Cover crop helps control black grass
03 Juli, 2018
03 July, 2018
Project Lamport, as this Bayer-Agrovista initiative is known, has been running in Northamptonshire in the English Midlands for four years. The soils in Northamptonshire tend to be heavy and arable farmers find it difficult to establish and grow high-yield spring crops there. Like on many UK farms black-grass infestation is a massive problem in Northamptonshire and before Project Lamport began, the indigenous black-grass population there was around 2,000 plants per square meter. Project Lamport involved examining the success of 14 different rotational systems in achieving the declared goals of a) controlling black grass, and b) facilitating the establishment of spring crops.
After consulting French scientists with experience in this field, the project coordinators decided to use black oats (Avena strigosa) as a cover crop. Black oats are good for soil structuring, good rust resistance and are easy to spray off. They can be drilled early and grow well into the winter, enabling a low seed rate to be planted to trap black grass in the autumn. Moreover, black oats also produce enough above- and below-ground biomass to facilitate direct drilling on heavy soils in spring. The varieties of black oats chosen for this project included Cadance, Panache and Altesses, which were typically partnered with a low rate of common vetch.
Project Lamport has shown that two important factors define successful crop cover use: a crop that allows black grass to germinate, and one that helps to improve soil structure. The cover crop and any black grass that had emerged were sprayed off with glyphosate and Companion Gold adjuvant in February and March. This approach resulted in a significant reduction in black-grass density so the population was low enough to be controlled using a low dose of a pre-emergence residual herbicide in the spring crop. As Mark Hemmant, Agrovista’s technical manager says, “We wanted to come up with a practical system that does not rely on herbicides – and in the past four years we have consistently done that.”
The results are impressive. The use of a low biomass cover crop followed by spring wheat led to 40.67 kg of viable weed seed return per hectare. If spring wheat followed a stale seedbed, which is common practice, the corresponding figure was 263.87 kg per hectare. In other words, the use of the black oat and common vetch cover crop significantly reduced the amount of black grass, while also improving soil conditions.