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).

Heavy black soil, brigalow softwood

High yielding

Open black soil, plain, no tree

Medium yielding

Light soil, box, scattered brigalow

Poor yielding

Grower’s Knowledge & Experience

Grower’s knowledge

measurement

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

– Paddock assessmentSTEP 1

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?

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

– Soil testsSTEP 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.

– Interpretation of soil testsSTEP 3

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