Weed management in coffee orchards

Weeds compete with coffee for water and nutrients, but killing them will cause soil erosion and loss of moisture. Instructions for three-tiered grass management — killing evil weeds, keeping supporting grass, mulching — for Robusta orchards in the Central Highlands.

Summary: Coffee growers in the Central Highlands have two schools of thought when it comes to weeds: kill them for easy care or keep them to protect the soil. Both have limits. A better way is to classify the grass and treat it differently: "evil" grass that competes with coffee for water is killed, "auxiliary" grass that holds soil and covers is kept. This article guides how to distinguish and apply seasons.

Applies to: Robusta coffee orchards in Dak Lak, Lam Dong, Gia Lai, Dak Nong, Kon Tum.
Duration: Management all year round, focusing on the rainy season and the end of the rainy season.
Difficulty level: Basic. It's important to change the way you think about grass.
Estimated additional costs: 3-5 million VND per hectare per year — 30-40 percent lower than traditional herbicide methods.

Why shouldn't we kill all the grass

Cleanly killing weeds in coffee orchards seems "tidy" but creates three big problems:

Soil erosion rainy season. In the Central Highlands, with heavy rains, red basalt soil without grass cover is washed away 2-5 centimeters of ground each year — loss of organic-rich soil.
The land dries quickly in the dry season. Grass keeps the soil moist, without grass it evaporates quickly, plants need more water.
Loss of natural enemies. Grass is home to ladybugs and wolf spiders — opponents of mealybugs and coffee pests.

On the other hand, evil weeds such as thatch grass, bear grass, and thread grass need to be killed because they compete strongly with coffee for water and nutrients. Balancing between the two is technical.

Classifying grass in coffee orchards

Evil grass needs to be destroyed

**Imperata cylindrica*: deep underground roots, strong resistance to water. Difficult to destroy because the roots crawl 1-2 meters underground.
Bear grass (*Cyperus rotundus*): underground tubers reproduce, the more you dig, the more you get.
**Cynodon dactylon*: crawls close to the soil, spreads quickly, difficult to uproot.
Betel nut grass, Fragranthus grass: 1-2 meters high, covers the light of young coffee trees.

General characteristics: strong underground roots, fast reproduction, not extinguished by shade.

Auxiliary grass should be kept

Narrow-leaved sedge grass: shallow roots, holds soil well, does not compete much for nutrients.
Wild peanut grass (*Arachis pintoi*): legume, fixes nitrogen to the soil, good cover.
Clover small type: shallow roots, flowers attract beneficial insects.
Ground grass is dense but low under 30 centimeters.

General characteristics: shallow roots, no strong competition for nutrients, easy to control height by cutting.

Three-tier management

Layer around the coffee tree (radius 60-80 centimeters)

This is the main active root zone. It is necessary to clean the grass so that the coffee does not compete for water and nutrients.

How to do:

Hand hoe clean the grass around the base 2-3 times a year. The beginning of the rainy season, the middle of the season, the end of the season.
Or use a selective herbicide — *Paraquat* (bipyridyl drug) or *Glufosinate ammonium* (phosphinothricin group drug) sprayed locally around the base. Avoid spraying on the coffee body.
After killing weeds, cover with dry grass or rotten coffee husks. Mulch 5-8 centimeters thick reduces grass regrowth and retains moisture.

Absolutely avoid: use *Glyphosate* (glycine group drug) on the area around the root. Can seep into coffee roots, causing toxicity.

Middle row (between two rows of coffee)

This area can be managed more lightly — keep grass low to protect the soil.

How to do:

Mow the lawn 3-4 times a year with a lawn mower. Keep the grass height 10-20 centimeters.
Leave grass clippings on site as green manure, do not collect them.
If the orchard has wild peanuts, hairy beans... encourage growth by not hoeing.
Kill evil weeds separately with hand hoe or selective crop-protection product.

orchard edge and walkway

This area can keep grass more naturally:

Mowing twice a year is enough.
Encourage grass with small flowers that attract beneficial insects.
Plant more small shrubs as a biological fence to prevent erosion.

Seasonal grass management

The beginning of the rainy season in April-May

Hoe all the grass around the base before heavy rain — wet soil makes it easier to hoe.
Mow grass between rows for easy fertilization.
Cover the base with compost material.

The peak of the rainy season is June-September

Grass grows the fastest. Watch the evil grass grow.
Hoe again around the base if the grass comes back.
Avoid spraying herbicides on wet soil — the crop-protection product will be diluted and less effective.

End of the rainy season October-November

Mow the grass between rows for the last time in the rainy season. The remaining grass clippings decompose into compost.
Preparing for harvest — clean paths for machines to collect and transport.

Dry season December-March

Grass grows less. Light management.
Keep the base mulch — protect the soil from the sun and retain moisture.

How to kill three special types of evil grass

Grass

Thatch grass has deep underground roots that cannot be dug up completely. How to destroy:

Cut close to the ground repeat every 2-3 weeks for 3-4 consecutive months. The underground roots run out of reserves, the grass gradually dies.
Or **spray *Glyphosate* on leaves** at the beginning of the rainy season when grass is growing strongly. The treatment moves down to the roots through the sap. Stay at least 1.5 meters away from coffee plants.

Bear grass

Gear grass reproduces through underground tubers. How to destroy:

Dig deeply for tubers in a small area in the new orchard.
Cut close to the ground repeatedly like thatch grass — the underground roots will dry out.
Large orchards can be sprayed selectively with monocotyledons — *Halosulfuron methyl* or *Sulfentrazone*.

Grass

The grass just crawls close to the ground and spreads quickly. How to destroy:

Hore thoroughly and pull the whole cow's body, leaving no small pieces behind.
After hoeing, cover immediately with decomposing material to prevent the grass from growing back.

Follow up every month

[ ] Proportion of evil weeds in the orchard — counted on 10 random square meter squares.
[ ] Grass height between rows.
[ ] Is the original coating still thick?
[ ] New grass appears that has not been seen before — be alert.

Common mistakes

**Spray *Glyphosate* close to the coffee roots**: the drug penetrates the roots, causing weak coffee, yellow leaves, and possibly killing young plants.

Remove weeds in large orchards: loss of cover, soil erosion, need more watering.

Removing auxiliary grass because it "doesn't look compact": waste of effort, loss of ecological benefits.

Do not treat thatch grass when it first appears: 1-2 years later it spreads throughout the orchard and is very difficult to kill.

Using the same treatment multiple times: weed resistance. Rotate drugs with different mechanisms.

Take notes

The main weed in the orchard (evil or auxiliary).
Number of hoeing and cutting times per year.
Medications taken — type, dose, date.
Cost of grass management per hectare.

References

*Weed management in coffee orchards* — Central Highlands Agricultural and Forestry Science and Technology Institute (abbreviated name WASI), 2022.
*Handbook for sustainable coffee land management* — Department of Crop Production, 2023.