Simulated sheep urine causes the formation of acidic subsurface layers in soil under field conditions

Soil Research ◽  
2020 ◽  
Vol 58 (7) ◽  
pp. 662
Author(s):  
Jason R. Condon ◽  
A. Scott Black ◽  
Mark K. Conyers
Keyword(s):  
Subsurface Layer ◽  
Soil Surface ◽  
Bare Soil ◽  
Internal Diameter ◽  
N Transformations ◽  
Ammonium N ◽  
Subsurface Layers ◽  
Sampling Times ◽  
Sheep Urine ◽  
Treatment Application

This study aimed to ascertain whether application of sheep urine led to the development of acidic subsurface layers of a pasture soil. Deionised water or simulated urine solution delivering urea-nitrogen (N) at 44.8 g m–2 and potassium at 25 g m–2 was applied to soil in either winter or spring. Treatments were applied to the soil surface within 10.3 cm internal diameter PVC tubes inserted 20 cm into the soil either under ryegrass or kept bare. Main sampling times corresponded to the completion of various soil N transformations as determined by periodic sampling. Main samplings involved the collection of above ground plant material and soil sampling in 2 cm depth increments in 0–10 cm and 5 cm intervals in 10–20 cm depths. Following treatment application, urea and ammonium-N moved to a depth no greater than 20 cm but the extent of movement was greater in winter than spring due to the influence of initial soil moisture. Following urea hydrolysis, soil pH increased in the 0–15 cm depth. Subsequent nitrification significantly acidified soil under pasture by 0.8–1.0 pH units in the 2–8 and 2–6 cm depths in winter and spring respectively. This created a net acidic subsurface layer of 0.2–0.4 pH units compared with soil at the beginning of the experiment. Subsurface acidification was 0.5–0.7 pH units greater in bare soil compared with the presence of pasture. Transformations of N resulting from application of simulated urine solution formed acidic subsurface layers in the field regardless of the season of application.

Interactions of surface drying and subsurface nutrients affecting plant growth on acidic soil profiles from an old pasture

1986 ◽  
Vol 26 (6) ◽  
pp. 681 ◽  
Author(s):  
A Pinkerton ◽  
JR Simpson
Keyword(s):  
Subsurface Layer ◽  
Acid Soils ◽  
Subterranean Clover ◽  
Soil Surface ◽  
Soil Profiles ◽  
Poor Growth ◽  
South Wales ◽  
Reconstituted Soil ◽  
Subsurface Layers ◽  
Surface Drying

Previous studies on soils from old pastures in southern New South Wales have demonstrated that nutrients have accumulated at the soil surface, but that the 40-100-mm depth layer in many profiles has become strongly acidic (e.g. pH 4.7), and high in extractable aluminium. Poor growth of subterranean clover has occurred on such soils during dry periods and may be associated with poor root growth in the acidic, nutrient-poor subsurface layers. Possible nutritional causes of these observations were investigated using reconstituted soil profiles. The root and shoot growth of subterranean clover, wheat, oats and lucerne were compared in unamended profiles and in profiles amended by applying nutrients or calcium carbonate (lime) to correct the more obvious deficiencies of the subsurface layers. Subterranean clover grew well as long as the surface soil remained moist, so that plants could utilise the nutrients potentially available within it. When the surface (0-40 mm) was allowed to dry but the subsurface layers remained moist, growth was poor unless phosphate was applied to the moist layer. Subsurface application of lime alone was ineffective. Nitrogen application increased clover growth in the presence of added phosphate or surface moisture, but nitrogen alone did little to alleviate the effects of surface drought. Wheat, and to a lesser extent oats, responded to subsurface lime when the surface was moist, and both responded to subsurface phosphate when the surface was dry. Lucerne responded to subsurface phosphate similarly to subterranean clover but the response was more than doubled in the presence of additional borate and lime. Lime without borate was not effective. When the surface was maintained moist, liming both the surface (0-40 mm) and subsurface layers improved the response over liming the subsurface layer only. The results suggest that declining fertility and productivity in old pastures developed on acid soils may not be rectified by liming alone, but that cultivation, ripping or drilling of phosphate, and in some cases addition of borate, may be required to improve the penetration of nutrients, particularly phosphorus, to greater depth.

The role of N transformations in the formation of acidic subsurface layers in stock urine patches

Soil Research ◽  
2004 ◽  
Vol 42 (2) ◽  
pp. 221 ◽  
Author(s):  
J. R. Condon ◽  
A. S. Black ◽  
M. K. Conyers
Keyword(s):  
Soil Surface ◽  
Urea Hydrolysis ◽  
Balance Model ◽  
Urea Solution ◽  
Nitrogen Transformations ◽  
N Transformations ◽  
Soil Layers ◽  
Subsurface Layers ◽  
Dominant Process

This study examines the role of nitrogen transformations in the acidification of soil under stock urine patches, specifically the formation of acidic subsurface layers. These are horizontal planes of acidity several centimetres below the soil surface. Glasshouse studies were conducted to relate nitrogen transformations to measured pH changes in soil treated with urine or urea solution (simulated urine). Acidic subsurface layers formed in both urine- and simulated urine-treated soil. With the development of a H+ balance model, the contribution of nitrogen transformations to changes in the H+ concentrations in simulated urine patches was determined.During the first 9 days following treatment, urea hydrolysis and NH3 volatilisation dominated changes in H+ concentration. After that, net immobilisation contributed to H+ changes; however, nitrification was the dominant process occurring. Downward movement of NH4+ originating from urea hydrolysis allowed more nitrification to occur in lower soil layers. The net result of these processes was net acidification of the 4–6, 6–8, and 8–10 cm layers by approximately 0.7, 0.6, and 0.3 pH units, respectively. Thus nitrogen transformations were responsible for the formation of acidic subsurface layers in simulated stock urine patches within 6 weeks of application.

The extent, significance and amelioration of subsurface acidity in southern New South Wales, Australia

Soil Research ◽  
2021 ◽  
Vol 59 (1) ◽  
pp. 1
Author(s):  
Jason Condon ◽  
Helen Burns ◽  
Guangdi Li
Keyword(s):  
Agricultural Land ◽  
Subsurface Layer ◽  
Organic Amendments ◽  
Soil Surface ◽  
Cost Effective ◽  
Acidic Soil ◽  
Application Rates ◽  
South Wales ◽  
Subsurface Layers ◽  
Lime Addition

Soil pH is seldom uniform with depth, rather it is stratified in layers. The soil surface (0–0.02 m) commonly exhibits relatively high pH and overlies a layer of acidic soil of 0.05–0.15 m deep, termed an acidic subsurface layer. Commercial and research sampling methods that rely on depth increments of 0.1 m either fail to detect or under report the presence or magnitude of pH stratification. The occurrence of pH stratification and the presence of acidic subsurface layers may cause the extent of acidity in NSW agricultural land to be underestimated. Though the cause of pH stratification in agricultural systems is well understood, the effect on agricultural production is poorly quantified due in part to inadequate sampling depth intervals resulting in poor identification of acidic subsurface layers. Although liming remains the best method to manage acidic soil, current practices of low pH targets (pHCa 5), inadequate application rates and no or ineffective incorporation have resulted in the continued formation of acidic subsurface layers. Regular monitoring in smaller depth increments (0.05 m), higher pH targets (pHCa > 5.5) and calculation of lime rate requirements that account for application method are required to slow or halt soil degradation by subsurface acidification. If higher pH is not maintained in the topsoil, the acidification of subsurface soils will extend further into the profile and require more expensive operations that mechanically place amendments deep in the soil. Although the use of organic amendments has shown promise to enhance soil acidity amelioration with depth, the longevity of their effect is questionable. Consequently, proactive, preventative management of topsoil pH with lime addition remains the most cost-effective solution for growers.

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

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 Different Backscattering Models for Bare Soil Surface Parameters Estimation from SAR Data in band C, L and P

2016 ◽  
Vol 49 (1) ◽  
pp. 261-278 ◽  
Author(s):  
S. Mohammad MirMazloumi ◽  
Mahmod Reza Sahebi
Keyword(s):  
Soil Surface ◽  
Bare Soil ◽  
Parameters Estimation ◽  
Surface Parameters ◽  
Sar Data

A comparison of multi-polarization and multi-angular approaches for estimating bare soil surface roughness from spaceborne radar data

2002 ◽  
Vol 28 (5) ◽  
pp. 641-652 ◽  
Author(s):  
Mahmod R Sahebi ◽  
Joel Angles ◽  
Ferdinand Bonn
Keyword(s):  
Surface Roughness ◽  
Soil Surface ◽  
Bare Soil ◽  
Radar Data ◽  
Soil Surface Roughness ◽  
Spaceborne Radar

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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