The rain many have just received is most timely and will hopefully set the season up for high potential yields. As we all know, we cannot control when and how much rain we get, but there are key elements of achieving a successful crop that we can control.

Such control includes good weed control as well as sowing the crop in a timely fashion. Often forgotten is achieving your target plant density through knowing exactly how much of the seed you have to sow.

Varying grain size and weight can greatly affect the amount of seed sown. If always sowing seed at 80kg/ha, depending on wheat seed being either 28g or 42g per 1000 seeds, the resultant plant density will be 240 or 160 plants per square metre respectively.

Depending on your situation, the seeding rate may be either too dense or too thin. You have to alter the seeding rate to match the seed size being sown to know you will achieve the plant density you require.

To calculate the seeding rate required uses a formula which is worth noting and is relatively easy to use with a calculator. Firstly, to calculate your 1000 grain weight in grams, select a representative cup full of seed, then count out 1000 grains. This is easier and quicker than you might think. Spread the grains near the edge of a table. Using a knife or a card, scrape two grains at a time into an ice-cream container under the lip of the table. With some practice, selecting five grains at a time will get you to 1000 grains quicker.

Using a scale that measures at least to the nearest gram, tare another small container on the scale and then weigh the 1000 grains, and record the weight.

After having a cup of tea, reach for the calculator and use the following formula to calculate the seeding rate required.

Sowing rate (kg/ha) = 1000 grain wt. (g) x the plant density required (pl./sq m) ÷ percentage of seeds sown that emerge.

As an example, Yitpi seed weighing 40g/1000 seeds, the target plant population 180 and the % emergence at 85, then the seeding rate required is 85kg seed/ha. Where emergence is not known, a good average is 85%. With poor seed, heavier soil or deeper sowing, this may be less.

Once the crop is up after using both a known seeding rate and known 1000 grain weight, the % emergence can easily be calculated after counting the number of plants emerged per square metre.

Every farmer needs this year to be as successful as possible, so getting as many things right as possible under your control has got to be better than tempting fate.

AUTHOR: Tom Yeatman, Senior Sustainable Agricultural Systems Consultant, Rural Solutions SA
CONTACT: Tom Yeatman, Rural Solutions SA Clare Office, Telephone, 88 426 224, Email yeatman.tom@saugov.sa.gov.au