Drilling is the process where a drill sows seed into rows in the soil, before covering them up. This is an important operation that plays a large part in determining the success of a particular crop. Below we look at the operation in more detail and consider some of the issues that farmers address:

Drilling can only be done when the weather and soil conditions are right as the seeds have to be sown at the correct depth and immediately covered. This will not be possible if the ground is too wet or the soil is too cloddy. Often drilling is follwed by rolling which consolidates the soil and improves germination.

There are number of different kinds of drills. This one is mounted above a cultivator (painted green) that break down the soil before the seeds are sown. In the foreground a marker disc cuts a slice into the soil that the driver follows when drilling. This ensures that there are no misses!

The hopper of a drill may contain more than a tonne of seed. With the advent of mechanical loaders, many farms have moved to the use of 500 kg seed bags. These have replaced the 50kg bags that had to be loaded manually by the operator.

A full hopper of barley seed is ready for drilling and will be sufficient for about 15 acres. The slight orange colour to the seed is a "seed dressing" that prevents soil borne diseases infecting the plant. One of the most important diseases to be controlled is ergot, a powerful fungal infection that affects the crop and produces a black grain like body. Ergot is highly toxic, causes psychosis and has been blamed for periodic instances of widespread madness throughout history.

It is of critical importance for the farmer to ensure that the correct amount of seed is drilled evenly across the field. If the seed rate is too high the crop will be too lush and prone to disease. If the rate is too low, winter kill may leave bare patches producing no crop at all. All drills have accurate meters to control the delivery of seed into the ground and these have to be calibrated by the operator for each different crop.

The view of the hopper without seed illustrates the distribution system of the drill. Seeds are distributed evenly across the width of the drill by a large fan that blows the seed around the circular distribution chamber and down the pipes. The two rectangular boxes are used to create tramlines.

After the seed has been blown through the distribution system it travels down the "coulters". These are metal tubes that cut a slot into the ground into which the seed falls. At the back of the coulters are spring tines which help to cover the seed up (these are not easily visible in this image).

At the back of the drill is a tramline marker. This cuts a slot in the ground when tramlines are being created. This allows the farmer to navigate the field accurately before the crop has emerged.

Drills have to cope with all kinds of seeds, sowing rates and drilling depths. Here is some oil seed rape in a drill hopper that has also been treated to prevent soil borne disease.

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