Forward planning problems as harvest drags on-SAC experts urge farmers to be on alert

This years protracted harvest may not have seen the flattened crops of years like 1985 but SAC Crop and Soil specialists point out that, along with high drying charges or tracked and wheel damaged fields, the 2011 conditions have left other issues for farmers to take account of. Well made plans may have to change.

According Mark Ballingall of SACs Crop and Soil Systems Team,

In contrast to 1985 there is now more reliance on winter sown crops so the knock on effects of the 2011 wet harvest and autumn is greater.

In the main, most winter rape, sown after harvesting winter barley, was drilled into reasonable seed beds, but the following persistent rain has impacted on the ability of many growers to control any weeds using herbicides applied just before or just after the rape seedlings emerge.

This is particularly significant with weeds like brome and black-grass says Mark. There are no products effective at a later stage.

Meanwhile SACs Dr Fiona Burnett warns that conditions have been ideal for clubroot development in oil seed rape crops. In previous wet autumns severe galls have developed early in fields previously not suspected of being infected with the disease.

Watch crops and investigate any signs of patches of stunted or purpled plants she suggests.

The conditions have also suited slugs which have taken their toll on some crops. Strict environmental controls on the applications of the pesticide metaldehyde and the difficulties of keeping slug pellets intact in the rain have made pest control difficult. Nevertheless the SAC advice to farmers is to do nothing that might lead to metaldehyde leaching into water courses.

With the winter wheat harvest delayed in many northern areas there will be an impact on the area of second wheat crops that can be drilled for next season. Wet soils can delay emergence, especially when soil temperatures start to drop. Some seed treatments also delay emergence so their use on later sown crops is not advised as this will only exacerbate the problem.

Potatoes, which are also proving difficult to harvest, are often followed by winter wheat so delays with the potatoes impacts on drilling plans for the grain crop. This will also increase the threat from wheat bulb fly as there is a lower threshold for damage in later sown wheat and wheat bulb fly egg counts suggest crops after potatoes will be at risk this season.

The combination of rain, combines, laden grain trailers, balers and bale handlers means soils take a beating with significant compaction. The heavier the machinery the deeper the compaction goes.

While SAC Soil Scientist Dr Bruce Ball understands farmers will now be anxious to establish winter sown crops he urges caution.

It is important now to avoid further damage by working the soil when it is wet. Ploughing wet soil can destroy the soil structure which is fundamental to providing good conditions for crop growth and controlling greenhouse gas emissions from the soil. The more compact and smeared the soil, the greater the likelihood of waterlogged crops.

Harvest compaction blocks the soil macropores which reduces drainage, leading to wet soils with loss of nutrients and possible erosion. Soil damage shows up as pans, clods, smeared surfaces or smelly layers. They can be detected in a simple guide on soil structure produced by SAC and colleagues from Aberdeen and Arhus Universities and called Visual Evaluation of Soil Structure..

Bruce Ball suggests that dealing with compaction may sometimes need to be delayed until the spring when the soil has had a chance to dry out. His experience of previous wet harvests shows that it may be worthwhile allowing the soil to recover its production potential rather than puddling in a crop which will give low yields.