Glyphosate Substitution

Written by Thomas Preuße, Chief Editor “DLG-Mitteilungen” and DLG-Agrifuture Magazine

Forgoing glyphosate will increase the demands made on the cultivation system as a whole. It is vital to minimise
the pressure caused by weeds overall. Replacing glyphosate with one single alternative measure is therefore barely
conceivable, especially in systems that do not involve the use of ploughs. Wherever ploughing is not possible or desirable, greater importance will also (have to) be given to crop rotation and/or intercrops because of this.

Are Iron and Electricity the Answer

If the curtain really does come down on using glyphosate at the end of 2023 in the EU we do not yet know if the UK will follow. However, it does not mean either the end of the world or necessarily a forced return to ploughing. But it will certainly make life more difficult for regenerative farmers. They will have to think more extensively in terms of ‘the system’ than ‘the measure’. In the future, arable farming will not be led by the technology; instead, the technology will follow the arable farming objective.

For a while, the situation surrounding the most controversial crop protection active substance of all time had settled down a little, but the date has been set. Glyphosate is only approved throughout the EU until the end of 2022, and that is next year. Even if the active substance were to be registered again at EU level and approved nationally, its use will either be restricted in terms of quantity and/or will only be possible in special cases: the product has long since had its heyday. At times, it accounted for 70% of the crop protection agent volumes used in Germany. Another reason why glyphosate is so popular is that it can also be used to control volunteers such as grass weeds and rapeseed and not just rhizomatous weeds.

Farmers may say ‘If I can’t use glyphosate, I’ll just have to start ploughing again.

And many of them will do exactly that or are already doing so today. After all of their positive experiences, others don’t want to see a plough on their land again at any price. Amongst others, Detlev Dölger and Wiebke Lenge of Hanse Agro, a private consulting company headquartered in Schleswig-Holstein, believe that both groups should rethink their stances. The standard for the technology must be the arable farming objective – and only this, not the existing technology. To determine this objective and therefore make the right decision, it is necessary to ask oneself several questions, whereby the question concerning grass weeds is at the very bottom of the list.

• What are the demands of the subsequent crop; what time remains until sowing?

• Does the soil have to be loosened? • What about the volume of straw and chop quality?

• How deep down is the germination moisture? Where is it (too) dry or (too) moist?

• What must/can I do to control rhizomatous weeds, grasses, slugs, mice or cutworms?

Winter rapeseed after winter cereal, for instance, is a classic case in which forgoing glyphosate may pose a problem.

The time between harvesting and sowing is very short, and it is very tempting to use a plough before sowing. It couldn’t be easier: the straw is ploughed under, grass weeds are buried and the soil is sufficiently loosened. No wonder that plough sales have picked up again, although some people had already consigned this implement to the ‘scrap heap of history’. Boundary ploughing to control the influx of grasses is a widespread standard. But is it really necessary? If the location is dry, the straw can be easily worked in and sufficient time is available, there is nothing to suggest that tillage and cultivation cannot be undertaken without the use of a plough. Here, Hanse Agro recommends shallow cultivating (4 – 6 cm and 6 – 8 cm) twice to distribute and mix in the straw, then deep cultivating once and perhaps shallow cultivating once more as ‘false seedbed’ just before sowing. If grasses and volunteer rapeseed are involved, however, the objective is to leave their seeds as close to the surface as possible, encourage them to emerge and then control them mechanically. This is when very shallow tillage to a depth of 2 cm comes into play. Implements for this have been increasingly launched onto the market in recent years. A special share may possibly be required for loosening. Hanse Agro is going one step further in trials for problematic locations: precision sowing of rapeseed in wide rows enables subsequent hoeing to control grass weeds and/or volunteer rapeseed.

If sowing winter wheat after winter rapeseed is involved, compact disc harrows are often the solution and problem at the same time.

Working in too early and too deeply prevents the volunteer rapeseed from emerging. Again, the consultants recommend flat tillage several times using harrows, rollers or even mulchers in this case. The latter solution is expensive but very good for arable farming purposes because it encourages the rapeseed to germinate without it being buried.

In dry locations, the yield is often determined by forgoing ploughing due to water conservation.

Trials conducted by the Federal State Institute for Agriculture and Horticulture in Bernburg (LLG) of Saxony-Anhalt confirm this in a sugar beet – spring barley – winter wheat – winter barley crop rotation. Real conflicts of interest occur here: glyphosate was not required with ploughing or deep mulch seeding but led to poorer cost effectiveness (higher effort and/or lower yield). Shallow mulch seeding, strip tillage and direct sowing were not possible at this location in Saxony-Anhalt without this active substance, especially with high pressure from volunteer plants in tight crop rotations. Extending the crop rotation (in this case with lucerne) along with consistent harrowing and mulching subsequently kept the pressure caused by weeds to a manageable level in this trial. Together with glyphosate, however, we may also have to bid farewell to pure direct sowing forever. The conclusion drawn by Dr Joachim Bischoff (LLG) is that action recommendations as a patent solution are impossible. Instead, weed control should be regarded far more as a holistic system of diverse arable farming and crop production measures adapted to the specific location.

Before row crops.

A second ‘domain’ of glyphosate is its application prior to maize or sugar beet sown using mulch seeding in the spring. The ‘opponents’ are old weeds as well as catch crops that have not or not sufficiently been killed off during the winter. The objective is to achieve the best possible catch crop stock in order to suppress weeds. Of course, this is very difficult to establish in dry years such as 2018. The catch crop can be mechanically removed prior to vegetation. However, the prerequisite is that the soil can be driven on.

A spring-toothed harrow with uniformly shallow-cutting double-disc coulters particularly stood out in trials conducted at Bingen University of Applied Sciences with sugar beet. While the disc harrow enabled the intercrop to be regulated well, it was unable to control weeds and grass weeds. Pelargonic acid is occasionally claimed to be a substitute for glyphosate, but it proved ineffective in these trials. Straw mulch seeding is only considered to have a slight likelihood of success. Glyphosate is not needed for maize mulch seeding, as shown by trials in southern and eastern Germany and reported on by Klaus Gehring of the Bavarian State Research Center for Agriculture. Weed control using selective herbicides functioned equally well, unlike direct sowing or strip-till systems which are reliant on pre-treatment.

Electrophysical method.

Compared to glyphosate, the use of electricity as a herbicide substitute appears to be a niche solution, but without the total herbicide, even implements such as the ‘Elektroherb’ are attracting attention. A generator driven by the PTO produces electricity that reaches the plants, where it is distributed, via skids in the tractor’s front-mounted implement. In trials conducted so far, it has proved effective in controlling stubborn rhizomatous weeds and also in killing intercrops. Apparently, organisms in the soil are barely harmed. A further developed version of this system wets the plants with an electrolyte solution before the electricity is applied. This enables the necessary voltage to be significantly reduced and increases the system’s comparatively low efficiency.

Conclusion: don’t just deal with the symptoms. As has already been mentioned, forgoing glyphosate will increase the demands made on the cultivation system as a whole. It is vital to minimise the pressure caused by weeds overall. Replacing glyphosate with one single alternative measure is therefore barely conceivable, especially in systems that do not involve the use of ploughs. Wherever ploughing is not possible or desirable, greater importance will also (have to) be given to crop rotation and/ or intercrops because of this.