Article taken from Agronomist & Arable Farmer, September 2017.
Latest findings at Agrovista's Project Lamport site in Northants clearly demonstrate that using a black oat-based cover crop ahead of a spring crop produces bigger profits and much better blackÂgrass control on heavy land than an over-wintered fallow.
Destroying the cover crop at the right time, and following on with the correct spring crop, is also vital in the battle to keep black-grass numbers down to manageable levels.
Spring drilling is an important tool to help defeat black-grass. However, it can be fraught with difficulty on heavy land, usually due to soils remaining wet and sticky well into the spring, resulting in very late sowing or preventing a crop being drilled at all, said Agrovista technical manager Stewart Woodhead.
""Using the correct black oatÂbased cover crop helps dry the soil out, optimising conditions for direct drilling the spring crop," he explained.
Omitting the cover crop means there is nothing to help soil structure, said Mr Woodhead. ""Apart from producing poorer yields and profits, largely due to poor establishment, opting for an over-wintered fallow failed to achieve consistent black-grass control in the following wheat crop (see table 1).
""This is because the cover crop also helps bind the soil together, improving the benefits of no-till.
""In the fallow plot, the soil moved too much and shattered when the direct drill went through.
""This allowed black-grass to chit, returning more than six times as much black-grass seed to the soil than with our cover crop regime, which is allowing the population to increase.""
Early destruction advantage
Destroying the cover crop with glyphosate at around Christmas time appears to be the optimum timing, rather than a couple of weeks before drilling, which can leave excess debris that traps too much moisture in the top inch or two of soil. The cover crop still has time to develop enough root to condition, dry and stabilise the soil ahead of sowing.
Under this regime, yields and profits have risen substantially, compared with early spring destruction, while the black-grass count fell sharply (Table 2)).
""We expect a similar yield advantage again this season," said Mr Woodhead. ""We were concerned that the soil wouldn't hold together as well at drilling, but the roots appear to be binding it together. We have found the spring crop gets out of the ground quicker and yields better, without increasing black-grass count.""
Alternative spring crops
For the second year running, spring barley is also showing good potential under the Agrovista regime.
Last season, a crop of KWS Irina produced better profits than spring wheat and a low black-grass count (table 2). This season's crop, sown at 450 seeds/sq m, looks like putting in a similar performance, although more black-grass is making an appearance.
""Last autumn, the cover crop was swamped with spring barley volunteers. This reduced autumn black-grass germination, but encouraged more to emerge in the spring," Mr Woodhead said.
Other plots show the importance of selecting a competitive spring crop. Soya and linseed have struggled to establish in the dry spring, and springôgerminating black-grass was rife in both plots, despite soil having only been moved in April and May respectively.
Input costs adjusted for cover crop seed; wheat priced at £135/t