What are Weeds?
Undesirable plants are termed weeds. They usually germinate, grow and multiply fast, have deep root systems, are resistant to most diseases and pests and can grow vigorously under a wide range of conditions.
Weeds crowd plants and compete for nutrients, sunlight, water and space.
Besides serving as hosts to plant pests and diseases, weeds can significantly reduce corn yields if left unmanaged.
Classification of Weeds
Grasses.
This group is composed of species belonging to the same family as corn, Graminae or Poaceae, which, in vegetative form, ranges from small tufted to erect or creeping annuals or perennials.
The stem of grasses are called culms, which have well-defined swelling or nodes at regular intervals from which leaves arise. The leaves consist of two portions: an upper portion called leaf blade and a lower one called leaf sheath. At the junction of a lead blade and a leaf sheath are hairy outgrowths called ligules.
An example is itch-grass or aguingay (Rottboellia chochinchinensis).
Sedges.
This group bears a general resemblance to grasses but this species belongs to the family Cyperaceae. Their triangular stem, absence of ligule and fusion of leaf sheaths to form a tube around their stem can normally identify them.
The leaves usually run linear and all borne in a rosette arrangement on a stem-like structure. The portion under ground is a tuberous or elongated rhizome, commonly called bulb.
Nutsedge or mutha (Cyperus rotundus) represents this group.
Broad-leaves.
Species not falling under the description of grasses or sedges are roughly classified as broad-leaf weeds. These are those with more expanded leaf blades and those with two or more blades in a petiole.
An example of a broad-leaf weed is kamo-kamotihan (Ipomoea triloba).
How to Manage and Control Weeds
Optimum yields can be obtained by keeping corn fields weed-free at the first 40 days after planting. Weeds can be effectively managed and controlled by a combination of two or more practices.
Common methods of managing and controlling weeds:
- Thorough land preparation
- Inter-row cultivation. Off-bar 22-25 days after planting and hill-up 27-30 days after planting.
- Hand or spot weeding
Cover crops provide improved weed control in corn field
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