Importance

The degree of clod development depends on many factors, including recent cultivations, water content at the time of tillage, the shear strength of clods and the quality of the soil structure. The loss of soil structure and the subsequent formation of clods reduce the quality of the soil tilth, impair seed germination and emergence and reduce crop yields and grain quality. Very cloddy soils indicate that the soil has become so degraded that it cannot maintain a fine aggregated seedbed throughout the growing season. The size, density and strength of soil clods increase with increasing loss of soil structure, so careful timing and considerable additional effort is needed to break them down to the required seedbed. This usually means that more intensive methods of cultivation and a greater number of passes are needed.

Assessment

• Assess the degree of clod presence on the soil surface between rows by comparing it against the three photographs.
• Consider the amount of cultivation and time that was taken to prepare the seedbed. Some soil clods may slake during rainfall so, to be meaningful, several assessments should be made up to crop maturity.
• Note that if the seedbed is too fine, it may be at risk of slaking and therefore water erosion or ponding.

Good
Moderate
Poor

Scoring

Good condition: Score 2

Good distribution of the friable, finer aggregates with no significant clods. A good seedbed is easily prepared.

Moderate condition: Score 1

Soil contains significant proportions of both coarse firm clods and friable fine aggregates. If cultivation is not carefully timed, clods slow significant tillage resistance.

Poor condition: Score 0

Soil dominated by coarse, very firm clods with fewer finer aggregates. Clod resistance is high and the window for successful cultivation is very narrow.