Suppressing young weeds with densely drilled crops is widely recommended in the battle against black-grass, but one Worcestershire farm has found drilling on wider rows can boost herbicide efficacy, cut weed burden and improve crop performance.
In a bid to move away from compaction, erosion and to tackle weed problems on the farm’s heavy Evesham lias clay, Springfield Farm near Pershore ditched the plough in 2010 and now runs an integrated strip tillage system.
With a background in arable trials work, farm manager, Ben Knight, says drilling cereals at a wider row spacing imitates trials, where it is not unusual for an 18sq.m plot of wheat to yield an adjusted 20 tonnes/hectare.
He says: “It’s the ‘edge effect’. Because a large percentage of a trial plot is bordered with space, you achieve a much stronger yield because of the better light interception. That’s what we’re trying to mimic with our wider row spacing.”
Winter wheat on the farm is typically drilled at 320 seeds/sq.m, as late as possible for black-grass control from the second week of October through to the end of October.
Drilling with a a Mzuri Pro-Til one-pass drill on 330mm centres with dual band coulters seeding rows 160mm wide, means when post-emergence herbicides are applied they are able to make much better contact with the weed because they are not affected by interrow shading, says Mr Knight.
“This means we haven’t lost the efficacy of the post-em because the weed is affectively getting a lower dose.”
As the season progresses from spring into June and key yield-building time, the rows close as higher tiller numbers are supported, filling the gap.
Mr Knight says: “We’re manipulating what the wheat plant will do at certain stages - we’re enabling the contact herbicide to do what we want it do at the beginning of spring, but then that extra light interception enables the plant to fill the space and reach its potential.”
As a Mzuri trial farm, Mr Knight regularly experiments with best practice techniques alongside the commercial enterprise, but one consistent result is that of light interceptions effect on yield.
The extra sunlight allows for a typically much stronger straw that can stand up to lodging better, and supports a higher yield as a result, he says.
“We’re in a predominantly mixed farming area, where the plough is still widely used. When it was farmed with the traditional plough-based, combination drill setup, yields were around 7t/ha.
Now, due to a combination of factors, including increased light interception and improvements to soil structure our five-year wheat yield average is 10.8t/ha.”
Over the past eight years, the 180ha farm has also pursued a greater focus on soil health, revamped its rotation, added cover crops to the mix and reintroduced livestock.
“All of the changes we have made have come together to build a healthy environment for the wheat plant to grow and compete against black-grass and other weeds,” Mr Knight says.
“We have healthier soils all-round – worm populations have grown and soil is draining a lot better. That’s creating an environment where the black-grass cannot thrive.”
Using a flufenacet pre-em, followed by mesosulfuron + iodosulfuron at post-emergence, black-grass on the previously heavily infested farm is now at a level that a majority can be hand-rogued before seed shed in June.
With a change to the farm’s rotation, which previously consisted of two wheats and OSR; spring crops, cover crops and a legume have been added to stretch the rotation to a four-year cycle of OSR, Wheat, a cover crop and spring legume, and back to wheat.
Mr Knight says: “The cover crops have been an important aspect for us along with not baling any straw on the farm in order to build soil organic matter - a healthy soil creates a healthy cash crop.
Cover cropping has also presented the opportunity for sheep to be reintroduced which can stimulate weed seeds to chit ahead of sowing. Because the soil is not worked to any depth, weed burden is kept in the upper layer of the soil to be able to chit and control in one go, rather than mixing it through the soil profile and getting multiple stages of emergence.