The aim is to place the seed into the soil at the correct depth with the least amount of disturbance so disc drills have become preferable for this job. Row spacing is an important consideration and whilst close spacing is preferable for crop competition, too close will result in increased soil disturbance so aim for 125 - 150mm.
The growing cover crop has been conditioning and restructuring the soil profile, all the drill needs to do is place and cover the seed at the correct depth then gently firm the soil around the seed, taking care to minimise soil disturbance. This requires a change of mind-set as the resulting seedbed can often look particularly scruffy compared to the norm.
For Cultivator drills such as the Vaderstad Rapid, lift the system disc and following harrow clear of the soil, remove track eradicators (LGP tyres and correct pressures will help) and if possible, lift the bout markers also. It is essential that disc coulters are not badly worn and that seed coulters are in the raised setting allowing the leading edge of the disc to cut the slot for the seed.
Both Claydon and Dale have now developed a low disturbance option for their drills specifically for use with cover crops. For strip drills, again, lift all soil engaging components clear of work and rely solely on the seed coulters to place and cover the seed. Operators must be prepared to decrease forward speed to minimise soil disturbance, 8 - 10 km/h rather than 12 - 14km/h. Seedbed conditions are far more important than date of spring drilling. The cover crop tends to hold moisture at the surface. Go when too moist and excessive slot smearing may result. If the seed is covered and well consolidated giving good seed to soil contact then rolling won't be required. However if in doubt, rolling with worn Cambridge rings as opposed to more aggressive breaker type ring rollers is preferable.
Nitrogen
Our R&D programmes will look at seedbed fertiliser applications. We are investigating the implications other application methods and nitrogen timings on stimulating grass weed germination. Spring Cereals have a much shorter season with a faster establishment, leaf and tillering development phase, before moving into the stem extension phase. Early nutrition is essential so aim to apply up to 50% of planned N in the seedbed to maximise early growth to establish full ground cover for light interception and early weed competition. Demand for nutrients will accelerate as biomass develops.
Seed rates
Newer varieties of spring cereals are capable of achieving average yields in excess of 8t/Ha but on-farm yields have often disappointed, achieving yields lower than anticipated. Commonly suggested seed rates resulting in plant establishment counts ranging anywhere from 150 to 300 plants m2 at best are often the cause for poor yields. Recent work of spring wheat seed rates is ""sparse"" and seed rates are an area requiring new R&D work. However, limited data would suggest that the aim should be to establish nearer to 400 plants m2, always recognising that actual establishment achieved for spring sowings can vary considerably. For this reason, particularly later sowings where the plant's capacity to tiller may be compromised, then much higher seed rates should be considered.