As spring sowing kicks up a gear, it is essential that the seed drill is calibrated to ensure even sowing and establishment.

Different varieties, thousand grain weights (TGW), seed lots and seed dressings will result in different seed rates and can result in seed flowing differently in the drill.

Before you calibrate your drill and indeed before you purchase your seed, you need to know your seed rate. If sowing is delayed, this may need to increase.

To calculate your seed rate, you need the TGW of the seed, the target plant population and the expected establishment percentage.

Some of this year’s Planet spring barley has a TGW of 53g.

If planting spring barley before mid-March, the target plant population would be around 280 plant/m2. After mid-March, this figure moves to 300 plants/m2. The expected establishment percentage would be 85%. This moves to 90% in April.

So, for Planet with a TGW of 53, you would multiply 280 by 53 and divide by 85 to get the seed rate.

(280 X 53) / 85 = 175kg/ha (11.1 stones/acre)

Calibrating the seed drill

Once you have calculated the seed rate, you can calibrate the seed drill.

Different drills will have different methods of calibration, so you should consult your handbook.

Some will input the necessary figures electronically in the cab, while some farmers may need to follow a chart on the drill to decide on ground wheel and seed wheel alterations.

On newer drills, the basics are the same once the drill is set up.

Method

Put seed into a clean drill and allow some seed to run through the drill into the collection tray for 20 seconds or so.

Empty the tray, as this step is just to have the seed running through the drill properly.

Empty the collection tray and either tare the scales with the tray on or take note of the weight of the tray.

You then need to let seed into the calibration tray. The time will vary depending on the drill. The time will also be entered into the computer.

Weigh the tray with the seed in and note the weight of the seed, not including the weight of the tray. Enter this into the computer system of the drill to gather information on forward speed and to check adjustments.