5 April 2002



Keeping your rotation as diverse as possible will minimise pest and disease problems, help with weed control and improve soil structure, says Alastair Leake of the Allerton Trust.

But it has to be balanced with economic considerations and market needs. "There are costs associated with having diversified cropping, especially where land is spread out. Quotas and contracts limit some crops, while soil type may exclude others."

Targets to work towards include no single crop occupying over 25% and no crop group taking up more than 50% of the rotation. That means short rotations with two winter wheats will not meet his target, although they will be favoured for profitability.

"Avoid long runs of winter cereals, maximise the benefits of break crops and calculate gross margins over rolling five-year periods, not just on the basis of a single year."

Diverse crop mosaics offer greater biodiversity and also have an effect on soil condition and workability. "Make use of the different rooting characteristics of crop groups, as they will influence cultivation needs for following crops.

Crop choice will have more impact on beneficial insects and natural predators than pesticide use, says Mr Leake. "Including spring-sown crops is desirable, as it increases weed control opportunities and shifts workload peaks. But it can be less favourable to some invertebrates."

Planning is the key, he concludes.

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