Once the corn is in the ground, it’s time to start thinking about weed control ,says Jim Ruhland, a DuPont-Pioneer agronomist from Mitchell, S.D.. The sooner weeds are managed, he says, the better because:
* Early control helps protect crop yield potential.
* Small weeds are easier to control.
* Young weeds absorb and translocate herbicides better.
* Herbicides can be less effective during times of heat and drought stress, which often occur at later application times.
Sequential weed-control programs, including preplant treatments followed by postemergence herbicides, have consistently provided the best weed control and greatest net returns, Ruhland says.
Weeds can reduce corn yield as soon as the V2 stage. Control weeds earlier than this and maintain control through at least V14 to help ensure maximum yield potential. For soybeans, control weeds within the first four weeks and continue to maintain control through canopy closure.
If pre-plant herbicides were not applied, Ruhland says to follow these steps:
* Apply post-emergence herbicides as soon as possible.
* Include residual herbicides to extend control of weeds that are still germinating.
* Use the recommended rate for the weed size.
* Use high-quality adjuvants as directed on the product labels.
* Be prepared to apply follow-up treatments to control escaped and late-germinating weeds.
What to look for
An emerging stand will give you plenty of clues to potential performance and management concerns, according to Ruhland.
Uneven growth can start as early as germination, causing uneven emergence. Uneven emergence is typically associated with issues in the seed furrow, such as uneven planting depth, residue, fertilizer burn, cloddy seedbeds, soil crusting, etc.
Sometimes corn appears to emerge uniformly but then becomes uneven as it progresses through the V3 to V10 growth stages. In these cases, one usually needs to look beyond the seed furrow to understand the cause of the uneven growth. The main cause may lie in field activities that occurred months earlier and, therefore, may be more difficult to identify, Ruhland says..
Possible causes of the uneven growth include:
* Soil type and/or drainage
* Crop-residue uniformity
* Plant-nutrient deficiencies
* Pest damage
By planting with care, controlling weeds and keeping a vigilant eye out for trouble, growers can greatly improve their chances for a healthy stand that starts strong and offers the maximum potential for a strong finish., Ruhland says.