ASPECTS of seed quality vary in importance, depending on the crop and its intended market.
Fundamental to any good crop is good germination, followed by low levels of other crop species seeds, weed seeds, chaff and so on. And seed-borne diseases, such as loose smut in barley, can increase rapidly in only a few generations of seed.
The varietal purity of seed is important both for the crop itself and for the quality of produce. Crops of low varietal purity may ripen unevenly, leading to problems with shedding or combining.
Grain contaminated with another variety or off-types, resulting from cross-pollination, may fail to meet the specific requirements of end-users. For example, contamination of bread wheat with a feed variety will reduce hagberg, and contamination of malting barley can lead to rejection or lower premiums.
Producing quality seed depends on a system of quality assurance. For most seed this means the statutory certification schemes, but with attention to detail there is no reason why farm-saved seed cannot also meet farmers requirements.
In 1996 the proportion of crops grown from certified seed varied from about 50% for field beans to almost 80% for winter barley.
Almost 75% of C2 cereal seed is certified at the Higher Voluntary Standard (HVS) – meeting higher standards for contamination with seeds of other cereals and weeds, and for varietal purity.
Standards of other seed contamination for HVS C2 seed, for instance, is 3 seeds in 1kg compared with 7 in 500g for the minimum C2 standard. Similarly wild oats are not allowed in the HVS standard, but in theory, one wild oat in 1kg is for the minimum C2 standard.
The certification process starts with very high quality breeders seed, which after several generations produces C2 seed.
There are normally five generations involved; breeders seed, pre-basic, basic, C1 and C2. However, this can be reduced to three generations if necessary.
The three main quality controls are:
• laboratory examination and control plots of parent seed
• inspection of seed crops
• testing purity and germination
Seed crops and seed must meet these standards at each stage.
Savings can be made with farm-saved seed, but there is a risk without quality control checks equivalent to those used in certification. This means checking the crop, cleaning the seed carefully, and having it tested for purity and germination at a seed laboratory.
NIAB conducts seed tests for various diseases. The cost is £48 for loose smut on barley, £52 for net blotch and leaf stripe on barley and £48 for fusarium on wheat seed.
Some important aspects of seed quality, such as varietal purity, rely on starting with a good parent seed stock. For this reason most farm-saved seed is once grown from C1 or C2 seed, and is ultimately dependent on the certification system.
It is risky to home-save seed for more than one generation because the seed becomes too far removed from the guarantees of certified seed – in other words, varietal purity and contamination assurance.
That is not to say that certified seed is perfect. In a very small number of cases things go wrong at any stage, from harvesting to delivery of seed. The system is designed to stop mistakes in the first place and to detect them before the seed reaches growers.
Why is seed quality so important? Andrew Mitchell, head of NIABs seed production explains .