Seed grading

Prepare your seed for a golden harvest

Since humans first developed stable agriculture, seeds have become the world's most essential crop. That's because seed is the bridge between one generation of plant and the next.

There isn't a single good reason for planting poor quality seed, and, thank goodness, this is one thing you can control. The general rule is the larger the seed for any particular variety, the stronger and more vigorous the seedlings are likely to be. Large seeds also produce plants with more tillers than those grown from small seeds.

Why grade your seed?

As you might expect, a good heavyweight will beat a good lightweight any day. So the aim of seed grading is to maintain this quality from one season to the next by removing all these destructive elements:

Graph of cropping cost comparisons
Cropping cost comparisons

The results? You will have selected only the best and highest quality seed for sowing.

The cost of cultivating, fertilizing and controlling weeds in a paddock are high and you cannot afford to permit faulty, foreign or diseased seed to occupy your carefully prepared land.When efficient grading methods are used, the small grain which is unsuitable for seed is taken out and can be sold at market rates, while the screenings make excellent stock food.

Seed grading has the smallest cost input in crop management but the highest return (see chart).

Both expert official tests and practical results have proved that proper seed grading gives a dramatic increase in yield (up to 45% better from large grain compared to small grain).

Quality grading is economic

Seeds are living organisms and unless looked after will rapidly deteriorate. The value of high seed germination is obvious.

However, the vigour of seedlings is just as important.

Vigour is a seed's ability to germinate, emerge and produce healthy, rapidly growing seedlings even when planted in poor field conditions such as heavy crusting soils or when planted too deep.

A low vigour seed may germinate well in ideal conditions of temperature and soil moisture. However, in less than perfect conditions it's another story. Poor emergence may limit yield. Vigour is one of the most important characteristics of seed quality because of its vital effect on seedling establishment.

This was clearly shown by trial work conducted by the Department of Agriculture in Western Australia.

Seed quality improves emergence

Major findings were that small cereal seed will germinate just as well as large, plump seed, but emergence is considerably less for pinched, small and broken grain:

Seed type Germination (%) Emergence (%)
Large 95 85
Pinched 99 73
Small 91 72
Broken 21 3

Seed with less than 80% emergence is not considered satisfactory and will require higher sowing rates to obtain optimum plant density. Grading your seed maximises germination and emergence. In other words, grading produces high seed vigour.

Seed grading improves the competitive nature of seed

Larger seed not only has greater vigour but emerges faster. The speed of germination and emergence is a powerful factor because it occurs early in the growth of the crop. Early emerging seedlings have a high probability of being larger at stem elongation and of producing more grains than those that emerge a few days later.

Seed grading will actively encourage consistency as well as competitiveness of seed. Uniformity of seed permits more even distribution of grain through the drill. Seed spacing is important as blanks and then clusters are a disadvantage for optimum plant density.

Alf Hannaford, the father of the seed grading industry in Australia, once compared the importance of competitive seed to the composition of a football team:

"A football team with weak men loses the game. Twelve good men and six weak ones cannot make a good performance. The weak impairs the strong and are unable to withstand the opposition".

The importance of seed coleoptile

Drawing of emerging coleoptile
Emerging
coleoptile

The coleoptile is the sheath (or shield) which guides the shoot through the soil to the surface. The first leaf emerges from the coleoptile. It functions chiefly as a protective tube for the young foliage, which grows up through it to the surface. A high percentage of abnormal seedlings have a split in the coleoptile which restricts emergence. This is illustrated in the table below, which shows the effect of coleoptile quality on seed emergence.

Immature seeds with split coleoptiles are often the grains from the top and bottom of the smallest heads produced from late tillers.

These often appear when heavy rain falls late in the crop development . Abnormal seedlings and dead seeds occur at a higher rate in small seed. Removal of this unproductive seed is ample justification for grading.

Reference: Abral, B.K. (1980). Seed & Technology, Vol. 8, p. 59-76.
Treatment Field emergence
of seed (%)
Wet soils:
Slightly split coleoptiles
Intact coleoptiles
 
5
92
Intermediate moistures:
Slightly split coleoptiles
Intact coleoptiles
 
11
97
Dry soils:
Slightly split coleoptiles
Intact coleoptile
 
2
97

Legume seed—grading even more critical

Grading is critical with legume seed. That's because grain legumes have a very poor capacity to compensate for low plant numbers. So yield is vitally dependent on seed quality. Even the most experienced farmer cannot accurately assess the true quality of legume seed by visual inspection alone. Weather damage, rough handling, insects, poor storage, disease – all these vital factors may not be immediately obvious. Good crops are not grown on hope alone. You invest too much in a crop to risk poor establishment. Sowing correctly graded legume seed plays an essential part in overcoming all these problems. Only correctly graded seed ensures vigorous, healthy legumes.

Herbicide resistant weeds—yet another reason to grade

Herbicide resistance is increasing. This is arguably the gravest challenge to agriculture this decade. Weeds that have developed resistance to herbicides include annual ryegrass, wild turnip, wild oats, bindweed, capeweed, barley grass and Indian hedge mustard.

GRDC estimates are that resistance to herbicides could cost up to $100 per hectare in grain legumes and $30 per hectare in wheat in the first year alone. Nobody can afford an infestation of herbicide resistant weeds. Many paddocks have high levels of resistance in their weeds due to the sowing of contaminated seeds. Grading helps reduce weed seed reserves and contain the spread of herbicide resistant weeds. Seed grading has many advantages:

One of the central aims of a herbicide resistance management program is to reduce the number of viable weed seeds. Sowing seed which has been thoroughly cleaned is an integral part of herbicide resistance management.

The seed protection specialists

Your local Hannaford seed management specialist prepares high quality seed for sowing. Every grain fed into a Hannaford machine is separately handled with precision. And here's the sequence that achieves this …

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