The weed seed burden - is the problem within our control?

Soil is undeniably the most important asset to any farming system, without it most of the food that we grow would cease production. So, it’s no wonder modern farming practices have taken huge leaps towards taking better care of the soil we’ve got.

Sustainable farming practises are being adopted widely across the country, not only through government incentives but also through recognised improvements in soil health. We can achieve this through practises such as increasing soil organic matter i.e., growing and incorporating cover crops and green covers, and reducing cultivations, thereby maintaining soil structure and minimising soil carbon loss as well as reducing machinery input costs.

These sustainable growing systems such as no-till and min-till aren’t the simple answer to all of our problems, with the soil association noting that many no-till or min-till systems have had to resume ploughing due to frequent and severe outbreaks of grass weeds. Reduced soil movement comes with additional challenges, such as; an increased weed seed burden, increased compaction and increased slug pressure (NFU, 2022).

At Amazone we endorse a reduced soil movement farming system; direct drilling where possible and employing shallow surface cultivations only when required. Targeted deeper cultivations are sometimes necessary; our recommended approach being a 40mm share on an Amazone Ceus to create deep fractures and enable root penetration, whilst only mixing the top 5 cm with the front discs maintains soil structure. Preferably though, we encourage utilising vigorously rooting cover crops to initiate deeper loosening as a more cost-effective option. These work by leaving soil drainage channels after their roots have decomposed. Research by Chen, G et al, found Brassicas were most effective for this purpose. But what does all this do for the weed problem?

Increasingly we rely upon glyphosate as a means of controlling the weed burden, rather than the use of cultivations and stale seedbeds. Unfortunately, glyphosate’s days are numbered, with glyphosate resistant weeds beginning to appear, resistant grasses being just one of them. It’s not just glyphosate that suffers resistance build up, the case is true of most current herbicides, with many showing a loss of effectiveness on certain weed types. But how does resistance occur and how can we take steps to reduce the chance of other common weeds also becoming resistant?

Spraying

The key to reducing resistance is by using multiple different modes of action to destroy weeds, not only utilising different chemicals, but by also incorporating mechanical weeding and clever rotations into your system. Another possible path for resistance build up is through improper spray application, plants receiving improper dosages have the possibility to build an immunity, therefore applying chemical to the highest possible accuracy is imperative. This is where Amazone’s precision farming spray technology comes into its own. CurveControl on our AmaSelect individual nozzle switching body, automatically switches nozzles based on the forward speed of each nozzle body, meaning as you travel around a corner, the inside of the boom will intelligently detect its reduced forward speed and switch to a smaller nozzle whereas the outside of the boom will switch to a larger nozzle or even two nozzles together to maintain an accurate dose rate across the entire width of the boom.

This system differs from PWM as the AmaSelect system has the best of both worlds, as the dosage range is dependent on your choice of 4 nozzles not just the single one of PWM. This means that you get great turn compensation as well as a massive dosage rate range in a straight line for example from 0.7 to 4.8 l/min whereas PWM on an 04 nozzle can only do 0.4 to 2.26 l/min, as seen below. Unlike PWM, AmaSelect allows for the use of air inclusion nozzles allowing you to reduce drift by around 75% (Agrovista). The benefits of curve compensation don’t stop with resistance build up though, it also helps reduce overdoses on the inside of the curve which can typically lead to yield losses due to phytotoxicity as well as reduce the danger of under-fertilisation during nutrient application on the outside of the curve. Another key benefit of AmaSelect is longevity, with some PWM systems suffering only short service life and incredibly intense, regular service intervals.

Mechanical weeding

When it comes to mechanical weeding, with the acquisition of Schmotzer, Amazone inherited over 100 years of knowledge in the inter-row hoeing industry. Schmotzer were the inventors of the hoe in 1922, and the long-lasting experience really shows within the Venterra range. With vast amounts of customisation to ensure we have the right hoe for everyone. In working widths from 1 to 12 metres and an ability to work accurately with our hydraulic shift frames down to a 16.6 cm row spacing, typical of that found on our Cayena and Cirrus drills. This opens the door for inter-row cultivations on cereals as well as the typical beet and maize crops. But let’s not get ahead of ourselves, the inter-row cultivator will never completely replace the sprayer, but it’s about utilising both systems as and when you can. Mechanical weeding has several other advantages, such as, breaking up a surface crust when capping has occurred, facilitating increased water infiltration. Inter-row cultivating is also a great opportunity to place fertiliser directly where the plant needs it, reducing fertiliser requirement by up to 25% as well as reducing inadvertent weed fertilisation.

Mechanical weeding doesn’t just have to be inter-row though. Stale seed beds are still a great way to encourage weed germination which can be quickly uprooted with a pass of a shallow depth cultivator such as the Amazone Cobra. The Amazone Cobra is available in working widths of 6 and 7 metres with a tine spacing of only 13.3 cm. This can work at a minimum of 4 cm depth, ideal for complete surface soil movement to eradicate weeds just before drilling without impacting deeper soil structure. It also doubles up a primary or secondary cultivator by changing from the 220 mm duckfoot to a 50 mm narrow share and with the optional knife roller fitted to the front of the Cobra, it can also be used to clear fields with cover crops of substantial height.

Cover crops

We all know the benefits cover crops can have on soil health and increasing the level of organic matter, but they can also have massive benefits when it comes to reducing the need for herbicides and pesticides. Many cover crops can be used effectively to smother and outcompete weeds for water and nutrients but can also be used to manage pests by hosting beneficial microbial life that discourages disease as well as encouraging beneficial insect predators to reduce insect damage. Studies by Koch, D using a rotation of barley > radish cover crop > sugar beet have been shown to successfully reduce sugar beet cyst nematodes, increasing beet yields in Wyoming, profitably substituting for chemical nematicides. SARE do push the fact that for many of these beneficials to work effectively the cover crop must not be fully incorporated as its presence protects beneficials and their habitat.

Farmers such as Bruce Christie have been using an Amazone GreenDrill to establish their cover crops. The Amazone GreenDrill catch crop seeder box is available as a 200 or 500 litre variant. In Bruce’s case his GreenDrill is mounted to his Cirrus cultivation disc drill, but the GreenDrill is available for mounting to a wide range of Amazone equipment such as the Catros discs and Ceus, Cobra and Cenius cultivators as well as to your own none Amazone machines. Bruce stated “The GreenDrill has revolutionised what we've been able to do in terms of green cover as well. We let out land here for growing potatoes and carrots as well and, in particular with the carrots, they want the headlands to be sown with wildflowers and nectar bearing plants. So, we've used the GreenDrill for that. We've also used it for sowing green cover after carrots to help break down the straw and that returns a bit of nitrogen ahead of wheat drilling”.

Once you’ve grown your cover crops you then need to find a way to desiccate and drill into those vast quantities of green manure. Topping is an effective way to shred cover crops but is often slow and cost ineffective, this is where Amazone TopCut comes to the rescue. The TopCut tool carrier consists of three subsequent tool segments, combining up to three knife rollers and/or slitting discs. At 12 metres wide with a low pulling requirement it can effectively prepare fields for direct drilling with just one pass.