay ◽  
The University ◽  
Chamber Technique

Thoron exhalation rate can be obtained through the combination of the ?accumulation chamber? technique and RAD7. Thoron?s rapid decay causes the intake path and the air flow rate to become important factors in calibration. In field conditions, since the flow rate of the internal pump in RAD7 will change as the voltage of the battery decreases, the big drying tube is more suitable for a long measurement than the small drying tube. We developed the method for recalibration of the thoron concentration reading of RAD7 based on the calibration factor for 222Rn, and obtained the thoron exhalation rate from soil surface near by the Radon Laboratory of the University of South China. This method can be applied to develop and improve instruments for measuring the radon exhalation rate.

Germination strategy of the East African savanna tree Acacia tortilis

2005 ◽  
Vol 21 (5) ◽  
pp. 509-517 ◽  
Author(s):  
Paul E. Loth ◽  
Willem F. de Boer ◽  
Ignas M. A. Heitkönig ◽  
Herbert H. T. Prins
Keyword(s):  
National Park ◽  
Laboratory Experiments ◽  
Perennial Grass ◽  
Soil Surface ◽  
Bare Soil ◽  
Acacia Tortilis ◽  
East African ◽  
Tree Canopies ◽  
Arable Fields ◽  
Germination Success

Germination of Acacia tortilis seeds strongly depends on micro-site conditions. In Lake Manyara National Park, Tanzania, Acacia tortilis occurs abundantly in recently abandoned arable fields and in elephant-mediated gaps in acacia woodland, but does not regenerate in grass swards or beneath canopies. We examined the germination of Acacia tortilis using field and laboratory experiments. Seeds placed on top of the soil rarely germinated, while seeds covered with elephant dung or buried under the soil surface had a germination success between 23–43%. On bare soil 39% of both the dung-covered and buried seeds germinated, in perennial grass swards 24–43%, and under tree canopies 10–24% respectively. In laboratory experiments, seed water absorption correlated positively with temperature up to 41 °C, while subsequent germination was optimal at lower (21–23 °C) temperatures. Seeds that had absorbed water lost their viability when kept above 35.5 °C. The absence of light did not significantly influence germination success. Acacia tortilis does not actively disperse its seeds, but regeneration outside tree canopies was substantial. The regeneration potential thus strongly depends on the physiognomy of the vegetation.

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