Lecture 8 Flashcards
bulk density
the relative density of the soil material including the pore space
how is the bulk density of soil determined?
determined by oven dry mass of a specific volume of soil (collected in cores & not disturbed)
how much pore space does an ideal soil have?
50% pore space
bulk density is a function of soil ______ & ______
structure & texture
sandy soils have a ________ bulk density than clay soils
higher
what is a good indicator of soil chemical envr?
soil pH
what does soil pH influence/effect? (3)
influences availability of plant nutrients
soil microbes
decomposition
what is the optimal pH range for plant growth?
6-7
why does the rainforest have more acidic soil?
due to high amounts of leaching
what 2 characteristics of the soil facilitate good root penetration?
High degree of aggregation & many macro pores
what are the characteristics of a good soil? (5)
High degree of aggregation and many macro pores – facilitates root penetration
good water holding capacity
optimal gaseous diffusion
an adequate amount of nutrients with a large CEC
soil fauna (microflora) that promotes rapid decomposition of organic material making nutrients available to plants
where does soil organic matter originate?
plant, animal & microbial matter
how does soil organic matter improve the productivity of soils? (4)
source of nutrients during decomposition
improves soil structure
buffers rapid pH change
improves water holding capacity
how does organic matter improve the soil structure?
aggregates with minerals to improve aeration & drainage
is soil organic matter a source of slow or rapid release of nutrients?
slow release
what decomposes the animal & plant matter in soil organic matter?
microbes
what role does humus have in soil organic matter?
very stable part of SOM
Highly complex organic compounds that have
accumulated in the soil
what do we call material that is no longer recognized as plant material?
humus
what is the main way to soil improvement strategy?
incres in SOM
urban soil
A soil material having a non- agricultural, man-made surface layer more than 50 cm thick, that has been produced by mixing, filling, or by contamination of land surfaces in urban & suburban areas
what type of soil doesn’t represent a typical soil profile?
urban soil
what type of variability do urban soils have?
vertical & spatial
why do urban soils have vertical variability? (3)
topsoil scraped off & backfilled later
topsoil might be from a diff area
depth of topsoil often less than original soil
how do you improve root penetration in urban soils?
the top layer of soil needs to be broken down to allow root penetration
describe spatial variation in urban soils
May see large changes in very small space
T or F - spatial & vertical variability of soils can occur at the same time
T
why do urban soils have high compaction?
a result of soil displacement
what is the result of low organic matter?
affects aggregation & limits soil organism populations
There is a reduced rate of _____ in compact soils
drying
urban soils have _________ aeration & drainage
poor
