El agua y las raíces pueden El agua y las raíces pueden pasar entre los macro porospasar entre los macro poros
Suelo de partículas dispersados Suelo de partículas dispersados destapan los macro porosdestapan los macro poros
Superficie de costra
Cationes FloculadosCationes Floculados
• Podemos dividir los cationes a dos categorías– Floculadores
malos• Sodio• Potasio
– Floculadores buenos• Calcio• Magnesio
IonPoder Relativo de
Floculación
Sodio Na+ 1.0
Potasio K+ 1.7
Magnesio Mg2+ 27.0
Calcio Ca2+ 43.0
Proporcion de Adsorción de SodioProporcion de Adsorción de Sodio
La proporción de los floculadores ‘malos’ a ‘buenos’ provee una indicación del estatus relativo de estos cationes:
Na+++
+ + ++
+
Ca2+ and Mg2+++
++++++++++
++
Matemáticamente, está expresado como el “radio de adsorción de sodio’ o RAS:
donde las concentraciones están expresados en mmoles/L
SAR = [Na+]
[Ca2+] + [Mg2+]
Ca2+ and Mg2+Na+
RAS
CE
La estabilidad de aglomerado (dispersión y floculación) depende en el equilibrio (RAS) entre (Ca2+ y Mg2+) y Na+ así como la cantidad de sales solubles (CE = Conductividad Eléctrica) en el suelo.
Suelo Floculado
Suelo Dispersado
++++++
++++
++
+ + +++++
+
+
CE más baja CE más alta
Na+
RAS
CE
Las partículas de suelo floculan si las concentraciones de (Ca2+ + Mg2+) están mas elevados relativamente a la concentración de Na+ (RAS está disminuído).
Suelo Floculado
Suelo Dispersado
+
++
Ca2+ and Mg2+
++
++++
++++
++++
++++
++
Na+
RAS
CE
Suelo Floculado
Suelo Dispersado
+
++
Ca2+ and Mg2+
++++++
Las partículas de suelo se dispersan si las concentraciones de (Ca2+ + Mg2+) están disminuidas relativamente a la concentración of Na+ (RAS está aumentado).
++
+
+
Partículas de suelo floculan si la cantidad de sales solubles en el suelo se aumenta (CE aumentada), aunque existe mucho sodio.
Suelo Floculado
Suelo Dispersado
Na+
RAS
CE
Ca2+ and Mg2+
CE más baja CE más alta
++
++
+
+
+
++
++++
++++
++++
++++
++
Partículas de suelo se pueden dispersar si la cantidad de sales solubles en el suelo se disminuyen (i.e. si CE esta disminuido).
Ca2+ and Mg2+
Na+
RAS
CE
CE mas baja
Suelo Floculado
Suelo Dispersado
CE mas alta
++++
++
+
++
Terrazas en NepalTerrazas en Nepal
FIN
Soil ErosionSoil Erosion
Erosion ProcessesErosion Processes
• Detachment– Destruction of aggregation: raindrops, flowing
water, ice, tillage, wind, animals, vehicles
• Transport– Movement of detached particles: ice, gravity,
wind, water
• Deposition– Eroded particles find a new home
Erosion by WaterErosion by Water
• Raindrop Splash Erosion– Causes initial detachment.
Can be minimized by good soil cover.
• Surface Flow– Causes transport. Can be minimized by
good soil cover and anything that reduces slope or slope length.
Sheet erosion
RillsRills
Gullies - ArizonaGullies - Arizona
Texturing Soils by Hand
START: Place approximately 3 tablespoons of soil in palm. Add drops of water and knead the soil to break down aggregates. Soil is at the proper consistency when it is plastic and moldable. If soil is too dry, add more water; if it is too wet, add more soil.
Does soil remain in a ball when squeezed?
Place ball of soil between thumb and forefinger, gently pushing the soil with the thumb and pushing upward to form a ribbon. Allow the ribbon to emerge and extend over the forefinger, breaking from its own weight.
Does soil form a ribbon?
Is the ribbon1 inch
long before breaking?
Is the ribbon1-2 inches
long before breaking?
Is the ribbon >2 inches
before breaking?
Excessively wet a pinch of soil in palm and rub with forefinger.
Does soil feel very gritty?
Does soil feel very gritty?
Does soil feel very gritty?
Does soil feel very smooth?
Does soil feel very smooth?
Does soil feel very smooth?
Neither grittiness or smoothness predominates
Neither grittiness or smoothness
predominates
Neither grittiness or smoothness
predominates
NOSAND
NO
LOAMY SAND
NO NO
NO
NO
SANDYLOAM
SILTLOAM
LOAM
NO
NO
NO
NO
SANDYCLAYLOAM
SILTYCLAYLOAM
CLAYLOAM
SANDYCLAY
SILTYCLAY
CLAY
USDA Texture USDA Texture TriangleTriangle
12 12 TexturalTextural Classes Classes
10
20
30
40
50
60
70
80
90
100
10
20
30
40
50
60
70
80
90
100
100 90 80 70 60 50 40 30 20 10
SandLoamySand
SandyLoam
Loam
SandyClay Loam
Clay Loam
Silt Loam
Silt
Silty ClayLoam
SiltyClay
Clay
SandyClay
SAND (%)
SILT
(%)
CLA
Y (
%)
18 17
1416 15
94
13
12 11
106
57
8
321
Universal Soil Loss EquationUniversal Soil Loss Equation(for water erosion)(for water erosion)
A = R . K . LS . C . P
A = erosion loss in tons/acre/yrR = rainfall factor (amount/intensity)K = soil erodibility factor (texture/ SOM)LS = slope-length factor (angle/length of slope)C = cover and management factor (crop/tillage)P = practice factor (erosion control measures)
Average Annual Rainfall Factor (R)
Soil Erodibility Factor (K)Soil Erodibility Factor (K)
• Depends on– rate of water infiltration– structural stability
• High K factors (high erodibility) caused by:– Soils high in silt and fine sand– Platy or massive soil structure
• A value is assigned to each soil series
Soil Erodibility Factor (K)Soil Erodibility Factor (K)Texture Organic matter content
<0.5% 2% 4%
Sand 0.05 0.03 0.02
Loamy sand 0.12 0.10 0.08
Sandy loam 0.27 0.24 0.19
Loam 0.38 0.34 0.29
Silt loam 0.48 0.42 0.33
Silt 0.60 0.52 0.43
Clay loam 0.28 0.25 0.21
Clay 0.13 – 0.29
Length-Slope (LS)Length-Slope (LS)
Cover (C)Cover (C)
Controlling Water ErosionControlling Water Erosion
• Control detachment– protect the soil surface from rain, mechanical
disturbance– encourage soil aggregation
• Control transport– Slow down water movement
Reduced TillageReduced Tillage
Grassed WaterwaysGrassed Waterways
Strip Strip CroppingCropping
Terracing in NepalTerracing in Nepal
Terracing - LebanonTerracing - Lebanon
These rock-walled bench terraces have been in use for thousands of years.
Erosion is much easier to prevent Erosion is much easier to prevent than to stop !than to stop !