Absolute mechanical weed control: FarmBiz – The Zimbabwe Independent
By Kudakwashe Gwabanayi
If one spends just five minutes in a farm chemical store these days, chances are two or three farmers have walked in and asked for herbicides or anything that can kill weeds.
Weeds have truly become a threat to this generation of farmers.
Wikipedia defines a weed as a plant considered undesirable in a particular situation, “a plant in the wrong place”.
Commonly cited examples are undesirable plants in human-controlled environments, such as agricultural fields, gardens, lawns and parks.
Similarly, volunteers (plants) are considered weeds in a subsequent crop.
This means that corn in a sugar bean field is a weed.
Due to the rainy season, where there are uncontrolled waterfalls in the fields, unwanted plants, especially annual grasses, grow where they are not wanted by the farmers.
While during the dry season, farmers can use drip irrigation systems that water only the desired crop to smother weeds, or mulch to cover areas where weeds would grow so they don’t get sunlight, these methods are inapplicable during the rainy season.
This therefore means that one can either remove the weeds using chemicals or do it mechanically, i.e. using a hoe or a cultivator.
Now, because we’re using more fertilizers – and of different types – the grass is quickly outgrowing the desired crop because fertilizers don’t select which plants to feed.
Lacking manual labor and, in most cases, poor planning, the farmer has no choice but to rush to get herbicides.
While there are many post-emergency chemicals that can treat weeds, the anxiety following purchase and subsequent use really isn’t worth it to the farmer.
Sometimes it rains heavily right after the herbicide is applied and it washes away and you may have to reapply it.
In other cases, it does not rain at all, but some herbicides require the grass or weeds to be relatively wet before applying them.
Also, the store clerk doesn’t really tell you about the side effects of weeds, or that after applying certain herbicides in corn for example, you can’t plant potatoes or tubers that grow underground.
Some corn herbicides are incompatible with other crops.
They will require you to plant only corn in that field for at least two years as the residual effects wear off.
Usually, farmers find out the hard way – after planting and realizing that germination is less than 30%, they realize that it was the side effects of herbicides that affected germination.
Although this may seem to discourage the use of herbicides, this in no way means that this author is against the new regime of chemicals available.
On the contrary, the use of pre-emergence herbicides is encouraged.
Again, this comes back to the issue of proper planning as mentioned earlier.
Most farmers who cultivate more than 600 hectares in the open field apply their herbicides 30 days or more before planting what they want to plant.
But those who do small portions like 5 ha are encouraged to do mechanical weeding.
It is absolute and definitive.
When we talk about mechanical weeding, we mean the use of hoes or ox-drawn cultivars to weed the weeds.
The cost is generally the same; hire labor and use post-emergence chemicals
It is enough to do it twice: four weeks after germination and at the eighth week.
In fact, even farmers with huge areas of cultivated land use tractor-drawn cultivators to get rid of weeds.
It’s the best way to do it.
Petruzzello (1984) describes a cultivator as an agricultural tool or machine designed to stir up the soil around a crop as it matures to promote growth and destroy weeds.
Horse-drawn cultivators were introduced in the mid-19th century.
In 1870, a farmer with two horses could cultivate up to 6 ha (15 acres) a day with a machine whose shovels (blades) straddled the rows of crops.
In the 20th century, with the power of tractors replacing horses, the number of rows a single machine could cultivate reached the capacity of multi-row planters.
As a result, cultivators and weeders have evolved over time and there are currently many types.
Spring tine weeders have lightweight spring tines that remove shallow rooted weeds without harming growing plants and can therefore be used directly on rows planted at an early stage, ridding the field of many weeds at as they emerge.
Rod weeders are used to control weeds in open, unplanted fields; their working element is a square section rod that rotates a few centimeters below the surface of the ground.
Tillers, essentially light plows, are equipped with spring tines, shovels or brooms.
It is in this context that farmers are reminded that as they go with the flow of the green revolution, it is important that they look at some ways that have been effective in dealing with their most common problems.
It can be argued that once it starts to rain it never gives you the option to weed manually and that is why most farmers prefer chemical weed control but at the first chance and opportunity go the traditional way. may give better results.
In some cases, farmers who use chemicals to weed their fields end up losing their own crops because they would have bought non-selective herbicides without knowing it because there are selective and non-selective herbicides.
Non-selective herbicides are generally more potent, but they usually kill any plants they come in contact with, including grass and other flowers the farmer may want to protect.
There are also contact and non-contact herbicides.
Indeed, traders do not have time to explain to farmers how to use chemicals.
In addition, farmers will buy the cheapest chemicals in the market without worrying too much about the side effects of chemicals.
Due to the huge demand for herbicides during the rainy season, stores quickly run out, opening a hole for criminals and unscrupulous dealers who then sell fake chemicals.
Some of the herbicides are actually diluted by the vendors so they get huge volumes.
There are also chemicals that are harmful to animals like chickens, goats, and cattle that are kept on the farm, so buying them would disrupt the ecosystem.
There are so many advantages such as time-saving of chemicals and their disadvantages as already stated above, but the bottom line is that mechanical weeding will give the farmer a better result than the use of chemicals, especially if the herbicide is a post-emergence herbicide.
By definition, post-emergence herbicides act on weeds that have already grown.
They use a mixture of chemicals to kill the weeds and make sure they don’t grow back.
There are several types of post-emergence herbicides available to help eradicate different types of weeds in various environments.
On the other hand, pre-emergence weedkillers are used before weeds are seen to prevent them from appearing.
This does not mean that the chemicals interfere with germination, but rather that they stop the formation of new root cells in young weed plants.
Without roots, the seedlings cannot continue to feed and grow and they simply die.
This whole process happens at ground level under the grass blades and thatch so you never have to see sprouting weeds.
The timing, weather conditions and type of weeds with which the grower is concerned will dictate the exact formula and application for pre-emergence use.
The chemicals in pre-emergence weedkillers are not effective on vegetative buds that grow from existing roots or rhizomes.
They also cannot be used on a prepared grass seedbed as their root stunting action in young plants will also affect grass germination.
What is clear about these herbicides is that they are scientific and require a certain level of intellect and knowledge to use at any given time.
- Gwabanayi is a practicing journalist and a farmer in his own right. — 0772 865 703 or [email protected]