Module 1 Flashcards
(40 cards)
Discuss the features of clay soil that make it so reactive
Clay particles are shaped like thin and flat platelets, they are also very small which means they have a very large surface area. Clay also has a charge which is mostly negative which can attract positively charged ions
What is Vt?
The total volume of wet soil
What is Pb?
Bulk density. Large bulk density maybe because it is a sandy soil or it is very compact
What is Pw?
Density of water
What is Ms?
The mass of the oven-dry soil
What is Mw?
The mass of water. Can calculate by subtracting Ms from the mass of the wet soil
What is w?
The gravimetric water content
What is θsat?
The volumetric water content of soil when it is saturated. To calculate θsat = f
What is f?
Porosity
What is θfc?
The volumetric water content of soil when it is at field capacity. To calculate θfc = θsat - θmp
What is θmp?
The macroporosity. The volume of all the macropores
What is θ?
The volumetric water content
What is the minimum value of macroporosity for good aeration?
10%
What is the field capacity?
The micropores are full of water but the macropores have successfully drained
What is saturation?
All the pores are full of water
Which two soil constituents have the largest surface area?
Clay and organic matter (hummus)
What is z?
The effective root depth and should always be converted to mm
How do you calculate the readily available water holding capacity of soil?
(θfc - θsp) x z
How do you calculate the total available water holding capacity of soil?
(θfc - θpwp) x z
What is θsp?
The volumetric water content at the stress point
What is θpwp
The volumetric water content at the permanent wilting point
How is soil structure assessed in the field?
The extent to which aggregates have formed and stability of these aggregates to a force applied. The shape of the aggregates. The size of peds.
What is the permanent wilting point?
When the plants have extracted all the water they are capable of taking from the soil
Features of good soil structure are…
Small aggregates that are stable