30 July, 2018
In order to get your cotton crop off to the best possible start, it’s critical that the seedbed is in the best possible shape and condition to achieve a successful uniform establishment. Poor crop establishment compromises productivity and may require the costly exercise of replanting.
Seedbed conditions need to be assessed with respect to aggregate size distribution in relation to seed size, which is important for seed soil contact. The type of planter to be used, in conjunction with soil moisture at planting can also affect the success of planting; as both tynes and disc openers can cause compaction which may compact root growth resulting in poor establishment due to increased soil disease.
Soil chemistry can influence establishment due to high levels of sodium, resulting in dispersion around the seed or seedling which harden on drying, forming a surface crust which can prevent the cotyledon from emerging along with the restriction of root growth.
Seedbed conditions should be assessed in relation to:
• The prior history of the field (fallow, wheat, sorghum or legumes).
• Soil moisture at the time of planting (plant on rain, planted dry and watered or watered and planted).
• The type of planter disc or tynes (with or without press wheels), the planting depth and planting at various speeds depending on the area to be planted soil aggregate size of the seed bed.
• The depth of planting in conjunction with cotton seed size.
Cotton Seed Distributors have developed a Field Conditions Score, a visual assessment of aggregates calculated by analysing the field texture, clod aggregate size, soil strength, moisture content, stubble cover and dispersion index. The scoring system is based on aggregate size of >2cm for a field score of 1; up to 10 – 15cm for a field score of 5.
By Chris Barry – Extension & Development Agronomist – Darling Downs and Central Queensland
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