By Professor Sheunesu Mpepereki

A FEW weeks ago, I penned two articles on growing soya beans.
I got feedback from several farmer that the information was useful.
We are preparing a book to provide information to farmers on soyabean production.
To make Zim-ASSET operational, we need to walk the talk.
This article will provide more insight on managing soyabean crops.
Travelling to Harare from Doma, through Raffingora, I observed many fields planted to soyabean on both A1 and A2 farms.
One small-holder farmer told me soyabean had better returns on a dollar invested compared to tobacco.
“Soya hadzina zvikaranga zvakawanda sefodya,” which is to say soya has fewer requirements than tobacco.
He had two hectares (ha) of soyabean that represented a textbook case of how not to grow soyabean.
Still he was enthusiastic and asked many useful questions!
I spent some time advising him and felt that I needed to talk to more farmers through this article.
Given my passion for soyabean, I was pleased to see that more farmers were now seeing the light and adopting soyabean as a major cash crop. Evidence on the ground though, shows that many farmers still lack information and technical advice on raising soyabean crops.
We have work to do!
I came across one farmer spraying a herbicide on his two ha soyabean crop.
On inquiry, he told me the herbicide was applying with a knapsack sprayer was called ‘Classic’ otherwise known by its chemical name chloro-muron-ethyl.
He explained that he wanted to control broad leaf weeds that threatened to turn his crop into what I jokingly call ‘sora beans’.
Indeed he was using the correct herbicide.
‘Classic’ is a selective herbicide for the control of broadleaf weeds in soyabeans.
I noticed that most of the grass type weeds in that field were already turning yellow with a few already dead.
The farmer told me he had, a week earlier, applied ‘Fusilade’ a selective herbicide that controls grasses.
Again I was impressed.
This farmer knew something about herbicides for use in soyabean production.
Sadly, many others still need a lot of help knowledge-wise.
In addition to the selective herbicide ‘Classic’, broad leaf weeds in soyabean can be controlled with another post-emergent herbicide called ‘Basagran’ while grasses are controlled with another called ‘Pursuit’.
Both ‘Basagran’ and ‘Pursuit’ are selective post-emergent herbicides for soyabean.
Readers will want to know that these are trade names given by different companies for the same chemical; we give their names here as examples of commonly available herbicides among many others.
Those farmers who planted soyabeans and immediately applied pre-emergent herbicides are unlikely to experience weed pressure in their soyabean stands.
These pre-emergent herbicides include metribuzin to prevent germination of broad leaf weeds and Metalochlor or Alachlor (Lasso) for grasses.
If the pre-emergent herbicides were incorrectly applied, weeds may germinate and compete with the soya crop for water, nutrients and light.
In such cases farmers are encouraged to apply post-emergent herbicides as described above.
For post-emergent herbicides to give effective weed control, they must be applied correctly.
Here are a few reminders on correct practices in applying herbicides.
Make sure to use the correct herbicide for the type of weeds in your field.
For pre-emergent herbicides applied to soil, the amount of clay in the soil is critical.
Less herbicide is required in sandy light-textured soils; heavier soils require a higher herbicide rate as some is always adsorbed by clay particles.
Some herbicides are not recommended for use on sandy soils. Information on application rates is found on the container label.
All users must read and understand the label on the herbicide container before applying.
Another danger is applying too little or too much.
If too little, weeds will appear soon after crop germination; if too much, the herbicide may burn the crop or prevent germination of crops coming next in the rotation.
Herbicides can remain in the soil (persist) for some months.
Also weeds exposed to low (sub-lethal) levels of herbicide may develop herbicide resistance.
If that happens, higher rates of application may need to be adopted, but that could damage the crop too!
Environmental pollution can follow.
Broad leaf weeds are easily controlled at three – five leaf stage.
l To be contnued