Transcript Every paddock is a field trial:

Every paddock is a field trial:
Observations, local knowledge,
paddock history and tests
provide the basis for the diagnosis of soil
and plant nutritional problems.
1. Observations of heterogeneity
• Are there responses to urine patches?  N or K.
Is the response by grasses or legumes?
• Are there responses to dung patches?  P, K or
acidity related. Response in grasses, legumes?
• Are there responses to ash heaps, or old tree
windrows?  K or acidity related.
• Are there responses to header trails?
 + = moisture, - = N tie-up.
• Are there responses to old lime or gypsum
stockpiles? (Near the gate )
Observations
2. Observations of plant symptoms
• Is there evidence of disease, insect pests, nematodes,
frost, or herbicide damage?
If the symptoms are suspected to be nutritional:
• Are the symptoms in drill rows or in patches?
• Are the symptoms on older leaves, younger leaves or whole plants?
• Are there indicator weeds?
e.g. sorrel for acidity or sea barley grass for salinity?
• If a grain legume, check nodules: number, size, internal colour?
e.g. lack of nodules = poor rhizobial activity, or soil acidity
lack of red colour = Mo deficiency.
• Are the roots stunted or spear tipped? e.g. Al toxicity or rhizoctonia.
3. Local knowledge of soil type
and topographic position
• Does excessive drainage or ponding occur
in this landscape position?
e.g. O2, N, Mn
• What is the texture profile?
e.g. Duplex, gradational, uniform; sandy, loamy, clayey?
• Are there subsoil constraints associated
with this soil type
e.g. acidity, sodicity, salinity or hardpans?
4. Paddock history
• When was the last pasture phase and how
long was it? (N fixed)
• When was the last legume crop? (N spared)
• When was Mo last used?
• What is the S history? (DAP and MAP are
not S sources).
Grower’s Knowledge & Experience
Grower’s knowledge
Heavy black soil, brigalow softwood
Open black soil, plain, no tree
Light soil, box, scattered brigalow
High yielding
Medium yielding
Poor yielding
measurement
STEP 1
– Paddock assessment
Is your paddock or parts of paddock showing
poor crop growth and yield, despite good
starting moisture and adequate in crop rainfall
Look for: diseases, insect pests, nematodes,
herbicide damage, weeds, frost damage
If these are not the cause, your SOIL maybe
limiting growth. Use the decision tree to help
identify soil constraints
Soil constraints
5. Chemical and physical tests
• Are there soil tests available?
Surface? Subsoil?
• Are there plant tissue tests available?
• Has there been testing for herbicide
residues?
• Have penetrometer readings been taken in
dry and wet soil? Infiltration tests?
– Soil tests
STEP 2
Take soil samples in good and poor areas separately at depth intervals
of:
0-10, 10-30, 30-50, 50-70 and 70-100 cm
.
Use tool kit (right) to ascertain levels
of:
1. pH
2. EC
3. Sulphur – spot rating
4. Chloride - spot rating
5. Chloride, mg/kg
6. Dispersion rating
7. Sodium, mg/kg
8. Nitrate, mg/kg
STEP 3
– Interpretation of soil tests
Constraints to cropping soils: decision made easy
Conclusion
• Observations,
•
local knowledge,
•
paddock history &
•
tests
provide the basis for the diagnosis of soil
and plant nutritional problems.
Examples of decision flow charts exist, but
require integration