June 2015 Q amp A Soils and Soil Fertility Trish Steinhilber psteinhiumdedu soil solution soil air primary minerals secondary minerals residues and byproducts humus biomass ID: 631355
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Master Gardeners’ Advanced TrainingJune 2015
Q & A – Soils and Soil
Fertility
Trish Steinhilber
psteinhi@umd.eduSlide2
soil solution
soil air
primary
minerals
secondary
minerals
residues
and by-products
humus
biomass
inorganic solids
organic solids
pore spaceSlide3
Organic Matter
75%
10%
15%
Department of Environmental Science and TechnologySlide4
Growth Factors:
What do plants need to grow?
1. water
2. oxygen
3. heat4. carbon dioxide
5. mechanical support6. nutrientsSlide5
Soil Aeration - The exchange of O
2
and CO
2 between the soil pores and the ambient atmosphere
HillelSlide6Slide7
Compaction
bulk density high enough or pore space low enough to negatively impact plant growth
bulk density >1.6 grams per cubic centimeter or pore space <40% will restrict root growth
information on either is difficult to obtainSlide8
Balance Between Water and Air
macropores (large pores)
drain quickly after rain or irrigation
allow rapid infiltration of rainfall and replenishment of oxygen in the root
zone
mesopores (medium-sized pores)“storage pores”hold water in form most plants can usemicropores (very small pores)
water is held too tightly to be used by most plantsrefuge of soil organisms when soils dry outSlide9Slide10Slide11
fine texture
medium texture
coarse texture
available water capacity
medium
high
low
nutrient holding capacity (CEC)
high
medium
low
infiltration & percolation
slow
medium
fast
crusting
high
medium
low
compaction
high
medium
lowSlide12
Soil Texture and Cation Exchange Capacity
Soil Texture
Cation Exchange Capacity
cmol
c
/kg
sands
fine sandy loams
loams and silt loams
clay loams
clays
1-5
5-10
5-15
15-30
>30 Slide13
What is a fertile soil?
one that provides an adequate supply of all nutrients throughout the entire growing
season
test soil
Is soil too acidic for plants being grown?
Are major nutrients present in adequate supply? Lime first, then
add other nutrients if needed.Slide14
soil acidity
:
the
adverse condition in the soil solution in humid regionsSlide15Slide16
Too much or too little ….Is too much of any nutrient bad for plants?
Is too much phosphorus bad for plants?
Is too little of a nutrient bad? Slide17Slide18
Soil Tests and Their Interpretation
Soil Test Category
Interpretation
very low, low
nutrient will, in all likelihood, limit plant growth
medium
nutrient may not be limiting; addition of nutrient advisable
sufficient, optimum or high
nutrient supply is OK; no more is needed
high, very high or excessive
nutrient supply is more than adequate; no more is neededSlide19
Lowering Phosphorus Soil Test Levels
possible
not needed
not ethical (personal opinion) Slide20
What Nutrient Source Should Be Used?
most organic sources are mixtures of N, P and K
appreciate single source fertilizers
ammonium sulfate, ureatriple superphosphate
muriate of potashSlide21
Composting Organic Materials
thermophilic
, aerobic process which changes
readily-decomposable compounds to more stable compounds
humus-like end productrequires the correct mixture of starting materialsbrown (high C/N) and green (low C/N)requires aerationSlide22
How Does Composting Alter an Organic Material?
ammonium and nitrate virtually
disappear
virtually all of the nitrogen is organic nitrogen
- N is released more slowly in composts than in feedstock materialslow in pathogens; friable and crumbly; pleasant, earthy odorSlide23
Poultry Litter from Delmarva(Preusch)
Type
Soil Texture
Mineralization Rate
fresh
sandy loam
.42
composted
sandy loam
.085
fresh
clay
.35
composted
clay
-.055Slide24
Mineralization Rates of Meat & Fish Processing Residuals (f-min)
Material
Type
Year of application
blood meal
0.65 - 0.70
feather meal
hydrolyzed
fresh
0.60 - 0.65
0.10
pelletized fish by-product
0.93
* fraction of original organic NSlide25
Mineralization Rates of Yard Waste and Composts (f-min)
Material Type
Year of application
Huck’s
Hen Blend
(VA)
(8 parts yard waste - 1 part hen manure, C/N = 29)
0.002
Panorama
Pay Dirt
(VA)
(1 part yard waste - 2 parts poultry litter, C/N = 18)
0.05
grass clippings (NJ)
0.25 (scl)-0.40 (sl)
* fraction of original organic NSlide26
Mineralization Rate Composts (f-min)
Material Type
Year of application
Bovung
1
-0.02
Fertilife
1
-0.02
Erth-rite-C
1
0.05
on-farm sheep manure & house-hold vegetable waste compost
-0.05
* fraction of original organic N,
1
Douglas and MagdoffSlide27
Gutser et al., 2005, J. Plant Nutrition and Soil ScienceSlide28
Protect the Soil Surface (esp. in fall)
minimizes erosion
protects soil aggregates
conserves moisture
moderates soil temperatureSlide29
Protect the Soil Surface –How?
protect soil from direct impact of rainfall
encourage a complete crop
canopy
mulchplant a cool season cover crop
minimize bare soil all seasons of the year!Slide30
Soil Tilth
a soil property that assesses the suitability of soil to support plant growth
a physical condition of a soil that relates to its ease of tillage, the impedance of seedling emergence and root penetrationSlide31
Tips for Maintaining Good Tilth
add organic matter
food for most soil creatures (heterotrophs)
amendments
cover crops**
warm and cool season choicesuse mulchmoderates temperature and moisture content
protects soil from crusting and erosionminimize extreme tillagerototillingSlide32
Questions? www.extension.umd.edu
/anmp
“Workshop Tools” tab
Soils (Basic) cell